S-92 Loss of control event - report

[212man]

Just seen this. Not read it yet but saw a summary elsewhere. Looks interesting! https://www.nsia.no/Aviation/Published-reports/2024-03?pid=SHT-Report-ReportFile&attach=1

[hargreaves99]

"The internal investigation team also wanted to listen to the cockpit voice recorder in order to better understand what had happened. In accordance with internal procedures, they asked for the pilots’ consent to do so. The pilots did not consent to this"

It appears a simple pre-departure brief between the crew would have avoided this whole incident, this is standard offshore procedure.

https://www.nsia.no/Aviation/Published-reports/2024-03

[Northernstar]

That pilot's refusal is typical of a culture prevalent in Norway where self belief and entitlement triumph over what is required. We hear more and more a unionised culture of doing as little as possible and scraping through proficiency checks in the simulator in Stavanger but due to union rules nothing can ever be done. A pure hierarchy based on time served. You don't have to be that capable, just get by on the day then sit back and collect the pay cheque until retirement. If only we had it that simple, now we aren't EASA so no more crossover. Just see it in passing across the median.

I wonder how much or little awareness Equinor and other oil companies have of the situation?

[212man]

I've just read it and found it be 59 pages of very little real analysis or new facts, and a lot of ambiguity and contradiction. At one point the wind is said to be 42 kts, and another it was 33 kts. At one point the aircraft accelerated to 28 kts and another it is 35 kts - neither of which tally with the wind speeds. Then we start talking about Somatogravic illusion - really? This illusion requires a significant acceleration, and was first discovered during the early jet age in the late 1940s. By definition, a helicopter taking off into a 33 kts wind and accelerating to 35 kts is not in this regime! Actually, I don't think I have ever encountered truly rapid acceleration in a helicopter with the exception being when pointing very nose down (up to 90 degrees). However, the acceleration is mainly due to gravity and so you do not encounter the 'push in the back' required for SGI (and obviously done in good visual conditions - but the physics is the same).

Cyclic force trim release function - talk about groundhog day! Are we really having to discuss how to use the FTR in 2024? Almost a minute of no intervention or assistance by the captain? I know we can all be 'armchair critics' (or Monday morning quarterbacks), but I cannot get my head around this. The captain was an ex-military instructor, although that is almost irrelevant as any captain should intervene within a few seconds of a situation like this developing.

As for 'blowback' - give me a break! At least VRS was never mentioned at any point......

The internal investigation team also wanted to listen to the cockpit voice recorder in order to better understand what had happened. In accordance with internal procedures, they asked for the pilots’ consent to do so. The pilots did not consent to this"

I find this extremely damming on many levels, and cannot fathom what kind of personal safety culture would lead to this decision. My own view would be to have as much information as possible in the report, to help prevent some other poor crew having the same - or worse! - happen to them, or even it happen again to the same crew. I know from my own experience, that the recollection of what was said and not said during an incident, are often not what the CVR reveals!

Disappointing on so many levels.

[Lonewolf_50]

As for 'blowback' - give me a break! At least VRS was never mentioned at any point. Let us be thankful for small blessings.
(Also: nice post).

[FlexibleResponse]

Somotogravic Illusions can and will occur throughout all pilots' aviation careers when flight operations include instrument flight conditions, low vis operations and/or night flying.

The basic reason for this is that the human vestibular and other balance system sensors are not naturally trained for flight accelerations (we are not birds!).

Somogravic illusions can can result from gentle (and therefore imperceptible), medium or rapid accelerations, or attitude change in any of the 3 axis.

The vestibular sense organ is UNABLE to resolve the difference between an acceleration or attitude change without the input from some other sense organ.

Slow bank angle change, for example (less than about one degree per second), cannot even be perceived the vestibular system.

I thought that this reference and associated included references was interesting:

https://skybrary.aero/helicopter-somatogravic-illusions-skyclip

And the Wiki coverage is comprehensive:
https://en.wikipedia.org/wiki/Sensory_illusions_in_aviation

[212man]

Somotogravic Illusions can and will occur throughout all pilots' aviation careers when flight operations include instrument flight conditions, low vis operations and/or night flying.

The basic reason for this is that the human vestibular and other balance system sensors are not naturally trained for flight accelerations (we are not birds!).

Somogravic illusions can can result from gentle (and therefore imperceptible), medium or rapid accelerations, or attitude change in any of the 3 axis.

