3rd Sep 2010, 20:48
permalink Post: 204
Nick Thomas
... I think am right to assume there were no spoilers...
Correct.
...so on landing did the act of bring the nose down spoil the lift...
Yes, as with most conventional aircraft, reducing the aircraft pitch attitude (once the main wheels were on the runway) would reduce the angle-of-attack and therefore reduce the amount of lift being generated by the wing. Modern aircraft wings are very efficient and will still be generating a considerable amount of lift during the landing roll, even as the aircraft slows down.
Put simply, spoilers and/or lift dump systems are required to destroy this lift, in order to get as much of the aircraft weight as possible on the main landing gear, which, in turn, allows greater pressure to be applied to the wheel brakes before the wheels start to lock-up and the anti-skid units activate to release the applied brake pressure.
Concorde\x92s wing however developed very little lift at zero pitch attitude, so, once you had landed the nose wheel, there was no need for spoilers.
...is that the reason why the non flying pilot pushed the yolk forward once she was down?...
No.
The reason was that using reverse thrust on the ground on Concorde caused a nose-up pitch tendency, strong enough to lift the nose. The procedure was the handling pilot would call Stick Forward as soon as she had landed the nose wheel and the NHP would apply forward pressure on the control column to make sure the nose didn\x92t rise.
If the handling pilot applied reverse thrust before the nose wheel was on the ground, things could get very awkward very quickly.
Firstly, the nose would probably rise, quite possibly beyond the power of the control column to lower it. Secondly, the wing would still be generating (some) lift and so only reduced wheel braking would be available before the anti-skids kicked in, and the amount of runway left would be diminishing faster than normal.
The solution was to reduce to Reverse Idle power until the nose wheel was back on the runway, however, in the heat of the moment it was very easy to go through Reverse Idle and on into Forward Idle. Not only would this again hinder the deceleration of the aircraft, but it would also run the risk of scraping the reverser buckets on the runway (as the buckets moved from the reverse thrust position to the forward thrust position) so tight were the clearances between the buckets and the runway on landing.
Best Regards
Bellerophon
... I think am right to assume there were no spoilers...
Correct.
...so on landing did the act of bring the nose down spoil the lift...
Yes, as with most conventional aircraft, reducing the aircraft pitch attitude (once the main wheels were on the runway) would reduce the angle-of-attack and therefore reduce the amount of lift being generated by the wing. Modern aircraft wings are very efficient and will still be generating a considerable amount of lift during the landing roll, even as the aircraft slows down.
Put simply, spoilers and/or lift dump systems are required to destroy this lift, in order to get as much of the aircraft weight as possible on the main landing gear, which, in turn, allows greater pressure to be applied to the wheel brakes before the wheels start to lock-up and the anti-skid units activate to release the applied brake pressure.
Concorde\x92s wing however developed very little lift at zero pitch attitude, so, once you had landed the nose wheel, there was no need for spoilers.
...is that the reason why the non flying pilot pushed the yolk forward once she was down?...
No.
The reason was that using reverse thrust on the ground on Concorde caused a nose-up pitch tendency, strong enough to lift the nose. The procedure was the handling pilot would call Stick Forward as soon as she had landed the nose wheel and the NHP would apply forward pressure on the control column to make sure the nose didn\x92t rise.
If the handling pilot applied reverse thrust before the nose wheel was on the ground, things could get very awkward very quickly.
Firstly, the nose would probably rise, quite possibly beyond the power of the control column to lower it. Secondly, the wing would still be generating (some) lift and so only reduced wheel braking would be available before the anti-skids kicked in, and the amount of runway left would be diminishing faster than normal.
The solution was to reduce to Reverse Idle power until the nose wheel was back on the runway, however, in the heat of the moment it was very easy to go through Reverse Idle and on into Forward Idle. Not only would this again hinder the deceleration of the aircraft, but it would also run the risk of scraping the reverser buckets on the runway (as the buckets moved from the reverse thrust position to the forward thrust position) so tight were the clearances between the buckets and the runway on landing.
Best Regards
Bellerophon
5th Sep 2010, 02:29
permalink Post: 215
It was certificated - up to a point. Problematic? Maybe not, but it was a part of the flt envelope to be treated with respect.
Obviously there are no spoilers, and once you translate to 'vortex lift' (stalled in conventional terms) there is definitely no shortage of drag. (This happened at about 250kts at landing weight).
Supersonic - it was certainly no sailplane and an ability to increase drag wasn't required.
So - there is a bit of the flight envelope where you are subsonic, descending at about 350kts IAS, where you may need a bit of drag; e.g. to make the FL140 limit on the OCK 1A SID (as it then was) to LHR.
To facilitate this, engines 2 and 3 could be selected to reverse idle within certain strict limitations (most of which have now left my brain). The mechanism was to ask the SFE to arm the system on his panel and then to select reverse on the inboards. Where the system was slightly unreliable was that you were running the air-driven buckets with the engines at idle thrust - consequently they sometimes didn't make a full reverse selection, in which case you canx reverse on that engine and managed on one.
Clearly the big event would be if they didn't translate into fwd thrust, which is one of the reasons it wasn't done below 10 000'. I'm not aware of this happening.
To be honest it was only really used when ATC threw an alt constraint at you during the descent, because in general if you just pitched down to 380kts (Vmo when subsonic at typical approach weights) you would get the height off comfortably.
Obviously there are no spoilers, and once you translate to 'vortex lift' (stalled in conventional terms) there is definitely no shortage of drag. (This happened at about 250kts at landing weight).
Supersonic - it was certainly no sailplane and an ability to increase drag wasn't required.
So - there is a bit of the flight envelope where you are subsonic, descending at about 350kts IAS, where you may need a bit of drag; e.g. to make the FL140 limit on the OCK 1A SID (as it then was) to LHR.
To facilitate this, engines 2 and 3 could be selected to reverse idle within certain strict limitations (most of which have now left my brain). The mechanism was to ask the SFE to arm the system on his panel and then to select reverse on the inboards. Where the system was slightly unreliable was that you were running the air-driven buckets with the engines at idle thrust - consequently they sometimes didn't make a full reverse selection, in which case you canx reverse on that engine and managed on one.
Clearly the big event would be if they didn't translate into fwd thrust, which is one of the reasons it wasn't done below 10 000'. I'm not aware of this happening.
To be honest it was only really used when ATC threw an alt constraint at you during the descent, because in general if you just pitched down to 380kts (Vmo when subsonic at typical approach weights) you would get the height off comfortably.
5th Sep 2010, 02:37
permalink Post: 216
Question for engineering types:
I remember being told in my conversion course that the motors driving the secondary nozzles (buckets) were the fastest rotating devices on the aircraft. Is it true? Have you got a number for it? Was it really more than the gyro in the stby horizon?
If anyone has seen the video of AF landing at BZZ after the first post-grounding test flight, you may have noticed that you can hear the buckets translating to reverse even over the noise of the blustery wind and four Olympus 593's at idle.
I remember being told in my conversion course that the motors driving the secondary nozzles (buckets) were the fastest rotating devices on the aircraft. Is it true? Have you got a number for it? Was it really more than the gyro in the stby horizon?
If anyone has seen the video of AF landing at BZZ after the first post-grounding test flight, you may have noticed that you can hear the buckets translating to reverse even over the noise of the blustery wind and four Olympus 593's at idle.
5th Sep 2010, 11:56
permalink Post: 217
In-Flight Reverse (A case of Bucket and See)
Capt Chambo
Concorde was, as EXWOK says, could use reverse in flight, on the inboard engines only, and only as far as reverse idle, the mechanism of which was quite complex and did on occasion not do work as advertised. Bear in mind here that the Rolls Royce Olympus 593 was a pure turbojet with no bypass, and so a hot stream reverser only had to be used; the reverser buckets acting directly on the efflux as it did any reverser in the 'old' days. Also the same buckets that were used for reverse were also progressively opened up between Mach 0.55 and wide open at Mach 1.1, this giving a vital control enhancement to the divergencing efflux. The overall effect of this was to give a true overall convergent/divergent nozzle assembly, the ideal for any supersonic aircraft.
