24th Aug 2010, 09:48
permalink Post: 88
Biggles78
The tailwheel design really was the one exception in poor design terms, but I'm sure that if the aircraft was doing what she should be doing right now, (you know routinely flying across the Atlantic and beyond, instead of languishing in museums), modifications would have finally put this particular malady to bed). In design terms, the rest of the aircraft was nothing short of a flying work of art, a masterpiece. Having said that though, personally I would rather that four rather than three hydraulic systems had been used. Originally there were four systems in the design, but the RED system was deleted, as it was felt to be superfluous. My own view is that this particular decision was total poppycock. Oh, and Green, Blue and Yellow hydraulic systems was something else that Airbus copied from Concorde.... although we ourselves pinched that idea off of the Comet
).
As far as the hydraulic expansion joints go, I will scour around and see if I can find a diagram for you. Try and picture two titanium (or stainless) tubes, on inside the other, with a sealed chamber being formed at the join. Inside this chamber were multiple lands fitted with special viton GLT seals. They did work incredibly well, although occasionally one of the seals gave out, and things got wet, VERY WET.
As far as the 4000 PSI hydraulic system, as EXWOK quite rightly pointed out, the loading on the flying control surfaces were immense throughout the whole flight envelope. (Picture alone just the T/O from JFK RWY 31L, where the aircraft is tightly turning and the gear retracting, all at the same time). As well as the flying controls and landing gear, you also had the droop nose to consider, four variable engine intakes as well as a couple of hydraulically operated fuel pumps. Oh, and in emergencies, a hydraulically driven 40 KVA generator too. The reason that 4000 PSI was chosen was that if a large amount of hydraulic 'work' was to be done, the only way to keep the size of jacks and actuators to a reasonable size/weight was to increase the system pressure by 25% from the normal 3000 PSI. (On the A380 they've gone a step further and gone for 5000 PSI, saving them over a tonne on the weight of the aircraft).
Concorde used a special hydraulic fluid, Chevron M2V. This is a mineral based fluid, as opposed to the ester based Skydrol, used by the subsonics. The reason that we went for a different fluid was a simple one; Skydrol is rubbish at the high temperatures that Concorde operated at, no good at all in fact, so we needed something better and in M2V we found the PERFECT fluid. As an aside, unlike Skydrol, that attacks paintwork, certain rubber seals, skin, EYES etc., M2V is completely harmless, wash your hair in it. (I did, several times when we had leaks. Thinking about it, maybe THAT is why my hair is such a diminished asset
EXWOK
It's so great having another of my pilot friends diving in to this post, welcome welcome
I remember the Mech' Signalling part of the air tests, my lunch has just finished coming back up thank you.
(for interest chaps and chapesses, with mechanical signalling, using just the conventional control runs under the floor, there was no auto-stabilisation).
The artificialfeel system worked incredibly well I thought, I always found it curious that the peak load law in the computer was at the transonic rather that the supersonic speed range. It was explained to me long ago that this was because the controls really are at their most sensitive here, but at high Mach numbers are partially 'stalled out', due to shockwave movements along the surfaces, and were therefore less effective. (For this reason I was told, the inner elevons were so critical for supersonic control, being the most effective of all elevons at high speed).
To all , I forgot to mention in my previous post regarding the engine failure in G-BOAF in 1980; I remember an FAA surveyor, who was taking a look at the carnage within the engine bay, saying that in his opinion, no other aircraft in the world could have survived the intensity of the titanium fire that ensued. Analysis showed that the fire was successfully extinguished, possibly at the first shot of the fire bottle. This was a testament to the way that the Concorde engine bay could be completely 'locked down' when the fire handle was pulled, as well as to the way that the whole engine installation was technically encased in armour plate. To put all this in context, acording to Rolls Royce a titanium fire, once it takes hold, can destroy the compressor of a jet engine in four seconds.
Dude
Quote:
|
M2
, it appears the tailwheel was, so far, the only "fault" in an otherwise extreme machine. Were there any other items like the tailwheel that were unworthy to be in her?
Does anyone have a tech drawing of the "sliding seals" used in the hydraulics. I have trouble visualising something that could withstand the 4,000psi pressure. Why was such a high pressure used? After all the control surfaces couldn't have required that much input to effect an authority movement. I understand it was also a special fluid that was used. Was this because of the pressure it was under or the temperature extremes? |
).
As far as the hydraulic expansion joints go, I will scour around and see if I can find a diagram for you. Try and picture two titanium (or stainless) tubes, on inside the other, with a sealed chamber being formed at the join. Inside this chamber were multiple lands fitted with special viton GLT seals. They did work incredibly well, although occasionally one of the seals gave out, and things got wet, VERY WET.
As far as the 4000 PSI hydraulic system, as EXWOK quite rightly pointed out, the loading on the flying control surfaces were immense throughout the whole flight envelope. (Picture alone just the T/O from JFK RWY 31L, where the aircraft is tightly turning and the gear retracting, all at the same time). As well as the flying controls and landing gear, you also had the droop nose to consider, four variable engine intakes as well as a couple of hydraulically operated fuel pumps. Oh, and in emergencies, a hydraulically driven 40 KVA generator too. The reason that 4000 PSI was chosen was that if a large amount of hydraulic 'work' was to be done, the only way to keep the size of jacks and actuators to a reasonable size/weight was to increase the system pressure by 25% from the normal 3000 PSI. (On the A380 they've gone a step further and gone for 5000 PSI, saving them over a tonne on the weight of the aircraft).
Concorde used a special hydraulic fluid, Chevron M2V. This is a mineral based fluid, as opposed to the ester based Skydrol, used by the subsonics. The reason that we went for a different fluid was a simple one; Skydrol is rubbish at the high temperatures that Concorde operated at, no good at all in fact, so we needed something better and in M2V we found the PERFECT fluid. As an aside, unlike Skydrol, that attacks paintwork, certain rubber seals, skin, EYES etc., M2V is completely harmless, wash your hair in it. (I did, several times when we had leaks. Thinking about it, maybe THAT is why my hair is such a diminished asset
EXWOK
It's so great having another of my pilot friends diving in to this post, welcome welcome
I remember the Mech' Signalling part of the air tests, my lunch has just finished coming back up thank you.
(for interest chaps and chapesses, with mechanical signalling, using just the conventional control runs under the floor, there was no auto-stabilisation).
The artificialfeel system worked incredibly well I thought, I always found it curious that the peak load law in the computer was at the transonic rather that the supersonic speed range. It was explained to me long ago that this was because the controls really are at their most sensitive here, but at high Mach numbers are partially 'stalled out', due to shockwave movements along the surfaces, and were therefore less effective. (For this reason I was told, the inner elevons were so critical for supersonic control, being the most effective of all elevons at high speed).
To all , I forgot to mention in my previous post regarding the engine failure in G-BOAF in 1980; I remember an FAA surveyor, who was taking a look at the carnage within the engine bay, saying that in his opinion, no other aircraft in the world could have survived the intensity of the titanium fire that ensued. Analysis showed that the fire was successfully extinguished, possibly at the first shot of the fire bottle. This was a testament to the way that the Concorde engine bay could be completely 'locked down' when the fire handle was pulled, as well as to the way that the whole engine installation was technically encased in armour plate. To put all this in context, acording to Rolls Royce a titanium fire, once it takes hold, can destroy the compressor of a jet engine in four seconds.
Dude
26th Aug 2010, 16:43
permalink Post: 132
Quote:
|
Originally Posted by
Brit312
Surges were not an uncommon or common event on Concorde, but when they happened - as they usually affected both engines on that side - the aircraft would lurch /yaw and everybody on board would know about it...
|
So the prototypes were equipped with "autorudder" computers. They used pressure sensors in the engines to detect engine failures, and they would then kick in a "pre-dosed" amount of rudder, that would then be "washed-out" gradually while the pilot dealt with the issue and added rudder trim.
They were manufactured by SFENA, and since I was their flight test support at Fairford, they became automatically my "babies".
The computers (analog, big boxes, the same size as the autopilots or air intake computers) were extremely reliable (we had only two passive faults during the entire flying career of 002).
Unfortunately the same could not be said of the pressure sensors, and since it was always easier to "pull" a computer than a pressure sensor, we found a computer on the bench every few weeks, which then had to be taken through a full test spec and sent back with "no fault found", before anybody was willing to look at the sensors.
Luckily a better solution was found, using a lateral accelerometer, and from the preprod aircraft onwards, each big separate autorudder computer was replaced by a single board tucked away in the autostab computer.
Since the function was always "on", there was no separate autorudder engage switch. Many years later, I discovered that several airline Concorde pilots did not even know the function existed....
CJ
27th Aug 2010, 04:59
permalink Post: 133
Nick Thomas
[QUOTE]Going back to expansion and paint. With the aircraft expanding approx 6 inches and a temp change up to 127`c, I guess a special kind of paint; able to withstand such adverse conditions; must have been used? When deciding on the paint specification was any consideration given to the overall weight of the paint?[/QUOTE
Can't remember much about paint spec's, but a lot of experimentation/trial and error was carried out with different paints until the right one was found. I remember when G-BOAD was delivered, that copiuous sheets of paint had peeled off in flight. Finally a superb polyurithane paint was found that did the trick perfectly.
Yes Nick, the life of the airframe was limited by the number of supersonic cycles, however modifications carried out extended the life of the airframe significantly. (and more were planned).
And the 'hat in the gap' stories are quite true.
