As Gazelle Pilot , i can say if you lose the control of the tail due to the tail wind, you keep it again after 180° turn, when the nose go to the wind...that's all , no spining ! I experiment that some times

Loss of T/R thrust for some reason...

A person was being winched at time of the spin. During the spin and descent the person was winched up into the doorway. Not sure if it was a victim or crew member.

Would a pilot have a different response in the first few seconds had their not been a person on the line?

Mickjoebill

The service letter amplifies what is already known about Fenestron stall - you need to apply maximum right pedal immediately - it also says it occurs in light winds.

That Taiwanese 365 had a major loss of TR thrust, not LTE or Fenestron Stall - it kept spinning, which doesn't happen with FS - as bobakat says.

As an ex- Gazelle pilot/instructor and a current 365 one, I can say that there is at least as twice as much TR authority in a 365 as there was in the Gazelle and a 40kt cross and downwind limit.

In a strong downwind condition - >20kts - the large tail fin does make directional control a little more twitchy but any tendency to weathercock will be negated as the aircraft comes back round into wind.

almost certainly - he did a great job getting the person on the wire safe - just unfortunate to crash afterwards.

CRAB

I would still put my money on LTE :-)

Big difference between your N3 and it's predecessors if it was an 'N' with little metal blades then it would be way different

G.

All we see in the vid is the ac moving slowly from right to left of shot, with someone on the wire.

Now then, obviously its only going to be an opinion, but were they;

a. Approaching the pup with the person being lowered down.
b. Flying away from the pup with the person being winched up.
c. Trying to maintain a downwind hover but allowing the ac to stray.
d. Slowly approaching downwind, lowering the person and about to turn left for an into wind recovery.

… just before the rotations began?


Seems strange in such a strong wind to operate downwind and with the amount of other aircraft around, there must have been a pattern in operation around the ship.

Not convinced about that :eek:

Looking closer at around the 17 second point;


http://i52.photobucket.com/albums/g1...ps21auds3x.png

zoomed in;

http://i52.photobucket.com/albums/g1...psnfuhzqxw.png

Still don't think so - anyone from Taiwan know which model of 365 it was?

Sid - I didn't check to see if the person on the winch did make it back to the cabin - maybe it wasn't so. However, in the circumstances who can blame anyone?

Crab... I'm pretty sure they are N2s.

It certainly looked as if they were doing their best to get their winchman safely back to the aircraft. He was clearly being winched in as the event unfolded.

Tragic regardless of the cause. :(

OH

CRAB - extract from the SL

In the various cases which resulted in the loss of yaw axis control, the action applied to the RH yaw pedal was not enough (amplitude/duration) to stop rotation as quickly as the Pilot wished.
As the aircraft continues its rotation, the Pilot generally suspects a (total or partial) tail rotor failure and decides either to climb to gain speed or to get closer to the ground.
In the first case, increasing the collective pitch results in increasing the main rotor torque and consequently further speeds up leftward rotation. This results in the loss of aircraft control.

Yes, they are N2's. The N3 has a different (upgraded?) fenestron with asymmetric blades but can't confirm any performance increase over the N2.

Geoffers,

The N3s were indeed fitted with an asymmetric fenestron although some of the earlier models were initially fitted with the same one as the N2. It made a noticeable difference in performance as well as being quieter. I seem to remember that the N3s NHV got originally had the N2 fenestron. A number of N2s were retrospectively fitted with the asymmetric fenestron. If you remember the ex-Maersk N2s Schreiner got and which I gave you your differences course on, they were later fitted with the upgraded fenestron before being moved from Nigeria to Sudan. The big performance difference in the N3s however, came from the engine upgrade. It did give us a lot of starting problems in Cameroun so we always carried a portable GPU and had little battery powered fans and additional ventilation in the baggage compartment when we shut down on the pipeline.

With the wind from the wrong direction incipient LTE could be a problem with any of the 365 models.

Well, I've watched the video, and I'm not entirely sure what caused this, because I don't know the windspeed, the magnitude of the pedal input, the density altitude, the mass of the aircraft, the pilot's degree of caution in causing an overtorque. You know... the et ceteras. Perhaps someone looking at an image of a helicopter the size of a flying termite can draw more information from this clip than me, or perhaps they have greater skill.