As far as inflight reverse goes, the amount of HP compressor delivery air (P3) required to actuate the bucket airmotor in flight at an idle thrust settings, was quite minimal to say the least, and some help was definitely needed here. The moment that inflight reverse was selected (on the inboard engines only remember) the OUTBOARD engines would have their idle N2 automatically increased, and some of THEIR P3 air supply was also automatically ported over (via an isolation valve) to the inboard buckets. This whole process was required in order to give a little added muscle to the bucket airmotors, and give the system a fighting chance. Even this however was still not quite enough, the inboard travelling buckets required minimal air loading on their surface, and so the primary nozzles for the affected engines (the primary nozzle lived just aft of the LP turbine, aft of the reheat assembly) was automatically signalled wide open in order to assist matters here, by reducing gas velocity. One the buckets had reached full reverse the primary nozzle was then signalled full close (this applied for normal ground reverse also) and the automatic increased idle on the outboard engines was cancelled. To enable the described process to occur, provided all four engines were at idle, a solenoid latched button on the F/E's station could be selected. This signalled a circuit that enabled the selection of idle reverse on the inboard engines only, the opening of the P3 isolation valve, the raising of the outboard engine's idle and maximum primary nozzle angle for the outboards as soon as reverse was then selected..
The whole system was just a little fragile here; failure of either the extra air supply, or the raised idle on the 'other' engine was usually enough to stop the process working correctly.
EXWOK
While flying 'up front' I only ever experienced the use of inflight reverse once. (The captain was a bit of an Animal, if you flying guys see what I mean
). I would not say that it felt as if we'd hit a brick wall, as I'd expected the sensation to feel, more like we were flying into the dumped contents of a very large manure truck
. The whole operation was so slick, we'd dumped the required amount of IAS more or less within a second or two, and normal thrust was immediately selected. As so often happened with you guys, you made it look too easy.
As far as the speed of the airmotor goes, I seem to remember that it was something in the order of 80,000 RPM at max chat; as you say faster (around twice as fast) as the standby horizon motor.
The basic core airmotor (not the whole assembly) was the same Garrett unit used on the P&W JT9 as well as the RB-211.
Dude
Concorde was, as EXWOK says, could use reverse in flight, on the inboard engines only, and only as far as reverse idle, the mechanism of which was quite complex and did on occasion not do work as advertised. Bear in mind here that the Rolls Royce Olympus 593 was a pure turbojet with no bypass, and so a hot stream reverser only had to be used; the reverser buckets acting directly on the efflux as it did any reverser in the 'old' days. Also the same buckets that were used for reverse were also progressively opened up between Mach 0.55 and wide open at Mach 1.1, this giving a vital control enhancement to the divergencing efflux. The overall effect of this was to give a true overall convergent/divergent nozzle assembly, the ideal for any supersonic aircraft.
As far as inflight reverse goes, the amount of HP compressor delivery air (P3) required to actuate the bucket airmotor in flight at an idle thrust settings, was quite minimal to say the least, and some help was definitely needed here. The moment that inflight reverse was selected (on the inboard engines only remember) the OUTBOARD engines would have their idle N2 automatically increased, and some of THEIR P3 air supply was also automatically ported over (via an isolation valve) to the inboard buckets. This whole process was required in order to give a little added muscle to the bucket airmotors, and give the system a fighting chance. Even this however was still not quite enough, the inboard travelling buckets required minimal air loading on their surface, and so the primary nozzles for the affected engines (the primary nozzle lived just aft of the LP turbine, aft of the reheat assembly) was automatically signalled wide open in order to assist matters here, by reducing gas velocity. One the buckets had reached full reverse the primary nozzle was then signalled full close (this applied for normal ground reverse also) and the automatic increased idle on the outboard engines was cancelled. To enable the described process to occur, provided all four engines were at idle, a solenoid latched button on the F/E's station could be selected. This signalled a circuit that enabled the selection of idle reverse on the inboard engines only, the opening of the P3 isolation valve, the raising of the outboard engine's idle and maximum primary nozzle angle for the outboards as soon as reverse was then selected..
The whole system was just a little fragile here; failure of either the extra air supply, or the raised idle on the 'other' engine was usually enough to stop the process working correctly.
EXWOK
While flying 'up front' I only ever experienced the use of inflight reverse once. (The captain was a bit of an Animal, if you flying guys see what I mean
). I would not say that it felt as if we'd hit a brick wall, as I'd expected the sensation to feel, more like we were flying into the dumped contents of a very large manure truck
. The whole operation was so slick, we'd dumped the required amount of IAS more or less within a second or two, and normal thrust was immediately selected. As so often happened with you guys, you made it look too easy.
As far as the speed of the airmotor goes, I seem to remember that it was something in the order of 80,000 RPM at max chat; as you say faster (around twice as fast) as the standby horizon motor.
The basic core airmotor (not the whole assembly) was the same Garrett unit used on the P&W JT9 as well as the RB-211.
Dude
Last edited by M2dude; 5th Sep 2010 at 13:25 .
6th Sep 2010, 14:14
permalink Post: 227
This thread deserves an award...
I'm not a professional pilot, just a humble owner of a PPL with a very strong interest in aviation and a long time reader here (esp. in the Tech Log board). I've never posted here, because I prefer to read and learn from those who know it better, but this thread has finally managed to lure me out of lurking mode
Like in this video?
YouTube - Concorde late 32 landing at Leeds/Bradford Airport
There is a strange high pitch sound that kicks in for about a second in the same moment the nose wheel makes contact with the ground and before the actual reverse thrust sound can be heard.
Thanks to all for sharing all this information about one of the most fascinating machines ever created by human mankind.
I'm not a professional pilot, just a humble owner of a PPL with a very strong interest in aviation and a long time reader here (esp. in the Tech Log board). I've never posted here, because I prefer to read and learn from those who know it better, but this thread has finally managed to lure me out of lurking mode
Quote:
| If anyone has seen the video of AF landing at BZZ after the first post-grounding test flight, you may have noticed that you can hear the buckets translating to reverse even over the noise of the blustery wind and four Olympus 593's at idle. |
YouTube - Concorde late 32 landing at Leeds/Bradford Airport
There is a strange high pitch sound that kicks in for about a second in the same moment the nose wheel makes contact with the ground and before the actual reverse thrust sound can be heard.
Thanks to all for sharing all this information about one of the most fascinating machines ever created by human mankind.
7th Sep 2010, 08:39
permalink Post: 250
I hope this one is interesting; it's a Rolls Royce diagram illustrating what the wildly varying differences were in terms of the engine between take off and supersonic cruise. The primary nozzle can be seen at the rear of the engine, together with the reheat assembly and the secondary nozzle (reverser buckets).
Yes ChristaanJ, I FINALLY managed to upload stuff here.
Yes ChristaanJ, I FINALLY managed to upload stuff here.
8th Sep 2010, 14:04
permalink Post: 279
Quote:
|
Originally Posted by
AC Busted
My question, if I may?
|
Quote:
| I noticed a tail skid in many videos. Did Concorde ever have a need for it? |
Only the first three Concordes (001, 002 and 01) had a real tail skid (coated with hardwood, IIRC, to prvent sparks).
From aircraft 02 onwards, the skid was replaced by two small wheels, that look as if they've come off a Spitfire....
To understand why it's there, look at a drawing of a side view of Concorde.
If a Concorde overrotates at take-off, or lands with the nose too high, the first things that would have touched the ground are the exhaust nozzles / thrust reverser buckets. The tail skid/wheels are there to prevent that.
As to the need for it...
"Tailstrikes" were rare, but they did happen.
Now I don't remember offhand whether it was already mentioned here or somewhere else, but more often than not those tail wheels were not much good, and got shoved back into the tail, with the reverser buckets still hitting the ground : there are photos of repairs to the buckets to prove it !
CJ
8th Sep 2010, 15:22
permalink Post: 280
..........which was one reason it was so important to touch down with the wings level - even a very small angle of bank could result in bucket contact as they translated to the reverse position. It was a surprise coming to Concorde to find it was even more restrictive than the 747 in this respect.
