19th Aug 2010, 11:16
permalink Post: 25
Biggles78
Stupid, you? no way!! (Besides, I'm Mr Stupid of the aviation world, that's my title
). The thing is, out here in the world of flying machines, there are almost an infinite number of questions (and hopefully answers too). This applies to just about all aircraft from the Wright Flyer up!!.
Keep asking away, there are so many of us Concorde 'nuts' out here who are more than happy to help out/bore the socks off you.
Fuel burns: The problem was that when flying slow/taxying, Concorde was an extreme gas guzzler, even when idling each engine burnt around 1.1 tonnes/hour (so every 15 minutes after push back meant over a tonne gone). A typical taxi fuel would be around 1.4/1.5 tonnes, depending on the runway in use on the day. I'd have to leave it to some of my pilot/F/E friends to remember some of the specific fuel burns after take off etc, but I can at least give you some interesting consumption figures:
At the beginning of the take off roll, each engine would be burning around 21 tonnes/hour. (Made up of around 12 T/Hr dry fuel (Fe) and 9T/Hr afterburner (reheat to us Brits) fuel (Fr). As Fr was scheduled against Fe, as a function of inlet total temp (T1) by the time V2 was reached (around 220 KTS) the rising T1 has pushed the total fuel flow (Ft) up to a staggering 25 tonnes/hour/engine. As i've pointed out before in previous topics, although the afterburner only gave us a 17% improvement in take off thrust, it was responsible for around an 80% hike in fuel burn. (Hence that is whay it was only used sparingly). However when reheat was used for transonic acceleration, it used a dramatically reduced schedule (roughly a 60% rise in fuel flow) , so it was not quite as scary. The afterburner would be lit at the commencement of the acceleration (0.96 Mach) and cancelled completely at 1.7 Mach. After this time the aircraft would accelerate on dry power only up to mach 2 and beyond. (The cooler the temperature the quicker the time to Mach 2). On an ISA+ day, it sometimes felt that the aircraft was flying through cold porridge, and could take quite a while to get to Mach 2 after reaheat cancellation, where as on a nice ISA - day, she would go like a bat out of hell, and the AFCS would have to jump in to prevent overspeeds.
Before I hit some more numbers, let me say that with Concorde, TOC = TOD!! After reheat cancellation at Mach 1.7, the aircraft would be at FL 430. The aircraft would climb at an IAS of 530 KTS until Mach 2 was reached at fractionally over FL500. From then on the aircraft would cruise/climb as fuel was burnt, up to a maximum of FL600. On warmish days (eg. the North Atlantic) TOD would typically be around FL570-580. On a cool day (the lowes temperatures would of course be reached in the more tropical regions; the LGR-BGI sector encountered this), FL 600 would be reached easily and she would love to climb some more. BUT, the aircaft was only certificated to 60,000' with passengers onboard, for decompression emergency descent time reasons, and so we were stuck with it. The pity is of course, the fuel burn would have been improved, but we never were able to take advantage of this. On test flights however, the aircraft would routinely zoom climb to FL 630. On her maiden flight, aircaft 208 (G-BOAB) reached an altitude of 65000'; the highest recorded Concorde altitude was on one of the French development aircraft, which achieved 68,000'. On a technical point, the analog ADC's were 'only' calibrated to 65,000'.
Anyway, back to some figues; at Mach 2, 50,000', the typical fuel burn per engine would be around 5 tonnes/hour, falling to around 4.2 tonnes/hour at 60,000'.
THE NOSE You are quite correct in your assumption, there were two positions of droop: 5 deg's for taxi/take-off and low speed flight and 12.5 deg's for landing. The glazed visor retracted into the nose and could ONLY be raised once the nose was fully up, and had to be stowed before the nose could move down. There were 2 emergency nose lowering sysyems; one using stby (Yellow) hydraulics and a free-fall system. Free-fall would drop the nose all the way to 12.5 deg's, the visor free falling into the nose also.
Stupid, you? no way!! (Besides, I'm Mr Stupid of the aviation world, that's my title
). The thing is, out here in the world of flying machines, there are almost an infinite number of questions (and hopefully answers too). This applies to just about all aircraft from the Wright Flyer up!!.
