B-29 Engine/Prop Operation

[colmbo]

As much as possible I try to set MP and RPM as I would/did in real life....part of the fun for me.

On the B-29 I've noticed that at altitude when you reduce RPM the manifold pressure doesn't change.  I haven't operated a 3350 but I do have several hours with Wright 1820s and PW 1830s.  The MP should decline as the RPM is reduced.  The supercharger/turbocharger is a big airpump, if you slow the pump down there is less air pumped, MP will drop.

Also the low RPM stop seems to be too high.  On the Ham Standards on the B-17 and B-24 you can bring the RPM back to 1200.  In fact on the runup when you excercise the props you look to be sure the RPM does drop to 1200 to be sure the prop/governor is working correctly.  On the AH B-29 I was only able to reduce to 2000 RPM until MP was reduced substantionaly, then only able to bring RPM down to 1600 until throttle was reduced enough that the RPM was responding to throttle.

Minor points, have no big effect on the game but in the interest of realism/immersion would be nice to see this corrected.

<S>

[Pigslilspaz]

Thank you for the first hand experience to help make the game more realistic.

[smoe]

As RPM is reduced the engine would use a smaller volume of air. The MP could theoretically retain the same level at different RPM's.

Are the B29 blowers designed for constant MP?

[colmbo]

As RPM is reduced the engine would use a smaller volume of air. The MP could theoretically retain the same level at different RPM's.

Are the B29 blowers designed for constant MP?

When you reduce RPM but leave the throttle unchanged to should see a drop in MP.  I know for a fact it works that way on the B-17 and B-24.  The reason being when you reduce RPM you are reducing the speed at which the supercharger and turbocharger are turning so less boost.

I've noticed in game the B-24 acts that same as the in game B-29 --- no MP drop with RPM reduction.

[Baumer]

There are a few other aircraft that have interesting MP/RPM issues I've seen in the past. I generally have chalked that up to how HTC models engine management. I suspect that if you look at the E6B you will see a drop in fuel usage (and speed) even though the MP hasn't changed, I'll run a test flight later to confirm it.

[icepac]

Manifold pressure on turbocharged planes is decided by the wastegate setting and the throttle.

[colmbo]

Manifold pressure on turbocharged planes is decided by the wastegate setting and the throttle.

Not sure if you agree with me or disagree. <G>

[icepac]

Just put that out there with no attempt at disagreement or agreement.

Throttle position, prop speed, and manifold pressure vary greatly in different planes for the same throttle lever and prop settings.

Once you get into turbocharged engines, you have devices that are used to control manifold pressure once the throttle is opened to the point of producing boost.

My car develops 15 pounds of boost at half throttle.

It also develops 15 pounds of boost at full throttle.

[RSLQK186]

Found through Google Books a B-29 Airplane Commander Training Manual. Looked at a preview of it. Page 70 is an engine operating limits chart.