Common Fueling Mistakes and How to Avoid Them

What kind of fuel does an airplane use?

The answer should be simple.

However, in 2009, a Cessna 421C mistakenly refueled with 80 gallons of Jet A fuel instead of 100 L of avgas resulted in a loss of engine power. Unable to return to a runway, the pilot landed the plane in an open field. The plane was severely damaged, the pilot and two passengers received minor injuries.

The National Transportation Safety Board (NTSB) determined the likely cause of the accident as “the failure of airline staff to ensure the aircraft was properly fueled.” Contributing factors to the accident were the Federal Aviation Administration’s (FAA) approval of a supplemental type certificate permitting improper opening of the fuel filler neck and complacency with non-standard refueling practices by landline carrier (FBO) personnel.

As one of about 50 NTSB regional aviation security investigators, it’s Joshua Lindberg’s job to investigate incidents like these.

“One of the things we’re always looking at and trying to track down is the type of fuel being used to make sure it’s the right fuel,” says Lindberg.

The reasons why fuel is misidentified or misfueled vary in most cases, he explains, but when the wrong fuel is used it is almost always a factor in the accident.

“We have many roles and wear many different hats,” he says, “but generally we document accident sites, gather all available pernicious evidence, interview witnesses and take lots of photographs, and then write the final accident report.”

While investigators do many things, Lindberg says the primary goal is accident prevention.

Becoming aware of several refueling-related errors, in part as a result of accident investigations, NTSB issued two misfuelling safety alerts – Line Personnel: Refueling Matters (SA-051) and Pilots: Refueling Errors (SA-050). NTSB also issued a safety alert (SA-079) about diesel exhaust fluid (DEF) and how it was mislabeled or not labeled at all at airports. As a result, it was accidentally added to aircraft.

According to Lindberg, some of the misfueling errors investigators are seeing today include:

• Tankers fitted with the wrong fuel nozzles
• Fuel nozzles are exchanged between trucks
• Aircraft that are not properly signposted or not signposted at all
• Aircraft misidentified by airline staff
• Aircraft equipped with Supplemental Type Certificates (STCs) that allow them to change the aircraft’s engine type, which in turn could change the type of fuel required.

The Cessna 421C fuel filler openings have been modified in accordance with Airworthiness Directive 87-21-02 R1 to prevent the “flattened” Jet-A fuel nozzles from entering the fuel filler openings.

The shield near the main tank’s right fuel cap was worn and illegible.

The final NTSB report for the Cessna 421C accident (CEN09LA145) states: “Two medium-sized single-engine general aviation aircraft based at FBO were modified with turboprop engines requiring Jet-A fuel. According to the supplemental type certificate, the two modified aircraft did not need to modify the fuel filler opening, so the aircraft could be operated with smaller fuel filler openings, which was not in accordance with the certification requirements.

The FBO’s Jet A tanker had the “flattened” nozzle. Line personnel at the FBO discovered that by rotating the Jet A nozzle and spigot at reduced pressure, Jet A fuel could be dispensed without using the adapter. This method became the normal method for the line employees involved to refuel the two modified PA-46 aircraft. The line engineer reported that he mistakenly thought the affected aircraft required Jet-A fuel, even though he had previously refueled that aircraft several times.

Although FBO line personnel had correctly refueled the accident aircraft in the past, the line engineer mistook the aircraft for one of the converted aircraft.

In two other cases, according to Lindberg, the tankers used were equipped with the wrong nozzles.

“What we found in both of those cases was that there were turbine helicopters at those airports, and those turbine helicopters were easier to refuel with the thin 100LL nozzle,” he says. “However, they needed Jet-A fuel, so the line service personnel swapped the jets to make refueling easier, and then never swapped them back or forgot to swap them back. And then when they had to fill another plane, they had the wrong nozzle there. They used the wrong truck. There was nothing that could really help them determine that they misfueled that plane.”

protective measures

Today there are a number of safety precautions that can be taken to prevent misfuelling.

Nozzles for Jet A and 100LL offer different versions. Jet A requires a larger “duckbill” nozzle, while 100LL requires a thin, round nozzle.

According to Lindberg, as long as these are correctly installed on the truck, they are a valuable means of preventing misfuelling.

Both refueling vehicles and aircraft are colour-coded. Black indicates Jet A. Red indicates 100LL.

“When you have black on black and red on red, you know the right nozzle fits the right plane,” he says.

Also, he adds fuel filler opening restrictors on many airplanes that use 100 liter engines, making the fuel filler opening small and very restricted, only fitting the small 100 liter nozzle. Jet A’s larger duckbill nozzle will not fit.

Stickers are another safeguard and should be standard on every plane, Lindberg says.

“If you don’t have a tag near your fuel filler neck, you should definitely add it,” he says. “It’s one of the things that can help service personnel quickly identify the type of fuel, and it only adds to the number of safety precautions we already have in place.”

Who is responsible?

“FAA regulations state that the pilot-in-command is ultimately responsible for the safety of his flight,” explains Lindberg. “However, the aviation industry is all about teamwork and we work towards a common goal of safety and accident prevention, which of course is best for everyone. So in the end, if we all share their responsibilities and work as a team, then the airline industry will be safer.”

Frequent, high-quality training is the best way to avoid refueling mistakes, he says.

“The National Air Transportation Association (NATA) has a very good misfuel prevention program on their website that offers free training and resources. I would highly recommend all liner service employees to complete this either annually or quarterly, whatever is included in their training program. But this is one of those that should definitely be included. And pilots can handle that too. It’s a free program and can help them identify misfuelling issues and collaborate with airline staff as they fuel their planes,” says Lindberg.

“Shortcuts are never good,” he adds. “Being in a hurry is never good and we have seen that this can also contribute to accidents. So we want to make sure we slow down and ask the right questions.”

Lindberg advises that ground handlers always have a conversation with the pilot at any refueling event.

“It’s an opportunity for you to communicate with someone else in the aviation industry. They have similar interests and common goals,” says Lindberg. “Always have a discussion with them because that discussion can raise any questions necessary to ensure the correct fueling is done. This ties directly to the fact that the airline industry is a team effort and everyone has an important role to play. We want to make sure everyone is equally informed and prepared so that everyone appreciates the extent of their responsibilities, including airline staff.”

Finally, he reminds ground service providers never to accept anything.

“You may have seen a certain type of aircraft or a certain type of tanker or whatever the case maybe 100 or 100,000 different times. But that one time you’re interacting with another type of aircraft and think you know exactly what kind of fuel it needs is probably when an accident is going to happen,” warns Lindberg. “So never assume you know the type of aircraft or the type of fuel an aircraft uses. Always ask, always strike up a conversation with the pilot.”