Seat Belts

[TAF Oscar]

Don't know about you, but I find the seat belts in light aircraft to be a right pain, especially the main strap in the old Stressna where it's fixed (not inertia reel), severely restricting movement.

Yes, I know that's the general idea, and no, I am not contemplating going without!

But out of curiosity, are there any cases where the seat belt in a light aircraft has actually prevented injury? I find it hard to imagine them being of any use except in a slow speed ground collision, or are they actually effective?

[Genghis the Engineer]

Well, I don't recall it did any harm when I overran a runway on landing and damaged the aircraft. Without it, I imagine that the yoke would have done my chest no good at-all.

If you trawl the AAIB database, you'll find an accident where the pilot was killed by a maladjusted shoulder harness - it broke his neck. It was in an MW6S I think.

G

[Who has control?]

I did most of my training and post PPL flying in a 152 Aerobat with a 4-point harness. On the rare occasions I used another a/c with just a lap strap, I really didn't feel strapped in. I don't feel secure in a big jet either, I suppose its just force of habit.

[The Nr Fairy]

And on the other side of the coin, a Jet Ranger pilot in Australia was killed when his helicopter rolled over just after lifting.

He'd not done up the shoulder straps on the 4-point harness, and the impact knocked his head against a door frame.

[Saab Dastard]

Genghis,

I am sure that you are right, and I am equally sure that you will agree that one will find many more AAIB reports on light singles where the use of seat belts & harnesses was recognised as a major contribution to the avoidance of any / further / serious injury.

SD

[Cat.S]

Hit a tree stump at 50mph when I was rallying and the belts stretched nearly a foot. Wouldn't have liked to hit the dash/steering wheel with the deceleration forces I felt then. Can't see an aircraft being any different in a forced landing!

[A and C]

In a crash at the PFA rally some years back the sholder harness coming adrift was given as a reason for the death of one of the guys in the front seat.

[Genghis the Engineer]

Saab, yes. My point was about the importance of a properly adjusted harness, rather than to suggest harnesses per ce are often a bad thing. No doubt there's a case somewhere where the presence of a properly set-up harness killed somebody, but I don't know of it.

There's also been a couple of cases in tandem microlights where the lack of a shoulder harness in the rear seat caused the passenger's body to break the pilot's neck.

G

[126.825]

can't remeber the figures but the lovely CAA did a survey with the AAIB - to summize you are actually far safer wearing the belt - i have read numerous cases where injury was caused by the PAX hitting the aircraft but i havent read many where they were seriously damaged by wearing them???

i know what you mean about being uncomfortable though - maybe you should approach the club/school about lengthening them etc?

safe flying :) :D :)

[CaptAirProx]

Remember recently that there was a crash near Oxford in a C150. When the student went around from a PFL and tried to climb away with forty flap the aircraft stalled/spun in from low level. The student survived but the instructor didn't have his shoulder harness on and was killed. Apparently according to the AAIB report he didn't believe in them, so never wore them on previous flights. Sad way to find out.

[TAF Oscar]

Mmmmm, thanks. Looks like they can be effective then.

When I trained in Florida the shoulder straps were never worn, only the lap strap, except for during the Skill Test with the examiner - very similar comment from my instructor about not liking them - not a good habit to be starting off with! Here in NL it is frowned on but to my knowledge not illegal to do this; we are expected to wear the full seatbelt.

I don't find it especially uncomfortable, just very inconvenient in the C172 I drive, as for example the COM1 stack is built into the far right of the panel (with COM2 in the middle), it's very difficult to work when restricted by the seat belt. The PA28's mostly have inertia reel belts which make it much easier.

Fly Safe...
TAFO

[Viggen]

The Grob 115 I am flying is luckily fitted with 4 point harnesses, like a racing car - yes they do restrict movement a little especially when navigating VFR and straining to find a VRP on the other side of the aircraft - however, I tend to loosen the shoulder straps in flight, and tighten them for the takeoffs and landings. IMHO should be fitted to all light aircraft...

[DOC.400]

I do the same Viggen -that's why 'hatches and harnesses' are in the checks!

Felt most unsafe in a Cub when had an engine failure and dead sticked into a field with only a lap strap, read too many AAIB reports where landing fine but heads made contact with airframe on stopping.

[john_tullamarine]

Several points .. regardless of whether we are talking cars, planes, or whatever..

(a) the vehicle structure provides for a survival volume of sorts.

(b) the principal intent of the seatbelt assembly is to keep the occupant within that volume so that the hard bits don't do nasty things.

(c) the intent of upper body restraint (typically a sash belt installation) is not so much to prevent injury but, rather, to reduce it.

If the occupant is wearing only a lap belt, the crash dynamics have the occupant initially moving forward and then articulating (folding) about the now restraining lap belt. The main injury risk is associated with the impact velocity of the arcing head as it impacts vehicle structure .. hence the emphasis on head injury criteria (HIC) assessments/measurements in sled crash tests.

Upper body restraint seeks to reduce this impact velocity to a value low enough to avoid serious brain injury. From a practical point of view, the installation geometry and stretch characteristics of belt webbing mean that the sash is not going to preclude head impact but, with any luck, might reduce the impact velocity (under the design crash case situation) down to something in the vicinity of half the unrestrained impact velocity.

If you are of the school which advocates not wearing upper body restraint components, then you ought to take a look at a representative sled crash test of a lap belt restrained dummy. The slowed down high speed film record is likely to change your attitude very, very quickly ... Similarly, the film record will show the greatly improved situation in the case where upper body restraint is worn.

(d) all of the various design standards relate to specific vehicle impact velocities and characteristics. If the actual crash is much outside the relevant envelope, then the end result usually is that the accident becomes non-survivable.

Even then, there are numerous anecdotal accounts of passenger survival in quite high energy (or highly crushed structure) impacts where casual consideration of the resulting wreckage would suggest that the accident was unsurvivable. One well-reported example of the latter situation was the Sioux City DC10 accident where the flight deck crew survived with comparatively minimal injuries ... but the nose/cockpit area was rolled into a little ball sufficient that rescue workers didn't expect survivors there.

The message is ... seatbelts work pretty well most of the time .. but .. like crash helmets ... they don't work at all if they are not worn by the occupants ...

(e) aircraft design standards require that the pilot be able to do all the bits that a pilot has to do with the seat belt installation appropriately done up. If not, the upper body restraint components are required to be installed in association with an inertia reel assembly to avoid the problem. The practical situation is that after market installations are cheaper without the reel so, as often occurs, the necessary reel assembly is omitted. If your specific aircraft is in this category, perhaps a talk with the owner, operator, flying school, etc., about liability might be appropriate. If that achieves nothing maybe the relevant NAA might be approached via the appropriate reporting procedures ....

(f) the question of airline passenger seats fitted with lap belts is a little more complicated as, for current seat design standards, the seat in front becomes part of the design restraint system.


The best rules to avoid or minimise injury ? ...

(a) rule 1 ... don't crash ...

(b) rule 2 ... don't crash ...

.... and so on ...

[ 23 December 2001: Message edited by: john_tullamarine ]</p>