Keep asking away, there are so many of us Concorde 'nuts' out here who are more than happy to help out/bore the socks off you.
Fuel burns: The problem was that when flying slow/taxying, Concorde was an extreme gas guzzler, even when idling each engine burnt around 1.1 tonnes/hour (so every 15 minutes after push back meant over a tonne gone). A typical taxi fuel would be around 1.4/1.5 tonnes, depending on the runway in use on the day. I'd have to leave it to some of my pilot/F/E friends to remember some of the specific fuel burns after take off etc, but I can at least give you some interesting consumption figures:
At the beginning of the take off roll, each engine would be burning around 21 tonnes/hour. (Made up of around 12 T/Hr dry fuel (Fe) and 9T/Hr afterburner (reheat to us Brits) fuel (Fr). As Fr was scheduled against Fe, as a function of inlet total temp (T1) by the time V2 was reached (around 220 KTS) the rising T1 has pushed the total fuel flow (Ft) up to a staggering 25 tonnes/hour/engine. As i've pointed out before in previous topics, although the afterburner only gave us a 17% improvement in take off thrust, it was responsible for around an 80% hike in fuel burn. (Hence that is whay it was only used sparingly). However when reheat was used for transonic acceleration, it used a dramatically reduced schedule (roughly a 60% rise in fuel flow) , so it was not quite as scary. The afterburner would be lit at the commencement of the acceleration (0.96 Mach) and cancelled completely at 1.7 Mach. After this time the aircraft would accelerate on dry power only up to mach 2 and beyond. (The cooler the temperature the quicker the time to Mach 2). On an ISA+ day, it sometimes felt that the aircraft was flying through cold porridge, and could take quite a while to get to Mach 2 after reaheat cancellation, where as on a nice ISA - day, she would go like a bat out of hell, and the AFCS would have to jump in to prevent overspeeds.
Before I hit some more numbers, let me say that with Concorde, TOC = TOD!! After reheat cancellation at Mach 1.7, the aircraft would be at FL 430. The aircraft would climb at an IAS of 530 KTS until Mach 2 was reached at fractionally over FL500. From then on the aircraft would cruise/climb as fuel was burnt, up to a maximum of FL600. On warmish days (eg. the North Atlantic) TOD would typically be around FL570-580. On a cool day (the lowes temperatures would of course be reached in the more tropical regions; the LGR-BGI sector encountered this), FL 600 would be reached easily and she would love to climb some more. BUT, the aircaft was only certificated to 60,000' with passengers onboard, for decompression emergency descent time reasons, and so we were stuck with it. The pity is of course, the fuel burn would have been improved, but we never were able to take advantage of this. On test flights however, the aircraft would routinely zoom climb to FL 630. On her maiden flight, aircaft 208 (G-BOAB) reached an altitude of 65000'; the highest recorded Concorde altitude was on one of the French development aircraft, which achieved 68,000'. On a technical point, the analog ADC's were 'only' calibrated to 65,000'.
Anyway, back to some figues; at Mach 2, 50,000', the typical fuel burn per engine would be around 5 tonnes/hour, falling to around 4.2 tonnes/hour at 60,000'.
THE NOSE You are quite correct in your assumption, there were two positions of droop: 5 deg's for taxi/take-off and low speed flight and 12.5 deg's for landing. The glazed visor retracted into the nose and could ONLY be raised once the nose was fully up, and had to be stowed before the nose could move down. There were 2 emergency nose lowering sysyems; one using stby (Yellow) hydraulics and a free-fall system. Free-fall would drop the nose all the way to 12.5 deg's, the visor free falling into the nose also.
Last edited by M2dude; 19th Aug 2010 at 12:40 . Reason: mistooks
27th Aug 2010, 15:55
permalink Post: 137
stilton
Really a question for my pilot friends, BUT.. I do recall that several years ago an RAF Tornado F3 requested permission to try a practice intercept on a JFK bound aircraft coming up to the accel' point... ATC relayed the request to the crew who had no objections, provided tha the rules of the air were obeyed, the ATC conversation went something like this.... 'OK, the Tornado is 15 miles astern of you.'. (at this point the burners are lit for the transonic acceleration).. ' he's 14 miles astern of you... 15..16....17...20... you can gues the rest, the F3 gave up in embarassment.
