Fuel Gage Indication: “Pucker Effect” versus Reality

[Jack Tyler]

Rich, thanks for posting your report. Your various mitigating strategies are all good food for thought. Altho' not mentioned, I was left wondering if you also adjusted your altitude to minimize the headwind, another thing a pilot can consider when trying to stretch the available fuel.

But I agree with you: you were too light on fuel for that return trip and were not safe. IMO 2.2 gals does not feel like a dependable 1/2 hr reserve for you. If the headwinds on the return flight had incrementally inched up, if you'd run into afternoon efficiency-robbing turbulence, if you hadn't been as careful as you were in taking onboard the fuel in the first place...there are lots of reasons why a 1 hr fuel 'bingo' makes sense for us amateur pilots.

I did a bit of checking. In a recent year, there were 132 fuel starvation accidents in GA. That's almost three a week. What a remarkable blemish on a population allegedly trained to a standard and constantly being bombarded via aviation media that fuel starvation is a serious risk. Don't think this number, as a percentage of estimated hours flown, has changed much in decades. Pogo's self-analysis applies; shame on us.

I am very thankful our Grumman came with an engine analyzer that included a fuel totalizer. One additional mitigating strategy if so equipped is to top the tank(s) when refueling and then always bounce the gals burned against the fuel ticket. I notice that my totalizer can sometimes be off ~.5 gals relative to the amount refilled after longer flights, but it's always been on the conservative side so far. The totalizer has occasionally made a 4+ hour flight possible for us, yet still found us landing with 1 hr reserve.

[SportPilot]

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[drseti]

There is really no reason to get low on fuel.

Would that it were that simple! But, the number of fuel starvation accidents Jack cited suggests that telling pilots "don't get low on fuel" is about as effective as telling kids to "just say no."

[SportPilot]

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[Wm.Ince]

. . . "There is really no reason to get low on fuel." . . .

That is not true.
How about an undetected fuel leak and/or a faulty fuel quantity indication system during a particular flight?

Perhaps you really meant to say, "There is really no reason to intentionally get low on fuel."
Now that, I can totally agree with. . . .

[drseti]

I never condoned running out of fuel, and I never said it should be encouraged. What I said is, despite our best efforts at training and education, it's still happening. Fairly frequently. So, instead of simply saying there's no excuse for it, don't you think we should be studying the underlying causes, and trying to mitigate them? The problem is more complicated than simply saying "don't do it." If it were that simple, it wouldn't be happening.

Maybe some of you don't know about, or remember, USS Yorktown's accident. He knew better, and had been sufficiently well trained that he landed when he realized he was low on fuel. That didn't prevent him from taking off again after checking his tanks, when he "thought he could make it."

[Wm.Ince]

I never condoned running out of fuel, and I never said it should be encouraged. What I said is, despite our best efforts at training and education, it's still happening. Fairly frequently. So, instead of simply saying there's no excuse for it, don't you think we should be studying the underlying causes, and trying to mitigate them? The problem is more complicated than simply saying "don't do it." If it were that simple, it wouldn't be happening.

Maybe some of you don't know about, or remember, USS Yorktown's accident. He knew better, and had been sufficiently well trained that he landed when he realized he was low on fuel. That didn't prevent him from taking off again after checking his tanks, when he "thought he could make it."

Paul,

Most of us knew exactly what you meant by your previous post on this.
I concur completely with you.
GA does not have a very good track record on accidents caused by fuel starvation. It happens way too often.
But why?
In my humble opinion, I think a lot of it boils down to just not using good, common, aviator sense. It is stretching things.
Stay within the safe envelope of the airplane and the safe envelope of your own capabilities.
If an error is to be made, I say make it on the side of safety.

[Jack Tyler]

Here's something I find worth considering re: fuel starvation: Is there a technology-based solution to this chronic problem? The FARs only require Part 23 a/c fuel gauges to be accurate when reading 'empty'. What if we slice the GA fuel starvation accidents into two groups, those equipped with fuel totalizers of some kind and those who rely solely on the less accurate gauges? Would aircraft with fuel totalizers have a significantly lower incidence of fuel starvation incidents?

I can't find any data on this so far. (Can anyone else?) But I think commercial aviation illustrates what the answer likely is. Just read through the incidents of fuel starvation, across a wide range of all global aviation incidents and involving aircraft with more capable fuel management systems, in this wikipedia list: http://en.wikipedia.org/wiki/Fuel_starvation

It's probably a fair assumption that fuel starvation is far more about us than our a/c systems or the volume of fuel held by our fuel tanks.

[FastEddieB]

Putting on my dusty pedantic hat here...

