Would you buy a diesel?

[Say again s l o w l y]

If you own an aircraft would you be willing to buy one of the new Diesels when they become more widely available?
Are you fed up being ripped off by Lycoming and Continental, who offer sub-standard products at rediculous prices?
How much would you be willing to spend on a new type of engine? I understand that the diesels are not exactly cheap at the moment!!

[big.al]

Our group C172 engine has around 1200hrs left before a replacement is due (Public Cat CofA). At current useage we reckon this is in around 3 years time.

I know very little about engines but I'm aware that a replacement will be around £12k. I would say that if a suitable AVTUR alternative were available for less than £20k it would be well worth the investment. That is assuming the Government hasn't introduced restrictive tax levels on AVTUR by that time of course. If the costs are still running at £40k for a diesel unit then I can't see it being worth the money. On that basis I would hope that the cost of diesel engines would come down over time. If the likes of Thielert etc. really want to get into the market for replacement engines with diesels then I'm sure that they will have to charge less. Otherwise we will really only see diesels on new aircraft for some time to come.

If I had the money to buy a (new) aeroplane outright I would almost certainly consider a diesel. Seems to me that fuel costs of around 25% comapred to Avgas is too good to miss. IMHO of course....

[IO540]

One needs to do an awful lot of hours, probably 500+ / year, before a RETROFIT becomes worth doing.

If there were other benefits, e.g. more power, that would be something else. But in the cases I have seen you get less power at sea level; this will affect takeoff distance substantially in a typical UK airfield (low altitude). The case for diesels (performance being acceptable despite lower spec-sheet HP) does rely to a significant degree on the TAS gain due to the turbocharger, at FL150+. Which basically means a full IR in the UK - unless I am missing something...

I would give it another year or three.

[Send Clowns]

Yes, if I could afford an aircraft! My employers have a contract to teach some groundschool for another organisation, including one of the new diesel engines. It is an incredible powerplant, seems extremely well-built and is a fine, efficient replacement for the traditional piston. The MAP they work at is about 60 "Hg, by the way. Built like a brick outhouse as our engines lecturer put it. He (a fine engineer, many years in the busines behind him signing off engines large and small) is very impressed by this unit.

al - surely the savings would be much greater than that? I am not sure of the current cost of fuels, as I don't pay, but is Avtur not about a third the cost of avgas? These engines are, I believe, slightly more efficient than petrol.

[Say again s l o w l y]

That's the first time I've heard that IO540. I can't quite understand the reason for it though.

Personally I think they are the way forward until we get electrically powered a/c with fuel cells. I won't hold my breath about them though!!

Is there a problem with the weight of the Diesels? What price would people be prepared to pay compared to an equivalent Avgas engine. Will it come down to price or are there other reasons for having a diesel?

Have they got the TBO's to equivalent levels yet or will we have to wait for a few more to be in use first?

[ShyTorque]

Diesels have to be the best way to go forward in light aircraft (pun intended).

Lower fuel burn, far cheaper fuel, no ignition system to go wrong, no mixture control, no carb icing, little or no weight penalty.

What more do you need?

Here's one to look at for starters: :ok:

http://www.wilksch.com/

[WelshFlyer]

The WAM engine is fantastic isn't it? Much less that the Thilert. Also I have seen a Europa with the WAM engine. It belongs to one of the members of the PFA strut i attend. G-WWWG Look it up on G-info it is a fantastic piece of engineering.

Also the 4 and 5 cylinder versions develop more than the Thilert's 130hp. Such output is not really practicable in a 172. A 152 maybee, but no matter what thilert say, it is not enough.

WF.

[IO540]

Say again s l o w l y

I agree that diesel engines are the immediate way forward - but it won't actually happen in numbers until you get the retrofit market, and that will wait until the cost falls to not much above the cost of a factory overhaul of the avgas engine being replaced. Much of this is in the flight training business and much of that is nearly bankrupt.

It will happen OK in new planes, e.g. the diesel DA40. With FADEC this is the way to go right now. If I was buying a DA40 I would buy the diesel version. But how many new piston planes are being sold today? Arguably the best all-round 4-seat modern IFR tourers today are the DA40 and the TB20, and what are their non-USA sales? Very low, probably less than 50 units in Europe in total, annually.