Dude
Quote:
| During the early years of Concorde testing and Airline service I had read it was used as a 'target' for practice interceptions by the RAF. |
Dude
14th Sep 2010, 18:40
permalink Post: 359
Brit312
Speaking of the IAD-Miami sector, was there something 'different' about the subsonic cruise altitude out of Washington? I only ever flew on this sector once,(down the back) but I remember that we did a very rapid transonic acceleration after we crossed the North Carolina coast at Wilmington, from something like FL400, which was only a little above VLA. The air noise over the upper fuselage increased much more rapidely than usual, even charters.
It was an awful long time ago, and if I've screwed up here (again) I heartily apologies .
Regards and salutations..
Dude
Speaking of the IAD-Miami sector, was there something 'different' about the subsonic cruise altitude out of Washington? I only ever flew on this sector once,(down the back) but I remember that we did a very rapid transonic acceleration after we crossed the North Carolina coast at Wilmington, from something like FL400, which was only a little above VLA. The air noise over the upper fuselage increased much more rapidely than usual, even charters.
It was an awful long time ago, and if I've screwed up here (again) I heartily apologies .
Regards and salutations..
Dude
8th Oct 2010, 14:18
permalink Post: 534
Feathers, these are the joys of afterburning; a totally gas guzzling way of extracting some more thrust from an engine. With Concorde, at 15 degrees TAT, you got a 78% increase in take off fuel flow for, as you say, about a 6000lb increase in thrust. Normaly adding an afterburning/reheat system is a fairly complex and heavy affair; you need both the system itself plus a variable exhaust nozzle. Because Concorde already required the primary nozzle for N1 control, the addition of reheat was at least a relatively simple and lightweight afair. The original Olympus 593-22R engine was really a little lacking in terms of dry thrust, and the addition of the reheat system was deemed essential. Concorde only had a single reheat spray ring and flame-holder, military systems often have several, with a corresponding increase in thrust growth as well as a hyper increase in fuel burn.
Further development plans for the Olypus 593 included a large increase in dry thrust; the reheat being retained only for transonic acceleration. It is such a pity that it was not to be.
Dude
Further development plans for the Olypus 593 included a large increase in dry thrust; the reheat being retained only for transonic acceleration. It is such a pity that it was not to be.
Dude
8th Oct 2010, 17:07
permalink Post: 536
Quote:
|
Originally Posted by
M2dude
Further development plans for the Olypus 593 included a large increase in dry thrust; the reheat being retained only for transonic acceleration. It is such a pity that it was not to be.
|
Reheat on the existing aircraft supplied about 25% extra "wet" thrust.
The Olympus 593 "B" engine was going to have about 25% more "dry" thrust, so the reheat could most likely have been deleted altogether.
This was achieved mostly by increasing the diameter of the LP compressor, hence increasing the mass flow, and adding a second LP turbine stage.
The "B" engine was destined for the "B" Concorde which, thanks to several aerodynamic improvements, would have had increased performance and more range, allowing direct flights from Frankfurt and Rome to New York.
Concorde #17 would have been the "prototype" for the "B" model... sadly, as M2dude says, it was not to be.
CJ
24th Oct 2010, 22:18
permalink Post: 602
Concorde Reheat
Consider it done Feathers.
As promised, here are a few diagrams of the Concorde reheat (afterburner, for our American friends) system. The ORIGINAL design was done by SNECMA, but due to them getting into all sorts of trouble with the fuel injection system and flame stabilisation, Rolls Royce baled them out, and it became a Rolls Royce/SNECMA design. (The core engine was a 100% Rolls design, with no French input whatsoever. However some engine sub-assembles were manufactured by SNECMA).
The basic way the afterburner worked was by spraying the fuel FORWARDS intially at high pressure, against the jet stram about one inch, until it hit the anvil. . As the fuel strikes the anvil it is blown back by the jet stram and atomises, passing over the of the spray ring and the over the flame holder. The ignition operated by passing 15KV across a dual cylindrical tube, the resulting arc was 'swirlied' into the fuel stream by blowing engine 5th stage HP compressor air into the tube (there were 7 stages in all).
