Purely hypothetical question...
 

...but what would happen if you filled your turbine helicopter with avgas and started it?

Ka-bum :o :o :o

Depends - some types will allow limited use of avgas under some circumstances.

Shirley, if you fill your helicopter with avgas it's going to bugger-up the seat covers before leaking out through the door seals.

Digin - Brilliant :p :p :p

As always, read the Flight Manual.

Some helicopter engines aren't allowed to burn it, some are, albeit usually for a given period within the service life.

Ex Yugoslavian Air Force Gazelle could use mixture of different fuels (there was a table of allowed mixtures), but only for limited time, after which engine was supposed to go to detailed inspection/overhaul

What ShyTorque said.
Most engines will run on it, but there will be issues with fuel pumps, FCU's and the Turbine that will prove to be fatal at worst and hugely expensive, at best, given enough time....

Gazelle. 25 hrs total engine time (before scrap iirc) on avgas or petrol. Enough for an emergency topup from a petrol bowser (or at a tankstelle) then rapid transit...west.

From the RR 250-C47B (B407) Operation and Maintenance Manual (Sep 09): Fuel Specifications

"(2) Emergency

Operation on ASTM D-910 AVGAS, all grades, is permitted for a maximum of six hours for each turbine overhaul period if aircraft boost pumps are available and turned on."

diginagain
Cant be flying a 500 then seats!! would not even hold it back to cover carpets

Years ago I studied this in some detail (in regard to what you could run a Gnome 1400 on in awkward circumstances).

Mostly, gas turbines will actually run on just about any hydrocarbon that will go though the fuel pump. The difficulties are associated with:

getting them to light up

getting them to stay in temperature limits

getting them to stay lubricated.

There are other problems with hot and high (especially high - vapour pressures and all that).

If your engine has an automatic temperature limiter that actually works at a non-catastrophic setting, running it on petrol shouldn't cause too many problems in the short tem - ie it won't burn out and it won't flame out. What damage you are doing medium term is a different question.

Diesel has the opposite problem. Once you have it lit it should be fine. But it doesn't light as easily as kero, not that there is much between them.

If your aircraft has two tanks, the obvious advice is to put the emergency fuel (and it should only ever be that) in one tank, use the other one for start / t-o / landing / and run on the funny stuff in the cruise only, and if the situation will allow, on one engine only (you are flying a twin doing this kinda stuff, yes?)

And as has already been hinted, the sort of emergency this applies to is where somebody (you?) is definitely going to die if you don't. This is not for the normal worrying-about-regulations situation.

Iain
Still unemployed

Avgas in jet turbine heli?
 

Yaaahooo! Too funny! diginagain!:DHeh,heh,heh, the heli would need a really good clean after and you'd have to put in one of those 'dangling' air fresheners!

Not necessarily, as I said earlier, the advice is in the Flight Manual and it varies between types of engine.

The engines for the type I fly can use AVGAS Grades: 80, 100 and 100LL (MIL-G-5572) as an emergency fuel (i.e. should only be used whenever any of the authorized fuel grades is not available).

Restrictions: Do not use for longer than 150 hours during any period between engine overhauls.

150 hours is hardly a "do or die" situation but the running time obviously needs recording in the tech log if an emergency fuel is used.

(These engines can also use diesel fuel without penalty but with OAT restrictions).

To answer 206 jock's original question: Nothing out of the ordinary.

Agreed, the difference is hardly noticeable.

The issue with Avgas is the build up of lead deposits causing hot spots on the turbine wheels.

As Shy Torque points out some engines are approved to run on diesel. i.e.(PW206/207). But be aware that the engine may be OK but in some cases the airframe is not. (EC135?)

In the High Arctic in Canada Winter Diesel and Jet is the same thing.

Flying through volcanic ash soon sorts that out. ;)

Clearly the 500 door seals are inferior to a Gazelle's.

As the responders have described, turbines have been run on lots of fuels. The details are the problem, such as the lead depostis from high lead avgas (which cause hot spots and flow disruptions on the blades, and can seriously damage the engine, over time).
Turbines can run on perfume and dead cats, so if you have to do it, do so (escaping from a James Bond villian, for example) but log the time carefully and be ready for a hot end overhaul, unless the fuel is specifically listed on the engine's qual sheet, and in the airframe flight manual (since the fuel tankage, pumps and valves must withstand the fuel, too.)

Nick, I think there are at least two stories you are holding back from us :p