Videos Of Challenger 600 Crash In Aspen Colorado


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I've resisted the temptation to post on this forum for some time. This thread however warrants an exception. Don, of all the people I know, I think you rank among the most humble, yet knowledgeable.

Actually, one might reasonably paraphrase Mizar's more recent posts as follows: "I have my opinion which I have strenuously expressed and I am not about to change that opinion. I stand ready to ration

Mac Davis wrote this: Oh Lord it's hard to be humble when you're perfect in every way. I can't wait to look in the mirror cause I get better loking each day. To know me is to love me I must b

Slats are designed to keep the boundary layer attached to the wing at high angles of attack nothing more. This is to assist in low speed handling. Slots are designed for the same thing although not used much anymore. If the wing surface is contaminated then this will cause boundary layer separation at the same angle of attack. Without slats the same hold true,the boundary layer will separate at a lower AOA than an uncontaminated wing. The limits for both types are built into the design. neither is "Safer" than the other.

If an uncontaminated, Slat Equipped wing stalls at 25 deg AOA then the same wing contaminated will stall before that angle is reached.

if an uncontaminated NON slat equipped wing stall at 20 degrees then the same wing contaminated will stall before that angle is reached

So neither design holds a safer margin for error they are just different. Yes the wing with no slats will stall earlier (normally) but that is built into the design.

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Defcon, the writer's opinion that I provided was not my own but a point to start a dialogue...which it did! What should be questioned is the "myth" and what/how much contamination is being considered. Too many variables I believe to lump into one determination that leading edge devices improve a wings performane with contamination. From frost to residual ice on leading edges to snow covering an entire wing, these will all have different effects on the airfoil and whether a leading edge device will help or not it impossible to say for every scenario. Leading edge devices do improve lift/drag performance, but due to the infinate variables involved in wing contamination it would be ill advised to wrap oneself in a perception that leading edge devices provide the same level of protection as a good dose of type I and type IV. (Sorry, I am preaching to the choir.)

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Mizar

You could post your engineering qualifications to support your contention that you know more than NASA and the expert I didn't name, but you won't, I'm sure.

Now granted, I haven't paid much attention to anything related to aerodynamics for quite some time now and things may have changed in this respect, but I doubt it. It's sad and maybe even a little humourous, but your comparison of wing susceptibility to the effects of contamination between swept wing slatted aircraft and their non-slatted cousins isn't any different than that held and proffered early in the CALPA meeting I previously referred to. It's scary to note that although twenty-five years has passed some mortifying aspects of pilot thinking haven't changed at all.

Take a look at the DC 9 - 10, 15, or 20 versus the 30. The first three types are un-slatted although the wing is similar amongst all four variants. I'll bet my last penny that Douglas didn't add slats to the '30' to provide a safety advantage when operating with contaminated wings. Slats add weight, mechanical complexity and cost to an aircraft. Slats are only there because a particular aircraft design requires them for reasons that definitely do not include performance enhancement with contaminated wings.

Although I could likely reference and display a technical source here, the 'fine detail' aerodynamic rationale for the inclusion of slats is beyond my pay grade and so, I have chosen to simply go along blindly and accept the rule; don't attempt take-off with contaminated wings.

JL - Thanks; your reference to the variable nature of wing contamination is right on the mark. The unpredictability of form makes it quite impossible to qualify, or quantify the degree of degradation a given airfoil may suffer in a particular circumstance. For this reason, 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.

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PS

I took a quick look and found the following Bombardier document on the subject being discussed.

"Wind tunnel and flight test data confirm that both 'hard' winged and slatted A/C stall at reduced AOA when the wing leading edges are contaminated.

At the same scale the reduction of stall AOA are similar."

The document can be found at:

http://www.sae.org/events/icing/presentations/2007s1tanner.pdf

I'm not having any luck getting the complete link to stick here?

The relative parts here are spaced out to achieve the objective.

sae.org / events / icing / presentations / 2007s1tanner.pdf

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PS

I took a quick look and found the following Bombardier document on the subject being discussed.