The key to successful ignition was a healthy spark, a good supply of air to the ignitor and accurate scheduling of fuel flow. (This was scheduled against dry engine flow as a funtion of total temperature). The other important factor (as with any afterburner) was correct and rapid operation of the exhaust nozzle. Fortunately, Concorde used it's primary nozzle for control of engine N1 anyway, so adapting this to operate as an afterburning nozzle also was a relative walk in the park, and it operated superbly.
During the light up phase of 3.5 seconds, the fuel ratio is a fixed 0.45 (ie. reheat fuel is 45% of dry fuel). After the light up phase the full scheduling commenced. As far as the FLIGHT RATING figures go (not take-off) the ratios were 0.6 at a TAT of 54 deg's C, falling linearly to 0.3 at 107 deg's C and above. (Remember that Concorde used afterburning really sparingly, just for take-off and then transonic acceleration; cut off at Mach 1.7 altogether.
Dude
As promised, here are a few diagrams of the Concorde reheat (afterburner, for our American friends) system. The ORIGINAL design was done by SNECMA, but due to them getting into all sorts of trouble with the fuel injection system and flame stabilisation, Rolls Royce baled them out, and it became a Rolls Royce/SNECMA design. (The core engine was a 100% Rolls design, with no French input whatsoever. However some engine sub-assembles were manufactured by SNECMA).
The basic way the afterburner worked was by spraying the fuel FORWARDS intially at high pressure, against the jet stram about one inch, until it hit the anvil. . As the fuel strikes the anvil it is blown back by the jet stram and atomises, passing over the of the spray ring and the over the flame holder. The ignition operated by passing 15KV across a dual cylindrical tube, the resulting arc was 'swirlied' into the fuel stream by blowing engine 5th stage HP compressor air into the tube (there were 7 stages in all).
The key to successful ignition was a healthy spark, a good supply of air to the ignitor and accurate scheduling of fuel flow. (This was scheduled against dry engine flow as a funtion of total temperature). The other important factor (as with any afterburner) was correct and rapid operation of the exhaust nozzle. Fortunately, Concorde used it's primary nozzle for control of engine N1 anyway, so adapting this to operate as an afterburning nozzle also was a relative walk in the park, and it operated superbly.
During the light up phase of 3.5 seconds, the fuel ratio is a fixed 0.45 (ie. reheat fuel is 45% of dry fuel). After the light up phase the full scheduling commenced. As far as the FLIGHT RATING figures go (not take-off) the ratios were 0.6 at a TAT of 54 deg's C, falling linearly to 0.3 at 107 deg's C and above. (Remember that Concorde used afterburning really sparingly, just for take-off and then transonic acceleration; cut off at Mach 1.7 altogether.
Dude
24th Oct 2010, 23:08
permalink Post: 604
Effect on range of single reheat failure to light on T/O
I understand that you could continue the takeoff if one reheat failed to light, but two questions. if you will:
TC
- Typically, would the balky reheat light on the next event requiring additional thrust, the transonic acceleration?
- In the event it did not relight for the transonic climb, what was the impact on range with only three afterburners available for acceleration?
TC
27th Oct 2010, 05:52
permalink Post: 610
Very good photo Feathers. The reheat really was just about the most fragile part of the powerplant, and gave us numerous headaches throughout the service life of the aircraft. The most unreliable part of all was the ignition side of things; the ignition transformer itself being the main culprit here. Also the swirl ignitor itself was rather fragile, as the smallest blockage in the air supply would render the ignitor useless. The failure of the reheat system resulted in the majority of rejected take-offs in the service life of the aircraft. (Failures during transonic acceleration would sometimes respond to a second selection of reheat, but this was often due to spontaneous llight up, due to the much higher total temperatures at Mach 0.95, rather than a recovery of the ignition system itself).
Dude
Dude
27th Oct 2010, 23:05
permalink Post: 617
norodnik
...Did you need all 4 reheats to go from 0.95 - 1.7 ?...
