[dustman]

Question for the group . My 3 is and older aircraft has the fuselage tank and no mechanical fuel pump. My question is there any issues that i should be concerned about here the plane was flown fo many years without one, but my AP has introduced doubts into my head he says that i should have one. The plane has an electric boost pump. What is the correct answer here. Thanks for any help. Engine 290-D,

 

[flyboykelly]

Your A&P is probably refering to FAR 23.991 (a)(1)

(1) For reciprocating engine installations having fuel pumps to supply fuel to the engine, at least one pump for each engine must be directly driven by the engine and must meet §23.955. This pump is a main pump.

23.955 refers the pump having bypass considerations.

Even though your aircraft is experimental, these certification standards are what A&P mechanics are trained to identify for certified aircraft airworthiness.

I personally believe that any experimental aircraft should be built as close to a certified aircraft standard as possible. If I were in your shoes I would install a mechanical engine driven fuel pump.

 

[hughfi]

In a climb I think it matters.

I have found that in a climb to higher altitudes (+7000ft) fuel pressure drops by quite a bit even with an engine pump. I assume this is because the engine is higher than the wings by a bit combined with the fact that as the air gets thinner, pumping becomes harder. In my view you absolutely need a fuel pump and a gascolator, plus a boost pump with a low wing aircraft. I know older cessna's don't have one, but there is one in all new aircraft and their fuel is above the engine in a climb.

For what its worth, its not hard to install one at all.

Hugh.

 

[frankh]

Personally

I would fit a second Facet electric fuel pump

1) Its cheaper ($32)
2) Its less susceptable to vapour lock if its not on the engine side of the firewall.
3) Available at your local autpoarts outfit.

If you do this ake sure you get th correct one..The 40105 makes less pressure than the 40106 already i would match it but it might be a bit much for you carb needle..I.e I suspect a 105 might be a better application.

Make sure you wire them independantly..I,e seperate fused circuit and seperate switch for each one.

Frank
IO360 with wingroot electric pumps and no mechanical pump.

 

[rv8ch]

gravity fed header tank

Question for the group . My 3 is and older aircraft has the fuselage tank and no mechanical fuel pump. My question is there any issues that i should be concerned about here the plane was flown fo many years without one, but my AP has introduced doubts into my head he says that i should have one. The plane has an electric boost pump. What is the correct answer here. Thanks for any help. Engine 290-D,

If I understand your setup correctly, then you have a gravity fed header tank which is higher than the carb. Do you use your boost pump for takeoff and landing, and the rest of the time leave it off? If so, then this is not a lot different from a high wing aircraft, assuming the static head (pressure head) between the carb and the header tank is high enough. I'd check with Van's to get their advice.

 

[Mel]

Another consideration...

Obviously, you didn't build your aircraft. If you have an A&P who maintains it, you need to make him comfortable also.

 

[rv7charlie]

Mustang II's, Midget Mustangs, and Thorp T-18's have been flying with header tanks & no fuel pumps for a lot longer than RV-x's.

Ultimate test: Call Van's.

Certified stuff is a good starting point, but one of the reasons for going experimental is we get a chance to do it better, which can have many definitions.

Charlie

 

[N941WR]

Dustman,

It is very easy to modify the O-290 for a fuel pump.

All you need is an accessory case (standard O-320 part), cam gear, fuel pump push rod, some gaskets, and of course the fuel pump.

While you are at it, can dump the oil screen and install a filter adapter, thus extending your oil changes to 50 hours. (I smell a cost justification here.)

There are details of the conversion on engine page.

 

[az_gila]

Compare to a certified...

Your A&P is probably refering to FAR 23.991 (a)(1)

(1) For reciprocating engine installations having fuel pumps to supply fuel to the engine, at least one pump for each engine must be directly driven by the engine and must meet ?23.955. This pump is a main pump.

23.955 refers the pump having bypass considerations.

Even though your aircraft is experimental, these certification standards are what A&P mechanics are trained to identify for certified aircraft airworthiness.

I personally believe that any experimental aircraft should be built as close to a certified aircraft standard as possible. If I were in your shoes I would install a mechanical engine driven fuel pump.

...Cessna - many of which have no pumps.

Since the FAR says that only if you have a pump, then it must be engine driven. It does not mandate a pump.

If you remove the electric pump, you will be in compliance with the FAR....

Will the RV-3 operate in normal flight modes on a gravity flow only with no pump?

 

[dustman]

pump

I have not flown it yet been spending the last year putting it back together. The POH calls for the pump to be on for take off and landing only. Im assuming that in level flight there is no need for a pump and level flight will be the extent of my flying.I would rather not take the engine out again to change the case.

 

[az_gila]

Ask your A&P...

I have not flown it yet been spending the last year putting it back together. The POH calls for the pump to be on for take off and landing only. Im assuming that in level flight there is no need for a pump and level flight will be the extent of my flying.I would rather not take the engine out again to change the case.

...why it should be different from a C-150 or C-172 fuel system - certified with no pumps.

My guess is he might be concerned about the flow rate in climb when the head of fuel is reduced....

 

[N941WR]

...I would rather not take the engine out again to change the case.