"Wind tunnel and flight test data confirm that both 'hard' winged and slatted A/C stall at reduced AOA when the wing leading edges are contaminated.

At the same scale the reduction of stall AOA are similar."

The document can be found at:

http://www.sae.org/events/icing/presentations/2007s1tanner.pdf

I'm not having any luck getting the complete link to stick here?

The relative parts here are spaced out to achieve the objective.

sae.org / events / icing / presentations / 2007s1tanner.pdf

When you enter a 'link' in your reply or even an initial post the " forum mechanism" automatically shortens it... ....your entire link was in your post even though your post made it look like there was a missing part of your link. :excl:

If you want to make sure the entire link is there.....right click on the link ,click on PROPERTIES, (new little window opens), and voila, there is your link. :Grin-Nod:

Ain' technology grande ?! :103:

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When I was working on the Global Express program we were testing an automatic anti icing system. At the time the system was not certified for operation in service. The system used the ice detection system to trigger the anti icing valves to open and heat the leading edges. This system would reduce this kind of incident if in fact contamination was an issue.

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Boestar

As I recall; safety considerations require automatic detectors to be far too conservative and as such, they unnecessarily consume to much in the way of fuel & maintenance resources. An experienced and well trained pilot remains the best detector available.

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Boestar

An experienced and well trained pilot remains the best detector available.

Years ago, we had a Goodrich detector on the PoS we called the Jetstream 41. I'll never forget landing after a two hour flight in light freezing precipitation with no warnings, the 1/4" of pure, milky white rime ice on the probe. We had a similar probe on some of the 757/767s I used to fly as well.

Nothing replaces the Mk I Noggin when it comes to stuff like this...

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Mizar

You could post your engineering qualifications to support your contention that you know more than NASA and the expert I didn't name, but you won't, I'm sure.

Now granted, I haven't paid much attention to anything related to aerodynamics for quite some time now and things may have changed in this respect, but I doubt it. It's sad and maybe even a little humourous, but your comparison of wing susceptibility to the effects of contamination between swept wing slatted aircraft and their non-slatted cousins isn't any different than that held and proffered early in the CALPA meeting I previously referred to. It's scary to note that although twenty-five years has passed some mortifying aspects of pilot thinking haven't changed at all.

Take a look at the DC 9 - 10, 15, or 20 versus the 30. The first three types are un-slatted although the wing is similar amongst all four variants. I'll bet my last penny that Douglas didn't add slats to the '30' to provide a safety advantage when operating with contaminated wings. Slats add weight, mechanical complexity and cost to an aircraft. Slats are only there because a particular aircraft design requires them for reasons that definitely do not include performance enhancement with contaminated wings.

To be clear, I follow the procedures for de-icing contaminated wings. I would likely be fired if I didnt and it makes sense to do so. My only point is once again, to state what I know to be fact. That non-slatted swept wings are much more vulnerable to wing contamination than the slatted types.

I do not have any engineering experience. Why do I need to have engineering experience to be knowledgeable about such things. Your engineers and NASA folks were either lying to put extra fear in you with the benefit of getting the overall important message out to always de-ice or they were not knowledgeable about the facts. Name me one slatted airliner that crashed because of loss of lift due to wing contamination. The only one you will likely come up with is the AF 737 in DC which was trying to climb out at a low power setting due to other mistakes made.

Douglas probably added slats to their larger DC-9s as a way to increase performance as the overall with the tradeoff in system weight and complexity became worth the investment as it grew larger. That reality doesnt change what I have said. The increased safety margin was just a nice bonus.

How many slatted DC-9s have had wing contamination accidents due to loss of lift.

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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?

You have often demanded that others here produce evidence in support of their contentions. In the present case, it's your turn to back up your assertions with more than personal belief Mizar.

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Considering that I have said twice that we should get de-iced, I dont know why you keep making these sort of 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?

The bottom line is that unlike the old days, you can pretty much expect that in the airline world we live in that de-icing is getting done.

