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airplanes can gradually transition Except they can't, since there is no approved alternative. The other problem is that even planes that can run unleaded gas

by lutorm 5y ago

airplanes can gradually transition Except they can't, since there is no approved alternative. The other problem is that even planes that can run unleaded gas often don't, because it's not available at the airport. Avgas is a tiny market and because of costs most FBOs can't or won't set up another fuel delivery infrastructure to run two fuels over some short transition period. Because of this, an additional requirement on a replacement is also that it be safely mixable with 100LL in any ratio, because during the transition period this will happen as people fly from airports where it exists to airports where it doesn't. This problem is being solved (https://www.faa.gov/about/initiatives/avgas/ https://www.faa.gov/about/initiatives/avgas/).

mlyle 5y ago
> Except they can't, since there is no approved alternative. There's an increasing number of diesel engines for GA aircraft, and supplemental type certificates to retrofit them into the same. If 100LL got more expensive, you'd see more people opting for the diesels when an engine reaches the end of its life. e.g. http://www.continentaldiesel.com/typo3/fileadmin/_centurion/news/newsuploads/179/PR_170406_EASA-FAA%20STC-C172-G1000-en.pdf http://www.continentaldiesel.com/typo3/fileadmin/_centurion/... Yes, it'd be really cool to end up with a lower-lead fuel that's safely combined with 100LL. That's been "imminent" for the last 25 years. The poster above advocates for a "rip off the band-aid" approach. GA advocates for a gradual, painless transition that, in practice, will never happen. Surely there's some middle ground?
- lutorm 5y ago
  A post further down says that the first unleaded replacement for 100LL was actually just approved.
  - mlyle 5y ago
    Swift UL94 has been to market for 3 years with very low uptake.
    - lutorm 5y ago
      Fair enough, but that's not a replacement for 100LL since not all engines can use it. It's gotta be a pretty large FBO to have enough market to pay for setting up a distribution for UL94 in addition to 100 octane gas. Like, there are engines that were certificated to run on 80/87 avgas but no one sells that any more either. Today's avgas market just isn't large enough to make it worth offering two fuels.
      - mlyle 5y ago
        About 2/3rds of GA has an STC available to burn it. There's not going to be one single tidy drop-in solution for the entire market. That's why we should tax leaded fuels, and everyone can pick the appropriate solution for them. Some will pick diesel conversions. Some airfields will go 94UL and people will purchase STCs. Presumably some other people will take other paths. And those with the hardest time transitioning can instead pay the tax and burn leaded fuel, still.
    - Aloha 5y ago
      Because as far as I know the engines must have their type acceptance updates to reflect it's allowed use. 3 years is also basically a second at the speeds GA changes at.
      - Blackthorn 5y ago
        The slow uptake has more to do with it just not being all that available.
        mlyle 5y ago
        Yup-- why should an airfield bother with going to 94UL when it's more of a hassle (some planes can't take it, all planes need an STC). But if you taxed the crap out of lead-containing fuels, I suspect more would be interested...
      - mlyle 5y ago
        Yes, technically speaking. Swift charges $100 for a STC, and has coverage of two thirds of the GA fleet. Really, all that needs to happen is an airport needs to decide that lead free is important to them and they'll pay the premium for Swift's fuel.
- Blackthorn 5y ago
  Continental diesels still have "TBR" (time between replacements) instead of "TBO" (time between overhauls). That's a huge problem preventing their uptake.
  - lutorm 5y ago
    Well, plus the fact that a new aviation engine runs $30-60k, which is about what an old, small, airplane is worth. It just doesn't make economic sense to replace those engines, you're effectively just trashing those planes.
    - deleted 5y ago
      [deleted]
  - mlyle 5y ago
    https://www.aviationconsumer.com/aircraftreviews/aircraftstepups/diesel-reset-improved-economics/ https://www.aviationconsumer.com/aircraftreviews/aircraftste... Data seems to imply that the diesel engine lifecycle cost is slightly better now than conventional engines, so electing for a diesel replacement instead of a conventional engine overhaul can make sense... but it's a razor thin difference. If you made leaded fuels more expensive-- more airfields are going to want to move to UL94, and more people at overhaul time are going to go the diesel path, and the problem will gradually get better.

by lutorm 5y ago

mlyle 5y ago

> Except they can't, since there is no approved alternative. There's an increasing number of diesel engines for GA aircraft, and supplemental type certificates to retrofit them into the same. If 100LL got more expensive, you'd see more people opting for the diesels when an engine reaches the end of its life. e.g. http://www.continentaldiesel.com/typo3/fileadmin/_centurion/news/newsuploads/179/PR_170406_EASA-FAA%20STC-C172-G1000-en.pdf http://www.continentaldiesel.com/typo3/fileadmin/_centurion/... Yes, it'd be really cool to end up with a lower-lead fuel that's safely combined with 100LL. That's been "imminent" for the last 25 years. The poster above advocates for a "rip off the band-aid" approach. GA advocates for a gradual, painless transition that, in practice, will never happen. Surely there's some middle ground?

lutorm 5y ago
A post further down says that the first unleaded replacement for 100LL was actually just approved.
- mlyle 5y ago
  Swift UL94 has been to market for 3 years with very low uptake.
  - lutorm 5y ago
    Fair enough, but that's not a replacement for 100LL since not all engines can use it. It's gotta be a pretty large FBO to have enough market to pay for setting up a distribution for UL94 in addition to 100 octane gas. Like, there are engines that were certificated to run on 80/87 avgas but no one sells that any more either. Today's avgas market just isn't large enough to make it worth offering two fuels.
    - mlyle 5y ago
      About 2/3rds of GA has an STC available to burn it. There's not going to be one single tidy drop-in solution for the entire market. That's why we should tax leaded fuels, and everyone can pick the appropriate solution for them. Some will pick diesel conversions. Some airfields will go 94UL and people will purchase STCs. Presumably some other people will take other paths. And those with the hardest time transitioning can instead pay the tax and burn leaded fuel, still.
  - Aloha 5y ago
    Because as far as I know the engines must have their type acceptance updates to reflect it's allowed use. 3 years is also basically a second at the speeds GA changes at.
    - Blackthorn 5y ago
      The slow uptake has more to do with it just not being all that available.
      - mlyle 5y ago
        Yup-- why should an airfield bother with going to 94UL when it's more of a hassle (some planes can't take it, all planes need an STC). But if you taxed the crap out of lead-containing fuels, I suspect more would be interested...
    - mlyle 5y ago
      Yes, technically speaking. Swift charges $100 for a STC, and has coverage of two thirds of the GA fleet. Really, all that needs to happen is an airport needs to decide that lead free is important to them and they'll pay the premium for Swift's fuel.
Blackthorn 5y ago
Continental diesels still have "TBR" (time between replacements) instead of "TBO" (time between overhauls). That's a huge problem preventing their uptake.
- lutorm 5y ago
  Well, plus the fact that a new aviation engine runs $30-60k, which is about what an old, small, airplane is worth. It just doesn't make economic sense to replace those engines, you're effectively just trashing those planes.
  - deleted 5y ago
    [deleted]
- mlyle 5y ago
  https://www.aviationconsumer.com/aircraftreviews/aircraftstepups/diesel-reset-improved-economics/ https://www.aviationconsumer.com/aircraftreviews/aircraftste... Data seems to imply that the diesel engine lifecycle cost is slightly better now than conventional engines, so electing for a diesel replacement instead of a conventional engine overhaul can make sense... but it's a razor thin difference. If you made leaded fuels more expensive-- more airfields are going to want to move to UL94, and more people at overhaul time are going to go the diesel path, and the problem will gradually get better.