No need, you can pull both cases with it on the engine mount. Granted it won't be that easy but you can do it.

Do a flow test before your first flight. Tony Bingelis' Firewall Forward book, page 176 shows how to do this. The basic steps are:
1) Establish the plane at an extreme climb angle by digging a hole for the ail and putting blocks under the wheels.
2) Disconnect the fuel line at the carb and time how long it takes to drain one gallon.

FAR Part 23.955 covers fuel flow.
"Gravity systems - The fuel flow rate for gravity systems (main and reserve supply must be 150% of the takeoff fuel consumption of the engine.

Pump Systems - The fuel flow rate for each pump system (main and reserve supply) for each reciprocating engine, must be 125% of the takeoff fuel flow for the engine at the maximum power approved for takeoff..."

(That quoted section is from the Tony's book, the FAR's may have changed since he wrote it.)

Good luck with your flight testing.

 

[rv8ch]

find a hill

...
1) Establish the plane at an extreme climb angle by digging a hole for the tail and putting blocks under the wheels...

Is Huntersville pretty flat? Around here it would be easier to find a little hill.

 

[frankh]

Gee

If you have to change out the accessory case you might as well just put a second Facet in parallel...A lot less work!

Frank

 

[N941WR]

Is Huntersville pretty flat? Around here it would be easier to find a little hill.

Nope, I could just pull the plane out in the front yard and it would be give me the angle I needed.

If you have to change out the accessory case you might as well just put a second Facet in parallel...A lot less work!

Frank

Yes it is a good bit of work but the Facet still relies on your electrical system. The idea is to have an engine that can continue to run w/o your electrical system. That's why most low wing planes have both an engine driven pump and an electrical pump.

 

[dustman]

Pump

Bill thanks for your web page on the conversion. I wish the AP would have voiced his concerns when he had the engine off for the inspection and I had remembered that I had an acc case with the fuel pump pad. This could have been an easy fix. Here is another question currently the engine is certified and if I understand the rules correctly, if I go and replace the case myself the certification goes away. I guess my next question is, is it a big deal if the certification goes away. I would assume if I were not planning on ever selling it no big deal do the fix and move on. How much difference would it make to a potiental buyer? What would you guys do?

 

[Geico266]

If you have to change out the accessory case you might as well just put a second Facet in parallel...A lot less work!

Frank

What would you guys do?

Frank has it right. Add a second Facet and call it good. You can hook them up in series in the same fuel line and one will pump or draw through the other. My -3 has no mechanical pump and 2 Facets (wing tanks). It has worked well since 1996. Without a fuel pump running my big fan stops.

 

[N941WR]

...Here is another question currently the engine is certified and if I understand the rules correctly, if I go and replace the case myself the certification goes away.

Since the engine is on an experimental, it is no longer considered "certified", as I understand it. (Mel?) Thus, you can do whatever you want to it. Just do it in a way that is airworthy. You are right, it is a bummer you didn't catch it sooner.

The good news is the O-290 is easy to remove and install because of the conical mount.

I guess my next question is, is it a big deal if the certification goes away. I would assume if I were not planning on ever selling it no big deal do the fix and move on. How much difference would it make to a potiental buyer? What would you guys do?

Not really a big deal. Since it has lived on an EXP, it would be difficult to sell for use on a production plane. Anyone who might buy it to hang on a PA-20/22 or some such plane will probably major it before putting it back in service so that is not a big deal.

You already know what I would do, I would change it out. The 2nd electric fuel pump is an option but it is subject to an electrical failure, just like the other one. That's why we have both. If the engine driven pump fails, the backup is the electrical pump. If the electrical pump fails, the backup is the engine driven pump.

 

[rvbuilder2002]

Another viewpoint...

If your A&P is referencing FAR's...ask if he would consider oking the installation if it meets the flow requirements of FAR 23.
If I remember correctly, a pumped system (low wing with wing tanks) must be able to supply 150% of the maximum flow rate required by the engine when measured at the carb. inlet at max possible angle of attack, and a gravity fed system requires 125 % of the max. flow rate required at max. possible angle of attack.

Stick the tail in a hole
Put a minimal amount of fuel in the tank (couple gallons)
Remove the hose form the carb and time how long it takes to drain one gallon with the hose end held at the same elevation as the carb. inlet.
Divide 60 minutes by the time to flow one gallon and you have your gallons per hour flow rate.
If the measured flow rate is at least 125% more than the max required by your engine, you are good to go...if not, install another pump.

 

[dustman]

pump

This is such a great site you can always get advice and generate even more questions. Here is another question since my plane has the header tank theoritcaly the head generated from the tank to the carb should have suffient pres as a primary system and the elec pump would be a back up pump so a second pump would give you double redundancy.

 

[N941WR]

This is such a great site you can always get advice and generate even more questions. Here is another question since my plane has the header tank theoritcaly the head generated from the tank to the carb should have suffient pres as a primary system and the elec pump would be a back up pump so a second pump would give you double redundancy.

True but how long can you fly with the fuel in header tank and do you think you would nice it if the electric pump stopped working?

Let me ask you, is the electric pump between the fuel selector valve and the header tank or between the header tank and the engine?

