Fuel in the Cockpit

[wintaki]

Hi, I was reading another thread where someone mentioned the tragic Von Alexaner accident.

I was curious how the fire could get into the cockpit (I am a RV builder wannabe so I dont have much knowledge right now). I read in the accident report there seamed to be evidence of fire inside the cockpit around the gascolator area. Do RVs normally have fuel coming thru the cockpit? Can they be built so fuel does not enter the cockpit at all?

How likely is it that an engine fire gets into the cockpit? This scares the heck out of me.

 

[Kyle Boatright]

Hi, I was reading another thread where someone mentioned the tragic Von Alexaner accident.

I was curious how the fire could get into the cockpit (I am a RV builder wannabe so I dont have much knowledge right now). I read in the accident report there seamed to be evidence of fire inside the cockpit around the gascolator area. Do RVs normally have fuel coming thru the cockpit? Can they be built so fuel does not enter the cockpit at all?

How likely is it that an engine fire gets into the cockpit? This scares the heck out of me.

If I recall correctly, the NTSB report didn't show any evidence of fire entering the cockpit. Speculation (which made sense to me) was that Von had unstrapped and might have been reaching for a fire extinguisher in the rear seat when he bumped the stick and was ejected from the aircraft. There was no evidence of heat to his clothing or body, so it doesn't make sense that he intentionally jumped.

As for fuel in the cockpit. That's how most GA aircraft with fuel valves are plumbed. For the fuel valve to be within reach from the pilot's seat, the valve must be in the cabin and the fuel lines must be routed to the valve. There are certainly work-arounds which would keep the lines outside the fuselage, but running external fuel lines seems clunky, as does a remote (electrically operated) fuel valve.

 

[robpar]

I have wondered about fuel passing through the cockpit myself. I am also a non builder but hope to build in the future.

I have been a licensed natural gas installer for automobile and trucks and fuel lines running through the passenger compartment is very much against code. If you have a fuel selector it has to be either electric or the valve and fuel lines must be separated by a metal bulkhead with the manual lever reaching into the compartment. This also applies for gasoline in automobiles and racing vehicles at least drag race cars.

Could something like this not be arranged? Having fuel lines in the passenger compartment seems to be needlessly risky. Most of the fuel components I have seen for aircraft have NPT tapered threads. I have bitter experience with NPT threads leaking and would not like to have them in my cockpit. There are some components that use an O-Ring seal and as long as it is compatible with the fluid being used are much less leak prone than NPT.


What about fuel pressure guages? In drag racing rules the guage has to use an isolator so that no fuel is brought into the cockpit. Just wondering about the practice in experimental aircraft.

Bob Parry

 

[n5lp]

It is normal practice in light aircraft to have the fuel selector valve in the cabin area. The builder of the EZ that John Denver died in was concerned about that.

"The fuel selector handle location was discussed with the seller and other pilots who had flown the accident airplane. The seller reported that he had asked the builder why he had located it behind the pilot's left shoulder. The builder responded that he did not want fuel in the cockpit area. The seller said that when he changed tanks inflight he would engage the autopilot, allowing his right hand to reach behind his left shoulder to the selector handle."

The complicated and awkward location of the resulting selector handle seems to have contributed to that particular accident.

There are always trade-offs.

 

[N941WR]

... If you have a fuel selector it has to be either electric or the valve and fuel lines must be separated by a metal bulkhead with the manual lever reaching into the compartment. This also applies for gasoline in automobiles and racing vehicles at least drag race cars.

Could something like this not be arranged?

What about fuel pressure guages?...

Bob,

In the Side-by-Side RV's (I don't know about the -3, -4, & -8) the fuel lines come through the side of the cabin, under your legs, forward of the spar, to the fuel valve. From there one line goes forward to the fuel pump. If you have an injected engine the high pressure pump is just forward of the fuel valve, if carbureted the low pressure pump is mounted on the cabin side of the firewall. From there the line goes through the firewall.

Your option is to run the lines and pumps on the outside of the fuselage and make some type of cover. If you put a bulkhead on the inside, you will still have fuel under your legs.

The lines are covered by inspection plates, which are removed every year at your condition inspection. In my case, I flew the first 15 hours w/o them installed so I would be able to spot any leaks.

Most new RV's have electric fuel pressure senders, mounted high on the left forward side of the firewall, so that line does not penetrate the firewall. Same goes for the oil pressure line/sender.

As for the gentleman who left his burning -8 w/o a parachute, I have read that he had no burns on him but in studying WW I pilots, who did not have chutes and had to make the choice of shooting themselves or jumping when their plane caught fire, I suspect the gentleman did jump once things on the inside got hot enough. What a horrible choice to make!

Someone mentioned that they thought he might have been ejected when reaching for a fire extinguisher in the backseat. This brings up a good point. If you mount your fire extinguisher where you can't reach it from your seat, you might as well not have one.

 

[Geico266]

If you re-read the accident report from Von's incident you'll find more info.

"The only evidence of heat/fire distress observed during post-mortem was the pilot's eyebrows and forward hairline. The aircraft's canopy is airfoil shaped and during flight conditions would tend to create an aerodynamic low pressure condition near the top of the canopy. If the canopy were opened in flight with fire conditions existing along its forward exterior surface, the entrainment of hot air and fire within the upper cockpit interior environment may have become intolerable for the pilot."

 

[robpar]

Bob,



The lines are covered by inspection plates, which are removed every year at your condition inspection. In my case, I flew the first 15 hours w/o them installed so I would be able to spot any leaks.

.

Inspection covers if sealed should be more than acceptable. I know there is not much room to run all these tubes so compromises have to be made. Running the tubes outside the plane does not seem to be much of a choice.

Electric sending units are the way to go for fuel and oil pressure but some, especially in the racing community, want the mechanical guages. I prefer the look of the 270 deg sweep mechanical guage to the 90 deg sweep of many electrical guages, but there are electrical guages with the look of mechanical ones.

Bob Parry

 

[N941WR]

Inspection covers if sealed should be more than acceptable. I know there is not much room to run all these tubes so compromises have to be made. Running the tubes outside the plane does not seem to be much of a choice.

That would be a challenge as you will need to find a way to seal them and yet be removable for inspection.

Remember, your electrical wires run up that center tunnel as well.

When it comes to your fuel system, I would be very reluctant to change anything. Most accidents are a direct result of fueling issues which can be traced back to non-standard fuel systems. The RV design has worked well for over 5000 aircraft, think two or three times before playing with it.