Good, thought-provoking posts by both FL and Covenant.
If this was a closed forum, confined to the industry, I might agree with Covenant. But it's not. What is Covenant suggesting? What is to be achieved by this informal investigating body? Do we expect the official investigators to read Prune and take views into account?
I'm totally with FL for the reasons he gives.
BA are about to have Concorde flying again. I for one am pleased about it even if they are the competition. Let's just celebrate.
Anyone who thinks the media will give a balanced account in whatever they write/broadcast is IMHO extremely naive. What documentary into the industry has ever been balanced? The media looks to sensationalise everything for 'shock horror exposure' melodramatic effect.
Most people/companies/industries who co-operate with the media in the naive belief that the final programme/feature will be balanced live to regret it.
IF the accident was due to pilot misjudgement/error then, in the interests of the reputation/future of Concorde, I hope that is made clear. But, whatever shortcomings the official investigation team have, I wouldn't trust the media/Press to investigate - they have no interest in searching for the truth, all they care about is a good story.

[ 30 August 2001: Message edited by: virgin ]

I withdrew from the previous thread some time ago after reading several postings in the BA private forum. BOAC (the Head Honcho BA forum moderator) had posted a link to the previous thread in the BA private forum, entitled “Calling all Concorders”. In it he copied Jackonicko’s plea for information from Concorde pilots… There were very few replies but one correspondent posted the following… I felt that I had been partly sucked into that battle of personalities (despite trying to remain objective) and have since remained (until now) as a spectator on the sidelines. I would now like to add to my previous contributions as I feel that there is a previously undiscussed possibility worthy of an airing. I should like to state though, for the avoidance of doubt (although some may find it blindingly obvious), that I have never been anywhere near a Concorde and have no knowledge of anything “Concorde specific”.

In the previous thread, I supported the theory that a contributing factor to the eventual loss of control may have been that the First Officer, when bringing Marty’s attention to “The Airspeed Indicator… The Airspeed Indicator” failed to add the command “Pitch Down”. I cited possible sensory overload as a reason for Marty’s failure to take corrective action against the obviously decreasing airspeed.

I would now like to suggest an alternative (and in many ways less un-attractive) scenario.

I have learned from these threads that Concorde cannot apparently stall in the conventional sense. Surely though, it must have a limiting angle of attack and therefore some protection against exceeding it? Yet there appear to be no sounds printed in the CVR transcript which relate to any “Stall Warner” or “Stick Shaker”. This may be related to why the First Officer gave no “Pitch Down” commands with his “Airspeed Indicator” warnings.

Perhaps on each prompt of “Airspeed Indicator” (excellent input from the NHP in a sensory overload scenario) Marty snapped out of whatever fifteen other things were occupying his selective attention at that moment (let’s face it, there was an awful lot going on at the time!) and DID actually pitch the nose down to retain flying speed. There would then have been no need for the NHP to issue the command “pitch down” and no automated warnings either.

I offer you the thought that perhaps Marty did NOT at any time allow the airspeed to reduce below flying speed and that the loss of control may well have been caused by the raging fire (I think we can all agree that it was raging, can’t we?) burning through control surfaces or actuating mechanisms.

Without knowledge from the Flight Data Recorder of the pitch angles at the moments immediately before and after the “Airspeed Indicator” warnings by the First Officer, this remains as speculative as any other theory. It is, however, a theory that is much kinder to the memory of the crew , and at least offers a way out of the arguments about whether an off-field landing should have been attempted.

***********************

Wrt the validity (or otherwise) of debating this here on PPRuNe... Perhaps some take BBs such as this too seriously. Whilst the internet can be a useful tool for the exchange of information, my primary purpose in posting on any forum is to amuse myself. That amusement takes a more or less serious tone depending on the topic (and I have been taking this one rather seriously), but in a worldwide circus such as the internet you do have to remember that it is all things to all people. That is its very strength.

Back to the sidelines...

Beaver Eager says
I agree, but it is also its weakness for the reason F/L gave.
'All things to all people' includes the Press reading what we say. Remember the quotes in the Press taken from Prune re the C4/BA pilots documentary?
Wise words F/L.

"If this was a closed forum, confined to the industry, I might agree with Covenant. But it's not. What is Covenant suggesting? What is to be achieved by this informal investigating body? Do we expect the official investigators to read Prune and take views into account?"

The views on this forum are actually helpful. Many investigators are experts in their own specialized fields and generalists in the rest, yet they are official representatives of larger parties to an investigation. Taken as a single expert, they certainly aren't keys to the final answer yet taken as collective viewpoints they are often solicited for areas of further investigation in scope and technical depth. Some of you complain about suspicions of protecting the "party line" especially for manufacturer representatives. Given that most investigation teams consist of multiple parties and their experts, some of us do pay attention to the viewpoints expressed by others, including these forums and do ask questions and express opinions affecting the investigation based on all sources of information that we can achieve.

I have stated in other forums that at least some of the suggested briefing material released after decoding a CVR does take into account issues raised in public domains that can be placed in perspective by what we hear on the CVR.

Keep up the informed questioning, somebody is listening.

I'm always quite shocked at the hatred and contempt which inevitably arises when the media and journos are discussed - especially on PPRuNe. We seem to be the new lawyers or accountants, or even traffic wardens. I can understand the reaction, to a certain extent.

I can see that aviation is seldom well served by the media, which does have too strong a 'generalist tradition' which does not help in accurate, insightful reporting of what may be complex, technical issues.

There are few specialised aviation correspondents in the general news media, and some highly respected specialised aviation magazines sometimes seem to be little more than rehashed company press releases, often with little analysis or expert comment, and sometimes flawed with errors.

But for the benefeit of Flying Lawyer, Hoverman and Virgin can I offer some reassurance. Were I merely looking for a set of 'rentaquotes' I could have gone and written my piece days ago. I want a broad and representative mix of 'expert' views (including informed speculation, there's nothing wrong with that) and I don't expect to come up with anything terribly sensationalist. I may well not even reach a conclusion, but only report an unresolved debate about factors which may have contributed to an accident. My piece will be balanced, and will reflect the fact that not everyone agrees with what I might believe. I would challenge anyone to point to any article in which I have 'unhelpfully' quoted (or even unhelpfully plagiarised) from PPRuNe or even to accuse me of being other than aviation friendly, and sympathetic to the broad needs and aims of the aerospace community. There are some media good guys, and I hope that I'm one of them!

