Fuel awareness/management

[drummer4468]

Had a mildly funny encounter this evening which came with some teachable moments for other learning pilots:

Was doing my first dual XC for commercial and having a grand old time. Beat up the pattern at a distant gravel strip for a while and headed back to base. Fuel selector management could have been better but we had plenty of gas in total. The timing between swapping tanks got kinda wonky with the pattern work, so toward the end I elected to stay on the right tank longer than usual to ensure that we remained over the yellow arc on the left when it was time to land, in case of a go-around.

**Note- the yellow arc I refer to is the min fuel level approved for take-off/climb to prevent fuel unporting and the pump sucking in air during acceleration, which may take some time to reach the engine, killing it at a critical moment like 100ft above the end of the runway

As the sun was setting maybe 30mins out from home, the CFI reminded me to keep an eye on the engine gauges since he couldn't see them behind the yoke-mounted iPad. I already was, of course, so I didn't think much of it. The right tank was reading pretty low and I was soon going to switch over anyway during the pre-landing checklist. However, I neglected to relay this internal dialogue to Mr. CFI.

Welp, sure enough, about 10 mins later the big spinny part suddenly went quiet. I was mildly surprised at the sudden-ness of my first actual unplanned power loss, but since I was privy to the conversation in my head, I was already expecting the possibility of the tank running dry(just not that soon, it was still decently above the red line on the gauge). At any rate, I wasn't all too alarmed and simply reached down, only to find the CFI's hand already flying across the cockpit, changing tanks, enriching, turning the boost pump on, etc. Once the giant fan roared back to life and his heart rate came down a bit, I chuckled, apologized and explained to him my reasoning for staying on the one tank so long. He lightly chided me in debrief but understood my rationale.

LEARNING POINTS:
-Never rely completely on your 40-50-year-old fuel gauges. They lie more often than not. This is why we physically/visually check the fuel levels on the ground, and keep track of flight time and fuel burn.

-Of course, I do not advocate intentionally running tanks dry. Like I said, the gauge still read over empty and I had planned to switch shortly, but was spring-loaded to swap if needed. As everyone should be.

-Make it habit to voice all your thoughts/flows/checklists. Whether you're alone, with a CFI, or even with non-pilot passengers. Something I'm constantly working on improving. Never hurts to bounce your thoughts around so everyone's on the same page and may help catch errors. Plus it usually makes you sound super cool to non-pilots.

 

[Clip4]

You were not trained to not rely on fuel gauges?

 

[drummer4468]

You were not trained to not rely on fuel gauges?

Of course. Just thought I'd present a real-world scenario as food-for-thought for others that are still learning and forming their habits. I can see how one can become complacent with the gauge regardless of what they're taught about inaccuracy, just because it's there. Kinda the same way it's hard to fight body signals in IR training, or seeing a known-failed AI showing you false attitudes.

 

[MauleSkinner]

**Note- the yellow arc I refer to is the min fuel level approved for take-off/climb to prevent fuel unporting and the pump sucking in air during acceleration, which may take some time to reach the engine, killing it at a critical moment like 100ft above the end of the runway

Got documentation on that?

reached down, only to find the CFI's hand already flying across the cockpit, changing tanks, enriching, turning the boost pump on, etc.

Your CFI missed a teaching moment if he was doing this rather than instructing.

Never rely completely on your 40-50-year-old fuel gauges.

Or figure out what they’re actually telling you.

 

[bluesky74656]

I always thought that the one certification requirement for fuel gauges was that they show empty when empty.

 

[MauleSkinner]

I always thought that the one certification requirement for fuel gauges was that they show empty when empty.

You get your information from old wives, apparently.

 

[Deelee]

**Note- the yellow arc I refer to is the min fuel level approved for take-off/climb to prevent fuel unporting and the pump sucking in air during acceleration, which may take some time to reach the engine, killing it at a critical moment like 100ft above the end of the runway

In which aircraft were you flying? Honest question. Our Arrow doesn't have any color markings on the fuel gauges and there is no reference to any of this in the POH... So just wondering what kind of aircraft has this yellow arc and minimum fuel required for takeoff

 

[bluesky74656]

In which aircraft were you flying? Honest question. Our Arrow doesn't have any color markings on the fuel gauges and there is no reference to any of this in the POH... So just wondering what kind of aircraft has this yellow arc and minimum fuel required for takeoff

The Bonanza I fly has it.

 

[ateamer]

Were you at low altitude when the engine shut off? If not, the CFI should’ve let you work through it and solve the problem. How experienced a trainer is he?

 

[steingar]

The fuel gauges on my Mooney are for entertainment purposes only. The fuel switch on the Mooney is on the floor directly in front of the pilot. I practically have to give myself fellatio to change tanks. You'd think I'd do it more often.

