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NW1
September 20, 2010, 15:18:00 GMT permalink Post: 5945693 |
Interesting & nostalgic thread. Nice to see this monumental aviation achievement still generates such passion...
In case it's of interest (and suitable health warning as the memory fades)... The heat did evaporate water vapour in the airframe - reducing corrosion. I remember when the 5 BA aircraft were returned to service, after the post-accident mods, their weight and balance certificates were prepared and found to be out by (IIRC) more than a tonne. This represented water in the airframe present after a year on the ground, and was gone again after a couple hours of supercruise on return to service. Back to the weighbridge for new W&B Certificates.... Vortex lift caused buffet which felt very similar to a conventional wing's stall/low speed buffet. At landing weights (I hate the trend of using the term "mass": weight is a force, mass is not!) you felt the buffet start as you reduced speed (CAS: Vc) to about 250kts. It was handy as a reminder that you should select visor down / nose to five below 250kts (the recommendation was as you slowed through 270kts, but latterly we were in the habit of holding at 250kts nose/visor up - I think TCAS was quoted as a backup to the more limited visibility in that config). At takeoff weights, the buffet went at more like 270kts accelerating. So I'm pretty sure there was no vortex lift at AoA > 7 degrees (250kts at LW). Recommended subsonic cruise at MTOW was F260 / M0.95 which was equal to Vmo of 400kts (CAS). It was best cruise because Vc=400kts was also min drag at MTOW. F280 meant a slightly more draggy speed of 384kts, but some preferred it because when cleared to climb & accelerate supersonic (the official expression was "go for it") it gave you a bit of slack against Vmo when eng put the reheats in. But we tended to ignore the overspeed warning anyway: it was supposed to go really really fast... We never flew with visor down and nose up unless it was bust - that config was only used during pushback (except one captain who always thought it looked better visor up....). Visor down max Vc was 325kts/M0.8 so it would limit subsonic cruise, and besides it made a racket like that. It was a beaut in x-winds - a total lack of yaw-roll couple meant you just straightened the 'plane up with rudder and carried on into the flare as normal. No roll to counteract, and the sideways "lift" created by the rudder deflection on the fin pretty much equalled the x-wind drift. Nice. Wind limits were Crosswind 30kts (15kts contaminated or autoland), Headwind for autoland 25kts (or manual "reduced noise" approach: that's a technical way we used to reduce the noise footprint down to 800' by flying at 190kts then reducing to a target speed of Vref+7kts at that point). Tailwind 10kts. All these limits were, of course, subject to "on the day" performance limits calculated at the time. I seem to remember there was an over-arching limit of 6000' on r/w length, subject again to "on the day" performance limits. OK, I cheated on this paragraph and dug out FM Vol 2a. There were loads of other limitations which were, by and large, more "esoteric" than a conventional airliner and which had to be learned for the conversion course. It really made the head hurt, and would have been impossible without a big loverrly picture of the beast on the wall chucking out yellow smoke and making noise. Even a static picture of her seemed to make noise... No one who flew it could really believe their luck, but one thing for sure is "they don't build them like that any more"... Ahhhhhhhhhhhhhh.......... Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Afterburner/Re-heat AoA Auto-land British Airways Captains Conversion Course Corrosion Rudder Super-cruise Visor Vmo Vortex |
NW1
September 20, 2010, 20:45:00 GMT permalink Post: 5946368 |
<<A senior royal gentleman to the skipper on leaving the aircraft,"Wonderful flight, thank you. And if the company want to know where the undercarriage is, it's up my a**e.">>
Same thing happened on the 757 fleet. And the Trident. Possibly the Britannia too - probably ![]() Subjects: None |
NW1
September 20, 2010, 22:48:00 GMT permalink Post: 5946584 |
Nick - good question. The elevons were not hidden at high AoA (no elevators, no T-tail issue) but high alpha longitudinal stability was an issue in early development, one of the fixes were the moustache strakes you see at the front - they help energise the wing vorteces and improve rudder authority at high AoA. Apparently. Well that's what they told us at ground school - the result was that right up to limiting AoA all flight controls were effective, including the potentially blanked-off rudder. IIRC the stick-shake was at about 16 degrees which left about 3 degrees slack above approach AoA and it all worked just fine in that environment.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): AoA Elevons Rudder |
NW1
September 21, 2010, 09:34:00 GMT permalink Post: 5947237 |
Nick - the only thing I can remember about cabin seats is that the a/c was certified to carry (I think) 125 passengers. But with JFK departures often load-limited as they were, I think 100 was a sensible decision. Some clever arrangements meant it looked bigger and airier than it was. Most passenger feedback seemed to indicate the cabin layout was good enough - not First Class, but then you only had to sit there for 3.5 hours...
