Well, yes and no. Most aircraft engine exhaust valves are a nickel-based super alloy known as Nimonic 80A. The metallurgical composition is about 76% nickel, 19.5% chromium and a small amount of aluminum, titanium and other ingredients. The titanium amounts to less than 2.5% of the total, which is there for some minor performance enhancements, but the main nickel and chromium give it the heat resistance necessary for operating at the extreme temperatures when the valve first opens. With aircraft engines, the main concern is not the valves, but the valve seats. Unlike car engines that are historically cast iron, the aluminum cylinders on airplane engines have always had some level of hardened valve seats to allow the cylinders to stand up to the stress of the valves opening and closing. Despite the myth about the lead in TEL acting as a valve lubricant, it actually causes problems in the form of deposits on the valve stems that eventually result in stuck valves. For a good description of the unleaded fuel issue and its effect on valves, I suggest you view Paul Bertorelli’s good video on the subject (Whadayamean Unleaded Fuel Will Trash My Valves?).
You are still ignoring the fact that the lower number of high performance engines still use the majority of aircraft fuels and provide most of the revenue to commercial operators. Asking them to derate their engines so that you can run a lower octane fuel (in spite of the fact that your engines will run on their high octane fuel) is like asking you to stop driving your gasoline powered car to give more room for diesel trucks on the road. Derating high performance engines would be incredibly expensive and could actually render the aircraft unfit for its original purpose. The FAA’s pronouncement of approving engines to use 91UL is creating another can of worms - mainly because it gets back into the argument of whether an FBO should have two separate pumps for Avgas, in addition to many that also dispense Jet A. We have enough problems with misfueling incidents between 100LL and Jet A. Dispensing two grades of Avgas creates another misfueling potential and exposes the FBO to the expense of operating the two grades along with the liability for fueling with the wrong grade.
Clarity will come later. But a big part of the problem is that it’s not 1970 when one could stick in any old tank, put on a pump and call it a fuel farm. Not only does it now have to meet many more safety requirements than before (good), it usually has to have a credit card payment system attached. Hence a $3k installation becomes a $30k (or more) installation. Hence, most small airports can’t easily afford two fuel choices. From a return on investment standpoint, without subsidies, the at the pump price required for a single 100UL installation might well be less than what one would have to charge for a new 9xUL choice from a second added station, even if the $/gallon is inherently lower. And adding a second truck run from the distributor isn’t free either.
It should be an all or nothing approach on fuel IMO, for the small engines that are already approved for mogas this new fuel is moot and only going to drive up the price of 100LL, lets base the rules on helping the consumer and not a destructive political socialist agenda that benefits no one.
No, I said just dump, 100 octane. No two grades. All these aircraft engines could be modified without degrading their power outputs. Most turbo charge airplanes would just need to add inner coolers or larger inner coolers to handle the new 94 UL as the only fuel available.
Most turbo charged piston engines only have compression ratios of 7.5 to 1. The big myth, is that these are high compression engines and have to use 100 octane fuel.
For the last 30 years of politics and funding cycles, we could have fully funded 91UL as an airport improvement. Lord knows it would have been the least expensive airport improvement program ever.
If it’s such a great idea, Arthur, start putting in pumps and raking in the bucks.
I’m not sure I agree with your solution to subsidize the inventors with money confiscated from all of the taxpayers instead of just the ones that actually benefit from the fuel. Why not just let the inventors license their formulas to the big producers (assuming that they still have any enforceable patents to lean on), like other patent holders do with basically everything else?
My concern is that we have airports that struggle to keep up with emails, much less making sure they note somewhere available in EFB’s and in online planning tools what type of fuel is available. My Turbo Saratoga will be part of that one-third NOT allowed to use 91UL. I have an intercooler (it is NOT an inner cooler - sorry, pet peeve) and I don’t plan on “trying” lower octane fuel and going up to 15,000 feet and just “screw around and see” if detonation occurs. For those guys content at flying at 3,000 feet all day long and never flying more than 100 miles from home, this is probably not that big of a deal. For those of us whose typical missions has us flying 10,000 feet or higher, in the mountains, and loaded for real traveling, the risk of not being able to find 100LL or 100 octane equivalent is a real concern.
