Videos Of Challenger 600 Crash In Aspen Colorado

[Kip Powick]

Mizar.............

There is no disputing much of the information that you post in this thread and others, should you substantiate it with appropriate links. Even you must know that, at times, even links that 'appear' to be credible can be in error and even if not in error are easily interpreted by different people in different ways. The Internet, (links), can be error or outdated, but of course you know that.

The problem, as I see it, is that often you post data/opinions/stuff, that you feel is 'gospel' and you seem to answer back with a tone of denigration toward those that may have different opinion about your information...whether you be right or wrong. This forum is a discussion area and while it is true there has been the odd spat about topics, I think it would be safe to say that all of us get along well in the "sand-box" ............then you arrived on the scene.. (again)............... and took upon yourself, whether purposely or unintentionally, to be " the" authority on each and every subject you concern yourself with.

You must be discussing, (posting), some of these subjects with blinders on if you fail to see that your methodology, syntax, and tone, in many cases really annoys many of the members of this forum or........... maybe it is just your way, but I really don't think it is a good way to have an intelligent and engaging discussion.

In your above post you mention Don, and you are correct, he is a most ardent, well versed individual that can write circles around the vast majority of posters on this forum but.............if and when he does make an error or 'thinks' he has PO'd someone he is extremely quick to get back in the forum, apologize and even look at the issue in a different light. Probably one of the most credible posters on this forum.

Just a suggestion, but perhaps a slight change in your 'tone' might make topics move along without a lot of 'rock-throwing'.

[DEFCON]

Mizar

You're obviously an intelligent guy and you do write very well.

At one time I was intimately familiar with the US Air crash you referenced. It was a required 'study' subject.

Correct me if I'm in error, but this whole debate started when you referenced an 'uncontaminated' slatted wing relative to a high performance maneuver. My first response pointed out a fact that I think you now may agree with? That is; if an aircraft is flown 'properly' a clean slatted swept wing will not provide a performance / safety advantage over its un-slatted cousin. Somehow, the debate morphed into the realm of contamination and its impact on wing performance.

When it comes to debating the finer points of aerodynamic law, I will always defer to the experts. We as ATP's know what we know, but sometimes our need to know more can lead to technical interpretations that can be quite dangerous. History and most pilot induced crashes have not proven otherwise.

Have you ever stopped to consider the consequences of rotation rates on swept wing performance and how that may play in the debate we're having? Three degrees per second is the norm, but it's not a rate that's commonly applied. If there's contamination involved on T/O and a pilot rotates at a rate that's faster than normal, flow separation can be expected. The 'hard' wing will be much more susceptible to the negative effects of contamination in this case than the slatted version, which is likely one of the reasons hard wing aircraft are involved in more contaminated wing T/O's. If so, it's hard to suggest one wing style / design requirement is better than another if pilot technique is contrary to the guaranteed performance provided through the certification process.

[Mizar]

Have you ever stopped to consider the consequences of rotation rates on swept wing performance and how that may play in the debate we're having? Three degrees per second is the norm, but it's not a rate that's commonly applied. If there's contamination involved on T/O and a pilot rotates at a rate that's faster than normal, flow separation can be expected. The 'hard' wing will be much more susceptible to the negative effects of contamination in this case than the slatted version, which is likely one of the reasons hard wing aircraft are involved in more contaminated wing T/O's. If so, it's hard to suggest one wing style / design requirement is better than another if pilot technique is contrary to the guaranteed performance provided through the certification process.

Thanks Defcon,

You have brought up a very important point. Rate of rotation. This can have a huge effect on the performance outcome of a contaminated(or even non-contaminated wing) versus normal rotation.

