Fighting Fuel Foolery

This was meant to be the last of four articles persuading instructors, and everyone else, that they will have a longer and happier life if they understand this 20 point outline of the fuel system.

But it’s not the last one. I underestimated how much more there was to be said about a system that’s just waiting to betray ignorant or unwary instructors and pilots.

 We are making progress, but it’s taken four articles and 10,000 words (that’s like a young Wilber Smith novel) to get us about three quarters of the way to a place of comfort.

Would you trust a doctor who doesn’t understand your blood system, or an electrician who is vague about wiring, or a neurologist who is puzzled by your nervous system? Okay, so the same applies to pilots and fuel systems.

If a pilot only understands one thing about the machinery under his command, let it be the fuel system.

And you, budding instructors, are the ones to bring this about. It’s your job to make it interesting and memorable by involving your pupes in a tour through the labyrinth of pipes and wires and valves and drains and taps that will keep the engine running and everyone smiling.

The 12 fuel selector

I was looking at an accident report the other day where a 20 year old commercial pilot lost both engines in a Seneca soon after takeoff. Why? Because both selectors were in the OFF position.

Silly bugger you might say. Well, yes and no. Yes, he was vastly overconfident for one with so little time on the aircraft. If he wasn’t sure where the selectors should be, he could have looked in the POH. Particularly as the decal showing the OFF, ON and X-FEED positions was missing.

So he bet his life on guessing – and got it wrong. Fortunately the goddess who looks after old ladies, little lambs and student pilots extended her benevolence to this young man. She merely waved a finger in his face and said, “you’re living on borrowed time, my boy.”

The moral of the story is that you must think very carefully before doing anything with the fuel selector.

If the decal showing the various positions is missing, then the aircraft is unserviceable.

And how about the plate in the C150 and 152s, which is meant to show the OFF and ON positions? The plate sits flat on the floor but it’s trying to tell you what to do with a lever which rotates in a perpendicular plane to the floor. It always puzzles me.

And then there are fuel selectors that don’t get serviced because they are difficult to get at. Eventually they are so worn and gunged up that you can’t feel the detent positions. Again, an aircraft like that is unserviceable.

There is also the fuel selector that’s so stiff that forcing it eventually breaks or bends part of the mechanism and it fails to select what you think you have selected. There was a Tecnam 2006P that crashed on the reef a while ago because of this.

Wilber Smith would be jealous of my literary output if I were to write a book called One Hundred True Stories About Fuel Selector Stuff-ups (abridged version).

Seriously – if there is one control in the whole aeroplane that screams, stop and think, and note the time, before you touch me, it’s the fuel selector.

And now here’s something more to think about. Why do so many pilots switch the fuel off after flight?

As an instructor I have always taught pupils to do that – not because I particularly want to isolate the engine from the tanks, but because I want the next pupil to develop a lifetime habit of switching the fuel on before he tries to start the engine.

I’m still not sure why other people do it. I guess the main reason for having an OFF position is in case of fire, but perhaps there are other reasons. Certainly a high-wing, normally-aspirated aircraft may leak fuel from the float chamber – perhaps that’s good enough reason for making a habit of turning it off.

Now I’m going to stick my neck out. About six months ago two guys, Richard McSpadden (5000 hours) who was the much-respected senior vice president of the AOPA Air Safety Institute, and Russ Francis (9000 hours) were flying a Cessna 177 RG when it crashed soon after takeoff, killing them both. The NTSB Preliminary Report says that the engine stopped while they were taxying out at Lake Placid. Quote:

There were several witnesses to the event. One told investigators that when the accident airplane pulled up next to the Beech A36 on the ground, that the accident airplane’s engine then shut off, and about 10 seconds later, the engine restarted. 

No, it wasn’t carb icing – the aircraft has a fuel injected engine.

If the engine stops, for no apparent reason, while you are taxying, are you simply going to restart it and carry on with your flight if you don’t know why it stopped?

Of course you’re not, but you can see where I am going with this indictment. The only reason I can see for the engine stopping and then restarting at the touch of a button, is that they both knew exactly why it had stopped – they had forgotten to switch the fuel on in the first place. They realized their mistake and quickly rectified it. Just my opinion.

It’s doubtful whether this had anything to do with the ultimate loss of power that led to them just failing to get back to the field. However several witnesses said they thought the engine didn’t sound as if it was producing full power during the takeoff and climb. Let’s hope the final report clarifies this.

Summary: I believe that two top pilots, with a total of 14,000 hours, forgot to switch the Cardinal’s fuel on.

I’m guessing that this may have been because of divided responsibility and no clear briefing as to who was actually flying this simple little aeroplane.

Dear instructors let that be a lesson to you and your pupils. Always be very clear about who is flying and who is responsible for what.

I like to check fuel selection three times before leaving the ground. Once during my round-the-cockpit inspection before start-up. Then once again during my round-the-cockpit after-start checks. And finally once more during my pre-takeoff vital actions.

And they are called VITAL actions, not ‘checks’, for the very good reason that they are vital to your future tenancy on this planet.

13 fuel low point filter

I had an engine failure in Twin Comanche ZS-EVB at George. It was at the worst possible time – just after takeoff.

Instructors – you are the best people to deal with such misfortunes because you are pretty much current and in practice. You shouldn’t really have to think what to do. You fly the aircraft with one hand and your feet, while muscle memory takes your other hand behind all the power levers and eases them fully forward. It then raises the gear and flaps.

You can then all relax and go through the dead-foot-dead engine, confirming and feathering routine. Bank a few degrees into the dead engine, trim and then relax some more while you make a plan and tidy up the cockpit. Finally let ATC know what your plan is.

