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#1
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Vacuum pump power source?
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 |
#2
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Vacuum pump power source?
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. |
#3
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Vacuum pump power source?
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 |
#4
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Vacuum pump power source?
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 |
#5
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Vacuum pump power source?
"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. :~) |
#6
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Vacuum pump power source?
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 |
#7
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Vacuum pump power source?
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 |
#8
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Vacuum pump power source?
"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. |
#9
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Vacuum pump power source?
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 |
#10
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Vacuum pump power source?
"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! |
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