stacee:
Yes indeed. As that characteristic was discovered about six decades ago (see Galaxy Flyer's point on the F-100), I think you will find that aerospace engineers have come up with a variety of ways to mitigate the problems of spanwise flow. Even as far back in history as the 1970's we were taught about slats, stall fences, et al.
I am not so sure.
As you are doubtless aware, washout isn't the only method used to mitigate for spanwise flow.
EDIT:
If you look at this picture
http://t0.gstatic.com/images?q=tbn:A...MC_qkyAgvf5Khp
you'll see one way that design engineers addressed that issue.
On a different scale in a fighter of a generation or two after the F-100 Galaxy Flyer pointed to, this picture shows the same basic idea at work:
http://t2.gstatic.com/images?q=tbn:A...Rcnc_P-OYxdAcQ

My less than gracious response to you suggested primary pitch control (and maybe I should have pointed specificallyl to longitudinal control authority) being a more likely source of the problem.

But we don't know. Hopefully, the FDR survived the crash.

LW, writes....
"As you are doubtless aware, washout isn't the only method used to mitigate for spanwise flow."

Washout has nothing to do with mitigating spanwise flow on a swept wing, its primary function is exactly the same as in an unswept wing, I.E. delaying tip stall by reducing the AoA the tip 'sees'

I did ask a question earlier,but it seems to have been deleted by someone...
Most aircraft exhibit a nose-down trim change when flaps are fully lowered,which may restore some more pitch authority.....Anyone care to comment,especially those who operate 744s..?

Thanks, Lone Ranger, I see what I did there. Been too long, mixing stuff up in the memory again. :ugh::ugh:

Did anyone address the possibility of a trim runaway?

Just out of curiosity.. How would these military vehicles be loaded? Would they be lashed onto a pallet with the pallet locked into position, Or loaded freely (bulk) and lashed to tie down points?

I only have experience in loading narrow body passenger aircraft. So have no idea how it works with cargo aircraft.

Sorry for a irrelevant question.

Video is both chilling and terrifying. Would make anyones blood run cold. RIP to the crew x

A review of AF 447 will show that AOA is relevant only to flight path of aircraft. This 747 was coming down at a very steep angle so to not be stalled would have to reference to this angle. We don't have the info at this point to know the cause but landing flat with a 60 degree descent angle still puts you in a deep stall.

Reminds all of us of that old maxim.

And it doesnt really matter why it happened or what sort of aircraft you are piloting.

If you get the nose too high, be it your fault or someone elses, a stall will follow. As sure as eggs are eggs.

Stall, spin, die.

No pilot should ever forget it- and I'm sure this crew never did.

Sometimes you are just fresh out of luck.:sad:

Dcoded: "Did anyone address the possibility of a trim runaway?"

Not likely. In the 747 there are two stab trim cutout switches just aft and to the right of the thrust levers. Corrective action would have been accomplished prior to the trim running away to the point that nose up trim would result in the witnessed accident.

Someone asked who was onboard.

News from The Associated Press

Pitch Trim runaway is one of many very unlikely possibilities, I would put money on a load shift. The boys didn't even have the opportunity to get the gear up before they were battling with the extreme nose up attitude.

The FDR will likely reveal the control input versus pitch attitude which should clear things up.

Watching this video sends chills up my spine. Prayers and condolences to the crew and their families. :(

A question and speculation
 

In a deep stall, will the horizontal tail (not a T-tail) see such an airflow that it tends to level the aircraft or even drop the nose? Is that what I see in the video?

If that is the case, then the (presumed) loose cargo which had shifted aft at rotation could be free to shift back forward - perhaps even beyond its original planned location - and exaggerating the nose drop.

I think, at this stage, all that needs to be said of this tragic accident was said in the first couple of pages, after that most of the professionals stood back and only posted thereafter to right a serious wrong. The rest of the thread consists almost entirely of speculation that ranges from highly educated to pure fantasy. MungoP's contribution is by far the most useful.

Can someone she light on this - would it take one of these vehicles to presumably cause this if it shifts position and therefore COG, two, more? Chain reaction where one hits the next which rips loose etc?

We need to hear what the CVR says and the ADC to get any real information. We know if pitched up for some reason but don't know why. Cargo shift or runaway trim could have caused it. We must wait for the black boxes to tell us.

Modern swept-wing aircraft DO NOT tip-stall first. Period. They are designed that way, with washout. Your earlier point that the nose will pitch up due to tip stalling in a modern jet is simply wrong.

Grimmrad: "Can someone she light on this - would it take one of these vehicles to presumably cause this if it shifts position and therefore COG, two, more? Chain reaction where one hits the next which rips loose etc?"

Reportedly, there were five MRADs on the aircraft. An MRAD weighs ~25,000#. Even in a 747, this would be a considerable load shift depending on the loaded location and the distance moved.