You have blindly followed misinformation and get de-iced. I am more knowledgeable on the subject and get de-iced. The end result is the same. We get de-iced. So the system is safe in our worlds.

But, it is not a dangerous position or arrogance to understand aerodynamics better which is what I have done. Remember, I am not saying that it is safe to takeoff with contamination. What I am saying is that non-slatted swept wings are much more vulerable to small amounts of contamination.

There is another reality outside the warm cockpits of our mainline world. There is the way things get done in more remote areas. Approaches are not ILS to ILS and facilities are not as they are in the white collar world. Certain realities happen even though they are not legal. Someone with inexperience may experience something and then try to apply it it the future when they shouldnt. They may have flown an aircraft with an experienced guy with a bit of contamination and they were successful. They may have done it for years and thought that they could always get away with it because they always had gotten away with it. The something tragic happens.

One has to ask themselves something. Why on earth would that Air Ontaio F28 captain have been foolish enough to take off from Dryden with contaminated wings. If he knew his jet aerodynamics, he would have known that he would likely die. So why did he do it. Because he had done it plenty of times before in different aircraft. So he thought he could apply the same thing again. As a new commercial pilot at the time, even I was well aware that this was foolish as soon as I heard what he had done. Why do you ask. Not because I am any smarter than anyone else but I was prudent enough to read accident reports. A lot of them. And I had learned that old DC-9s, F28s, etc(non-slatted jets) were more vulnerable. Based on the reality of the high number of accidents. I hope I dont have to list them to convince you.

My only point in all this is not to encourage people to takeoff with contaminated wings. It is to pass on that for those out there who have done so and therefore continue to think that because it worked in the past, it will work under different circumstances in the future ferrying an RJ or similar aircraft out of a remote area and are tempted to go when no de-ice is available, you may get a big surprise. Posting your statements quoted above is not helpful to the process.

While I know I could post a study proving your so-called engineers were wrong, why bother, the stats are the proof.

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Thanks Malcolm. The most important statement made in your link is this:

Slatted aircraft have high C/L max:

Slatted A/C Aerodynamics: Slatted A/C have high CLMAX:-The percentagereduction of lift due to a given reduction of stall AOA is less on a slatted A/C than on a “hard”winged A/C.

Which is the reason I have been saying what I have been saying. Which is the reason the accidents of the past are what they are.

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you should also consider the information following the quote you captured:

Possible Contributing Factors –For Discussion.

•Aircraft Design:-Geometry Limit:-Due to the high operating attitudes of slatted A/C some are geometry (tail strike) limited.

Take-off speeds may be increased due to increase of Vmu.

-Large A/C typically have fully powered irreversible flight controls.-Large turbojet (slatted) A/C have fully evaporative hot air wing anti-ice systems.

-Large A/C typically have onboard ice detection systems

Flight Operations:-Large airlines operate the majority of slatted A/C:-Detailed SOPs and sophisticated flight operations and training departments.-Generally operate from large airports that possess state-ofthe-art weather reporting, runway de-icing and clearance equipment and A/C de-icing equipment

Regarding the other points you listed from the link,

There are no significant tailstrike issues on the old 737-200(unless you really, really work at it), yet if you compare the 737-200 vs the old short-body DC-9 with no slats, the hard wing DC-9s were crashing a whole lot more due to wing contamination.

If you compare the old hardwing DC-9 with the slatted stretch DC-9, neither had fully powered irreversible controls(except the rudder perhaps) yet only the hardwing versions have the high accident rate due to contamination.

If you compare the old hardwing DC-9s which crashed a lot due to contamination issues and the stretch which had a much better record, I think youll find similar wing anti-ice systems, which is likely irrelevant anyways as most aircraft are not allowed to use their wing anti-ice systems on the ground and most contamination accidents happen on takeoff.

Considering an ice detection system makes no sense to me. An ice detection systems is an inflight system(for the aircraft I have flown anyways), so it is not relevent to crashes due to ice contamination which almost always happens on takeoff.

