Fuel Pump Operation

[Les Parson]

Greetings,

On the 'Before Takeoff' checklist on page 71 of the manual, Fuel Pump is called to be in the 'ON' position. The language in the System Description section on page 96 suggests the fuel pump should be used during the engine start, emergency ops and vapor lock situations. The latter description is consistent with my real-world POH/checklist.

Just looking to clarify and confirm. Many thanks.

[joespeed52]

[Deleted]

[maubrenta]

The language in the System Description section on page 96 suggests the fuel pump should be used during the engine start, emergency ops and vapor lock situations. The latter description is consistent with my real-world POH/checklist.

Yes that's what I see on my real world V35B Bonanza POH as well.

[AKar]

In some Continental installations, the auxiliary fuel pump causes noticeable enrichment of the mixture which can be enough to cause loss of power and to make the engine run poorly.

Generally speaking, unless specifically mentioned to be fine, auxiliary fuel pumps should not be used just to be safe, except where directed by procedures.

-Esa

[Piper_EEWL]

In some Continental installations, the auxiliary fuel pump causes noticeable enrichment of the mixture which can be enough to cause loss of power and to make the engine run poorly.

Generally speaking, unless specifically mentioned to be fine, auxiliary fuel pumps should not be used just to be safe, except where directed by procedures.

-Esa

But that’s the same for the fuel injected Lycomings no? In our RL C182T the fuel pump is only used for priming and in abnormal procedures (fluctuating fuel flow for example). I’ve never flown a low wing with a fuel injected lycoming though so this might be different then. The low wing carbureted engines all call for fuel pump on during takeoff and landing .

[AKar]

In some Continental installations, the auxiliary fuel pump causes noticeable enrichment of the mixture which can be enough to cause loss of power and to make the engine run poorly.

Generally speaking, unless specifically mentioned to be fine, auxiliary fuel pumps should not be used just to be safe, except where directed by procedures.

-Esa

But that’s the same for the fuel injected Lycomings no? In our RL C182T the fuel pump is only used for priming and in abnormal procedures (fluctuating fuel flow for example). I’ve never flown a low wing with a fuel injected lycoming though so this might be different then. The low wing carbureted engines all call for fuel pump on during takeoff and landing .

In some cases, yes. I know the high-wing Cessnas will run at high power with their boost pumps on, and mixture full rich, but probably at somewhat lesser power. Obviously, mixture settings are adjustable and vary from engine to engine. Carbureted engine installations indeed, at least in most cases, utilize the booster pump during critical phases of flight. These are different in that they use a low pressure fuel system that basically simply keeps the float chamber filled and are not dependent of fuel pressure for engine operation - simply for fuel transfer. In fuel-injected engines, the engine-driven fuel pump plays a critical role as it directly feeds the engine. For this reason, the auxiliary fuel pump is also of relatively high pressure type, to serve as a backup should the engine-driven pump fail. Whether or not they are designed to run together varies somewhat.

It is rather interesting how different the Continental injection system is from the Lycomings. In Continentals, one could say we have a true fuel injection system whereas the Lycoming's creation resembles closely a pressure carburetor. Several Continentals actually don't meter the incoming air at all, but pump the fuel into the engine purely based on lever positions and RPM.

-Esa

[Piper_EEWL]

It is rather interesting how different the Continental injection system is from the Lycomings. In Continentals, one could say we have a true fuel injection system whereas the Lycoming's creation resembles closely a pressure carburetor. Several Continentals actually don't meter the incoming air at all, but pump the fuel into the engine purely based on lever positions and RPM.

-Esa

Mhh that sounds very interesting indeed. Do you know if any of this is covered in the manual? I think I'll best go and read it soon. Those this also vary between the IO-520 and IO-550 or is this a Continental Engines specific design feature.

This release already makes for interesting discusssions even though we haven't flown it yet...

