Helicopter crash Hudson River 2

[LittleInch]

Helicopter sight seeing inner York crashed with all dead.

This video looks like it was flying at some speed, then something happens, it seems to change orientation very rapidly which causes the whole tail structure to detach, followed shortly by the main rotor blade and part of the gearbox. Horrible way to go.

https://www.reddit.com/r/CatastrophicFailure/comments/1jwfxh9/full_video_of_the_helicopter_crash_in_hudson

Six people killed after helicopter crashes into Hudson River in New York

Pilot and a family with three children who are believed to have been Spanish tourists were killed onboard aircraft

www.theguardian.com

 

[mfgenggear]

well there several modes of failure.
it is possible for boon strike , yes
was the structural integrity of the boon structure possible yes
was there possible kinetic force from the gear train and drive shafts yes

the relevance of the first video some of the rivets were tore out , and there was considerable buckling in certain areas
the second video was a review of a typical helicopter gear boxes and drive shafts, important to note some type of clutch
to disengage the engine from the gear box. I am further researching this a little more, and allow auto rotation.
I was trying find actual gear teeth attributes , such as number of gear teeth , diametral pitch, pressure angle so i could run the numbers with my
Fairfield gear analysis. so what I found and have not vetted, the rolls royce engine produces 10K rpm, 472 Hp, I calculated 247.9 ft/lbs of torque
a simple example of gear reduction of 245/45 out put is 1836,7 RPM output torque of 1344.8 torque .
attached is white paper when a clutch failed causing moment on the mass components.

 

[TugboatEng]

I have an issue with that report on the freewheel gear. They found corrosion products in the freewheel mechanism and assumed it was due to water intrusion despite no actual water being present and no sources of ingress found. Did the investigators not know of fretting corrosion? That will occur with lack of lubrication.

 

[mfgenggear]

I have an issue with that report on the freewheel gear. They found corrosion products in the freewheel mechanism and assumed it was due to water intrusion despite no actual water being present and no sources of ingress found. Did the investigators not know of fretting corrosion? That will occur with lack of lubrication.

well it may have contributed to the failure , but it is plain the evidence the clutch failed, cant get any clear then that.
I find your reluctance to look at the imperial evidence. this may not be the cause of this incident and a deep drill to audit of all components.
if there a clear evidence of not following specifications and procedure. the only wet towel, is jumping to conclusions and not following failure analysis procedures. guessing is not function of sound engineering. on the other I am not saying your wrong. but not conclusive.

 

[TugboatEng]

If there was corrosion due to water I would expect pitting on surfaces. The report makes no mention of that and oddly ommitted all images of the parts that actually failed.

 

[XR250]

What a tragic and unnecessary loss of life.

When this type catastrophic failure occurs is because gear box failed. And seized which causes broken gears. Seen the results of that.
Hope the NTSB drills down to the root cause.
Again may they RIP.

Are you a gearbox guy? (i assumed that from your handle). Seems like the gearboxes in helicopters, V22 Ospreys and wind turbines have a relatively high rate of failure.
Is this due to lack of maintenance, or designs that prioritize cost and/or low weight?

 

[SWComposites]

Those gearboxes have very high fatigue loadings, for a large number of cycles. Fatigue can be hard to predict. and as a result they require lots of maintenance, which can be expensive. Everything on an aircraft, and even more so on a helicopter/VTOL vehicle, is very weight critical. (wind turbines probably not). And gearboxes are heavy, so they tend to get very "optimized", leading to very tight fatigue margins.
Then people/companies try to cut corners (costs) on maintenance and inspections, leading to unplanned failures.

 

[mfgenggear]

Are you a gearbox guy? (i assumed that from your handle). Seems like the gearboxes in helicopters, V22 Ospreys and wind turbines have a relatively high rate of failure.
Is this due to lack or maintenance, or designs that prioritize cost and/or low weight?

Swcomposite well explained

Xr250
Winged aircraft and rotory are very weight constraints. Depending on the application aerospace steels are at the limits of tensile and contact stress. Contract requirements dictate the amount of cycles and or hours.
Safety margins are low.
Machining tolerance are very tight. And components tolerance are very tight.
Heat treats can be complex with strict case depths. Yes I am a retired gear guy.
Designs are or can be complex.
High Quality standards and procedures are strict.
However there has been outsourcing to foreign country's. Thete where there has been issues.
Maintenance I never was involved.

 

[XR250]

Looks like they are looking at vibration caused by aftermarket rotor blades...

 

[XR250]

Also this...

Van Horn blades - PPRuNe Forums

Rotorheads - Van Horn blades - Read a TSB report that took issue with Van Horn blades (said they failed during an autorotation). I've flown them, they feel a little different than original Bell blades, but otherwise seemed good. Anybody know more? TSB REPORT 2019 206 crash

www.pprune.org

 

[waross]

I hate to be kicking a dead horse, but I would like to see boom strike definitively ruled out.
Juan Brown states that the boom broke at a row of rivets.
Fair enough.
But a strike behind the row of rivets may have caused the boom to break at a weak spot, that is at the row of rivets.
Juan Brown states that the first failure was the loss of the tail boom.
What I am wondering:
WE see pictures of the back of the cabin where the boom detached.
An impact or damage further back on the boom may have caused the boom to fail at the rivets.
Are there any pictures of the damage to the boom itself?
Damage to the rotor blades:
The rotor blades appear to be broken at mid span.
A comment on the radius to the blade damage compared to the the radius to the tail boom damage may easily rule out a boom strike.
Has this been addressed and I missed it?

 

[TugboatEng]

We know that the top deck attachment to the airframe of the helicopter failed. If the fasteners at the front failed first this would cause the airframe to rotate down by the nose relative to the rotor, putting the tail boom in the path of the rotor. In this case a boom strike may have occurred but would not have been a causal factor in the crash.

 

[waross]

The sequence given By Juan Brown, supported by photos;
1: Abrupt increase in altitude.
2: Loss of tail Boom
3: Loss of rotors, roof and transmission.
If the jump in altitude was overcompensated for with less collective this could have triggered a boom strike.
The boom failed at the rivets;
Well if I wanted to break apart a riveted joint in a galvanized pipe by beating on it I may have better results hitting the pipe a distance away from the actual joint to get some mechanical advantage on the rivets.
Still waiting for confirmation of damage to the lost section of tail boom and measurements of rotor damage.
I am not saying so much that it was a tail strike as I am wanting a tail strike to be definitely ruled out.

 

[TugboatEng]

If the forward attachment of the top deck were to fail first, the rotor assembly would hinge on the aft fasteners with a similar effect of pulling back on the ciclic. This could cause the rapid increase in altitude and then a boom strike due to abnormal rotor pitch. Full separation of the top deck followed the boom strike.

 

[XR250]

Interesting Reddit Thread...

https://www.reddit.com/r/aviationmaintenance/comments/1jwbv68/any_bell_206_wrenches_know_how_a_main_gearbox