PPRuNe Forums - Bristow S92 down west of Bergen Norway

PPRuNe Forums (https://www.pprune.org/)

- Rotorheads (https://www.pprune.org/rotorheads-23/)

- - Bristow S92 down west of Bergen Norway (https://www.pprune.org/rotorheads/657874-bristow-s92-down-west-bergen-norway.html)

Quote:

Originally Posted by albatross (Post 11610291)

A very experienced pilot friend and a very smart guy (don’t tell him I said that!) looked at these posts and said “Humm aren’t you folks getting focused on the seaworthiness of the lifeboats on the Titanic and kind of ignoring the cause of the ship hitting the iceberg?” He has a way of saying things like that. He will not post on aviation sites and seldom, if ever, even looks at them, except when I occasionally drag him, kicking and screaming, over to my computer screen. He has a point.

I think what you’re seeing is not a lack of interest from aviators as to why it occurred, but (somewhat surprisingly for prune) a restraint in pointless guesswork as to the cause. I’d like to think in respect to the deceased and crew who are going through a very difficult time, but also because there’s insufficient information to make any assumptions and we will know soon anyway due to there being survivors.

There is however, a significant amount of information that can be discussed about the post accident events gleaned from open source information.

Of course there is the absence of witness accounts, no video of the accident as it occurred, and other differences from other similar events.....such as the in the other accident a few days before this one.

Witness accounts always engender discussion as they can vary greatly and of course watching a video of something happening presents a great many opportunities for discussion.

The float discussion was just one topic that is of course relevant and as we have seen leads off in several directions as it should.

In time there will be yet more such issues that shall be ripe fruit for examination.....including what caused the aircraft to wind up in the water.

What lessons are learned if there is no discussion amongst professionals of the factors surrounding a crash?

https://cimg1.ibsrv.net/gimg/pprune....cd03c77857.jpg
Looks like cable hanging below the tail boom. That doesn't look like water impact damage there either.

Black striations on tail rotor paddles? Wire from the hoist?

Quote:

Originally Posted by megan (Post 11611877)

Black striations on tail rotor paddles? Wire from the hoist?

The cabin door was closed, so seem unlikely to be hoist cable - more like TR control cables?

If you watch the video of the recovery you’ll understand why the tail has that damage.

LZ

Quote:

Originally Posted by Hot_LZ (Post 11611978)

If you watch the video of the recovery you’ll understand why the tail has that damage.

LZ

Yes - it gets a good smashing twice!

An update from NSIA (only in Norwegian so far) states that the floats were armed, but (obviously) did not inflate.
They speculate that it could be because the sequence of events managed to outsmart the design criteria.

Quote:

The cabin door was closed, so seem unlikely to be hoist cable - more like TR control cables?

Just wondering 212, given one of the hoist hooks was missing, wonder too if that white streak (abrasion mark?) below where the hook should be is indicative of anything. Will come out in the wash.

https://cimg4.ibsrv.net/gimg/pprune....d0d8579af1.jpg

Quote:

Originally Posted by GenuineHoverBug (Post 11612061)

Quote:

Update March 8, 2024

The investigation is still in an early phase. The Accident Investigation Board has interviewed the five who survived the accident. Together with analysis of data from the tachograph, this is important information to be able to understand why the accident could have happened. There is good dialogue with the parties involved. All findings that are significant for flight safety will be immediately given to the Norwegian Civil Aviation Authority and to the European Aviation Authority, EASA. The American Accident Investigation Board, NTSB, is associated with the investigation with an accredited representative.

So far, no significant discoveries have been made that affect the immediate flight safety.

The survey will also include survival possibilities. This includes both the helicopter's and crew's equipment, the possibility of evacuation and the rescue operation itself.

The helicopter was equipped with floats. These were armed, but were not automatically triggered in the event of a collision with the sea. The flotation elements for the helicopter type are designed for a controlled emergency landing on water. Although the accident appears to have had limited energy when it collided with the sea, it cannot be described as a controlled emergency landing. The fact that floats were not resolved may be because the situation that arose was outside the system's limitations. The Accident Investigation Board cannot thus far say that there is a technical fault with the floats.

.....