ChristiaanJ
This was the real beauty of the autostab' on all 3 axis; you could just safely take it all for granted. The Mach 2 engine out case was a classic, as not only would the aircraft yaw towards the dead engine but there was an adverse roll input, where the wing on the same side would LIFT due to the excess intake air for the failed automatically being 'dumped' through the now open spill door. If for any reason the aircraft HAD been under manual rather than autopilot control, then life without autostab would be rather uncomfortable to say the least. And putting further Concorde's achievements in terms of stability; the world's only previous large delta winged Mach 2 aircraft, the B58 Hustler, had the slightly awkward feature in the case of an outer engine failure at Mach 2, in that the yaw forces were sufficient to tear the fin off. This happened on more than one occasion during service life of the Hustler, but engine failure (or far more likely a deliberate precautionary shut-down) although hardly a non-event in the case of Concorde, it was routinely dealt with without drama or danger.
Dude
[QUOTE]Going back to expansion and paint. With the aircraft expanding approx 6 inches and a temp change up to 127`c, I guess a special kind of paint; able to withstand such adverse conditions; must have been used? When deciding on the paint specification was any consideration given to the overall weight of the paint?[/QUOTE
Can't remember much about paint spec's, but a lot of experimentation/trial and error was carried out with different paints until the right one was found. I remember when G-BOAD was delivered, that copiuous sheets of paint had peeled off in flight. Finally a superb polyurithane paint was found that did the trick perfectly.
Quote:
| Did the repeated expansion and contraction cycle have a detremental effect on the ulitamate life of the airframe? |
And the 'hat in the gap' stories are quite true.
ChristiaanJ
Quote:
| Many years later, I discovered that several airline Concorde pilots did not even know the function existed.... |
This was the real beauty of the autostab' on all 3 axis; you could just safely take it all for granted. The Mach 2 engine out case was a classic, as not only would the aircraft yaw towards the dead engine but there was an adverse roll input, where the wing on the same side would LIFT due to the excess intake air for the failed automatically being 'dumped' through the now open spill door. If for any reason the aircraft HAD been under manual rather than autopilot control, then life without autostab would be rather uncomfortable to say the least. And putting further Concorde's achievements in terms of stability; the world's only previous large delta winged Mach 2 aircraft, the B58 Hustler, had the slightly awkward feature in the case of an outer engine failure at Mach 2, in that the yaw forces were sufficient to tear the fin off. This happened on more than one occasion during service life of the Hustler, but engine failure (or far more likely a deliberate precautionary shut-down) although hardly a non-event in the case of Concorde, it was routinely dealt with without drama or danger.
Dude
7th Sep 2010, 09:59
permalink Post: 253
Makes me wonder... In the event of a complete loss of thrust at Mach 2 (say fuel contamination) would the deceleration be significant ? If so I guess the fuel redistribution / pumping to maintain acceptable CG would become interesting...
Concorde did actually have a four engine failure drill, which covered it's complete speed rsnge including Mach 2.0. There was one assumption made in this drill and that the engines would continue to windmill which would allow them to give you full hydraulic pressure
As you could imagine, If all 4 engines cut at Mach 2.0 the F/E would be quite busy and so the the non flying pilot would use his fuel transfer switch to start the fuel moving forward. This was a pretty basic selection where fuel would be pumped out of Tank 11 using all 4 pumps [2 electrical and 2 hydraulic driven] and into the very forward tank which was no 9.
As a rule of thumb transferring 1000kgs from tank 11 to tank 9 moved the Cof G forward by 1%. Now with all 4 pumps in tank 11 running the tansfer forward was so quick that the pilot had to keep switching the transfer off and then on to stop the Cof G moving forward too quickly. It was usually to everybody's relief when the F/E could find the time to take over the fuel transfer as he had the selections to allow him to be more selective as to where the fuel went and so slow the rate down
---------------------------------------
This was quite a neat system, as the gear was retracted, a SHORTENING LOCK valve was signalled, allowing a relatively tiny jack to pull the entire shock absorber body into the body of the oleo progressively as the gear retracted. So the shock
Forther to M2dude's explanation Concorde's main landing gear consisted of 3 seperate metal castings . there was the normal two for the oleo and these two were fitted inside the outer casting, which was the one you could see.
As the gear retracted a mechanical linkage , which was driven by the gear's retraction movement, would lift the oleo assembly up into the outer casing, so shortening the length of the leg . If I remember the shortening jack was just to assist in breking the geometric lock of the linkage
------------------------------------------
The other difference between AF and BA aircraft was the DC electrical system
AF had Nickel cadmium batteries with an automatic charging system
BA had the good old lead acid battery sysytem, well except for AG where the DC system was one of the systems they never changed when AG was incorporated into the BA fleet
Concorde did actually have a four engine failure drill, which covered it's complete speed rsnge including Mach 2.0. There was one assumption made in this drill and that the engines would continue to windmill which would allow them to give you full hydraulic pressure
As you could imagine, If all 4 engines cut at Mach 2.0 the F/E would be quite busy and so the the non flying pilot would use his fuel transfer switch to start the fuel moving forward. This was a pretty basic selection where fuel would be pumped out of Tank 11 using all 4 pumps [2 electrical and 2 hydraulic driven] and into the very forward tank which was no 9.
As a rule of thumb transferring 1000kgs from tank 11 to tank 9 moved the Cof G forward by 1%. Now with all 4 pumps in tank 11 running the tansfer forward was so quick that the pilot had to keep switching the transfer off and then on to stop the Cof G moving forward too quickly. It was usually to everybody's relief when the F/E could find the time to take over the fuel transfer as he had the selections to allow him to be more selective as to where the fuel went and so slow the rate down
---------------------------------------
This was quite a neat system, as the gear was retracted, a SHORTENING LOCK valve was signalled, allowing a relatively tiny jack to pull the entire shock absorber body into the body of the oleo progressively as the gear retracted. So the shock
Forther to M2dude's explanation Concorde's main landing gear consisted of 3 seperate metal castings . there was the normal two for the oleo and these two were fitted inside the outer casting, which was the one you could see.
As the gear retracted a mechanical linkage , which was driven by the gear's retraction movement, would lift the oleo assembly up into the outer casing, so shortening the length of the leg . If I remember the shortening jack was just to assist in breking the geometric lock of the linkage
------------------------------------------
The other difference between AF and BA aircraft was the DC electrical system
AF had Nickel cadmium batteries with an automatic charging system
BA had the good old lead acid battery sysytem, well except for AG where the DC system was one of the systems they never changed when AG was incorporated into the BA fleet
6th Oct 2010, 23:40
permalink Post: 519
The AF simulator was regarded as a sub standard machine, never had the required interface or processing power compared the the UK machine that was built as a joint effort by Sinker-Link Miles (structure and motion) and Redifon simulation (interface and computers), with a view that the developed product would be offered to the option holding airlines.
A key failing of the AF machine was that it could not correctly simulate an engine failure on take off without going off the runway.
So what happened when AF had an apparent engine failure/fire after V1 in 2000? The crew made a right hash of the procedures....Nuff said really.
A key failing of the AF machine was that it could not correctly simulate an engine failure on take off without going off the runway.
So what happened when AF had an apparent engine failure/fire after V1 in 2000? The crew made a right hash of the procedures....Nuff said really.
31st Oct 2010, 16:31
permalink Post: 646
M2Dude & Brit312:
FWIW the LP Cock to shutoff was added to the precautionary engine shutdown C/L - but I think this was after (and because of) the AF inceident.
But I had understood that their engine failure that day had been due to a problem with the engine which caused enough vibration to damage the fuel pipe leading to the leak. I don't know if they ran the Fire / Severe Damage C/L, but that C/L always involved shutting the LP Cock as part of the Cleanup Items. Maybe they did "only" run the Precautionary Shutdown C/L - I have no idea, but the LP Cock position (which turned out to be key to the near loss of the a/c) would depend on it prior to the addition of that step in that latter drill.
I do remember there was always controversy in training circles about the Cleanup Items and when or where (or even "IF"?) they should be run: but IF the AF flight had run the Fire / Severe Damage drill and IF they had run the Cleanup Items soon afterwards, then their situation would not have been so dire.
No critisism of anyone intended (AF crew or forum posters), it's all such a long time ago now, but the nuances involved in Precautionary Shutdown / Fire - Severe Damage / Cleanup Drills were far from clear-cut...
FWIW the LP Cock to shutoff was added to the precautionary engine shutdown C/L - but I think this was after (and because of) the AF inceident.
But I had understood that their engine failure that day had been due to a problem with the engine which caused enough vibration to damage the fuel pipe leading to the leak. I don't know if they ran the Fire / Severe Damage C/L, but that C/L always involved shutting the LP Cock as part of the Cleanup Items. Maybe they did "only" run the Precautionary Shutdown C/L - I have no idea, but the LP Cock position (which turned out to be key to the near loss of the a/c) would depend on it prior to the addition of that step in that latter drill.
I do remember there was always controversy in training circles about the Cleanup Items and when or where (or even "IF"?) they should be run: but IF the AF flight had run the Fire / Severe Damage drill and IF they had run the Cleanup Items soon afterwards, then their situation would not have been so dire.
No critisism of anyone intended (AF crew or forum posters), it's all such a long time ago now, but the nuances involved in Precautionary Shutdown / Fire - Severe Damage / Cleanup Drills were far from clear-cut...
8th Nov 2010, 21:15
permalink Post: 684
coobg002
,
I'm not an aircraft designer, just an avionics engineer with an aeronautical engineering background, so my answer can only be partial...
