100LL Banned at Reid-Hillview & San Martin- Santa Clara County

We all know that leaded aviation fuel’s days are numbered. Steps are already underway to market a recently formulated replacement for 100LL Avgas. But, it seems that’s just not quick enough for Santa Clara County, California. Other airport sponsors in California may be taking similar steps. We sure hope the FAA steps up to the plate to deal with this issue. Please take a moment to read this great article about this by Mike Busch

100LL Crisis in California

by Mike Busch A&P/IA CFI-A/I/ME

The powers-that-be in Santa Clara County, California, have decreed that leaded avgas will no longer be available after December 31, 2021 at two busy airports that the County controls: Reid-Hillview Airport (KRHV) in San Jose and San Martin Airport (E16) 18 miles to the southeast. Starting on January 1, 2022, only unleaded avgas will be allowed to be sold at those two airports, and at present the only unleaded avgas available is 94UL.

Pleas by AOPA and the FAA for the County to delay this ban on leaded avgas until a viable 100-octane unleaded substitute fuel is available have fallen on deaf ears. Legal and regulatory challenges to the County’s precipitous action appear to have gone nowhere. The experts I’ve spoken with who have been following the situation in Santa Clara County most closely have all told me the same thing: This is almost certainly going to happen.

If only these two airports were affected, it would be bad enough. But none of the experts I’ve spoken with expect things to stop there. There are already indications that Santa Monica Airport (KSMO) in Southern California may cease selling leaded avgas soon. There are also rumors about similar bans coming at California airports from Watsonville (KWVI) in Northern California to Gillespie Field (KSEE) in San Diego.

If the dominoes start falling, it’s unlikely that this will remain confined to California for long. All owners and pilots of piston aircraft need to be concerned.

Getting rid of lead

I’m hardly an environmental activist, but I’ve been an outspoken proponent of unleaded avgas for many years— for reasons having nothing to do with the environment. Tetraethyl lead (TEL) is a great octane booster, but everything else about it is terrible for our engines. It is the principal cause of the scaly combustion chamber deposits that lead to stuck valves (especially in Lycoming engines), and the principal cause of sludge that contaminates oil control rings and leads to high oil consumption and low compression (especially in Continental engines). It’s also extremely toxic, and it is only manufactured in one plant located in the U.K. so the supply chain for TEL is highly tenuous.

A good illustration of the evils of TEL can be found in the Rotax Line Maintenance Manual, which calls for the use of synthetic oil and an oil change interval of 100 hours provided the engine is operated on unleaded mogas. However, the manual prohibits using synthetic oil if the engine is operated on 100LL more than 30% of the time, and cuts the oil change interval in half to 50 hours. Also, the gearbox inspection interval is reduced by half if the engine is operated on 100LL.

I firmly believe that the sooner we can move from 100LL to unleaded avgas, the better it will be for our engines. But, the unleaded avgas needs to be suitable for our engines.

Is 94UL suitable?

At present, the only approved unleaded avgas available in meaningful quantities is 94UL. This may or may not be a suitable fuel for your piston aircraft engine, depending on what kind of engine you have. Low-compression engines that were originally certified for use with 80/87 or 91-octane avgas (both long unavailable) should do just fine on 94UL. 

However, 94 UL is not suitable for high-compression or turbocharged engines that were certified for use with 100-octane avgas. For one thing, it is not legal to operate them on fuel with an octane rating lower than 100—this is an operating limitation for which compliance is mandated by FAR 91.9(a). Legalities aside, operating these engines on 94-octane fuel does not provide sufficient detonation margin when operating at high power (especially takeoff power). You might get away with it on a cold day, but the engine might experience destructive detonation on a warm day. So, operating on a non-conforming fuel is not just illegal, it’s also irresponsible and dangerous.

How can you tell whether or not UL94 is suitable for your engine? There are several ways. The minimum octane requirement should be prescribed in the operating limitations section of your POH or AFM. In addition, this information should be placarded at each fuel filler port of the aircraft. Also, you can pull up the Type Certificate Data Sheet for your engine and find the compression ratio and minimum octane requirement there.

