Manifold Pressure at Rest

Did I misunderstand my reading on the subject, or should the Manifold
Pressure on an engine that's off be the local atmospheric pressure?

I've just noticed that this is not the case in my little R182.

- Andrew

Should be the same value if the engine is not operating and the gauge is
correctly calibrated. I would suspect the gauge is out of calibration.

Dave

Andrew Gideon wrote:
Did I misunderstand my reading on the subject, or should the Manifold
Pressure on an engine that's off be the local atmospheric pressure?

I've just noticed that this is not the case in my little R182.

- Andrew

Let me amend my answer to be "same value if the engine is not operating,
the gague is correctly calibrated and you are AT SEA LEVEL".

Remember that local altimeter settings are corrected for sea level when
you are at a locale that is at elevation. 29.92" setting in Denver is a
"corrected reading" for what the pressure would be if you were at sea
level. So, ballpark.. the value is 1" per thousand (without digging out
reference material) pressure change/altitude. Denver on a standard day
(setting 29.92") should have a manifold pressure gauge reading (5000
ft/5" less) just under 25" when the engine is off.

Sorry for my initial error.
I'm sure if there are others, they will be quickly pointed out.
Dave

Dave S wrote:

Should be the same value if the engine is not operating and the gauge is
correctly calibrated. I would suspect the gauge is out of calibration.

Dave

Andrew Gideon wrote:

Did I misunderstand my reading on the subject, or should the Manifold
Pressure on an engine that's off be the local atmospheric pressure?

I've just noticed that this is not the case in my little R182.

- Andrew

Where are you?

"Andrew Gideon" wrote in message
online.com...
Did I misunderstand my reading on the subject, or should the Manifold
Pressure on an engine that's off be the local atmospheric pressure?

I've just noticed that this is not the case in my little R182.

- Andrew

John Gaquin wrote:

Where are you?

I assume you're answered by: Less than 200' above sea level.

- Andrew

at less than 200ft MSL, then the MP indicator with the engine at rest (and
sitting on the ground) should read the approximate value of the barometric
pressure or about 30in

Out here (2200MSL) the MP indicator would read about 2 inches or more lower
or about 28in (or closer to 27.5in) MP before engine start

BT

"Andrew Gideon" wrote in message
online.com...
John Gaquin wrote:

Where are you?

I assume you're answered by: Less than 200' above sea level.

- Andrew

Andrew,

I've just noticed that this is not the case in my little R182.


Should be. Otherwise, your MP gauge might need repair. Ours is
indicating about 0.5 inches too much, so we correct our settings for
that.

--
Thomas Borchert (EDDH)

Andrew Gideon wrote in message gonline.com...
Did I misunderstand my reading on the subject, or should the Manifold
Pressure on an engine that's off be the local atmospheric pressure?

I've just noticed that this is not the case in my little R182.

It should be the same as ambient pressure, but not necessarily the
same a altimeter setting. Altimeter setting is not pressue but some
made up number that makes the altimeter read correctly (that's
actually the definition!).

-Robert

Robert,

it should read the same pressure as the altimeter in the Kollsmann
window when the altimeter is set to zero feet, right?

--
Thomas Borchert (EDDH)

On Wed, 18 Aug 2004 17:57:19 +0200, Thomas Borchert
wrote:

Robert,

it should read the same pressure as the altimeter in the Kollsmann
window when the altimeter is set to zero feet, right?

......altimeter set to ***airfield elevation***, correct??
The old QFE vs QNH settings thing...
GNP, Socata TB-9 SX-ADE, LGTG, Greece, (grounded due to Olympics in
progress, next flight 29 September)