Pity you cannot ask the question directly to "Clarence" Johnson, because he used both solutions for two of his best-known Mach 2+ designs...
The F-104 had indeed a very small, very thin, straight wing.
The SR-71 had a wing shape not totally unlike Concorde; admittedly the wing shape itself was more a delta, but the 'chines' of the forward part of the fuselage played an important role.
I would say.... every design is a compromise.
You don't start with a good-looking shape, you start with a specification.
In the case of the F-104 it was for an interceptor, something simple and fast , with a (relatively) limited range.
So you chose a big engine, you stuck a cockpit at the front, and you added the smallest straight wings that would do the job.
Not exactly ideal at low speed... the F-104 had huge "blown" flaps and even so it was still pretty "hot" during approach and landing.
As to what to do after an engine failure.... the procedure for a dead-stick landing was in the manual, but generally the "she flies like an angel, but she glides like a brick" would prevail, and you'd punch out.
In the case of the SR-71, much like Concorde, it was the 'spec' that was totally different.
Long-range supersonic cruise (hence space for fuel in the wing was prized), but also acceptable low-speed handling.
Think of the repeated air-to-air refuelling for the Blackbird, or the subsonic sectors in a typical LHR-JFK flight for Concorde.
So for anything that can still take off and land at an acceptable speed and perform well subsonically when needed, yet cruise at Mach 2 or Mach 3, the ogee/delta wing has turned out to be the best compromise.
CJ
I'm not an aircraft designer, just an avionics engineer with an aeronautical engineering background, so my answer can only be partial...
Pity you cannot ask the question directly to "Clarence" Johnson, because he used both solutions for two of his best-known Mach 2+ designs...
The F-104 had indeed a very small, very thin, straight wing.
The SR-71 had a wing shape not totally unlike Concorde; admittedly the wing shape itself was more a delta, but the 'chines' of the forward part of the fuselage played an important role.
I would say.... every design is a compromise.
You don't start with a good-looking shape, you start with a specification.
In the case of the F-104 it was for an interceptor, something simple and fast , with a (relatively) limited range.
So you chose a big engine, you stuck a cockpit at the front, and you added the smallest straight wings that would do the job.
Not exactly ideal at low speed... the F-104 had huge "blown" flaps and even so it was still pretty "hot" during approach and landing.
As to what to do after an engine failure.... the procedure for a dead-stick landing was in the manual, but generally the "she flies like an angel, but she glides like a brick" would prevail, and you'd punch out.
In the case of the SR-71, much like Concorde, it was the 'spec' that was totally different.
Long-range supersonic cruise (hence space for fuel in the wing was prized), but also acceptable low-speed handling.
Think of the repeated air-to-air refuelling for the Blackbird, or the subsonic sectors in a typical LHR-JFK flight for Concorde.
So for anything that can still take off and land at an acceptable speed and perform well subsonically when needed, yet cruise at Mach 2 or Mach 3, the ogee/delta wing has turned out to be the best compromise.
CJ
21st Nov 2010, 18:21
permalink Post: 753
QUOTE]I'm wonder if all 4 Olympus 593 all died in flight and unable to restart. Is it
possible to be able to land at the nearest airport[/QUOTE]
As CristiaanJ says , it depends on how far the nearest airfield was away, but given that there was one close enough then yes in theory it was possible.
On Concorde there were two checklist to cater for a four engine failure that assumes the engine have flamed out but not seized thus the system can be fed by windmilling engines. The two drills are
4 ENGINE FAILURE ABOVE MACH 1.2
4 ENGINE FAILURE BELOW MACH 1.2
When above M1.2 the windmilling speed of the engines should keep the engine generators on line and you should have good hyd pressure also.
Therefore the main point of the drill at this speed is to try and relight the engines, by selecting relight on all 4 engines at the same time. You normally got the chance to go through 2 and some times 3 relight sequences before the speed dropped to Mach 1.2
At mach 1.2 with no engines then the windmilling speed is reaching a point where it is not sufficent to hold the generators on line so the drill concentrates on switching as much of the systems onto essential electrics which will be supplied by the hydraulically driven emergency generator.
To help support the yellow and green hyd system below M1.2 the ram air turbine is lowered. Engine relights will continue to be attempted but as you are on essential electrics now they can only be attempted individually.
If no relights and below 10,000ft then the c/list tells you to prepare the aircraft for landing by lowering nose/visor and gear by emergency systems with speed reduced now to 270 kts. To conserve hyd pressure being mainly derived now from the RAT for the flying controls the emerg gen is switched off during the approach and approch speed is 250 kts with min landing speed
of 200kts
During this all this descent the aircraft had to be flown and navigated, radio calls made along with PA and cabin briefing and all the normall descent checklist complied with so you can imagine it was quite a busy time
This drill used to be practised on the sim ,but the crew would normally find the engines started to relight before 10,000ft so as to give the crew confidence that the drill worked.
However after many years of operation there was some talk about doing away eith the drill as no one could envisage it ever happening. then the BA 747 lost all 4 engines in the volcanic ash cloud and all such talk stopped
possible to be able to land at the nearest airport[/QUOTE]
As CristiaanJ says , it depends on how far the nearest airfield was away, but given that there was one close enough then yes in theory it was possible.
On Concorde there were two checklist to cater for a four engine failure that assumes the engine have flamed out but not seized thus the system can be fed by windmilling engines. The two drills are
4 ENGINE FAILURE ABOVE MACH 1.2
4 ENGINE FAILURE BELOW MACH 1.2
When above M1.2 the windmilling speed of the engines should keep the engine generators on line and you should have good hyd pressure also.
Therefore the main point of the drill at this speed is to try and relight the engines, by selecting relight on all 4 engines at the same time. You normally got the chance to go through 2 and some times 3 relight sequences before the speed dropped to Mach 1.2
At mach 1.2 with no engines then the windmilling speed is reaching a point where it is not sufficent to hold the generators on line so the drill concentrates on switching as much of the systems onto essential electrics which will be supplied by the hydraulically driven emergency generator.
To help support the yellow and green hyd system below M1.2 the ram air turbine is lowered. Engine relights will continue to be attempted but as you are on essential electrics now they can only be attempted individually.
If no relights and below 10,000ft then the c/list tells you to prepare the aircraft for landing by lowering nose/visor and gear by emergency systems with speed reduced now to 270 kts. To conserve hyd pressure being mainly derived now from the RAT for the flying controls the emerg gen is switched off during the approach and approch speed is 250 kts with min landing speed
of 200kts
During this all this descent the aircraft had to be flown and navigated, radio calls made along with PA and cabin briefing and all the normall descent checklist complied with so you can imagine it was quite a busy time
This drill used to be practised on the sim ,but the crew would normally find the engines started to relight before 10,000ft so as to give the crew confidence that the drill worked.
However after many years of operation there was some talk about doing away eith the drill as no one could envisage it ever happening. then the BA 747 lost all 4 engines in the volcanic ash cloud and all such talk stopped
11th Dec 2010, 20:04
permalink Post: 854
A certain CFI (I think) at BA flying club, High Wycombe, who was also F/O on concorde, showed me some photographs of an engine that had eaten a piece of intake ramp.
I think he said that the adjacent engine had surged and a piece of ramp went out the front and down the other engine. This resulted in a double engine failure mid atlantic. They landed in Shannon with very little fuel left.
A double engine change ensued.
Question, how fast was the ramp going if the A/C was at Mach 2?
I think he said that the adjacent engine had surged and a piece of ramp went out the front and down the other engine. This resulted in a double engine failure mid atlantic. They landed in Shannon with very little fuel left.
A double engine change ensued.
Question, how fast was the ramp going if the A/C was at Mach 2?
11th Dec 2010, 20:59
permalink Post: 855
Quote:
|
Originally Posted by
dixi188
A certain CFI (I think) at BA flying club, High Wycombe, who was also F/O on concorde, showed me some photographs of an engine that had eaten a piece of intake ramp.
I think he said that the adjacent engine had surged and a piece of ramp went out the front and down the other engine. This resulted in a double engine failure mid atlantic. They landed in Shannon with very little fuel left. |
First time that happened was on prototype 001 in the very early days, when an engine "spit out" the entire ramp (there's a photo in Trubshaw's book).
The ramps and actuators were 'beefed up' considerably afterwards... I didn't know an in-service aircraft had suffered a similar mishap.
Quote:
| Question, how fast was the ramp going if the A/C was at Mach 2? |
CJ
PS I have no record of any of the British development aircraft ever having lost a ramp, notwithstanding the number of deliberate engine surges they went hrough. But then maybe I wasn't told....
11th Dec 2010, 22:17
permalink Post: 856
Them darn intakes
Hi Guys, quite a few little points here, so here's my angle(s):
Pedalz
Ooo yes. The biggest problems we ever had associated with the ramps themselves were wear in the seals at the sides of the forward ramp. Even a few thou' over the maximum allowable side gap was enough to make the intake unstable and susceptible to surging. (It is quite interesting that the rear ramp side gaps were not in the least bit critical, and if Concorde intake development had continued, the rear ramps were going to be deleted altogether). Other failure factors were control unit malfuntions, rapid sensor drift; all of these causing either ramp/spill door drift or runaway. Primary nozzle misbehaviour could also result in intake surges. Having said all that, the monitoring of the intake system was truly superb, and surface runaways, themselves quite rare, would usually be picked up by the control system monitors causing either a lane switch or if that did not work, a total 'red light' failure with the surfaces frozen. No surge was treated as 'just one of those things', and much midnight oil was burned and hair pulled out (so that's what happened to mine
) to try and find the cause of the surge.