[AKar]

It is rather interesting how different the Continental injection system is from the Lycomings. In Continentals, one could say we have a true fuel injection system whereas the Lycoming's creation resembles closely a pressure carburetor. Several Continentals actually don't meter the incoming air at all, but pump the fuel into the engine purely based on lever positions and RPM.

-Esa

Mhh that sounds very interesting indeed. Do you know if any of this is covered in the manual? I think I'll best go and read it soon. Those this also vary between the IO-520 and IO-550 or is this a Continental Engines specific design feature.

This release already makes for interesting discusssions even though we haven't flown it yet...

Baseline models are pretty much the same, including IO-520 and IO-550 (of which, btw, I regard IO-550 a much better engine, sampling the few sub-models I've got something to say about). The function of the Continental injection system is not very well described in most old-style POHs, but is included into engine manufacturer's operating manuals and supplementary documents. By quick browsing, it is not covered in A2A Bonanza's manual.

See here for general description and some discussion [pdf].

While not the first thing to learn when starting to fly an airplane, I think it is somewhat important to have an overall idea on how the fuel system of the engine works, be that a carburetor, Bendix servo as in Lycomings, or Continental's fuel injection system. The differences in between them have subtle but important consequences in how to operate these machines.

-Esa

[Scott - A2A]

Les,

Good spot, the fuel pump should be off for takeoff and I can see it referenced in other places where it shouldn't be. We just made these corrections for an update. However to be sure I will run this over with our long time Bonanza pilots to see if there is any unofficial uses of the pump other than that is described in the manual.

Scott.

[Les Parson]

Les,

Good spot, the fuel pump should be off for takeoff and I can see it referenced in other places where it shouldn't be. We just made these corrections for an update. However to be sure I will run this over with our long time Bonanza pilots to see if there is any unofficial uses of the pump other than that is described in the manual.

Scott.

Ok, thanks Scott. My former boss has an F33. I thinks it's the same engine. I can ask him if need be.

[Scott - A2A]

Les please do. I have found, especially in aviation, if you ask 100 pilots the same question, you will get 100 different answers. Which is why we have to create such an elaborate process for finding the "real" truth in so many areas.

Scott.

[CodyValkyrie]

I’ll ask my mechanic friend that I did some work for. He’s been working on Bonanzas for most his life.

[AKar]

Better yet, anyone having an access or knowing someone who has an access into Bonanza might as well try it out. Rich mixture, high power - with auxiliary pump enabled, I'd suspect the engine will lose power or even fail to run properly, though the effect may be mild at sea level.

-Esa

[Les Parson]

Les please do. I have found, especially in aviation, if you ask 100 pilots the same question, you will get 100 different answers. Which is why we have to create such an elaborate process for finding the "real" truth in so many areas.

Scott.

Wilco - I'll report back.

[Les Parson]

Scott,

The following is the response re Aux Fuel Pump operation from my contact who is a current F33A owner with the same engine (IO-520 285 HP).

Les

Thanks for the note. Let me do some research but the answer is “it depends”.

What you’re referring to is the electric fuel pump, versus the fuel pump which is mechanically driven by the engine. In many model Bonanzas the electric pump is as you describe, used on the ground to prime the engine before start, assist with a hot start (vapor lock) etc and in flight be available in case of mechanical fuel pump failure (manual activation required by the pilot) as the engine will not run without positive fuel pump pressure I.e. the engine will not “gravity feed”. Use of both mechanical and electric pumps is not recommended in these model Bonanzas as it “oversupplies” the engine with fuel (they are additive) and will cause the engine to run rough. In fact, if the electric pump is on, the engine may not stop running at shutdown even if the mixture is pulled full lean.

This is how my Bonanza works.

However, there are certain models with a two stage pump (Hi/Lo) in which the pump is used for takeoff (and landing I believe) as a backup in case the mechanical fails during these critical phases.

I don’t want to tell you from memory the models though I believe it may be the turbocharged models. Let me do some more research and I’ll get back with you today or tomorrow.

I hope this helps.