There have been several times in my earlier career when I suspected that there could be contamination on my wing during the takeoff roll. One time it was reported as 1 degree C and there was water on the wing. They were drops of water not a smooth film. The aircraft guage said 1 degree and so did the official weather. We were in a slatted swept wing jet. I was worried that it could freeze or even possibly be frozen but it appeared liquid. It was a remote area with no real ground support except a marshaller. When I asked the captain to look he said it was just water. His look at the wing from the L1 door for a couple of seconds did not take very long. The small area I could touch on the leading edge was water but what about cold fuel soaking a wing. The tanks were not full. It probably was water but it was evening and not likely to get any warmer.

So what to do if it freezes in the time from now to takeoff in what will be 15 minutes minimum. Bottom line like any time there has been a concern(like freezing drizzle on a high wing that may not be visible if your fluid broke down), I made sure I rotated a bit more slowly than normal and at a speed a bit higher than normal and no that was not part of the briefing. Bad CRM on my part. Apparently there was a bit of ice on the wing that could be seen when airborne. Enough to cause an accident for a normal takeoff, not likely. Yes, I know, I should never have departed without confirming the wings were free of contamination but something to consider if at V1 you suddenly remember that you were supposed to de-ice or there is a concern for some reason.

Some of the wing contamination accidents have involved faster than normal rotation rates and I believe Bombardier had CRJ200 or Challenger test flight crash in Wichita in which rotation rate was a contributing factor.

On that note, perhaps some of the old 737 and baby DC-9 drivers can confirm that the old 737s and baby DC-9 had a six degree rotation rate. It is mentioned in a report I have but that it was changed to 3 degrees after some pitch-up-roll off 737 contaminated wing incidents and baby DC-9 accidents.

[Mizar]

Mizar.............

There is no disputing much of the information that you post in this thread and others, should you substantiate it with appropriate links. Even you must know that, at times, even links that 'appear' to be credible can be in error and even if not in error are easily interpreted by different people in different ways. The Internet, (links), can be error or outdated, but of course you know that.

The problem, as I see it, is that often you post data/opinions/stuff, that you feel is 'gospel' and you seem to answer back with a tone of denigration toward those that may have different opinion about your information...whether you be right or wrong. This forum is a discussion area and while it is true there has been the odd spat about topics, I think it would be safe to say that all of us get along well in the "sand-box" ............then you arrived on the scene.. (again)............... and took upon yourself, whether purposely or unintentionally, to be " the" authority on each and every subject you concern yourself with.

Just a suggestion, but perhaps a slight change in your 'tone' might make topics move along without a lot of 'rock-throwing'.

Kip,

I would like to make a few quotes from this thread on this post.

Concerning my simple(although repeated) statements about slatted vs non-slatted wings were these statements,

I think adherence to the safe rule is prudent versus being short-sighted and putting my faith and everyone that's involved life on the line because I may have a misguided appreciation of airfoil performance.

There are old pilots and there are bold pilots, but there aren't any old, bold pilots. I think it's probably their arrogance that kills them off?

what is it about pilots that allows them to take and hold some pretty dangerous positions on matters of aerodynamics without their being particularly well informed, or educated in the subject matter?

I let those statements roll off and finished with a compliment to said poster. I did say that some unknown engineers were incorrect but does that really justify these statements or hints about me.

Then you posted this

Remember all.........................

for some it is very hard to be humble when one thinks they are greater/more knowledgeable that all the others

And then Moon adds something else that has no relation to this thread but does not appear very complimentary. Can you provide quote on this thread by me that are out of line.

I admit that I have been direct in some of the political threads but I see all kinds of political insults thrown at leaders and at me by others yet only I seem to get castigated. That is politics though and that is fine but I would say that I have been no more out of line than others but the others seem to get upset at a similar style.

I will try to get the thread somewhat back on track by posting the page that Malcolm asked for. It is on page 69.

Defcon to answer your question, I originally posted this:Good point about the rapid pitch action in a low energy situation. In the YFC, contamination was critical, in Aspen, the higher elevation with a rapid pitch up in possibly a low energy state could be crucial, the final report will be interesting I hope.

You replied with this:Mizar

You referred above to an uncontaminated wing with 'slats'. Slat equipped aircraft don't provide any additional protection against things such as contamination etc.

