![]() ![]() In other words, I don't think you should use less than 3000 RPMs when greater than 46 inches MP. There isn't a reason to go above the maximum continuous setting except for combat and I'm sure the warbird was designed with these settings in mind. Above that and it says 3000 RPMs and 61 inches and 3000 RPMs and WEP (68 or 72 inches or whatever). The manual only gives guidance on RPMs and MP when they are LESS THAN 2700 and 46in. If only there was a way to compress the air before it gets to the prop, then the prop could spin as fast as metallurgy will allow. A prop rotating much more than 3000 RPMs starts to disrupt the air too much and there come to be diminishing returns. Hm well the Mustang was designed with 3000 RPM being the maximum and this had been an established limit for warbirds for many years. At lower rpm you can overboost engine so for 2700 keep eye on MP gauge is required, at 2700rpm you can get up to 50" but my sweet spot for aerobatics is 2600 and 45" MP. Maybe you could design the airshow to have high speed maneuvers between the slow moving ones.įirst thing at lower rpm engine produce less heat not more. Probably the nature of the problem is going too slow for too long. But when you have max MP + RPMs LESS than what the engine is designed for, that's gonna break stuff. So really very little stress being placed on the engine and it's designed to operate at 3000 RPMs anyway, so it isn't a big deal. If you have 3000 RPMs but low MP, then the prop is spinning fast but the blades aren't turned into the air creating as much friction (or power). This is called something but I'm not an aeronautical engineer so I forget. Doing this to the engine produces a lot of excess mechanical stress and friction (heat). If you go against the manual and set RPMs too low for your Manifold Pressure then the Mustang will auto adjust the prop speed by turning the prop blades flat against the air until they make enough friction to slow the engine down to the set RPMs. If you really want to vary the RPMs then you're going to have to study all those flight operation instruction charts in the back of the manual. If you fly at 2700 RPMs then you're going to need to never let the Manifold Pressure exceed 46 inches (that's the maximum continuous setting). It is far more likely that the engine is overheating because the RPMs are set TOO LOW. I would think you should keep RPMs at max and vary the manifold pressure. But then again, I have flown the plane inverted until fuel starvation quit the engine, but once righted, it came back w/out problems. Seems like a poor weakness for a fighterplane to have. But then I see other planes doing the same thing w/out incident. ![]() I'm thinking oil? during the low G part, but that's just a second or two. I have used higher power during cuban eights & Immelmans before without problems in dogfighting, it's only during these ballistic dump overs that I'm having the problems. The last two incidences I purposefully used power off dives to recover from the maneuvers and then just glid at best range glide speed to wait for the inevitable engine failure, and there it came. ![]() I'll use about 40" during a speed building dive, but then I'm already going fast because of the dive starting out. No high power settings, 20-30 inches at max when slowing down, but mostly below 15" to almost idle, temp needles are always solidly in the green, right up to the failure, and then that occures way after the maneuvers during basically a level cruise flight to set up speed. ![]()
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