The vestibular sense organ is UNABLE to resolve the difference between an acceleration or attitude change without the input from some other sense organ.

Slow bank angle change, for example (less than about one degree per second), cannot even be perceived the vestibular system.

I thought that this reference and associated included references was interesting:

https://skybrary.aero/helicopter-somatogravic-illusions-skyclip

And the Wiki coverage is comprehensive:
https://en.wikipedia.org/wiki/Sensory_illusions_in_aviation

I believe you are mixing Somatagravic with Somatogyral. They are different, and the former is caused by linear acceleration in the longitudinal axis (can also be a deceleration). I have certainly encountered the latter - typically called ‘the leans’

[FlexibleResponse]

@212man
I believe you are mixing Somatagravic with Somatogyral.

Yes, 212man you are correct. I've didn't know that the two illusions of acceleration and movement came from two different parts of the vestibular organs (the two otoliths and the semi-circular canals).

As you said, the first is described as Somatogravic and the second Somatogyral. In my years of aviation I have never discriminated between the two!

In the absence of strong visual and other sensory inputs both sensors of the vestibular organs may be involved in false orientation/spatial awareness.

[Lala Steady]

As I understand it, the somatogravic illusion ( the feeling of pitching nose up when experiencing a liner acceleration forward) was well documented by carrier pilots being steam launched and why they used to do the launch 'hands-off' to prevent them pushing nose down into the sea.

[212man]

As I understand it, the somatogravic illusion ( the feeling of pitching nose up when experiencing a liner acceleration forward) was well documented by carrier pilots being steam launched and why they used to do the launch 'hands-off' to prevent them pushing nose down into the sea.
They would certainly experience it in night or DVE conditions, not so much with a good horizon, as the visual imagery will be given precedent by the brain I think. I think the early military jets (Canberra etc) were prone to it doing missed approaches in IMC, until it was better understood, but that's from memory.

[JohnDixson]

212: showing my age….but, does the commercial pilot community teach helicopter instrument take-offs? Or for that matter, does the military?

[hargreaves99]

does the commercial pilot community teach helicopter instrument take-offs? Or for that matter, does the military?


It's not part of the UK CAA CPL or IR, but it is definitely part of any offshore line training/type rating training/LPC/OPC Sim training. This is bread and butter stuff for an offshore operation.

[[email protected]]

If the PF had ever been taught IFTOs it certainly wasn't apparent from this incident - 25 degrees nose up!!!

The transition from visual hover to instrument scan needs to be instant - ask anyone who has done night deck departures from a warship when you start around 50' or less above the water.

The PF clearly wasn't looking at the AI during the departure - select and hold an accelerative attitude, how difficult is that?

If they want to avoid this type of incident then give the crews NVG - no more flying into black holes, especially not with a 900' cloudbase and 7000m vis, they would have had a visible horizon on goggles, especially since the lights of the rig were all behind them.

I agree the sections on somatogravic illusions and blowback are just padding and wholly irrelevant to the accident. The 'pitch up' they refer to regarding blowback (flapback) happens at the onset of ETL, not at 40 kts and a gentle hover taxi forward will not feel like a pitch up either.

Neither pilot was doing their job very well that night and I am amazed they managed to avoid the water.

[hargreaves99]

we have been here before:

https://www.gov.uk/aaib-reports/aaib-investigation-to-agusta-westland-aw139-g-lbal

https://wvmetronews.com/wp-content/uploads/2021/05/NTSB-Cline-final-report.pdf

[malabo]

Why bother to install a CVR if it can only be referenced in an incident where both crew are deceased?

I was investigating a ditching incident where I suspected there was a systemic problem and so wanted to review the CVR for the crew's last 4 landings. Nope, that's not allowed.

There must have been some fantastic history of abuse in Europe for the unions to have their backs up on this.

[Turkeyslapper]

Not an offshore type so please excuse my ignorance. What’s Vmini for this type? Surely on a pitch black night rolling off the side of a deck over water it’s effectively IMC whilst below Vmini? Are AFCS functions used to mitigate such departures?

[HeliMannUK]

Minimum coupling speed for the IAS is 55knts.

​​​​​ATT (long term attitude hold) is available as the basic flight mode without trim release depressed. It is good but slow to react (like the whole machine) through the trim controls.

I've done a handful of blackhole landings and departures on decks and moving decks, not many but it's a challenge.

As the PM you need to be on top of your game.