Concerning airline SOPs, many of the hardwing accidents occurred at major airlines such as TWA, Continental, USAir, and ABEX. But it didnt occur on their slatted aircraft.

In other words, the issue remaining is the one I posted earlier,

Slatted aircraft have high C/L max:

Slatted A/C Aerodynamics: Slatted A/C have high CLMAX:-The percentagereduction of lift due to a given reduction of stall AOA is less on a slatted A/C than on a “hard”winged A/C.

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Actually, one might reasonably paraphrase Mizar's more recent posts as follows:

"I have my opinion which I have strenuously expressed and I am not about to change that opinion. I stand ready to rationalize that opinion in the face of any contradictory fact."

Mizar....all are agreed that one ought not to attempt operation with contaminated wings. It is of no relevance therefore whether slotted is less susceptible to the consequences of contamination than un-slotted. The argument is akin to one where the dispute is as to whether the fatal injuries sustained in a 100 mph accident in a Porsche are less severe that the fatal injuries sustained at 100 mph in a Ford.

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I posted the results of a definitive study, the only one I could find that examined the two types of wings re contamination, Your rebuttal is antidotal at best.

So if I posted my rebuttal as some sort of a definitive study then it would be the final word. Read what you posted on the study and read what I wrote in response carefully. I have shown that the study is not exactly accurate. It may be accurate for already inflight operations but as you can see it makes no sense for takeoff operations.

I could study the accidents and compare and the write a paper about it. Would that all of a sudden make you believe it. Can one not individually come to valid conclusions based on real world experience.

And I have to admit that I really dont know what you mean by antidotal.

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

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

Mac Davis wrote this:

Oh Lord it's hard to be humble

when you're perfect in every way.

I can't wait to look in the mirror

cause I get better loking each day.

To know me is to love me

I must be a hell of a man.

Oh Lord it's hard to be humble

but I'm doing the best that I can.

I used to have a girlfriend

but she just couldn't compete

with all of these love starved women

who keep clamoring at my feet.

Well I prob'ly could find me another

but I guess they're all in awe of me.

Who cares, I never get lonesome

cause I treasure my own company.

Oh Lord it's hard to be humble

when you're perfect in every way,

I can't wait to look in the mirror

cause I get better looking each day

To know me is to love me

I must be a hell of a man.

Oh Lord it's hard to be humble

but I'm doing the best that I can.

I guess you could say I'm a loner,

a cowboy outlaw tough and proud.

I could have lots of friends if I want to

but then I wouldn't stand out from the crowd.

Some folks say that I'm egotistical.

Hell, I don't even know what that means.

I guess it has something to do with the way that I

fill out my skin tight blue jeans.

Oh Lord it's hard to be humble

when you're perfect in every way,

I can't wait to look in the mirror

cause I get better looking each day

To know me is to love me

I must be a hell of a man.

Oh Lord it's hard to be humble

but I'm doing the best that I can.

We're doing the best that we can

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It appears that my statements here on a safety issue have triggered some interesting responses from various posters so I will respond based on my intention to provide some important safety information for those who might be tempted to try something because they have gotten away with it before and the importance of trying to learn as much as possible from all sources in world where we may be given conflicting information on the same subject. Then I will make a further post to back up my earlier statements.To respond:

DEFCON: I appreciate your approach to safety and your professionalism. I still stand by what I said about the people who misinformed you. This is a quote from an article that I will link in my next post.“The FAA has a concern about the effects of advising pilots that non-slatted airplanes are more sensitive to wing ice contamination. It is believed that if non-slatted wings are singled out, pilots will feel that a minute amount of ice is acceptable on slatted wing airplanes.“ This explains why your experts say what they say about no difference. They have a message to send and analysis should not enter the process.

Boestar: I see what you are saying but I gave an example on page two of what can happen in large parts of the world where facilities are not what we are used to. It is a warning to those who might want to tempt fate based on the fact that they have done it before.