7th Oct 2010, 04:02
permalink Post: 522
Oshkosh 1994
One very long winded piece of personal nostalgia, I hope you\x92ll all bear with me:
In 1994 a Concorde (can\x92t remember the registration) flew out to Oshkosh Wisconsin (OKS) for the bi-annual EAA fly in. The aircraft was scheduled to fly from LHR to YYZ via MAN, where it would pick up 100 charter passengers in Manchester for a five day holiday in Toronto. The aircraft would then fly empty from YYZ to Oshkosh for the five day air show, before returning to YYZ to bring home the passengers to MAN. At Manchester another 100 charter passengers were then carried subsonically back to London. While the aircraft was in Canada and the US, it would be looked after by two American BA engineers who were based at JFK. At least that was the plan, but the best laid plans of mice and men\x85.
The aircraft was catered for the MAN-YYZ sector in London, and flew up to Manchester with just the three flight deck crew but no cabin crew (no passengers, so no need). At Manchester there would be a change of crew, plus a full complement of cabin crew for the on-going sector to Toronto (Plus of course 100 passengers). This is where things started to go rather wrong; when the aircraft landed at Manchester one of the bar trolleys , which had not been correctly secured by the catering twits, broke loose and flew through the open flight deck door (pre-911 the door was usually always open anyway). The trolley hit the back of the E/O\x92s chair and subsequently damaged a couple of fuel transfer switches on his panel. You can imagine what the three crew thought; they were just landing the aircraft when a high speed trolley decides to join them on the flight deck in an extremely noisy and spectacular entrance. (The language went something like \x91what the ***** was that!!). The two switches, although damaged still operated normally, and so the crew taking the aircraft to YYZ decided to accept the aircraft with just a couple of ADDs for the broken but still funtional switches.
So the aircraft, plus FOUR flight crew (an extra crew member, a captain in this case, was taken along to do the PR over the PA, as was usual on charter operations). Everything seemed to be going smoothly, or so it seemed, when there was a warning that the number 2 secondary nozzle \x91buckets\x92 had travelled towards reverse (the blue transit light was flashing) although the indicator on the E/O\x92s panel still apparently showed the nozzle at the correct zero degree position for supersonic flight. As always (at least with BA!!) the correct drill was applied, and a precautionary engine shut down was carried out. This now meant that the aircraft would have to decelerate to subsonic speed, and as a consequence would not be able to reach YYZ safely, and so a technical diversion to YQX (Gander NFLD) was carried out, the aircraft and passengers having an unscheduled night stop there. (This eating into the first night of the passengers stay in Toronto). The two JFK engineers who had been waiting patiently in YYZ had to quickly jump on a Lear Jet to Gander, and on arrival there got on the phone to London, that\x92s where I come in. The nozzle itself had not run away at all, it was merely an indication problem, but we all decided that the best course of action for now was to have the secondary nozzle physically locked at the intermediate position of 10 degrees as a performance ADD. This would still allow supersonic operation (although from YQX to YYZ there would be precious little of that), but with a fuel penalty of at least 1.5 tonnes per supersonic sector, plus of course no reverser operation on that engine. I still had concerns about the aircraft being able to return on the YYZ to MAN sector with a bucket locked out, but at least the passengers could now start their delayed holiday in Toronto, and the aircraft could happily fly on to the wilds of Wisconsin.
Every day during the EAA fly in, Concorde would do some charter flying, and the JFK guys would be on the phone every day letting us know how things were going. It seemed now that the secondary nozzle defect had \x91cleared up\x92 on it\x92s own, and the guys had decided to reinstate the secondary nozzle air motor to its normal position. We were all very apprehensive about this, and started to think about what the possible cause of the original defect was and maybe see about provisioning a spare part if necessary. On the final day of the EAA event, the aircraft was taxying out when another warning light for the number 2 bucket illuminated. The aircraft returned to the ramp where the JFK engineers again locked out the air motor at 10 degrees before leaving on its charter. We had discussions over the phone as to what the symptoms were, and it looked like the culprit was the switch pack that lived underneath the bucket assembly. I spent several hours getting spare parts shipped via MAINTROL to YYZ, the idea being that the bits could be flown out to Toronto on the next scheduled subsonic flight. It was generally agreed that the aircraft could not fly the YYZ-MAN sector with a bucket locked out due to performance considerations and so a fix was essential. (The spare parts included by the way the two switches that had been broken on the first landing into Manchester).
I was at the airport until quite late that night making sure that from the information that we\x92d been given the correct course of action had been chosen, and I only got about four hours of sleep before I had to head back to Heathrow the following morning. I had a feeling that I\x92d be possibly be asked to fly out to Toronto (the JFK guys requested this also) , so I took my passport, a change of clothes etc. with me just in case. Sure enough before I knew it I was on the 10:30 BA001 Concorde to JFK, a Limo taking me immediately across town from JFK to La Guardia. From there I was put on an Air Canada A320 to Toronto, arriving there at about 14:30 local time. (19:30 \x91my\x92 time, I was knackered already). When I got to our Concorde the JFK guys told me that the bits I\x92d sent the previous evening were stuck in Canadian Customs, and it took another hour or so to get our hands on them. We proceeded to get her \x91fixed up\x92 between us, and by about 20:00 local we were serviceable. I phoned the crew at the hotel, telling them of the good news, and was told that as soon as I\x92d checked in and had a shower, we were all going out to dinner (my body clock was now at 02:00). Now the flight crew and cabin crew are well [FONT='Calibri','sans-serif']acclimatised, having been in Canada and the States for FIVE days, but I am now a total wreck, (more so than usual), and w hen I finally got to bed it was around midnight Toronto time (05:00 London time). Now no one (including me) expected to see me for the 07:30 pick up from the hotel in the morning, but somehow I miraculously made it. Because one passenger had gone home to Manchester early, there was a seat available for me on the aircraft (I\x92d expected to have had to fly home subsonic, due to the only other available seat being the flip down flight deck aisle seat; to have sat there for over four hours would have been less than pleasant). So all I now wanted to do was get on the aircraft, collapse into my seat and SLEEP, but I had to wait until all passengers had boarded before I was allocated my seat; 26B right at the back of the aircraft. So here I go, getting onto the aircraft in what I thought was total anonymity when as I get on board the purser in the fwd. galley announces that \x91this is Mr Dude who flew out yesterday from London especially to make sure we don\x92t have to divert again\x92. I just wanted to die as I have to walk the gauntlet of 99 passengers all clapping and cheering all the way to the back of the aircraft, my face as red as a beetroot, and when I finally get to my seat I find that I am sat next to this really lovely elderly lady who wanted a blow by blow account of what had gone on, as well as a running commentary on the flight itself. (Of course alll I wanted to do was sleep, I was totally exhausted, but this old lady was absolutely delightful). About an hour after take-off one of the stewardesses informs me that the crew want me up front urgently, so here I go again walking the length of the cabin up to the flight deck. As I go in the guys said \x91I thought you\x92d fixed the *** ing thing.\x92 \x91I did\x92 replies yours truly, and I took a look at the flight deck panels and everything is normal. The four guys are killing themselves laughing, \x91fooled you\x92 , the flight engineer chirps up with (everything was fine, the joke was on me yet again). I once more stagger back to my seat, and for the rest of the flight I keep my lady passenger friend entertained with Concorde stories all the way back to Manchester. At Manchester there is another few hours wait before we FINALLY fly back down to Heathrow, with yet another load of passengers and I finally go home to bed. In all of my Concorde years I\x92d had many exhausting episodes, but Toronto \x9294 really took the biscuit.
Dude
In 1994 a Concorde (can\x92t remember the registration) flew out to Oshkosh Wisconsin (OKS) for the bi-annual EAA fly in. The aircraft was scheduled to fly from LHR to YYZ via MAN, where it would pick up 100 charter passengers in Manchester for a five day holiday in Toronto. The aircraft would then fly empty from YYZ to Oshkosh for the five day air show, before returning to YYZ to bring home the passengers to MAN. At Manchester another 100 charter passengers were then carried subsonically back to London. While the aircraft was in Canada and the US, it would be looked after by two American BA engineers who were based at JFK. At least that was the plan, but the best laid plans of mice and men\x85.