So how is this fuel issue affecting the so-called (real or otherwise) pilot shortage? Does the algorithm used to come up with the 70%-of-the-fuel-is-burned-by-30%-of-the-fleet consider that pilot training is done in the 30% category. Imagine the cost of you PPL if it was done in a hot twin?
Wouldn’t help said pilot shortage
“Most turbo charged piston engines only have compression ratios of 7.5 to 1. The big myth, is that these are high compression engines and have to use 100 octane fuel.”
That’s because the turbocharger is compressing the air before it even gets in the cylinder. The result is even greater peak pressure and power (and chance for detonation).
The piston/cylinder compression ratio may be low, but the overall compression ratio (turbo+piston/cylinder) is even higher.
Which is the whole point of turbocharging an engine.
You need to learn a bit more about engine design, changing the induction tract, and dealing with the FAA on mods. Short answer: cannot be done.
That’s absolutely not true they’ve already done it.
I’m not sure what your logic is here. If an FBO and flight school share the same owner, or are even the same business entity, you’d think they would put in the second fuel for their old 172’s if it saved money.
They don’t, so I suggest it’s likely not worth it. I could be wrong, but if you ever do the calculations on fuel cost as a portion of TOTAL operating cost including depreciation, and actual repairs, you’ll see why so many people who didn’t need body on frame trucks kept buying them despite fuel price spikes. You gotta be on the extreme far end of the mileage chart before fuel costs really matter. One reason I’ve been suggesting forever to dump all the stupid mandates and greatly raise fuel taxes so the market will favor efficiency.
If the FAA does what is proposed, and you have an engine listed on Lycoming SI 1070AB as able to run on UL91, you will not need an STC. UL91 and UL94 are ASTM D7547 spec fuels. They are not “mogas” or automobile ASTM D4814 fuels which require an STC. Swiftfuel UL94 does not require an STC for grade 80 aircraft and engines. CURRENTLY, Aircraft whose minimum approved fuel grade is listed as Grade 100LL, Grade 100/130, or Grade 91/96 CANNOT USE Swift Fuels’ Unleaded UL94 Avgas without purchasing an appropriate Supplemental Type Certificate. This is crazy as the EU has allowed UL91 for more than 10 years in aircraft with engines on the Lycoming SI 1070 list. In the USA the AIRFRAME needed to be approved as well. Not so in Europe.
color is clear or yellow. So far, it does not smell at all like mogas.
What is needed is Water Methanol Injection…
Open your mind… https://www.jstor.org/stable/44548241
12 octane points on top of 94 = 106. + the latent heat of vaporization allows for LEAN BEST POWER mixture. This was known and done by airlines in the late 40’s. They were running 74 octane fuel in supercharged radials, successfully.
UL91 is AVGAS not Mogas. Same ASTM spec. see SAIB Number: HQ-16-05R1
The FAA should install one self serve UL94 tank and pump at every federally funded airport. The cost should be shared between the FAA and the EPA for being complete failures. This pump should have short term transient tie downs, and through the fence access. This will help with the pilot shortage and improve safety. I can fly for an hour for less money than it costs to take a piss at Signature.
Oh, goody. Now we’re back to two fuels, 91UL for “the 68%” and some version of 100 for the rest of us? After 50 years of airports having one supply tank, airports are gonna need two tanks?
(For folks thinking installing a second tank is just an “FAA thing,” they have no idea what kind of effort it is to install a second tank - funding calisthenics, engineering work, dedicating ramp the space, installing the tank and bump protection, adding second pump, getting the spotted owl EPA approval, obtaining fire safety certification. Even installing a small second system is upwards of $350,000 that your tax dollars or inflation get to pay for. And last but not least, the airport gets to bankroll an additional $30,000 of fuel inventory. Fun.)