Helicopter crash New York City

[jellycopter]

Originally Posted by paco

"What is puzzling is that it looks like the rotors take only the top part of the MRGB with them when they separate rather than ripping the whole gearbox out."

I agree - Which leads me to wonder why it was weakened - previous overtorquing? I know it's one of the places I look at when I'm preflighting. It would have to be one hell of a pull, though.

It’s my understanding that the planetary reduction gear is located towards the top of the 206 main rotor gearbox. A sudden stoppage of this planetary gear assembly ( as in the Super Puma a few years back ) might potentially bust out of the gearbox casing and split it in two.

[FH1100 Pilot]

Originally Posted by [email protected]

If the MRGB is allowed to move (as a result of one of the nodal beams or other fixings giving way), it would twist the TR drive out put which could, feasibly, create enough imbalance and drag along the TRD shaft to overstress the boom and cause it to fail.

What is puzzling is that it looks like the rotors take only the top part of the MRGB with them when they separate rather than ripping the whole gearbox out.

Whatever the initial trigger, it rapidly becomes a catastrophic in flight breakup which even the best pilot in the world wouldn't survive.

In a 206, the transmission is not directly connected to the t/r driveshaft - it runs through the freewheeling unit and then the engine. To me, it appears that not only did the entire transmission come out, but maybe the engine as well! Look at this pic and tell me what's missing. That lump there towards the back - is that the engine or just the oil cooler?

[[email protected]]

This is interesting about the freewheel on 206's https://www.casa.gov.au/sites/defaul...separation.pdf

1. Effectivity All Bell 206 Jet Ranger and Long Ranger series helicopters. 2. Purpose Alert operators, pilots and maintainers to critical freewheel unit lubrication issues in order to reduce the possibility of torsional main rotor mast yielding and in-flight separation of the main rotor head from the mast. 3. Background Defect report investigations into continuing failures of main transmission freewheel units in Australia and a near fatal incident in Canada demonstrate that a malfunctioning freewheel causes varying degrees of main rotor mast failure, ranging from torsional yield to complete separation of the rotor head from the main rotor mast.

In a 206, the transmission is not directly connected to the t/r driveshaft - it runs through the freewheeling unit and then the engine.

So a freewheel failure/snatch could have caused the TRDshaft to distort stressing the tail boom as well as trashing the MRGB.

[wrench1]

FWIW: word is the MR, transmission, and nodal beam assembly departed together still attached to the roof/deck section.

[RAFEngO74to09]

The transmission on a Bell 206 is held in by 2 x upside down V links



These have broken before - as in this incident in Australia https://www.atsb.gov.au/media/news-i...e-requirements

[Bell_ringer]

Originally Posted by RAFEngO74to09

The transmission on a Bell 206 is held in by 2 x upside down V links
These have broken before - as in this incident in Australia

This has been referenced previously. In this case the bearings had worn which accelerated fatigue, there had been inadequate inspections.

[Sam W]

The two V links are on the non-nodal beam equipped 206B. The 206L has four independent links between the transmission and the two nodal beam flexures.

[albatross]

Originally Posted by Torquetalk

Doing that kind of work, from that FATO, a Longranger would spend a lot of time at the top end of its performance on multiple cycles day-in, day-out. Using transient take-off power would be routine. Misjudgments about fuel load and pax weight with a very high turnover would also be easy to make. Without HUMS, there is no certainty that the aircraft had not been previously over-torqued, either occasionally, or routinely.

Sea level , 6 lightly dressed pax, no baggage, probably max 400 lbs of fuel if planning 4 tours between fuelling.
I doubt you would be anywhere near 100% torque on departure much less pulling any transients.
Certainly not cruising around at max continuous Q.

[Dick Smith]

We have decided to ground our Longranger pending further information coming from the NTSB ,FAA ,CASA and Bell

Worth being conservative in this case I reckon!

I do not believe it will be a very long time before the relevant information is available that will allow safe flight

[Weheka]

Originally Posted by Squawk7700

This talk of the fuel call being a disguised mayday is fanciful at best. He called for fuel as he no doubt needed fuel, probably like he would do 10 times or more per day! Presumably to get the fuel guy/gal out at the pad ready to hot-fuel, saving time and money.

Exactly right, completely normal call for those types of ops.

[BigMike]

Photo from the NTSB showing rear of the aircraft, and separation of the tail-boom aft of the attachment points.

[Bell_ringer]

That also looks like what is left of the hot section and exhaust of the engine.

[BigMike]

Further Photos (NTSB):

[helispotter]

Originally Posted by BigMike

Photo from the NTSB showing rear of the aircraft, and separation of the tail-boom aft of the attachment points.

In other words, not a case of the four boom attachment bolts having been the cause of the accident.

[Bell_ringer]

Zooming in, what appears to be the remains of the engine and aux gearbox.

[BigMike]

Originally Posted by helispotter

In other words, not a case of the four boom attachment bolts having been the cause of the accident.

Well clearly if they are still attached, no.

[FlexibleResponse]

1. Vertical with tail-rotor(?)
2. Tail boom
3. Main rotor
4. Cabin


https://abcnews.go.com/US/tourist-he...y?id=120755978

Watch ABC News video at 1:18 and note that main rotor separation occurs a lot later than tail boom and tail rotor.
That would seem to indicate that the tail boom failed first after extreme and rapid yaw.

[Kulwin Park]

You can see the T/R Driveshaft section is broken about halfway, ENGINE to OIL COOLER FAN section, just above the white Starter Generator in the above picture.

[Bell_ringer]

Originally Posted by FlexibleResponse

Watch ABC News video at 1:18 and note that main rotor separation occurs a lot later than tail boom and tail rotor.
That would seem to indicate that the tail boom failed first after extreme and rapid yaw.

That has been stated previously in this topic.
What is impossible to tell from the few pixels contained in these videos and related images, are what caused the extreme yaw.
Was it something in the tail rotor drive system that went, or, was it something in the main gearbox, transmission or mountings that let go first.
That is nothing the currently available videos can answer, beyond confirming a sequence of visible events.

[FlexibleResponse]

What @Bell_ringer said. I agree.