The aircraft was catered for the MAN-YYZ sector in London, and flew up to Manchester with just the three flight deck crew but no cabin crew (no passengers, so no need). At Manchester there would be a change of crew, plus a full complement of cabin crew for the on-going sector to Toronto (Plus of course 100 passengers). This is where things started to go rather wrong; when the aircraft landed at Manchester one of the bar trolleys , which had not been correctly secured by the catering twits, broke loose and flew through the open flight deck door (pre-911 the door was usually always open anyway). The trolley hit the back of the E/O\x92s chair and subsequently damaged a couple of fuel transfer switches on his panel. You can imagine what the three crew thought; they were just landing the aircraft when a high speed trolley decides to join them on the flight deck in an extremely noisy and spectacular entrance. (The language went something like \x91what the ***** was that!!). The two switches, although damaged still operated normally, and so the crew taking the aircraft to YYZ decided to accept the aircraft with just a couple of ADDs for the broken but still funtional switches.
So the aircraft, plus FOUR flight crew (an extra crew member, a captain in this case, was taken along to do the PR over the PA, as was usual on charter operations). Everything seemed to be going smoothly, or so it seemed, when there was a warning that the number 2 secondary nozzle \x91buckets\x92 had travelled towards reverse (the blue transit light was flashing) although the indicator on the E/O\x92s panel still apparently showed the nozzle at the correct zero degree position for supersonic flight. As always (at least with BA!!) the correct drill was applied, and a precautionary engine shut down was carried out. This now meant that the aircraft would have to decelerate to subsonic speed, and as a consequence would not be able to reach YYZ safely, and so a technical diversion to YQX (Gander NFLD) was carried out, the aircraft and passengers having an unscheduled night stop there. (This eating into the first night of the passengers stay in Toronto). The two JFK engineers who had been waiting patiently in YYZ had to quickly jump on a Lear Jet to Gander, and on arrival there got on the phone to London, that\x92s where I come in. The nozzle itself had not run away at all, it was merely an indication problem, but we all decided that the best course of action for now was to have the secondary nozzle physically locked at the intermediate position of 10 degrees as a performance ADD. This would still allow supersonic operation (although from YQX to YYZ there would be precious little of that), but with a fuel penalty of at least 1.5 tonnes per supersonic sector, plus of course no reverser operation on that engine. I still had concerns about the aircraft being able to return on the YYZ to MAN sector with a bucket locked out, but at least the passengers could now start their delayed holiday in Toronto, and the aircraft could happily fly on to the wilds of Wisconsin.
Every day during the EAA fly in, Concorde would do some charter flying, and the JFK guys would be on the phone every day letting us know how things were going. It seemed now that the secondary nozzle defect had \x91cleared up\x92 on it\x92s own, and the guys had decided to reinstate the secondary nozzle air motor to its normal position. We were all very apprehensive about this, and started to think about what the possible cause of the original defect was and maybe see about provisioning a spare part if necessary. On the final day of the EAA event, the aircraft was taxying out when another warning light for the number 2 bucket illuminated. The aircraft returned to the ramp where the JFK engineers again locked out the air motor at 10 degrees before leaving on its charter. We had discussions over the phone as to what the symptoms were, and it looked like the culprit was the switch pack that lived underneath the bucket assembly. I spent several hours getting spare parts shipped via MAINTROL to YYZ, the idea being that the bits could be flown out to Toronto on the next scheduled subsonic flight. It was generally agreed that the aircraft could not fly the YYZ-MAN sector with a bucket locked out due to performance considerations and so a fix was essential. (The spare parts included by the way the two switches that had been broken on the first landing into Manchester).
I was at the airport until quite late that night making sure that from the information that we\x92d been given the correct course of action had been chosen, and I only got about four hours of sleep before I had to head back to Heathrow the following morning. I had a feeling that I\x92d be possibly be asked to fly out to Toronto (the JFK guys requested this also) , so I took my passport, a change of clothes etc. with me just in case. Sure enough before I knew it I was on the 10:30 BA001 Concorde to JFK, a Limo taking me immediately across town from JFK to La Guardia. From there I was put on an Air Canada A320 to Toronto, arriving there at about 14:30 local time. (19:30 \x91my\x92 time, I was knackered already). When I got to our Concorde the JFK guys told me that the bits I\x92d sent the previous evening were stuck in Canadian Customs, and it took another hour or so to get our hands on them. We proceeded to get her \x91fixed up\x92 between us, and by about 20:00 local we were serviceable. I phoned the crew at the hotel, telling them of the good news, and was told that as soon as I\x92d checked in and had a shower, we were all going out to dinner (my body clock was now at 02:00). Now the flight crew and cabin crew are well [FONT='Calibri','sans-serif']acclimatised, having been in Canada and the States for FIVE days, but I am now a total wreck, (more so than usual), and w hen I finally got to bed it was around midnight Toronto time (05:00 London time). Now no one (including me) expected to see me for the 07:30 pick up from the hotel in the morning, but somehow I miraculously made it. Because one passenger had gone home to Manchester early, there was a seat available for me on the aircraft (I\x92d expected to have had to fly home subsonic, due to the only other available seat being the flip down flight deck aisle seat; to have sat there for over four hours would have been less than pleasant). So all I now wanted to do was get on the aircraft, collapse into my seat and SLEEP, but I had to wait until all passengers had boarded before I was allocated my seat; 26B right at the back of the aircraft. So here I go, getting onto the aircraft in what I thought was total anonymity when as I get on board the purser in the fwd. galley announces that \x91this is Mr Dude who flew out yesterday from London especially to make sure we don\x92t have to divert again\x92. I just wanted to die as I have to walk the gauntlet of 99 passengers all clapping and cheering all the way to the back of the aircraft, my face as red as a beetroot, and when I finally get to my seat I find that I am sat next to this really lovely elderly lady who wanted a blow by blow account of what had gone on, as well as a running commentary on the flight itself. (Of course alll I wanted to do was sleep, I was totally exhausted, but this old lady was absolutely delightful). About an hour after take-off one of the stewardesses informs me that the crew want me up front urgently, so here I go again walking the length of the cabin up to the flight deck. As I go in the guys said \x91I thought you\x92d fixed the *** ing thing.\x92 \x91I did\x92 replies yours truly, and I took a look at the flight deck panels and everything is normal. The four guys are killing themselves laughing, \x91fooled you\x92 , the flight engineer chirps up with (everything was fine, the joke was on me yet again). I once more stagger back to my seat, and for the rest of the flight I keep my lady passenger friend entertained with Concorde stories all the way back to Manchester. At Manchester there is another few hours wait before we FINALLY fly back down to Heathrow, with yet another load of passengers and I finally go home to bed. In all of my Concorde years I\x92d had many exhausting episodes, but Toronto \x9294 really took the biscuit.
Dude
Last edited by M2dude; 7th Oct 2010 at 22:00 .
8th Oct 2010, 09:06
permalink Post: 528
Feathers McGraw
The 10 degree lockout position was a bit of a compromise, to allow the aircraft to operate throughout the normal operating envelope with a secondary nozzle (bucket) at a less than ideal position. See the diagrams below, one showing the bucket control schedule and the other the bucket positions at both take off and supersonic flight: If the buckets are too wide at low Mach numbers then the high velocity exhaust will try and 'drag' the low pressure/low velocity air in the exhaust annulus along with it; this results in a huge reduction in thrust and is termed 'base drag'. That is the whole idea of having the eyelids at the top and bottom of the bucket assembly; to admit free ambient air into this void and mitigate the effects of base drag (and reduce the noise mayhem a little too). If however the buckets are too narrow at high speed/high altitude then we really get a problem; The high pressure/high velocity exhause gas immediately expands against the VERY low presuure ambient air and flares outwards at an accute angle, again losing us serious quantities of thrust The wide open bucket angle gives us this wonderful cushion of secondary intake airflow. (travelling over the top of the rear ramp, through the engine bay and into the nozzle annulus. The eflux can now gently expand against this airflow as it exits the secondary nozzle, taking up the shape of the divergent secion of nozzle.
Now if we are locked at the 10 degree position we are at a position that will give us significant but tolerable losses throughout the flight envelope.
Quote:
| I presume that the fuel penalty for a locked secondary nozzle was due to the reduced expansion of exhaust gas without the maximum divergent shape? |
Now if we are locked at the 10 degree position we are at a position that will give us significant but tolerable losses throughout the flight envelope.
8th Oct 2010, 14:22
permalink Post: 535
I heard that the combined nozzle and reverser was a unique piece of aviation development.
The story I heard when I was an apprentice at Hurn was that, compared to the prototype multi finger nozzle and separate reverser, the production nozzle was:-
1. More efficient.
2. Lighter.
3. Simpler.
4. Cheaper to make and maintain.
I doubt there have been many developments that meet all 4 items.
