Forced landing on beach

What about C of G and pitching moment – there is reasonable evidence that C of G has a significant impact on pitching moment. From my own experience of dinghy sailing (not that much different) getting the weight aft has a significant impact on pitch poling running down waves. The length of the fuselage must also have an impact on the pitching moment – its very difficult to pitch pole a longer racing dinghy than a short one and of course the speed ulitmately determines the amount of energy that is available to cause the aircraft to pitch about its C of G.

If the nose pitches into the water first then presumably the whole of the pitching moment is about the front of the aircraft, requiring a lot of energy to lift the tail to rotate over the nose. In the same way in a sailing boat the centre of effort is about the mast which is well forward, so typically as the boat pitch poles, the front of the boat digs into a wave, the mast keeps going and the boat effectively rotates about the mast which continues over the front of the boat as the nose is forced deeper into the water.

In an aircraft intuitively with the gear down I would have thought the effect would be to cause the aircraft to initially pitch down forcing the nose into the water, whereas without the gear up the aircraft is going to behave dependent on how much the nose has already pitched down into the water. I would have thought given identical landing profiles with the gear down the aircraft is more likely to pitch forward.

- using the wheel brakes considerably reduces the risk of a flip – they recommend setting the parking brake.
- if the aircraft has retractable gear and the POH doesn’t say anything about ditchings, extend the gear (and set the parking brake).

I find this bizarre. Other than perhaps on a totally still lake, what difference would the brakes make? And extending the gear? Does anyone know what their thinking – or better, research – behind these recommendations is?

I find this bizarre. Other than perhaps on a totally still lake, what difference would the brakes make? And extending the gear? Does anyone know what their thinking – or better, research – behind these recommendations is?

My information is from a booklet about emergencies – part of a booklet series on flight safety prepared jointly by the Swedish CAA and several GA organisations including AOPA-Sweden.

Ditchings are somewhat better “tried out” than landings in forests. Experience shows that the aircraft should not be landed so that the tail touches the water first. If the tail breaks the water surface too early, it is drawn down and the angle of attack increases so that the airplane will pitch up sharply, stall and touch down hard. Land as usual on the main gear, but make sure you have the wheels braked.

Without braked wheels there will not be sufficient aquaplaning for a softer deceleration – the result can instead be a nose-over. Before ditching, apply the parking brake already on downwind or long final. During the flare, make sure that the nose gear does not touch down first.

Opinion is divided on whether a retractable gear should be extended or not. Contributing factors in addition to the design of the landing gear include whether it is a low-, mid- or high-wing aircraft. If there is no other information in the POH, extend gear and ensure that the wheels are properly braked.

There are no sources given, but the editor of the booklet is a well-known and respected profile in Swedish GA circles with more than 45 years experience and 8000+ flight hours when this information was prepared. Not that it is any guarantee, of course.

Landing tail low in the Hudson definitely didn’t drag the Airbus nose up.

What could “drag the tail down” and not the (braked) wheels?

That is a very interesting video.

I have watched it a few times stopping and starting. I hadnt appreciated that the spats are pretty substantial and after the first bounce it seems clear they cause a huge amount of drag and it seems to me almost inevitable the aircraft has to pitch forward and rotate around that point. In short the spats certainly dont help.

Seeing that I would need some convincing to lower the gear which also doesnt seem to be the commonly held opinion of the “experts” that post on this subject.

Definitely wheels on sand, and a bounce, rather than a ditching. Fixed gear seem often to tip to near vertical, then come back, rght-way-up on ditching.
The only ditching expert I’ve heard of opened canopy, stood on seat, rolled inverted at low level, and jumped. WW2 Atlantic convoy catapult Hurricane pilot, who chose not to bale-out on case he couldn’t be found, and thought air intake would drag plane under when ditched.
I think he did it more than 10 times. Information from newspaper obituary when he died at an advanced age.

This report while old seems still relevant.

http://naca.central.cranfield.ac.uk/reports/arc/rm/2917.pdf

U/c up is the view with some other interesting conclusions.

alioth 02-Jun-15 16:40 #30
Taking a ditching course the consensus there was that a non retractable will most likely flip
If it does, it doesn’t seem to affect the outcome: the egress rate is over 90% for ditchings.

http://www.equipped.com/ditchingmyths.ht

Unless of course you land on shallow water and find the airplane is upside down with a sliding canopy. Not enough water to right the plane nose down.

The bottom line is that most SE fixed gear have a very low stall speed. So with any kind of moderate headwind the forward motion should not be too bad. Yes while they flip most will come to rest 30-40 nose down.

Ditching myths had no empiracal evidence about landing with or without the gear extended. It asked to be shown proof. Meanwhile the very extensively studied, with models as well as real aircraft, done by Fuji’s submission in http://naca.central.cranfield.ac.uk/reports/arc/rm/2917.pdf suggests differently for best outcomes. It was interesting that high wing in that report had a less than welcome outcome compared to mid wing but bit better than low wing depending on the wing loading. I believe some of their data involved more Transport category aircraft than small GA. The principles are the same though, except for stall speeds which I think is why small GA planes have a comparable outcome., even with gear extended and high wings whose cockpits would be underwater.

Prior to taking the Ditching course “Survival Systems” I had read up on Paul Bertorelli’s article and it made sense for overall survival but I think the naca study proves with with fact why.

I think there is possibly a lesson from all this – in a tail dragger it may be best to avoid landing in shallow water because the aircraft will almost certainly pitch and there may be greater problems with egress and stress caused by the higher G – given the alternative opt for water that is a bit deeper and be ready of course to evacuate as quickly as possible. It also seems to me with retracktable undercarriage you are better off leaving it up, albeit just perhaps with the absence of spats there may be a better chance of the u/c dragging through the water without causing the aircraft to pitch and at the same time absorb some of the energy.

Would others agree with those conclusions?