Engine choice dictates aircraft choice?

linspuk · Post by **linspuk** » Thu Apr 14, 2011 10:37 am

I guess that we have to recognise the gradual demise in availability of Avgas over coming years, and it's replacement by substitute fuel, which will necessitate engine modifications and might cause engine problems for some. So I ask myself, is it wise to choose an aircraft (eg most RV's) to build that requires an Avgas engine to be purchased and installed, and used, in several years time, which might actually be obsolescent? Surely the only way to go in a build project now is with aircraft using mogas engines, to avoid this worry and dilemma?
I'm posing the question to elicit opinion, as I'm very shortly going to commit to my first build project, and whilst my head says aircraft A (powered by Rotax) , my heart is with aircraft B (powered by Lycoming).

Jeremy Liber · Post by **Jeremy Liber** » Thu Apr 14, 2011 12:45 pm

... or aircraft C (powered by a Jet A-1 burning diesel engine such as the Wilsch).

There are several RVs flying with the Wilsch engine, maybe contact the owner of one or more of them to get their feedback.

Mick Bevan · Post by **Mick Bevan** » Thu Apr 14, 2011 1:14 pm

Hi there
Do what plenty of RV owners do; run it with a tank of Mogas and a tank of avgas. take off on Av, cruise on Mo, land on Av.Personally, I can't see Avgas being supplanted entirely by the time you get your project completed.
regards
MB

Brian Hope · Post by **Brian Hope** » Thu Apr 14, 2011 3:09 pm

I think it depends on which Lycoming you choose to use. The 150 hp O-320 has low compression pistons and is perfectly happy with mogas, I've been told that the 160 and the O-360 engines are not so happy because the mogas octane rating is a bit too low. No doubt some users out there can add truth or otherwise to that theory.
There are enough aircraft with engines requiring 100LL that it or an alternative will almost certainly be available well into the future.

linspuk · Post by **linspuk** » Thu Apr 14, 2011 4:19 pm

Mick Bevan wrote:Hi there
Do what plenty of RV owners do; run it with a tank of Mogas and a tank of avgas. take off on Av, cruise on Mo, land on Av.Personally, I can't see Avgas being supplanted entirely by the time you get your project completed.
regards
MB

Points above noted, but I'm investing my money and effort into an aircraft I want to fly for a fair few years, rather than still being ok in 5. Also, avgas alternates may well appear but will necessarily be a compromise in efficiency in working compared to the original engine design. I agree with the diesel idea, and read with interest a recent article on powering an RV with the Wilksch. I realise beauty is in the eye of the beholder, but I felt the cowling of the diesel rather spoilt the lines of the RV though.
I'm being wimpish I know, but these engines are so big a part of the cost that it's a crucial decision which I suspect is somewhat overlooked in favour of performance in the short term.
I'm still torn though, but then the romantic in me wants a Pietenpol too!

Bill McCarthy · Post by **Bill McCarthy** » Thu Apr 14, 2011 6:42 pm

You never know, a super duper engine conversion may come out of the woodwork in the LAA competition for "new" power plants.
I would have thought that the Rover V8 conversion that appeared briefly in an aged PFA mag might have had more interest - loads of torque, reasonably light, hydraulic tappets and cheap.

Tom Sheppard · Post by **Tom Sheppard** » Thu Apr 14, 2011 8:29 pm

I doubt it, frankly. The cost of fuel is one issue, its quality anotther. It costs a lot of fuel to lift a big engine and a big engine needs to lift a lot as well in order to have any endurance. The future belongs to diesel. Jet A1 is the way to get an affordable running cost and Diesel means that you can turn fuel load into payload. Much better. If you are looking at building a plane for many years' use, then why build using an engine design that is so very old and inefficient? If you do, you'll be changing it out before long anyway when you realise that it costs three times as much to operate and you could get off much more quickly or fly another 250 miles with a modern lump.

Rod1 · Post by **Rod1** » Fri Apr 15, 2011 7:34 pm

I made a decision to go Rotax 9 years ago because I thought the cost of fuel would be a threat to my ability to continue in the sport. I am very happy with my choice and am operating my MCR on less cost (all in) then just the cost of fuel for a 160hp RV. Francis recently told me that no RV’s had been approved for mogas in the UK but that it was theoretically possible to get one through with the addition of an extra fuel pump. I assume the cost of the paper to get this approved might be a factor

Rod1

Nigel Hitchman · Post by **Nigel Hitchman** » Wed Apr 27, 2011 11:37 am

while Rod's MCR might be more economicall to fly than some, you have to be careful when you look at the figures.
My RV6 might burn more fuel per hour, just below 30l per hour is what I calculate, I think its actually a bit better than that, but that is at 170mph. If Im going somewhere, this is a lot more economical than my Piper Cub. If I slow down to rotax speeds, the fuel burn goes down too. While Im still burning slightly more than the MCR and maybe some Europas when flying at their speeds, I will probably compare favourably with a lot of the other Rotax powered light aircraft when it comes to miles per gallon.
I would also suggest that the re-sale value of an RV will be higher (in comparison to the purchase price) and the long term maintainability will be higher too.
Lycoming are working on approval for Mogas in even their higher compression engines and it appears that the alcohol problems with mogas are going to be easier to resolve than first thought, so I dont think there will be a problem with fuel for Lycomings in your homebuilt for many years.
Surprised no UK RVs have been approved to fly on Mogas, I thought there were quite a number of 150hp RVs flying on Mogas and of course many in other countries of even higher hp.

