Pressure Altitude or Density Altitude

[john smith]

I am becoming confused by everything I am reading.
When I set cruise power, do I set the MP and RPM for the pressure
altitude I am cruising at?
Or do I set it for the calculated density altitude?
Or, does density altitude only affect mixture/leaning?
I know full throttle (MP) altitude is affected by temperature (density
altitude), which is what leads me to ask the question. What confuses me
is the POH refers to pressure altitude.

[john smith]

Scott Skylane wrote:
> john smith wrote:
>
>> I am becoming confused by everything I am reading.
>> When I set cruise power, do I set the MP and RPM for the pressure
>> altitude I am cruising at?
>> Or do I set it for the calculated density altitude?
>> Or, does density altitude only affect mixture/leaning?
>> I know full throttle (MP) altitude is affected by temperature (density
>> altitude), which is what leads me to ask the question. What confuses
>> me is the POH refers to pressure altitude.
>>
> John,
> Most flight manuals I have seen reference pressure altitude on one side
> of the power setting table, and then show applicable settings for
> various temperatures at those given altitudes. Thus, the table is doing
> the density calculation for you, all you need to know is pressure
> altitude and OAT (or induction air temp, if available).

(Sound of Dope Slap!)
That's two in the last 24 hours.
I sure hope my forehead doesn't get much flatter!

[Scott Skylane]

john smith wrote:
> I am becoming confused by everything I am reading.
> When I set cruise power, do I set the MP and RPM for the pressure
> altitude I am cruising at?
> Or do I set it for the calculated density altitude?
> Or, does density altitude only affect mixture/leaning?
> I know full throttle (MP) altitude is affected by temperature (density
> altitude), which is what leads me to ask the question. What confuses me
> is the POH refers to pressure altitude.
>
John,

Most flight manuals I have seen reference pressure altitude on one side
of the power setting table, and then show applicable settings for
various temperatures at those given altitudes. Thus, the table is doing
the density calculation for you, all you need to know is pressure
altitude and OAT (or induction air temp, if available).

Happy Flying!
Scott Skylane

[Thomas Borchert]

John,

> What confuses me
> is the POH refers to pressure altitude.
>

If it does, use that. Our POH shows tables for pressure altitude and
correction factors for temperature, i.e. +/- 0.5 in. MP for every +/-
10 degrees Celsius difference from standard temperature for that
altitude.

--
Thomas Borchert (EDDH)