Americans have cheap fuel so they aren't bothered. Without the fuel price differential, very few people will pay the extra money.

[Say again s l o w l y]

IO540, I think you have hit on the heart of the problem for Diesels.

I would love to have Diesels in our Robin 200's, especially as they are both coming up to engine changes, but I don't think it is financially worth it at the moment.
It seems to be a chicken and egg scenario, with people waiting until the price falls, but the price can't/won't fall until more units are sold.

That damn, cheap Yankee fuel stuffing it up for the rest of us again!!:p

Are the Diesels car based engines?

[ShyTorque]

Modern aviation diesels are not car derived but specifically designed for aircraft, to run on Jet fuel. Even if the specific fuel consumptions were the same, the fuel costs in UK would be less than 1/3 of that for an engine running on AVGAS / MOGAS. In practice it is even less than that.

The Wilksch engines are two stroke, 3 cylinder turbo-charged units. Two strokes can be made smaller and lighter than equivalent 4 bangers because they have twice as many power strokes and so produce more power per unit engine size.

[shortstripper]

I think you may see more and more diesels appearing in permit aircraft. Wilksch don't seem to have it yet though ... very expensive and as yet no longevity proof. In view of R and D costs for expected returns, don't hold your breath re aircraft manufacturers. As has been pointed out, without the US market, there's not enough profit to be made.

IMHO it's the homebuilders and a good auto conversion that will prove the way forward with diesels. I have an engineering friend who is keen to come up with something as his own personal challenge, I wish him luck. I for one would welcome a small diesel in the sub 100hp weighing little more than a VW or Cont as we have nice cheap red diesel here on the farm. Trouble is, most diesels weigh more plus they all need a starter and big battery. No weight saving by hand propping will work here :{

IM

[zalt]

ShyTorque - I thought the Thielert engines were modified Merc A class engines.

[ShyTorque]

Zalt,

You may be right, it's not a type I have any knowledge of. :ok:

[WelshFlyer]

The Thilert engines are Diesel car engines. Heavily modified I'll give them that, but none the less. I think that no matter where aircraft are being sold, the problem is that Cessna own a significant number of shares in Lycoming. And because of this it is in their interest to use their own drives. If Lycoming produced a compression ignition engine we'd be talking, but I feel there is a better chance of pigs flying than a Lycoming diesel.

[knobbygb]

Everything else I've read on the subject seems to point to the continued availability of leaded fuel being one of the important factors in this. Is 100LL really going to be available for the next 20 odd years? I understand it's the only leaded product still supplied and that the oil companies aren't particularly keen, especially with the very small size of the market. Is this really going to be a problem?

Also, out of interest, are the diesels generally noisier or quieter than the current engines, or is there little difference?

[Croqueteer]

The "Diesel Air" engine in a Luscombe at the PFA rally was impresive in performance and in the fact that it is designed to "plug in" in place of current C90s and 200s. Nobody has mentioned that diesel and JetA1 are far safer fuels than avgas. Red diesel is also relatively easy to buy and store.

[Wee Weasley Welshman]

It is time for the ancient and desperately polluting and unefficient Continental and Lycoming to die. I suspect emissions regulations and AVGAS availabilty may prove the death knell.

New aircraft sales are going to be (outside the US) dependent on offering a good FADEC diesel option. After a while the Hank will notice that those pesky Europeans are flying really quite clever aircraft that burn 70% less fuel. At that point Cessna or someone will probably buy the major dieselaero engine manufacturer and bingo.

The Diamond diesel twinstar looks like an IR training wet dream. It always bugs me that we train people one week on a 30yr old American designed dinosaur Senecca and the week after put them in an A320.

GA aircraft need to catch up and become cheaper. An all composite FADEC diesel powered EFIS integrated GA range of aircraft will invigorate GA itself. Lets face it - most trial flight type people are amazed at how basic and crude your average GA craft is.

Compare the latest Nissan Micra to your avergae Cessna. Its pathetic.

Cheers

WWW

[big.al]

al - surely the savings would be much greater than that?
Send Clowns - yes you are probably right, I was only guessing a conservative cost of 25% of current values (i.e. 75% saving). Could potentially be a great deal more as the fuel burn is probably a lot less per hour.