I'm not especially looking to 'expose' any alleged cover-up, I'm just looking for some answers that aren't given in the official report - and let's not forget that there is some scepticism even among aircrew that this will tell the whole unvarnished truth. I want to fill in the gaps, let my readers know more about this fascinating debate, and reflect that there may be some vague unease in certain quarters, and no more than that.

You may believe that the vast bulk of the media/Press is fickle, because some journos have annoyed you, but to generalise like this would be as silly as it would for me to generalise about all pilots based on the actions of those few who may have annoyed me. I'm still saying 'Well done, BA.' and I've never yet 'revelled in scare-mongering stories about Concorde being a death-trap', nor did I ever call for its immediate grounding - quite the reverse.

Why should people help the Press? Well to help ensure that journos have no excuse for not getting their facts right, and to ensure that there is the best possible chance of the media 'getting it right', for starters, and to encourage greater air mindedness in the general population. Your belief that the end-product is bound to be unfavourable to the industry is, in my view, unduly pessimistic, and I hope to prove you wrong.

In this specific case, there seems to be a real worry that some pertinent factors may have been overlooked, and that these should be highlighted, if only so that they can serve as potential flight safety lessons.

Covenant made the point that brainstorming by an 'eclectic group such as this' could be of value in ensuring that no stone is left unturned and no possibility left unexplored, and I can only add that this might be even more useful if there is even the slightest suspicion of the accident report having been produced with political or other considerations in mind. If the widest possible audience are aware of this professional disquiet, and if there is a media spotlight, then it makes it more difficult for anyone involved to get away with anything vaguely shabby.

Please give this journo, at least, the benefeit of the doubt.

At least most people hold journos higher in the pecking order than wheel-clampers or airport security jobsworths!!

Regrettably there are some well known journos who just trot out something they've picked up and publish anything for a story, even if it's glaringly wrong and riddled with inaccuracies: 'Giant Jet in horror death plunge, millions put at risk' when ATC merely requested an expeditious descent and that sort of thing!

If cousin Nigel has been reading this thread and has access to Concorde planning data, could he please confirm the RTOW for the accident aircraft using the actual W/V (090/08), OAT and QNH passed to the crew?

Jackonicko

The media quite rightly has a "strong generalist tradition", and nobody would mind this if the reporting was fundamentally correct. The problem is that so much of it is just wrong, written by people who seemingly do not care at all about the accuracy of what they are writing. On PPRuNe the complaints are about the poor quality of aviation reporting, but it's a pattern repeated across the board.

I'm not saying that you are one of these journalists, and the very fact that you are here now would suggest that you aren't. You're just suffering for the actions of others in your profession. Does it surprise me? Sorry, but no.

BEagleCan I just re-iterate what I posted earlier. The weather from the ATIS was as follows (wind) 15k, NIL, FEW018,FEW023,BKN033,19/--, H1008. The wind had been left out of the report until the erratum of the interim report when it emerged as 080/08kts. The aircraft was known to be overweight to the crew, because this is what was on the recorder (my translation – c’est bonne, je t’assure)

14:13:13 - Engineer “on the gauges I have 96.4 with 96.3 for 95 on board”

14:14:04 – First Officer “ZFW and ZFW CG”, Engineer- “I have 91.9 and 52.2”

That gives a weight leaving the ramp of 91.9 + 96.3 = 188.2 tonnes. Just before take-off the Captain asks this question:

14:40:19 Captain – “How much have we used?” Engineer – “There you had 800 kilos”

14:42:31 Captain – “Go”

They had used just 800kgs 2mins 12 sec before the start of the take-off roll so if we allow say 200 kgs for the last two minutes, that means that using the same information that the crew used, the weight was 188.2-0.8-0.2=187.2 tonnes

That is at least 2 tonnes over the structural limit of 185075 and according to a brief analysis with a friend of mine, who would know these things, they were 6 or 7 tonnes over for the tailwind case. That is not speculation or surmise, that is a direct transcript from the CVR and is the data that the crew were assuming for their performance.

JackonickoPerhaps you will excuse the regard in which pilots hold journalists. We seem to have had a rather hapless experience in the past, and unfortunately it seems the public form their perceptions from what they see and read. We wince every time we read Disaster jet in near smash horror at 30000ft. Thousands almost killed. My night of passion with red hot sexy skipper – busty Belinda tells all.

Please remember that we as pilots bear considerable responsibility with little power, whilst you guys have considerable power, often exercised with little responsibility.

lomapaseo wrote:

"The views on this forum are actually helpful. Many investigators are experts in their own specialized fields and generalists in the rest, yet they are official representatives of larger parties to an investigation. Taken as a single expert, they certainly aren't keys to the final answer yet taken as collective viewpoints they are often solicited for areas of further investigation in scope and technical depth. Some of you complain about suspicions of protecting the "party line" especially for manufacturer representatives. Given that most investigation teams consist of multiple parties and their experts, some of us do pay attention to the viewpoints expressed by others, including these forums and do ask questions and express opinions affecting the investigation based on all sources of information that we can achieve."

To lift from a previous recommendation - we might want to remember, for example, that the root cause of the failure which led to the Challenger explosion was first identified, investigated and then put to the public and the press in a form which all could understand by Professor Richard P. Feynmann, a Nobel laureate in physics but a man who, by his own admission, knew absolutely nothing specific about spacecraft or accident investigation. Who, having once seen it, could forget his tabletop demonstration with a C-clamp and a glass of icewater?

Of course experts in all fields of interest are vital to a full and complete understanding of what went wrong here. But I humbly submit that accident investigations would benefit from the presence of a few generalists - folks who are not members of a specific system community, but who have the skills to look at the bigger picture. Reports from a committee of dedicated experts tend to have the same value as designs by a committee of dedicated experts.

