3 ms·

Yup. Old small piston airplanes had an exemption to use leaded gas "for safety". Mind you, these are the engines running on 1950s tech that still have carbureto

Yup. Old small piston airplanes had an exemption to use leaded gas "for safety". Mind you, these are the engines running on 1950s tech that still have carburetors. The failure to test and approve an unleaded fuel lead is a long and unpleasant story.

pc86 3y ago
I mean, brand new single-engine prop planes with modern fuel-injection systems are also running on leaded gas, so the fact that really old planes also are is kind of obvious/irrelevant. With a handful of exceptions, single-engine prop planes are only certified to run on 100-octane leaded gasoline. For many (maybe even most, but I don't know the exact numbers) certified aircraft there is no legal path to get it to run on any other type of fuel. Certain planes have supplemental type certificates to allow an expensive conversion but it's far from the norm.
- BorgHunter 3y ago
  > With a handful of exceptions, single-engine prop planes are only certified to run on 100-octane leaded gasoline. This was true up until last year, when G100UL was approved as a drop-in replacement for 100LL. It does require a STC and the associated paperwork, but this is apparently pro forma and quite cheap, and doesn't require any modification to the aircraft apart from some placards. The problem, of course, is that G100UL isn't really available anywhere yet, while 100LL is still ubiquitous.
- dontlaugh 3y ago
  There are 100 RON fuels without lead.
  - jabl 3y ago
    Sure there are, but the 100 in 100 octane avgas refers to MON, not RON. 100 MON fuel is a bit trickier to be done without lead, although we now have G100UL which does it.
- Reason077 3y ago
  > "For many (maybe even most, but I don't know the exact numbers) certified aircraft there is no legal path to get it to run on any other type of fuel." Until recently this was true. But since September 2022, G100UL is legal and certified for "every spark ignition piston engine and every airframe using a spark ignition piston engine in the FAA’s Type Certificate database.”
- elzbardico 3y ago
  Yes, I understand using leaded gas in older designs. But what was the manufacturer's excuse to keep designing engines that require leaded gas even on fuel-injected, ECU equipped newer designs? Not a rhetorical question, I am genuinely curious.
  - tass 3y ago
    New and old designs have been tested and can work with unleaded fuel. (Edit: there are surely some exceptions here, so I don’t mean this to be all encompassing) New designs must work with leaded fuel since that is the fuel which is available - until avgas contains no lead this will continue to be the case. Side note, most new planes are sold without an ecu.
- NelsonMinar 3y ago
  You're right, some GA engines use fuel injection, also a 1950s technology. I used to fly a Cardinal with Lycoming IO-360. We got the fancy GAMIjectors and it made a huge improvement. Yes, the big exciting 2000s technology was "the holes in the injector are sized to provide calibrated fuel flow". While I'm rambling, the dual spark in a GA engine is really interesting.

pc86 3y ago

I mean, brand new single-engine prop planes with modern fuel-injection systems are also running on leaded gas, so the fact that really old planes also are is kind of obvious/irrelevant. With a handful of exceptions, single-engine prop planes are only certified to run on 100-octane leaded gasoline. For many (maybe even most, but I don't know the exact numbers) certified aircraft there is no legal path to get it to run on any other type of fuel. Certain planes have supplemental type certificates to allow an expensive conversion but it's far from the norm.

BorgHunter 3y ago
> With a handful of exceptions, single-engine prop planes are only certified to run on 100-octane leaded gasoline. This was true up until last year, when G100UL was approved as a drop-in replacement for 100LL. It does require a STC and the associated paperwork, but this is apparently pro forma and quite cheap, and doesn't require any modification to the aircraft apart from some placards. The problem, of course, is that G100UL isn't really available anywhere yet, while 100LL is still ubiquitous.
dontlaugh 3y ago
There are 100 RON fuels without lead.
- jabl 3y ago
  Sure there are, but the 100 in 100 octane avgas refers to MON, not RON. 100 MON fuel is a bit trickier to be done without lead, although we now have G100UL which does it.
Reason077 3y ago
> "For many (maybe even most, but I don't know the exact numbers) certified aircraft there is no legal path to get it to run on any other type of fuel." Until recently this was true. But since September 2022, G100UL is legal and certified for "every spark ignition piston engine and every airframe using a spark ignition piston engine in the FAA’s Type Certificate database.”
elzbardico 3y ago
Yes, I understand using leaded gas in older designs. But what was the manufacturer's excuse to keep designing engines that require leaded gas even on fuel-injected, ECU equipped newer designs? Not a rhetorical question, I am genuinely curious.
- tass 3y ago
  New and old designs have been tested and can work with unleaded fuel. (Edit: there are surely some exceptions here, so I don’t mean this to be all encompassing) New designs must work with leaded fuel since that is the fuel which is available - until avgas contains no lead this will continue to be the case. Side note, most new planes are sold without an ecu.
NelsonMinar 3y ago
You're right, some GA engines use fuel injection, also a 1950s technology. I used to fly a Cardinal with Lycoming IO-360. We got the fancy GAMIjectors and it made a huge improvement. Yes, the big exciting 2000s technology was "the holes in the injector are sized to provide calibrated fuel flow". While I'm rambling, the dual spark in a GA engine is really interesting.