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Can You Put Automobile Gas in Your Aircraft?

“Automobile gasoline is not qualified for airplanes.”

Every pupil pilot hears this dire warning about working with car fuel in an aircraft engine that was not licensed for it. These warnings are usually accompanied by a story about engine failure and an unscheduled off-airport landing, which typically takes place shortly just after takeoff.

“If you are traveling devoid of an STC and the feds see you have vehicle fuel in an airplane not certified for it, it is a violation.”

Richard Scarbrough, airframe and powerplant mechanic and aircraft maintenance columnist for Traveling

Even though it is genuine that the use of automobile gas in an airplane can be a tricky business, it is not likely that motor failure will take place so speedily, suggests Richard Scarbrough, an airframe and powerplant mechanic and aircraft maintenance columnist for Traveling

“That’s not to say that the use of vehicle gas could not produce difficulties down the street for the plane,” he says, describing, “100LL provides the motor with lubrication through the guide, which auto gasoline doesn’t.” 

But with the superior rate of avgas, is it value the threat? If it is, how would you do it?

Why Would You Want To?

Vehicle fuel is ordinarily considerably less high-priced than aviation fuel. But, mainly because it normally arrives in at a decrease octane, (80 vs . 87), the consequence will be decrease compression, as engines intended with higher compression ratios generally want larger octane gasoline to keep away from detonation. To mitigate these troubles, lots of pilots operate a combination of 100LL and automobile gas in their plane.

Scarbrough notes that in buy to legally use automobile fuel in an plane, the plane need to have a supplemental variety certificate (STC), which is a sort of style certification issued by the FAA that presents the applicant acceptance to modify an aeronautical solution from its original style and design.

“If you are traveling with out an STC and the feds see you have car fuel in an plane not accredited for it, it is a violation,” he suggests.  

These violations rely on who catches you—it could be as little as “education” on the location or a warning observe or letter of correction, which indicates the corrective motion a pilot must consider in just a specified timeframe.

The STC is received from a provider—a business that specializes in the STC—usually for a handful of hundred pounds.

“Most plane proprietors are happy to spend that for the fuel STC mainly because they will make up the expense of the STC with a person or two fill-ups,” Scarbrough points out.

Plane proprietors who would like to acquire benefit of the STC have to file a Form 337 (important maintenance or alteration) with the FAA and in addition, placard the plane correctly.

Who Has Finished This?

Acquiring an STC can be each time-consuming and high priced, but for some aircraft operators, the need to modify the aircraft arrives out of a sense of requirement. These types of was the case for Petersen Aviation in Minden, Nebraska.

Due to the fact 1983, Petersen Aviation has been providing an auto gas STC for 48 engine styles. In accordance to Todd Petersen, prior to 1983, the family business enterprise sprayed crops utilizing AgCats, and the high cost of 100LL and problem receiving a trusted supply impressed them to glimpse into the idea of operating the plane on auto fuel. They realized they have been not the only pilots going through this dilemma, and the STC enterprise was born.

In accordance to Petersen, the STC procedure necessary them to reveal to the FAA that vehicle gas would not adversely impact either the plane or the engine itself. It is a time-consuming course of action, he notes, including that the FAA sees a lot of programs for STCs each calendar year that are not finished for the sum of analysis and screening and paperwork the applicant has to do.

“To get a supplemental style certificate to run an aircraft on car fuel, you in fact need to have two supplemental form certificates—one for the airplane, the other for the engine,” Petersen suggests.

The tests for the gas STC includes jogging the distinct engine on auto gas and determining if there are any adverse reactions, this sort of as detonation or vapor lock. At times, the aircraft requires alterations to the fuel program, this kind of as unique seals or a unique gas pump, to make the STC feasible.

When an aircraft operator obtains the STC, the airplane gets the 337 type and any areas that are required to make it function, alongside with placards stating that the plane is working on automobile gasoline. 

“These are placards that go on the motor and on the wings [by the fuel cap], and an IA [airframe and powerplant technician with inspection authority] has to install them,” Petersen states. In addition, documentation of the STC is produced in the aircraft’s logbooks by an IA.

As soon as the STC is in spot, the plane can use car fuel, but you ought to be mindful about the variety you pick, Petersen warns. Car gasoline that consists of ethanol—a kind of alcoholic beverages frequently additional to car gasoline to minimize carbon emissions—can have a detrimental outcome on the plane except the engine is made up of ethanol-tolerant elements.

“If the aircraft is crammed with vehicle gas that contains ethanol and the plane just sits, you are setting oneself up for motor failure,” Petersen clarifies. “The seals and gaskets can be harmed when the plane sits previous 10 times. Also, ethanol attracts humidity out of the air and pulls it into the gasoline, so you have to be watchful in a humid setting. The motor may possibly not want to operate.”

Petersen indicates that plane entrepreneurs who want to run auto gasoline lookup for a filling station that doesn’t incorporate ethanol to the merchandise, noting that marinas are often a fantastic alternative for the reason that most boats will not choose ethanol improved fuel either.

Lycoming Engines Take on Car Gas

A person of the frequent fears when employing automobile gasoline in an aircraft engine is that undertaking so might void the manufacturer’s guarantee. Lycoming Engines presents advice on this. 

According to Brandon Dildine, field support complex agent for Lycoming, automotive fuels could be employed in some Lycoming engines provided they meet up with the demands listed in Support Instruction SI1070AB. 

“Use of fuels that do not meet up with the demands detailed in this publication may well result in engine injury or failure and will void the motor guarantee,” Dildine claims. He adds that unapproved fuels containing additives, this sort of as ethanol or oxygenates:

  • might be additional possible to vaporize in gas strains producing a reduction of electrical power
  • may well direct to detonation for the duration of standard procedure
  • are fewer secure and can degrade over small durations of time, resulting in fuel that does not meet its previous technical specs typically ensuing in a varnish buildup in the fuel technique
  • can collect dampness from the air a lot more effortlessly
  • can bring about corrosion of airframe/motor gasoline process components 
  • and can induce degradation of seals, hoses, diaphragms, sealants, bladders used in the airframe/gas system that are not suitable.

Dildine advises persons to seek the advice of the airframe maker prior to working with auto gasoline to confirm that the gasoline permitted for the engine is also suitable with all airframe components.

Dildine even more warns, “All automotive fuels applied must be analyzed to verify that alcoholic beverages is not existing, and a fuel facts sheet need to be acquired from the distributor for the distinct batch to validate that all specs have been satisfied. 

“Due to federal laws and changes in seasonal fuel blends, the formula could modify from batch to batch or could grow to be contaminated all through distribution when transferred in tanks or pipes that had blended gas in them.”