My friend EXWOK perfectly answered the intake hydraulics allocations.
EXWOK was right on the ball here as usual, in fact above Mach 1.6 an interactive surge was more or less guaranteed. The cause of interactive surge had nothing to do with the wing leading edge position, but to the radially generated distortion field coming out of the FRONT of the surging intake, severely distorting the adjascent intakes airflow. It mattered not if the originating surge was an inboard or an outboard intake, the other guy would always go also, above Mach 1.6.
You might want to take a look at 'When Intakes Go Wrong Part 1:
Concorde engine intake "Thrust"
and Parts 2 & 3:
Concorde engine intake "Thrust"
Not to mention Part 3:
dixi188
I can never recall this particular event happening with BA , certainly not as a result of a ramp failure. Although in the near 28 years of operation we had quite a few SNN diversions, none that I can ever recall were as the result of a ramp structural failure. The two major SNN diversions that I can recall were G-BOAF in the early 80s when an LP1 blade failed and resulted in a totally wrecked engine (although a completely contained failure) and G-BOAA in 1991, with another wrecked engine due to running in rotating stall. (Both of these events were covered previously in our thread). ChristiaanJ has mentioned quite rightly the event with A/C 001 spitting a ramp out, and Air France had a ramp failure going into JFK. (Covered previously in our thread, due to certain 'human foul ups'). I am not sure, but I think that
this
one in JFK DID require a double engine change in JFK. (Usually from SNN a BA aircraft would be 3 engine ferried back to LHR).
ChristiaanJ
Nope, you are quite right, no more French or British development aircraft ever suffered a ramp linkage failure again. The 001 ramp failure was a salutary lesson to the design team, and the intake assembly became tougher than old boots after that, nomatter WHAT you threw at it.
Due to the lateness of the hour (and me being up at 4
), that will have to do for now guys.
Best regards to all
Dude
Pedalz
Quote:
were the intake ramps in front of the engines ever known for problems? Especially during supersonic cruise where the airflow through the compressors and position of the ramps was determined by an exacting science which could turn into quite a situation if disturbed.
Which hydraulic system actuated these ramps?
|
) to try and find the cause of the surge.
My friend EXWOK perfectly answered the intake hydraulics allocations.
Quote:
| Due to the shape of the leading edge and positioning of the intakes themselves, could it be possible that disturbed airflow from a problem ramp or donk could also effect it's outboard neighbour (if I'm right in presuming that only the inboard engine surging etc. could effect the outboard and not vice versa)?[/ |
You might want to take a look at 'When Intakes Go Wrong Part 1:
Concorde engine intake "Thrust"
and Parts 2 & 3:
Concorde engine intake "Thrust"
Not to mention Part 3:
dixi188
Quote:
| A certain CFI (I think) at BA flying club, High Wycombe, who was also F/O on concorde, showed me some photographs of an engine that had eaten a piece of intake ramp. I think he said that the adjacent engine had surged and a piece of ramp went out the front and down the other engine. This resulted in a double engine failure mid atlantic. They landed in Shannon with very little fuel left. |
ChristiaanJ
Quote:
PS I have no record of any of the British development aircraft ever having lost a ramp, notwithstanding the number of deliberate engine surges they went hrough. But then maybe I wasn't told....
|
Due to the lateness of the hour (and me being up at 4
), that will have to do for now guys.
Best regards to all
Dude
Last edited by M2dude; 12th Dec 2010 at 04:51 . Reason: Adding a bit and correcting another
21st Dec 2010, 16:53
permalink Post: 926
quote:
d putting further Concorde's achievements in terms of stability; the world's only previous large delta winged Mach 2 aircraft, the B58 Hustler, had the slightly awkward feature in the case of an outer engine failure at Mach 2, in that the yaw forces were sufficient to tear the fin off. This happened on more than one occasion during service life of the Hustler, but engine failure (or far more likely a deliberate precautionary shut-down) although hardly a non-event in the case of Concorde, it was routinely dealt with without drama or danger.unquote
To rub it in, a typical double engine surge - they were nearly always double surges as the first surge expelled the ramp shock waves and turned the flow into a pitot with a large standing shock ahead of the intake that screwed up the flow into its neighbour - would produce about 1 degree sideslip and 2 deg bank. There would be a +/- 0.2g variation in normal acceleration and that was it! Through Christiaan's kind offices I am posting the records of such an event.
Hustler pilots eat your heart out!
CliveL
To rub it in, a typical double engine surge - they were nearly always double surges as the first surge expelled the ramp shock waves and turned the flow into a pitot with a large standing shock ahead of the intake that screwed up the flow into its neighbour - would produce about 1 degree sideslip and 2 deg bank. There would be a +/- 0.2g variation in normal acceleration and that was it! Through Christiaan's kind offices I am posting the records of such an event.
Hustler pilots eat your heart out!
CliveL
21st Dec 2010, 21:00
permalink Post: 934
A double engine failure, or even a double engine surge, could lead to a very nasty yaw, faster than the pilot, not necessarily instantly aware of exactly what was happening, could counter.
The designers were, right from the start, aware of this problem.
Hence, the prototypes were equipped with specific "contre automatique" (auto-rudder) computers, that would "kick in" a given rudder deflection as soon as they detected an engine failure (and twice as much in the case of a double failure).
Unfortunately... the manner of detecting an engine failure was based on pressure sensors in the engine, which proved to be notoriously unreliable.
Since the whole system was "fail-passive", in the case of a pressure sensor failure nothing happened, other than that I got the "suspect" computer dumped in my lap every time, since it was easier to swap a computer than test and swap pressure sensors....
In the end, it was always "no fault found", and the engineers had to go and test the sensors to find the failed one.
Already on the pre-production aircraft, this Rube Goldberg system was replaced by a single circuit board 'buried' in the autostab computer.
It used a lateral accelerometer to detect the abrupt yaw of a sudden engine failure or surge, and applied appropriate rudder. Look at the sudden rudder deflection 'peak' on the lateral response graph in the previous post.
Since there was no separate 'auto-rudder engage' control switch (the function was permanently active), and it was only mentioned very much in passing during training, some pilots were not even aware it existed.......
CJ
The designers were, right from the start, aware of this problem.
Hence, the prototypes were equipped with specific "contre automatique" (auto-rudder) computers, that would "kick in" a given rudder deflection as soon as they detected an engine failure (and twice as much in the case of a double failure).
Unfortunately... the manner of detecting an engine failure was based on pressure sensors in the engine, which proved to be notoriously unreliable.
Since the whole system was "fail-passive", in the case of a pressure sensor failure nothing happened, other than that I got the "suspect" computer dumped in my lap every time, since it was easier to swap a computer than test and swap pressure sensors....
In the end, it was always "no fault found", and the engineers had to go and test the sensors to find the failed one.
Already on the pre-production aircraft, this Rube Goldberg system was replaced by a single circuit board 'buried' in the autostab computer.
It used a lateral accelerometer to detect the abrupt yaw of a sudden engine failure or surge, and applied appropriate rudder. Look at the sudden rudder deflection 'peak' on the lateral response graph in the previous post.
Since there was no separate 'auto-rudder engage' control switch (the function was permanently active), and it was only mentioned very much in passing during training, some pilots were not even aware it existed.......
CJ
27th Jan 2011, 10:55
permalink Post: 1144
I don't know if this was mentioned before but I just read an article
here
about Concorde having an engine failure during certification testing for ice buildup. Perhaps someone here in PPRuNe can shed some more light into what happened and what was done to fix the problem?
30th Jan 2011, 10:38
permalink Post: 1154
Engine Bay
Pen Pusher
That really is a superb photo and shows just what a large but cramped affair the Concorde engine bay was. Although a pre-producion example, the picture generally shows what the production aircraft looked like inside the chasm. In the picture you can see the titanium roof of the engine bay that did such a good job in protecting the wing above (as was the case with the OAF engine failure in 1980 mentioned previously in this thread). What is missing from the 101s engine bay shown here are the air conditioning primary and secondary heat exchangers that were fitted above the engines. (The large trunking you can see coming forward from the jet pipes are the exhausts for the ram air from the exchangers). On a blunty, the heat exhangers are mounted in the belly of the aircraft, in what is generally known as a pack. But there was no room in Concorde for such lumpy bits, and so the only alternative was to mount them above the engine. The remainder of the equipment, the Cold Air Unit (or Air Cycle Machine as the blunties call them) as well as the, unique to Concorde, Fuel heat exchanger were mounted in the wings. With everything so sprawled about it could not really be called a 'pack' and so in Concorde we refered to an air conditioning GROUP.
The wiring you can see on the lower parts of the engine doors is generally Graviner fire wire, used for engine fire and nacelle overheat detection. At the forward part of the 2 doors (shown most clearly on the #4 engine) are two orange 'boxes. These are the engine bay ventilation 'ground running flap' electrical actuators (the flaps themselves being shown shut). Normally these spring loaded flaps would be open on the ground, being progreesively closed with increasing speed as engine bay pressure increased. The actuator would only run when the engine fire handle was pulled, to help seal off the bay. All the other orange stuff you can see is FTD, or flight teast wiring and equiment. (We used to not very kindly refer to it as 'orange s--t'
).