JMHO.

llater,

llamas

If you take a look at the Daily Mail of today, the article that is written by Ephriam
Hardcastle echos wording that can be found on this thread , all about the problems with the Concorde before take off, so we must assume(always a dangerous pastime) that these sort's are looking at everything to write about,that could be sensational.

Jackino, you might be the nicest,sweetest man since the last Lord Lucan, but your trade puts you somewhat outside the area of normal thinking peoples trust, sorry old boy! :eek:

Getting at the truth after an aircraft accident used to be easier in the past than it is today.

Probably the first AAIB investigation that was obviously affected by ongoing litigation aspects was the Staines Papa India Trident accident.

For what it is worth, I believe there are some very honest investigators in the AAIB, NTSB and the BEA. However, such is the complexity of modern types and the operational situations in which they crash, these full time honest men cannot do a meaningful investigation without the help of outside experts. The specialist knowledge they lack is often only available from the manufacturers and the operators of the aircraft that has crashed. This process, whereby such specialists take part in any investigation is known as the “party process.”

In the USA the integrity of the party process, as it affects the NTSB, was recently reported on by RAND. I quote from their report entitled Safety in the Skies:

There is much more in the report than it is reasonable to quote here, but it all essentially says some people may lie because their boss tells them to. Sadly, I don’t find that surprising.

If the media are helped to understand the issues they might aid getting at the truth - or at least make it harder to bury it. Its possible Jacko could make a difference here.

I don't have very much faith in the Rand report since it was produced under the self serving authorization of the NTSB itself. It makes an excellent case for increasing the size and budget of the NTSB. On the other side is the party system and its ability to bring product specific experts to the investigation. The balances at work in the party system (against undue influence) are both the other parties and their experts as well as the IIC of the NTSB. As far as I can see the current system works quite well

To doubt the substance of the official report makes one neither xenophobic, nor even anti-Concorde or anti-Air France. Two ex Air France Concorde aircrew (Jean-Marie Chauve and Michael Suaud) have presented their own report to the French judicial enquiry into the crash.

I haven't seen it or found it on the net, yet, but understand it includes the astonishing revelation that the aircraft didn't hit the metal wear strip until after the tyre blow out!

They also point out that had acceleration been normal, the aircraft would have been airborne 50 yards before reaching it.

Essentially all we are seeking in this accident (and come to that any other) is the truth and what caused it to happen.

Do we trust the official authorities to publish a report which is factually correct?

I am sure that the professional crew members and also the fare paying passengers who perished in this awful accident would want everyone to know exactly what happened and why. We owe it to these people and their family and friends and also all those who will travel on Concorde in the future to ensure that no stone is left unturned.

Having read a number of posts to the effect that delta wings do not stall, I was left feeling vaguely uncomfortable. I am not a pilot, but one of my specialisations in my degree course was aircraft aerodynamics, so I decided to go back and have a look at my text books.

I have in front of me a graph plotting lift coefficient against angle of attack for two different wings: high and low aspect ratio (essentially the difference, from a lift perspective, between conventional and delta wings).

http://users.snip.net/~pjspring/images/clvalpha.gif

For the purposes of simplicity, I'm going to assume that a normal airliner wing is pure trapezoidal and that concorde is pure delta. The truth is somewhere in between, but it's close enough to demonstrate my point.

A trapezoidal wing starts to exhibit flow separation at high angles of attack (12-15 degrees) which leads to flow break-down and finally stall, with the lift coefficient markedly dropping off thereafter.

In contrast, the delta wings exhibits flow separation at even low angles of attack, but the vortices thus produced behind the leading edge are stable and actually contribute to the lift, with flow reattachment occuring at some point on the wing before the trailing edge. This stable leading edge vortex formation contunues up until angles of attack near 25 degrees where the lift coefficient starts to drop off again.

This behaviour is simply explained by the fact that, at high angles of attack (greater than 10 degrees), the leading edge vortex turns away as a free vortex in the main flow direction and, although it continues to provide lift, it increasingly creates reverse flow areas and stagnation zones in the wingtip area. This effect can be readily seen in the creation of tip vortices which are often visible when condorde lands at high alpha.

I suppose it depends a lot on your definition of the word "stall" - which is not actually a precise engineering term. If you define it as the point where your lift coefficient against alpha curve turns the corner, then yes, delta wings do stall eventually.

This graph doesn't even tell the whole story though, because it assumes a constant airflow across the wings (constant airspeed).

Another factor in the difference between high and low aspect ratio wings, which is very important in this instance, is that the drag coefficient increases very much quicker in a delta wing with high angles of attack, and even more so with the formation of tip vortices, which are basically just a waste of energy (pretty, but wasteful :) ).

A delta wing aircraft that is low on power, such as concorde was, really cannot afford to go to high angles of attack because of the dramatic effect on airspeed. Even a delta wing, with its better performace at high alpha, will produce less lift if the airspeed drops off. Without a whole load of power at your disposal, increasing angle of attack is an inefficient trade-off to gain a little short-term lift for a lot of airspeed - much more so than with a conventional wing. Sooner or later gravity will inexorably take over and the aircraft will spin out of the sky.

If that's not stalling, then I don't know what is!!

[edited to add a sentence for increased clarity]

[ 01 September 2001: Message edited by: Covenant ]

[edited to add graph]

[ 01 September 2001: Message edited by: Covenant ]

As a postscript to my previous post (pun not intended), I'd like to follow up on something an earlier contributor said about the normal response of a pilot to loss of lift.

As I have already stated, I'm not a pilot, but as I understand it, the way to get maximum lift out of an airliner with conventional wings is to pull the stick back until you feel the stick shaker, and then hold it just forward of that. This is borne out by the graph I included above - although I still think this action depends very much on you having sufficient available power to overcome the increased drag.

Maybe a concorde pilot, or a military pilot who has flown delta wing jets, can confirm what I believe to be a different approach altogether for delta winged aircraft. I suspect there is a point on the low-aspect ratio wing curve where your trade off of lift versus drag with angle of attack is at its most beneficial. This would vary with available power, as it would with a conventional wing, but whatever the case, I am sure it is well below what we might for the sake of argument call the "stall" point.

