On a traditional car this creates what is known as manifold vacuum. This has the effect of limiting the amount of air (and by default the air/fuel mixture) into each cylinder, thereby effectively limiting the produced power and indirectly the RPM.
On traditional carburetors this is part of the carb itself, with fuel injection it is part of the throttle body.
#P 51 cockpit install#
In order to prevent this from leading to the destruction of the engine, and to allow some form of control over the engine RPM, we install a throttle plate of some type in the intake system. We will think in terms of a car engine at this point as it's basically the same as an aircraft for this discussion and besides it's conceptually easy to relate to.Īn engine will attempt to draw in as much air as possible during the intake stroke. Now you would have a screw that (for a given rotational speed) could be made to drive itself into the material at varying speeds without having to change the rotational speed at all. Now further imagine that the angle (pitch) of said blades could be changed at will. Now imagine a propeller as a "screw" that has been machined down to only a few little legs that once were an entire circle around the screw. In the machine screw, the screw might have to turn thirty or forty times to travel one inch, where with the wood screw, the same may happen after only ten to twelve turns. If the concept of "pitch" is not known, think of two screws, one a machine screw with a fine thread and one a wood screw with a coarse thread. Sometimes (if not always) this is called a constant speed prop. This allows two things, one the engine will almost always be running at a higher RPM where it is more reliable, (less likely to stall, or sputter) and two, the engine/prop combination will not exceed the limits of their respective components. With this in mind, most aircraft engines utilize an adjustable pitch prop. This has less to do with rotation itself, but rather the masses involved with the pistons reversing directions at the end of each stroke, and the associated inertia(s) involved. The engine itself has a limit of RPM where it too will self destruct.
#P 51 cockpit plus#
Plus at some point, the tip speed will exceed the speed of sound, opening up a whole new can of worms. Well, the blades are fairly heavy and spinning quite a bit faster than your arm. If you ever held something fairly heavy and swung your arm around you would feel this effect. This has to do with the tip speed, the act of constantly changing direction (it spinning remember) and the forces generated at the hub by the blades trying to fly away. At a point beyond that limit the prop will fail by actually blowing itself apart. The answer will take a couple of steps, and a disclaimer.ĭisclaimer: I am not a pilot, nor an aircraft mechanic, however I do know a thing or two about engines and aircraft in general, and I and my family were in the engine monitoring instrumentation business for 42 years.Ī propeller, or prop, has an RPM limit. I personally don't think it is good enough for the masses, but, I will give you all a chance. I replied to Jim via PM and he insisted on my actually posting the answer on here so others could read it.
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