Aux. Fuel Pump Question

[BYUFlyr]

Does anyone see anything wrong with leaving the fuel pumps "on" in the pattern when performing touch and goes on a Piper Seneca? Does it affect the aircraft's performance? Fuel mixture?

I think it's a safe practice and I see no drawbacks with leaving them on. Turning them off at 500 AGL just to turn them back on 30 seconds later seems like an unnecessary addition to the workload and increases the chances of inadvertently landing with your back-up fuel pumps "off".

I had a discussion about this with my MEI and I didn't feel like he gave me a good reason to turn them "off" when we're staying in the pattern. The POH does not say that you have to turn them off at 500 AGL. It states that you MAY turn them off above 500 AGL.

We also had the same discussion about cowl flaps in the pattern (leaving them open). Can someone more experienced than me shed some light on this?

 

[Kream926]

fuel flow maybe?

 

[minitour]

I'd go with the POH...check out the Amplified procedures sections and see if it recommends...for example, the 172RG POH specifies leaving the gear down in the pattern. I discussed this with an examiner and after one "gear up" and "gear down" he said I could leave them down...

When in doubt, the POH is set up by the manufacturer...go by that.

I know that doesn't really help, but that's all I got...

-mini

 

[hawg2hawk]

If any A&P's weigh in on this, I'm sure they will tell you it is to increase the service life of the aux fuel pump. It's like the landing light -- it would be safer to leave it on all the time, but then you'd spend a lot replacing landing lights. In many larger aircraft, boost pumps, while not technically the same, are left on at all times during flight.

Remember an aux pump is a backup to provide fuel under positive pressure in case the engine driven fuel pump fails. Having the aux fuel pumps on or off won't affect fuel flow -- that's the function of the fuel control via the mixture and throttle settings.

I'll let someone else cover cowl flaps. I don't feel up to the inevitable argument.

 

[minitour]

I'll let someone else cover cowl flaps. I don't feel up to the inevitable argument.

I'll try ---

Leave 'em open...on the climbout you wont overheat and you probably won't shock cool 'em either...one less thing to worry about should some numbnutz taxi onto the runway when you're on short final...

-mini

*edit*
But again...if the POH says close 'em and open 'em when appropriate...do it

 

[Kream926]

I discussed this with an examiner and after one "gear up" and "gear down" he said I could leave them down...
-mini

really, WTF!!?!?!
mine made me do up and down every time

 

[minitour]

really, WTF!!?!?!
mine made me do up and down every time

yeah well...mine also wouldn't let me use rudder during the maneuvers...so take it for what its worth...

Luckily though we went out and did the maneuvers first so that was the "gear up" and on base was the "gear down" for the first touch and go...didn't touch it the rest of the time...

He either didn't care, didn't know about the POH saying that, or was impressed that I knew and just went with it...I'm thinking it was a "didn't care"

-mini

 

[hawg2hawk]

yeah well...mine also wouldn't let me use rudder during the maneuvers...so take it for what its worth...

Luckily though we went out and did the maneuvers first so that was the "gear up" and on base was the "gear down" for the first touch and go...didn't touch it the rest of the time...

He either didn't care, didn't know about the POH saying that, or was impressed that I knew and just went with it...I'm thinking it was a "didn't care"

-mini

Maybe not. I've ridden with countless instructors and check pilots in a bunch of different airplanes, and every time I see something like this, the reason offered is "so we don't wear out the gear/aux pump/landing light" etc.
Sometimes valid, sometimes not, but hopefully the IP knows AND cares!

 

[minitour]

...hopefully the IP knows AND cares!

word to that!

 

[JB74]

If any A&P's weigh in on this, I'm sure they will tell you it is to increase the service life of the aux fuel pump.

I am not an A&P but I would also guess that is why. Does anyone know how often the aux pump operation is verified? Annual? I would guess that an inop aux pump could go undetected for quite some time if the plane got 100% of its fuel from the engine driven pump.