If your airplane is powered by a Lycoming engine, Lycoming has a lovely service bulletin—Service Instruction 1070AB—that sets forth all the approved fuels for every Lycoming engine model. If you look at Table 3 of this service bulletin, you’ll see that lots of Lycoming engine models are approved for use with 94UL, while lots of other engine models are not. For instance, the Lycoming IO-360-B, -E, -L, -M, -N and -P are approved to run on 94UL, but the IO-360-A, -C, -D, -F, -J and -K are not. A similar situation exists for the other Lycoming engine families—O-320, IO-320, O-360, TIO-360, O-540, IO-540, TIO-540, etc. Some are approved for 94UL, some aren’t. You need to look up your particular engine model variant to know which category it falls into.

What about 100UL?

Creating a viable unleaded 100-octane fuel has been a much tougher task than either the industry or the FAA anticipated. The joint FAA/industry Piston Aviation Fuel Initiative (PAFI) program has been working to qualify one or more suitable fuels since 2013, and after 8½ years still has nothing to show for it other than various unsuccessful candidates that were sent back to the drawing board.

At present, the only approved 100UL fuel is the one formulated by General Aviation Modifications Inc. (GAMI) in Ada, Oklahoma known as “G100UL.” The FAA has granted STCs for this fuel to be used in a wide range of low-compression engines, with extension of the Approved Model List (AML) to high-compression and turbocharged engines expected in 2022.

George Braly of GAMI, developer of G100UL

Getting FAA approval of a fuel is one thing, but actually deploying it to airports is quite another. I spoke to GAMI’s George Braly who told me that his company was working hard with refiners, blenders and distributors on the logistics of getting serious quantities of G100UL produced and distributed, but that realistically this won’t happen before “late summer of 2022.” I interpreted this as a best-case projection, and I’ve heard other experts say that it could be 18 months before 100UL is reliably available.

In the meantime

More than half of the piston GA fleet have low-compression engines that will do fine on 94UL. If you’re flying one of these, you probably don’t need to worry too much about this period of fuel supply instability. But, the portion of the fleet powered by high-compression or turbocharged engines represent 75% of the avgas consumption. If you’re flying one of these, you definitely need to worry because 94UL is simply not suitable (or legal) for use in your aircraft.

Pilots of these higher-performance aircraft will need to be vigilant about which airports have 100-octane avgas and which don’t. If you’re flying into an airport where availability of suitable fuel is uncertain, you’ll need to be careful to tanker in enough fuel to get back out and fly to another airport where suitable fuel is available.

Ah, but what if you fly to an airport where you expect 100LL to be available and discover to your shock that it isn’t? What if only a non-conforming fuel like 94UL or unleaded 91-octane mogas is available? What if you don’t have enough 100LL left in your tanks to fly to another airport where 100LL is available? In short, what if you find yourself painted into a corner?

Well, legally you’re stuck. You’d probably need to find someone willing to haul a bunch of 5-gallon jugs of 100LL to you, preferably in the dead of night when nobody could spot you pouring the banned fuel into your airplane so you could make your escape.

Putting legalities aside, if you’re tempted to fuel your bird with 94UL or 91UL despite the fact that it requires 100-octane avgas—and please understand that I’m certainly not recommending you ever do this—I will offer you a couple of suggestions for minimizing the likelihood of subjecting your engine to destructive detonation.

First, segregate the substandard fuel into one tank while keeping unpolluted 100LL in another tank. Use the 100LL tank for takeoff, climb, go-around, missed-approach, and all other max-power operations, and switch to the tank containing substandard fuel only for reduced-power cruise, descent, and other low-power operations where detonation is unlikely.

Second, don’t try to use substandard fuel unless your aircraft is equipped with an engine monitor with a CHT probe on each cylinder and a user-programmable alarm that you can set to go off at 400°F for Continentals and 420°F for Lycomings. If you get a high-CHT alarm while operating on substandard fuel, you need to reduce power IMMEDIATELY. A runaway CHT can cause a piston to melt (or worse) in just one or two minutes if the pilot fails to take immediate action to halt the thermal runaway.

I offer these tips strictly for emergencies. Please don’t allow yourself to get into a situation where you’re tempted to fuel your aircraft with substandard fuel that doesn’t meet the minimum octane requirement of your engine. My purpose in sending you this alert is to heighten your awareness that conforming fuel may not be available at certain airports during the coming year, and to encourage you to do the necessary due diligence and flight planning to avoid getting into a situation where you require fuel that is unavailable. It appears that we are entering a period of time that may be less than friendly to piston GA. Be careful out there.

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