View Full Version : Icelandair rollercoaster (investigation report)

24th Jan 2003, 11:28

24th Jan 2003, 18:54
Neither the incident pilots nor the accident investigators appear to have heard of the somatogravic illusions (and specifically the "pitch-up illusion").

It would seem to me (on a quick read-through) that that was the problem causing the go-round gyrations.

Methink the pitch-up illusion needs more publicity than it got courtesy of the 23 Aug 00 GF072 GulfAir A320 accident in Bahrein

GF072 somatogravic references (http://www.iasa.com.au/folders/Safety_Issues/others/helpout.htm)

(Some of the cited links may be dead because of Pprune server swap-outs.)

27th Jan 2003, 09:21
So what is somatogravic illusion anyway?

And why did this Icelandic Crew have it?

Bobby Guzzler
27th Jan 2003, 13:17
A somatogravic illusion is where you experience rapid acceleration in the longitudinal axis, i.e. pushing you into your seat. The hairs in your ears lean back and it feels like the nose of the a/c is way up in the air - try and have a look at some carrier accidents, when the pilots plummet nose down into the ocean to try and compensate (ouch!). :eek:

27th Jan 2003, 13:27
Shadow - try any search engine with 'somatogravic' and you can learn!

As I understand it in simple terms, forward acceleration causes the tiny 'balance' hairs in the ?inner? ear to be tilted backwards (due to inertia) which has the same effect on the brain as tilting the whole body backwards ie pitching nose up.

The brain (deprived of adequate visual reference) can interpret such forward acceleration as a climb and vice versa. Thus a tendency to push forward to stop the climb as the aircraft accelerates.

As the USAF used to say " Disorientated? - Get on the gauges!"

The human balance system was not built for flying!

Try The Flyer, October 2000 (http://www.wvfc.org/news/00oct.html)

27th Jan 2003, 16:29
Neither the gyros nor the pitot static instruments are affected by somatogravic phenomena. All the pilots need to do is to look at the instruments instead of outside. It's Lesson One in Instrument flying. Very elementary. :p

27th Jan 2003, 16:36
With pilot as your occupation, you should know what somatogravic illusions are! :confused: :eek:

27th Jan 2003, 17:13
G/A - be fair - it IS a big word:D

Bobby G - apologies for the duplication:o

27th Jan 2003, 17:25
The Pitch-up Illusion

It's OKAY Girls, calm down. It was only a rhetorical question to get it back up to the top.

the shadow

27th Jan 2003, 19:30
can happen with any type with no visual horizon,and plenty of push.lost some 118's in Canada due 'low'ceilings depts and the a/craft pitched up initially -then flew into the ground ,as the guys 'pushed'to stop themselves going over the top.
Heads Up display moved too fast ,USAF reconcentrated on the ball Att Ind' for initial pitch att'.
Can happen on any type with plenty of 'acceleration'no visual horizon and not concentrating on the Ball(att Ind).
Case in point,in northern B.C.,lost a Metro on a foggy 'Goaround'that flew into the trees despite a 'posative'initial pitch up(FDR).

28th Jan 2003, 16:20
I'm not sure that it will do any good for amateur surmising over this incident. Incidentally, the link given at the top of the thread seems to be far more comprehensive (and is far more recent) than MJ's link.

One thing IS sure though, that the somatogravic illusions, both in up and down pitch with the large power and speed changes, would have added significantly to the extreme confusion experienced by the crew.

Just glad I wasn't there!:eek:

29th Jan 2003, 11:06
Offcourse the somatogravic effect was a factor in the incident... Setting GA-power, having a high pitchup attitude, being confused, retracting the gear... If you don't know where you are or what you are doing, you will act primitive, which is as a pilot to push on the stick if your pants make you feel that the nose is going up.
I would not underestimate the effects of such illusions, even for the more experienced professional pilot.

29th Jan 2003, 20:22
This and other illusions are covered in the JAA ATPL 'Human Performance' module. We studied it and I remember my ground instructor saying that jet pilots who take off on aircraft carriers are made to put their hands on the dashboard so they do not push forward on the controls. It took them years to figure out why everyone was just heading straight down and ditching into the sea!

30th Jan 2003, 06:11
If anyone could get hold of a short authoritative exposition on this silent killer, it would be a worthwhile addition to Capt Pprune's Technical and Safety Index.

