The commercial pilot stated that, during the preflight inspection of the helicopter before the agricultural flight, there were about 23 gallons of fuel onboard, which he determined was sufficient to complete the 45- to 60-minute flight to his destination.
He added that, before departure, the helicopter fuel gauge indicated “close” to 3/4 full. Based on the helicopter’s total fuel capacity (41 gallons), a 3/4-fuel quantity indication would have equated to about 30 gallons.
About 50 minutes into the flight and seven miles from the destination airport, the engine lost power.
The pilot performed an autorotation to a field near Le Sueur, Minnesota. The helicopter hit terrain and sustained substantial damage. The pilot sustained injuries in the crash.
During a post-accident examination of the helicopter, no usable fuel was found. However, the fuel gauge indicated a little over a 1/4 tank of fuel remaining.
The examination revealed that the fuel transmitter’s resistive element was corroded. The fuel transmitter was tested, and the resistive values were uncorrelated to the transmitter’s float position.
A new fuel transmitter was tested, and the resistive values corresponded to the float position.
Although the fuel gauge was indicating that a sufficient amount of fuel was onboard for the flight, the pilot should have visually checked the fuel quantity in the tanks before takeoff to ensure that a sufficient amount of fuel was onboard for the flight, which he did not do.
His improper preflight fuel planning and his dependence on erroneous fuel gauges led to the subsequent fuel exhaustion and total loss of engine power.
Probable cause: The pilot’s inadequate preflight and in-flight fuel planning, during which he did not visually check the fuel quantity in the fuel tanks and instead relied on the fuel gauges that were showing erroneous fuel quantity indications, which resulted in fuel exhaustion and the subsequent loss of engine power during cruise flight.
NTSB Identification: CEN18LA300
This July 2018 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Any pilot who goes flying without a visual check of fuel on board should lose their license.
Every time fuel is added to a tank represents an opportunity to evaluate the accuracy of the fuel gauge (does the gauge reading change in accordance with the number of gallons added).
Why do we even have fuel gauges if they are so unreliable? Cary said it right. You have to stick the tank unless you can see the that the tank is full.
Fuel gauges are required equipment, per FAR 91.205. But they are only required to be accurate at ’empty’ , no usable fuel.
This young guy had 4+ hours in this modified 1947 Bell helicopter. It looks like it’s difficult to look into the tanks, mounted high behind the cockpit.
He also had a problem with the rotor tach sender…
It appears to be poor maintenance on an old aircraft.
What I find interesting about of these pointless cases of fuel exhaustion is that someone will always pipe in with a comment about Sticking The Tanks. I have a lot of hours in a variety of GA aircraft (rented) and I have yet to see one that had any “stick” to use or any guidance in a pilots manual on how to translate any stick readings into an actual quantity I guess you could look around for an old broom stick handle and then make a SWAG based on how much got wet.
Other that then the usual looking into the filler opening and making a guesstimate of fuel onboard (if not full) is about the best that anyone could do. As others brought up the Bell 47’s tanks are not in the most accessible location give they were going for a gravity feed system. I will add that Piper had a good idea of putting a metal tab inside the tank that represented a known level for a partial tank.
Just as an aside the big airliners do have a “Dipstick” system built into the tanks so that a malfunction indication system does not ground them. Of course the pilot has to correctly interpret the data that is presented to get the accurate level and a bit of a math fiasco resulted in a Boeing 767 doing a dead stick landing at one time.
Sarah:
For the Cessna 172’s and Piper’s I’ve flown, I always had a glass/plastic tube that had gallons printed on the side, which showed how many gallons were in the tank being measured. You just put it in the tank, put your thumb on the top, remove the tube and presto – it showed how many gallons were in that tank.
You can make your own stick, or I have also used an acrylic tube. The idea is to lower it into the tank until it bottoms out, put your thumb over the end, then remove it. The fuel will remain inside the tube until you release your thumb, and will show the level very clearly. I’ve used both – a simple wooden stick is easy, cheap, and foolproof.
Sarah:
Thanks for your thought provoking comment.
In my experience three bits of information are a must to avoid fuel exhaustion: How much fuel is in the every tank before each and every flight, the ins/outs/and cautions for managing your fuel system the aircraft you are currently flying; and how much fuel is actually burned per unit time. It goes without saying that poor aircraft maintenance, as was the case with this accident, adds a serious element of the unknown.
The pilot estimated he had fuel for 45-50 minutes, and then flew a mission that exceeded his estimate’s upper limit. Ooops. His bad. Where was his reasonable reserve?
IMHO, we should also ask if the accident aircraft was airworthy. Two questions must be answered “yes”: (1) Does the aircraft meet it’s TCDS and all ICAW requirements of any STCs/ADs etc? The answer was “NO” since the fuel gauge was inop due to inadequate maintenance. (2) Was the aircraft safe to fly? Evidently not since the fuel gauge was inop (it didn’t accurately display ’empty’). Poor maintenance is a wild card. He must have really needed the job.
I encourage you to get with a CFI or mechanic to discuss the most accurate ways to measure fuel in the tanks for the aircraft you fly. FWIW, a calibrated dipstick (more than one may be needed if your aircraft has tanks of different capacities) is hands down the least error prone method of determining your pre-sortie fuel for each and every tank. It’s low tech,, and if calibrated (a must for any instrument) consistently very accurate. Even the best fuel totalizer can lead us astray. Redundancy occurs when we dip tanks, keep close track of time, and very conservatively estimate fuel burn (i.e. over estimate by about 20%).
Transport category aircraft may have multiple redundancies that afford their pilots considerable opportunities to trap errors. In addition to the aircraft system redundancies and multi-pilot crews, Dispatchers provide significant back up to catch errors. Could be that’s why the accident rate of even the worst airlines in the world is still lower than the GA single pilot accident rate in the US. In the case you mentioned of the 1983 Gimli Glider fuel exhaustion mishap, all those error traps failed. A new requirement to convert gallons to liters was the underlying root cause. About 18 years later an A330 suffered the same problem while over the the Atlantic. This time due to a maintenance error. In any case, comparing the mishaps of the sole pilot of a GA aircraft to a crewed aircraft isn’t of much value.
Well, one good reason might be for redundancy; if the gauge(s) is going down faster than your clock is ticking off the minutes it’s time to land ASAP. Whether it’s the gauge or fuel siphoning/leaking , the ground is a better place to find out than the air.
It’s often said that how you train is how you’ll fly—in other words, those things learned waaaaaay back in primary training carry forward well into the future. But few of us were trained about flying with less than full tanks. Most of us were trained to check that the tanks were full before we started each lesson, or before we left for our cross country flights. So few of us were trained early on to stick the tanks and determine that a partial load of fuel is adequate for the intended flight. Can this be the not so subtle reason for the plethora of fuel exhaustion events which regularly occur every year, inadequate fuel planning training? Just a thought.
Full fuel before each flight? To do that you have to fill them before or after each flight and have control of the aircraft so you know no one has flown it since fueling. Such a practice in not common in training or subsequent flying. Checking fuel is a requirement regardless of when you get fuel. Even if you own the plane you need to sump check before each flight and while doing that visually check fuel even if you think the tanks are full.