Fuel starvation is a term normally reserved for those incidents where usable fuel remained somewhere, but did not make it to the engine for one reason or another.

Fuel exhaustion is when the plane is just plain outta gas. That's the correct term for this discussion thus far.

The former is normally caused by either not fully understanding the fuel system - which in some planes can be quite complicated - or through fatigue or panic forgetting how it works.

The latter is usually the one with all the insidious psychological causes behind it.

I'll venture that in virtually none of the fuel exhaustion accidents would the pilot have described him or her self as the kind of pilot to run out of gas. Ever. In much the same way I would not have described myself as the kind of mechanic to hook a battery up backwards!

[FastEddieB]

To gain some sympathy for how fuel starvation can happen...



Quick - the right engine is feathered due to oil pressure loss and the left just got quiet. The only fuel remaining is about 10 gals in the right wing locker tank. What do you do to get the left engine going again?

I've only had two students fail checkrides.

One was an A&P who maintained the Apache we were using getting befuddled in the oral about proper use of crossfeed.

If you're curious, the other had to do with missing W&B data on the Mooney we intended to use.

[drseti]

I'll venture that in virtually none of the fuel exhaustion accidents would the pilot have described him or her self as the kind of pilot to run out of gas. Ever. In much the same way I would not have described myself as the kind of mechanic to hook a battery up backwards!

Right, Eddie. Just as, during my first marriage, I would not have described myself as a person who would get divorced - ever! All it takes is one moment (or decade) of inattention.

[MrMorden]

I am very conservative with regards to fuel, I very rarely ever land with less than ten gallons (two hours flight time). I just don't want to be "that guy" in an NTSB report.

That said, to get the maximum available utility from an airplane, you have to use all its capabilities, and that includes range and endurance. It seems the FAA has concluded that a 30 minute VFR reserve is a safe amount, and generally that is true. The problem arises when there are unforeseen winds, the destination airport is unavailable, or other variable creep in to eat away that reserve.

30min reserve would be running my airplane down to about 3.5 gallons (2.5 for flying and 0.5 unusable per side). That would be pretty scary for me, and I'd want to have some very detailed information on fuel burns, winds aloft, and other flight information...not to mention a lot of diversion possibilities in case things didn't work out. But for more experienced pilots who want to do the detailed flight planning, the valid reason for getting pretty low on fuel is to maximize use of their airplane. I think the trick is just to be constantly on your game and ready to recognize when the fuel situation is not working out and change the plan.

It's not really something I want to do personally, and with 34 gallon tanks I don't think it would ever come up for me. But for somebody like Fast Eddie with 18 gallon tanks, I'd guess that he'd want to squeeze all the range out of his Sky Arrow that he safely can when he's traveling cross country.

[MrMorden]

Here's something I find worth considering re: fuel starvation: Is there a technology-based solution to this chronic problem? The FARs only require Part 23 a/c fuel gauges to be accurate when reading 'empty'. What if we slice the GA fuel starvation accidents into two groups, those equipped with fuel totalizers of some kind and those who rely solely on the less accurate gauges? Would aircraft with fuel totalizers have a significantly lower incidence of fuel starvation incidents?

Many cars have "seat belt minder" systems, where when you start driving with the driver seat belt disconnected, it chirps at you. There could be designed a similar "fuel minder" system on airplanes (as an optional feature, not an FAA requirement please), such that when a preset fuel level say VFR reserve plus 1 gallon) is reached, a bright cockpit light comes on and a voice in the headset says "low fuel". That light stays on and the voice repeats every 10-30 seconds until the system is reset. Put the reset switch on the *outside* of the airplane or in the engine compartment, so the pilot actually must land to reset it.

If you combine that with a little electronic data event logger that can't be tampered with that logs low fuel events with times and durations (and maybe GPS positions by connecting to the ship's GPS), and you have a nice tattletale system for the FAA. Also, insurance companies might deny any claims on aircraft where the system is activated for more than ten minutes, as evidence of willful fuel starvation.

I'm not saying I would want this on my airplane, but if you are looking for a technological solution...

[MrMorden]

To gain some sympathy for how fuel starvation can happen...

The original Bellanca Viking had this problem, there were five separate relatively small tanks and a very complex two fuel valve arrangement. There were a few accidents where by the time the pilot found the fuel (or gave up looking for it) the emergency was well under way.

[Wm.Ince]

. . . "It's probably a fair assumption that fuel starvation is far more about us than our a/c systems or the volume of fuel held by our fuel tanks." . . .

Could not agree more. Human factors.
What good is a great fuel low warning system if the pilot, for one reason or another, refuses to pay attention to it?
Distractions play a big part in the chain of events leading up to an accident.