But I am drifting off the subject. Why did the engine stop when I most needed it?

This is an interesting one. The twin Comanche has two of these little low-point filters and drains. They are under the fuselage and hidden behind a small hatch. And therein lies the problem. The smallness of the hatch.

One of them is very easy to get at, and the other is a bastard. So much so that engineers when doing MPIs are inclined to pull the left one out, clean it and service it. They then have a look at the right hand one and decide to have a tea break before tackling it. Over tea they reason that the previous guy probably serviced the right hand one so there is no reason for him to do it. It will be fine for another 100 hours.

You can see where this is going – the right hand one on EVB never got serviced in its entire life, and I think it was the oldest Twin Comanche in the country.

When the engineer, Dave Milne, eventually got it out, with much cursing over cut knuckles, he showed me what was inside. It looked like muddy water. It actually was completely full of water, but the mud colour was rust. In the bottom was a corroded bit of bent wire – that was all that was left of a large spring.

The moral – if a drain is difficult to get at, that’s all the more reason that you MUST get to it.

And how about those really silly ones on the 100 and 200 series Cessnas? There is a white knob that you get at through the hatch where you check the oil. Nice and convenient – you don’t have to bend down for it to shoot a dollop of fuel straight into your shoe.

Worse still, it leaves a puddle of fuel on the concrete directly where the exhaust is about to send flames if it backfires during startup. There have been several Cessnas burned to the ground by this bit of idiocy.

14 The primer.

This is an interesting little gadget that gives you a nice rich mixture for cold starts. Basically, it’s a choke replacement. Every time you unlock it, pull it out and shove it in again, you are actually operating a sort of syringe – pulling it out fills it up and pushing it in injects vaporized fuel into the head, just before the inlet valve.

Here are three crash/don’t crash facts that many instructors don’t know about primers, so how are ordinary pilots meant to know them?

First fact, how do you tell if it’s properly locked, and does it matter? Yes, it does matter a lot, because if it comes unlocked the engine will run rough and lose power.

When you push it in and give it a bit of a turn, you should know what’s going on behind the scenes. Have a look at the photo. The yellow blobs show where two indents are. These are designed to stop the primer from slowly turning until the peg pops out of the hole and unlocks the primer.

The POH, or your instructor, will tell you that after priming you should push the peg into the hole and turn it 90 degrees. This will take the peg into the ‘safe’ zone where it can’t come unlocked. If it turns for any reason the peg will go into one of the indents and prevent it from turning any further

Now, if you are not going to use the primer you have probably been taught to pull gently on it to make sure it’s locked – that’s fine – but if you give it a bit of a twiddle – just to make sure, then you stand a chance of twiddling it into the minute ‘unsafe’ zone – that’s the small gap between the indent and the hole. If it then pops out of the hold you will lose power – possibly during takeoff.

Second fact. If you have a look at the engine you will notice that those thin primer pipes don’t go to all the cylinders – usually three out of four on Lycomings. This is to make sure that if you have primed too much and flooded the engine, at least one cylinder is not flooded so she stands a chance of starting on that one.

Third fact – under certain conditions you may be able to use the primer to give you a bit of power after a complete, or partial, engine failure. It will get fuel to the cylinders if dirt, or water, or something else is preventing the carburetor from doing its job. It’s a long shot, but always worth a try if you need some extra urge to get you to that forced landing field.

15 Fuel system low point drain.

We covered this pretty thoroughly under 13 fuel low point filter. We need to think about the consequences of accidentally leaving this drainin the open position. A high-wing aircraft will let the fuel run out as soon as you switch the fuel on. With a low-wing aircraft, the fuel may only run out when you switch the fuel on and the electric pump on.

Either way it’s theoretically possible to be streaming fuel into the atmosphere while in flight. You won’t see it – in that way it could be similar to leaving the fuel cap off on a high wing.

It seems that ship’s captains and engineers need to take a leaf out of pilot’s operating procedures. It sounds as if the crash of the container ship, Dali, into the bridge in Baltimore was probably caused by dirty fuel.

These ships usually have two huge supercharged two-stroke diesel engines driving a single propellor. They only use one engine while moving slowly. That engine not only turns the propellor, but it also powers all the electrical and hydraulic systems. And both those systems are used to move the rudder for steering.

Like aircraft, they have fuel filters and water drains. It sounds as if these were either inadequate or were not properly serviced and drained before departure, allowing dirt to block the fuel injection nozzles, causing the engine failure.

Then they have the equivalent to an APU which takes a bit of time to come on line and then it only supplies limited electrical and hydraulic power.

Short story – if you don’t drain the filter bowl you can cause a monstrous nonsense on anything from a little aeroplane to a bloody great ship.

As an afterthought, the Gleitch and I were delighted to receive the following letter:

Dear Guy

I have been following the Jim Davis articles on fuel.  He may not remember this but in about December 1995 I was in Port Alfred when I saw SAA’s JU-52 flying overhead.

I drove out to 43 Air School because I heard it was due to land there. When I arrived, the aircraft was being refueled. Jim was supervising this operation from the back of a horse. He was riding bare-back, wearing no shoes and had a parrot on his shoulder.

I commented on this to one of his staff, a young WW (Weekday Worker – I believe). Who said that Jim sometimes came to work in his 1936 Dodge Fire Engine – complete with ladder and brass bell – and with the same parrot on his shoulder.

The youngster looked round to make sure no one was listening and said, “I think he is a bit eccentric.”

Just thought you might enjoy this story.

All the best


GL writes: When I asked Jim to comment he admitted it was true – but said it was only at weekends.