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): JFK LHR-JFK Route |
NW1
September 29, 2010, 13:30:00 GMT permalink Post: 5963828 |
A memory which really stuck re. hand flying supersonic was how solid it felt - and how the extreme TAS (about 1200kts) vividly demonstrated the relationship between TAS / angle of bank and turn rate: you rolled on 15 degrees of bank and it seemed like the HSI heading reference had stuck - it just didn't turn. From memory turn radius with 30 degrees AOB at M2 was about 50nms...
Re the autostabs: it felt like the puppet's strings were cut with them off, but switching to Mechanical Signalling as well made it truly horrible. I only ever flew the sim in this config, I understood they used to do it at base but stopped it because they feared lives would be lost. A pal once memorably described it as like trying to fly a dustbin lid around. And so it was! Plug it all back in (Electrical Signalling and Autostabs) and it all snapped back into shape beautifully. So ahead of its time... There were no doubt pitch trim changes transonic due to the mach trim system, but a more obvious effect in the 0.99-1.3 range was due to shockwaves forming and fading assymetrically causing minor oscillations in all axes: if you watched out front while hand flying the accel or decel you could make out the nose descibing what felt like figures of eight as the trim changed in pitch and yaw. Roll too, and gentle pressure was required on the cc to avoid overcontrolling and PIO - a bigger problem with the Conc than some other types... Memory lane - this is fun! Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Auto-stabilisation Hand Flying Mach Trim Shockwave TAS (True Air Speed) |
NW1
October 25, 2010, 02:15:00 GMT permalink Post: 6015726 |
100kts
E/O calls "Power set" if you have a minimum of 4 engines and 3 reheats (for a "goer" - your flippy thing set to "3"!) else "Engine Fail" and therefore an RTO. 4-engines and 4-reheats (4 greens) needed at 100kts for a "power set" call for a "stopper" - flippy thing at "4". It was simply how far off TOW was from PLTOW and a concept introduced following a commercially unacceptable number of RTOs which weren't necessary from a perf-A POV... (A single reheat failure, although rare, could be accepted after 100kts at any weight) (Just noticed Brit312 covered this earlier - sorry!) Last edited by NW1; 25th October 2010 at 02:29 . Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Afterburner/Re-heat |
NW1
October 31, 2010, 15:31:00 GMT permalink Post: 6029488 |
M2Dude & Brit312:
FWIW the LP Cock to shutoff was added to the precautionary engine shutdown C/L - but I think this was after (and because of) the AF inceident. But I had understood that their engine failure that day had been due to a problem with the engine which caused enough vibration to damage the fuel pipe leading to the leak. I don't know if they ran the Fire / Severe Damage C/L, but that C/L always involved shutting the LP Cock as part of the Cleanup Items. Maybe they did "only" run the Precautionary Shutdown C/L - I have no idea, but the LP Cock position (which turned out to be key to the near loss of the a/c) would depend on it prior to the addition of that step in that latter drill. I do remember there was always controversy in training circles about the Cleanup Items and when or where (or even "IF"?) they should be run: but IF the AF flight had run the Fire / Severe Damage drill and IF they had run the Cleanup Items soon afterwards, then their situation would not have been so dire. No critisism of anyone intended (AF crew or forum posters), it's all such a long time ago now, but the nuances involved in Precautionary Shutdown / Fire - Severe Damage / Cleanup Drills were far from clear-cut... Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Air France Engine Failure Engine Shutdown |
NW1
October 31, 2010, 23:01:00 GMT permalink Post: 6030290 |
Sorry M2Dude, but although I agree that the reasons for the premature withdrawal from service lay south of La Manche, the AF incident we're talking about was not due to "forgetting to select the LP cock to shutoff" in your quote
