CONCORDE ACCIDENT - PART 2

[virgin]

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 ]

[beaver eager]

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…

Anyone with the required privileges to re-post this request in the BA section?

There were very few replies but one correspondent posted the following…

I haven't replied to that thread because it's just too big and developing into the usual battle of personalities rather than exchange of info.

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...

[Hoverman]

Beaver Eager says

" ..... 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."

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.

[Al Weaver]

"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.

[Jackonicko]

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.

[BEagle]

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?

[Evo7]

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.

[Capt H Peacock]

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.

[llamas]

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

[Vfrpilotpb]

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!

[John Farley]

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:

The party process presents inherent conflicts of interest for entities that are both parties in an investigation and “parties defendant” in related litigation. Indeed, RAND has found that, at least in certain complex types of accidents, the party system is potentially unreliable and that party representatives may be acting to further various interests beyond prevention of a similar accident. Such potential conflicts may, in some instances, threaten the integrity of the NTSB investigative process, raising numerous questions about the extent to which party representatives are motivated to influence the outcome of the safety-related investigation in anticipation of litigation. NTSB

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.

[Al Weaver]

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

[Jackonicko]

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.

[fireflybob]

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.

[Covenant]

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).



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 ]

[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 ]

[N1/TOGA]

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 .

[Jackonicko]

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.

[John Farley]

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:

The NTSB must substantially revise its practices, more closely manage its resources, and break the cultural insularity that is widening the gap between its staff and the broader aviation community. NTSB’s leadership must make the requisite improvements while continuing to ensure the independence of investigations and the leadership of its professional staff.

Not altogether self-serving stuff in my book.

Regards

[John Farley]

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 ]