03.03.2010, 12:59
i always thought the climb was better and maybe the top speed could be a bit better than what UP has modeled, but how or where are you getting 390MPH as a max speed at SL?
It could be misleading to adjust all speed/power/climb parameters based on "/hg alone, and i know you will probably explain this a bit more in detail later.
I tend to also look at HP/rpm over the altitude ranges as well as the full throttle height. The full throttle height usually gives you the best indication of where top speed is achieved, however getting more mercury out of the engine might actually mean that full throttle height is lowered.
For example:
If a plane has a max rated pressure of 57" then usually the plane can achieve this pressure rating with out using all of the throttle. As you know, the plane climbs and the manifold pressure drops, so the pilot will increase throttle/supercharger to compensate and make sure the plane is using max rated power.
Eventually the plane gets to an altitude where the throttle arm can no longer be pushed forward (full throttle height) and generally we see the plane at its max speed. Increasing the engine rating to 75" would allow the pilot to use more throttle at lower altitudes, and generally we see a lower full throttle height because of this, unless the throttle arm is adjusted to compensate for more throw to allow for higher boost levels.
I've read the P-51D was capable of 90" at 3000 rpm but was never rated as such, similar to how P-40's Allisons could push 70" with the proper fuel and rpm settings.
It could be misleading to adjust all speed/power/climb parameters based on "/hg alone, and i know you will probably explain this a bit more in detail later.
I tend to also look at HP/rpm over the altitude ranges as well as the full throttle height. The full throttle height usually gives you the best indication of where top speed is achieved, however getting more mercury out of the engine might actually mean that full throttle height is lowered.
For example:
If a plane has a max rated pressure of 57" then usually the plane can achieve this pressure rating with out using all of the throttle. As you know, the plane climbs and the manifold pressure drops, so the pilot will increase throttle/supercharger to compensate and make sure the plane is using max rated power.
Eventually the plane gets to an altitude where the throttle arm can no longer be pushed forward (full throttle height) and generally we see the plane at its max speed. Increasing the engine rating to 75" would allow the pilot to use more throttle at lower altitudes, and generally we see a lower full throttle height because of this, unless the throttle arm is adjusted to compensate for more throw to allow for higher boost levels.
I've read the P-51D was capable of 90" at 3000 rpm but was never rated as such, similar to how P-40's Allisons could push 70" with the proper fuel and rpm settings.