My point is that for a delta wing, I suspect there is an optimal angle of attack, probably below 20 degrees, which is not heralded by buffet or stick-shaker and beyond which you should not go without masses of available power to pull you out of trouble.

Again - please understand that there is no disrespect intended - but I wonder if Capt. Marty suffered from his extensive experience with conventional wing aircraft and assumed (granted that we already know he apparently disregarded or failed to comprehend the airspeed warnings from his F/O) that as long as he didn't feel the stick shaker, he could keep pulling back for as long as necessary to reach Le Bourget. In hindsight, with 20-20 vision, time to analyse and reflect, etc, etc, maybe the best course of action from an aerodynamic point of view would have been to allow the nose to come down more and accept the sink rate but at least maintain some airspeed (energy).

I concede that the extreme pitch up that concorde experienced may have been due to a number of factors beyond the pilot's control; for example a rapidly changing COG due to loss of fuel forward of the already unusually aft-situated COG or fire damage to the control surfaces. My comments above are based on the supposition that the increasing pitch up of the nose was due to pilot input.

This is not submitted as factual representation of events on that fateful day, or indeed to imply that this was anything but another minor consideration in the train of unfortunate events, but merely as another point to consider among the many others we have been discussing.

Addendum
Since writing this, I have become convinced that Capt. Marty did the very best he could to extract maximum performance out of concorde in rapidly deteriorating conditions.

I am not deleting this post so that the thread will retain its continuity and the later posts make some sense, however I withdraw any speculation that Capt. Marty could have acted in any other way to prolong the controlled flight of the aircraft at that time.

I have also since been corrected about concorde's design in that a stick shaker (or similar) is included and operates well below the theoretical maximum alpha of the aircraft - not to warn of imminent stall, but to give the pilot intuitive feedback that he is pushing the boundaries of the design envelope.

[edited for typo]

[ 01 September 2001: Message edited by: Covenant ]

[edited for clarity]

[ 01 September 2001: Message edited by: Covenant ]

[edited to include retraction and correction]

[ 04 September 2001: Message edited by: Covenant ]

you are a very bad journalist jackonicko.

you should read the 3 BEA reports, it's a minimum.

- "tyre retreads" BEA report 1

- threshold wind at 14:43 R26:090/3 R08:320/3
14:44 R26:020/3 R08:300/3

- max performance T/O weight limitation :
186700 kg

- 96.3/96.4 = only fuel gauges indication!(max fuel quantity : 119280l+1630l at0.792kg)
actual fuel 94.8 = 119280l + 300l
capt H pecock....no comment!!!

- CDG FOD inspections : read the last report
(comparaison with others intl airports)

- engine 1 lost power due to fuel/hot gas
ingestion. (probably the same thing for
engine 2 if F/E didn't cut off)

- the fire and high temperature have
probably reduced wing performance and
damaged inner elevon (aircraft control).

- "missing spacer" BEA say no consequence
normal acceleration, no deviation.
I am not enough expert to be disagree
and it is not the good place to find
experts!!!

- "french judicial enquiry"..."I haven't seen it or found it"...in this case stop your
speculations!!! wait and see!!! and read at least the 3 BEA reports.

The french judicial enquiry has to settle
the responsabilities (and not BEA).

stupid and steril topic .

N1 TOGA

Please have the decency to be civil, old chap. "You are a very bad journalist" is hardly a good start, is it? The last Concorde thread did start getting nasty, but we're all trying hard on this one to be more measured.

And when senior Captains of large jet airliners, a test pilot of John Farley's reputation, and other informed aviation people express concerns about this subject, it can hardly be 'stupid and sterile', can it? Your lack of respect for your fellow Pruners does you no credit.

For information, I have read all the BEA documents available in English, and have waded through some of them in French (especially the CVR transcript). We know that the report by the two French Concorde captains (presumably 'not experts' according to you) disagrees with some of its findings.

There are many experts on this thread too, and some of them have expressed a belief that the BEA report (only an interim document at present) may be quite seriously flawed, and have explained why. Some are concerned that there have been a succession of flawed reports from the BEA, while others believe that there is always a tendency for reports (not just French ones) to be shaped by commercial or political interests. Yet you choose to give it the respect normally accorded to holy scriptures.

Because you have very kindly posted in English, there are parts of your post that I don't really understand, and thus don't want to answer.

The first one concerns take off weight, where you seem to be disputing the fact that they took off overweight.

The summary of the case for this argument is as follows:

From the accident report we can see that they took off at 187.2 tonnes.

The max structural weight is 185.075 tonnes (not 186.700).

Even if the aircraft was marginally below its absolute structural limit by the time it reached its take off position (and are we sure it had done?) then the 8kt tailwind was sufficient to reduce the Regulated TO Weight (the weight at which it was legal and safe to take off) to a figure below that of the Actual Take Off Weight - so in summary, they took off overweight.

Can you explain how you disagree with this? (Can those who posted these figures originally quote a source, with report and page no., just for the record?)

You go on to state unequivocally that engine 1 lost power due to fuel/hot gas
ingestion, whereas Rolls Royces tests suggest that this verdict may be shaky, and some experts suggest that solid object damage (perhaps the runway edge light) was what stopped it. Speculating on what 'would' have caused No.2 to fail is specious. The engine had not failed and was producing thrust when it was deliberately shut down, without a direct order to do so from the captain.

You speculate that the fire and high temperature 'have probably reduced wing performance and damaged inner elevon (aircraft control)'. You may be correct, but there is no evidence to support this. Captain Marty lost control because he was too slow and at too high an AoA.

BEA may say that the "missing spacer" was of no consequence, but a number of highly qualified experts disagree, and we have already suggested that there are reasons for some people to suggest or suspect that the BEA's conclusions may not be impartial, and may have been tempered by a desire to protect the reputations of the nationalised airline and Aeroports de Paris.

You admit that you are "not enough expert to be disagree" (your profile does not even tell us whether you have any aviation expertise at all, nor whether you even hold a basic PPL) yet you seemingly fail to recognise that others (who are experts - including an accident investigator) do feel that this kind of discussion on PPRuNe is useful, and valuable, and do respect the expertise of many of those contributing to the debate.

