Firefighting Chinook Crash

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It has been suggested the rate of rotation could have caused disorientation....which certainly could be a factor in what happened.

that was a major factor in the Wessex crash in 1993 in Snowdonia. I talked to the pilot, who was a colleague, afterwards and he said the rate of rotation made it very difficult to judge height causing him to pull collective just too early to cushion the touchdown in the water the way he intended.

[gipsymagpie]

Bears remarkable similarities to a crash of a Chinook doing logging 25 years ago. I believe a failure of an electric component let to an instantaneous command for full yaw deflection which the SAS actuator did but this then caused the hydraulic actuator to fail (by bursting). I only have limited Chinook experience but it seems to fit.

https://aviation-safety.net/wikibase/23446

[fdr]

The rear rotor TPP really looks like it is giving left yaw, the fwd rotor may have some left yaw input too, the machine is not translating sideways greatly, so the fwd TPP is not countering the yaw much if at all. Yaw servo jam?

[60FltMech]

CH-47D flight controls

Hello everyone,
Before I became a crew member on UH-60s I worked quite a bit on the CH-47D, I’ve done a bucket load of flight controls rigging on them and as SASless pointed out, the flight control system is not exactly simple.

Having said that, it’s not pure magic either. From memory it goes roughly like this: (anyone with more recent experience please correct me) the controls move through linkages horizontally from the cockpit to the companionway/flight control closet where th e pallets someone mentioned already are located.

The pallets have the force trim actuators(mag brakes) and position transducers etc. on them. Then the controls rods go vertical to the ILCAS(SAS Actuators) the on top of those the controls go horizontally to the first stage mixing assembly bell cranks, which transfers the control motion to the to the second stage mixing assembly where it goes horizontally across the top of the aircraft, then vertically to the swiveling and pivoting actuator pilot valve.

And here is where I suspect the failure may have happened. The previous incident involving the barrel roll of a CH-47D was attributed to a jammed pilot valve in a fwd pylon actuator, can’t remember which one, maybe swiveling, causing it to EXTEND fully. Anyway, This incident trigged a period of time where special recurring inspections were performed on the actuators where you ensured certain hardware was properly installed by pulling an inspection plate on the pilot valve. So, possible pilot valve jam? Or here’s another scenario.

While rigging flight controls we very often disconnected the input rod to the pilot valves to make adjustments, once you push/pull on the valve that actuator takes off. If the control rod anywhere in the system got severed/disconnected, the actuator would simply drive whatever direction had LEAST force applied to the pilot valve. In this case, If I remember right if you disconnect the control rod from the valve the actuator would RETRACT fully. There are a bunch of places where this disconnect could have occurred in such a complex system, I feel like it could have been anywhere after the second stage mixer, again just speculating. I lean towards the aft controls because of the tilt of the rotor system, also remember the lions share of the lift is on the aft system due to the amount of the weight contained in that section of the aircraft.

Anyway, no matter what the cause, such a sad situation. Prayers for the families/friends of all involved.


60Mech

[ORAC]

https://twitter.com/djsnm/status/167...HhlFHGKbTPQr_A

Electronic flight bags are great.... until you drop them and they jam controls. I'm sure this kind of thing had happened long before the digital era, with other more low tech flight documents

https://data.ntsb.gov/Docket?ProjectID=105544






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[MechEngr]

A New York tour helicopter went down because a front passenger's bag strap caught a critical control on the cockpit floor.

Here it is: https://www.usatoday.com/story/news/...ash/415706002/

There's no good excuse - there are many suppliers of iPad mounts to attach them to pretty much anything in a reasonably solid manner. It's horrifying to suspect the guy who dropped the iPad knew dropping it was the cause of the control problem and be unable to reach it. A good day doing a good job and suddenly this? It's like those Final Destination movies.

[60FltMech]

Tragic. Seems the crew were just like all the rest of us, just doing the job and got caught by something they probably never thought about.

I feel like I do a good job securing the cabin before flight, can’t stand it when something is just left loose on the floor, but I think I’ll reassess my routine and start putting an eyeball on the pilots gear as well….

FltMech

[212man]

Originally Posted by MechEngr

A New York tour helicopter went down because a front passenger's bag strap caught a critical control on the cockpit floor.

Here it is: https://www.usatoday.com/story/news/...ash/415706002/

There's no good excuse - there are many suppliers of iPad mounts to attach them to pretty much anything in a reasonably solid manner. It's horrifying to suspect the guy who dropped the iPad knew dropping it was the cause of the control problem and be unable to reach it. A good day doing a good job and suddenly this? It's like those Final Destination movies.

pretty sure it was the passenger’s tether that snagged it - although this news article is a quote in the immediate aftermath.

[SASless]

212man is correct.

One of the passenger's tether moved the Fuel Shutoff Valve causing the engine to stop.