On a longer trip in the Mooney I start out on the left and burn for an hour. Switch to the right and burn two hours. Switch back to the left. If the flight goes any more than 5 I land and get gas. All this assumes I start full. I try and switch at the top fo the descent. I don't like doing it in the pattern because I have to unlatch the shoulder belt and go head down to change the tank. Don't like to do that in the landing pattern.

 

[AKBill]

I was taught to visually check fuel quaintly and use a watch and average fuel burn for the engine to determine fuel duration. My O-320 burns about 8gph and I use 10gph as the fuel burn. I also switch tanks at regular intervals (30 to 45 min).

Fuel gauges can be inaccurate and I use them with caution. Hopefully they will help detect a leaking fuel system...

 

[WDD]

I know the fuel amount before I leave, the estimated fuel burn rate, and factor in a hour reserve. I don’t think I’ve ever used the fuel gauge.

 

[Will Kumley]

If you struggle remembering to switch tanks there are tricks. I believe you can set a timer in FF, but since I'm too thrifty to purchase FF that isn't an option for me. I tried setting an alarm on my phone which is mounted on the yoke to use Flight Plan go but also discovered I really only look at it when I feel the need to verify something as I'm usually eyes out of the cockpit flying. So now I use my Garmin running watch. As a runner, I use a garmin watch to track my runs and have even used it in flight to track my course, although its old, cheap, and not designed for aviation use so I only get a ground speed and track, not altitude or anything fancy. Its merely used to help me show others where I flew after the fact. However, I have set one of the workouts on the watch to be a 30 minute interval with a 1 minute rest. Now it buzzes/vibrates on my wrist at those times and its a good reminder to switch tanks when I'm in the Cherokee. If I somehow miss the first alert, a second one is only a minute behind it. Of course, now you can buy pilot versions of the garmin watches that do this with a "switch tanks" reminder but again I'm thrifty and as I have a routine that works I see no need to spend 400+ dollars on a watch when that money can go towards aircraft rental. I'm sure any watch with a timer would work but it helps that my watch vibrates as I'm not going to hear a tiny beep from a standard watch alarm when flying.

 

[MauleSkinner]

Fuel gauges can be inaccurate and I use them with caution. Hopefully they will help detect a leaking fuel system...

Fuel gauges can be inaccurate, but are normally precise...when it indicates 1/2 tank in the left wing, it will always be the same amount that’s there. Before the Part 23 rewrite, 23.1337 read:

(b) Fuel quantity indication. There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. An indicator calibrated in appropriate units and clearly marked to indicate those units must be used.

CAR3 had similar verbiage.

Where the common misconception comes in is where the reg continues, again with similar verbiage in CAR3...

In addition:

(1) Each fuel quantity indicator must be calibrated to read “zero” during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply

So while it needs to be precise (Repeatable) everywhere else, it only needs to be accurate (correct) at empty.

 

[Tom-D]

When I bought the Fairchild it did not have fuel gauges. So I had to figure it out.
first flight, I filled the tanks, I flew 2 hours, landed and filled the tanks, I knew than what the fuel Consumption was.

It isn't magic ?

 

[Tom-D]

Any one remember how to dip tanks?

 

[WDD]

Any one remember how to dip tanks?

Who doesn’t measure due with a rod in the preflight ?

 

[Tom-D]

Who doesn’t measure due with a rod in the preflight ?

Then why wouldn't anyone know how much fuel they have?
This isn't rocket science.

 

[WDD]

Then why wouldn't anyone know how much fuel they have?
This isn't rocket science.

I assumed measuring fuel with the measuring rod was as ingrained as buckling your seatbelt or putting the key in the ignition. I guess I had that drilled in me fairy consistently in training.

 

[Tom-D]

I time that I know of, I had an excuse for running out of fuel.
Had topped up both tanks, did the pre-flight as normal. Then started and started to taxi and the did the normal warm up.
then the engine quit, would not start again. I got out and looked to see the gas-co-lator bowl was missing, and was the fuel.
we found the bowl about 20 feet from the start of the taxi.

 

[IK04]

When I was flying my 140 back home after buying it in the nether regions of the Republic, I soon discovered the right fuel gauge always read about 3/4 full and didn't move much with normal fuel sloshing.

I determined that I could use only the left fuel gauge to know my fuel on board. By observing the fuel level on the working gauge for one hour and switching tanks, I knew that after another hour the right tank would have roughly the same level as the left tank. With five hours of usable fuel on board, I could repeat this procedure and know which tank was fullest when landing, since my longest leg was just under four hours...

I have since replaced the gauge with the appropriate propane tank gauge designated in the parts list for my 1946 airplane. Probably the only affordable part on the damn thing, other than the brass fuel drains from Ace Hardware.

 

[drummer4468]

I always thought that the one certification requirement for fuel gauges was that they show empty when empty.

I thought so too, but I also know that the real world doesn't much care what's *supposed* to happen. I guess it may be a wive's tale, unless someone has the regs to back it up. I'm too lazy/busy to google it at the moment.

