"Morgans" wrote in message
...

"Bob F." wrote

Here's a question ...
When a normally aspirated engine quits while at cruise, how does the MAP
react with respect to the throttle?
Does it indicate zero?
Does it indicate barometric pressure?
Does it pin? (Go to max)?
Does it follow the Throttle (high MAP with a high throttle setting , low
when set to low throttle setting)?

From a theoretical point of view, I vote for the last choice. Why?

I would think because, if the prop is still turning, the engine is still
an air pump, just as much so as if it were still running. The "suck" part
of the suck, squeeze, bang and blow is still there. If the throttle is
closed, the throttle butterfly is closed so the suck is trying to pull a
partial vacuum.

I would think that because the engine is turning more slowly, the ability
to pull as low of a MAP will be lessened, (higher MAP-just to clarify)
than the pressure you would normally see at the same throttle setting with
the engine running.
--
Jim in NC

Correct, at least your first paragraph. With respect, I don't understand
your second paragraph without reading into it.

I ask this Q. because I often ask a student to tell me how to recognize and
engine fuel starvation. I often get the incorrect answer that the MAP goes
to zero.

Years ago, before best practices frowned upon this, you could set up a glide
at about 400 fpm down, 80 kts, and 2200 RPM, pull the mixture and you would
not hear or feel any engine loss. And if you pushed the throttle in, MAP
would increase, just like when it's running ok. So this is not a good
indication of engine fuel starvation.
You could set up the same scenario on a ME and find the right speeds and
settings to demo this.
--
Regards, Bob F.