If your start and end point is that you can't believe that there is any possibility that the BEA could have got it wrong (by accident or design) perhaps there is no point in arguing.

lompaseo

Thank you for that.

Yes NTSB asked Rand to do the investigation. Yes the report does make an excellent case for a bigger NTSB budget, but my word it is also quite scathing in what it says about the management of the NTSB.

It lists good reasons for saying things like:

Not altogether self-serving stuff in my book.

Regards

Covenant

Nice to see two very informative posts that tidy up some things that others have said – perhaps without full consideration. A couple of points regarding what you said came to mind.

Before I get to those, I must admit that I have never flown Concorde, but I was lucky enough in the mid sixties to fly both the RAE single seat aircraft (HP115 and BAC221) that were purpose designed to study the handling and performance characteristics of the projected Concorde planform. I also flew a Vulcan specially modified to look at piloting aspects of engine failure on take off as it would apply to the Concorde, as well as spent many a long hour in the Bristol Concorde simulator – then used for development and now the primary training aid for today’s crews.

This work, on behalf of the RAE boffins, left me in no doubt that the increase in drag that you refer to (when a delta flies slowly at higher angles of attack than ordinary wings can reach without stalling) is the dominating characteristic of such flight. Indeed it leads to the notion of the zero rate of climb speed (Vzrc) that is mentioned in several appropriate places in the BEA reports. If you slow down to this speed you (by definition) need full throttle just to hold that speed in level flight. One knot (or more) slower and you are in big trouble. You must lower the nose so as to reduce lift and the associated induced drag, which means you give away height in order to pick up speed. Just like the stall recovery case for conventional types. When I left that scene the boffins were seeing this Vzrc as the direct equivalent of Vs for all certification purposes. It is not a stall but it has the same effect as one and margins (1.3 or whatever) would need to be provided to keep pilots away from it just like the stall.

That I guess is neither good nor bad news. But what is very bad news is that the Vzrc is hugely dependent on the amount of thrust at your disposal. If you chop a donk Vzrc may leap up 20 or 30 knots or more depending on the aeroplane concerned. Now you are talking of a much more lethal effect than the slight increase of stalling speed that happens when thrust is lost on most aircraft.

With this in mind the linear part of the “delta wing” curve in your diagram above may not all be usable in level flight – or there again it may be possible to go right over the top and down the backside quite easily if you have monster amounts of thrust attached to your left hand (watch the Russians at airshows). But being on that part of your curve may (again depending on the design) bring about huge trim changes leading to loss of attitude control with even low levels of turbulence.

Perhaps all this is why one hears so much talk about “departures” rather than “stalls” these days. I like it when people talk about the aircraft “departed from controlled flight” because it is all embracing and not just about lift (or the lack of it).

So, months ago, when I first looked at the curves of airspeed, angle of attack and height from the accident flight, I was full of sympathy for Marty’s predicament. For what it is worth, it seems to me that he actually managed to finesse a knot or two at constant height and was initially flying quite brilliantly. Did you notice BTW that when that delicate balance was eventually lost (perhaps due to fire damage of the aerodynamic surfaces with associated change in longitudinal response) how high the aircraft shot up as the lift available at the suddenly increased angle of attack momentarily took charge?

Regards

edited for usb finger trouble

[ 01 September 2001: Message edited by: John Farley ]

I am awestruck by the quality of this thread. It's what makes PPRuNe a unique aviation resource.

Covenant

Check this link for information about Low Aspect Ratio Wings at High Angles of Attack

There are some graphs that quite clearly explains what happens to delta wings at high AOA.

All of the above is backed up by a lot of formulas that doesn't make sense, though, to "normal" human beings :)

you wrote:
I think most here would define stall as the state of flight where the critical angle of attack has been exceeded (i.e. the wing stops producing lift). Drag is another matter and an excess of drag is not the same as a stall, although the consequences may be the same eventually.

-------

But is any of this, or how the Captain flew the aircraft relevant? Isn't it more relevant why they ended up in the messy situation that they did?

[ 01 September 2001: Message edited by: cosmo kramer ]

Cosmo

Could you join me on Tech Log – Votex bursting?

Regards

John Farley

I just want to thank you for a beautifully simple and professional analysis of what Capt Marty had to deal with. I am "just" a private pilot but would have been more if I wasn't so short-sighted. I have loved Concorde since she first flew and anything that will keep this wonderful bird flying safely and help mere mortals (regular non-Concorde/non Delta-wing pilots) understand the issue is very welcome. From what others have said, and I have read, of the career of Capt Marty, I suspect he would be delighted that (a) we appreciate his predicament and (b) we are debating what happened in Paris so that it need never happen again.

I have to say your analysis of the incredibly fine balance he would have had to maintain in extraordinarily stressful circumstances just shows what a great pilot he was - in extremisrelying on his skills, experience and instinct while knowing, probably, that he and his aircraft would not survive the incident.

:)

P.S. any word on when Concorde will make her first flight to/from LHR?

Although the Vulcan was a 'conventional' delta rather than a 'slender' delta, it too had unusual handling charcteristics at low IAS - or more correctly at high AoA. These included significant adverse yaw and ultimately roll reversal with use of elevon in the rolling plane requiring cautious use of rudder to control yaw/roll and rapid IAS decay in level flight unless a lower pitch attitude was selected and a descent established. We didn't take the ac to anything close to the limits during our OCU on type, but I certainly remember how unnatural the low IAS/level flight regime was.

Even in the cruise the high drag at low IAS could catch the unwary! We didn't have any low speed buffet boundary limits as I recall, so when day over the south of France at FL410 when the nav plotter asked for a large speed reduction to cope with the unusual high level wind and timing requirements to make good a low level entry time, the captain decelerated to around 190 KIAS; when we tried to accelerate again it wouldn't do so even with the 4 Olympi bellowing as loud as they could. He had seemingly discovered Vzrc4 for that particular flight level and thrust available and it was only with the agreement of ATC allowing us to descend 4000 ft that we managed to accelerate out of the flight regime.

