Vacuum pump power source?

[Terence Wilson]

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

[John Godwin[_2_]]

Terence Wilson > wrote in
:

> So I guess most aircraft use an electrical pump that can be
> driven by the alternator or battery, is this the case?
>

This is why they teach partial panel.

[tscottme]

In small "general aviation" type aircraft commonly built for decades, the
vacuum pump is engine driven through a mount on the engine. This vacuum
pumo typically drives the attitude indicator and directional gyro. Another
instrument called turn coordinator is typically a self-contained,
electrically-driven gyro. If the engine-driven vacuum pump fails pilots
learn how to fly with reference to the turn coordinator, compas, airspeed
indicators.

There is a section of the vacuump pump shaft that is designed to fail should
the vanes of the pump, or some other cause, cause the pump to seize. This
can protect the rest of the pump and/or prevent damage to the engine
accessory drive gears.

Owners/pilots that foresee a lot of flying by reference to instruments will
sometimes install an electrically-driven attitude indicator as a redundant
instrument to the vacuum driven indicator. There are devices some
owners/pilots install which can be used in an emergency which will tap into
the vacuum in the intake manifold of the engine and provide instrument
vacuum power.

--

Scott

"a community that allows a large number of young men to grow up in broken
homes, dominated by women, never acquiring any stable relationship to male
authority, never acquiring any rational expectation about the future - that
community asks for and gets chaos."
Daniel Patrick Moynihan


"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

[Mortimer Schnerd, RN[_2_]]

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?


Somebody else has already explained the frailities of the vacuum system. So why
do we use it? Redundancy. If the electrical system takes a dump, you've still
got primary instruments along with the attitude indicator and directional
gyro... you've lost the lights, radios, and the turn coordinator. But you're
still able to keep the shiny side up without too much sweat.

If the vacuum system craps out, you've lost the attitude indicator and the
directional gyro. But you've still got the primary instruments to keep things
upright.

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.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com

[Matt Barrow[_4_]]

"Mortimer Schnerd, RN" <mschnerdatcarolina.rr.com> wrote in message
...

>
> Somebody else has already explained the frailities of the vacuum system.
> So why do we use it? Redundancy. If the electrical system takes a dump,
> you've still got primary instruments along with the attitude indicator and
> directional gyro... you've lost the lights, radios, and the turn
> coordinator. But you're still able to keep the shiny side up without too
> much sweat.
>
> If the vacuum system craps out, you've lost the attitude indicator and the
> directional gyro. But you've still got the primary instruments to keep
> things upright.
>
> 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".

One nice little gadget is an AH that has a battery backup completely
isolated from the standard electrical system.

Better yet is dual electrical systems that run off independant and isolated
electical buses.

Better still, is the above that runs of an AHRS, that has a MTBF of 30,000
hours as opposed to the vacuum system that typically has a MTBF of 28
minutes. :~)

[Mortimer Schnerd, RN[_2_]]

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.

Of course, that means almost 2700 hours where nothing broke.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com

[Jim Macklin]

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

[Matt Barrow[_4_]]

"Mortimer Schnerd, RN" <mschnerdatcarolina.rr.com> wrote in message
...
> 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.

How did you lose the AI?

>
> Of course, that means almost 2700 hours where nothing broke.
>

Like the adage, "...hours of 'boredom' followed by minutes of stark terror".

Note, that losing the vac pump and the AI would have been of little
consequence with an AI with battery backup. My old bird had a EAI with
battary and the vac AI was my secondary. Also, dual alternators is becoming
the norm in the new generation aircraft.

[john hawkins]

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
>
>

[Matt Barrow[_4_]]

"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.

And maybe a new, electronic buggy whip!

[Robert M. Gary]

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

[Robert M. Gary]

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

[Ronnie]

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
>>
>>
>
>

[Bill]

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