N4655R
Senior Member
Ok, so I am having a brain fart at the moment....
When calculating density altitude with the attached chart, for flight planning, is the altitude on the left calculated whilst in the air or is the density altitude used at the airport. For example, today the density altitude at KROA is 3453' - The field elevation is 1175'. So, if my flight is planned at 4500', do I then add the difference from the density altitude from the field altitude to my planned altitude to determine the RPM setting in cruise (3453-1175=2278 Then 2278+4500=6778')? RPM Cruise setting at 2575RPM at 75%.
Or just use the density altitude (3453') for the cruise RPM setting? RPM Cruise setting at 2475RPM at 75%
Or just add the 3453' to the planned altitude. 4500+3453=7953' for 2600RPM at 75% Power.
PA28-140
When calculating density altitude with the attached chart, for flight planning, is the altitude on the left calculated whilst in the air or is the density altitude used at the airport. For example, today the density altitude at KROA is 3453' - The field elevation is 1175'. So, if my flight is planned at 4500', do I then add the difference from the density altitude from the field altitude to my planned altitude to determine the RPM setting in cruise (3453-1175=2278 Then 2278+4500=6778')? RPM Cruise setting at 2575RPM at 75%.
Or just use the density altitude (3453') for the cruise RPM setting? RPM Cruise setting at 2475RPM at 75%
Or just add the 3453' to the planned altitude. 4500+3453=7953' for 2600RPM at 75% Power.
PA28-140
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