[ 03 September 2001: Message edited by: BEagle ]

Covenant

In the way of these things I have acquired some manufacturer’s data relevant to flying Concorde slowly that covers some of the points you made here in your 1 Sep 13.01 & 14.35 posts.

I’ll put it over on the Tech Log Vortex bursting thread.

Regards

Having read some of the posts here and in the Tech Log, from John Farley in particular, I think I should withdraw any speculation on the appropriateness of Capt. Marty's actions that I made in my second post of 1st September. It's quite clear to me now that, all other factors being equal, he was making the very best of a very bad job.

I should have just left my first post to stand as it was. That'll teach me to stick to the facts! :)

Cosmo Kramer
Thanks for the link to the low aspect ratio wings at high alpha treatise. I don't think anything in there contradicts what I said in my first post, although the graph does show the non-linear vortex lift continuing for higher alphas than on my graph - probably because it is describing the theoretical total lift and doesn't allow for vortex bursting which, as the author points out, is not easily predicted using theorectical models.

On the tech log, WOK noted that concorde departs at slightly less than 25 degrees alpha in the sims which I suspect is more due to other stability factors than vortex bursting. I also tend to agree with John Farley that, even with all four engines producing max thrust, concorde would not be able to maintain IAS at such high alpha, which effectively puts vortex bursting well outside the normal (or even abnormal) operating envelope of the aircraft.

Nevertheless, at the point of departure from controlled flight, the aircraft, for whatever reason, experienced a dramatic loss of lift, which is essentially what people mean when they talk about stalling. That this was ultimately due to high alpha, high drag, low power or any combination of the three is not really important. One or both of the wings did, in fact, stop producing lift - which is why the aircraft went down and not up!

As you say, although discussion of this point is interesting, it has little to do with what we should be concentrating on with regard to the causes of the accident. My aim was really to clear up any misunderstanding that may have arisen about the nature of slender delta wings and their performance at high alpha. I think between us all, we have managed to do that fairly comprehensively! :)

You are right that isn't important as far as the result goes.

But speaking from a strict definition point of view, I would say that a stall is caused by an exceedance of the angle of attack. Is a wing that is not producing lift stalled? If so is a parked aircraft stalled? ;)

Perhaps, not to clutter up the topic, further posts on this issue should be in Vortex bursting or another new thread in Tech log?

I hesitate to point out to Brit PPRuNers that a Concorde TV documentary is due on Thursday night (BBC 2?) at about 2100. Although I've not seen it, and have had nothing to do with it, I fear that it may generate some anti-journo/anti-media feeling.

But don't blame ME.

PS: What an epic thread! Many thanks to JF and covenant for educating me!

BEagle

Very interested in your comments about Vulcan handling at high A of A. When the lovely bird was flying, the airshow routine seemd to comprise a steep climb, sustained 'till very low airspeed, then a 'wingover', to the right and a dive to recover speed. Given the odd handling at high alpha, that must have been 'interesting', especially for the guys in the back with no bang seats.

Cheers

SSD


PS

Just like to add my thanks to John Farley for his superb contribution to this most interesting thread.

Re weights

Based on that day's met data (a twelve kt headwind, a low QNH (1008), the higher than normal temperature and the usable length of the runway), the dispatcher calculated the maximum weight as 177,930 kg. I'm unclear as to whether this took account of the non-availability of thrust reverser 2, which led to a reduction of 2.5% in the maximum weight permitted.

However, flight preparation showed a takeoff weight of 184,800 kg with one hundred passengers (but not all of the baggage) checked in, and the despatcher then started getting anxious suggesting a route with an optional tech/refuel stop or unloading baggage to follow on another flight - it was at this stage that the crew took over flight planning (in order to stretch or bend the rules?).

The max structural weight is 185.075 tonnes.

From Captain P's reading of the report it has been said that they took off at 187.2 tonnes, though in the latest report it is suggested that the accident investigators recalculated the figures, and came to the conclusion that actual TO weight was an estimated 184,802 kg.

So was the aircraft marginally below its absolute structural limit (as suggested by N1 TOGA) by the time it reached its take off position, or two tonnes overweight (cf max structural), or ten tonnes over the max weight originally calculated by the despatcher. And all of those overweight figures are without the 8 kt tailwind.

Ten tonnes. TEN tonnes? Can some-one confirm that I've got that right?

After re-reading the BEA reports, I have just noticed a rather critical erratum in the preliminary report which was corrected on page 7 of the first interim report (15/12/2000).

Rather significantly to my earlier post, it says that, with reference to the control column position graph, positive values indicate nose down input rather than nose up, which was how it was shown on the key in the preliminary report.

What this means is that contrary to what I had previously believed, the pilot was constantly using nose down input to the control column from about 12 seconds after rotation. This is especially significant at around time 97667, where it appears the AoA begins to climb out of control. I had originally thought that the pilot responded by pulling the stick back through some 4 degrees (which seemed to make little sense, I admit).

It appears to me now that Marty was indeed trying to hold the AoA to around 12-13 degrees for the bulk of the flight against a tendency to go nose-up, rather than trying to hold the nose of the aircraft up to maintain height, as I had originally thought.

What a difference a little "+" sign makes!

[Edited for the usual typos]

[ 04 September 2001: Message edited by: Covenant ]

Jacko - I'm pretty sure that the flight despatcher's figure allowed for the known thrust reverser unserviceability and it doesn't have a material bearing on the accident.

The "investigators' recalculation" doesn't make clear whether that was a RTOW or ATOW estimate; it was way short of the ATOW figure known to the crew and that figure was known by them to be in excess of the max permitted certificated structural TOW.

Nowhere in the report do I read a clear and accurate assessment of RTOW based upon the known 8kt tailwind, the actual OAT and QNH at the time. WHY NOT?? Informed comment in this thread puts the figure at around 177T...

Elsewhere, John Farley comments upon Vzrc2 both with the landing gear up and with the landing gear down. Also, we learn that any decrease in thrust at low speed will lead to a rapid loss of speed and an increase in Vzrc. So why would anyone ever consider shutting down any engine still producing thrust with the landing gear still down??

