Originally Posted by
Pilot DAR
The aircraft must carry inflatable lifejackets, but if the occupant is wearing an approved immersion suit they don't need to also wear the lifejacket. I had pointed out that while wearing an immersion suit, it might be difficult to don and later inflate a life jacket with the lessened mobility while wearing an immersion suit.
Not sure I understand this point properly. By "immersion suit", do you mean a device designed BOTH to protect against hypothermia AND provide buoyancy?
I ask because the usual (UK) definition I have always been taught is that an immersion suit (combined with suitable underclothing) provides protection only against hypothermia when immersed. Bouyancy is provided by a separate lifejacket.
Evidently, if you drown because you cannot remain afloat, hypothermia protection is no longer relevant.
Some immersion suits (as I have been taught to know them) do have an element of buoyancy at times, but that's due to inadvertently trapped air, insufficient to keep an adult afloat and usually distributed around the suit in a manner that does not safely keep the face out of water and severe windspray.
Therefore an immersion suit AND a lifejacket are advised as complementary survival aids; they protect against different threats to life.