EDIT:
So maybe i got a little bored and dug this up on the interwebs:


"The often misunderstood portion of the regulation is §23.1337(b)(1) “Each fuel quantity indicator must be calibrated to read “zero” during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined under [Sec. 23.959(a);]” At first glance, it could be read as “it only needs to accurate when it is at zero” but this is not the case. What this portion is trying to clarify is that it needs to read “zero” when the usable fuel is gone even though there may still be “unusable” fuel in the system. It is not saying that is the only time it needs to be accurate.

If we go back to the stem of §23.1337(b), it says, “(b) Fuel quantity indicator. There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. An indicator calibrated in appropriate units and clearly marked to indicate those units must be used. In addition—” This seems pretty clear if you don’t skip over it. The indicating system needs to provide an accurate indication to the pilots during flight of how much usable fuel is left in the tanks at all times. There is no specification as to how accurate but it needs to provide an accurate indication."

In which aircraft were you flying? Honest question. Our Arrow doesn't have any color markings on the fuel gauges and there is no reference to any of this in the POH... So just wondering what kind of aircraft has this yellow arc and minimum fuel required for takeoff

Beech Sundowner, it's in the POH. It's all about how the tanks are designed/shaped and where the fuel wants to sit in relation to unbalanced outside forces that exist in takeoff or go-around acceleration. In fact, IIRC i think slips may be cautioned against as well. I'll have to double-check that now, thanks for making me think of it.

EDIT: Just looked it up, POH does limit slips to 30 seconds. Though I can't imagine ever having to slip that long at once. These things come down like elevators with the power off.

Were you at low altitude when the engine shut off? If not, the CFI should’ve let you work through it and solve the problem. How experienced a trainer is he?

Plenty high, we were near the end of the cruise at 4500. He actually self-critiqued the same sentiment afterward, saying he should have let me figure it out. I can understand the knee-jerk reaction though, being that it was getting pretty dark and he deals with plenty of brand-new private students who freak out and/or freeze over things like that. That's why part of me found it funny, because I already knew the situation and was totally calm about it. He was just quicker to reach over, so I stayed out of the way instead of arm-wrestling around. Bumping heads hurts when you both reach for the fuel lever in the middle lol.


I appreciate all the input. Just to reiterate, I wasn't relying on the gauges, I knew how much fuel we had on board. I didn't intentionally run the tank dry but I knew it was low; we had plenty of gas in the other in case it did, so I was comfortable holding off the swap until descent to maintain a safety margin above the yellow arc for the upcoming landing.

And yes, my management was lacking a bit amidst some unplanned detours in the flight. Could have set myself up a little better before it happened. By the time Overall it was a non-issue, and I'm just sharing because I like learning from others' perspectives and experiences. Maybe it'll help someone else, or at least share my sensible chuckle. lol.

 

[drummer4468]

If you struggle remembering to switch tanks there are tricks. I believe you can set a timer in FF, but since I'm too thrifty to purchase FF that isn't an option for me. I tried setting an alarm on my phone which is mounted on the yoke to use Flight Plan go but also discovered I really only look at it when I feel the need to verify something as I'm usually eyes out of the cockpit flying. So now I use my Garmin running watch. As a runner, I use a garmin watch to track my runs and have even used it in flight to track my course, although its old, cheap, and not designed for aviation use so I only get a ground speed and track, not altitude or anything fancy. Its merely used to help me show others where I flew after the fact. However, I have set one of the workouts on the watch to be a 30 minute interval with a 1 minute rest. Now it buzzes/vibrates on my wrist at those times and its a good reminder to switch tanks when I'm in the Cherokee. If I somehow miss the first alert, a second one is only a minute behind it. Of course, now you can buy pilot versions of the garmin watches that do this with a "switch tanks" reminder but again I'm thrifty and as I have a routine that works I see no need to spend 400+ dollars on a watch when that money can go towards aircraft rental. I'm sure any watch with a timer would work but it helps that my watch vibrates as I'm not going to hear a tiny beep from a standard watch alarm when flying.

Thanks for the insight, that'd be a nifty trick to set up my FitBit for 30 minute "workouts". I'll have to try it sometime. One trick I use is on the first half of the hour I'm on the right tank, second half I'm on the left tank. Works well as a rule of thumb, especially if you have an analog watch or clock in the panel; the minute hand points to the tank you need to be on. Same idea if whatever I happen to be renting has a fancy flight timer in the transponder, i'll glance at that and change as necessary.

I think overall what happened on this particular flight, was we diverted to a different field nearby and did a few surprise laps to brush up on short/soft field ops. After all that fun and unplanned distraction was done and we were happily cruising back home, I got a little too lax with the timing and ended up in the awkward spot that I did.

 

[AKBill]

@drummer4468 consider joining Beech Areo Club (BAC) if you will be flying the Sundowner for any length of time