Manifold Pressure at idle

The Yak Aircraft Corporation (formerly the A.S. Yakovlev Design Bureau JSC) is a Russian aircraft designer and manufacturer.

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Darrell Lush
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Manifold Pressure at idle

Unread post by Darrell Lush » Mon Jul 29, 2013 6:30 pm

Had a bit of a brain fart today. I haven't flown my Yak for some time now so I thought I'd take it for a spin. I do not remember ever seen the MP below 20 cm at idle and only up to 40 cm at 70%. So I did a take off roll to monitor the MP and lo and behold she went right up to 80 cm as I am used to. Taxied back to the holding point and did a short flight. At cruise, came back to 70 cm no problem.

What MP reading do you guys get at idle ? ie 42%
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Re: Manifold Pressure at idle

Unread post by paulw » Thu Aug 01, 2013 12:14 pm

Darrell Lush wrote:Had a bit of a brain fart today. I haven't flown my Yak for some time now so I thought I'd take it for a spin. I do not remember ever seen the MP below 20 cm at idle and only up to 40 cm at 70%. So I did a take off roll to monitor the MP and lo and behold she went right up to 80 cm as I am used to. Taxied back to the holding point and did a short flight. At cruise, came back to 70 cm no problem.

What MP reading do you guys get at idle ? ie 42%
Hi Darrell

I had a look this morning as I didn't know and didn't want to comment earlier.

What I saw on CXK.
During Run-up at Holding point: approx 60cm at 70%. I think just a little less.
I don't remember during flight, but I think also in the region of 70 at 100% and then just after take off coming back to 82% RPM, the pressure dropped to about 47 as you also go back on the throttle. I am not 100% sure though.

However, when doing the "run-up" after flight before shutdown (64% for 30sec and 43% for 15sec), I checked the manifold pressure specifically as you raised this.
Pitch full fine, throttle At 32% approx bottom of quage 30 and popping below even but coming up to 32cm
Throttle to 28% or so showed an increase to actually about 32-34cm
Going 64% raised manifold presure to about 40cm.
I did this 2-3 times and was the same everytime.
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Darrell Lush
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Re: Manifold Pressure at idle

Unread post by Darrell Lush » Thu Aug 01, 2013 8:42 pm

Thanks Paul. You should get around 80 cm at 100%. I normally fly at 70cm/70% or 65cm/65%......keep it square. Up here in JHB you most likely will not be able to over-boost
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