[Mizar]

Correct malcolm. In other words, The FAA knew at the time that non-slatted wings were much more susceptible to wing contamination but when the NTSB asked that this point be made for the knowledge of pilots, the FAA refused on the basis that you stated above and I stated previously. The goal was to get all planes deiced and the idea of publishing information to make pilots more aware of aerodynamics while at the same time still having a rule for de-icing was not acceptable to the FAA.

The end goal is laudable but can backfire in ways not thought about in my opinion.

[DEFCON]

Good Lord gentlemen....when you're standing on a ramp looking at an aircraft full of pax, you're not in an experimental wind tunnel scenario. Performance degradation due to wing contamination can NEVER be quantified, or qualified by a pilot under any circumstance, regardless of wing design.

The FAA never claimed a non-slatted wing was 'much' more susceptible to the effects of contamination. From my pov, without publishing a word, their inferred message was; given the opportunity, a pilot somewhere will apply his non-educated guess to a T/O situation and kill everyone on board. Instead of issuing a statement that may encourage pilots to make faulty non-demonstrable rationalizations to govern flight safety decisions, the FAA, TC and others produced a one size fits all rule.

[DEFCON]

Malcolm

A serious question in response to your post immediately above and not an insult; so what? IOW's, what does the statement that you've captured / quoted mean to you?

[Don Hudson]

Fascinating discussion.

I was taught that hard wings stalled at different AoA's, (ie., at a reduced AoA and therefore "earlier"), than slatted and slotted wings.

Part of that understanding was, I expected that the differences would be the same for contaminated surfaces but the actual AoA at which the wing begins to stall would be reduced, (lower AoA for given conditions), perhaps, as most would know here, below the threshold for the aircraft's stall warning system.

I am not an engineer nor am I trained in mathematics, statistics or aerodynamics so the subtleties of how that wonderful work is done will forever elude me but one can get a sense of the work by study and by engaging those who do the work.

An aeronauticist friend, (now retired), recommended Shevell's, "Fundamentals of Flight", (it can be purchased for a reasonable price at Alibris). While doing some work on AF447 we talked about Prandtl's theory of lift, circulation, vortex formation and all kinds of fascinating things I never knew about the transports I flew!

From Shevell, I think the following may settle the matter of the effect of slats & slots on AoA. Shevell doesn't discuss contaminated wings but for "standard" contamination levels I think it is reasonable to assume that the AoAs remain approximately the same in relation to one another even as both will reduce.

The meaning of the phrase, "much more susceptible", (to stalling with regard to hard wings), means, I think, that without the increased lift due to increased energy of the fresh air over the wing created by the slat or slot, a "hard" wing that is contaminated will stall at a lower AoA than a similarly-contaminated wing with slots or slats.

As with others here, I see the danger in such an awareness and agree with comments made concerning the impression that there is "some latitude" for aircraft with high-lift devices. That is easily countered by the statistics which are clear, and thankfully are dealt with both by airmanship and regulatory requirements regarding the clean wing concept. Such "latitude" in aviation is always a "gift" of sorts; one should never spoil such a gift by accepting it...

Fundamentals of Flight, Shevell, Prentice-Hall, 1983, pp 236 - 237

Regarding this sad accident, it doesn't appear that the airplane stalled, but, as others have earlier observed, porpoised much like the FedEx MD11 at Narita.

[DEFCON]

The aeronautical engineers name near the top of the document has some relevance to some of us here.

Takeoff_and_Landing_In_Icing_Conditions.pdf

[Don Hudson]

The video in which the airplane leaves camera range top-left is I think, the first approach & successful go-around. One can see the infra-red picking up engine exhaust at high power.

Does anyone see that on this attempt the airplane appears to bounce in the same way it does in the second landing on which the aircraft crashes?

In the video that keeps the aircraft in view after the initial impact, the smoke plume seen rising is moving at a tremendous speed, (comparatively), indicating the kinds of winds in which the landing took place.

