Fuel Pump - why turn off at low altitude?

[Romeo Juliet Whiskey]

Why do I see so many youtube videos of pilots turning off the fuel pump after takeoff at 300-400ft? If this is the only thing supplying fuel to the engine in case of an engine driven pump failure, it seems like the worse time to be turning the pump off. Why not at a much higher altitude, top of climb for example in small GA planes? What do you guys do?

 

 

[Roscoe]

Why do I see so many youtube videos of pilots turning off the fuel pump after takeoff at 300-400ft? If this is the only thing supplying fuel to the engine in case of an engine driven pump failure, it seems like the worse time to be turning the pump off. Why not at a much higher altitude, top of climb for example in small GA planes? What do you guys do?

Turn off at top of climb, wings level, and be alert for rough running and/ or a drop in fuel pressure.

Also keep aux pump on during critical stages of flight or extended climbs. There is no harm to the engine in having the aux pump on.

 

 

[Roscoe]

Turn off at top of climb, wings level, and be alert for rough running and/ or a drop in fuel pressure.Also keep aux pump on during critical stages of flight or extended climbs. There is no harm to the engine in having the aux pump on.

And forgot to mention, Pump ON should be one of the Downwind pre landing checks.

 

 

[facthunter]

Good question. Why do it so soon and at a place where a failure is critical.?

 

Some people retract the wheels as soon as airborne. You can sink back onto the runway or have an engine failure and it might be nicer to have wheels to land on. There ARE times where getting the wheels up quickly is needed to meet near obstacle clearance criteria on a M/E plane

 

 

[rage83]

Just remember it takes a moment to switch fuel pump on or off. So switch off check for rough running no good if it is switch back on. I was always taught not to take my hand off switch untill i have confirmed fuel flow stable.

 

Not all aircraft require fuel pump to be used on take off or landing the 172R and S ( with the injected engine ) are examples of this. Fuel pump is only used to prime the engine and obviously in the event of mech pump failure. but not for take off or landing.

 

 

[Roscoe]

Just remember it takes a moment to switch fuel pump on or off. So switch off check for rough running no good if it is switch back on. I was always taught not to take my hand off switch untill i have confirmed fuel flow stable.Not all aircraft require fuel pump to be used on take off or landing the 172R and S ( with the injected engine ) are examples of this. Fuel pump is only used to prime the engine and obviously in the event of mech pump failure. but not for take off or landing.

Yes the POH should be the guide for the particular aircraft type.

 

 

[Yenn]

If you turn off while still climbing and using a lot of fuel, a failed engine driven pump will show up very quickly. So you turn the pump on again and know you have the fault.

 

Turn off in level flight and a failing pump may keep you going, but you won't know it is failing.

 

 

[Happyflyer]

Just remember it takes a moment to switch fuel pump on or off. So switch off check for rough running no good if it is switch back on. I was always taught not to take my hand off switch untill i have confirmed fuel flow stable.Not all aircraft require fuel pump to be used on take off or landing the 172R and S ( with the injected engine ) are examples of this. Fuel pump is only used to prime the engine and obviously in the event of mech pump failure. but not for take off or landing.

And yet a Super Decathlon which also has a fuel injected 180 HP Lycoming like the Cessna requires the fuel pump on until a safe altitude has been attained. I've always wondered why the difference.

 

 

[djpacro]

And yet a Super Decathlon ...

The USA FAA Approved Airplane Flight Manual is required to have all the information required to operate the airplane safely and it is quite clear that the fuel pump is not required for takeoff.

However the additional document, not approved by the FAA, (called the Pilot Operating Manual or just Operating Manual depending on the year) has:

 

 

I rang Jerry Jr at the factory and he said that gravity feed is sufficient, in the event of failure of the engine-driven fuel pump, for the engine to run OK so just conservative to use the pump. It seems that they haven't bothered too much about tidying up these manuals in the last 40 years (several inconsistencies between the documents so merging them into a single POH would be nice).

 

 

 

[pmccarthy]

I was taught fuel pump off at 300 ft but I keep it o til a landing spot is obvious (low wing)

 

 

[kaz3g]

Does it matter if you forget and leave it on during the whole flight?

 

Kaz

 

 

[facthunter]

Would depend on whether it is rated continuous use. and it will be subject to wear, in any case.. IF it is a backup, I would use it in situations where an engine failure is dangerous unless there is some downside to doing so. If there are inconsistencies in the POH the reason should be investigated from the aspect of housekeeping and clarity. The POH is not a flying training manual. Nev

 

 

[dutchroll]

The question has a never-ending stream of answers, many of which might be equally valid.

 

I've heard it said many times that up to and including the initial power reduction after takeoff is the most common time for engine failures in the initial phase of flight, though I don't know how much hard data there is to back this up. I guess if this is correct, then you are taking adequate risk mitigation precautions by keeping the boost pump on until this point, ie, until shortly after your power reduction, which would coincide with the after takeoff checks in many cases (and this is often where the boost pump is turned off).