Usually the first three can be met, but at great cost.
P.S. I did my bit of Concorde design in the FSDO by re-drawing a cabin bulkhead to reduce weight.
The story I heard when I was an apprentice at Hurn was that, compared to the prototype multi finger nozzle and separate reverser, the production nozzle was:-
1. More efficient.
2. Lighter.
3. Simpler.
4. Cheaper to make and maintain.
I doubt there have been many developments that meet all 4 items.
Usually the first three can be met, but at great cost.
P.S. I did my bit of Concorde design in the FSDO by re-drawing a cabin bulkhead to reduce weight.
9th Oct 2010, 19:10
permalink Post: 539
Dixi188
Actually Rolls Royce always told me that the (new) Type 28 secondary nozzle was a bit of a dissapointment. Aerodynamically it was a far better interface with the wing from a drag point of view than the original design, but fell short of it's design promise in terms of performance. The design responsibility for the secondary nozzle system awarded to the French engine manufacturer SNECMA. They in turn farmed the whole manufacturing side off to STRESSKIN inc., a division of General Motors, and the air motor and electronic control unit were designed and built by Garret Airesearch in the US also.
The original secondary nozzle was 'freely floating, with no actuation; the thrust revereser itself was a pair of cascade doors, driven by an air motor. Tertary air doors opened at low speeds to admit ambient air into the nozzle anulus, instead of the eyelids of the later 'buckets'.
If you look at the diagram below you can see what a complicated animal the prototype powerplant was. The intake dump door (alternative name for spill door) was hinged both at the front AND the rear; either hinge mechanisms automatically releasing at specific Mach numbers. It was the mechanical nightmare that the diagram suggesrs.
Dude
Quote:
|
I heard that the combined nozzle and reverser was a unique piece of aviation development.
The story I heard when I was an apprentice at Hurn was that, compared to the prototype multi finger nozzle and separate reverser, the production nozzle was:- 1. More efficient. 2. Lighter. 3. Simpler. 4. Cheaper to make and maintain. |
The original secondary nozzle was 'freely floating, with no actuation; the thrust revereser itself was a pair of cascade doors, driven by an air motor. Tertary air doors opened at low speeds to admit ambient air into the nozzle anulus, instead of the eyelids of the later 'buckets'.
If you look at the diagram below you can see what a complicated animal the prototype powerplant was. The intake dump door (alternative name for spill door) was hinged both at the front AND the rear; either hinge mechanisms automatically releasing at specific Mach numbers. It was the mechanical nightmare that the diagram suggesrs.
Dude
Last edited by M2dude; 9th Oct 2010 at 21:54 .
20th Oct 2010, 10:21
permalink Post: 593
The green 'Go' configuration light depends on the following flowchart:
Ess 28v DC Busbar -> Fwd Thrust Selected -> Arming Switch 'On' -> Landing Gear Relay Operated -> Fuel Flow Attained -> Jet Pipe Pressure (P7) Attained -> Bucket Position Correct -> 'GO'.
How were these engine parameters monitored? (From the AMM)
- Arming Switch 'ON' : it's a manually operated four-pole solenoid-held switch, for the four engine circuits, operative only when a landing gear weight switch is energized.
- Fuel Flow and Jet Pipe Pressure (P7) Attained: Once the circuit to the 'Go' light is armed, the flow and pressure are monitored against the values set on the indicator bugs on the respective instruments. Once they pass those values, their respective change-over relays are energized, completing the circuit.
Here's a simplified schematic for this:
At least I think that's how it works
.
Lefteris
Ess 28v DC Busbar -> Fwd Thrust Selected -> Arming Switch 'On' -> Landing Gear Relay Operated -> Fuel Flow Attained -> Jet Pipe Pressure (P7) Attained -> Bucket Position Correct -> 'GO'.
How were these engine parameters monitored? (From the AMM)
- Arming Switch 'ON' : it's a manually operated four-pole solenoid-held switch, for the four engine circuits, operative only when a landing gear weight switch is energized.
- Fuel Flow and Jet Pipe Pressure (P7) Attained: Once the circuit to the 'Go' light is armed, the flow and pressure are monitored against the values set on the indicator bugs on the respective instruments. Once they pass those values, their respective change-over relays are energized, completing the circuit.
Here's a simplified schematic for this:
At least I think that's how it works
.
Lefteris
20th Oct 2010, 10:56
permalink Post: 594
Quote:
| What engine parameters were monitored to provide this indication and how was this done ? |
BLUE reverse light --- this reflected the correct operation of the
reverse thrust.
Flashing, rev selected but buckets in transit
On steady reverse selected and achieved
Amber Configuration
[CON] light----------- ON if reheat fails with no loss of engine RPM
On if reverse selected and primary nozzle greater
than 15%
Green Go light---------- This light monitored the engine for correct power
for take-off in that
Fuel flow and P7 had to match or exceed a pre
calculated figures, which were preset on their
individual gauges prior to take off.
The secondary nozzles had to within their
take-off limits
The CON light is off
In the case of No 4 engine the N1 limiter has
returned to normal position
Now normally there was a call of 100kts and at that point there had to be 4 green GO lights illuminated otherwise the t/off would be aborted. There was a concession to this in that if runway/ conditions /weight allowed the takeoff could continue with only 3 green lights illuminated at 100 kts as long as the
affected basic engine was OK[ this covered the loss of one reheat]
The green lights were considered necessary if the aircraft was using a rough runway and nose nodding could interfer with correct engine instruement monitoring and were also handy as the pilots could at a glance check whether they had at least minimum eng power for t/off.
To keep things simply their use was standard on all T/offs rough or otherwise
22nd Oct 2010, 09:26
permalink Post: 597
Ze Concorde Quiz Mk 2 (Or is it Mach 2?).... Ze Answers
OK guys, here are the answers. If you disagree about any of them then fire away, the old memory certainly 'aint perfect.
As many of you have guessed, there were 22: The 14 production airframes, the 2 production series development aircraft (201 & 202), the 2 pre-production airframes (101 & 102) and the 2 prototypes 001 & 002. PLUS, the major fatigue test specimen at the RAE Farnborough and the static test specimen at CEAT in Toulouse. The CEAT tests actually tested the wing to destruction; I seem to remember it was something like a 200% overload before the wing failed at the root. And great but rather sad pictures
VOLUME
, never seen these before.
OK, from MY memory
, we have: London LHR (duhhh!!), Bahrein BAH, Singapore SIN, New York JFK, Washington IAD, Dallas DFW, Miami MIA, Toronto YYZ, Barbados BGI, and Riyadh RUH. As well as charters being ommited, so are some of the special 'surprise' shuttle appearances that Concorde would make, substituting a subsonic to and from destinations such as Manchester and Edinburgh.
11:15
The BA193 and BA 195.
OK, there were 12 engine feed pumps (3 per engine) 8 main transfer tank pumps (2 each for the transfer tanks 5, 6, 7 & 8), 4 'A' tank pumps (2 each for 5A & 7A), 8 trim-transfer tank pumps (2 electric pumps each for tanks 9, 10 & 11 PLUS 2 hydraulically driven pumps for tank 9), 4 electric engine start pumps (there was a single electric start pump per engine that delivered fuel to it's own dedicated start atomiser in the combustion chamber. The pump automatically ran when the engine HP valve was set to OPEN and would continue running for 30 seconds after the DEBOW switch was returned to the 'normal' position), 4 engine first stage pumps (a single mechanically driven pump per engine), 4 second stage pumps (a single pneumatically driven pump, sometimes termed 'the turbopump, per engine. This would cut out at around 20,000'), our scavenge tank pump (triggered automatically when there was 7 US gallons in the tank; pumping it back into tank 2. This pump was identical to an 'A' tank transfer pump), and FINALLY, a single de-air pump for tank 10. The pump would drive the fuel through a mesh, removing air bubbles from the fuel. Tank 11 used the L/H trim pump for de-air (similar principle)and would be switched on during take-off. This is why the tank 5 trim inlet valve being set to over-ride OPEN would result in the tank being highly pressurised in the case of the Gonesse disaster; the pump would obviously pressurise the L/H trim gallery and any tank on that side with an open inlet valve!!!
