Easy reading guide on Manifold pressure - Page 2 - ED Forums


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Old 07-02-2020, 03:06 PM   #11
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Originally Posted by Yoda967 View Post

I'm more concerned about contemporary info than what can be done in the sim.

This link to the testing done in 1943 on the LF Mk IX specifically says the limitation that applied was +12 boost at 3000 RPM.


The oft-maligned Pilot's Notes for the Mk IX (from 1946) also state that at training and normal loads, takeoff power is set to between +7 and +9 boost, with power increased after takeoff to +12.

I admit I may be wrong about the +11.5 boost, though I would question why the need to placard the engine limitation as applying up to 1000 feet if there's no expected difference above that.
I just linked screen from pilots notes which claims 18 lbs boost for take off.
Like i said merlins 61 nad 63 were limited to 12 lbs.
merlin 66 has 18 lbs limit.
I think they were referring to how long you can hold on take off power before you need to reduce it, after take off plane enters climb so let assume that spit get to 170-180 mph and climbs 1000 ft up then pilot had to reduce power.
In other planes like p-51 61" take off power is limited to 5 min i think.
similar for P-47
And this link you posted are referring only to tests limits under which tests were done.They were testing different engines new and old too, so they set 12 lbs for same test conditions.
And BTW take off power limit has absolutely nothing in common with handling of the plane in take off roll. Power limit refers to power levels where engine can be operated safely acording to requirements.
It is so fun, 18lbs in spitfire, launching like a rocket
Are you referring to this part in pilot notes, because i could not find anything else in Take off segment.
7 - 9 lbs for take off with normal loads, but you need to increase to 12lbs to reduce spark fouling.But still nothing that 12 lbs is max power for take off.
I still claim that Merlin 66 has 18lbs take off power limit.

Last edited by grafspee; 07-02-2020 at 03:45 PM.
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manifold pressure

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