Japanese AH-64 crash in Kanzaki, 5/2/2018
 

Appears to have crashed into a residential area with the loss of the crew; hopefully no one on the ground injured:

At least two dead as Japanese military helicopter crashes into residential neighbourhood

Sorry, behind paywall.

Condolences for all aboard. These planes were built by Fuji ind under license. They came out as advanced block II, but I think they were upgraded to block III not long ago, with composite rotor blades. Way back in the 80s I was stationed at Futenma, we were supposed to have some joint exercises with JDF marines, and air cover but someone further up the food chain nixed it. They don't have a stellar record of safety. However, just as likely the plane let them down at this point.

Viewing the news here it seems it had been in for repairs and was on a final test run. Witnesses heard a rough noise from the rotor and saw parts falling off in the final three seconds as it ‘nose-dived’.

Oops, I should have read this article first!
https://japantoday.com/category/nati...l-area-in-Saga

Newly replaced main rotor head detached just prior to crash?
https://japantoday.com/category/nati...-chopper-crash

Well, this is starting to sound distressingly familiar. I doubt we'll ever hear more about the accident chain in the Japanese news, but wondering if the required ground run, and hover tests were completed, with inspection before just taking off for a little spin.

http://www.asahi.com/ajw/articles/AJ201802060049.html


This video may be of interest. (It does not appear to be behind a paywall).

Very similar to the galveston bay accident, and the fort Campbell accident. Main rotor separation in cruise flight.

Yup. And without chopping the tail. So very likely not preceded by loss of individual blade. Just the Main rotor departing. Chilling and sad.

I see at least two blades come off, and that would leave two on the mast/head. More and more like maint issue from the inspection/repairs. Hard to see though, but seems like just before the ground, I can see blades still attached. Maybe...

at 0.18 I can clearly see two blades. One at 2, and one at 8 relative to the airframe. At 0.24-25 I think I see main blade rotation just before impact. I don't think the hub departed, but speculation of course.

There was a clear shot on the news of a blade lying across the bottom of a concrete water culvert some distance away.

Here: https://www.jiji.com/jc/article?k=2018020600888&g=soc


and a time-lapse shot here:
https://www.jiji.com/jc/d4?p=sag205&d=d4_ftee

Strap pack failure? Without seeing the root of the blade, it's hard to say the cause of the failure. But I think I saw 2 blades depart during the accident video. I wish Boeing would put more effort into this recurring problem.

Hmmm reminds of a Whistling Chicken Leg issue a 20 years ago.

Since it was coming out of mx, if not a failure of the strap pack, could be incorrect asm after stage check, or left loose, or something like that. A dual failure would indicate that the problem was not related to one blade asm, but covered both blades being affected. It would be possible for the first failure to lead to the second failure, but then the other two blades seemed to stay on the hub all the way down.

After one comes off for any reason, the rest can be a crap shoot.

Trying to Google it - the strap pack is that series of plates that hold the blade root to the hub... right?

'main rotor head' is what got changed.
https://www.asahi.com/articles/photo...206001939.html

Yes. The "straps" carry the centrifugal loads on the pitch housing/blade.