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That is very interesting, Yvon.
My calculation shows that if you were turning 5000 rpm when manifold pressure was 30.5"Hg you would have been flowing approx 17.20 lbm of air per minute. If the pressure drops to 29.4" Hg (and all else the same) , you would now have to turn 5200 rpm to get the same air flow of 17.20 lbm/min, so there is indeed an 200 rpm difference to get the same air mass flow. Very interesting.
Thanks for sharing.
Ed
----- Original Message ----- From: "Yvon Cournoyer" <geryvon@videotron.ca>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, October 21, 2007 5:05 PM
Subject: [FlyRotary] ATMOSPHERIC PRESSURE & ENGINE HORSEPOWER AT GROUND LEVEL
Ed Anderson and others have mentionned at times that they observed power output variations at ground level and attributed the variations to variances in atmospheric pressures at ground level. Over the last few days, our area was subjected to very high atm press (approx. 30.5 in. hg.) followed by very low atm press. (approx. 29.4 in. hg.) At full power static runup, I noted 200 rpm less at low pressure. I regret that I did not note the temperature and relative humidity.
Max rpm noted 5000. Sorel Airport elevation is 76 ft. Yvon.
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