But then again, my experience in Dauphins is limited to a mere 4000 hours in the 366G1, 365N, N1, N2, & N3.

Geoffers - remember it talks about light wind conditions only, because in any stronger wind the directional stability will stop the spin or slow it enough to regain control - it won't keep spinning like the one in the video.

Have any of the long-time 365 pilots here ever experienced fenestron stall/LTE that spun you round and round like that?

CRAB - consider that the fact that the aircraft in question was moving downwind at the time and losing translational effect therefore pulling more collective to maintain height.

I don't think EC would have issued an SL like this if they did not have good reason. I suspect there are a whole bunch of 'incidents' that we are unaware of. If they say don't try and fly away with this issue going on then they must have lost few to that problem.

If not LTE then what would the failure mode be? Is there a history of drive shaft failures?

Anyway, sad day for the Taiwanese CG. If there are lessons to be learned then I hope they will share them.

G.

http://www.taipeitimes.com/News/front/archives/2016/03/12/2003641375

Geoffers - I think the SL is a bit of an a*se-covering exercise as it highlights that correct pilot action (ie full right pedal) will stop the spin. This was ably demonstrated by a French TP to put to bed the myth of Fenestron stall on the Gazelle - he established a 120 deg/sec rate of yaw and stopped it dead with full right pedal (and a little bit of an overtorque, but that is better than crashing).

Note the SL refers to ALL TRs, not just the Fenestron and simply shows the thrust response from pedal position is essentially linear with a conventional TR but more S - shaped with a Fenestron.

The SL primarily concerns itself with occurences in the low hover where incorrect pilot action could easily result in trying to land with a high rate of rotation - not usually a good outcome from that - the Taiwanese 365 was in a high hover so LTE/FS is very unlikely to be the problem since it would be easy to flyaway from it.

However - Sid's link (which I can't get to) might be a possible answer - a big slug of seawater through the fenstron could easily trash the TR driveshaft due to the sudden drag.

Concur with your analysis although I have my doubts that lessons learned on the Gazelle can be applied to the N2. The blades on the later models were notoriously fragile so a slug of seawater could well have set the whole thing off.

There but for grace of god etc etc.

G.

Hi Geoffers,

Yes there have been at least an history of a drive shaft failure on a 365N.

A close friend of mine experienced a failure of the output flector (# Thomas Coupling ) at the main gear box output level. The design is the same on the N3.

It happened on a rig take-off .... first heavy vibrations with a loud banging jerking noise, than the armed floats deployed uncommanded (due to combined vibrations and the shocks of the ofset turning shaft still attached to the flector banging against the "mechanical Floor" that triggered the floats relay located just above on the "mechanical floor" )

The pilot, on the very early stage of the take-off managed to turn back to the deck, where he slammed the helicopter down as the flector completely broke.

It is interresting to note that the inflated forward floats almost completely impaired his downward vision to aim at the center of this small helideck.

I can add, that after many thousands hours(#8000) on different versions of 365 and also Gazelle flying not only offshore but also aerial work (long line,sling, movie shooting, picture taking, survey, military etc....) I've never experienced, nor never heard one of my colleagues talk of a so called tail rotor stall or fully developed LTE on these types.
Could it be pure luck after all ?

Cpt,
I would imagine the floats inflated due to the vibration in the Immersion probe (shorting it out) manifested by the airframe vibration rather than the flector banging against the 'mechanical floor' triggering the relay.

The older Immersion probes were known at times to be the reason for setting off the floats uncommanded due to either sand build up or even water shorting in flight (rain) as well as internal vibration within the probe.

Link is still good.

Taipei Times

Perhaps the ship was acting as a 'breakwater' and the wave came off the far side.
Anyway, plenty of ship movement going on; maybe the 90 degree difference of ship heading during the operation could be a factor?!

http://i4.mirror.co.uk/incoming/arti...ter-rescue.jpg

http://img1.cna.com.tw/Eng/WebEngPho...10016t0001.jpg