Vacuum pump power source?

On Sep 10, 8:22 pm, Terence Wilson wrote:
Hello,

I was wondering how the primary vacuum is powered in a single engined
aircraft. If it was powered directly by the engine, a engine failure
would result in the immediate loss of attitude indicator and heading
indicator.

Not true unless the engine siezes. An idling engine will power the
instruments.

-Robert

On Sep 11, 8:11 am, "Mortimer Schnerd, RN" mschnerdatcarolina.rr.com
wrote:
Matt Barrow wrote:
The chances of both systems failing on the same flight are much less than
any one system... and even there failure is an uncommon event. But as
others have noted, you can add redundant instruments and even backup
sources.

Of course, the vacuum system is, IIRC, about 5-10 times more likely to "take
a dump".

While that may be, I've lost an attitude indicator once, a vacuum pump once, an
alternator once and a fan belt once. A limited history but it's running 50/50
in my book.

And a backup vac pump would only fix one of those items, while a back
up electric attitude indicator would address two.

-robert

Besides icing, once other limitation of the venturi power source
is how to sping the gyros up before takeoff. Seems to limit the
weather you would be able to launch into. I would not launch
into low IFR with venturi powered gyros.

Just my 2 cents.

Ronnie

"john hawkins" wrote in message
. net...
What ever happened to the god old venturi. Sure they could ice up Hasn't
anyone come up with a heated venturi (other than placing it the exhaust
streram)?
I got my rating in an old cessan that ran off venturi. two big fog horn
off the left side Bjut they worked.

"Jim Macklin" wrote in message
...
Most systems use a pump attached to the engine, which will
provide suction/pressure as long as the engine is turning.
Those pumps fail, their life is short and can be shorter if
abused during engine maintenance.
There are stand-by electric pumps and even engine manifold
sources are used in some installations. Many airplanes are
all electric [the new G1000's come to mind] and they have
redundant battery busses, generators and some also include
air driven gyros.


"Terence Wilson" wrote in message
...
| Hello,
|
| I was wondering how the primary vacuum is powered in a
single engined
| aircraft. If it was powered directly by the engine, a
engine failure
| would result in the immediate loss of attitude indicator
and heading
| indicator. So I guess most aircraft use an electrical pump
that can be
| driven by the alternator or battery, is this the case?
|
| Thanks in advance,
|
| Terence

If the engine fails, contact with the earth won't be far behind.
Unless the aircraft is really high, the gyros will still be running
and reasonably erect upon
contact if they are in good conditon. They don't suddenly
tumble. The usual spec is 7 minutes for rundown.

As others point out, a failure of the pump is more likely
and there are several solutons.

Bill Hale



On Sep 10, 9:22 pm, Terence Wilson wrote:
Hello,

I was wondering how the primary vacuum is powered in a single engined
aircraft. If it was powered directly by the engine, a engine failure
would result in the immediate loss of attitude indicator and heading
indicator. So I guess most aircraft use an electrical pump that can be
driven by the alternator or battery, is this the case?

Thanks in advance,

Terence