Fuel Pump Off?

[squeakmail]

I just want to play a game of "Devils Advocate"...whatever your answer (even if I agree with you) there is an argument available.

Anyway...student asked me recently...

"Why bother turning off the fuel pump when climbing through 1,000 feet. If one of the immediate actions during an engine failure (PFL) is to turn it back on again and wait for it to do it's stuff...why not leave it turned on for the entire flight?"

Answers on a postcard.

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LIVE in peace...or REST in it!

[Wee Weasley Welshman]

You want to know if the engine pump ever fails. If you have both on then you are 'hanging on one' without ever knowing it. No backup when the inevitable happens. Besides the electric pump design wears more quickly than the engine pump design.

WWW

[climbs like a dog]

Not forgetting too that it is an unneccessary service drawn from the electrical supply.

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0 to 2000ft in 10 minutes

[Wee Weasley Welshman]

And the higher internal pressure at altitude may cause leaks to occur in the fuel lines etc.

WWW

[Wee Weasley Welshman]

What I really want to know is where the fuel comes from when on a PA38 you put the fuel selector to the upright position i.e inbetween left and right tanks. The engines always run. A secret belly tank not covered by the pilots handbook...? I think we should be told!

WWW

[Airprox]

When the fuel knob is in the 12 o'clock isn't that feeding from both tanks??

[WileyP]

Gotta agree with WWW (as usual!) about shutting the pump off when safety and flight conditions dictate. To add emphasis, here's a quote from Textron Lycoming's operating tips:

''An effective continuous fuel supply is provided by use of the fuel boost pump. As a general recommendation, the fuel boost pump should be used with Lycoming engines in all conditions where there is any possibility of excessive vapor formation, or when a temporary cessation of fuel flow would introduce undesirable hazards.

''The conditions under which Textron Lycoming recommends operation of the fuel boost pump are as follows:

1. Every takeoff.

2. Climb after takeoff unless Pilot’s Operating Handbook says it is not necessary.

3. When switching fuel selectors from one separate fuel tank to another, the fuel boost pump should be "On" in the new tank until the operator is assured there will be no interruption of the fuel flow.

4. Every landing approach.

5. Any time the fuel pressure is fluctuating and the engine is affected by the fluctuation.

6. Hot weather, hot engine ground operation where fuel vapor problems cause erratic engine operation

7. Some General Aviation aircraft require the use of the fuel boost pump during high-altitude flight. This will be spelled out in the Pilot’s Operating Handbook.

8. If the engine mounted fuel pump fails.

''If the fuel boost pump is used during ground operation, don’t fail to check the condition of the engine mounted fuel pump before takeoff by turning the boost pump off briefly, and then back "on" for takeoff. If the engine mounted pump has failed, it would be safer to know that on the ground rather than in the air when the fuel boost pump is turned "off."

When in doubt, do the safest thing and use the fuel boost pump with Lycoming engines. Don’t be "stingy" with the boost pump. In most cases they last the overhaul life of the engine, and are then exchanged or overhauled themselves. AS A REMINDER, the airframe Pilot’s Operating Handbook is the authority if boost pump information is spelled out in it."

Each pilot, and certainly each flight instructor should be well versed in the manufacturer's instructions and recommendations. That means not only the airframe manufacturer, but the powerplant manufacturer as well.

...and above all,

FLY SAFE!

WileyP

[Capt Homesick]

I had a loss of fuel pressure once- the EDP had worked fine on the ground, but when we climbed through 1000' and switched the electric pump off, the fuel pressure did its normal drop, then kept dropping below the green arc. As it was, we turned the electric back on, turned back and landed. If we hadn't turned the booster off we would never have known- not only a problem for us, but for everyone else to take the a/c afterwards. Maybe it would never have been a problem- until the electric pump was nearly at the end of it life, and engineering said "it'll be ok for just one more flight..."

[Tinstaafl]

Boost pump use with Continental injected engines is usually different.

Try switching the electric pump on with the EDP and you will often experience a rich cut. Varies with the exact engine / pump / installation & power setting etc. Also if there are high & low press. settings eg IO-520 variants used in C206/207/210/310/400 series and Baron/Bonanzas.

Seneca's with the Continental IO-360 are similar but the single flow rate pump is there as a replacement for the EDP in case of failure and also for purging. The Catch is that it can only supply sufficient fuel flow for about 75% of max power. Don't think I'd be too impressed if I had an engine failure + the live engine EDP fail!