150 feet, guys. 150 feet.
Unctuous, great post! I agree with everything you wrote.
Based on the accident report, here's what I think happened. And let's remember, this flight was a dynamic situation. It's hard to take "snapshots" of any one point in the approach and draw hard and fast conclusions. Things were happening- and things were happening fast. (And also remember that the whole operation was being filmed by the V-22's themselves, as well as aircraft that were circling overhead. Images from these cameras were relayed back to various places in real time.)
So at the 3.0 mile DP (deceleration point), the V-22 was 100 feet too high and 20 knots too fast (going an astonishing 270 knots across the ground). They should have started decelerating there, but did not - not for another 1/2 mile. At 270 knots GS, that 1/2 mile would have been covered in...what...10 seconds? Less?
Anyway, at around 2.5 miles from the LZ they began slowing down and converting back to helicopter mode. With only .79 miles to go they were at 150 feet (still too high) and 147 knots airspeed. By 1/2 mile they were down to 115 knots indicated (128 kts GS).
Okay, stop right here. 115 knots in a V-22 in helicopter mode? I can see that in a Huey, which has generous flapping capability in the rotor, but isn't that just a tad fast for a proprotor-equipped V-22? I ask this because here is what the V-22 AFM says about landing after a dual engine failure in forward flight. First of all, they call for a fast conversion back to helicopter mode and a target speed of 110 knots.
Note:
Expect large pitching transients and NR decay during reconversion due to edgewise flow through the rotor system.
Expect 4000-5000 fpm rate of descent. Glide ratio is 2:1.
Expect loss of flare effectiveness as wing stalls. Plan approach
for 50-60 KCAS at touchdown.
Okay, the V-22 in Afghanistan did not suffer a dual engine failure. But the AFM note is enlightening. When you're going fast and convert back to helicopter mode, strange things happen- i.e. those "large pitching transients." The accident aircraft in Afghanistan was going around 230 knots when they began their conversion, deceleration and descent. And remember, they were only 300 feet from the ground.
At 1/2 mile they were at 150 feet, still doing 115 knots. And here is where it all came undone. The MP (mishap pilot) was undoubtedly working hard, trying to get that big bastard slowed down. For some reason he allowed a rate of descent to build up. Reports say it may have been as high as 1800 fpm downward. From 150 feet. Okay, momentarily as high as 1800 fpm because they did not hit the ground at that rate of descent.
Okay, stop again. You know, we've all been there. We've all be at the bottom of a really messed-up approach. You get to a point where you finally wake up and go, "Damn! This isn't working out, let's get out of here." And you go! You pull pitch and - depending on whether you're above or below ETL - you either pull or push on the cyclic. "Come on, fly darlin'."
I think that once the V-22 began that descent there simply wasn't enough power in the engines or proprotors to stop it. That thing weighed nearly 45,000 pounds at that point. That's a lot of momentum coming down at 1800 fpm. And all it had for support were those tiny little, highly-loaded proprotors. I'll bet that the MP did recognize how screwed up the approach was, and applied every bit of power he had in trying to make that go-around. From 115 (or 100 or even 75) knots it should have been cake. But there just wasn't the lift reserve left to pull it off.
No VRS.
No brownout.
Just a classic case of SWP. Or settling-with-power, V-22-style.
Why is this important? Why do we obsess over this so? Because very simply, it will happen again. And again. The USAF and USMC are trying to make the Osprey do something for which it is particularly ill-suited.
You don't have to be master V-22 pilots to understand this. Most of you guys are probably helicopter pilots- you intuitively and thoroughly understand how helicopters fly. You know about things like inertia and momentum, and the importance of not putting the aircraft into a position from which it cannot escape. You listen to the military pilots say that the V-22 *can* make fast, helicopter-type approaches into a hot LZ, but you know with every fiber of your being that it's very risky. Dangerous, even.
You know this.
But we've had this "magical" V-22 shoved down our throats. And it keeps killing people. In Afghanistan, it killed four people in April of 2010 when the pilot misjudged what should have been a "simple" straight-in, night approach to an undefended LZ. And again let it be said that this pilot was widely regarded as one of the best V-22 pilots in the Air Force. And even he screwed up. I wonder if mcpave and ospreydriver both privately feel that they are better pilots than the MP? I wonder if they privately feel that they wouldn't have screwed up like that?
Ospreydriver feels that since we've already got the V-22, then we should just accept it. I guess he would also advise a rape victim that if it's inevitable, do not resist but just lay back and enjoy it. No, we should fight! We should fight to get the V-22 canceled, as it should have been from the start. We should continue to fight to stop wasting money on this pig.
Here in the U.S., our new mostly-Republican House of Representatives has vowed that they will cut spending! and help reduce our astonishing deficit. They could start by replacing the V-22s with CH/MH-53s. That would not only save a lot of money, it would save a lot of lives.
(Oh, and speaking of the deficit, one final note to helonorth: You said, "BTW, I believe the US deficit is 13-14 trillion." Son, in class this week, perhaps you could ask your high school teachers to explain the difference between "debt" and "deficit," for you obviously don't understand it. I'm not surprised. You want to be a helicopter pilot, after all, right? Sadly, it is a problem of limited intelligence that afflicts so many in our field. You'll fit right in!)