4 ms·

I hope we can get it, or even 94UL (which is 100LL minus the lead) at airports soon. Many of us can run 94UL just fine, but there's nowhere it's available.

sokoloff 5y ago
Though many airplanes can, the working airplanes (that burn a lot of fuel) mostly cannot and if the FBO is faced with being able to sell fuel to all airplanes or just some with a tank and dispenser, it's a pretty easy call. The promise of G100UL is that that FBO can (eventually) sell this fuel to all gasoline-fueled airplanes.
- Blackthorn 5y ago
  I know what the promise is. My point is I'd like any unleaded fuel at all to be available at the pump. Regardless of whether it needs to support the world's shittiest ancient engines or not.
  - sokoloff 5y ago
    Being able to support turbocharged engines is critical to being economically viable for FBOs which is critical to being actually available for sale. (Estimates were that 70% of the airplanes could use a 94UL-type gasoline, but that the 30% of remaining airplanes burned [and bought] 70% of the fuel sold, so a 94UL solution is, as you've experienced, not economically viable.)
    - ericd 5y ago
      Apologies, I’m not very familiar with aircraft engines, why can’t we simply use high octane unleaded gasoline, like most turbocharged car engines? Are the cylinder pressures significantly higher in airplane engines?
      - sokoloff 5y ago
        Airplane engines are overwhelmingly air-cooled, fixed timing (after starting), pilot-controlled fueling, and expected to produce 100% of rated power for 5 minutes and then 65-75% of rated power for hours on end. Automotive engines are overwhelmingly water-cooled [providing a far more stable and lower cylinder head temperature], variable/computer-controlled timing often with knock sensing [providing the means to adjust timing dynamically when anything beyond light pinging is detected], closed-loop fuel control, and rarely producing more than 20% of their rated power. Aircraft engines need to stay together with a cylinder head temperature of 460ºF, fixed timing, and fuel mixtures that are set by the pilot. It's a far more demanding (and less controlled) environment. Some additional refs that might be interesting: https://www.avweb.com/features/pelicans-perch-43detonation-myths/ https://www.avweb.com/features/pelicans-perch-43detonation-m... https://www.avweb.com/features/pelicans-perch-55lead-in-the-hogwash/ https://www.avweb.com/features/pelicans-perch-55lead-in-the-... https://www.avweb.com/features_old/pelicans-perch-31those-fire-breathing-turbos-part-1/ https://www.avweb.com/features_old/pelicans-perch-31those-fi...
        maxcan 5y ago
        Small nitpick but while aircraft engines cannot catastrophically fail at 460F, no one should be flying them that hot. Its basically guaranteed to shorten the TBO on the engine that way. When I was flying a turbocharged cirrus (notoriously hot running engine) we always kept the cylinder heads to 380F. It limited our climb performance but was so much better for the engine.
        sokoloff 5y ago
        I agree. I use 380°F as my soft limit for a TNIO550B and take more aggressive action at 395°F. Nevertheless, it’s a certification requirement that the engine have appropriate detonation margin at the manufacturer’s declared CHT redline and TCM/CMI has chosen to put their redline around 75°F higher than I’m comfortable in normal operations.
        maxcan 5y ago
btgeekboy 5y ago
At least one airport I know of - KAWO - used to have it, but no longer does. Wonder what the story is there.

sokoloff 5y ago

Though many airplanes can, the working airplanes (that burn a lot of fuel) mostly cannot and if the FBO is faced with being able to sell fuel to all airplanes or just some with a tank and dispenser, it's a pretty easy call. The promise of G100UL is that that FBO can (eventually) sell this fuel to all gasoline-fueled airplanes.

Blackthorn 5y ago
I know what the promise is. My point is I'd like any unleaded fuel at all to be available at the pump. Regardless of whether it needs to support the world's shittiest ancient engines or not.
- sokoloff 5y ago
  Being able to support turbocharged engines is critical to being economically viable for FBOs which is critical to being actually available for sale. (Estimates were that 70% of the airplanes could use a 94UL-type gasoline, but that the 30% of remaining airplanes burned [and bought] 70% of the fuel sold, so a 94UL solution is, as you've experienced, not economically viable.)
  - ericd 5y ago
    Apologies, I’m not very familiar with aircraft engines, why can’t we simply use high octane unleaded gasoline, like most turbocharged car engines? Are the cylinder pressures significantly higher in airplane engines?
    - sokoloff 5y ago
      Airplane engines are overwhelmingly air-cooled, fixed timing (after starting), pilot-controlled fueling, and expected to produce 100% of rated power for 5 minutes and then 65-75% of rated power for hours on end. Automotive engines are overwhelmingly water-cooled [providing a far more stable and lower cylinder head temperature], variable/computer-controlled timing often with knock sensing [providing the means to adjust timing dynamically when anything beyond light pinging is detected], closed-loop fuel control, and rarely producing more than 20% of their rated power. Aircraft engines need to stay together with a cylinder head temperature of 460ºF, fixed timing, and fuel mixtures that are set by the pilot. It's a far more demanding (and less controlled) environment. Some additional refs that might be interesting: https://www.avweb.com/features/pelicans-perch-43detonation-myths/ https://www.avweb.com/features/pelicans-perch-43detonation-m... https://www.avweb.com/features/pelicans-perch-55lead-in-the-hogwash/ https://www.avweb.com/features/pelicans-perch-55lead-in-the-... https://www.avweb.com/features_old/pelicans-perch-31those-fire-breathing-turbos-part-1/ https://www.avweb.com/features_old/pelicans-perch-31those-fi...
      - maxcan 5y ago
        Small nitpick but while aircraft engines cannot catastrophically fail at 460F, no one should be flying them that hot. Its basically guaranteed to shorten the TBO on the engine that way. When I was flying a turbocharged cirrus (notoriously hot running engine) we always kept the cylinder heads to 380F. It limited our climb performance but was so much better for the engine.
        sokoloff 5y ago
        I agree. I use 380°F as my soft limit for a TNIO550B and take more aggressive action at 395°F. Nevertheless, it’s a certification requirement that the engine have appropriate detonation margin at the manufacturer’s declared CHT redline and TCM/CMI has chosen to put their redline around 75°F higher than I’m comfortable in normal operations.
        maxcan 5y ago

btgeekboy 5y ago

At least one airport I know of - KAWO - used to have it, but no longer does. Wonder what the story is there.