Compare the latest Nissan Micra to your avergae Cessna. Its pathetic.
WWW - dead right, the average Micra has a much shorter take off distance;)

[WelshFlyer]

Noise is generally a bit less than LL100 engines, they also run more efficiantly because of the"Full authority digital control" something that I have mixed feelings about. In a way it's a good idea, on the other hand it's not so good because it removes a certain degree of engine control from the pilot - it's kind of like a "fly-by-wire" for the engine - you don't control the engine, you tell the FADEC to controll the engine.

WF.

[IO540]

WelshFlyer

Can you elaborate on how FADEC is a bad thing? I assume you refer to the lack of an RPM and mixture lever. Why would more control be useful?

I know there is a reliability issue due to a more complex system.

[Say again s l o w l y]

With a large number of engine problems being due to operator error, I can't see the argument against FADEC.

Airline pilots love FADEC, it can stop you making a complete a*se of yourself on the odd occassion!!:O

[tacpot]

The only real issue with FADEC for light aircraft is reliablility/redundancy. On an airliner you can afford to have sufficient redundancy in the systems because you are carrying 100's of fare paying passengers. On a light aircraft, with an new engine already costing tens of thousands of pounds, can you afford to put sufficient redundancy into FADEC?

My view is it better to sell an engine with two FADECs for £22,000 than with one for £20000. If the customer can afford your engine they can fly safely. The cost isn't in the hardware, it's in the R&D and certification. Better to release a product that will sell for many years because it is reliable and that recoups the extra R&D and certification costs, than have an product that only sells a few units because a few fail in service early in the life of the product, so that you never get back any R&D or certification costs.

[WelshFlyer]

I bet airline pilots like fly by wire as well:\ My main problem with FADEC on a light aircraft is an issue of simplicity - a carburettor might have parts that wear out, but they are not dependant on 5.5volts being generated by an alternator and then reduced by a control circuit. That's a hell of a lot of components to go wrong:( The question is can light aviation needs ever justify the develpoment of FADEC? It isn't really needed, diesels have been around for a while before FADEC was invented.

I'm dubious about FADEC because it isn't "tried and tested" Dual-channel FADEC would make me feel a little more comfortable, but imagine the regulator blows up - you'd be left without an engine in a situation that would normally be ok, (if the instruments were undamaged)

Now, a drive with the option of being able to run with out the FADEC system running, would be a plus - the efficiancy of FADEC with the possibility of dis-engaging it in certain situations.

[White Bear]

know you have to deal with what you have, but everyone should understand that the whole fuel cost thing is directly controlled by the Government, and their respective countries tax rates.

Small diesels do not have a wonderful reputation for longevity over petrol, in small cars or anywhere else, given the same duty cycle. They are about 10% more fuel efficent, but the fuel it's self is heavier, never a thing to be taken lightly (pun intended). If you continue to wax lyrical about diesels, and forget the advances made in petrol engines you are missing the point. My car for example can climb higher than my Cessna, and I never need to adjust the mixture. the plugs last 100,000 miles or about
2000 hours, the oil change interval @ 10,000 miles or 200 hours. Compare that to the recommeded fuel injection system maintenance schedule and cost of that, and you will get a shock.

Old engines have old technology, petrol or diesel, and new petrol engines with FADEC are more efficient than ever, and just as long lasting as a diesel, but without all the diesel problems of high pressure fuel injection systems, filter problems, hygroscopic fuel, weight etc, Do not forget that diesels are inherently more expensive to build, and the maintenance costs over the life of the engine are much higher.

Before one commits to a diesel conversion, one should look at the cost of a conversion to a modern petrol engine with FADEC.
Just my HO.
WB.

[ShyTorque]

It might well be that governments will sound the death knell for the aviation petrol engine by legislating against the high lead content of the fuel they use. The problems of using MOGAS as an alternative are quite limiting in some respects.

Once the technology of aviation diesels is well tried and tested, the unit costs will decrease to a more affordable level.

[Say again s l o w l y]

I very much doubt any engine or modification would be certified if by a small failure in the electrical system you would get a total engine failure or loss of control.

I'm assuming that there would be a fail safe mode and I thought I'd heard that there would be 2 alternators driving seperate electrical systems to try and counter any probs.