This occurred on a military base, so the Afghans are out of the investigative picture, I'm told. Let the NTSB review the evidence and announce the cause.

If i were a betting man, i would consider a steeper take-off profile combined with having 1 heavy vehicle coming loose from its hold downs and breaking the other(s) free. Lack of awareness on the load ratings of the hold-down points combined with "wear and tear" reducing the available hold down points structural strength would be high on my list

I'm trying to think of the simplest single reason for the loss. Does the 747 a take-off warning (like the A320) if power levers are advanced with stab trim outside of acceptable range?

To auto flight:

Yes a B744 has a TO config warning system warning for an incorrect stab setting.

1990 we flew 727's out of Managua, Nicaragua so did steep climbs and descents to get as high as possible knowing there were shoulder AA missles unaccounted for in the country. A Russian Mig base was on the north side of the lake by Managua. We should know soon if cargo shifted aft or trim caused this crash. It sounds very similar to the DC8 crash at MIA when the cargo slid back at high pitch attitude on take off. The DC8 didn't have the bear claws on the floor securing the cargo as I recall.

[QUOTE]I'm trying to think of the simplest single reason for the loss. Does the 747 a take-off warning (like the A320) if power levers are advanced with stab trim outside of acceptable range?/QUOTE]

Certainly the 737 does. I would imagine that it is a common feature across all Boeings. Having said that I would think that it a requirement for all public transport aircraft to have this alert as we can see the consequences can be catastrophic.

I don't need to have done stalls or spins in a 747 to see that the aircraft wing drops left, yaws massively to the right, wing drops to the right and loses height rapidly 'on a knife edge'. Who knows why they applied rudder but I do know that the technique taught is rudder to prevent further wing drop. It's my opinion that people over kill this technique. I won't be using rudder in a stall. I'm not touching it.

Having done stalls in the A320 sim with my company ( following the AF447 accident) I can tell you it requires alot more pitch down than a light aircraft, a very gentle recovery out of the nose down attitude to avoid a subsequent stall (which comes surprisingly easily) and an extension of slats helps alot. These were generally done 10000' and at high altitude.

Having what looks like such a high attitude stall in something with as high a mass as a 747 at this level must have been a nightmare.

Except if they didnt have time to realize that their ailerons are ineffective due to high alpha on the apex of the climb and the only way of getting this nose down was the rudder, or they would fall vertically straight down still with high pitch attitude.

On standard 747-400's, it depends on what data the pilots enter into the FMC (as per their loadsheets): Weight, thrust, CG, etc. i.e. Garbage in, garbage out.

However, prior to this, if the wrong data is entered, there is a chance it could be caught prior to takeoff. The aircraft does a rough check between entered data and the nose gear strut pressure. There is a pressure sensor which sends data to the alerting system. Strut pressure identifies aft or forward CG (roughly). An advisory message is generated if there is large discrepancy.

ALSO, on aircraft fitted with operative Weight & Balance systems (common on Freighters), computed weights and CG are displayed on the CDUs in small font for comparison with manual entries.

I wouldn't recommend using the ailerons either ( and I'm well aware that ailerons are ineffective and even reversed at very high alpha).
Lower the nose, unloading the G, roll the wings. Nevertheless I believe this was unrecoverable - so no slight on the crew. I remember I was taught early on by an examiner, having been taught by a 20 something instructor that regurgitated the text book technique to me - don't you touch that rudder in a stall! I don't fancy spinning today! You really have to know what you're doing. And I mean not spew out on pprune some quote written by a very capable test pilot - I mean practice these procedures in a type or similar at sensible timescales.

Whybyflier et al,

I believe the reason rudder is mentioned and used in some stall recovery methods, is because it is the yaw that develops at the point of stall due to the sudden increase in drag of that wing at the point of stall. The wing drop is normally the bit we as pilots see more visually. So rudder is used to prevent further yaw, not actually wing drop.

In this incident, we get a perfect view underneath the jet so we are not seeing it from a pilot's eye view. I would guess that if you look at any aircraft that stalls one wing first for what ever reason (rudder application, dirty wing, gust, aileron input etc) it would look like a massive yaw has developed from a pilot input.

So - although none of us know exactly what or wasn't applied in this event it seems to appear to me, for whatever reason (pilot induced or not) the right wing finally stalled causing a rapid yaw with resultant roll in the direction of yaw. . . basically a spin entry that due to the delightful 747 it briefly headed 'towards' a spiral dive which then self corrected? That perhaps more altitude may have given them a fighting chance . . . but there for the grace of god and all that.

However I am not a swept wing specialist so perhaps my straight wing stalling theory is flawed?

When the nose dropped would you not face the then problem of the load ( if that caused the problem) shifting fwd?

I think if you have a loose heavy load, all 'conjecture' is off?

