Seal Team Six Helicopter Crash 5/1

[tj8888]

As I guess everyone knows, during the Bin Laden raid the Seal's stealth helicopter crashed. Several things were offered as possible reasons: the stealth modifications altered the flight characteristics in unpredictable ways, it was more humid or hot than they expected, and that the high walls of the compound resulted in the helicopter losing lift (the most common explanation).

I'm just wondering if the high wall explanation makes sense from a physics perspective. I assume I'm missing something because to me I'd think trapping the air with high walls would increase lift. I mean if we imagine walls so high that a helicopter is completely surrounded by an enclosure with an open top I'd think that would help with the lift even more.

if I'm wrong can someone explain this to me?

 

[turbo]

Just speculation, but if the main rotor started pumping its air into an enclosure resulting in a sudden increase in lift, could the tail have dropped and hit the wall?

 

[pallidin]

I assume they didn't hit a power line or some type of purposeful aerial wire obstruction?? Has that been ruled out?

Reason I ask: I heard that, during the Vietnam conflict, the NK's would sometimes put wire cables in-between tree's to fatally snag US helicopters coming in for covert landing or low-alttitude drop-off of personel/equipment.

 

[russ_watters]

Just speculation, but if the main rotor started pumping its air into an enclosure resulting in a sudden increase in lift, could the tail have dropped and hit the wall?

I think it is better to look at it from the opposite direction: if the main rotor started pumping air into an enclosure, resulting in a sudden increase in lift, the main body would decrease its rate of decent, with the net result on attitude being a pitch-up...but if the helicopter decreases its rate of decent without the tail actually dropping faster, that implies an overshoot of the landing spot, not an undershoot.

 

[Drakkith]

I haven't really heard anything about this. I'm assuming that enemy fire was ruled out?

 

[Vespa71]

Just speculation, but if the main rotor started pumping its air into an enclosure resulting in a sudden increase in lift, could the tail have dropped and hit the wall?

Providing this is a single lift-rotor aircraft, main rotor center is close to center of mass, so tail-lift shouldn't be affected. However, tail-rotor can get "horizontal lift" from nearby wall, causing rotation to aircraft. If helicopter descended close to one wall, there could be asymmetrical lift to main rotor, also causing reduced control.

Generally it is difficult to land a helicopter on a small area if windspeeds vary. Here, because of the walls, the helicopter will make it's own unpredictable winds. Throwing up dust inside walls (opposed to throwing away air/dust horizontally) can reduce visibility, reducing corrective control.

 

[johnbergstromslc]

Keep in mind that this was an experimental, stealth helicopter. It's doubtful it flies as well or is as stable as a normal military helicopter. (The F-117 stealth fighter would crash and burn if not for continuous computer control and is purposely limited in the manuevers it can do).

Also, it was operating in high altitude and the pilot probably pushed the envelope a little too hard...

 

[pallidin]

Keep in mind that this was an experimental, stealth helicopter. It's doubtful it flies as well or is as stable as a normal military helicopter. (The F-117 stealth fighter would crash and burn if not for continuous computer control and is purposely limited in the manuevers it can do).

Also, it was operating in high altitude and the pilot probably pushed the envelope a little too hard...

Special Operation Forces do not use "experimental" anything dealing with high-value targets in an actual operation.
Just so you know...

 

[Drakkith]

Keep in mind that this was an experimental, stealth helicopter. It's doubtful it flies as well or is as stable as a normal military helicopter. (The F-117 stealth fighter would crash and burn if not for continuous computer control and is purposely limited in the manuevers it can do).

Also, it was operating in high altitude and the pilot probably pushed the envelope a little too hard...

Modern jet fighters are computer controlled. The F117 is much older, designed differently, and was never designed to dogfight anyways. I am more inclined to agree with pallidin.
Also, was damage sustained from enemy fire ruled out?

 

[Ranger Mike]

Having some experience in these things...( as the R word may hint in my name..) I can tell you one thing that is absolute fact.
Rehearsal ,,,and i am talking about full dress rehearsal do to live ammo, and EVERY detail as would be actual case...was conducted on an EXACT replica of the compound...not once but dozens of times...portions of the entire sequence were run and re-run until it became second nature to each assault team member. These live fIre rehearsals INCLUDED the chopper pilot tasked to do the flying on the actual day..it is highly unlikely that pilot error was the cause and the attention to detail of the target compound would eliminate the team being caught unawares regarding lack of lift...everything that can be anticipated was taken into account as well as all possibilities of what could go wrong..thats why they did have a back up plan on air evac...and they had two more back up plans should that have failed...

 

[cjl]

The F117 is much older, designed differently, and was never designed to dogfight anyways.

And fully computerized nonetheless. It's hideously unstable in all three axes.

(I agree that they would not have used any experimental stuff on this kind of an operation though)

 

[Drakkith]

And fully computerized nonetheless. It's hideously unstable in all three axes.

Where you pointing something out in my post that was incorrect or misunderstood?

 

[BruceW]

Having some experience in these things...( as the R word may hint in my name..) I can tell you one thing that is absolute fact.
Rehearsal ,,,and i am talking about full dress rehearsal do to live ammo, and EVERY detail as would be actual case...was conducted on an EXACT replica of the compound...not once but dozens of times...portions of the entire sequence were run and re-run until it became second nature to each assault team member. These live fIre rehearsals INCLUDED the chopper pilot tasked to do the flying on the actual day..it is highly unlikely that pilot error was the cause and the attention to detail of the target compound would eliminate the team being caught unawares regarding lack of lift...everything that can be anticipated was taken into account as well as all possibilities of what could go wrong..thats why they did have a back up plan on air evac...and they had two more back up plans should that have failed...

Incredible, Its not like operations during the world wars, they actually have the time to rehearse and plan everything to the last detail

 

[Drakkith]

Incredible, Its not like operations during the world wars, they actually have the time to rehearse and plan everything to the last detail

Yep. Completely different type of conflict!

 

[cjl]

Where you pointing something out in my post that was incorrect or misunderstood?

Your post could have been interpreted as stating that the F117 was not computer controlled, since you seemed to contrast modern jet fighters (which you described specifically as being "computer controlled") with the older F117. I was merely making sure there wasn't a misunderstanding.

 

[Drakkith]

Your post could have been interpreted as stating that the F117 was not computer controlled, since you seemed to contrast modern jet fighters (which you described specifically as being "computer controlled") with the older F117. I was merely making sure there wasn't a misunderstanding.

Ah, I see. I was merely pointing out that many modern fighters are computer controlled and can pull some crazy maneuvers.

 

[cjl]

...many modern fighters are computer controlled and can pull some crazy maneuvers.

Very true

 

[pallidin]

Having a radar signiture less than that of a large bird, steath-tech allows inderdiction in conflict areas seemingly impossible.