No.
Two reheats were the minimum for transonic acceleration, however due regard would have to paid to the additional fuel usage with one or two reheats failed.
...If you got to 1.3 and then one or more failed could you continue (albeit with slower acceleration ?)...
Yes, as above, whilst remembering the 15 minute time limit on the use of reheat.
...I presume if you were unable to get the things lit at 0.95 you just turned round and went home again ?...
Yes, once you were convinced that at least three were not going to light up.
...The procedure would take around 90 mins so would you need to burn off fuel or already be at acceptable landing weight by that time ?...
Not something I ever had to do, fortunately, but even so, 90 minutes would seem somewhat excessive to me, given that the aircraft would still have been over the Bristol channel. On a transatlantic sector, fuel jettisoning would have been necessary to get down to 130,000 kgs (for a fuel saving landing) or 111,130 kgs (MLW) if the nature of the failure precluded a fuel saving landing.
...once when aboard at about 50K-55K feet the aircraft rolled I would estimate 3 degrees to the left and then came back level again almost immediately...what might have cause such an event (I would guess an airflow issue with intake or engine ?)...
Any number of things could have caused this, but probably the most likely one is the one you suspected, a (transient) intake problem.
Best Regards
Bellerophon
...Did you need all 4 reheats to go from 0.95 - 1.7 ?...
No.
Two reheats were the minimum for transonic acceleration, however due regard would have to paid to the additional fuel usage with one or two reheats failed.
...If you got to 1.3 and then one or more failed could you continue (albeit with slower acceleration ?)...
Yes, as above, whilst remembering the 15 minute time limit on the use of reheat.
...I presume if you were unable to get the things lit at 0.95 you just turned round and went home again ?...
Yes, once you were convinced that at least three were not going to light up.
...The procedure would take around 90 mins so would you need to burn off fuel or already be at acceptable landing weight by that time ?...
Not something I ever had to do, fortunately, but even so, 90 minutes would seem somewhat excessive to me, given that the aircraft would still have been over the Bristol channel. On a transatlantic sector, fuel jettisoning would have been necessary to get down to 130,000 kgs (for a fuel saving landing) or 111,130 kgs (MLW) if the nature of the failure precluded a fuel saving landing.
...once when aboard at about 50K-55K feet the aircraft rolled I would estimate 3 degrees to the left and then came back level again almost immediately...what might have cause such an event (I would guess an airflow issue with intake or engine ?)...
Any number of things could have caused this, but probably the most likely one is the one you suspected, a (transient) intake problem.
Best Regards
Bellerophon
3rd Dec 2010, 12:19
permalink Post: 828
howiehowie93
The whole idea of adapting hotstreak injection came from our Rolls-Royce rep', who spent many years on RB199 development. We'd even identified the position on the Olympus 593 for the injector itself; un unused start atomiser port, but as I reluctantly said before, it was not to be.
Apart from ignition issues the other main problems were reheat instability and reheat 'coming in with a thump', this particular malady being generally confined to transonic acceleration and not take-off.
The instability issue was caused by either an open circuit/high resistance fuel metering valve tacho (only rate feedback was used here) or more commonly contamination of the RFCU umbilical electrical connector. The connector itself was originally located high up the side of the engine, close to the combustion area, was barely accessable and was a total nightmare in terms of reliability. After a great deal of pressure from us (BA) SNECMA agreed to effectively relocate the connector at the bottom of the engine and the majority of our stability problems almost disapperared overnight.
The 'reheat in with a thump issue was a real beaut'. For transonic acceleration a much lower ratio of Fr/Fe (reheat fuel flow/engine fuel flow) was used than for take-off. (0.45 as opposed to 0.78) and therefore the opening rate of the fuel metering valve required damping, this being achieved by using a metered orifice inside the RFCU that applied a small amount of servo fuel pressure to one side of the valve to achieve the damping. Trouble was, any contaminants in the reheat fuel system would progressively clog up the orifice and kill our daming stone dead; the end result being the FMV banging wide open and hence the 'thump'. The only remedy for this problem was to replace the RFCU. SNECMA, in a truly classic feat of engineering produced a filter across this orifice, in order to prevent it getting clogged. Anyone see a problem with this? Yep, the filter itself would clog up and we got our beloved thump back.