Quote:

Originally Posted by HeliComparator (Post 11606321)

Someone dies, this creates an opportunity for some childish bickering and point scoring. Rather sad.

I miss the childish bickering HC, RH gets boring when we all play nicely!

Is there any indication of when the Norwegians might release more information regarding this unfortunate accident? They stated on the 11th March that it was not a controlled ditching and there has been no comment since.

https://www.nsia.no/Aviation/Investigations/24-203

New info today. Aircraft ended up 30 degrees nose up before impact. It mentions they were doing a “mark on top” auto letdown but doesn’t say whether or not they were coupled at the time of the upset.

Quote:

Originally Posted by FC80 (Post 11654473)

More questions arise, like is it not SOP to use the APU in these evolutions? That would have mitigated the power loss from the blade impact, and kept AFDS functional.

Even so, the AFDS is a last resort system and should be one of the last things to stop working, especially as it uses virtually no power.
If the systems are properly designed.

Quote:

Originally Posted by HeliComparator (Post 11654584)

Even so, the AFDS is a last resort system and should be one of the last things to stop working, especially as it uses virtually no power.
If the systems are properly designed.

I’m not going to be an apologist for the design, but I do think it’s understandable. As I alluded to earlier, the battery’s sole function is to start the APU. It doesn’t even need to drive a motor to do so, as the APU has a hydraulic starter using a hydraulic accumulator - so the battery just opens the solenoid and makes a few sparks. So, from a failure mode scenarios perspective, I can see why ditching with battery power only might be discounted. I guess the omission comes with looking at mechanical failures only, and not crew related.

Not entirely familiar with S-92 battery system, though I have to imagine it’s similar to H-60M:
https://cimg5.ibsrv.net/gimg/pprune....8bed29955.jpeg
FltMech

I think the reference to new rules around flotation equipment is curious, and I wonder if this statement is accurate

Quote:

New international regulations which, among other things, include emergency flotation elements for helicopters have been published.

Are there really new rules coming out of this investigation, or do they mean changes coming from EASA NPA 2020-16? Or CS-26/Part-26

Correct 212, this is part of the new CS26 Iss 4, specifically CS 26.435:

CS 26.435 Automatic deployment of an emergency flotation system
(a) Compliance with point 26.435(a) of Part-26 is demonstrated by complying with CS 27.801(c)(2) of CS-27 at Amendment 5 or later, or the equivalent, or with the following:
(1) An emergency flotation system that is stowed in a deflated condition during normal flight must have a means of automatic deployment following water entry. The means to automatically deploy the emergency flotation system must operate irrespective of whether or not inflation prior to water entry is the intended operation mode. If a manual means of inflation is provided, the emergency flotation system activation switch must be located on one of the primary flight controls and must be safeguarded against inadvertent actuation.
(2) Activation of the emergency flotation system upon water entry (irrespective of whether or not inflation prior to water entry is the intended operation mode) must result in an inflation time short enough to prevent the rotorcraft from becoming excessively submerged.

(b) Compliance with point 26.435(b) of Part-26 is demonstrated by complying with CS 29.801(c)(2) of CS-29 at Amendment 5 or later, or the equivalent, or with the following:
An emergency flotation system that is stowed in a deflated condition during normal flight must have a means of automatic deployment following water entry that does not rely on any pilot action during flight. The inflation system of the emergency flotation system must have an appropriately low probability of spontaneous or inadvertent actuation in flight conditions for which float deployment has not been demonstrated to be safe. If this is achieved by disarming the inflation system, this must be achieved by the use of an automatic system employing appropriate input parameters. The choice of input parameters, and the architecture of the system, must be such that rearming of the system occurs automatically in a manner that will assure the inflation system functions as intended in the event of a water impact. It is not acceptable to specify any pilot action during flight.

In the S-92 (along with most other types) the floats activate via water switches, but the system needs to be manually armed by the pilot. According to CS26.435 this is no longer acceptable.

I guess the sensible option is an airspeed switch to prevent inadvertant operation when you are cracking along at 140Kts - getting it to rearm below 70-80 kts would seem appropriate.

Hitting the sea any faster than that in an uncontrolled ditching is likely to be catastrophic anyway so the floats won't do you much good, even if they did deploy and weren't ripped off in the impact.