G-AXDN, aircraft 101. (A production wing, fuselage, droop nose and intakes, but with the short tail section and secondary nozzles of the prototypes.
Ready ChristiaanJ? There were 18....Yes, the single SFENA standby horizon, 9 INS gyros (one per X,Y and Z platform in each of the 3 INUs), 8 autostab' rate gyros (one per axis for each of the 2 autostab' computers PLUS a monitor gyro for the pitch axis). The radar by the way used attitude signals from the INS.
9. One per main wheel plus the single 'in flight braking' nose wheel brake.
Mach 0.7!!! Between this and Mach 1.26 the intake surfaces were positioned as a function of engine N1 if the engine was shut down for any reason. (Otherwise of course the intake surfaces were fully up). You needed a sub idle N1 of 57% and below for all this to happen, and it was to assist relight performance and reduce buffet. Between Mach 1.26 and 1.32 the ramps were driven down slightly to about 5%, full supersonic scheduling itself commencing at Mach 1.32.
Already brilliantly answered by Brit312 (as well as the FSLabs diagram). Yep, Geen GO, T/O monitor armed, fuel flow and P7 at or above datum, A/C on ground, reverse not selected and CON light not on. Amber CON (Reheat selected and not detected, N1 OK or reverse selected and primary nozzle (Aj) not at minimum. Blue REV; steady buckets at reverse, flashing buckets in transit.
Fairford, followed by Brize Norton, and then a host of airfields from Prestwick and Shannon to Chateauroux.
OK, probably no surprises now:
Landing - 27L & R, 9L & R (prior to LHR mag' deviation update were 28L & R & 10L & R) together with 23/05.
Take off - 27L (28L), 9R (10R) and 9L. (10L never happened as take offs on this runway only occurred in 2003).
It was FedEx, they planned to operate two stripped out aircraft, leased from BA, between Shannon and JFK as high value parcel carriers. The idea was that parcels would be flown in from all over Europe by small FedEx feeder aircraft and the parcels transferred to Concorde which would then speed on to JFK in around 2 1/2 hours. It never happened because of a combination of economics appraisal by FedEx and BA deciding that it could would not release the aircraft anyway.
A/C 101, G-AXDN first flew on 17th December 1971 with FIXED INTAKES!! (101 was going to be the launch vehicle for the new digital intake control system, but the 'boxes' were still being designed). This placed an operating limit of Mach 1.5 on the aircraft, limiting her ability with such a restricted flight envelope. She returned to Filton in late 1972 for installation of the system, as well as the new Olympus 593-602 engine. (The engine, very similar to the production Mk 610 version, used a quite revolutionary annular combustion chamber, and eliminated at a stroke the thick smoke exhaust that had up to then been Concorde's unwanted visual signiture). The aircraft flew more or less smokeless on 15 March 1973, achieving Mach 2 soon afterwards. As ChristiaanJ pointed out, the British prototype 002 had a similar gap, actually significantly higher, of 19 months. (The French aircraft 001 had an even longer gap of some 20 months).
I hope you guys had fun with this one, regards to all
Dude
Quote:
| 1) How many Concorde airframes were built? |
Quote:
| 2) As far as the British constructed aircraft went, name the destinations that were served?. Regular flight numbers only, excludes charters etc. |
, we have: London LHR (duhhh!!), Bahrein BAH, Singapore SIN, New York JFK, Washington IAD, Dallas DFW, Miami MIA, Toronto YYZ, Barbados BGI, and Riyadh RUH. As well as charters being ommited, so are some of the special 'surprise' shuttle appearances that Concorde would make, substituting a subsonic to and from destinations such as Manchester and Edinburgh.
Quote:
| 3) What was the departure time for the ORIGINAL morning LHR-JFK Concorde services? (Not called the BA001 then either). |
Quote:
| 4) Further to question 3 above, what WERE the original flight numbers for the BA001 and BA003? (The morning and evening LHR-JFK services?). |
Quote:
5) There were no less than FORTY SIX fuel pumps on Concorde. What was the breakdown for these? (Clue; don't forget the scavenge pump
).
|
Quote:
| 6) What was the only development airframe to have a TOTALLY unique shape? |
Quote:
| 7) This one is particularly aimed at ChristiaanJ. What was the total number of gyros on the aircraft? |
Quote:
| 8) How many wheel brakes? |
Quote:
| 9) What Mach number was automatic engine variable intake control enabled? |
Quote:
| 10) Above each bank of engine instruments were three lights, a blue, a green and an amber. What did they each signify? |
Quote:
| 11) At what airfield were the first BA crew base training details held? |
Quote:
| 12) What LHR runways did Concorde use for landing and take-off? (Trick question, not as obvious as it might seem). |
Landing - 27L & R, 9L & R (prior to LHR mag' deviation update were 28L & R & 10L & R) together with 23/05.
Take off - 27L (28L), 9R (10R) and 9L. (10L never happened as take offs on this runway only occurred in 2003).
Quote:
| 13) What operator had serious plans to operate Concorde from SNN to JFK in the early 1980's? |
Quote:
| 14) What development aircraft did not exceed Mach 2 until fifteen months after her maiden flight? |
I hope you guys had fun with this one, regards to all
Dude
Last edited by M2dude; 22nd Oct 2010 at 11:21 . Reason: oops, misssed out question 2
1st Nov 2010, 05:45
permalink Post: 649
NW1
I agree that my wording regarding precautionary engine shut-down was not quite correct my friend
; with WW3 going on out there under the wing I think we can both agree that that check list ddi not in any shape or form cover the events ensuing.
And as for the AM/CF dynamic duo; I could not agree more; these two wankers/toss-pots/cretins etc (being a gentleman forbids me from printing here my real thoughts on these veritable slime buckets) I would not place them in charge of a broken down manure truck.
. One had the avowed aim of destroying Concorde and the other, in a position to do some good did his master's bidding and was party in no small way to this madness. Pity 'skippy' did not have some balls too!!
Best Regards
Dude
I agree that my wording regarding precautionary engine shut-down was not quite correct my friend
; with WW3 going on out there under the wing I think we can both agree that that check list ddi not in any shape or form cover the events ensuing.
And as for the AM/CF dynamic duo; I could not agree more; these two wankers/toss-pots/cretins etc (being a gentleman forbids me from printing here my real thoughts on these veritable slime buckets) I would not place them in charge of a broken down manure truck.
. One had the avowed aim of destroying Concorde and the other, in a position to do some good did his master's bidding and was party in no small way to this madness. Pity 'skippy' did not have some balls too!!
Best Regards
Dude
Last edited by M2dude; 1st Nov 2010 at 09:34 .
7th Nov 2010, 01:34
permalink Post: 674
Oh darn it Feathers, if you insist (LOL).
First of all, what is rotating stall? All gas turbine engines are prone to this to some degree or another, the Olympus was particularly prone (so we discovered to our cost). What happens is that extremely LOW figures of N2, small cells of stalled air rotate around the anulus of the early stages of the HP compressor (at approximately half the rotational rpm), resulting in parts of the airflow becoming choked and highly distorted. This often results in the combustion process being disturbed to the extent that combustion instead of occuring in the combustion chamber, occurs in the turbine itself. This of course results in massive overheating of the turbine blades and stators (and is what is suspected occured in the #2 engine on G-BOAA in 1991.
To prevent running in rotating stall, the Olympus automatic fuel start schedule would accelerate the engine quickly to around 67% N2 before dropping back to the normal idle figure of around 65% N2. (The stall clearance N2 figure was ambient temperature dependant, the higher the temperature the higher the N2 that was required and hence scheduled by the automatics).
What had happened on G-BOAA was an engine starting/accelerating problem, where the N2 ran at a sub-idle of around 40% N2 for several minutes. This was enough for the malignant effects of rotating stall to take hold, and the resulting turbine blade failure over the Atlantic the following day. In all fairness to everyone involved, none of us, including Rolls Royce realised just how potentially serious this phenonomen was, and salutary lessons were learned by one and all. (The following year Air France had a similar failure; their first and last also).
