Fuel pump switches

[StewartH 66]

I'm curious why there are two "on" positions for the fuel pump switches in the Cheyenne II, one "1" and the other "2"?  When does one use "1" and when "2"?  Both positions work, obviously...

Stew

[whamil77 183]

The engine driven pumps aren't designed to draw fuel from the tanks, but only to pressurize the fuel nozzles. The boost pumps provide pressurized fuel to the engine driven pumps.  There are two for each engine for redundancy.  If one fails, the other is available.  Some operators use #1 on odd days and #2 on even days.  Some use one to failure and keep the second in reserve, while checking operation of the second occasionally.     

[StewartH 66]

Thank you, Bill.  I appreciate your insights into the Cheyenne.