With regard to aircraft 204, G-BOAC I think you will find that all the engines are still installed. I took this photo (oops sorry, my wife did
) when we had a function in Manchester about 18 months ago. You can see what a wonderful job the folk up there are doing taking care of her, and as for dining under the wing.. it was truly a memorable experience indeed.
Best regards
Dude
That really is a superb photo and shows just what a large but cramped affair the Concorde engine bay was. Although a pre-producion example, the picture generally shows what the production aircraft looked like inside the chasm. In the picture you can see the titanium roof of the engine bay that did such a good job in protecting the wing above (as was the case with the OAF engine failure in 1980 mentioned previously in this thread). What is missing from the 101s engine bay shown here are the air conditioning primary and secondary heat exchangers that were fitted above the engines. (The large trunking you can see coming forward from the jet pipes are the exhausts for the ram air from the exchangers). On a blunty, the heat exhangers are mounted in the belly of the aircraft, in what is generally known as a pack. But there was no room in Concorde for such lumpy bits, and so the only alternative was to mount them above the engine. The remainder of the equipment, the Cold Air Unit (or Air Cycle Machine as the blunties call them) as well as the, unique to Concorde, Fuel heat exchanger were mounted in the wings. With everything so sprawled about it could not really be called a 'pack' and so in Concorde we refered to an air conditioning GROUP.
The wiring you can see on the lower parts of the engine doors is generally Graviner fire wire, used for engine fire and nacelle overheat detection. At the forward part of the 2 doors (shown most clearly on the #4 engine) are two orange 'boxes. These are the engine bay ventilation 'ground running flap' electrical actuators (the flaps themselves being shown shut). Normally these spring loaded flaps would be open on the ground, being progreesively closed with increasing speed as engine bay pressure increased. The actuator would only run when the engine fire handle was pulled, to help seal off the bay. All the other orange stuff you can see is FTD, or flight teast wiring and equiment. (We used to not very kindly refer to it as 'orange s--t'
).
With regard to aircraft 204, G-BOAC I think you will find that all the engines are still installed. I took this photo (oops sorry, my wife did
) when we had a function in Manchester about 18 months ago. You can see what a wonderful job the folk up there are doing taking care of her, and as for dining under the wing.. it was truly a memorable experience indeed.
Best regards
Dude
5th Apr 2011, 18:32
permalink Post: 1259
Quote:
| During the take off roll there was a power check called (by the FE, I think). I've heard this on recordings and videos variously as "power checked" and "Power set". Assuming they are one and the same check, which is correct |
I think you are referring to the 100kt call, when the F/E was expected to give a call as to the state of the powerplant [both engine and reheat] achieving desired power for take off. He was assisted in this decision by the illumination of 4 green lights [ one per engine] which came on if the engine power was OK. Should one green light fail then he would confirm the correct engine operation by observing that engine's N2 and Area position
If all OK at 100kts the F/E would call ---- "Power Set"
If not all Ok then he would call ----------" Engine Failure" which would
result in a rejected Take off
In the early days there was no concession and every take off had to have 4 green lights illuminated so the call then was " 4 Greens" , but when the concession came along that term would not fit so the change in call
The concession were
1] one green light out [seeabove]
2] and basically if weight, and airport conditions allowed it a take off could be continued even with one reheat failed at 100kts
Up to 60 kts the F/E could reselectt a failed reheat so hoping it would be
OK by 100kts
At 100kts the conditions in the above concessions applied
Above 100kts the take off would continue even if a reheat failed however
if another fails when below V1 the take off would be rejected
So finally to answer your question the correct call [well in 1998] was
" Power Set "
31st Jan 2012, 11:44
permalink Post: 1549
Perhaps more an operational than a technical question, but it's nice to see one of the sky-gods back on this thread!
I confess to occasionally firing up Microsoft Flight Simulator and SSTSIM, and am particularly impressed by the Barbados route - especially as half-way between the Azores and Barbados, you are literally a thousand miles from anywhere with limited diversion options and marginal fuel in case of engine failure and subsonic cruise. While I'm sure you had all the angles covered, was it really a nail-biting moment and what sort of contingency plans were in place?
I confess to occasionally firing up Microsoft Flight Simulator and SSTSIM, and am particularly impressed by the Barbados route - especially as half-way between the Azores and Barbados, you are literally a thousand miles from anywhere with limited diversion options and marginal fuel in case of engine failure and subsonic cruise. While I'm sure you had all the angles covered, was it really a nail-biting moment and what sort of contingency plans were in place?
31st Jan 2012, 13:33
permalink Post: 1550
fizz57
As well as carrying sufficient fuel to arrive at BGI with standard fuel reserves remaining, there was also a requirement that sufficient fuel be carried to ensure that, following an engine shut-down at any stage in the flight, Concorde could divert, on three engines, to a suitable diversion airfield, and still arrive there with standard fuel reserves remaining.
It was this requirement - the three-engined diversion requirement - that often required more fuel to be loaded - above the basic LHR-BGI flight plan fuel figure - often bringing the total fuel required up to or over the full tanks figure and so became the limiting factor on this route.
Perhaps the main difference between Concorde and most subsonic aircraft, following an engine shutdown in cruise, was that Concorde would suffer a much greater loss in range. From four-engined supersonic flight to optimum three-engined subsonic cruise the loss in range would have been in the order of 30-35%.
This was mainly because Concorde, following an engine shut-down in cruise, would have to decelerate and descend, and thus leave a very efficient flight regime, at M2.0 and 55,000-60,000ft, with relatively low drag, low winds and very cold outside air temperatures, for a much less efficient regime, at M0.95, at around 30,000ft, in a higher drag subsonic cruise with warmer outside air temperatures and much stronger, probably adverse, winds.
The forecast weather at the principal en-route diversion airfields of Santa Maria, Lajes, Bermuda and Antigua, along with the calculated wind components at subsonic cruise levels to these airfields, were all taken into account at the flight planning stage, with the forecast subsonic cruise wind component to Antigua generally being the most critical factor.
If the weather conditions at and en-route to these diversion airfields were favourable, flight planning was straightforward. If the weather conditions were unfavourable, flight planning got more difficult, but the necessary fuel was always carried, passenger numbers limited or a re-fuelling stop planned.
No, not really.
LHR-BGI was certainly the most demanding route on Concorde, and required careful planning, good tactical awareness and diligent in-flight monitoring, however the flight planning procedures and tactical decision making processes were standard and would have been very familiar to any ETOPS rated pilot.
With one exception.
Concorde would still have got you to a diversion airfield following a second engine failure!
Best Regards
Bellerophon
Quote:
| ... Barbados route...half-way between the Azores and Barbados...a thousand miles from anywhere with limited diversion options and marginal fuel in case of engine failure and subsonic cruise...what sort of contingency plans were in place?... |
As well as carrying sufficient fuel to arrive at BGI with standard fuel reserves remaining, there was also a requirement that sufficient fuel be carried to ensure that, following an engine shut-down at any stage in the flight, Concorde could divert, on three engines, to a suitable diversion airfield, and still arrive there with standard fuel reserves remaining.
It was this requirement - the three-engined diversion requirement - that often required more fuel to be loaded - above the basic LHR-BGI flight plan fuel figure - often bringing the total fuel required up to or over the full tanks figure and so became the limiting factor on this route.
Perhaps the main difference between Concorde and most subsonic aircraft, following an engine shutdown in cruise, was that Concorde would suffer a much greater loss in range. From four-engined supersonic flight to optimum three-engined subsonic cruise the loss in range would have been in the order of 30-35%.
This was mainly because Concorde, following an engine shut-down in cruise, would have to decelerate and descend, and thus leave a very efficient flight regime, at M2.0 and 55,000-60,000ft, with relatively low drag, low winds and very cold outside air temperatures, for a much less efficient regime, at M0.95, at around 30,000ft, in a higher drag subsonic cruise with warmer outside air temperatures and much stronger, probably adverse, winds.
The forecast weather at the principal en-route diversion airfields of Santa Maria, Lajes, Bermuda and Antigua, along with the calculated wind components at subsonic cruise levels to these airfields, were all taken into account at the flight planning stage, with the forecast subsonic cruise wind component to Antigua generally being the most critical factor.
If the weather conditions at and en-route to these diversion airfields were favourable, flight planning was straightforward. If the weather conditions were unfavourable, flight planning got more difficult, but the necessary fuel was always carried, passenger numbers limited or a re-fuelling stop planned.
Quote:
| ...While I'm sure you had all the angles covered, was it really a nail-biting moment... |
LHR-BGI was certainly the most demanding route on Concorde, and required careful planning, good tactical awareness and diligent in-flight monitoring, however the flight planning procedures and tactical decision making processes were standard and would have been very familiar to any ETOPS rated pilot.
With one exception.
Concorde would still have got you to a diversion airfield following a second engine failure!
Best Regards
Bellerophon
4th Sep 2012, 07:06
permalink Post: 1685
reverser incident 70s
hi guys, thanks for a very informative thread.
In the mid 70s I lived in a thatch cottage 31nm west of LHR at the bottom of a hill in the Thames valley.
One particularly grotty dark autumn evening our cottage started shaking, I rushed out into the dark expecting to see a car crash but realised it was a low flying aircraft. (I wasn't a stranger to low aircraft noise as we were in the Greenham Common circuit and the F111 had been based here when Upper Heyford was resurfaced).
I later read that droop snoop had an engine go into reverse in cruise.
The subsequent report in the horror comic was of it's following take off when it happened again on rotate.
What I remembered was some sort of award to engines or probably the whole crew and that she didn't get above three thou until crossing the Bristol coast.
questions...
