NTSB report questions

[Hercpilot]

I was recently reviewing some varieze accidents and noticed that there were a couple of statements in the narrative portion of each report that I was unaware of. Can someone enlighten me on the accuracty of these statements.

 

"The aircraft designer specifies that the aircraft be equipped with both an engine driven fuel pump and an electric auxillary fuel boost pump because of the limited headspace between the tanks and the engine."

 

"The early models of varieze aircraft are subject to unporting the fuel tank line when operating with minimum fuel. Later models have a tank sump to correct this condition."

 

Justin

[Kent Ashton]

I think all the canard airplanes are like that. I have problems getting fuel pressure sometimes on start until I actuate the electric primer. Never been able to determine why but I would not fly without the electric pump.

 

Some guys have encountered fuel pressure problems after installing fuel flow sensors in the line. The sensor causes just enough restriction to give pressure problems.

-Kent

[Hercpilot]

I guess I may need to be more specific. I have yet to find in the varieze plans, the requirement to install either an electric pump or a fuel sump. Am I just overlooking those instructions either in the plans or CP's?

 

Justin

[Richard Riley]

The Vari doesn't require either an electric or mechanical fuel pump. It is a good idea to have at least one, if not both.

 

The Long specifically requires a fuel pump. That was the core of the whole Bill Davenport debacle.

[gilbert drieux]

I fly my Lyc O-235 VariEze as per plans.

No electric pump, no sump (? What is it in VE ?).

You MUST select fuselage tank while descending (nose down attitude), as low gas level wings tanks cann't provide gas to gascolator in this attitude.

Read Section II, and VariEze Owner's manual Section IV of the VariEze Manufacturing Manual.

Regards.

 

Gilbert

VE 1736

F-PMPZ @ LFPK (France).

[Hercpilot]

I am aware of the need to switch to the fuselage tank in a descent with minimum fuel in the wing tanks. I am just curious where the NTSB investigator found the information that they state in their respective reports pertaining to either a sump or fuel pump in the varieze.

 

Justin

[TMann]

Justin, you are planning on a boost pump aren't you?

Another option would be to include a sump as a passenger thigh support.

[Hercpilot]

TMann,

I guess that is the question before me. Until reading the NTSB reports, I really had not even considered it. I think I may revisit the idea. Do the facet type pumps allow for fuel flow in the event of failure? Would the pump need to be on all the time or just during critical phases of flight?

 

Justin

[TMann]

I can't speak to that. All of my research has been based on an EFI solution which will require an electric pump.

 

The rent-a-spam-can I fly has both an electric and mechanical pump.

The electric is on during start-up, takeoff, landing and when switching tanks.

 

I'm building the thigh support style of sump vs. the blisters.

[gilbert drieux]

I am aware of the need to switch to the fuselage tank in a descent with minimum fuel in the wing tanks. I am just curious where the NTSB investigator found the information that they state in their respective reports pertaining to either a sump or fuel pump in the varieze.

 

Justin

Migh be NTSB investigators made some confusion on VE vs LE.......

I don't ear on sump on VE.

If a sump is used, under passenger thigh support, the issue to provide it w gas from wings' tanks while descending still exist..... Just a little time more before shut off.... (own many galons in sump / gal per hour => few minutes... )

I'm not in hangar today : What is the sump's WL, and the carburator fuel intake WL ? Difference is certainly less than from wings' tanks; and that is the fuel pressure !.... (Whitout pump).

The pump give security ...... as long it can get fuel from any tank.... (or sump).

 

Regards.

Gilbert.

[Kent Ashton]

Do the facet type pumps allow for fuel flow in the event of failure? Would the pump need to be on all the time or just during critical phases of flight?

The Facet is usually fitted between the tank and the engine-driven pump. It will push fuel through the E.D. pump when the engine is not turning (that's how you develop fuel pressure for start) and fuel will flow through the facet when the facet is off. The facet is mostly used for a backup during T/O and landing but I knew an RV-6 guy who used a pair of them for fuel pressure (no E.D. pump on his engine). Always made me a little nervous to fly with him but they are very reliable little pumps.

-Kent

[Kent Ashton]

(how many galons in sump / gal per hour => few minutes... )

You are usually descending at a low power setting, leaned out, so the fuel flow on an O-320 is probably only a gallon or two per hour or less. If a sump holds a gallon you are good for a hour or so. In addition, there is sloshing into the sump even if the tank port is uncovered. Not something to worry much about.

-Kent