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

All dyno runs, must be corrected to sea level standard day, so that there will be some usable data day to day to account for temperature, humidity, and barometric pressure. Actual HP goes up and down with changes in all of these factors. Raw torque numbers are meaningless until corrected as above.

 

Like the RPM drop when you check the carb heat. And the reason you lean the mixture as you climb.

 

On a Southwest 737 we landed at the old Denver, and before we pushed back with full fuel and seats, the ticket agent got on the PA and asked for 6 people to volunteer to get off and catch the next plane, because now the plane was too heavy to legally leave Denver. Because it was 102 degrees outside.

 

The wife and I held out for a round trip each to anywhere in the system. On the way off the plane, we were handed a magnum of champagne. We went to the ticket counter, then to the very next gate, and got on a plane that was a nonstop to Columbus Ohio. There were 12 people on that plane. The plane we got off of landed in Chicago and got stuck there for three hours in thunder storms. 

 

Life is good.

 

Lynn E. Hanover