208B Leaving the Fuel Boost on and Battery......

[ClevelandSteamer]

Why must we leave it on until the Fuel Boost pump Annunciator flashes? Maybe this is just a few companies I see doing it or not I dunno. But, We are asked to do it. Some people say it is to fill the EPA can with the residual fuel inside, some say it is to fill the pressure in the lines when you put the condition leaver to idle cut off.

Im new on the Caravan and I would like to know the real answer. I get a whole lot of answers from each pilot.

Also, On the G1000....since there is no Annunciator panel, how do you know when to turn it off? Wait s few more seconds? You wouldnt leave the AV1 AV2 on until you got a CAS message I would assume.

Cheers!

[longjon]

Have you looked at the fuel system schematic in the maintenance manual?

[Bulawrench]

There is a difference between the POH and Pratt maintenance manual on this. If you keep pressure to the engine down to 5 % ng you are better off. I prefer not to have the switch in normal but "on" so it doesn't cycle.

[black hole]

To Lubricate the engine fuel pump!!!!?? And we all like healthy fuel pumps?
BH

[Bulawrench]

something like 12 hours without an airframe pump comes to mind. Do you have the boost pump on when you do engine washes?

[ClevelandSteamer]

Thanks for the word on the lights you guys. In regards to the boost pump on during washes, I don't think so, how often do they need to be done?? Im sure our company doesn't do them enough, were are right n the coast of the indian ocean. Lots of salt water residue I am sure. Not a float operator though.

Can you explain a little bit more about the boost being left on until 5%Ng?? for pressure? I appreciate it, thank you.

Cheers,

[Bulawrench]

I have been around turbo beavers for too many years and they recommend leaving the boost pumps on to keep pressure to the engine. This always keeps the engine pump happy with fuel as it is lubricated by fuel.
We do engine compressor washes at the end of every day and power recovery washes every 200 hours as the maintenance schedule states. Spinning the engine several times in this type of wash without the boost pumps may cause damage but i haven't proven this speculation yet. We are on the coast and aircraft are on floats.
Cheers

[longjon]

edit

[2R]

Good question .Some nice answers
It is always "nice to be nice"

No such thing as a dumb question ,only dumb answers or in some cases rude answers.
I would rather ask a dumb question than live in ignorance.
If you are going to take the time to type an answer how hard would it be to share "the Knowledge"and answer the question in a nice manner sharing your wisdom with those who seek it.


I have to wait until the lakes freeze over before i can walk on the water

[ClevelandSteamer]

Your right 2R I guess they can get rid of this Maintenance forum too if people are going to be so ignorant. What good is it anyways right?

The forum for the know it alls are on Pprune maybe?? I just handed in my two weeks, i'm going to cut my wrists instead of fly the C208B.

Anyways, I cant know everything, I think its a lot better then being, "Pilot A Type" that knows everything and doesn't ask question.

Cheers,

[Spinner]

don't stop asking questions at least some of us don't mind offering a reason. I am sorry that it hurts some peoples feelings to offer answers.

[brownbear]

5% ng when you can shut off boost is definitely for lubrication on the engine driven HP pump. Otherwise the pump can cavitate.

Anytime the engine is spooled the boost pumps need to be on, either for start up or comp washes.

Comp washes in salt environments are good to do daily. They are not done like soap washes.

crank with ignition off and boost pumps on, till you are above 10%ng. Put a garden hose of clean water with minerals in it....(needs to be soft) and continue adding water for 10-14 seconds. Remove the water and the operator then clears the engine while cranking. Observe starter limitations of course. And also follow P&WC maintenance manual too.

There are all kinds of guides on the water being introduced and at certain PSIs. On most of the float planes I worked on we just used a garden hose.

Remember after the water drains, about 5 minutes to start the engine to clear the water. Other wise things may rust out inside.....