It appears as if control was lost on both touchdowns and only the first go-around was successful.

The nose-down pitch after (what I believe was) the third bounce on the second landing attempt is extremely violent, leading me to wonder if the control column was struck and pushed forward by something/someone. On viewing it a few times, it could indeed be a stall.

[DEFCON]

Don

The DC9-30 was never intended to be flown without slats and I think its airfoil Reynolds number would reflect that consideration. If I understand correctly, on a normal take-off and by design, the slatted wing is necessarily at a higher AOA at lift-off than its non-slatted cousin, which reduces comparative stall margins accordingly. For the provided DC-9-30 charts to be useful to the debate, I think we'd need similar charts for the DC-9-10 series, which would necessarily include velocity information as well. I'm unable to locate anything relative on the net.

Rotational rates that are too fast and or too steep are the more likely master link in the non-slatted contaminated wing crash chain than any other factor. If pilots operated these aircraft as per the certification criteria, the crash rate between both wing types would I think, be very comparable. When all the technical aerodynamic variables are considered, and they are many, any education that encourages pilots to believe the slatted aircraft is the safer of the two in dicey conditions is to ignore the professional failure that leads to mishaps in the first place.

[Mizar]

Rotational rates that are too fast and or too steep are the more likely master link in the non-slatted contaminated wing crash chain than any other factor. If pilots operated these aircraft as per the certification criteria, the crash rate between both wing types would I think, be very comparable. When all the technical aerodynamic variables are considered, and they are many, any education that encourages pilots to believe the slatted aircraft is the safer of the two in dicey conditions is to ignore the professional failure that leads to mishaps in the first place.

What evidence do you have that pilots of hardwing jets have an increased rate of rotating at a faster rate than the slatted jet pilots. There is of course little likelyhood that this was ever the case. I should think the NTSB's statements are quite accurate. That being exacty what I have repeatedly stated and now provided the much requested proof backed up by studies at Douglas Aircraft.

[DEFCON]

Mizar

Here's a link to a Pprune discussion. Many leads for you to follow up on can be found within. Take a moment and perhaps learn something about the type of aircraft you fly rather than playing pretend aero dynamist. Personally, I think you're beginning to sound like the kind of pilot that's going to make the news someday...and it won't be a pretty story!

http://www.pprune.org/tech-log/223852-danger-rapid-rotations-2.html

[Don Hudson]

Hi DEFCON;

Re, "The DC9-30 was never intended to be flown without slats and I think its airfoil Reynolds number would reflect that consideration."

Well, I know enough about aerodynamics and the concept of Reynolds Numbers to recognize that it gets very technical and for the uninitiated, mathematically complex at the "Reynolds Number" level of discussion and of course that is well and truly beyond my pay grade!

While I don't "speak the language", one can intuitively understand "thickness of a fluid, like honey", (viscosity), "pushing a spoon through honey", (inertial or kinetic energy) and "length" (frontal or wing-area dimensions, or the size of the spoon!) to know that smaller-in-relation-to-larger (spoons, say) need a way to compare the behaviour of fluids-encountering-bodies for wind-tunnel work, and that aeronauticists know that RN satisfies this need, (being called a "similarity parameter"). Now getting that extreme simplification to apply to the -30 slatted wing as compared to the non-slatted wing is for me a leap of knowledge and imagination! I read that the Reynolds Number is the inverse of a term used in calculating "F", or force. From Shevell:

Hi Mizar;

Again intuitively, one senses that there is less requirement to give fluid "time to alter course", (inertia, as in change of AoA), and still keep the boundary layer attached to the leading-edge wing surface on a slatted wing than on a non-slatted wing. The reason being, (according to Prandtl), that slats impart energy to the airflow and do a remarkable job of keeping the boundary layer attached while doing so, requiring a higher AoA to be effective, (all this is from Shevell, not me and in physics, intuition can run counter to reality). Given this, one could conclude that a non-slatted wing in a snap rotation would perform less well than a slatted wing.