[212man]

Not an offshore type so please excuse my ignorance. What’s Vmini for this type? Surely on a pitch black night rolling off the side of a deck over water it’s effectively IMC whilst below Vmini? Are AFCS functions used to mitigate such departures?
Vmini is 50 KIAS. Your point is valid and has been the topic of conversations before. However, bear in mind that from a certification standpoint Vmini is considered for steady state flight. During an offshore take off, using a positive accelerative attitude (we always used -10 absolute, not delta) you will reach and pass 50 kts rapidly. Even more so with 33 kts of wind!

The correct sequence should be - establish the stable hover with FTR depressed, then release when established. Pull pitch to climb vertically, depress FTR passing TDP to set the accelerative attitude, then release and monitor the acceleration and no sink. Company SOPs might then include using GA mode passing 55 KIAS, to establish a Vy climb at 750 ft/min. In turbulent conditions it may be necessary to make minor cyclic inputs in the initial climb, but at night I’d suggest doing that against the force, and not use the FTR.

[hargreaves99]

In some types (eg EC155) you would not need to use the Force Trim Release at all. It has "follow up trim", making such departures very easy.

[212man]

In some types (eg EC155) you would not need to use the Force Trim Release at all. It has "follow up trim", making such departures very easy.
Exactly, and the inbuilt transition from 'follow up trim' to 'cruise mode' actually raises the nose, and sets an attitude that should achieve Vy. In my response I was trying to keep it S-92 based, and address the questions about Vmini.

[Mee3]

The 225 has go around button to automatically reach cruise altitude. Surprise if the 92 does have equivalent and does not required to be used in standard operating procedures.

[212man]

The 225 has go around button to automatically reach cruise altitude. Surprise if the 92 does have equivalent and does not required to be used in standard operating procedures.
The standard O&G S-92 cannot be coupled below 55 KIAS (except Rad Alt on its own). With the SAR AFCS it can do a transition up from the hover.

[albatross]

The standard O&G S-92 cannot be coupled below 55 KIAS (except Rad Alt on its own). With the SAR AFCS it can do a transition up from the hover.

What happens if you push the GA “Go Around” button at the hover?

[helicrazi]

What happens if you push the GA “Go Around” button at the hover?

Nothing on a O&G machine from memory

[212man]

What happens if you push the GA “Go Around” button at the hover?
Nothing!

[[email protected]]

Most modern autopilots won't engage the mode unless it is inside parameters - if the GA mode specifies min IAS/TAS of 55 Kts then below that computer says Nooooo:)

[PlasticCabDriver]

Min IAS couple on the EC175 is 30kts, but it will engage GA in the hover. If no AP presets already made it will automatically select Vy and 1000ft/min RoC, otherwise it will use the presets. One of the reasons we don’t routinely use it from the hover is that if you are OEI below Vtoss (which in a 175 on the N Sea is always 40kts) it will prioritise getting to that Vtoss, which may result in a a rate of descent. However, it gets to Vtoss pretty quick so under the vast majority of N Sea conditions you would be unlikely to see much RoD if any. SOP is to engage GA at Vtoss.

Helpfully, if there is no lateral mode already coupled, then it will also roll wings level as well as accelerate and climb. It does that well enough and quickly enough to use as a Get Out Of Jail Free card in disorientation scenarios similar to that being discussed.

[albatross]

Nothing!

Thanks for the confirmation. I also was trying to remember.
I remember seeing a Demo of the SAR setup in the sim. Hence my confusion.

[212man]

Helpfully, if there is no lateral mode already coupled, then it will also roll wings level as well as accelerate and climb. It does that well enough and quickly enough to use as a Get Out Of Jail Free card in disorientation scenarios similar to that being discussed.

​​​​​​​It also has a distinct recovery mode too - no?

[PlasticCabDriver]

It also has a distinct recovery mode too - no?

Yes, AP RECOV. Double click on the AP engage button on the cyclic. In simple terms, it will recover the aircraft to straight and level. Both AP RECOV and GA seem to have similar reaction times, and work just fine, but GA will put you in a climb.

[212man]

Yes, AP RECOV. Double click on the AP engage button on the cyclic. In simple terms, it will recover the aircraft to straight and level. Both AP RECOV and GA seem to have similar reaction times, and work just fine, but GA will put you in a climb.
cheers, thanks for the update

[BushrangerRed]

Somatographic illusion is rare in helo ops, but not unheard of. Particularly on high wind low visibility transitions to forward flight off offshore helidecks. The ‘feel’ of achieving Vtoss rapidly after departing the hover, sometimes with poor horizon but excellent lateral visual cues, coupled with the attitude pitch up from accelerative to speed stable attitude (on the S92 sometimes 15-20 deg pitch up) does catch one out from time to time. Not to say somaatogyral issues aren’t also
at play.