LW50

TOC... the second wing drop is exceeding the normal aileron only roll max rate, for high aoa on the B744. If the roll off to starboard was from pilot input, it would be using rudder to give the roll, which would give the rate easily. The image doesn't give much help without pixel level evaluation to indicate the aileron position or the rudder position at the start of the roll off.

As for incipient spin, the aircraft has a roll rate initially to starboard, (at TOC) and then a yaw to starboard, but it has a roll then to port, with yaw reducing. The pitch rate is not a sustained pitch up, so I doubt that there is any inertial coupling going on, just some roll and yaw without extended coupling. The B74 has very benign handling normally, just needs half a chance and some altitude. (Last B744 type stall event at low level I am aware of was about a month before... not stability related, just environmental and crews with a SA/1 disconnect; lucky boys). These guys were faced with a catastrophic stability issue and in a time critical situation. We don't train this one, but it is a painfully possible event due to the functional resonance of socio-technological systems.

Agreed.

I think the video, sadly, shows a "departure from controlled flight" with probably little to no chance of recovery. I'm sure they did pretty much everything they could with the controls during the short period they were airborne but it ended in extreme AoA and high RoD.

A *recoverable* jet upset at high altitude is bad enough (see AF447) but, as is likely, having heavy cargo on the loose inside the fuselage at low level makes it non-surviveable, IMHO. It's a bit like making a paper dart that is aerodynamically unstable - no matter how fast or slow you throw it, it just flutters randomly to the ground. Cutting the engine power might possibly have helped slightly but who's to know?

fdr, thanks. I could not make out what the rudder was doing, I was trying to understand the right roll, and hadn't considered roll rate limitations. (DOH!) Thanks also on the incipient spin and inertial coupling points. :ok: Insofar as the wings being more or less level at impact, do you think (once the nose fell through) that sufficient control authority was restored to roll level using ailerons (roll rate limits considered)? :confused:

Well they are out of the picture, all right. But that is just because they happen to be a country occupied by american forces and have no say in anything, so...

Other than that, the international law is pretty clear here:
The accident occured within Afghan airspace/territory.
Furthermore this was a civil aircraft and not a military/state aircraft.
The investigation is therefore under the authority of the Afghans - read Art. 26 Chicago Convention.

In the unlikely case that an Afghan investigator should show up at the gates of Bagram airbase, they would have to let him in to do his job.

The question isn't what happened - it's why it happened. It is clear what happened - they stalled, wing dropped, they tried to balance it (secondary effect of left roll defo isn't right yaw), they had the spin entry and it crashed. No one knows what begun this sequence of events - they only think. My opinion is the application of rudder didn't help. At best it shortened the petrifying roller-coaster. They were able to roll and pitch before impact, clearly - you can see that, but it was too late. The beginnings of the spin sealed the deal. A 747 at take off has an eye watering amount of inertia, it takes time to do things. Once it was yawed right from that wing drop it was game over - the knife edge turn basically put it in free fall from 1200' with bugger all energy.

I got that. .
Also got that.

I still don't see how that's a spin, but I think I can piece together how what you are describing is similar to a spin entry. *scratches head* As the nose drops and the wings level, it appears, from what little we see, that it is still in a stall but it does not appear to be rotating about the vertical axis (again, the view may inform this impression) which is what I associate with a spin.

I think the situation was more basic than that: the aircraft hit the gorund going almost vertically down with hardly any forward speed. None of the flight controls would have been effective; it was a falling leaf. Quite possibly, if it had another couple of thousand feet under it, it would have wing-rocked again, ala AF447.

I think CaptAirProx has it right:

janeczku . . .
 

Well, not exactly, because the American Air Force Base is treated as "sovereign territory" type real estate, much in the same protocol as foreign embassies are. Afghan authorities may enter by invitation only.

Glueball: also, SOFA (status of forces) agreements address coordination with local authorities as part of that agreement. It's been some years since I saw the SOFA that included Bagram air base, pre Karzai, so I don't know what it looks like now. I do recall that if an Afghan civilian or military or police was injured/involved, or property damage, there were some protocols to handle cases with a joint investigation and adjudication of claims.
That's all memory provides at the moment.
We mostly let the JAGs handle that.

Which is most probably just an optical illusion due to the viewing angle and the distorted view through the windscreen. You can see the aircraft getting bigger quite rapidly, so although it seems to stand almost still, it was in fact moving fast. During impact you can see debris moving forward rapidly trailing burning fuel. Compared to the size of the fuselage they travel at least one fuselage length in a second, so some 100+ kt. Without forward speed the roll rate to level the wings would not have been possible either.

Please guys... Stop the drivel about stall, spin etc... Rudder here, rudder there, increase/decrease thrust bla bla bla..

If you end up with 80 degree nose up at 1200 ft in a 747 you are dead. No matter what you do.