I would certainly be more inclined to build an aircraft with a Lycoming or a Rotax rather than an experimental engine. Diesel might be the way to go eventually, but I dont think we are they yet, hopefully Wilksch will prove me wrong!

Nick Allen · Post by **Nick Allen** » Wed Apr 27, 2011 11:52 am

Of course, someone might sooner or later try to put one of the bigger ULPower engines into an RV, which might make quite a good combination: compact, Mogas, injected...
http://www.ulpower.com/engines/ul350i/index.html
(Remembering that according to Vans they haved flown several of their prototypes happily on 118 hp Lycomings.)

Nigel Hitchman · Post by **Nigel Hitchman** » Wed Apr 27, 2011 12:15 pm

I was amazed to see lots of different ULpower engines at Fredrichshafen, upto something like 260hp. Hopefully they will all prove to be as good an engine as the initial 80hp one seems to be.
The Vans RV9 was originally flown with a Lycoming O-235 which the aircraft was designed around, but it seems since then most people have opted for 150/160 hp Lyc O-320s not sure why. Of course the Vans RV-12 is designed for the Rotax 912.

Nick Allen · Post by **Nick Allen** » Wed Apr 27, 2011 12:27 pm

most people have opted for 150/160 hp Lyc O-320s not sure why

Habit? Engine envy? Or I guess, with a fixed-pitch prop, better take-off performance... But for a reasonably light, streamlined airframe 120hp ought to be a sufficiency.
(However, Nigel, I did scrounge a ride in the back of a Joe's RV4 on Sunday, and all I can say is "Yee-ha"...and I can understand why people like to have some extra power to play with in them!)

Andrew Gardner · Post by **Andrew Gardner** » Wed Nov 02, 2011 6:28 pm

Hopefully there will be a breakthrough in electric powerplants in the not too distant future, with both the automotive and aviation industries currently working on them.

Battery technology seems to be the limiting factor at the moment.

If an alternative approach to generating/storing electricity could be found which did not require batteries that might be one approach.

Another alternative of using a very small petrol/diesel etc. engine to generate electricity to top up a battery which is actually powering the aircraft via an electric engine then the fuel type might not be so important.

ian herdis · Post by **ian herdis** » Thu Nov 03, 2011 12:27 am

There is a Titan T51 currently in build using the Susuki V6 engine which Titan supply this is available as 165 or 183 HP so right in the RV range that may be one to watch

Ian
Building Sportsman 2+2

IanTadd · Post by **IanTadd** » Fri Nov 04, 2011 8:10 am

Andrew Gardner wrote:Hopefully there will be a breakthrough in electric powerplants in the not too distant future, with both the automotive and aviation industries currently working on them.

Battery technology seems to be the limiting factor at the moment.

If an alternative approach to generating/storing electricity could be found which did not require batteries that might be one approach.

Another alternative of using a very small petrol/diesel etc. engine to generate electricity to top up a battery which is actually powering the aircraft via an electric engine then the fuel type might not be so important.

I am a keen promoter of electric power so echo your sentiments about a breakthrough in electric power. However I would suggest that its unlikely that a viable 4-6 hour range in conventional 2/4 seat airframe will become possible in a time frame that should influence todays builds. Some remarkable research work has been achieved over the last couple of years with a range of technologies metal-air, lithium, refuel-able batteries (Cambridge crude being the latest development) and super capacitors which may dramatically benefit from the latest developments with graphene (for which a Nobel prize was given last year). Interestingly all of these developments rely on nanotechnology to a greater or lessor extent.
Despite this there is a giant mountain to climb, the best available batteries are achieving 150-200wh/kg (capacitors significantly less) petrol used in Rotax gives 1700wh/kg, until electric storage or generation can achieve over the 1000-1200wh/kg it will be unable to compete with the currant IC engine. While careful design and high aspect ratio wings can reduce the energy requirement (the Chinese built e430 demonstrates this) those same techniques can be applied to aircraft powered by IC engines. Its not difficult to imagine how small an IC engine and fuel tank would be needed to power the e430. In case anyone is wondering why 1000-1200 wh/kg can match 1700wh/kg from petrol, its because the electric motor is so much lighter than an IC engine and therefore the electric fuel tank can be heavier than a tank fuel of petrol while giving us a similar all up weight of motor and tank for a practical flight duration.

As far as hybrids are concerned, I may be proved wrong but the typical power use in light aircraft leaves me doubtful that hybrids with an IC engine are a viable way forward in the same way as they may be for cars on an Urban cycle. Hybrids using a fuel cell are a different mater and its hard to see (given todays state of research) how any successful fuel cell aircraft will not be a hybrid of fuel cell with a battery or capacitor.

Light Aircraft Association

Engine choice dictates aircraft choice?

Engine choice dictates aircraft choice?

Electric?

Re: Electric?