Not sure about the popularity of fly by wire, never having flown any a/c with it (apart from on my PC that is!), I wouldn't really want to make any judgements. I doun't really like the principle, but it does allow lots of interesting designs of 'reduced stability' and that sounds like fun!!

[IanSeager]

The question is can light aviation needs ever justify the develpoment of FADEC?

A bit late for that question. The Thielert Centurion fitted to the certified DA40 and STC'd for the C172 and PA28 has FADEC with dual ECUs. The throttle has no mechanical connection to the engine at all.

Ian

[WelshFlyer]

This may sound a bit cheeky of me, but: Are you the Ian Seager that test-flew the Thilert engine in the C172 and PA28 for Flyer magazine?

[IO540]

WelshFlyer

Electronics as such is actually extremely reliable. What makes the electronics you get in GA aircraft not reliable is poor mechanical construction (ignorance of the vibration and humidity environment) and occassionally bad design in the first place. The latter can be various things but thermal cycling is a bad thing - nowadays one can design most things such that they run very cool so that's not an issue.

For some reason you can pay US$80k (list price) for a 3-servo autopilot system and everything in it is open to the elements, so if the plane is parked outdoors it will suffer badly from corrosion.

Obviously electronics needs to be designed to withstand the voltage surges coming out of the alternator when its load varies suddenly, etc.

The car makers learnt this stuff 20 years ago. It isn't rocket science.

I would be quite happy with a FADEC system which has been properly designed and built. And if one has two of them in a dual-redundant configuration that helps a lot (not as much as some people might think though, especially if both are identical units with identical software :O )

Re FADEC on an avgas engine, I don't think this would save much fuel (on a correctly operated engine) because once you run at or past peak EGT (lean of peak) all the fuel is getting burnt and for an engine optimised for a given cruise power setting, any further savings are second order only. These engines may be 1950s but they are pretty efficient once running at the right point. But FADEC would save a lot in a typical wet self fly hire / flying school type operation, 20% easily.

[englishal]

Give me a diesel (or two) with FADEC any day. The advantages outweigh any conceived disadvantage in my book.

Cheers
:D

[Spiney Norman]

Here's a question for any engineers out there. I've often wondered if the much greater torque a diesel would provide actually would improve take-off performance, and not, as IO540 said, make it worse. Haven't seen any field performance figures quoted in comparison. Anybody know?

Spiney

[Wee Weasley Welshman]

Fiat are reliably making a second generation direct injection diesel that runs at fuel pressures of 1700psi in an all alloy engine sporting 4 valves per cylinder. It does 70mpg and goes like stink.

If Fiat can manage to mass produce that with enough reliability then I think we can come up with something for light aircraft.

I'd prefer to have tanks full of diesel when I come off the side of the runway and wrap it around a tree - if nothing else thats a major major advantage.

Diesel might be heavier but there is actually more calorific energy in it so for the same efficiency you need to carry less fuel. Carbs are inefficient ancient technology that often as not cause half the engine problems that cause heart stopping moments (engine stopping in stall etc) and accidents (carb ice - plug fouling). Direct Injection diesel gets rid of all of that plus all the snags and failures associated with the Magnetos and Plugs.

I don't know this for sure but isn't torque more use than horsepower when it comes to GA use? Prop RPM varies only over a narrow range and the actual acceleration rate of that variance is not that critical. More torque though equals more pitch on the prop which equals more bite in the air which equals greater thrust - doesn't it. With diesel generally providing more torque and less horsepower than a petrol are they not naturally more suited to GA applications?

As red diesel is available for boats then surely it would be available for light aircraft? In which case bring on the 60p a gallon - 4 gallons an hour cruise... Now that would have a lot of implications - I'd consider commuting by air straight away.

I would have no problem with FADEC. My car has it and the manufacturer pumps out nearly a million a year and the failure rate is off the scale of statistical likelihood. In fact BMW used to have 3 times the throttle failure rates with conventional systems than they now see with an all electronic system - according to my service manager.

I know that in my limited 2000 GA hours I had 3 throttle failures - 2 coming off in my hand and 1 failing in a mid position requiring a glide to land.

Bring it on I say.

WWW

[IO540]

Spiney Norman

I didn't mean to say diesels have worse takeoff performance. A 200hp diesel plane will have the same performance as a 200hp avgas plane, at sea level, and both with CS prop.