Do you fly with the electric pump on all the time? If so, why not climb up high, turn off the pump and see how long (if?) it takes for the engine to start sputtering when climbing.

Remember, the reason for the electric pump is there is to act as a backup to the engine driven pump. The reason we turn them on for takeoff and landing is so we don't have to do anything should the engine driven pump fail during takeoff.

 

[rvbuilder2002]

This is such a great site you can always get advice and generate even more questions. Here is another question since my plane has the header tank theoritcaly the head generated from the tank to the carb should have suffient pres as a primary system and the elec pump would be a back up pump so a second pump would give you double redundancy.

True but how long can you fly with the fuel in header tank and do you think you would nice it if the electric pump stopped working?

Let me ask you, is the electric pump between the fuel selector valve and the header tank or between the header tank and the engine?

Do you fly with the electric pump on all the time? If so, why not climb up high, turn off the pump and see how long (if?) it takes for the engine to start sputtering when climbing.

Remember, the reason for the electric pump is there is to act as a backup to the engine driven pump. The reason we turn them on for takeoff and landing is so we don't have to do anything should the engine driven pump fail during takeoff.

I think it is causing confusion by referring to the tank as a header tank. If I understand correctly, this RV-3 has an earlier version fuel system with no wing tanks, just a single fuselage tank fwd of the instrument panel. A header tank by definition is generally a small tank fed by other remote tanks in the wings, other areas of the fuselage, etc. All fuel feeds to the engine through the header tank. Neither of the two different standard fuel systems used in RV-3's over the years used a header tank. I am pretty sure the standard fuselage tank fuel system used no fuel pump at all. It was gravity fed only.
It sounds like this RV-3 was built with an electric fuel pump between the fuselage tank and the carb. Because of the flow resistance of the pump, this could actually reduce the gravity fed flow rate. This was part of the reason I recommended you do a flow test.

A second electric pump would not necessarily give you double redundancy, it may actually reduce the gravity flow rate even more (depending on the pump you installed). Maybe enough that you would need one pump turned on all the time.

Before you do anything, I would highly recommend that you do an accurate flow test (airplane in proper flight attitude, etc.).

 

[Tom Muller]

Use of the Electric Fuel Pump

I have a related question. My RV-9A runs very well on the mechanical fuel pump alone and so I have been using the electric boost pump only to power the gascolator sump and the electric primer. I start and run the engine, which was new when I built the airplane, on the mechanical pump alone. I have not been using the electric pump for landings or takeoffs in order to reduce cockpit workload and preclude running the airplane too rich or wearing out the electric pump.

Am I taking a serious risk of engine starvation? I have been doing this for 150 hours without a hickup.

 

[Ironflight]

I have a related question. My RV-9A runs very well on the mechanical fuel pump alone and so I have been using the electric boost pump only to power the gascolator sump and the electric primer. I start and run the engine, which was new when I built the airplane, on the mechanical pump alone. I have not been using the electric pump for landings or takeoffs in order to reduce cockpit workload and preclude running the airplane too rich or wearing out the electric pump.

Am I taking a serious risk of engine starvation? I have been doing this for 150 hours without a hickup.

Clearly, engine driven pumps don't fail that often, but if it did, and you were on take-off, flipping on the backup pump is one more task you'd have to do, in addition to flying the airplane. What you are doing works, obviously, but every aircraft checklist I have handy (for airplanes with backup electric fuel pumps) has me turn the pump on before take-off, and off after I climb 1,000' AGL. There is no real reason not to do it - the pumps sound like they are hammering themselves to pieces, but they actually last a very long time - and that one time you might want it, it could save your life.

I personally use "Aux Pump - ON" for every take-off and landing.

Paul

 

[N941WR]

...
I personally use "Aux Pump - ON" for every take-off and landing.

Paul

Same here and when switching tanks.

The only "warning" light I have on my panel is a green LED light, centered above my EFIS. It is wired in parallel with my fuel pump and is right in my line of site when taking off and landing.

(The EFIS handles all the other warnings with tones and a message.)

 

[IowaRV9Dreamer]

can too much pumping really make an engine rich?

I have not been using the electric pump for landings or takeoffs in order to reduce cockpit workload and preclude running the airplane too rich

Correct me someone, but I don't think the use of a boost pump in a carb engine will richen the mixture, right? As long as there is fuel in the bowl, the engine should run - the pump (mechanical, electrical, or both) just keeps fuel in the bowl. The float & valve should keep the bowl from overflowing, so the engine can't get "too rich". Do I have this right?

The point about wearing out the pump is fair, though.

 

[rvbuilder2002]

Correct me someone, but I don't think the use of a boost pump in a carb engine will richen the mixture, right? As long as there is fuel in the bowl, the engine should run - the pump (mechanical, electrical, or both) just keeps fuel in the bowl. The float & valve should keep the bowl from overflowing, so the engine can't get "too rich". Do I have this right?

The point about wearing out the pump is fair, though.

Yes you have it right.
The only way a boost pump could cause a richer mixture is if there is something wrong with the carb. (needle valve leaking, float leaking/sinking, etc.).