As a helicopter pilot, I’m very interested in what happened to the Pave Hawk helicopter crash that occurred yesterday on Mt. Hood. (The news said it was a Pave Hawk. I didn’t get a good enough look.)
Most of the coverage I’ve seen shows the helicopter after it already lost control. Did anyone notice on the video what may have caused the crash? My first thought was that they struck the tail rotor, but all of the shots I’ve seen show the tail pointed downhill (as it should be). I didn’t notice the main rotor hitting the ground until after the helicopter was on its way down.
Of course it’s too early to tell what actually happened. At such a high altitude a power failure on one of the engines would cause the helicopter to crash. A tail rotor strike or transmission failure would also do it. But I was wondering if anyone saw anything on the video that led directly to the crash.
I saw it just lurch forward, crash and roll. I’ve seen tail rotor inceidents, and this looked way different.
A guy waiting to be rescued said, and I’m paraphrasing - 'before the helicopter crashed or looked like it was in trouble, I felt the downwash suddenly get much lighter…then it crashed…"
Yes, a sudden downdraft could force the helicopter down and the main rotor could hit the slope. I didn’t see that happen though, and I heard that the crew was able to release the guy on the cable before the helicopter went down. Of course, they could have had a downdraft and the pilot knew they were not going to be able to do anything about it, so they cut the guy loose then. From what little I saw, that looks like a possibility.
If they had a power failure they would have been able to maintain flight for a few seconds due to the large amount of inertia in the rotor system.
They did show another helicopter dumping fuel so that they would be light enough to perform a high alititude rescue. When you’re flying on the edge, things become more dangerous.
Pilots like to discuss crashes before all of the facts are in, and as you can see I’m no different. It’s still too early to tell just what happened, but I was curious if anyone saw anyting on the video that was an obvious cause.
I am not a helo pilot, nor any kind of pilot, but I have seen crashes with UH-1’s flying too low near a steep hillside in Vieques. As I understand it, the rotorwash did not give the propoer “ground effect” as it went downhill, and the Huey lost altitude sufficiently enough to unintentionally impact the terrain. Just slipped kinda sideways and back. No injuries (the pilots were both friends of mine), but we had a hangar queen for a six month cruise. It flew back to the ship slung unger a CH-53D, quite the sight. I have not seen the video, but if they were in near hover near the crevass, then suddenly got over the crevass, a similar outcome may have occurred.
According to this report the refueling probe hit the side of the mountain which led to the final crash, but he was apparently already losing control when that happened. They don’t seem to know yet what triggered the initial problem.
It’s been a bad week for climbers; first Mt. Ranier then Mt. Hood.
A big problem with high alt. helo work is that there isn’t much air there to beat on. The 'copters had to dump a lot of fuel to be light enough to make it to that altitude to help the stranded climbers. I don’t kow if this altitude was in that “small air” reigon, but it seems likely.
when there’s so little air to beat, any wind shift or change can be greatly maginfied as the helicopter requires more time to correct.
It’s been a bad week for fliers too. First the Taiwan Strait then Mt. Hood.
I’m not a pilot either but I don’t understand what ground effect would have to do with this. I thought the rotor blades provided lift all by themselves independent of any ground effect. Additionally, don’t you have to be really low to the ground for ground effect to work? I saw a huge uhmm…thing (not quite plane, not quite boat)…the Russians once built that was to be a transport that relied solely on ground effect. It barely lifted a few feet off the water it was flying over (the thing was never put into service). I wouldn’t think the rotors on a helicopter would experience much ground effect even if the helicopter was sitting on the ground.
Again, I know nothing about this stuff and am only speculating. I’m also not trying to call *UncleBill a liar. I just don’t understand this and hope someone can explain.
Re: Ground effect. Helicopters have hovering ceilings “in ground effect” and “out of ground effect” (IGE and OGE). You can be sure the Pave Hawk was within its OGE ceiling limit. I heard on NPR on the way to work that winds may have been a factor, so maybe Squink’s guess is right. The place where I rent helicopters lost one when a pilot came in too shallow for a pinnacle landing. He got into a strong downdraft on the lee side of the ridge and hit the slope. (No injuries, aside from a couple of bruises; but the aircraft was a total loss.)
The way I heard it explained was that when in proximity to a steep slope the backwash from the side closest to the slope can spin the helo around and over. Pretty much matches what I saw on the video.
The news reported the helicopter as a Pave Hawk, whose purpose is “to conduct day or night operations into hostile environments to recover downed aircrew or other isolated personnel…”
Kinda sorta what I was talking about, the downhill side of the craft has the normal OGE, while the uphill side can get backwash (or maybe an IGE situation?). The UH-1 slid sideways downhill.
The Huey was WAY too low, and again, I have not seen the Pave Hawk video.
You can see the whole video, from before the chopper loses control, here. Look a third down the page, in the box at the right, under “other links.”
It’s hard to tell – postage-stamp video, y’know – but the helicopter appears to be in a stable hover, then starts to execute a maneuver, wavers, and dumps fast. I’m not an expert, though.
When this fixed-wing pilot was watching the video (aside from going “ooo! oowie! yikes!”) my first thought was “it looks like a stall”, followed shortly by “I don’t know enough about rotorcraft to know if that’s possible at a hover” (I know about going to fast and getting a receeding blade stall, but in a hover you can’t be going to fast, can you?)
It looked to me like a loss of lift, however that might have happened - downdraft, engine problem, whatever - followed by a sort of wallow as the aircraft lost it’s grip on the air and started to fall, or at least descend rapidly.
After seeing the video provided by Cervaise, it looks like it was okay until it crossed to the lee side of the ridge where it caught a downdraft. As I said, the place where I rent lost an R-22 to a downdraft from a ridge; but that was a 160 h.p. (derated to 124) heli. If a downdraft took the H-60, it must have been a helluva wind. Or the heli was operating at its limits and didn’t have anything else to give.
The easy Q first: All H-60 variants are “X-hawk.” The basic (Army) model is the UH-60 Blackhawk used for utility missions. The PaveHawk is a special forces variant, named similarly to the H-53 PaveLow. (Not sure where the “Pave” part comes from, though.) The Navy has a couple of variants, the SH-60B Seahawk and the SH-60F OceanHawk. The coast guard flies the SH-60J JayHawk.
Lots of things could have caused the crash. I only saw the video once, but it looked to me like the nose kicked out to the right just as the helo started to lose control. This could be indicative of a tailrotor problem, although the departure was not nearly as violent as you typically see in a T/R problem. Losing one of the two engines could cause the problem, but I’d have expected to see the helo settle while yawing right.
The wind could have played a major role - I’m not an expert in mountain flying, but it is supposedly quite challenging. The altitude was certainly a contributing factor. The power requried to hover is significantly higher at 10-11 thousand feet than at sea level and that would have reduced the margins for error significantly. I’m not sure an SH-60B could even hover at that altitude, but its empty weight is several thousand pounds heavier than a PaveHawk.