A diesel of the same HP may have lower prop rpm (i.e. more torque) but you fit a suitable prop which makes use of the extra torque, that's all. HP = RPM x Torque.

What I was getting at is that some diesel conversions are of lower HP than the original engine on that plane. So your takeoff performance MUST be worse. The diesel is normally turbocharged however and as the original avgas engine normally isn't, the diesel generates more HP (the plane will perform better) once past a certain altitude, say 8000ft.

[ShyTorque]

WWW,

The point with these engines is that they use Jet A-1 fuel, not "diesel" fuel as we generally understand it. This means that fuel is very widely available at airfields and costs just 39p a litre so you don't have to go to the garage with your can as you would for MOGAS!

Torque is what turns the propellor.

Power = Torque x RPM.

We just need good torque, not high prop RPM, that is why GA engines are large capacity, slow-revving lumps. Diesels are ideal for our low-revving aircraft props because they provide better low-speed torque than relatively low compression petrol motors.

Another advantage is that they have no mixture control like a petrol engine, because the diesel actually has an unthrottled intake, it's just the amount of fuel injected that controls the power output. This means that at low power settings they run very weak and at higher power settings they run richer, but at very good volumetric efficiency at all settings. This is why their low power (cruise) fuel economy is so good.

Because there is no carb venturi, there is no carb icing! Turbo-charging is ideal for them because a smaller, lighter engine can be used and the torque rating can be maintained at altitude.

I'm not sure if Jet A-1 has a higher specific energy content than AVGAS though, I think it might actually be slightly less

Ah, IO540 just beat me to it with his post! :ok:

[Say again s l o w l y]

According to my notes from the dim and distant ATPL exams(why have I still got these things!), AVTUR does have a higher calorific value than AVGAS.

[ShyTorque]

If that is the case (I'm sure you're right, I do know that road diesel fuel has a higher calorific value than petrol), then the higher Specific Gravity of Jet fuel (~0.8) against AVGAS (~0.72) is offset by the extra energy available, so there ought to be little or no overall performance disadvantage in changing the fuel type.

Actually, because of the better specific fuel consumption of a diesel, there should be a net performance gain because it would be possible to carry less weight of fuel to go the same distance.

Just the cost and TBO issues to be resolved then? Oh yes, and the black smoke going up hills... ;)

[Wee Weasley Welshman]

Now thats a point I am unclear on - are they talking about commercial diesel or Avtur/JetA1 ?

Everyone seems to refer blithely to 'diesels' but it would make far far more sense to use the infrastructure in place for JetA1.

Can someone please clarify?

Cheers

WWW

[ShyTorque]

WWW,

I say again: Jet A-1!

[WelshFlyer]

The reason they call them Diesels is because they are Compression Ignition - but they have nothing to do with commercial diesel exept that they share common architecture - the thilert is a modified car engine.

[Wee Weasley Welshman]

Fine - makes sense. Hadn't really put enough thought into it.

Cheers

WWW

[A and C]

Something that has been missed by all above is that all the new Diesel engines that are under development use VP props and are mostly being fitted to aircraft that had fixed pitch props.

It is my understanding that the thilert engine produces 135 BHP but the take off performance when fitted to a PA 28 or Robin DR400 is about the same as the 160BHP fixed pitch Lycoming.

This can only be down to the prop working better at a low TAS , as the TAS increases towards the best TAS for the fixed pitch prop the Lycoming engine aircraft will have the advantage in climb performance untill it reaches its full throttle altitude once this has happend the turbochager on the diesel will slowly gain the advantage as it can maintain full power to a greater altitude.

A normaly asperated engine can only maintain 75% power (high speed cruise) to about 8000 ft so above this altitude the diesel will become the best option as the higher that you fly the better the TAS.

As a guess I would think that the best cruise altitude would be about 10-12000 ft.

All I now want to know when can I buy one to fit in my DR400.

[IO540]

As a guess I would think that the best cruise altitude would be about 10-12000 ft.

Why not a lot higher? Most turbocharged avgas planes have a 25000ft+ ceiling and the sales brochures like to quote TAS figures at FL200 or so - obviously they are pretty impressive :O

I suppose that a diesel replacement engine aimed at the lower end of the GA market would have a smaller turbo, perhaps...