I flew out to Shannon on a BAC 1-11, that was sent to fly the Concorde passengers back to London. As I and my colleague were coming down the ventral door steps of the 1-11, a chirpy Aer Lingus engineer asks 'have you guys come to fix the broken engine?, there are bits of it lying in the jet pipe'. Now up to now, from the information we'd been given in London, we thought that we were going to be looking at either an intake or engine induced surge, a few systems checks and boroscope inspections and we'd all be on our way, so we naturally thought the Aer Lingus guy was joking. He was most certainly was not; as you looked into the jetpipe (through the secondary nozzle buckets) you could see a large quantity of metal debris, accompanied by a strong smell of burnt oil. I remember this day well, it was the day that the first Gulf war ended; how ironic.
The aircraft departed on three engines, flown by a management crew late the following day, my colleague and I returned to London by Aer Lingus one day later. (No passengers whatsoever are permitted on ferry flights, even expendable ones like me).
Dude
First of all, what is rotating stall? All gas turbine engines are prone to this to some degree or another, the Olympus was particularly prone (so we discovered to our cost). What happens is that extremely LOW figures of N2, small cells of stalled air rotate around the anulus of the early stages of the HP compressor (at approximately half the rotational rpm), resulting in parts of the airflow becoming choked and highly distorted. This often results in the combustion process being disturbed to the extent that combustion instead of occuring in the combustion chamber, occurs in the turbine itself. This of course results in massive overheating of the turbine blades and stators (and is what is suspected occured in the #2 engine on G-BOAA in 1991.
To prevent running in rotating stall, the Olympus automatic fuel start schedule would accelerate the engine quickly to around 67% N2 before dropping back to the normal idle figure of around 65% N2. (The stall clearance N2 figure was ambient temperature dependant, the higher the temperature the higher the N2 that was required and hence scheduled by the automatics).
What had happened on G-BOAA was an engine starting/accelerating problem, where the N2 ran at a sub-idle of around 40% N2 for several minutes. This was enough for the malignant effects of rotating stall to take hold, and the resulting turbine blade failure over the Atlantic the following day. In all fairness to everyone involved, none of us, including Rolls Royce realised just how potentially serious this phenonomen was, and salutary lessons were learned by one and all. (The following year Air France had a similar failure; their first and last also).
I flew out to Shannon on a BAC 1-11, that was sent to fly the Concorde passengers back to London. As I and my colleague were coming down the ventral door steps of the 1-11, a chirpy Aer Lingus engineer asks 'have you guys come to fix the broken engine?, there are bits of it lying in the jet pipe'. Now up to now, from the information we'd been given in London, we thought that we were going to be looking at either an intake or engine induced surge, a few systems checks and boroscope inspections and we'd all be on our way, so we naturally thought the Aer Lingus guy was joking. He was most certainly was not; as you looked into the jetpipe (through the secondary nozzle buckets) you could see a large quantity of metal debris, accompanied by a strong smell of burnt oil. I remember this day well, it was the day that the first Gulf war ended; how ironic.
The aircraft departed on three engines, flown by a management crew late the following day, my colleague and I returned to London by Aer Lingus one day later. (No passengers whatsoever are permitted on ferry flights, even expendable ones like me).
Dude
19th Nov 2010, 22:00
permalink Post: 742
Mr Vortex
Not quite; remember that the N1s and N2s in the E SCHEDULE graph are non-dimentional. ie. they vary with temperature. As the temperature rises (with increasing Mach Number) the scheduled spool speeds increase. What really happens (I did not explain it correctly first time) is that the much lower N1 demanded by the use of E LOW at high speed results in a much further closed primary nozzle than normal, pushing up TET (and EGT) and we run hard into the EGT limiter, which claws fuel flow off, to the extent that the ramps and spill doors come down to their preset limits, almost as if there is a flame-out. The net result is a huge reduction in thrust. The condi was formed as the primary nozzle naturally took up a near fully open position in supersonic cruise and the wide open secondary nozzle buckets completed the picture. The schedule used here was E HIGH. I've noticed a couple of errors on the graph, the main one being that E HIGH is used with reheat off but with Vc
>
220 KIAS
Apart from being set as a variable limit, EGT normally played no role in the control loops (there were 2 loops, the 'governor' and 'positioner' loops). P7 played no part whatsoever in any case, the main variables were; N2, throttle valve position, throttle transmitter position, T1, total pressure and static temperature..
Feathers McGraw
Oh nooooo... I've been outed
Best regards
Dude
Quote:
|
So if we select E Low at M>1.7 the N2 will ovespeed and hence higher fuelflow. Am I understand it right? Also, what E mode provide the
best config shape [lest sat suitable] that provide a con-di nozzle for maximize thrust. [Not open to wide that exhaust can't reach M1 at the throat of Prim nozzle]. |
Quote:
| And another quesrion here, the engine control unit use which parameter to control the thrsut. The EGT, or N2, or P7. |
Feathers McGraw
Quote:
| If you watch some of the more recent Concorde programmes, such as "Concorde's Last Flight", you'll hear and see the reaction of the various people (including our very own Dude) from the BA side of things as they talk about their charge. |
Best regards
Dude
Last edited by M2dude; 20th Nov 2010 at 05:10 .
29th Nov 2010, 21:39
permalink Post: 816
touch and goes
Notfred -
There was no real difference between a touch and go and a normal take off/landing. As already stated earlier in the thread bucket contact was always a possibility if the landing was a little high-pitched, especially while the buckets translated. Not having the wings perfectly level reduced bucket clearance significantly. Not much of an issue on take-off.
As for checking runways - there was a lot of that done for this aeroplane, but nowt to do with clearances. Runway roughness was a potential issue on take-off, it was to do with the structural dynamics. No time to explain now, though, but I'll revisit it tomorrow if no-one else does.
In short - bucket contact would be the result of mishandling of some sort (e.g. incorrect Vref, speed decay, overflare, wings not level) not runway roughness.
There was no real difference between a touch and go and a normal take off/landing. As already stated earlier in the thread bucket contact was always a possibility if the landing was a little high-pitched, especially while the buckets translated. Not having the wings perfectly level reduced bucket clearance significantly. Not much of an issue on take-off.
As for checking runways - there was a lot of that done for this aeroplane, but nowt to do with clearances. Runway roughness was a potential issue on take-off, it was to do with the structural dynamics. No time to explain now, though, but I'll revisit it tomorrow if no-one else does.
In short - bucket contact would be the result of mishandling of some sort (e.g. incorrect Vref, speed decay, overflare, wings not level) not runway roughness.
27th Dec 2010, 14:04
permalink Post: 1026
A pot pourri of responses after my Christmas reading!
This actually is interesting in that the n umbers show one of the fundamental features that made the Ol 593 such a good choice. If you look closely at the TO and cruise values you will find that at TO the overall compressor pressure ratio is 13.5 the compressor exit temperature 460 degC and the turbine inlet temperaure is 1152 degC. In cruise the pressure ratio is 10.5, the compressor exit is 565 degC and the TET 1100 degC.
Somebody, I can't find the exact post, was asking whether the elevated cruise total temperatures affected engine life, and here we see why this is so. As Christian said in another posting, when you compress air it gets hotter - from 21 degC to 460 degC at take off and from 127 degC to 565 degC in cruise. A fundamental limit on engine operation is the turbine entry temperature. Not only does it affect the maximum TO thrust you can get but also the continued exposure to cruise TETs has a very big effect on engine fatigue life, and engine manufacturers have shown extremes of ingenuity when developing new materials and ways of cooling the blades to increase allowable TET.
The problem with supersonic operations is that you start from an elevated intake delivery temperature so that when the flow exits the compressor it is already very hot 565 instead of 460 to be exact. But the maximum temperature one can stand for fatigue reasons is limited, therefore the amount of fuel you can pour in must be limited also, and the thrust you can develop per pound of airflow is roughly proportional to the fuel input/temperature rise. To get any sensible cruise thrust then one must squeeze the cruise TET as high as you dare for fatigue reasons but also you need to keep the compression ratio down so that the temperature going into the combustion chambers is as low as you can get away with. This tend to drive engines designed for extended supersonic operations to having a low pressure ratio. This is against the trend in subsonic operations where compression ratios have been steadily increasing along with bypass ratios.
The net result then is that the engine must be designed with a low OPR and must operate with cruise TET much closer to its TO TET value than would be necessary, or indeed desirable, on a subsonic design.
Actually, here, as on some other apparent carry-overs, one should look at the equipment supplier rather than the aircraft manufacturer to trace continuity. Here we have Messier supplying Concorde's gear and Dowty (OK they are now part of Messier) supplying the A330. And having worked on both, I seem to remember that the means of doing the shortening are quite different.