<<What was required in the case of this failure was a precautionary engine shut-down, closing off the fuel supply to the engine totally, and a descent/deceleration to subsonic speed, carefully monitoring fuel consumption all the time. Unfortunately the crew 'forgot' to shut down the fuel LP valve>> At that time the Precautionary Engine Shutdown C/L did not call for the LP cock to be selected to shutoff (that stable door was subsequently closed). So no procedural errors there. You could argue that the severe vibration which kicked off the incident should have called for the Engine Fire / Severe Damage C/L in which case the Cleanup C/L would have seen the LP Cock closed - but when? And was this the drill called? IF the Precautionary Shutdown drill was used then it is not surprising that the LP cock was not closed. That's all. Easy when looked at through a retrospectoscope.... And for what it's worth I think AM and CF were a pair of [edited to say: "allegedly not supportive of the Concorde operation"] who should not have been allowed any authority at all over this precious project.... Last edited by NW1; 1st November 2010 at 09:02 . Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Air France Engine Shutdown |
NW1
November 06, 2010, 16:19:00 GMT permalink Post: 6043691 |
Concorde had a very advanced HUD fitted. It was a spring-loaded wire frame (a bue transparent plastic thing on 'OAG) which you could flip up in front of you to help judge the landing attitude. With final attitude about 11 degrees and secondary nozzles scraping the runway at (from memory) about 12.5 degrees attitude control was key.
Three-engined ferrys were approved. Went through it on the sim, and this is only from memory but you set full re-heated power on the symmetric pair, and the assymmetric engine at 75kts. "Power Set" was called slightly later than normal (130kts). Any re-heat failure before V1 = RTO. There were loads of complex additional issues to go through at planning (the 3-engine ferry manual wasn't the thickest on the fleet - but it was thick enough!) and I don't think I'd have been too keen on doing one (I was never asked, and I don't know of any Concorde having done it - more "seasoned" fleet members may know better!): I think it was a slighly more critical proposition even than doing it on a blunty, and most guys I know have reservations about it on their fleets too... Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Afterburner/Re-heat HUD (Head Up Display) Nozzles V1 |
NW1
November 20, 2010, 16:04:00 GMT permalink Post: 6074244 |
We've heard from Engineers, Pilots, Designers, 'Ambassadors'.... How about ATC??? Are there any out there with their memories?? Was life slightly different when "No Speed Restriction" was offered and Concorde hit 400 kts+ instead of the mere mortals at +/- 300 kts?? Anything unusual in their handling on the way into LHR/JFK/IAD/BGI etc for sequencing?? Any general anecdotes to recollect??
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Air France JFK |
NW1
December 20, 2010, 23:13:00 GMT permalink Post: 6134593 |
Why the switches for climb and cruise ratings. What was being accomplished that modulation of the throttles couldn't
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Afterburner/Re-heat Noise Abatement |
NW1
December 22, 2010, 16:01:00 GMT permalink Post: 6137867 |
VOR tracking on Conc
You're right Christiaan - memories of the exact details are growing misty now, but I do remember trying to get the autoflight VOR tracking facility to work and not getting anything sensible. I (and everyone else I ever flew with) invariably used the INS to track to a VOR - or just tuned the station and flew it like an aeroplane using controls and needles. The Concorde aeroplane encouraged the latter technique because it was so rewarding (but occasionally deeply frustrating) to fly. Good days were phenominal. Bad days were... bad (Mike Riley put this well in his "Concorde - Stick and Rudder" book).