[ 04 September 2001: Message edited by: BEagle ]

BEags: If it's 177 tonnes for that day's OAT and QNH, but with a 12 kt headwind, how much lower for an 8 kt tailwind? What ballpark difference would we expect?

Incidentally, for those who doubt it, the Structural weight limit for take off is 185,070 kg and for taxying is 186,880 kg.

The accident report suggests that the aircraft taxied out at 186,757 - 87,251 kg, and took off at 185,757 - 186,251 kg, though these are guesstimates, based on what the two Air France Concorde chaps producing the report for the magistrate regard as unduly optimistic estimates of baggage and pax weights.

Covenant: With regard to the trace of control column inputs, the idea that all the +s represent stick forward seems bizarre - do the traces show that they pushed forward to rotate (it would be a neat trick)?

Also, the AoA was held to a reasonable level (without much stick input at all), so the subject of stick inputs is hardly relevant - 2° either way hardly represents the Captain pushing forward to keep the nose down (nor pulling back to keep it up) terribly hard. Right up until the final turn, where the speed started to decay (from 208 kts down to 181, and later much lower), the AoA went up and the aircraft's rate of climb began to increase markedly, the Captain was flying it with great delicacy, nursing the aircraft into a gentle climb straight ahead. The lack of 'fighting to keep the AoA down' may also be indicated by the fact that the pilots' had wound in significant nose up trim however, and did nothing to select more nose-down trim.

Also, while the co-pilot kept shouting for airspeed, the captain kept it pegged at 199-211 kts (precision flying, under the circumstances), and the aircraft gently but steadily climbed to 182 ft as it crossed the motorway, and to 300 ft as it began the final turn.

Would you guys have done that, or would you have stayed at 100 ft and tried to get closer to the Vzrc speed as you belted for Le Bourget?

gear up:
two engines 262 kts, three engines 193 kts
gear down:
two engines 300 kts, three engines 205 kts

VMCA:
three engines 132 kts
two engines 157 kts

Did they begin turning for Le Bourget too late (forcing them into turning more tightly, with more angle of bank, than was perhaps wise)? Would you have begun turning earlier (even before crossing the motorway, perhaps turning to intercept the Le Bourget extended centreline, rather than flying a mile beyond it?) would the aircraft have departed in a gentler, faster but much lower turn?

I hear what you've all said about Delta wings stalling, but looking at the altitude/airspeed/AoA traces you can see that the aircraft effectively stalled and spun once airspeed decayed/alpha increased beyond a certain critical point.

If I'm being over-simplistic or showing my PPL limitations, please educate me!

Jackonicko

The original trace in the preliminary report shows control column negative input as the pilot rotated and for the next approximately 12 seconds where it became positive and remained so for the duration of the flight. The key says "+ Nose Up". The first interim report corrects this to "+ Nose Down".

Of course, if I'd been thinking properly, I'd have realised the error since, as you say, it would be a pretty neat trick to rotate with nose down input on the control column! :)

I don't think I was implying that he was "fighting" to keep the nose down, more that there was a moderate amount of nose down input, contrary to what I had originally thought which led me to wonder if he was trying to maintain altitude at the expense of airspeed.

I see more clearly now :rolleyes:, and think he was more likely, as you suggest, to have been doing some delicate speed control by nudging the nose forward under what power he had available.

To comment on your last few paragraphs, I've been trying to visualise the flight path from the CDR traces, and ended up actually modelling the aircraft for the last 30 seconds of the flight, in a 3D program I use, to try and get my head round it.

Having done that, I would venture to suggest that the real critical problem was not attitude or angle of attack, but roll. As you say, neither of the former parameters was all that excessive for most of the flight, and by the time AoA did become excessive, the roll to the left was around or above 90 degrees. At that point, lift production is purely academic. I don't think the roll angle got this bad because the pilot tried to turn too hard or too late.

I suspect it would have had more to do with control surface problems, specifically elevon failure on the left wing. Since the pilot was demanding slight nose-down during the fire, if one of the left elevons became frozen in place, it's not hard to see how that would cause an unstable situation leading to uncontrollable anticlockwise roll. It may even be that it was this extreme angle of bank which caused the #1 engine to ingest greater quantities of the burning fuel (leaking from inboard of the engines) and finally give up the ghost.

Whatever causes and effects or the actual sequence of events, by this time, the plane was uncontrollable with no more options left to the pilot. Furthermore, with this event about to happen, I don't think there was anything more he could have done at any point during the flight.

In many ways, this also makes all the other questions about TOW, CoG, tailwind, missing spacer bar, and anything else that didn't directly contribute to the fuel fire, purely academic. If your control surfaces lock up, you're in big trouble regardless of your height, speed, or anything else for that matter.

In my mind, it's back to the question of how and why the fuel leak and subsequent fire started; all other questions being interesting but not significant.

[ 05 September 2001: Message edited by: Covenant ]

Jacko - the 177T RTOW figure was, I believe, an unofficial figure based upon the actual 090/08 wind passed to the crew with their take-off clearance - not the pre-flight calculated value using the ATIS conditions at that time.

We introduced 'late change' data for the Vulcan in 1978 specifically to allow for last minute wind/temp/pressure changes influencing the V speeds - and it's something we teach our VC10 students during their simulator training. It is absolutely fundamental on heavy transport category aircraft to recompute RTOW if the weather values are different to the planned values on departure; equally it is never acceptable to ignore RTOW or max permitted take-off weight limits. I would be very, very unhappy at ever flying in an aircraft whose crews seemingly ignore such limits......

Covenant & BEagle,

Many thanks.

But the AoA was kept as 'tight' as the airspeed until the turn (beginning at point 7 on the photo), where roll rate also increased dramatically.

At point 8 (181 Kts, angle of bank going from 38° to 93°, AoA up to 19.5°) it looks as if he'd lost it - and to my uneducated eye, had over-banked and tried to 'hold' the nose up. At that point, the left wing had (sorry) seemingly 'stalled'. Four seconds later the speed was down to 136 kts, and AoA was 25.15°, while the roll angle was beyond 90° (spin or incipient spin?).

