engineer
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A few more points but, in summary my take is that rigid airships were clearly not cost-effective by 1941. The case for blimps as ASW assets was better than airships. I think blimps versus conventional aircraft may actually turn on higher order effects.
1) The original search plan for the Macon's involved the airship advancing at 50 knots while two scout planes paralleled the airship's course flying at 100 knots 60 degrees off the main course, timing their flight so they would turn back to airship and then repeating the zig zag after spotting the mother ship until they were recovered when fuel ran low. Then a fresh pair of scout planes would relieve the first two. Under clear weather and flawless execution, the Macons would sweep a swatch of ocean 240 (not 120 - my bad) miles wide (all this presumes 40 mile visibility and a search altitude of roughly 5000 feet. So under optimum conditions, a Macon could search nearly 160,000 (not 80,000 my bad) square miles of ocean per day. The obvious rejoinders apply that weather won't cooperate, mechanical casualties may disable aircraft and recovery systems, etc. Persistance was key asset since the airship could remain aloft for several days at a time and would not have to return to base after a short time in the patrol zone.
2) A PBY had a search radius of about 800 miles and a cruise speed around 140 knots. http://www.history.navy.mil/branches/hist-ac/pby-6a.pdf For argument's sake let's concede that the area of interest is the outer half of that patrol. So each PBY would cover 40 miles x 800 miles (400 out and 400 back) in it's loop, 32,000 square miles. Our squadron of 12 PBY's would be able to cover 12x32k or 384,000 square miles. It would be subject to the same weather caveats as the Macon, but by distributing the search over 12 independent platforms instead of one primary and up to 5 dependent platforms, the PBY squadron is more robust in terms of being more resistant to a single point of failure that would disable the squadrons search ability.
3) On the Blimp side, obviously the blimps were far less expensive than the Macon in terms of cost, crew, and ground support. Blimps carried some of the first deployed magnetic anomoly detector (MAD) gear. I also think that Bruce Powers' point about detection is an asset, too. At least in WitP, a detected sub has much lower odds of a successful attack than an undetected sub. The other part of the question gets to the USA way of war in WW2 with massive quantities of everything. Afterall, the Manhattan Project entailed developing two, indepedent nuclear weapons technologies. Given the pre-war base of experience in LTA and the uncertainties of how the ASW campaigns would proceed, would allocating resources to develop a large LTA ASW arm be a reasonable risk mitigation so the Allies would have another type of threat against Axis submarines? The Battle of the Atlantic was a big deal in 1942 and early 1943 so the perceived risk of a redundant ASW weapon was smaller than the risk that the Germans would blockade the Atlantic.
I think the numbers speak for themselves that patrol planes are a more effective method of naval search. In hindsight, we might conclude that PBY's were better at killing subs than blimps, but it's hard to quantify the attacks that blimp overwatch prevented. There's also the redundancy aspect of having more than one type of aerial ASW platform.
< Message edited by engineer -- 7/22/2009 6:25:54 PM >
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RE: U.S.S. Macon - 
RE: U.S.S. Macon - 
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