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): INS (Inertial Navigation System) Rudder |
NW1
December 22, 2010, 23:39:00 GMT permalink Post: 6138601 |
Superstab
Hmm. There was, I think, a raft of high-incidence (alpha) protection fitted.
Digging out the old BAe conversion course notes: The "Anti-Stall" (SFC) 1&2 sytems offered: Super Stab: Increased authority of pitch autostab as incidence increased above 13.5 degrees - proportional to pitch rate and incidence angle - and a nose down pitch trim with a Vc (CAS) deceleration with incidence > 13.5 Stick "Wobbler": the "unmistakable warning" - when incidence > 19 and Vc<270kts the control columns took a life of their own and tried to fling you into the forward galley. Served you right. Some other high incidence stuff was fed from the ADC rather than the SFC, like: The ">13.5d incidence" feed to the SFC CAS (Vc) feed to the SFC Incidence from 16 to 19 degrees (rate dependant) to get the SFC to feed in up to 4 degree nose down pitch command and the sticj wobbler trigger. Increase of authority of yaw autostab as incidence > 13.5d Autotrim inhibit > 14.5d incidence Stick shaker >16.5d incidence AP/FD disconnect > 17.5d incidence There was loads of other technical stuff which engineers understood, but we had to learn by writing diagrams which made sense to us enough to pass the written exam. The bottom line was an aeroplane which flew beautifully, but which you had to understand well, and which you could not tease beyond its limits. If you ignored a limit or an SOP then you reached an unpleasant place far quicker than with the blunties - it was a challenge which rewarded as quickly and as deeply as it punished. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADC (Air Data Computer) Auto-stabilisation Auto-trim Conversion Course Galley Stick Shaker |
NW1
January 16, 2011, 13:21:00 GMT permalink Post: 6183091 |
Dude - that really brings back pain form the past! I remember knowing (just) enough about the flying controls to pass the ARB, but a diagram similar to that one was presented at one "Technical Refresher" day (remember those?) by one of our more chatty training EOs (could have been you?!) together with a coloured plastic overhead projector schematic complete with slidey moving jacks and PFCUs and things and it worked! I completely understood the system right up until the first pint of Brains that night...
Flying in mechanical signalling was a different experience - losing the autostabs was bad enough (and proved how good that system was). A mate on the fleet once described it as like trying to fly around on a supersonic dustbin lid. I think that description was too kind - the thing was barely controllable in that configuration. One of our skippers described an airtest when he was on the JS where the crew were trying a decel in MS: as the phugoids were diverging he thought he was about to lose his life so leant forward to restore things. Sadly the switches had been left in MS, so he had to move the switches up to "Blue" as well as then pressing the reset tits - a procedure which he described as almost impossible due to the ever more extreme manoeuvres. Recovery, fotunately, was instant. Resetting electrical signalling and autostabilisation always felt like slotting into a groove on the Concorde. For that reason, I believe, flight in mechanical signalling was removed from transonic flight on airtests and altogether from Base Training. The simulator was the only sensible way of trying to fly like that... And that flying control pre-flight check! Learning it was a conversion course rite of passage: one of the sadder parts of reading this thread was realising I'd forgotten it. Great times, great aircraft, great people. Nostalgia isn't necessarily a thing of the past... see you in March? Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Auto-stabilisation Conversion Course Simulator |
NW1
June 12, 2011, 15:26:00 GMT permalink Post: 6509010 |
What was the minimum maneuvering speed for Concorde
