dwg
Posts: 319
Joined: 1/22/2008 Status: offline
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quote:
ORIGINAL: Commander Stormwolf Dinah carried a giant drop tank that looks (and weighs) pretty close to a torpedo.. so did the Saiun (Myrt) The Ki-46-III was the only drop-tank equipped version, so that limits you to development starting in 1943 or later before you start. The size of the -III's drop tank is variously given as 101 or 120 gallons, with avgas at 6lb/gallon, that gives a rough weight of 600 to 720 lbs (caveat, I'm not clear if the drop tank size is in Imperial or US gallons, if Imperial increase the weights to 720 to 864lbs). However the Type 91 aerial torpedo had a minimum weight of over 1,700lbs on the Type 91 Mod 1, increasing to over 2,000lbs on the Type 91 Mod 7 and the Type 4. Your drop tank that supposedly proves the Ki-46 was stressed to carry a torpedo actually turns out to be half the weight. quote:
you can stick a torpedo on practically anything.. And yet strangely I was reading just this afternoon how the Westland PV.3 torpedo bomber had to be abandoned as a military aircraft when the Admiralty stopped development of the lightweight 1,000lb aerial torpedo it was supposed to carry. This was a purpose-designed torpedo bomber, but it simply could not carry a full size aerial torpedo. An aircraft is roughly speaking two girders, one the wing, the other the fuselage. The lift on the wing acts on both to hold them in the air, but they can easily be overstressed and fail. Think of a plank balanced between two supports, if you hang weights on it then it will start to bend, hang enough weight on it, and it will fail catastrophically. It's even more complex for aircraft, because they aren't dealing with a static 1G straight down load, they have to account for manoeuvering and turbulence too. The dominant part of designing an aircraft up until quite recently wasn't the aerodynamics, it was the stress calculations, which had to be done by hand for every joint in the structure, every time the design changed, until computers became able to handle the calculations. Aircraft structures are designed for their operational loads, a limited growth margin (often part of the spec) and a design margin to cover sudden stress on the fuselage, whether that be from microbursts, windshear or plain old pilot stupidity. And that additional strength is kept to a minimum, because strength in the structure translates directly into extra weight in the structure, and either lower performance, or the need for a bigger engine and wing to carry them. The feedback loops in aircraft design are vicious. Exceed the stress margins and your aircraft is now at risk of quite literally falling apart in the air due to overstressing the fuselage or wing, and I can list a substantial number of aircraft that have done just that. There are very few WWII aircraft below medium bomber size that could freely have 2,000lb added to their load without taking them over their design margins, and even if they were capable of having that load added, it would need to be transmitted into the fuselage along a load path capable of taking that stress level, which would require a considerable redesign if that load path didn't previously exist. (As a current example, India is having to specifically modify Su-30MKIs with a purpose-designed belly hardpoint in order to carry the air-launched BrahMos cruise missile, the standard hardpoints for the Su-30, which can carry the big 1,300Kg Kh-31, simply can't handle the mass of the BrahMos) Equally you have to consider the stressing of the wing design versus the operational environment. The stresses on a high-altitude wing are quite different to the stresses operating on a wing at low level, which experiences much more buffetting (and even if the two wings are operating at identical speed over the ground they'll be operating at substantially different Mach numbers, which means different designs are optimal). Put a wing in the wrong environment, especially with substantial extra load hung from the aircraft, and you are inviting it to fail. Similarly engines are optimised for specific operational heights.
< Message edited by dwg -- 5/22/2012 6:26:26 AM >
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