Air Vanuatu Twin Otter elevator cable snap
 

From the Vanuatu media: An Air Vanuatu (NF) Twin Otter on a domestic flight made a safe landing with 19 pax or pob when the elevator cable snapped just moments before landing at an outer island airstrip (Walaha, Ambae). The cable had been fitted new just 6 months ago. If the aircraft had been at higher altitude and not so close to touchdown the result could have been catastrophic, and in a similar incident in Tahiti several years ago.
NZ aviation accident people are part of the investigation.

If the TwOtter has a conventional trim that is controlled by its own cables, it might be possible to fly it down to a safe landing using the trim only.

Indeed.
Non event - just fly it with the trim wheel.

Hardly a non-event.:=

Hah! Very good! ;)

RE Tahiti incident: Air Moorea Flight 1121 was a De Havilland Canada DHC-6 Twin Otter which crashed shortly after takeoff from Moorea Airport on Moorea Island in French Polynesia on 9 August 2007, killing all 20 people on board.

It was bound for Tahiti's Faa'a International Airport on a regular 7-minute service, one of the shortest on earth, scheduled 40 to 50 times a day. Frequent takeoff and landing is believed to have been a major factor in the crash, because of wear and tear on the elevator cables, inspected only at fixed time-intervals, regardless of usage.

In 2003 a Dornier 228 suffered a lightning strike which melted, or probably vaporised, the elevator control rod.

The crew flew the aircraft using electric trim, including a go around, the subsequent landing was not the best resulting in the aircraft being written off and some substantial injuries to the occupants.

ASN Aircraft accident Dornier 228-202 LN-HTA Bodø Airport (BOO)

I was reminded of this accident when an FO tried to convince me it would be OK to fly a DO228 through a storm, I politely declined and we went around the weather.

In the case of the Air Moorea DHC6, I seem to recall how it was typically parked on the ramp possibly contributing to cable wear as well. Apparently jet blast from taxiing large aircraft would regularly strike the elevator from behind, causing it to move violently. Additionally, the salty tropical environment is not kind to the steel cables. Closer/more frequent inspection and corrosion protection treatments are more than just a good idea in such an operating environment.

An elevator cable break may be more recoverable in some circumstances and airplane types than others. Though I've demonstrated a trim only (elevator free) landing in a C-172 with good results, I'd be less sure about doing this in a larger airplane with higher control force required and/or slower trim. Particularly if it was unplanned and had not been previously practiced under controlled conditions at a safe altitude.

If near the ground and out of trim, things could easily go south before the effect of cranking the trim wheel affected the pitch attitude. Given the typical delay in trim effect while flying stick/elevator free, PIO may result in some airplane types and loading conditions. Anyone thinking that just because it's relatively easy to control one aircraft in one set of conditions would do well to consider that it might not be so easy in other conditions. It pays to know ahead of time!

Indeed. First off, Fa'a'ā International Airport is relatively small. Unsecured elevator movements while parked in a high hydro-carbon contamination area, (jet blast), may, over time contribute to several problems, one of which is premature control strand failure.

Why the DHC-6 aircrew may or may not have routinely installed a control lock is undetermined. The direction the DHC-6 aircraft were routinely parked on the apron is also subject to investigation.

Most pilots I've flown with, (and taught), know enough to park upwind and install a control lock.

As an aside, in the late 1970's and early 1980's, the BN-2A Islanders were marshalled well away from the big jets at Pape'ete's Faa airport.

Did these DHC6 fly above VNE...:mad: as I often watched with planes used to drop jumpers!!! Enough to destroy cables .

Not sure if the same aircraft as the 2007 crash, but a plane I flew years ago crashed in the Pacific somewhere:
I flew this plane on floats in saltwater 1984/85.
All the salt going in the tail section without being rinsed out daily and flap brackets that correoded away to half thickness after a year in the salt made me nervous and I quit the job.
Years later I tracked the tail number and found it on wheels in the Pacific, just after it crashed and killed everybody.
Tail number when I flew it was N-784DL.
DL for Don Lewis, owner of the company.

Edit:
Found it, same airplane that I flew on floats/
https://en.m.wikipedia.org/wiki/Air_Moorea_Flight_1121

This site really does bring out some knobs!!! :mad:

If you cant fly it with a trim wheel, get the attitude you desire by having the pax move up and down the cabin.

If the aircraft nose is too high, fill the front seats/ aisle, laps. If the nose is too low get every one in the rear... FO too if it helps!

I remember reading a report of a crash where a similar sized plane crashed due to an alligator(or crocodile) getting loose and every one running to one end of the aircraft to get away from it. Don't know if its true but very believable.

The OP posted:

That is a very different situation from a landing planned with time to allow for an alternate method of pitch control.

This would be a really poor idea, re configuring an aircraft in a uncontrolled manner, with undisciplined occupants, who would now no longer be secured in the aircraft is asking for trouble! Too many people move too far, and you're out of C of G limits, out of control, and not going to regain control - and you asked them to move! Not when I'm flying!

If you're having to consider flying with the trim wheel, for loss of other control, it's an event! The trim wheel, with practice and time to perfect technique, can be used to set up a landing, but certainly not at the last moments on the approach. The Twin Otter is a more pitch sensitive than some other types. Changes in flap position, or power, can affect pitch of a Twin Otter more dramatically and suddenly than other types, flying by pitch trim alone is not a last minute alternative.


The design requirement associated with this characteristic:

Nothing there says "suddenly" or "at the last moment". It also must be practiced.

There are shorter scheduled flights:

Nur zwei Minuten in der Luft: Das sind die kürzesten Linienflüge Europas - FOCUS Online

Now defunct (I believe) South Pacific Island Airways lost a Twin Otter from the Pago Pago base on the island of Ta'u in about 1984 due to the same problem on short final. The guys got it down, just, but it slid off the dirt strip into the bush and caught fire. Can't recall if there were pax casualties, but I know the American captain survived and returned to flying not too long afterwards.
I seem to recall (but open to correction) that the corrosion of the elevator cable was attributed to the local pax habit of travelling with badly sealed buckets of fish in saline water which were carried in the aft hold and tended to leak.

Short scheduled flights - Loganair Westray to Papa Westray took less than a minute.

...made me curious so did a little light reading...

http://www.dtic.mil/dtic/tr/fulltext/u2/a800185.pdf


...report is a few pages in...past all the chaff...

One gets the impression from reading this that this problem essentially only affects Twin Otters? Why? Surely other types, such as Islanders, PC-6 and Caravans, also operate in such harsh environments, and seem to get away with it?