What happens if you lose both fuel pumps?

mandm

mandm

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In a low wing airplane, what happens if you lose both fuel pumps, would the engine quit almost right away? Or would fuel possibly still flow through the system?
 
If you lose both, my guess is you lose the engine. No gravity and I doubt enough pressure/suction.
 
Depends on the design. My low wing experimental has no fuel pump to fail ...
 
Fuel injected it'll quit right away. Carbureted it will run on the fuel in the bowl for maybe.... 15 seconds? After that it depends on the fuel system. If the fuel level is above the float bowl of the carb, it might get enough gravity flow to stay running, more likely just enough to cough and sputter its way to the crash site.
 
A few long wing airplanes (like Ercoupes) have a gravity fed header tank. The fuel pump just transfers fuel from the mains to the header, so if you lose the pump your engine will keep running until the header is dry.
 
The chance of losing both in flight has an exceedingly small probability.
Everyone knows the symptoms of losing one, or the other in flight.

More often, the electric pump failure is discovered on the next startup.
I have also had a mechanical pump fail on the ground.
 
You get the opportunity to log glider PIC time.
 
Half Fast said:
In the unlikely event this happens, the pilot simply rolls inverted to maintain fuel flow.

Surviving the subsequent wheels-up landing is the difficult part....
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It's been done, in the movie Flight, on an airliner.
 
I have 1st hand knowledge of a PA-28 caught on top IFR with an alternator failure. Battery totally died. Engine kept running OK and ended with a safe landing. On the other hand, I am familiar with the Bell Jet Ranger. It has an engine driven fuel pump plus two electric boost pumps in the fuel tank. Flight manual states that "If one or both boost pumps, inop, reduce fuel endurance to 45 minutes." Bell isn't kidding.
 
schmookeeg said:
That insidious twins vs singles debate is everywhere :D
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I was mastering the Barron and my CFI told me of a Barron incident in Maine. In dead of winter.
Pilot did a poor job of draining ALL sumps and took off on the mains. He then switched to Aux tanks. There was a slug of water in each tank and it froze halfway to the engines. Both quit. He was able to dead stick back to his departure field.
 
Maxnr said:
I was mastering the Barron and my CFI told me of a Barron incident in Maine. In dead of winter.
Pilot did a poor job of draining ALL sumps and took off on the mains. He then switched to Aux tanks. There was a slug of water in each tank and it froze halfway to the engines. Both quit. He was able to dead stick back to his departure field.
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Yikes! If I'm flying something with that many tanks, I'm switching them a few minutes apart from each other.
 
kaiser said:
Yikes! If I'm flying something with that many tanks, I'm switching them a few minutes apart from each other.
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My CFI's teaching point was, whenever possible, to switch tanks when over an airport.
I also recall a whole lot of drains on the Barron.
 
Carburetors on gravity-feed systems have larger float bowl valves to permit adequate fuel flow at the tiny pressure generated by the fuel head. Pumped systems use carbs with smaller valve to prevent system pressure from forcing the valve open and flooding the engine.

Boost pumps have a manufacturer-recommended life limit. Ten years or so. There are components in them that deteriorate with age.
 
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Lots of planes with fuselage tank and low wing.
 
kaiser said:
If you lose both, my guess is you lose the engine. No gravity and I doubt enough pressure/suction.
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Unless you're Denzel. Then you just fly inverted in an emergency and gravity is no longer a problem.
 
Maxnr said:
I have 1st hand knowledge of a PA-28 caught on top IFR with an alternator failure. Battery totally died. Engine kept running OK and ended with a safe landing. On the other hand, I am familiar with the Bell Jet Ranger. It has an engine driven fuel pump plus two electric boost pumps in the fuel tank. Flight manual states that "If one or both boost pumps, inop, reduce fuel endurance to 45 minutes." Bell isn't kidding.
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Why would you have expected the engine to not run ok in that situation?
 
Jeff767 said:
Why would you have expected the engine to not run ok in that situation?
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This Is in answer to Mandm's question: "If you lose both pumps in a low wing, would the engine still run?" I cite an example in answer, when a low wing airplane lost both pumps and continued to run. In that case, loss of the pumps would be secondary to loss of com, nav, fuel gauge, turn coordinator and ext lights.
Though I was not on board the incident A/C, I was acutely aware that this was a major problem for that pilot because of the IMC conditions. Widespread low IMC over the area. Turned out OK.
 
In an old Bonanza, if the engine driven fuel pump quits, and the electric backup quits, you can use the wobble pump to fly to the crash site.
 
Maxnr said:
This Is in answer to Mandm's question: "If you lose both pumps in a low wing, would the engine still run?" I cite an example in answer, when a low wing airplane lost both pumps and continued to run. In that case, loss of the pumps would be secondary to loss of com, nav, fuel gauge, turn coordinator and ext lights.
Though I was not on board the incident A/C, I was acutely aware that this was a major problem for that pilot because of the IMC conditions. Widespread low IMC over the area. Turned out OK.
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you said that plane lost its alternator and subsequently the battery. Not that it lost both pumps. How did it lose both pumps, one of which is mechanical?
 
Gravity isn't going to keep the fuel flowing in a low-wing airplane that uses wing tanks. It just ain't. Nor is the suction in the carb's venturi. That's one reason why there's a boost pump in the system.
 
Maxnr said:
This Is in answer to Mandm's question: "If you lose both pumps in a low wing, would the engine still run?" I cite an example in answer, when a low wing airplane lost both pumps and continued to run. In that case, loss of the pumps would be secondary to loss of com, nav, fuel gauge, turn coordinator and ext lights.
Though I was not on board the incident A/C, I was acutely aware that this was a major problem for that pilot because of the IMC conditions. Widespread low IMC over the area. Turned out OK.
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Still confused. There is no reason the engine should not have run normally. The electric pump is a backup to the mechanical pump and not normally used. The mechanical pump is extremely reliable.
 
Jeff767 said:
Still confused. There is no reason the engine should not have run normally. The electric pump is a backup to the mechanical pump and not normally used. The mechanical pump is extremely reliable.
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He said, "I cite an example in answer, when a low wing airplane lost both pumps and continued to run."

In what universe would that be? Or did it have a big header tank up high in the fuselage? Or in-tank pumps in addition to the booster and engine pump? Not in a light airplane. "Both pumps" means both the engine-driven pump and the booster.

The manufacturers don't install engine and fuel stuff that isn't necessary to safe flight. It costs money and adds weight and failure points. So if it's there, it's necessary.
 
I was replying to the post that stated the aircraft had a total electrical failure and the engine continued to run. In that situation it should continue to run.
 
Jeff767 said:
I was replying to the post that stated the aircraft had a total electrical failure and the engine continued to run. In that situation it should continue to run.
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LOL! I once had a student who was absolutely certain the engine would quit with no electrical power - he saw it as an electric fan. I needed to switch the Master off in flight to convince him otherwise. He made a little jump in his seat when I did that.
 
midlifeflyer said:
LOL! I once had a student who was absolutely certain the engine would quit with no electrical power - he saw it as an electric fan.
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Once had a student wondering about that skinny little V-belt in there that made the propeller turn. He thought the alternator was a motor.
 
..hypothetical, would you be able to use the primer in a carb'd low wing plane like a PA-28 to squirt fuel in?
 
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