In terms of "evidence", the Continental Airlines 1987 DC9-14 accident at Stapleton was an example of a snap rotation, in combination with a contaminated wing, (see ref re F/O rotation technique, p.36). However, the rotation rate was a result of inexperience and not necessarily a pilot-decision that was associated with the DC9-14's non-slatted wing. The CRJ accident in China was also associated with wing contamination. I'm not aware of any available flight data on this accident. If I recall, there were comments regarding the YFC CRJ accident concerning (or which resulted in the installation of) leading edge "strips" and their relation to the stall characteristics of the non-slatted wing. I haven't the time at the moment for further research!

[DEFCON]

Don

I have about the same level of Reynolds Number expertise; other than a basic appreciation for the concept, my knowledge base is pretty limited.

If I understand the principle properly; when the air passes through the 'slot' between the extended slat and the wing leading edge it energizes the boundary layer.

Thanks for providing the Denver link. In fairness I should have said; fast rotations and over rotations can easily be induced as opposed to being intentional when runway surfaces are contaminated and or the wings of certain aircraft are as well.

[Don Hudson]

Hi DEFCON;

I have an exceedingly patient aerodynamicist friend who endures my questions and helps push me along in this stuff - it really is fascinating but, like photography or music, I'm very glad I don't have to earn a living at it !!

The Denver Report does mention the potential for pitch-up in uneven wing-contaminated circumstances - ie., if the tips stall first, where the wing is still flying, the CP moves forward - (HTBJ - Davies).

The Report also states that wings without leading edge devices are more vulnerable to performance degradation due to upper-surface contamination than wings with high-lift devices installed, (Report, p.35, last para.), which is pretty definitive in terms of criticality of the non-slatted design. I was at the Boeing Everett plant a couple of days ago and watched a brand new B747-800 freighter take off with "white stuff" just streaming off the wings, the fuselage top "sparkling" with the same stuff...the temp & dew point would have been within a degree or two and the OAT was +3C...

[DEFCON]

When I've seen 'white stuff streaming off wings', my first thought is, 'dry snow', but who knows? 'Sparkling', is a term that makes something more sinister comes to mind.

I agree with the notion that a slatted wing will produce some well defined aerodynamic advantages over the non-slatted version. On the other hand, one can also say, the non-slatted wing will too produce some well defined aerodynamic advantages over the slatted version. The trouble is, neither type is without its weaknesses when contamination is present. The aerodynamic qualities associated with a contaminated wing on either version turn calculated takeoff V-speeds into little more than rough guidance material; the takeoff becomes a flight test of sorts with unpredictable results.

The trouble is; some pilots seem to want to believe the slatted wing will confer some type of measurable protection from poor decisions that may be made during periods of inclement weather. Nonetheless, the aerodynamic facts tell a different story; any advantage the contaminated slatted wing may have over its non-slatted cousin on takeoff is very minor and when said advantage is considered along with all the 'known' negatives of the design, any belief in the so-called protection provided by slats isn't really offering ones self much more than a false sense of security.

[Don Hudson]

DEFCON;

I don't know what to make of the white stuff - seems like it's just flowing off:

Regarding, "some pilots seem to want to believe the slatted wing will confer some type of measurable protection" and such "conferring", well the airplane doesn't know anything about wishful thinking and we all know the solution.

One story. I can recall a frosty early morning at SFO; - all they had was ropes and brooms, no de-icing fluid, period, (never need it, too expensive, we were informed). The 320's wings glistened with frost and they wanted to board.

I explained that we could board and push but we wouldn't be departing right away as we had to "de-ice". By the time we got the airplane started the sun was up. I explained to the passengers that we were going to park for a few minutes before continuing.

I turned the airplane around with our back to the sun...

We departed after about 20 minutes, wings damp but all the frost was gone. I'll never forget the heck I got for the delay and the "technique". I guess not everyone had the alternative in full view during the early years.

