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81

Jet-A (and all turbine fuels) are far cheaper than 100LL (at least in bulk; retail prices vary due to local supply and demand as well as different regional tax regimes on aviation fuel) for several reasons. Scale Southwest Airlines alone burned through 1.9 billion gallons of Jet-A in 2015, dwarfing the mere 175 million gallons of 100LL that the entire US ...


32

The LL of 100LL stands for Low Lead as it has tetra-ethyl lead added as a detonation inhibitor for high-performance engines. Despite the "low" moniker there actually is a lot of it in there, and it's toxic. This fuel is expensive for a number of reasons: The lead itself is expensive The lead additive means that a refinery must shut down and clean the lead ...


31

There are a number of factors that go into it: Economies of Scale Jet-A is used in a much higher volume than 100LL. All the jet engine commercial aircraft each day burn through orders of magnitude more Jet-A than piston aircraft burn through 100LL. That means that there is a much higher production volume, and therefore a cost savings as a result. Buying ...


23

Your question is based on an incomplete picture of how aircraft work, I'm afraid. As a passenger on any major airline, the only lead you are likely to encounter is in the shielding on the security x-ray machines. Fact: leaded fuel is relatively uncommon First, tetraethyl lead is only present in what we call avgas - it is most often sold these days as ...


16

You could fly gliders. They don't use leaded fuel. In fact, they don't use fuel at all.


10

The distillation and refining process for 100LL is more expensive than the process for 91 unleaded. 100LL has a high octane index, and is treated to be less volatile (in particular at high altitudes). 100LL is also perfectly dry in order to prevent icing. Also, 100LL is produced in smaller quantities than car fuel, so economies of scale are also a factor. ...


9

The modifications required are just not economically viable. The main issue is vapor lock, because ethanol has a lower vapor pressure (i.e. more likely to vaporize) than gasoline. Worse, mogas ethanol levels are varied to achieve ideal vapor pressure for different temperatures. This is fine for cars that go through a tank of gas every week or two, over a ...


9

ExxonMobil China says their Avgas 100LL will not freeze above -58°C. The 'typical' freezing temperature is not given, but I would expect we'd be more interested in the maximum freezing temperature.


8

J. Hougaard's answer is a bit of a smart @ss but it is one way to fly without using leaded fuel minus whatever is burned in the engine of the tow plane. But there a few more alternatives as well. Do your primary flight training in an aircraft powered by jet fuel - Jet-A does not contain lead in it so it is no more risky than unleaded automotive gasoline. ...


8

This is a long answer but I think it explains a viable, realistic alternative to 100LL and Jet-A. There is a common alternative to 100LL: regular gasoline! Many airplanes, particularly trainers, can use ethanol-free automotive fuel interchangeably with 100LL. It's just a matter of finding a school that has the right airplanes. All you need to do is call ...


6

I have not seen any studies on this, nor would I expect to as Avgas is such a niche product and the price of it is not heavily dependent on the price of the underlying fuel itself. If you look at this answer the reason avgas is so expensive is that it has special requirements for making it, storing and transporting it and so little is produced that there's ...


5

Gasoline (both avgas and mogas) grades are distinguished solely by octane rating and lead content. In theory, the octane rating is the amount of actual octane (C8H18) it contains, with the remainder being mostly heptane (C7H16), hexane (C6H14), pentane (C5H12), etc. As you note, a higher octane rating is needed for engines with higher compression ratios. A ...


5

Fuel injectors in GA piston engines are actually fixed nozzles, so short of fuel contamination, are not so easy to clog,since the only thing that can be deposited with clean fuel is the blue dye in the avgas. In 8 years maintaining a fleet of 6 to 8 injected Continental engines, running 200-700 hours / year, I did not see a fuel-deposit blocked nozzle. ...


5

FAA Advisory Circular AC No: 23.1521-1B deals with use of IPA for Part 23 aircraft. It states: ASTM D 910, Standard Specification for Aviation Gasolines, allows the use of isopropyl alcohol conforming to the requirements of ASTM D 4171, specifications for Fuel System Icing Inhibitor, as a fuel system icing inhibitor. Accordingly, isopropyl alcohol ...


4

The main difference is avgas is based on completely different chemistry, paraffin (the flammable component of candle wax) and mogas is based on aeromatic hydrocarbons (like benzine). (Forget about alcohol - mogas MUST be alcohol free) The paraffin base makes avgas much more stable (so it can be stored a long time) and it has a much lower Reid Vapor ...


4

Chemically speaking, The difference in the fuels is the inclusion of lead-based additives that increase the Octane rating of the fuel, which are otherwise banned for use in other settings due to the negative effect on air quality. The other common use of leaded fuels I can think of is in auto racing, which also doesn't particularly prioritise air quality. ...


3

It seems as though there was an accident involving a PA-23-180 a while back that lead to this advisory. You can see the full report here (interestingly this was published by the NTSB not the FAA). Require that Piper, Beech, and other airplane manufacturers who have not already done so issue service and operating information regarding the use of fuel ...


3

I'm not aware of any FAA-approved (or FAA-accepted) products for on-engine fuel injector cleaning. If your injectors are blocking due to lead deposits a tricresyl phosphate additive may help improve lead scavenging and prevent the problem, but it's probably not going to clean a clogged injector. (TCP is also pretty nasty stuff – leaning your engine more ...


2

I fly a PA-30 Twin Comanche regularly,and,since the POH does not discuss use of isopropyl alcohol or Prist,have contacted Piper repeatedly to seek approval.No response has come from Piper.AOPA and Int’l Comanche Society are equally silent on this topic.I even requested that Air Safety Foundation look into it. I consider this issue of great importance, as the ...


2

What's the reason for the huge increase in price between car and aviation gas? There are many differences, as other answers mentioned, but not as big as the experienced prices show. But by only focusing on the product it's easy to miss cost involved in distribution and sales. An FBO has at least the same, usually much higher, fixed cost than an average gas ...


2

The main issue, the one that bans ethanol blend fuel for use under the autofuel STC, is the effects of ethanol on rubber components in the fuel system. Ethanol is also mildly corrosive to aluminum but nowhere near as bad as methanol, which will dissolve a fuel tank in days (methanol powered race cars race and then purge their fuel systems right away). 10%...


1

Mogas and avgas are very similar ; the difference is in ratio of high octane to lower octane components . The major group of high octane components are aromatics; the xlyenes with octanes well over 100. Also some parafinics like octane ( which is 100 octane ). Also some products from alkylation ( "alky") but I don't know the specific compound names. Xlyenes ...


1

The problem is basically bureaucratic delays, helped along by easing of EPA timetables on the banning of leaded fuel, taking some of the pressure off, which has caused the developer of UL102, Swift Fuels, to suspend its 2nd Phase testing until the machine gets moving.


1

It's not just big twins that have "high compression" or use turbos. Many four and six seat engines have higher compression engines also without turbos. My Lycoming O-360-A1F6D has no turbo. has 8.5:1 compression ratio cylinders and needs 100LL to prevent early detonation. https://www.lycoming.com/sites/default/files/O-HO-IO-HIO-AIO%20%26%20TIO-360%20Oper%...


1

The figure of merit here is thrust to weight ratio (https://en.m.wikipedia.org/wiki/Thrust-to-weight_ratio) For a good turbojet, you get about 5:1. So a 100 lb engine could produce about 500 lbf of thrust. Modern High bypass turbofans are significantly more fuel efficient than turbojets, but the thrust to weight ratio is still about 5:1. So calculate how ...


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