Did the entire main rotor come off!?!
Ouch!
That looks a bit like the transmission came unglued. So the output shaft pulled out of the trans, leaving the rotor and shaft to flutter down while the fuselage and powerplant plummeted.
The fact the tail boom is missing suggests another cause. So called “mast bumping” which is a bit of a misnomer.
If the rotor disc is aggressively unloaded, the main rotors blades strongly flex downwards and can strike the tail rotor or tail boom. Which usually severs the boom and knocks off part of a main blade too. Which main rotor imbalance then thrashes the transmission apart or rips it right out of the fuselage. Plummeting ensues.
Unexpected turbulence encounters, instinctive evasive control inputs to avoid a collision, or basic hamfisted piloting are the usual causes of mast bumping.
IIRC you have X blocked so you probably can’t see this, but there’s also a vid of the helo behaving “erratically” shortly before the breakup:
So yeah, that seems plausible. Aggressive maneuvers (for unknown reason) lead to a mast bump, shearing off the tail boom and causing the other cascading failures you outline.
Scott Manley suggests (looking at ADS-B data) that the second video isn’t actually the same craft. Take that one with a grain of salt, then.
Your videos won’t play for me. I clicked the link, but there was no footage of the helicopter. (Just recovery efforts.)
I’ve never heard of that happening. The way it’s supposed to work is that in the event of a powerplant or transmission failure, the freewheeling unit (sprag clutch) disengages and lets the rotors to continue turning so you can autorotate to a safe landing.
Zero-G can definitely cause a boom chop. So can low rotor RPM. Ya gotta love that they use the word ‘doomed’.
DCA management may want to start considering exorcism.
There have to be more camera views of this that make it into the news. The city is filled with cameras. I’m wondering why the hand held videos were made? Was the helicopter doing something that made noise or looked dangerous enough for someone to get out their phone and start videoing the event? That’s going to take 5-10 seconds to get started.
They aren’t quite there yet:
I uploaded it to YouTube. Skipping the second video since it’s probably something else.
Maybe just “exorcizing” the name, Reagan, would be enough.
I did see the helicopter plummeting (one of my favourite words, ironically), but I didn’t see any ‘erratic’ flying before that.
There were two videos, the second of which showed erratic flying. But it was probably a completely different helicopter and taken at a different time. I didn’t repost that one.
Anyway, the YouTube version allows easier frame-by-frame stepping. The main rotor is still spinning in place as the rest of the craft is falling. Crazy that it separated that cleanly.
Well, you can see here that a substantial chunk of the transmission/swash plate assembly appears to have completely detached. I would have said that’s not possible before today’s events.
I guess we can’t blame the Jesus nut for that one. Unless the assembly is put together differently than I expect.
Substantially every passing aircraft is videoed by somebody. People like to take vids of aircraft. And with millions of people, there will be 3 or 4 vids of every completely ordinary flight. The tiny percentage of vids that are of flights that do turn weird will be submitted to the media or posted to Youtube.
A rule of thumb in our biz was that 100% of every flight is being video-ed by somebody.
I saw that upthread. I also saw nothing erratic. What I saw was the usual perspective distortions from a moving camera on the ground. And I saw the helo going into (or behind) clouds and re-emerging.
Nothing to see there.
I agree that is almost certainly not footage of the accident helo.
Yeah. That was exactly what I was basing my opinions on. Looks to me a bit more like some of the upper cowling around the swash plate, etc. Which I why I suggested the rotors shaft pulled out / parted and took some of the surrounding structure and skin stuff with it.
I wasn’t even trying to be snarky! “Jesus nut” might be slang but it’s a reasonably well-known name for the “main rotor retaining nut”. The thing is, despite the main rotor coming off apparently intact here (or nearly so), it seems like it also bought the swashplate, part of the mast, etc. with it. So it wasn’t the Jesus nut, but maybe another single-point-of-failure down the chain?
Another video, which shows some of the lead-in:
Appears to lose yaw control first, turning pretty hard to the right. Loses some debris a few seconds later–maybe the tail boom. And then the main rotor after that.
Apparently the Bell 206 has an unusual tail rotor drive shaft that’s glued together and has caused a number of accidents:
Nothing wrong with adhesive per-se, but there are a lot of segments and it’s not obvious that it can really be inspected properly. Doesn’t seem like a great design. A marginally less catastrophic accident here:
That does look exactly like a classic loss of control of, or loss of RPM to, the tail rotor. Once the tail rotor is ineffective due to whatever mechanical disruption, the fuselage starts spinning the opposite way to the main rotor. It ends up sideways to the airstream and pretty soon, like 1 or two revolutions, the tail boom fails in overload.
Meanwhile the fuselage plummets out of control. In this case the main rotor head and / or transmission did somehow tear out of the fuselage on the way down. But very clearly that was not the initiating failure; that was a late consequential failure that did nothing to alter the final gross outcome.
Back in USAF in one of my jobs I was part of a combined expeditionary force that among other things had USAF armed sorta-attack helos. (yep, not a well-known component of USAF. Not secret, just obscure.)
Anyhow as I was getting my introduction to USAF helo aviation the crews kept referring to various malfunctions that led to FGBS. I finally had to ask what FGBS was. “Flaming Green Ball of Shit”. As in that’s what the accident site looks like after the inevitable uncontrolled fuselage plummet. Unlike airplane crashes, there’s very little forward speed at impact; it’s almost always nearly vertical. Leaving a nice compact debris pile. FGBS.
Pave Hawk?
Mast bumping could certainly cause the rotor head to separate. It’s a known issue with semi-rigid (two blades, aka ‘teetering rotor’) helicopters.
So here’s where we are with the hypothesis:
- The tail rotor fails.
- The pilot is late initiating emergency procedures (immediately enter autorotation) or takes incorrect emergency actions.
- The pilot loses control of the aircraft, which results in a mast-bumping incident that causes a boom chop and rotor separation.