 

My boost pump is on for takeoff and landing when fuel flow and pressure demand is very high, and very critical (for landing, this would be the go-round case). It is rated for continuous operation so it could be left on all the time, however it is a backup pump (and used for priming) and considered unnecessary for other flight phases, to be reserved for emergency use.

 

 

[Garfly]

I remember reading somewhere that leaving the auxiliary fuel pump on continuously can increase overall fuel consumption. I went a googlin' for a reference but haven't found it. Could've dreamt it.

 

But I did turn this up:

 

http://www.askacfi.com/29466/auxiliary-fuel-pump.htm

 

 

[facthunter]

Leaving a fuel pump on shouldn't affect fuel consumption in normal circumstances with proper pumps used. One good function is to reduce the chance of vapourlock when using mogas. Nev

 

 

[dutchroll]

Just before I started my military flying training I was at Point Cook when a CT4 ditched into Port Phillip Bay after takeoff.

 

The instructor had simulated an EFATO. The military CT4 had a normal and emergency boost pump. The emergency position required a "lift and throw" action as I recall. The student flicked it to emergency (which he wasn't supposed to do unless it was a real engine failure) and the idling engine got a gutful of fuel and stopped. The instructor couldn't get it started again and ditched shortly afterwards. The RAAF crash boat rescued them (although the student almost drowned as for some reason his parachute deployed in the water).

 

That at least was the last I heard of the investigation, though I never read the full report. I don't recall anything much of my CT4 systems training. I think I dumped all of those memories after being made to run the length of the airfield with a life vest and parachute on because I forgot my before takeoff checks once. Luckily the instructor said I could fly the plane well, or I really would've been in trouble.

 

 

[storchy neil]

to be done with caution and fire extin handy

 

get electric fuel pump set up as static display well away from aircraft or other combustable material run into a carby with no escape for excess fuel and you will find that the pump will heat up very quickly causeing fuel vaporization turn on escape line for excess fuel and the heat from electric pump drops greatly

 

this is why rotax have a return line to fuel tank neil

 

 

[kaz3g]

Well Storchy...you have moved the conversation where I was hoping.

 

If you have a return line and you are drawing from the other tank, you will decant fuel to the one with the return line and even eventually lose fuel overboard.

 

Kaz

 

 

[alf jessup]

Well Storchy...you have moved the conversation where I was hoping.If you have a return line and you are drawing from the other tank, you will decant fuel to the one with the return line and even eventually lose fuel overboard.

 

Kaz

Correct Kaz if you do not manage your fuel system correctly

 

 

[SDQDI]

All the more reason to have a little header tank that the wing tanks drain into so that you can't accidently jettison your fuel.

 

With the 914 I run my electric pumps all the time so not as much to remember. What I mean by that is that is the proper way for my plane which coincidently makes it easier, I DON'T mean I leave them on to make it easier and I don't recommend that everyone does that because each plane is different. As has been said the POH should be read and understood and followed.

 

 

[facthunter]

It only happens if the tank the fuel is returning to is full or nearly so.It's part of your fuel management. Know your aeroplane. Nev

 

 

[storchy neil]

POH on some aircraft stipulate how the management of fuel is to be done so hoping that I would shoot my self in foot wont wash

 

POH start up on some aircraft select right hand tank as excess fuel from return line returns to right hand tank after 30 minutes of flight of turn on left tank

 

called fuel management

 

sdqdi does your aircraft have return line to tank neil

 

 

[SDQDI]

sdqdi does your aircraft have return line to tank neil

It sure does Neil:thumb up:

 

 

[Nightmare]

I remember reading an article about a fuel pump being left on, caught fire during a cross country flight, the cabin filled with smoke, and the pilot had to make an emergency landing around Gympie last year. I can't remember if it was supposed to be left on through out the flight.

 

But to address the original post, I guess it greatly depends on the plane, what do their procedures and checklist say?

 

 

[storchy neil]

yep man if you said no I would have wanting to know why

 

bert flood RIP mate and I had many a discussions on this very issue it was bert who inform me that rotax required a return line to tank well before year 2000 to reduce the chances off vaporization and flooding of carby and pressure relief on needle and seat

 

the reason why bert and I had these discussions was that at 100 hrs I had one new needle and seat replaced at 130 hrs 2nd new needle and seat replaced

 

when I found that that there was no return line to tank and informed bert his reply to me was " why not" yet the repair manual clearly shows that return line should have been there

 

it was the maj RIP mate who I also discussed very this issue at temora of not conforming with installation manual it was maj who got me to do the the test that I did about the amount off heat generated by some pumps that do not have pressure relief and heat generated by them is great neil