Was it a simple electrical failure?
Was there any protection to stop it happening again?
Was there a significant speed loss when it happened?
Was there a problem with the adjacent engine?
Flying questions.
What was the engine out climb procedure?
Was there another double engine failure procedure as on the iron duck with immediate fuel dumping?
Was it just a coincidence that the flight was routed outside of CAS but along the Thames valley avoiding the high ground to the north and Membury mast?
Thanks
sorry if it has already been covered but have only got through to page 50...
In the mid 70s I lived in a thatch cottage 31nm west of LHR at the bottom of a hill in the Thames valley.
One particularly grotty dark autumn evening our cottage started shaking, I rushed out into the dark expecting to see a car crash but realised it was a low flying aircraft. (I wasn't a stranger to low aircraft noise as we were in the Greenham Common circuit and the F111 had been based here when Upper Heyford was resurfaced).
I later read that droop snoop had an engine go into reverse in cruise.
The subsequent report in the horror comic was of it's following take off when it happened again on rotate.
What I remembered was some sort of award to engines or probably the whole crew and that she didn't get above three thou until crossing the Bristol coast.
questions...
Was it a simple electrical failure?
Was there any protection to stop it happening again?
Was there a significant speed loss when it happened?
Was there a problem with the adjacent engine?
Flying questions.
What was the engine out climb procedure?
Was there another double engine failure procedure as on the iron duck with immediate fuel dumping?
Was it just a coincidence that the flight was routed outside of CAS but along the Thames valley avoiding the high ground to the north and Membury mast?
Thanks
sorry if it has already been covered but have only got through to page 50...
8th May 2013, 16:05
permalink Post: 1714
For the french speaking (or reading) people here, I just found a mine of very interesting informations about Concorde on this website:
Accueil
This site has a database of thousand of concorde flights with the following datas: Date and time of the flight, airframe used, technical and commercial crews, guests, departure/arrival airports and flight type (regular, charter world tour...).
On top of that, many infos and stories around Concorde can also be found there.
I can't resist to translate one of those stories (I'm far from being a native english speaker or a professional translator; so forgive me for the misspellings and other translation mistakes). It is a report about one of the biggest incident that happened to the prototype 001 during the flight tests:
Shock of shockwaves
We were flying with Concorde at Mach 2 since 3 month already on both side of the Channel. The prototype 001 did outstrip 002 which was supposed to be the first to reach Mach 2.
Unfortunately, a technical issue delayed 002 and Brian Trubshaw fairly let Andr\xe9 Turcat be the first to reach Mach 2 with the 001 which was ready to go.
The flight tests were progressing fast and we were discovering a part of the atmosphere that military aircrafts hardly reached before. With Concorde, we were able to stay there for hours although limited by the huge fuel consumption of the prototypes.
The Olympus engines did not reached their nominal performance yet and, most of the time, we had to turn on the reheat in supersonic cruise to maintain Mach 2.
The reheat is what we call afterburner on military aircrafts. Fuel is injected between the last compressor stage of the low pressure turbine and the first exhaust nozzle. This increases the thrust for the whole engine and its nozzle.
The 4 reheats, one for each engine, are controlled by the piano switches behind the thrust leavers on the center pedestal between the two pilots. Air was fed into the engines through 4 air intakes, one for each engine, attached 2 by 2 to the 2 engine nacelle, one under each wing. The advantage in terms of drag reduction was obvious.
However, tests in wind tunnel showed that, at supersonic speed, if a problem happens on one engine, there was a great chance for the adjacent engine to be affected as well by the shockwave interference from one air intake to the other despite the presence the dividing wall between the two intakes. So we knew that an engine failure at mach 2 would result in the loss of 2 engines on the same side, resulting in a lateral movement leading to a strong sideslip that would likely impact the 2 remaining engines and transform the aircraft into the fastest glider in the world.
This is why an automatic anti sideslip device was developed and installed on the aircrafts.
The air intakes are very sophisticated. At mach 2, it creates a system of shockwaves that slows down the air from 600 m/sec in front of the aircraft to 200 m/sec in front of the engine while maintaining a very good thermodynamic performance. In supersonic cruise, the engines, operating at full capacity all the time, were sensitive to any perturbation and reacted violently with engine surge: the engine refusing the incoming air.
Stopping suddenly a flow of almost 200kg of air per second traveling at 600m/sec causes a few problems. As a result, a spill door was installed under the air intake and automatically opened in such event.
To control the system of shockwaves and obtain an efficiency of 0,96 in compression in the air intake, 2 articulated ramps, controlled by hydraulic jacks, are installed on the top of the air intakes in front of the engines. Each ramp is roughly the size of a big dining room table, and the 2 ramps, mechanically synchronized, move up or down following the instruction of an highly sophisticated computer that adapts the ramp position according to the mach number, the engine rating and other parameters such as skidding.
At that time, it was the less known part of the aircraft, almost only designed through calculation since no simulator, no wind tunnel, did allow a full scale test of the system.
The control of the system was analog and very complex but it was not easy to tune and we were moving ahead with a lot of caution in our test at mach 2.
On the 26th of January 1971, we were doing a nearly routine flight to measure the effect of a new engine setting supposed to enhance the engine efficiency at mach 2. It was a small increase of the rotation speed of the low pressure turbine increasing the air flow and, as a result, the thrust.
The flight test crews now regularly alternate their participation and their position in the cockpit for the pilots.
Today, Gilbert Defer is on the left side, myself on the right side, Michel R\xe9tif is the flight engineer, Claude Durand is the main flight engineer and Jean Conche is the engine flight engineer. With them is an official representative of the flight test centre, Hubert Guyonnet, seated in the cockpit's jump seat, he is in charge of radio testing.
We took off from Toulouse, accelerated to supersonic speed over the Atlantic near Arcachon continuing up to the north west of Ireland.
Two reheats, the 1 and the 3, are left on because the air temperature does not allow to maintain mach 2 without them.
Everything goes fine. During the previous flight, the crew experienced some strong turbulence, quite rare in the stratosphere and warned us about this. No problem was found on the aircraft.
We are on our way back to Toulouse off the coast of Ireland. Our program includes subsonic tests and we have to decelerate.
Gilbert is piloting the aircraft. Michel and the engineers notify us that everything is normal and ready for the deceleration and the descent.
We are at FL500 at mach 2 with an IAS of 530 kt, the maximum dynamic pressure in normal use.
On Concorde, the right hand seat is the place offering the less possibility to operate the systems. But here, we get busy by helping the others to follow the program and the checklists and by manipulating the secondary commands such as the landing gear, the droop nose, the radio navigation, comms, and some essential engine settings apart from the thrust leavers such as the reheat switches.
The normal procedure consists in stopping the reheat before lowering the throttle.
Gilbert asks me to do it. After, he will slowly reduce the throttle to avoid temporary heckler. Note that he did advise us during the training on the air intake to avoid to move the thrust leaver in case of engine surge.
As a safety measure, I shut down the reheat one by one, checking that everything goes fine for each one. Thus I switch off the reheat 1 with the light shock marking the thrust reduction. Then the 3\x85
Instantly, we are thrown in a crazy situation.
Deafening noise like a canon firing 300 times a minute next to us. Terrible shake. The cockpit, that looked like a submarine with the metallic and totally opaque visor obviously in the upper position, is shaken at a frequency of 5 oscillation a second and a crazy amplitude of about 4 to 5 G. To the point that we cannot see anymore, our eyes not being able to follow the movements.
Gilbert has a test pilot reaction, we have to get out of the maximum kinetic energy zone as fast as possible and to reduce speed immediately. He then moves the throttle to idle without any useless care.
During that time, I try, we all try to answer the question: what is going on? What is the cause of this and what can we do to stop it?
Suspecting an issue with the engines, I try to read the indicators on the centre control panel through the mist of my disturbed vision and in the middle of a rain of electric indicators falling from the roof. We cannot speak to each other through the intercom.
I vaguely see that the engines 3 and 4 seem to run slower than the 2 others, especially the 4. We have to do something. Gilbert is piloting the plane and is already busy. I have a stupid reaction dictated by the idea that I have to do something to stop that, while I can only reach a few commands that may be linked to the problem.
I first try to increase the thrust on number 4 engine. No effect so I reduce frankly and definitively. I desperately look for something to do from my right hand seat with a terrible feeling of being helpless and useless.
Then everything stops as suddenly as it started. How long did it last, 30 seconds, one minute?
By looking at the flight data records afterward, we saw that it only last\x85 12 seconds!
However, I have the feeling that I had time to think about tons of things, to do a lot of reasoning, assumption and to have searched and searched and searched\x85! It looked like my brain suddenly switched to a fastest mod of thinking. But, above all, it's the feeling of failure, the fact that I was not able to do anything and that I did not understand anything that remains stuck in my mind forever.
To comfort me, I have to say that nobody among the crew did understand anything either and was able to do anything, apart from Gilbert.
The aircraft slows down and the engine 3 that seemed to have shut down restart thanks to the auto ignition system. But the 4 is off indeed.
Michel makes a check of his instruments. He also notes that the engine 4 has shut down but the 4 air intakes work normally, which makes us feel better. After discussing together, we start to think that we probably faced some stratospheric turbulence of very high intensity, our experience in this altitude range being quite limited at that time. But nobody really believes in this explanation. Finally, at subsonic speed, mach 0.9, with all instruments looking normal, we try to restart engine 4 since we still have a long way to go to fly back to Toulouse.