The only remedy for this problem was again to replace the
RFCU. The contaminants were often as a result of RFCU build issues; this issue was never truly resolved.
I checked and found the dodgy sustained N1 band for the Olympus 593, this was 88-91% N1. This figure was never an issue in service as at cruise ISA -7 and above conditions the N1 was always run at the flat rate limit of 101.5%. Below ISA -7 the intake system would progressively reduce N1 as a function of intake local Mach Number, falling to 97.4% at ISA -24. (The coldest cruise conditions I personally ever saw was ISA - 25 (that's -81.5 degrees C folks) between BAH and BKK.
The controlled N1 at all other 'non cruise' phases was always in the upper 90's, well away from our blade resonance area.
jodeliste and Alpine Flyer
Thank you both for the TSR-2 information, it makes amazing reading (what a truly magnificent aircraft) , and as Concorde's military cousin, discussion here is in my opinion most waranted.
Regards
Dude
The whole idea of adapting hotstreak injection came from our Rolls-Royce rep', who spent many years on RB199 development. We'd even identified the position on the Olympus 593 for the injector itself; un unused start atomiser port, but as I reluctantly said before, it was not to be.
Apart from ignition issues the other main problems were reheat instability and reheat 'coming in with a thump', this particular malady being generally confined to transonic acceleration and not take-off.
The instability issue was caused by either an open circuit/high resistance fuel metering valve tacho (only rate feedback was used here) or more commonly contamination of the RFCU umbilical electrical connector. The connector itself was originally located high up the side of the engine, close to the combustion area, was barely accessable and was a total nightmare in terms of reliability. After a great deal of pressure from us (BA) SNECMA agreed to effectively relocate the connector at the bottom of the engine and the majority of our stability problems almost disapperared overnight.
The 'reheat in with a thump issue was a real beaut'. For transonic acceleration a much lower ratio of Fr/Fe (reheat fuel flow/engine fuel flow) was used than for take-off. (0.45 as opposed to 0.78) and therefore the opening rate of the fuel metering valve required damping, this being achieved by using a metered orifice inside the RFCU that applied a small amount of servo fuel pressure to one side of the valve to achieve the damping. Trouble was, any contaminants in the reheat fuel system would progressively clog up the orifice and kill our daming stone dead; the end result being the FMV banging wide open and hence the 'thump'. The only remedy for this problem was to replace the RFCU. SNECMA, in a truly classic feat of engineering produced a filter across this orifice, in order to prevent it getting clogged. Anyone see a problem with this? Yep, the filter itself would clog up and we got our beloved thump back.
The only remedy for this problem was again to replace the
RFCU. The contaminants were often as a result of RFCU build issues; this issue was never truly resolved.
I checked and found the dodgy sustained N1 band for the Olympus 593, this was 88-91% N1. This figure was never an issue in service as at cruise ISA -7 and above conditions the N1 was always run at the flat rate limit of 101.5%. Below ISA -7 the intake system would progressively reduce N1 as a function of intake local Mach Number, falling to 97.4% at ISA -24. (The coldest cruise conditions I personally ever saw was ISA - 25 (that's -81.5 degrees C folks) between BAH and BKK.
The controlled N1 at all other 'non cruise' phases was always in the upper 90's, well away from our blade resonance area.
jodeliste and Alpine Flyer
Thank you both for the TSR-2 information, it makes amazing reading (what a truly magnificent aircraft) , and as Concorde's military cousin, discussion here is in my opinion most waranted.
Regards
Dude
8th Apr 2011, 16:29
permalink Post: 1284
For take-off reheat was selected (armed) on all 4 engines together, and certainly not in pairs. (As was stated previously, once 81% N1 was reached the reheat light-up sequence was automatically initiated). You would not wind up on the brakes either, the carbon brakes were extremely sensitive to overtorquing. For transonic acceleration however you are quite right about the 'burners in pairs' bit.
Last edited by Jetdriver; 10th Apr 2011 at 09:23 .