matt_eghr

Investigating the above statement for aero-eng project.

However, not sure on the feasibility due to high rpm output of a rotary engine. Also can aircraft use car petrol (95/97 octane) if a car engine is adapted to a light aircraft, eg mazdas RX-8? Why is AVGAS used for aircraft?
Do all GA single props have reduction gearing to the propeller, would this be a reliable gearing linkage? What sort of torque is required of an aircraft engine?

With the improvements in efficiecy, minimal vibration and more power to weight ratio than a piston engine a rotary engine would proberbly be good enough to use in small GA single props!

I have e-mailed mazda for some extra info outside of their website regarding the actual engine, but just posting here for any knowledge about the use of this engine in aviation.

Thanks! Matt

andyb79

you might want to take a look at this site

rotary aviation

and i would say the main reason this hasnt been done a great deal before is ddue to the rather questionably reliability of these engines

fruitloop

I think due to it's enormous drinking problem to make power that is "usable" it has been left alone..!! I could be wrong !!

Genghis the Engineer

(1) High RPM isn't a new problem, 2-stroke microlight / homebuilt engines such as the Rotax 582 handle it with a gearbox or belt / chain reduction drive.

In my experience, if you can keep tipspeeds consistently below 0.7M then the system should work. Torque will drop out from power and speed, propeller pitch setting will drop out from that.


(2) UK Airworthiness Notice No. 98, contained in CAP 455 contains the rules on using unleaded MOGAS in aircraft. It is possible - in fact for many engines, it's a better fuel.

(3) AVGAS, which in it's 100LL form has 100 octane rating, and about 3 times the lead of old 4-star is used because (a) many aircraft engines were designed for this sort of makeup, (b) because it comes from a "regulated" aviation fuel source - which keeps the CAA happy, and probably most of all (c) habit. Actually rotaries are incredibly tolerant of different fuels and will run on just about anything with a bit of tweaking.


Mazda conversions are quite popular in some countries, particularly for Gyroplanes where the engineering problems aren't all that different to a conventional SEP.

But, they are thirsty, and the aircraft / motorcycle rotaries such as the Norton have only ever been used for unmanned aircraft applications because of a relatively poor reliability. Without doubt the Mazda is a much more reliable unit (and I'm sure there are others), but they aren't all that light - not necessarily because they can't be, but because they don't need to.



- I think that if you take a look at websites dealing with Ultralights and Gyroplanes, particularly in Australia, you'll find some information about Mazda rotary conversions for aircraft use. Also look in Janes at the work done in the UK for UAVs using Rotary engines, and look up a company called "Midwest" who were developing aircraft rotaries based somewhere near Gloucester before they moved to Germany about 4 years ago in frustration at CAA not letting them do anything (although rumour has it, CAA were equally frustrated that Midwest would never give them the information that they asked for).

Good luck with your project,

G

noisy

Hi Matt,

You might want to look into the cost of an overhaul. I have an inkling that Wankel rotaries (there, I said it!) are heavy on maintenance. The combustion process relies on a good seal within the pockets, so tolerances are tight which causes wear & tear.

Mind you, I have heard that some conventional piston engines are very expensive to have overhauled.

Noisy

matt_eghr

Thanks for all your feedback, i've written to mazda regarding the servicing required, fuel consumption, weight, dimensions, idle rpm and reliability!...just waiting for a reply.
The RX-8 car does quite good mpg so i presume it would run well for gal/hr!
Im sure there are drawbacks to this type of engine but still worth doing a project on.
Also what make/specifications are the engines that cessnas and warriors use to make comparisons with the RX-8?
thanks!

fruitloop

Quote "The RX-8 car does quite good mpg so i presume it would run well for gal/hr!" Yes but remember it isn't pulling between 70% (cruising) and 100+%(max) RPM when being driven on the road !! PSRU (propellor speed reduction units) are available for a variety of engines.
http://www.fighterescortwings.com/subsubpage3.html
http://northwest-aero.com/
and many others !!
If you want to compare a 12a,13b,or a 20a rotary for fuel usage/hr/shaft horsepower as opposed to either a piston engine/gas turbine you will be "shocked".

As Genghis the Engineer has pointed out regards prop tip speeds and fuel type's for "regs" 1 other area that I would "suggest" you look at is vibration at high RPM with rotaries.This in itself also causes extra maintenance.
Cheers

Genghis the Engineer

You'll find this sort of information in a copy of "Janes all the worlds aircraft", if it's worth it's salt, your University library should have plenty of back copies.

Aircraft in the front, engines in the back (if it's a seriously old copy, airships before aircraft), both in alphabetical order of nationality, then alphabetical order of manufacturer.

The "World directory of leisure aviation", which costs about £6 is worth getting hold of for a different slant on similar problems.



One hint with engine data - always check you are comparing like with like, different companies will use subtly different horsepower definitions (cross-check kW), and there's no standard as to what combination of ancilliaries are attached for the weight and dimenstions quoted.

G