fuel pumps on/off?

[tuj]

Hi all:

I recently have had a couple of flights in a very small plane (8 seats, including pilot and empty seat next to him/her). Not sure the make, but there are overhead switches for the fuel pumps. I was watching the pilot fly as I was in the 2nd row, and during takeoff and landing, both pilots engaged the fuel pumps. However they left them disengaged during flight.

Can anyone explain to me (an engineer) why this is? Does the engine gravity feed?

[Tom!]

Might have been fuel boost pumps for starting and use during critical phases of flight, in addition to the normal engine driven pump

[OhNoCB]

Sounds possibly like a Chieftain.

Emergency fuel pumps switched on or off in the overhead switch panel which are used if you have a pump failure and also used for takeoff and landing. When everything is working normally you will have engine driven fuel pumps and boost pumps for the fuel, the emergency ones tend only to be switched on as a contingency.

[Radix]

.............

[Capot]

T T B F F.....ah yes, Fuel Pump(s) on.......

As I recall, simply to reduce the risk of fuel starvation during the take-off and initial climb.

[Dont Hang Up]

Electrical and mechanical pumps offer redundancy in the critical phases of flight.

Then why not use both all the time you may ask?

Well then there is the risk that the failure of one can be masked by the other. In the cruise is the best time to find such things out, with your normal scan hopefully identifying any unexpected decline on the fuel pressure gauge. And also "electrical fuel pump on" is usually quite high up on your engine-failure checklist