[Mitch Cronin]

Fabulous picture Don.... Forgive me for the slug's pov, but I thank the lucky stars for any pilot (or AME for that matter) who can find that kind of courage to do what the more reckless wouldn't. .... and while I'm at my usual business of asking for a let here......

...

Have a good look at that photo.... and realize it's size... - as though you're standing beside it... and then, imagine Orville and Wilbur are suddenly standing with you ( never mind the magic, it's imaginary!)... ...Better yet, the three of you are standing on one wing a few feet outboard of the outboard engine... (it stills feels like you're standing on rock out there btw... even jumping won't produce a noticeable result - yep, I've tried) ... and now you're telling them the thing flies! ?? ...!! .... lol.... Sorry mate... it's just every time I've ever been around those beasts I've wondered what that would be like.... Would they believe you?

[Mizar]

Mizar

Take a moment and perhaps learn something about the type of aircraft you fly rather than playing pretend aero dynamist. Personally, I think you're beginning to sound like the kind of pilot that's going to make the news someday...and it won't be a pretty story!

I have to admit, that I don't understand your line of thinking. First of all, by relaying information to you which the NTSB has stated in their report is not "playing pretend Aerodynamist" It is what it is....reality. It is a passing of information by accident investigators to you that you were unaware of. This is the fourth time now that you have hinted that I am somehow dangerous. Knowing about the differences and effects of aerodynamics due to my reading of accident reports, and then enlightening you about this may in you opinion make me someone who is going to make the news someday but not likely in my opinion.

In reality, I would rather not go any further in the personal terms as you have. While I may do on that on political threads, this is a safety related thread. I would suggest that you analyze your reactions to having learned something here and perhaps consider it as beneficial to you and try to pass on your own safety knowledge here rather than the types of statements I quoted on this post and earlier as a reaction to safety board conclusions.

Knowledge is power, not dangerous. I will continue to read reports and pass on information. That keeps people from making the news.

[Mizar]

.

Interesting picture Don,

The Boeing plane would need to follow FAR121.629 No person may take off an aircraft when frost, ice, or snow is ADHERING to the wings, control surfaces, propellers, engine inlets, or other critical surfaces of the aircraft or when the takeoff would not be in compliance with paragraph © of this section. Takeoffs with frost under the wing in the area of the fuel tanks may be authorized by the Administrator. They may have justified it as snow is not adhering if it blows off.

When it is dry snow it will all blow off easily as the speed increases, or will it? I once landed for a few hours at a northern airport in a PT-6 powered aircraft. It was cold and snowing lightly. Looked like it could all blow off easily but took the broom to it anyways. Was quite surprised to find a bunch of ice near the engines below the snow on the wing. Engine exhaust had made the wing warm which melted snow which then froze.

Was only a small percentage of the wing covered in ice but still showed that ice can come as a surprise.

Also notice that engine inlets is covered by the FAR which do not believe is covered in the CARs

[Don Hudson]

I would have taken it for fluid had it not been for the sparkly bits that seemed to be breaking loose. As one can see, it was a clear day except for local fog.

On the CRJ video, do you see a bounce or two on what I believe to be the first attempt?

The consensus in some arenas is that the sharp manoeuvre that led to the crash is a bunt-like pitch driven by elevators and not a stall. I'm inclined to agree. Deployed spoilers generally cause a slight pitch up (if at all) at that point.

[JL]

Hey Don, maybe you could ask your aerodynamist friend the reasoning or technology development that has the more recently designed aircraft (A380, 787, A350, B747-8) not equipped with double or tripple slotted fowler flaps. They all appear to be a single element flap systems these days. (Sorry for getting off topic..) Weight savings perhaps?

[Don Hudson]

I think it's a good question, JL - I'll see what he has to say.

[blues deville]

Here's a good slat/no slat photo comparison.

http://www.airliners.net/photo/United-Express-(SkyWest/Canadair-CL-600-2B19-Regional/1164372/L/