[212man]

Somatographic illusion is rare in helo ops, but not unheard of. Particularly on high wind low visibility transitions to forward flight off offshore helidecks. The ‘feel’ of achieving Vtoss rapidly after departing the hover, sometimes with poor horizon but excellent lateral visual cues, coupled with the attitude pitch up from accelerative to speed stable attitude (on the S92 sometimes 15-20 deg pitch up) does catch one out from time to time. Not to say somaatogyral issues aren’t also
at play.
I don't want to be argumentative, and I'm not an aviation physiologist, but I'm pretty sure that what you are describing is not SGI. SGI requires a sustained acceleration in the longitudinal axis, which combines with the Normal (as in at 90 degrees - not 'the usual') gravitational force, to produce a resultant force.This resultant force acting on the vestibular system creates the sensation of pitching up, or down. By definition, if you are taking off into a strong wind and accelerating to Vtoss, you are not experiencing a sustained acceleration, simply pitch changes, which I agree can lead to spatial disorientation but not from SGI.

If an aviation medicine expert wants to correct me, I'm happy to be so

[HeliComparator]

Min IAS couple on the EC175 is 30kts, but it will engage GA in the hover. If no AP presets already made it will automatically select Vy and 1000ft/min RoC, otherwise it will use the presets. One of the reasons we don’t routinely use it from the hover is that if you are OEI below Vtoss (which in a 175 on the N Sea is always 40kts) it will prioritise getting to that Vtoss, which may result in a a rate of descent. However, it gets to Vtoss pretty quick so under the vast majority of N Sea conditions you would be unlikely to see much RoD if any. SOP is to engage GA at Vtoss.

Helpfully, if there is no lateral mode already coupled, then it will also roll wings level as well as accelerate and climb. It does that well enough and quickly enough to use as a Get Out Of Jail Free card in disorientation scenarios similar to that being discussed.

Surely if you go OEI low and slow, you want to get to Vtoss quickly. It should probably result in a rate of descent unless you are light. If you don't accelerate to Vtoss quickly, you will lose more height.

However time and time again we see that oil and gas accidents are caused by crew disorientation. Accidents are not caused by engine failures. And yet it seems there is still some prioritisation of engine failure risk over crew disorientation risk. Are they crazy?

[hargreaves99]

It's the same with ab initio training, spending hours and hours doing engine failures, partial power loss, hydraulic failures etc

And when you look at the accident reports, most accidents are caused by pilots hitting things in perfectly servicable aircraft (the ground, fences, trees, etc)

the CAA are living in the dark ages

[60FltMech]

I finally read this report, sounds like almost a carbon copy of the UH-60M incident in Mobile Bay several years back, although they narrowly avoided the same loss of life.

As non-rated crew, I’ve determined to:

(1. Not allow myself and my crew to depart in terrible weather conditions, make my concerns known.
(2. IF there’s an IIMC event, I’m bringing my scan inside to the PFD to cross monitor airspeed, rotor speed, attitude and positive rate of climb.

Just because I don’t have access to the controls doesn’t mean I can’t contribute.

As to my first point, I’m well aware that it’s easy to say what I’ll do when faced with pressure (real or self induced) to accomplish a flight, and there have been times where I SHOULD have said something but didn’t. Other times I DID say something, and it was well received by the crew and we delayed departure for better weather (or didn’t leave at all). I think verbalizing and even typing it down here helps reinforce the mindset though.

I have to say I’ve been blessed for the most part with crews that make it easy to make the right call. In my experience, the close calls with weather came from complacency, being with a crew that I had worked with for years, excessive professional courtesy kept me quiet a few times.

Other times, it was an unfamiliar crew mix and before I could even recognize it, rules were being “bent” to have “fun”. Both were sobering situations, ones I’d like to avoid going forward.

FltMech

[SASless]

From a pre-World War II pilot.....The emergencies you train for almost never happen. It's the one you can't train for that kills you. (https://www.azquotes.com/quote/681734)
Ernest K. Gann (https://www.azquotes.com/author/23135-Ernest_K_Gann)

​​​​​​​He might have added....the one you do not train for kills you.