Michel launches the process to restart the engine. It restarts, remains at a medium rotation speed and shuts down after 20 seconds, leaving us puzzled and a bit worried despite the fact that the instrument indicators are normal.
Gilbert then decide to give up and won't try to restart this engine anymore and Claude leaves his engineer station to have a look in a device installed on the prototype to inspect the landing gear and the engines when needed: an hypo-scope, a kind of periscope going out through the floor and not through the roof.
After a few seconds, we can hear him on the intercom:
"Shit! (stuttering) we have lost the intake number 4."
He then describes a wide opening in the air intake, the ramp seems to be missing and he can see some structural damages on the nacelle.
Gilbert reacts rapidly by further reducing the speed to limit even more the dynamic pressure.
But we don't know exactly the extent of the damage. Are the wing and the control surfaces damaged? What about engine 3?
We decide to fly back at a speed of 250 kts at a lower altitude and to divert toward Fairford where our british colleagues and the 002 are based. I inform everybody about the problem on the radio and tell them our intentions. However, I add that if no other problems occur, we will try to reach Toulouse since we still have enough fuel.
Flying off Fairford, since nothing unusual happened, we decide to go on toward Toulouse. All the possible diversion airport on the way have been informed by the flight test centre who follows us on their radar.
At low speed, knowing what happened to us and having nothing else to do but to wait for us, time passes slowly, very slowly and we don't talk much, each one of us thinking and trying to understand what happened. However, we keep watching closely after engine 3.
Personally, I remember the funny story of the poor guy who sees his house collapse when he flushes his toilets. I feel in the same situation.
Gilbert makes a precautionary landing since we don't rely much on engine 3 anymore. But everything goes fine.
At the parking, there is a lot of people waiting for us and, as soon as the engines stop, we can see a big rush toward the nacelles of the right hand side engines.
Gilbert and myself are the first to get off the plane and we are welcomed down the stairs by Andr\xe9 Turcat and Jean Franchi who came out from the crowd watching at the right hand side nacelle.
They both behave the same way, with a slow pace attitude, the same look, a mix of disbelief and frustration.
Andr\xe9 is the first to speak: "I can't believe we were not on this flight, really unlucky\x85". Yes, this flight was supposed to be just a routine flight\x85!
The condition of the nacelle is impressive. We come closer and everybody move aside for us with a look of disbelief and respect as if we were hell survivors.
The ramps of the intake 4, those 2 "dining tables", have completely disappeared leaving a hole where we can see the hydraulic jacks and the stub rod where the ramps were attached.
Indeed, only the ramps were missing, apparently ejected forward which was unbelievable knowing how fast we were flying. The ramp slipped under the nacelle causing some damages on it and on the hood of one of the elevon's servo control. Fortunately, the control did not suffer any damage.
What is left of the rear ramp seems to be blocked down inside the intake in front of the engine and we can see behind it the first blades of the compressor, or what is left of it, not much.
The engine swallowed a huge amount of metal but no vital parts of the aircraft has been damaged, no hydraulic leaks, no fuel leaks. I remembered at that time the stories of some B58 Hustler accident where the loss of an engine at mach 2 almost certainly ended with the complete loss of the aircraft. Our Concorde has only been shaken. This incident strengthened the trust I had in this plane. And I was not unhappy to have experienced this ordeal, especially when I saw the frustration on the face of Andr\xe9 Turcat and Jean Franchi.
But we had to understand what happened and how; and also why the ramp's fixing broke.
It didn't take much time to get the answers.
I unintentionally triggered the problem when shutting down the reheat of engine 3. The sudden stop of the fuel flow did of course stop the combustion and the back pressure behind the low pressure turbine. But, probably because of the modification made on the engine before the flight, the stop of the reheat has not been followed by the normal closing movement of the primary nozzle to compensate the pressure drop. So the low pressure turbine ran out of control, dragging down the low pressure compressor which reacts by surging.
Despite the opening of the spill door, the engine surge led to a sudden movement of the shockwaves in the air intake creating a surge in the intake itself. A similar surge happened in the adjacent intake 4 followed by a surge of the corresponding engine. This caused an excessive pressure above the ramps and the fixings of the intake 4 did not hold.
Since it was the first time we experienced a surge in the air intake, we had little knowledge of the stress it would create on the ramps. This led to miscalculation of the strength of the ramps's frames and they did brake.
Another mistake: instead of installing the motion detectors on the ramp itself, to make the production easier, they have been placed on the arms of the hydraulic jacks. This is why Michel R\xe9tif thought that the position of the ramps were correct. The hydraulic jacks did not suffer any damage and were still working normally even if the ramps were missing.
All the data recorded during this event helped us in redesigning the air intakes and the flight test program resumed three month later.
After this, we deliberately created dozen and dozen of air intake surge to fine tune the way to regulate them with digital calculator this time.
From now on, even if it was still very impressive, it was safe and their intensity was not comparable with what we experienced with the missing ramps.
However, a french president may kept a lasting memory of this, much later, during a flight back from Saudi Arabia. This time, I was on the left side, Gilbert on the right and Michel was still in the third seat\x85 But that's another story.
For me, the lasting impression of failing and being helpless during this incident made me wonder what a commercial pilot would have done in this situation. This plane was designed to be handled by standard commercial pilots and not only by the flight test pilots.
At that time, I was interested in taking in charge the management of a training center for the pilots of the future Airbus's clients. This event pushed me that way and I made it clear that I wanted to add the flight training on Concorde in this project. This has been agreed and I did it.
And the Concorde training program now covers the air intake surges and how to deal with them.
Jean PINET
Former test pilot
Member and former president of the Air and Space Academy
Accueil
This site has a database of thousand of concorde flights with the following datas: Date and time of the flight, airframe used, technical and commercial crews, guests, departure/arrival airports and flight type (regular, charter world tour...).
On top of that, many infos and stories around Concorde can also be found there.
I can't resist to translate one of those stories (I'm far from being a native english speaker or a professional translator; so forgive me for the misspellings and other translation mistakes). It is a report about one of the biggest incident that happened to the prototype 001 during the flight tests:
Shock of shockwaves
We were flying with Concorde at Mach 2 since 3 month already on both side of the Channel. The prototype 001 did outstrip 002 which was supposed to be the first to reach Mach 2.
Unfortunately, a technical issue delayed 002 and Brian Trubshaw fairly let Andr\xe9 Turcat be the first to reach Mach 2 with the 001 which was ready to go.
The flight tests were progressing fast and we were discovering a part of the atmosphere that military aircrafts hardly reached before. With Concorde, we were able to stay there for hours although limited by the huge fuel consumption of the prototypes.
The Olympus engines did not reached their nominal performance yet and, most of the time, we had to turn on the reheat in supersonic cruise to maintain Mach 2.
The reheat is what we call afterburner on military aircrafts. Fuel is injected between the last compressor stage of the low pressure turbine and the first exhaust nozzle. This increases the thrust for the whole engine and its nozzle.
The 4 reheats, one for each engine, are controlled by the piano switches behind the thrust leavers on the center pedestal between the two pilots. Air was fed into the engines through 4 air intakes, one for each engine, attached 2 by 2 to the 2 engine nacelle, one under each wing. The advantage in terms of drag reduction was obvious.
However, tests in wind tunnel showed that, at supersonic speed, if a problem happens on one engine, there was a great chance for the adjacent engine to be affected as well by the shockwave interference from one air intake to the other despite the presence the dividing wall between the two intakes. So we knew that an engine failure at mach 2 would result in the loss of 2 engines on the same side, resulting in a lateral movement leading to a strong sideslip that would likely impact the 2 remaining engines and transform the aircraft into the fastest glider in the world.
This is why an automatic anti sideslip device was developed and installed on the aircrafts.
The air intakes are very sophisticated. At mach 2, it creates a system of shockwaves that slows down the air from 600 m/sec in front of the aircraft to 200 m/sec in front of the engine while maintaining a very good thermodynamic performance. In supersonic cruise, the engines, operating at full capacity all the time, were sensitive to any perturbation and reacted violently with engine surge: the engine refusing the incoming air.
Stopping suddenly a flow of almost 200kg of air per second traveling at 600m/sec causes a few problems. As a result, a spill door was installed under the air intake and automatically opened in such event.
To control the system of shockwaves and obtain an efficiency of 0,96 in compression in the air intake, 2 articulated ramps, controlled by hydraulic jacks, are installed on the top of the air intakes in front of the engines. Each ramp is roughly the size of a big dining room table, and the 2 ramps, mechanically synchronized, move up or down following the instruction of an highly sophisticated computer that adapts the ramp position according to the mach number, the engine rating and other parameters such as skidding.
At that time, it was the less known part of the aircraft, almost only designed through calculation since no simulator, no wind tunnel, did allow a full scale test of the system.
The control of the system was analog and very complex but it was not easy to tune and we were moving ahead with a lot of caution in our test at mach 2.
On the 26th of January 1971, we were doing a nearly routine flight to measure the effect of a new engine setting supposed to enhance the engine efficiency at mach 2. It was a small increase of the rotation speed of the low pressure turbine increasing the air flow and, as a result, the thrust.
The flight test crews now regularly alternate their participation and their position in the cockpit for the pilots.
Today, Gilbert Defer is on the left side, myself on the right side, Michel R\xe9tif is the flight engineer, Claude Durand is the main flight engineer and Jean Conche is the engine flight engineer. With them is an official representative of the flight test centre, Hubert Guyonnet, seated in the cockpit's jump seat, he is in charge of radio testing.
