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Early efforts at sniffing were tried in WW2 as a way of locating U-boats especially the schnorkel exhaust gases. I don't think the technology was sufficiently sensitive at the time. Given the schnorkel vented under the surface whatever gases rose into the atmosphere would have been quite dissipated.
| RAF in the Maritime War Vol 5 p.97 and App V & VIA 1955 post-war review of claimed schnorkel sightings with benefit of German logs with U-boat positions |
| It was found that numerous attacked "schnorkels" were false claims. Probably waterspouts ('willywaws') or whales, with no known U-boats in the vicinity. U-boat logs showed that most schnorkelling was at night and at speeds below 4kts to minimise wake. Claims of exhaust fumes were doubtful as the exhaust pipe ended well below the air intake so gases exited below the water surface. |
And yet we see the same kind of claims about smoke trails made by RN personnel hunting U-boats in the Channel in 1944. They are more likely to be able to differentiate between weather phenomena & smoke trails. Who knows at this distance in time.Hi Ewen
The following is from an article I wrote on the Type XXI U-boat. I think the wartime reports about Schnorkel sightings have to be regarded warily. My comment is paraphrased and not a direct quote. Amazingly when the RAF did the post-war review they were only able to find 3 photos of genuine schnorkels despite the widespread of cameras by 1944/45. The Monthly Anti-submarine Reports and the Coastal Command Reviews contained several pieces on the danger of misleading waterspouts and whale spouts.
RAF in the Maritime War Vol 5 p.97 and App V & VIA 1955 post-war review of claimed schnorkel sightings with benefit of German logs with U-boat positions
It was found that numerous attacked "schnorkels" were false claims. Probably waterspouts ('willywaws') or whales, with no known U-boats in the vicinity. U-boat logs showed that most schnorkelling was at night and at speeds below 4kts to minimise wake. Claims of exhaust fumes were doubtful as the exhaust pipe ended well below the air intake so gases exited below the water surface.
I agree with your 1950's technology comment although I don't have a source.
Sure but the RAF survey was cross-checked with U-boat logs so has some credance. It feels a bit like the claims of sono-buoys reported as getting definite U-boat sounds but when put through a similar subsequent analysis a substantial proportion had no evidenced U-boat in the area. Not criticising the air crew, just very tough judgement calls made under considerable pressure.And yet we see the same kind of claims about smoke trails made by RN personnel hunting U-boats in the Channel in 1944. They are more likely to be able to differentiate between weather phenomena & smoke trails. Who knows at this distance in time.