Setting altimeters with no radio

Doug wrote:
No one has mentioned using the manifold pressure guage as an altimeter.


Because you can't do it in the air, unless you stop the engine first.

No one has mentioned using the manifold pressure guage as an altimeter.
Because you can't do it in the air, unless you stop the engine first.

Well, you can, sort of, but it probably won't help much. At full
throttle, the manifold pressure will max out at a value that has the
same relationship to altitude as an altimeter. I vaguely recall it's
something like an inch loss per thousand feet high.

Jose
--
"Never trust anything that can think for itself, if you can't see where
it keeps its brain." (chapter 10 of book 3 - Harry Potter).
for Email, make the obvious change in the address.

On a normally aspirated engine, the MAP will be about 1 inch
per thousand feet from 29.92 plus about 1.5 inches for
induction losses on a running engine. So if the maximum
observed MAP is 23 inches, you are at about 5,500 feet
pressure altitude [give or take a thousand feet.
Turbocharged engines make such a check impractical.



"Jose" wrote in message
news | No one has mentioned using the manifold pressure guage
as an altimeter.
| Because you can't do it in the air, unless you stop the
engine first.
|
| Well, you can, sort of, but it probably won't help much.
At full
| throttle, the manifold pressure will max out at a value
that has the
| same relationship to altitude as an altimeter. I vaguely
recall it's
| something like an inch loss per thousand feet high.
|
| Jose
| --
| "Never trust anything that can think for itself, if you
can't see where
| it keeps its brain." (chapter 10 of book 3 - Harry
Potter).
| for Email, make the obvious change in the address.