This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
I preflighted the Cessna 172 for a three-hour flight in the pattern at ZZZ. Fuel was visually checked and lined up with what was seen on the gauges at 75% (15 gallons a side).
After about three hours of pattern work the engine started sputtering on base to final. Carb heat was checked and was on, with full flaps. Fuel also was checked and was at five gallons a side.
After switching to the right tank, which did not help, the focus was getting the plane on the ground in a safe manner.
Three to five seconds from landing, the engine shut down and I was able to land the aircraft about five feet short of the runway. After landing, there was no visible sign of damage to either the airfield, plane, or myself.
The fuel was checked again and showed empty, in direct contradiction to what was shown earlier and later in the maintenance hangar (Full) on the fuel gauges.
Airport Ops and maintenance were then able to tow the aircraft back to the ramp for inspection.
Cause: Faulty reading of fuel gauges. Suggestions: Fixed fuel gauges and not trusting the C172 fuel gauges.
Primary Problem: Aircraft
ACN: 2191917
When you click on the link it will take you to the ASRS Online Database. Click on Report Number and put the ACN in the search box, then click Search. On that page, click on “view only the 1 most recent report.”
consv estimate = 9 gallons per hr = 27 gallons not sure where math was on this one…. pilot error 100%. maybe add another 1 gal per hour because of pattern work
Another issue here is, take offs & going around, uses more fuel than one does at cruise. So 3 hours of pattern work is going to have you at full throttle about every 10 minutes up to pattern altitude, and also depending on how much traffic is in the pattern….
This means one will use more fuel than if one had been at cruise on X/C. So one has to remember that this is a higher fuel use activity than normal.
It might be advisable to take a break from pattern work after an hour and check the fuel during that break.
It is interesting how each upcoming generation has to learn what every generation previously has already learned: Light airplane fuel gauges are notoriously untrustworthy. One must mechanically determine one’s level of fuel in order to be accurate. My generation learned that in the late 1960s. Nothing has changed.
I have never ONCE done a preflight that didn’t include a visual check of the wing tanks, regardless of the inconvenience of the Cessna wing.
“At XA30 on Day 0, I preflighted Aircraft X (C172) for a three hour flight in the pattern at ZZZ. Fuel was visually checked and lined up with what was seen on the gauges at 75% (15 gallons a side).”
Not sure what year/model Cessna 172 this is, but 75% fuel capacity certainly is not 15 gallons per tank!
The standard fuel tanks on earlier Cessna 172s is 39 gallons, 36 usable.
So 75% of 19.5 is about 15 gal.
The gauges should read accurately near empty, but not at other levels.
Either fill the tanks to full or stick the tanks to see how much fuel there actually is.
19.5 gallons per side.
And there are 30 gal tanks also on some. Iirc.
There was an option on some models for the ‘long range’ tanks, like I have, which are 52 gallons, 26 per side.
They were usually with a higher HP engine, like the TCM, IO-360.
My question is why do both gauges have the same inaccurate reading?
It may be that both fuel sending units wer replaced and not calibrated…ie, bend the float wire until an ’empty’ reading is actually empty.
Other levels depend on the length of the float arm, which is not adjustable on a Cessna unit, [ without making multiple bends in the arm if it’s too long.]
3-5 seconds from landing and he didn’t make the runway….yet another reason not to aim for the numbers, along with gust protection, etc….unless you are operating on a short runway, of course.
Agree. And if there is an engine problem, the first requirement at lower altitude with questionable gliding distance is to head directly to the runway – the shortest possible ground track. This pilot first did trouble shooting (carb heat, switched tanks (how long did he wait for restart)), apparently didn’t raise the flaps, and still almost made the runway. Had he gone straight to the runway first, seems like he could have easily made it with a lot of room to spare.
I always say , ” If I make it to the downwind I will also make it to the runway.”
Per the FARs, the only time that fuel gauges are required to be accurate is when the tanks are empty.
Most modern general aviation aircraft have been certificated by the FAA in accordance with 14 CFR Part 23. The following pertains to the fuel gauges:
23.1337 Power plant instruments installation.
23.1337(b) Fuel quantity indication. There must be a means to indicate to the flight crew 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…
A gauge that reads zero when the tank is still 1/ 3 full does not meet this requirement. This regulation goes on to say:
23.1337(b)(1) In addition… 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…
The purpose of 23.1337(b)(1) is to reiterate that the gauge is supposed to indicate usable fuel, not total fuel. The main requirement is to indicate to the flight crew the quantity of usable fuel. This requirement is plainly “in addition” to the basic requirement, not instead of it.
Also FAR 91.205b (9) Fuel gauge indicating the quantity of fuel in each tank.
Every time you fuel the plane you should be able to say how much fuel it will take within 2 gallons! Using fuel gages, fuel flow totalizer, average burn per hour. There is no excuse for running out of gas! None! Run out of gas you have no business being a pilot.
Three hours of pattern work…perhaps
the pilot is a student, or as Biden’s FAA renamed them, a ‘learner’. This learner just learned a valuable lessons, which one would doubt will be repeated.
I’d bet you made a mistake or three as you advanced from ‘learner’ to your current status as a certificated aviator.
Nope. Commercial Pilot with 800 hrs TT.
But…aren’t we all still learners?