I'm still finding that there are a lot of pilots out there who don't have any substantive AvMed grounding and just haven't heard of the phenomena (or if they did, it just went in one ear and out the other - without any somatogravic pause for confusion).

There are many suspected examples of pitch-up illusion - apart from the military ones and GulfAir 072.

the Shadow

30th Jan 2003, 10:27
It's a good point shadow, I think I may have suffered it a bit during my IF training; night, snow, on the go-around. Lucky my instructor was with me.
Only found out about it in my next block of ground school!

Sleeve Wing
30th Jan 2003, 14:15
Must admit that I'd never heard of this "somatogravic" phenomenon either but that's probably because "pitch-up illusion" was self- explanatory ( and well-known to early jet jocks) in the olden days.
Probably why the Icelandic guy was so confused..... and because I never got to read all the new-fangled CAA stuff on Human Performance.

BTW, fly-half, one puts one's hands on the "cockpit coaming", above the Instrument Panel of the aeroplane, probably first used in the UK during the early sixties for Buccaneer carrier takoffs.

Better remember that for your first airline/ Air Force interview.........
dashboards are fitted to cars!

Regards (with tongue in cheek!)
Sleeve. ;) ;)

30th Jan 2003, 17:24
This is one I'd like to run through on the simulator to learn:[list=1]
how to avoid it
get things back in order when the automatics run off in the wrong direction.

30th Jan 2003, 21:19
PEGASUS says:"Of course the somatogravic effect was a factor in the incident... Setting GA-power, having a high pitch up attitude, being confused, retracting the gear... If you don't know where you are or what you are doing, you will act primitive, which is as a pilot to push on the stick if your pants make you feel that the nose is going up. I would not underestimate the effects of such illusions, even for the more experienced professional pilot"

Pegasus, I can put you into a Cessna with blindfolds and maneuver the airplane in such a way that you would tell me that the airplane is climbing when in fact the airplane is in a steep nose down spiral. It's covered in basic instument course 101.

This near fatal incident is not a myth. It's easily explained: These 757 pilots in IMC had interrupted their instrument scan, and the PF had instinctively reacted to sensory illusions and overcontrolled his airplane from 40 degrees nose up to 49 degrees nose down. He should have known better not to pull and push on the yoke by the seat of his pants. In IMC the PF must stay glued to his instruments. It's a total concentration effort, and a strong belief in your instruments. End of story.

Pilot Pete
30th Jan 2003, 22:13
I remember the initial report being circulated to us at work shortly after the incident. Flying the 757 out to one of the Canaries on a fine day we sat there in the cruise just reading through it in awe. We came to the conclusion that 49 degrees nose down must have looked vertical...........................even on the instruments!

Terrifying. Plenty of lessons for us all to take on board.


31st Jan 2003, 13:40
"This is one I'd like to run through on the simulator..."

I would caution that (obviously) you are not going to get many of the physical cues/distractions in the sim because it will be unable to reproduce any sustained accelerations.

I would also suggest that you will find it difficult to see how the crew managed to get it wrong in this manner without going upstairs and trying it for real (A/P, A/T & AFDS confusion excepted).

As an aside, am I the only one who finds the Boeing-style 'crosshair' type of flight director inferior to the 'v-bar'? You can get a very large 'demand' from the pitch/roll bars when only a small correction is required. On the 'v-bar' directors I have flown with, they show you the correct attitude required by the AFDS at that moment in time, not a 15 degree pitch demand to descend 50 feet. I think the Boeing types also have a time-dependent factor which increases the F/D command.

31st Jan 2003, 15:27
I'll do without the full suite of physical sensations, especially hitting the ground, and engineering will doubtless prefer not having to do a structural check after each such exercise in a real a/c.

While a simulator scenario may not reproduce the precise sensations, there are still valuable lessons to be learned here.

3rd Feb 2003, 06:08
Seems to me that it was blind adherence to automation gone mad. All the pilot had to do was to click off the FD and A/T and do a leisurely raw data go-around using basic ADI and manual throttle to a sensible body attitude. Nothing could be more safer or more simple. Unthinking reliance on automatics has killed more than one crew and passengers and frightened a few hundred more. :cool: