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MagnusNewtonBernouli t1_jdurc5j wrote

Reply to comment by geekpeeps in Does living in an airplane flight path, near an airport, pose a health risk? What happens to the lead from the jets fuel? by [deleted]

It's used in all kinds of commercial flights in piston aircraft.

It's uncommon in airliner flights because it's expensive and causes increased wear and tear in turbines.

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quietflyr t1_jdv85t5 wrote

It's not used in airliner flights because that's not the fuel the engines were designed for.

Can a jet engine run on avgas? Probably, but it's probably not allowed by the certification of the aircraft, and thus is not allowed by the regulations. Some military aircraft have allowances for short runs using alternate fuels like avgas, actual kerosene, diesel, etc, but I doubt most civilian airliners have this option at all.

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MagnusNewtonBernouli t1_jdv99tb wrote

> Can a jet engine run on avgas?

Firstly, turbine not jet. And not only can they but it is in the maintenance manual and the POH/TO for the aircraft.

A plane I flew had this very limitation. 100 hours of operation on 100LL.

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quietflyr t1_jdvgu3m wrote

So when talking about airliners, we're mostly talking about jet engines, which, by the way, are a subclass of turbines.

And your aircraft type had the limitation, but I would guess most modern airliners would not have 100LL as an available alternative fuel at all. Did the airplane you flew have T56 engines?

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richalex2010 t1_jdvnrv9 wrote

> So when talking about airliners, we're mostly talking about jet engines, which, by the way, are a subclass of turbines.

Turbine includes turboprops though, which are a significant minority of airliners and commercial aircraft.

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quietflyr t1_jdvvz8z wrote

The pedantry here is incredible...

Dash-8: 1258 built

ATR-42: 497 built

ATR-72: 1000 built

Beech 1900: 695 built

Saab 340: 459

Those would be all the most popular turboprop airliner types in service today, totalling 3909 aircraft built, ever. And we're talking Part 121 aircraft here, not Part 135. Though adding Part 135 would very likely add to my point.

There have been over 11,000 737s built, over 10,000 A320s, and tens of thousands of other Boeing and Airbus types. Plus 4000 CRJs. Plus 3000 Embraers of various types.

But if you want to pretend my comments aren't valid because I used the word "jet" instead of "turbine" and thus excluded a small proportion of the global airliner fleet, go right ahead.

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paulHarkonen t1_jdvqs74 wrote

"It's in the manual" is just another way to say "it can run on this". How many times did you fuel up with Avgas?

Yes they can run on it (they can run on a lot of stuff) but the practical reality is that they don't.

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gogozrx t1_jdv7xnc wrote

AVGAS isn't used in turbines because it's the wrong fuel for them, and they will not run. AVGAS needs a spark to reliably ignite, and turbines don't work like that - they're effectively diesel engines and ignite the fuel from the heat of compression.

I stand corrected. Turbines *will* run on AVGAS, but it's not recommended, and can have other issues.

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quietflyr t1_jdv96bq wrote

Turbines can run on all different kinds of fuels, including gasoline/avgas. It doesn't mean it will produce its rated power, or will be as reliable as when running jet fuel, but it will run. Avgas/gasoline will definitely ignite from compression alone. Remember, Avgas is leaded so it won't ignite from the heat of compression in a piston engine at its designed compression ratios.

C-130s for example have a section in the flight manual about alternate fuels. They list things like diesel, kerosene, gasoline, avgas, etc, but they're all intended for extreme circumstances (stuck somewhere without jet fuel and need to get out now) and all have maintenance requirements after using them.

That being said, I highly doubt modern commercial turbofans are certified to run these alternate fuels. But from a technical standpoint, they would most likely run.

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ozspook t1_jdv968p wrote

I can assure you that gas turbines have ignitors and can run on a large range of fuels, AVGAS included.

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