3 ms·
> we would now have 40 years of safety data for unleaded and for leaded. When lead was banned in auto gas, it was replaced by MTBE, which itself was banned in
by labcomputer 6y ago
> we would now have 40 years of safety data for unleaded and for leaded.
When lead was banned in auto gas, it was replaced by MTBE, which itself was banned in most states by 2007. The alternative to MTBE is Ethanol, which is currently used in auto gas. But Ethanol is incompatible with aircraft because it is corrosive to aluminum (and tends to cause more serious vapor-lock problems in fuel lines).
In other words, there's no widely-used blend of fuel that could even potentially have 40 years of safety data. Pilots are already used to paying a lot for fuel (more than auto gas), so there's money at stake if someone can come up with an unleaded alternative. It's just that someone has to invent that safe alternative first.
On top of that, fuel is a particularly sensitive issue to the FAA because fuel and engine malfunctions are currently the 3rd and 4th leading causes of aircraft accidents (and this is after the FAA has spent decades on safety programs to reduce fuel-related accidents).
- userbinator 6y agoBut Ethanol is incompatible with aircraft because it is corrosive to aluminum (and tends to cause more serious vapor-lock problems in fuel lines). Incidentally, this is also an issue with small engines in things like garden equipment --- the ethanol tends to degrade plastics over time too.
- perl4ever 6y agoI was generally aware of MTBE, but I didn't know it was universal since the 70s nor necessary for all grades of fuel. What about iso-octane? Also, I happen to have a car from the 80s and in looking for information about the consequences of using fuel with ethanol, some say it can be a problem while other people say at that point in time it was designed to handle it. So I'm not clear on what diversity there was in the types of fuel available over time.
- labcomputer 6y ago> nor necessary for all grades of fuel. That's moving the goalposts. Piston airplane engines typically (but not universally) have high compression ratios, so they require fuel with a high octane rating. In fact, the only avgas that contains lead today is 100LL (100 octane, low lead). If you want to have a discussion about lead in avgas, you're having a discussion specifically about 100 octane fuel. > What about iso-octane? Definitionally, 100 octane fuel has anti-knock properties similar to 100% iso-octane. You may be able to make an approximately-100% iso-octane blend for lab tests, but it's not really possible to manufacture it in commercial quantities. Keep in mind, "premium" auto gas is usually less than 93 octane, and even that has ethanol.