30 seconds of searching on the internet found numerous news articles quoting the Pilot and NTSB published information confirming that.

The chilling part of the results are accounts of the Go Pro video of the cabin as it sinks into the river with the passengers struggling to remove or cut the harness and tethers.

[212man]

Originally Posted by SASless

212man is correct.

One of the passenger's tether moved the Fuel Shutoff Valve causing the engine to stop.

30 seconds of searching on the internet found numerous news articles quoting the Pilot and NTSB published information confirming that.

The chilling part of the results are accounts of the Go Pro video of the cabin as it sinks into the river with the passengers struggling to remove or cut the harness and tethers.

Indeed - the NTSB report is quite frank about those final seconds and it’s clear those who had to
listen/watch the recordings would have found them pretty traumatic I think. Especially probably having to repeat the process for evidence clarification.

[MechEngr]

I preferred not to again get details of the event where the passengers were drowned like rats because the helicopter company failed to provide proper flotation for operating over water and just assumed the inflation system would work. Not even 30 seconds of searching.

[ApolloHeli]

Originally Posted by MechEngr

I preferred not to again get details of the event where the passengers were drowned like rats because the helicopter company failed to provide proper flotation for operating over water and just assumed the inflation system would work. Not even 30 seconds of searching.

The floats were not the issue. Yes, one inflated more slowly than the other so the helicopter rolled inverted as a result, but this is quite common for a power-off ditching (helicopters rolling inverted) - there is a reason HUET required escaping an inverted helicopter. The fundamental issue was the policy of tethering passengers with anchor points behind their backs, without providing the training or the means to quickly release the tether and evacuate the aircraft in an emergency.

[FH1100 Pilot]

Okay, so we know what caused the jammed pedals. What caused the thing to fall out of the sky?

[SandBlaster214]

You Tube

[Nubian]

Originally Posted by ApolloHeli

The floats were not the issue. Yes, one inflated more slowly than the other so the helicopter rolled inverted as a result, but this is quite common for a power-off ditching (helicopters rolling inverted) - there is a reason HUET required escaping an inverted helicopter. The fundamental issue was the policy of tethering passengers with anchor points behind their backs, without providing the training or the means to quickly release the tether and evacuate the aircraft in an emergency.

Not quite. The floats were an issue as they only partially inflated, as the second bottle was not activated, not completely filling the bags and caused it to roll. So quite a large factor. I question the statement for rolling over as a norm. This was dead calm waters, not the open ocean where there is significant waves.

However the root cause of that accident can be traced back to the managements decition to offer these rides in the manner they did and for not putting enough barriers in place. Alcohol was an issue, not secured Fuel Shut Off lever/choice of helicopter, choice of harness, etc..
A HUET-course wouldn’t have saved those.

[212man]

Originally Posted by FH1100 Pilot

Okay, so we know what caused the jammed pedals. What caused the thing to fall out of the sky?

I think that's a question many of us have

[helispotter]

Originally Posted by FH1100 Pilot

Okay, so we know what caused the jammed pedals. What caused the thing to fall out of the sky?

Worth looking at footage linked in #8 again. Not really falling, rather increasing rate of decent. With the yaw rate building up, must have become more difficult to control in general and keep orientation. Aerodynamics of rotors would start becoming complicated due to the yaw rate as well?

[SLFMS]

I can’t help but wonder if they had put full boot in if the iPad would have broken or bent enough to give better control
That is of course assuming they didn’t. It’s certainly not to critique I’d say there was a good chance if the flying pilot was LH he did not know the reason for the jammed control.

We are normally taught not to force a jammed control too hard. Perhaps I’m under estimating the force required but Monday morning Quarterbacking has me wondering if maximum power of the leg would have bent or snapped the ipad enough to regain control. iPads are not that tough after all.

Perhaps the marks show they did try so to be clear it’s not a comment on the crew rather a what if. It seems strange to yaw so much while established at the time of the jam so another possibility is they were trying to release the ipad with a wiggle but it made it worse.

Sad outcome and something I’m sure have many Pilots thinking about their cockpit security

[jimmymc]

Does anyone know how the iPad was mounted in the aircraft before it dropped into the footwell?

[megan]

Okay, so we know what caused the jammed pedals. What caused the thing to fall out of the sky

Pilot sitting X feet in front of the axis of rotation yawing at 148° per second shoulder harness unlocked, perhaps the 'g' forces are such that he is doubled over. My back of the envelope calculation comes up with a little over four 'g' assuming the point of rotation is half way between the two rotors. Front rotor is at station 93, rear 560. Issue mentioned by F-14 crew if the aircraft is in a flat spin (which is irrecoverable in the aircraft), not a posture you want for the recovery which is via ejection.

Lesson might be, fly with a locked harness, some carrier pilots can tell stories about face planting the instrument panel on an arrested landing..