Ditching spamcans

[ft]

The C172 POH recommends ditching in a level attitude at 300 fpm V/S @ 55 KIAS.

Any thoughts as to why, as opposed to stalling it in at Vs with the tires skimming the surface?

My best guess is that it is to avoid having a nose up attitude causing a sharp pitchdown as the aircraft impacts the water, as that might damage the spongy components strapped into the seats?

Cheers,
Fred

[Clear_Prop]

My best guess is that it is to avoid having a nose up attitude causing a sharp pitchdown as the aircraft impacts the water, as that might damage the spongy components strapped into the seats?

Haha, LOL!

I think the emphasis is on not putting the plane in a
dynamically changing attitude, because of the unpredictability of the water surface.

Trying to stall it in would be fine if you have a flat calm surface and you can actually pull it off - but if there's any swell or chop the water level might fall away from underneath you just at the critical moment, such that your profile is changed to a state much worse than desired - in big enough swell the a/c could go post stall and dump you in the drink quite visciously! However, in a steady descent with the aircraft in a stable attitude, the final ditch will be pretty consitent regardless of swell (unless you're really unlucky and ditching into very rough sea).

Also what looks flat and calm at 200 ft might look completely different at 2 ft.

Any seaplane drivers out there with more to offer?

[FlyingForFun]

Another factor might be that it is very difficult to judge your height above the water, especially with no land or ships nearby as a reference. The only thing you could use to assist with this judgement would be the size of the waves - but of course wave size varies so much that it would be virtually impossible to flare at the right height.

(Incidentally, sea-plane pilots have this problem, even when they are near to land, on "glassy water", i.e. on a still day when there are no waves. The technique used here is to flare before crossing over the shore, while you still have a good visual reference for judging your height. You then set a moderate amount of power, hold the attitude constant, and wait - making absolutely no attempt to flare further before landing.)

FFF
-----------

Edit to answer Clear-Prop's question. I'm certainly not an experienced sea-plane pilot, having got the rating last month and not used used it since, but as I suggested above, this probably isn't very comparable to normal sea-plane operations. I can't think of too many reasons why you'd ever want to land a sea-plane that far away from land or ships - and the brain will subconciously use all this information when judging the height above the water.

[604guy]

Speaking off the top of my head I would guess the reason is to ensure that you are contacting the water in full control of the a/c. If you were to attempt to contact the water in a stall and were a bit off in your judgement you run the risk of the a/c nose falling and the resulting attitude when contact was finally made would not be the most conducive to ensuring a successful evacuation. Basically as you have suggested.

As for POH’s, particularly those of GA aircraft, you must remember too who writes them. 50% is written by company lawyers, 25% by the sales staff which leaves only the remaining 25% to be written by the folks that know anything….the test pilots and engineers.
;)

Regards

[willbav8r]

I think Bob Hoover said that "flying the plane into the crash" is what kept him alive after several prangs......

Of course, ditching in anything less than a v calm surface has to be pretty damn difficult?

[ft]

Thanks all. Exactly the kind of discussion and points of view I was looking for. Following directions without understanding the reasons for them being as they are is something I'm not very fond of.

604guy, LOL on the POH writing! Good thing that the airlines have SOPs on top of that... written by a grumpy old chief pilot to ensure that he will not have to unlearn any of the bad habits he learned during flight training in 1934! ;)

Cheers,
Fred