We took off from Toulouse, accelerated to supersonic speed over the Atlantic near Arcachon continuing up to the north west of Ireland.
Two reheats, the 1 and the 3, are left on because the air temperature does not allow to maintain mach 2 without them.
Everything goes fine. During the previous flight, the crew experienced some strong turbulence, quite rare in the stratosphere and warned us about this. No problem was found on the aircraft.
We are on our way back to Toulouse off the coast of Ireland. Our program includes subsonic tests and we have to decelerate.
Gilbert is piloting the aircraft. Michel and the engineers notify us that everything is normal and ready for the deceleration and the descent.
We are at FL500 at mach 2 with an IAS of 530 kt, the maximum dynamic pressure in normal use.
On Concorde, the right hand seat is the place offering the less possibility to operate the systems. But here, we get busy by helping the others to follow the program and the checklists and by manipulating the secondary commands such as the landing gear, the droop nose, the radio navigation, comms, and some essential engine settings apart from the thrust leavers such as the reheat switches.
The normal procedure consists in stopping the reheat before lowering the throttle.
Gilbert asks me to do it. After, he will slowly reduce the throttle to avoid temporary heckler. Note that he did advise us during the training on the air intake to avoid to move the thrust leaver in case of engine surge.
As a safety measure, I shut down the reheat one by one, checking that everything goes fine for each one. Thus I switch off the reheat 1 with the light shock marking the thrust reduction. Then the 3\x85
Instantly, we are thrown in a crazy situation.
Deafening noise like a canon firing 300 times a minute next to us. Terrible shake. The cockpit, that looked like a submarine with the metallic and totally opaque visor obviously in the upper position, is shaken at a frequency of 5 oscillation a second and a crazy amplitude of about 4 to 5 G. To the point that we cannot see anymore, our eyes not being able to follow the movements.
Gilbert has a test pilot reaction, we have to get out of the maximum kinetic energy zone as fast as possible and to reduce speed immediately. He then moves the throttle to idle without any useless care.
During that time, I try, we all try to answer the question: what is going on? What is the cause of this and what can we do to stop it?
Suspecting an issue with the engines, I try to read the indicators on the centre control panel through the mist of my disturbed vision and in the middle of a rain of electric indicators falling from the roof. We cannot speak to each other through the intercom.
I vaguely see that the engines 3 and 4 seem to run slower than the 2 others, especially the 4. We have to do something. Gilbert is piloting the plane and is already busy. I have a stupid reaction dictated by the idea that I have to do something to stop that, while I can only reach a few commands that may be linked to the problem.
I first try to increase the thrust on number 4 engine. No effect so I reduce frankly and definitively. I desperately look for something to do from my right hand seat with a terrible feeling of being helpless and useless.
Then everything stops as suddenly as it started. How long did it last, 30 seconds, one minute?
By looking at the flight data records afterward, we saw that it only last\x85 12 seconds!
However, I have the feeling that I had time to think about tons of things, to do a lot of reasoning, assumption and to have searched and searched and searched\x85! It looked like my brain suddenly switched to a fastest mod of thinking. But, above all, it's the feeling of failure, the fact that I was not able to do anything and that I did not understand anything that remains stuck in my mind forever.
To comfort me, I have to say that nobody among the crew did understand anything either and was able to do anything, apart from Gilbert.
The aircraft slows down and the engine 3 that seemed to have shut down restart thanks to the auto ignition system. But the 4 is off indeed.
Michel makes a check of his instruments. He also notes that the engine 4 has shut down but the 4 air intakes work normally, which makes us feel better. After discussing together, we start to think that we probably faced some stratospheric turbulence of very high intensity, our experience in this altitude range being quite limited at that time. But nobody really believes in this explanation. Finally, at subsonic speed, mach 0.9, with all instruments looking normal, we try to restart engine 4 since we still have a long way to go to fly back to Toulouse.
Michel launches the process to restart the engine. It restarts, remains at a medium rotation speed and shuts down after 20 seconds, leaving us puzzled and a bit worried despite the fact that the instrument indicators are normal.
Gilbert then decide to give up and won't try to restart this engine anymore and Claude leaves his engineer station to have a look in a device installed on the prototype to inspect the landing gear and the engines when needed: an hypo-scope, a kind of periscope going out through the floor and not through the roof.
After a few seconds, we can hear him on the intercom:
"Shit! (stuttering) we have lost the intake number 4."
He then describes a wide opening in the air intake, the ramp seems to be missing and he can see some structural damages on the nacelle.
Gilbert reacts rapidly by further reducing the speed to limit even more the dynamic pressure.
But we don't know exactly the extent of the damage. Are the wing and the control surfaces damaged? What about engine 3?
We decide to fly back at a speed of 250 kts at a lower altitude and to divert toward Fairford where our british colleagues and the 002 are based. I inform everybody about the problem on the radio and tell them our intentions. However, I add that if no other problems occur, we will try to reach Toulouse since we still have enough fuel.
Flying off Fairford, since nothing unusual happened, we decide to go on toward Toulouse. All the possible diversion airport on the way have been informed by the flight test centre who follows us on their radar.
At low speed, knowing what happened to us and having nothing else to do but to wait for us, time passes slowly, very slowly and we don't talk much, each one of us thinking and trying to understand what happened. However, we keep watching closely after engine 3.
Personally, I remember the funny story of the poor guy who sees his house collapse when he flushes his toilets. I feel in the same situation.
Gilbert makes a precautionary landing since we don't rely much on engine 3 anymore. But everything goes fine.
At the parking, there is a lot of people waiting for us and, as soon as the engines stop, we can see a big rush toward the nacelles of the right hand side engines.
Gilbert and myself are the first to get off the plane and we are welcomed down the stairs by Andr\xe9 Turcat and Jean Franchi who came out from the crowd watching at the right hand side nacelle.
They both behave the same way, with a slow pace attitude, the same look, a mix of disbelief and frustration.
Andr\xe9 is the first to speak: "I can't believe we were not on this flight, really unlucky\x85". Yes, this flight was supposed to be just a routine flight\x85!
The condition of the nacelle is impressive. We come closer and everybody move aside for us with a look of disbelief and respect as if we were hell survivors.
The ramps of the intake 4, those 2 "dining tables", have completely disappeared leaving a hole where we can see the hydraulic jacks and the stub rod where the ramps were attached.
Indeed, only the ramps were missing, apparently ejected forward which was unbelievable knowing how fast we were flying. The ramp slipped under the nacelle causing some damages on it and on the hood of one of the elevon's servo control. Fortunately, the control did not suffer any damage.
What is left of the rear ramp seems to be blocked down inside the intake in front of the engine and we can see behind it the first blades of the compressor, or what is left of it, not much.
The engine swallowed a huge amount of metal but no vital parts of the aircraft has been damaged, no hydraulic leaks, no fuel leaks. I remembered at that time the stories of some B58 Hustler accident where the loss of an engine at mach 2 almost certainly ended with the complete loss of the aircraft. Our Concorde has only been shaken. This incident strengthened the trust I had in this plane. And I was not unhappy to have experienced this ordeal, especially when I saw the frustration on the face of Andr\xe9 Turcat and Jean Franchi.
But we had to understand what happened and how; and also why the ramp's fixing broke.
It didn't take much time to get the answers.
I unintentionally triggered the problem when shutting down the reheat of engine 3. The sudden stop of the fuel flow did of course stop the combustion and the back pressure behind the low pressure turbine. But, probably because of the modification made on the engine before the flight, the stop of the reheat has not been followed by the normal closing movement of the primary nozzle to compensate the pressure drop. So the low pressure turbine ran out of control, dragging down the low pressure compressor which reacts by surging.
Despite the opening of the spill door, the engine surge led to a sudden movement of the shockwaves in the air intake creating a surge in the intake itself. A similar surge happened in the adjacent intake 4 followed by a surge of the corresponding engine. This caused an excessive pressure above the ramps and the fixings of the intake 4 did not hold.
Since it was the first time we experienced a surge in the air intake, we had little knowledge of the stress it would create on the ramps. This led to miscalculation of the strength of the ramps's frames and they did brake.
Another mistake: instead of installing the motion detectors on the ramp itself, to make the production easier, they have been placed on the arms of the hydraulic jacks. This is why Michel R\xe9tif thought that the position of the ramps were correct. The hydraulic jacks did not suffer any damage and were still working normally even if the ramps were missing.
All the data recorded during this event helped us in redesigning the air intakes and the flight test program resumed three month later.
After this, we deliberately created dozen and dozen of air intake surge to fine tune the way to regulate them with digital calculator this time.
From now on, even if it was still very impressive, it was safe and their intensity was not comparable with what we experienced with the missing ramps.
However, a french president may kept a lasting memory of this, much later, during a flight back from Saudi Arabia. This time, I was on the left side, Gilbert on the right and Michel was still in the third seat\x85 But that's another story.
For me, the lasting impression of failing and being helpless during this incident made me wonder what a commercial pilot would have done in this situation. This plane was designed to be handled by standard commercial pilots and not only by the flight test pilots.
At that time, I was interested in taking in charge the management of a training center for the pilots of the future Airbus's clients. This event pushed me that way and I made it clear that I wanted to add the flight training on Concorde in this project. This has been agreed and I did it.
And the Concorde training program now covers the air intake surges and how to deal with them.
Jean PINET
Former test pilot
Member and former president of the Air and Space Academy
Last edited by NHerby; 9th May 2013 at 17:24 .