C-421B Aux Fuel Pump Qest

[conquest]

Anybody know about how long you keep the aux fuel pump on after t.o. I'M being taught to keep in on all the time. Any thoughts.

Thanks in Advance,

 

[Junior2]

conquest-

I have lots of time in the Golden Eagle....B model. Here is what I have always done. After takeoff (at safe altitude) aux pumps off. If I am flying in hot weather, or at "High Altitude"...above about 12,000 for that airplane...TURN THEM ON LOW. They engines will vapor lock in this airplane during flight.....BUT.....you have plenty of warning (eg. nervous fuel flow, surging power, engine quitting), and it is QUICKLY remedied by turning Aux pumps to low.

Flying freight, I was usually below 12,000...so I would prefer to leave them off as to save the pumps for when I might REALLY need them (by the way, I have had 2 aux fuel pump failures in this airplane as well in the 3 years that I have flown it). If it makes you feel better....when you use the aux tanks, cessna took the guess work out of it, and the aux boost pumps in the aux tanks will automatically turn on when selecting these tanks (I have had one of these pumps fail inflight as well).

It is fine to leave them on LOW, if you want, or if that is the company SOP's for that aircraft...but in closing, I turn them off.

 

[bbond]

You learned correctly. On all the time.

 

[f-5]

leave those rascal's on low all the time.....period...except for shutdown....then shut down one engine at a time.....never shut both engines down at the same time on a 400 series.

 

[Mason]

leave those rascal's on low all the time.....period...except for shutdown....then shut down one engine at a time.....never shut both engines down at the same time on a 400 series.

What is the reason for not shutting both down at the same time?

 

[Say Again Over]

leave those rascal's on low all the time.....period...except for shutdown....then shut down one engine at a time.....never shut both engines down at the same time on a 400 series

The airplane has a bit of a shudder when shutting both down at the same time, please explain though, haven't heard this before.

 

[dhc8fo]

I don't know what PP's reason is, but here is mine:

If you shut one down at a time, you can check that the shuttle valve for the vacuum pumps is working properly. Just alternate between which one you start first and which one you shut down first and check that the red thingy (technical term) pops out.

I follow the check list (which has you shut the aux pumps off after takeoff and before shutdown) but I really see no reason why you can't leave them on all the time. I know several operators that do. Flight Safety lets you do either.

 

[Mason]

That is the only reason that I can think of but the way it was worded seemed like the plane would blow up if you shut both down at the same time.

 

[CDogg]

I always flew with them on low - period. never seemed to have a problem.... but did turm them off for shutdown, made hot starts a bit easier it seemed, but maybe that was just a mental thing

 

[McLovin]

After start, keep them on LOW until shutdown even if you have done the fuel pump switches service bulletin, unless the low pressure fuel pumps fails, then go HIGH (hopefully you did the bulletin. Lots of crashes have happenned prior). Remember, if you are on high, adjust your mixture on landing or you'll flood the engines

As far as shutting one at the time, I was explained once by a cessna rep that shutting both engines at the same time creates too much airframe vibration that can lead in cracks. (not sure I believed him)

shutting one at the time definitely reduces vibration and keeps passengers happy!