1) Why climb to (and indeed through 200 ft) without coming close to VZRC2?

2) How much more airspeed might they have got if they'd flown level, rather than climbing at about 180 ft per minute?

3) Why not turn gently towards Le Bourget much earlier (the direction the aircraft wants to go, and to keep it straight you're using right rudder)?

I believe that the dispatcher's originally calculated maximum weight was the RTOW for that aircraft on that day in those conditions (177,930 kg - very close to our 177 tonnes) and the fact that the actual TOW was so much higher was what made him start kicking up a fuss. Is it interesting or sinister that the accident report does nothing to explain why his RTOW figure was so much lower than the one they came up with as being 'appropriate', or is this the difference we'd expect for the different RWs - the dispatcher planned for 27, they planned for 26?

From the report:

"Based on data on the wind (a twelve kt headwind), the QNH (low, 1008 hPa), the temperature (higher than the norm) and the usable length of the runway, the dispatcher calculated the maximum weight as 177,930 kg. However, flight preparation showed a takeoff weight of 184,800 kg with the one hundred passengers checked in.

At about 09 h 30, the dispatcher informed the duty officer of the weight problem, without however specifying the QFU used for the calculation. The duty officer first thought of using another aircraft, then tried to resolve the technical problem with the reverser and finally thought of loading the baggage onto another flight.

On his side, the dispatcher studied two hypotheses for routes (one direct and one with an optional technical stop) and loading so that the flight could take place in terms of its weight.

A little before 10 h 00, the crew called the dispatcher who informed them of the problem. The crew informed him that they had asked for the replacement of the failed pneumatic motor on reverser 2, asked him to file a direct ATC flight plan and told him that they were going to take over the flight preparation themselves."

Jacko, perhaps prompted by V1TOGA's posting I can only say that as a pilot and having lost both parents through an airliner crash I, and I think many others, applaud your efforts to obtain a clearer understanding into whatever facts can be reasonably ascertained in the sad ending of that Concord flight.
It can only be hoped that the information thus gleaned will be of use to others. In the meantime I follow your findings and the informed discussions with great interest and hope like us all to see Concord airborne again.

How can you see that? :confused: The reason I keep digging in this stall thing (which by now we should agree that Concorde doesn't) is because it somewhat implies pilot error. You have no facts to support vortex bursting, which as far as I can read from the Vortex bursting thread would require a hypothically high AoA, and the aircraft would probably become unstablile before reaching that AoA. All you know is that for unknow reasons the aircraft rolled over and crashed (speculation as to why may be e.g. fire damage to the control surfaces). This does not necessarily imply that the wings were not producing lift. However, as Covenant mentioned it is academic to discuss lift if it doesn't act in the opposite direction of gravity (i.e when roll is greather than 90 deg).

See above, and atleast support speculation with some facts. Otherwise one might just aswell say that aliens shot it down with a laserbeam ;)

If talking about a conventional wing (that stalls ;)), the right wing would stall first in a left turn because it has the highest AoA.

Are you suggesting that they should have let it sideslip towards Le Bourget (keeping the wings level and let the nose drift)? That is not the most aerodynamic efficient way of flying.

After 150+ post on this topic, I for one, feel more and more confident that the accident was indeed caused by the tireburst and subsequent fire. If it was the fire damage that caused the crash, overweight, engine shut down, etc. would not have been factors that directly contributed to the crash.

Cosmo,

Sorry to upset you with my inexact terminology.

JF wrote: "The increase in drag that you refer to (when a delta flies slowly at higher angles of attack than ordinary wings can reach without stalling) is the dominating characteristic of such flight. Indeed it leads to the notion of the zero rate of climb speed (Vzrc)..... If you slow down to this speed you (by definition) need full throttle just to hold that speed in level flight. One knot (or more) slower and you are in big trouble. You must lower the nose so as to reduce lift and the associated induced drag, which means you give away height in order to pick up speed. Just like the stall recovery case for conventional types. When I left that scene the boffins were seeing this Vzrc as the direct equivalent of Vs for all certification purposes. It is not a stall but it has the same effect as one and margins (1.3 or whatever) would need to be provided to keep pilots away from it just like the stall."

This is why I used the word 'effectively' when I described the process as stalling. Perhaps I should have written:
"looking at the altitude/airspeed/AoA traces you can see that the aircraft departed and spun (there is no doubt that it's final manoeuvre was a spin) once airspeed decayed/and induced drag due to excessive alpha increased beyond a certain critical point."

To suggest that the cause of the departure was control damage (even the BEA does not claim that the controls were not functioning at the time of impact) is as speculative as my suggestion that the pilot mishandled the aircraft (so perhaps you too should support speculation with some facts, or shall we both agree that aliens shot it down with a laserbeam?).

(And to be fair, I don't think my 'speculation' was so very far fetched: "At point 8 (181 Kts, angle of bank going from 38° to 93°, AoA up to 19.5°) it looks as if he'd lost it - and to my uneducated eye, had over-banked and tried to 'hold' the nose up." does it?)

With regard to wings stalling in a turn, isn't the out-of-turn wing travelling faster than the inside wing, with faster relative airflow? In an erect left handed turn which wing stalls first?

To clarify, I'm not suggesting that the pilot should have sideslipped all the way to Le Bourget (though in those circumstances, keeping the ball centred might not have been a prime concern). Do we even know that the aircraft wasn't perhaps already sideslipping, with the constant starboard rudder pressure?

May I challenge you on two questions, since you express yourself so confident that you 'know' what happened?

1) How confident are you that the combination of excessive weight and undercarriage problem didn't exacerbate or even cause the tyre blowout, or, if not that, that it didn't cause the ignition of the fuel?

2) How confident are you that shutting down the No.2 had no effect on the outcome?

3) Can you explain how the outcome would have been the same had Marty traded altitude for airspeed, by not climbing above 100 ft, and had he made a faster, gentler earlier turn towards Le Bourget? Or is it OK for you to speculate, but no-one else.

I don't know the answers, I don't have a firm idea of what caused the tragedy, but I do believe that there may have been multiple factors at work. Why do we need to over-simplify it without evidence that it was simple?