Malcolm: I am posting a link to the type of study-report that you feel is so important to confirm what I have said. Please keep in mind that there are endless reports and it is not uncommon to have conflicting reports on the same subject as seems to be the norm about things such as what is good for you to eat. If you really believe that some sort of peer type report makes a study the final answer, you must be a hard core man-made global warming supporter all of a sudden. That being said, I think the writers of the report below are credible.

Kip: I always think of guys like you and Don as much more knowledgable than myself in most of aviation just because I am certain about this doesn't change my opinion of you guys and many others.

[post edited by PowerAdmin - deleted objectionable comments]

Edited by PowerAdmin
post edited by PowerAdmin - deleted objectionable comments
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I mentioned earlier about the differences between slatted and non-slatted swept wing aircraft on this thread. These quotes are from the National Transportation Safety Board accident report on USAir 405 at La Guardia quite a few years ago.

While a very thin film of ice or frost will degrade the aerodynamic performance of any airplane, the Safety Board believes that the aerodynamic characteristics, as well as the accident record, indicate a need for special attention to be given to transport jet airplanes that do not have leading edge devices for lift enhancement during takeoff.

The following is a general description of the effect of leading edge high lift devices, such as slats:

An important (or predominant) limitation of lift to be obtained in wings, is flow separation from the leading edge. Means of preventing or postponing such separation are, the use of leading edge slots or slats, camber or the deflection of nose flaps, and boundary-layer control (blowing or by suction). These devices are used to increase the maximum lift and/or to prevent stalling from the wing tips, thus preserving lateral (aileron) control. All types of leading-edge lift-increasing devices function by increasing the angle of attack where stall takes place. They thus control separation, while lift (circulation) is basically controlled by the position of the trailing edge (by angle of attack, with or without a flap).

Like the F-28, the DC-9-10-series airplane has a fixed leading edge wing. Douglas Aircraft Company has found that the fixed leading edge wing is more susceptible to lift degradation due to ice, frost, or snow than a similar wing with extended leading edge slats. The following description of this finding is from an article published by Douglas Aircraft Company:

These [wing roughness] effects are particularly important for early transport aircraft having no leading edge devices. Extension of the leading edge devices of more advanced aircraft will generally recover most of the stall speed degradation resulting from the low levels of roughness cited here. Although the low levels of roughness cited by Douglas are generally less than the roughness level expected to cause an accident, possible aerodynamic degradation is especially critical during takeoff since the AOA margin from stall is less than at any other regular phase of flight."

The accident report further states

"….the critical factor in ice contamination is how close the takeoff maneuver gets the wing to its stall AOA. In this case, the fixed leading edge wing apparently has less margin of safety than the slatted wing, even if it is assumed that the percentage lift loss due to ice contamination is the same for both wings.

During the takeoff maneuver, it takes longer to rotate the slatted airplane to a stall attitude so that the slatted airplane has time to climb and accelerate. Because airplanes with leading edge slats normally stall at a higher AOA, the risk of an AOA overshoot into the stall region is lower than it is for a fixed leading edge airplane. The combination of more altitude, higher speed, and enhanced roll control increases the likelihood of a successful takeoff when the upper surface of a slatted wing is contaminated with a minimal amount of ice. Further, airworthiness requirements are based on a safe climb speed (V2) that is at least 20-percent above the stalling speed.

Because the slatted wing creates lift over a broader range of AOA, a 20-percent margin in speed provides a slightly larger AOA margin before wing stall, typically a 1.5- to 2.0-degree greater margin between the AOA at V2 and the stall AOA.

Other important statements in the report concerning the issue at hand.

There are far fewer non-slatted airplanes operating under 14 CFR Part 121, but they have experienced almost all of the takeoff accidents attributed to wing upper surface ice contamination.

“The FAA has a concern about the effects of advising pilots that non-slatted airplanes are more sensitive to wing ice contamination. It is believed that if non-slatted wings are singled out, pilots will feel that a minute amount of ice is acceptable on slatted wing airplanes.“

http://www.airdisaster.com/reports/ntsb/AAR93-02.pdf

I can only hope that this might convince people that a small statement made early in the thread(which somehow morphed into something much more) is correct.

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