Yes, they both came out of the Bristol drawing office. One minor anecdote: the 'ramshorn' stick was a novelty to the Concorde flight test crews but they got to like it, or at least put up with it. All went well until it came to the time when Dave Davies, the ARB Chief Test Pilot, came to put his rubber stamp on the aircraft.
Concorde's seats, just like those on your car, could be moved back and fore to get your legs on the pedals and up and down so you could see over the bonnet (sorry, instrument panel). The control column of course stayed in one place, so the relationship of the 'horns' to ones thighs varied with ones height. Andre Turcat was about 6ft 2in, Trubbie and the others of average height. The smallest regular pilot was Jean Franchi at, I suppose, about 5ft 7 or 5ft 8. No problems. But Dave Davies was short like me and he found that he could not get full back stick and full aileron because the ramshorn fouled his thighs.
Consternation! Completely unacceptable! I don't know what arguments they used to convince him it was all OK really, but it got through certification. I would certainly be interested to learn from the pilots in this group as to whether it was ever a problem.
I can't resist this one!. Has anyone ever noticed/wondered about the tiny bit of the outer elevon that has been chopped off? That was my first real input into the design as a young erk looking at variability of touchdown conditions and coming to the conclusion that if the pilot got into trouble and was trying to pick up a trailing wing with too much AoA as well then he was likely to hit the ground with the downgoing elevon. I persuaded my boss that this was so and we made a small adjustment.
In self defence I am going to plead that this was well before the days of the Type 28 nozzle, so the issue of buckets contacting the ground first never came up!
To the point where an American Airline maintainance engineer, watching a prototype taking off and with full benefit of being located strategically for maximum sideline noise, remarked on what he described as 'visible acoustic radiation'
On another occasion, it was reputed that Stanley Hooker, watching a TO in the company of HRH the Duke of Edinburgh, remarked that "You know Sir that that noise represents less energy than it takes to boil an egg". to which he got the reply "Then I must congratulate you Sir Stanley, on producing so much noise for the expenditure of so little energy".
There was an effect and in consequence the aircraft performance brochures were formally calculated for north/south flight. Pity really, it would sometimes have been nice to be able to fly guarantee performance demonstrations in the most favourable direction
That's enough for today!
CliveL
Quote:
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Originally Posted by
M2Dude
I hope this one is interesting; it's a Rolls Royce diagram illustrating what the wildly varying differences were in terms of the engine between take off and supersonic cruise. The primary nozzle can be seen at the rear of the engine, together with the reheat assembly and the secondary nozzle (reverser buckets).
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This actually is interesting in that the n umbers show one of the fundamental features that made the Ol 593 such a good choice. If you look closely at the TO and cruise values you will find that at TO the overall compressor pressure ratio is 13.5 the compressor exit temperature 460 degC and the turbine inlet temperaure is 1152 degC. In cruise the pressure ratio is 10.5, the compressor exit is 565 degC and the TET 1100 degC.
Somebody, I can't find the exact post, was asking whether the elevated cruise total temperatures affected engine life, and here we see why this is so. As Christian said in another posting, when you compress air it gets hotter - from 21 degC to 460 degC at take off and from 127 degC to 565 degC in cruise. A fundamental limit on engine operation is the turbine entry temperature. Not only does it affect the maximum TO thrust you can get but also the continued exposure to cruise TETs has a very big effect on engine fatigue life, and engine manufacturers have shown extremes of ingenuity when developing new materials and ways of cooling the blades to increase allowable TET.
The problem with supersonic operations is that you start from an elevated intake delivery temperature so that when the flow exits the compressor it is already very hot 565 instead of 460 to be exact. But the maximum temperature one can stand for fatigue reasons is limited, therefore the amount of fuel you can pour in must be limited also, and the thrust you can develop per pound of airflow is roughly proportional to the fuel input/temperature rise. To get any sensible cruise thrust then one must squeeze the cruise TET as high as you dare for fatigue reasons but also you need to keep the compression ratio down so that the temperature going into the combustion chambers is as low as you can get away with. This tend to drive engines designed for extended supersonic operations to having a low pressure ratio. This is against the trend in subsonic operations where compression ratios have been steadily increasing along with bypass ratios.
The net result then is that the engine must be designed with a low OPR and must operate with cruise TET much closer to its TO TET value than would be necessary, or indeed desirable, on a subsonic design.
Quote:
|
I
s this another item that Airbus used for the A330/340? I can't remember the exact arrangement for Concorde, but the 330 uses a clever lever arrangement at the top of the leg.
I was not even aware of this A33/340 similarity, sounds yet another case of Airbus using Concorde technology. (Immitation still is the greatest form of flattery I guess). As far as I am aware Concorde had none of the lubrication issues that you describe. M2Dude |
Actually, here, as on some other apparent carry-overs, one should look at the equipment supplier rather than the aircraft manufacturer to trace continuity. Here we have Messier supplying Concorde's gear and Dowty (OK they are now part of Messier) supplying the A330. And having worked on both, I seem to remember that the means of doing the shortening are quite different.
Quote:
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Originally Posted by
Brit312
The Britannia and now you are talking about the love of my life and yes I do remember the story of the nose and visor selector, but we have forgotten the most obvious. Where do you think they got the idea for the control column from
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Yes, they both came out of the Bristol drawing office. One minor anecdote: the 'ramshorn' stick was a novelty to the Concorde flight test crews but they got to like it, or at least put up with it. All went well until it came to the time when Dave Davies, the ARB Chief Test Pilot, came to put his rubber stamp on the aircraft.
Concorde's seats, just like those on your car, could be moved back and fore to get your legs on the pedals and up and down so you could see over the bonnet (sorry, instrument panel). The control column of course stayed in one place, so the relationship of the 'horns' to ones thighs varied with ones height. Andre Turcat was about 6ft 2in, Trubbie and the others of average height. The smallest regular pilot was Jean Franchi at, I suppose, about 5ft 7 or 5ft 8. No problems. But Dave Davies was short like me and he found that he could not get full back stick and full aileron because the ramshorn fouled his thighs.
Consternation! Completely unacceptable! I don't know what arguments they used to convince him it was all OK really, but it got through certification. I would certainly be interested to learn from the pilots in this group as to whether it was ever a problem.
Quote:
|
Originally Posted by
exWok
........which was one reason it was so important to touch down with the wings level - even a very small angle of bank could result in bucket contact as they translated to the reverse position. It was a surprise coming to Concorde to find it was even more restrictive than the 747 in this respect
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I can't resist this one!. Has anyone ever noticed/wondered about the tiny bit of the outer elevon that has been chopped off? That was my first real input into the design as a young erk looking at variability of touchdown conditions and coming to the conclusion that if the pilot got into trouble and was trying to pick up a trailing wing with too much AoA as well then he was likely to hit the ground with the downgoing elevon. I persuaded my boss that this was so and we made a small adjustment.
In self defence I am going to plead that this was well before the days of the Type 28 nozzle, so the issue of buckets contacting the ground first never came up!
Quote:
| As far as your point about the prototype engines; they were way down on thrust anyway, (even without the 'help' of the silencers), produced more black smoke than a 1930's coal fired power station. |
To the point where an American Airline maintainance engineer, watching a prototype taking off and with full benefit of being located strategically for maximum sideline noise, remarked on what he described as 'visible acoustic radiation'
On another occasion, it was reputed that Stanley Hooker, watching a TO in the company of HRH the Duke of Edinburgh, remarked that "You know Sir that that noise represents less energy than it takes to boil an egg". to which he got the reply "Then I must congratulate you Sir Stanley, on producing so much noise for the expenditure of so little energy".
Quote:
|
Originally Posted by
CJ
One example : in theory the aircraft did weigh 1.2 % less, so the lift was 1.2 % less and the drag was 1.2 % less, so the fuel consumption was less too, so did Concorde have another 50-odd miles range thrown in 'free' by flying higher and faster than it's low-down subsonic brethren?
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There was an effect and in consequence the aircraft performance brochures were formally calculated for north/south flight. Pity really, it would sometimes have been nice to be able to fly guarantee performance demonstrations in the most favourable direction
That's enough for today!
CliveL