It was expressed in the flight manual as "Lowest Authorised" speed, Vla, and didn't depend on weight. 0-15,000' Vla=V2 or Vref as appropriate, 15,000'-41,000' Vla=250kias, 41,000'-60,000' Vla=300kias Also what was the typical climb speed I'm guessing you mean rate of climb rather than IAS? - At lift-off? From memory Vr was around 200kts, V2 around 220kts and if restricted to 250kts (way below min drag) you'd get pretty poor rates of climb - about 1000fpm if you were lucky and IIRC - you'd quickly want to lower the nose, just barely climb and get her up to 400kts when she'd really fly... - Once 240 kts is achieved? see above - but once you got her up to min drag (about 400kts at MTOW) things went better - about 4000fpm without reheat - At minimum maneuvering speed at typical takeoff weight? At V2 she staggered up due the the drag of the slender delta wing at low IAS - but climb performance on three engines (in contingency reheat) at V2/MTOW was better than a conventional subsonic jet on three / MTOW / V2 due to conservative certification requirements of the TSS - At MTOGW? Does the above answer your Q? Happy to add more if you need... Edited to add, most transatlantic takeoffs were at MTOW - around 185 tonnes - and due to the slender delta aerodynamics, weight didn't affect performance as much as a conventional wing anyway because induced drag was the bigger player at slow speeds - and I've just completely exhausted my very limited grasp of aerodynamic engineering!! Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Afterburner/Re-heat IAS (Indicated Air Speed) V2 |
NW1
June 23, 2011, 23:15:00 GMT permalink Post: 6532637 |
<<
I'm guessing you mean rate of climb rather than IAS?
>>
<<No, I meant the airspeed you'd be flying at while climbing (post takeoff)>> OK, then the answer to your Q's: Also what was the typical climb speed - At lift-off? About 200kts - Once 240 kts is achieved? 240kts - At minimum maneuvering speed at typical takeoff weight? Vla after takeoff was V2 until 15,000'. I.E. about 220kts - At MTOGW? V2 didn't vary much by weight Out of JFK we flew at Vmo once further than 12nms from the coast. Vmo=400kts IAS at low level. Out of LHR overland the IAS restriction was 300kts until past the speed limit point early in the SID - much less draggy than 250kts and hence better climb rates. But you'd quickly be released to get to 400kts (barder's pole) where it was designed to be flown. <<Why higher speed? That have to do with shockwaves and the resulting pressure distribution differences?>> The flight envelope was bigger and more complex than subsonic types: it was developed in flight test and probably had many considerations involved. I think someone posted it earlier in this thread in graphical form (from the flight manual) if you want to see it. In practice, you had to be aware of three basic parameters - IAS, Mach and CG position (the CG "corridor"). Once understood, it wasn't that difficult to keep up with it...and the IAS and Machmeters had barber's poles handily programmed to show the limiting values (including, cleverly, max temp on the nose Tmo=127 degrees celcius). Regarding climb rates - best ROC was at 400kts (MTOW) or 380kts (MLW). As speed reduced below that, drag increased and ROC reduced. At MTOW and 400kts you'd get about 4000fpm max dry power. At 250kts it was all noise and very few feet per minute - after noise abate procedures you had to lower the nose, just barely climb, and get IAS up toward min drag as soon as possible. With an engine failed go for 300kts minimum - Vmo as soon as you can. <<shockwaves and the resulting pressure distribution differences>> You had to avoid the "transonic" region due to these effects: maximum subsonic cruise was 0.95M due to the auto-stabilised flying controls become over-active as shockwaves started to "dance" around the airframe (usually asymmetrically). This calmed down by about 1.3M in the acceleration (when the intake ramps started to do their thing). To accelerate to 2.0M you needed reheat until 1.7M so you didn't hang around between 0.95M and 1.7M. FL260 was best for subsonic cruise because at that level 400kts IAS = 0.95M... Last edited by NW1; 24th June 2011 at 08:09 . Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Afterburner/Re-heat C of G Flight Envelope IAS (Indicated Air Speed) JFK LHR Shockwave V2 Vmo |
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