[Say again s l o w l y]

Unless everyone is going to retro fit oxygen systems, I hope they are optimised for flight below 10k, TAS figures for a C150 at FL200 would be pretty meaningless!

[LowNSlow]

I thought that one of the factors which has delayed production of aero diesel engines is the requirement to use AvTur (jet A-1). This is obviously a good thing as there is an existing infrastructure to supply this fuel at a lot of airfields. One major difference between road going diesel and AvTur is that AvTur provides a lot less lubrication to the moving parts of the fuel injection pump. Unsurprisingly AvTur is chemically designed for turbine engines which do not rely on their fuel for lubricating critical parts of the engine. Most former vehicle pumps are set up to run on the ground bound diesel and for certification purposes have had to be shown to be reliable on AvTur.

I sit waiting to be corrected on the above :D

PS If the trusty Cirrus in my Auster went phut I'd prefer to fit a WAM-120 inverted inline engine rather than a flat four Lycoming. The reason for not doing it is, of course, cost..........:sad:

[IO540]

Say again s l o w l y

I agree entirely regarding FL100+ not being very useful in Europe (due to the airspace structure and the difficulty of getting the necessary JAR IR).

But oxygen as such is not a problem; you can get portable packs for a few hundred quid which are perfectly good and (unless the plane came with oxygen fitted - that would be a very upmarket turbo model) preferable because no inspection is needed whereas a fixed oxygen system adds some 1k or more to the CofA annual cost.

I am not sure if you are tongue in cheek re the Cessna 150 :O Would a private owner of a £10k-20k plane spend money on a diesel? Only a flying school putting 500+ hours a year on a C150 would consider that, even if they had the money.

[A and C]

You are wrong about the lubrication issue the jet A1 fuel is used to lubricate the whole fuel system on a turbine engine as well as some of the valves for bleed air control and turbine/ rotor active clearance control.

You are correct to think that a fuel pump that was ment to work with diesel oil will not last long using Jet A1.

The fuel control units on jet engines have longer TBO,s than the makers of piston diesel engines quote for the whole engine so I dont see fuel control as a technical issue.

[Say again s l o w l y]

Definately tounge in cheek! Having a portable O2 system is all very well, but PPL's without an IR will never get near 10K, let alone FL250!

It seems to make more sense to buy new a/c with Diesels than to retrofit an old knackered airframe with a state of the art engine.

3 years ago we bought some brand new a/c and compared to our existing fleet of Cessna, they make a fortune. We have well over twice the use despite the price being higher. There is alot to say for the magpie affect "OOH, shiny!"
So we are seriously thinking about replacing whats left of our old fleet with some modern tackle. A risk, but maybe worth it in the end.

Our most recent aircraft are coming up for their first engine changes and I would love to get rid of the shonky old lycomings. We have had huge problems with the engines, from starting, magnetos, spark plugs, fuel pumps etc etc. One a/c had to have a top end rebuild after less than 1000hrs. A plainly rediculous situation. The amount of money lost in down time has been considerable, so I am all for Diesel engines, even if all they do is create some competition and force the main manufacturers to buck up their ideas, which are really quite laughable.:mad:

[Volume]

brand new news :

Tonight FAA has finally validated the german JAR-E type certificate for the Thielert TAE110 / Centurion 1.7 per FAR-33.

So this engine is aviable to the general aviation in the U.S. now.

[Lowtimer]

PPL's without an IR will never get near 10K, let alone FL250!

Huh? Maybe not FL250, but we're not all stuck under London airspace, you know. Flying around East Anglia and going up and down eastern England to North Yorkshire or Northumberland you can often benefit greatly from going high - pick up a mighty tailwind, see the sights, avoid all the rest of the GA traffic scudding around at 2000 feet, see any higher-level traffic more easily due to being above the haze layer, and have lots of options in the event of engine trouble. This summer there have been many suitable days for flying up at 8, 9 or even 10 thousand feet, especially in an aeroplane with a good rate of climb. Got the Yak from Sywell to Bagby with a true groundspeed of 165 knots point to-point one day, not bad with only 210 km/h on the ASI. Mind you, the price of the mighty tailwind in one direction is often that I have to scud along at 1500 feet to diminish the headwind on the opposite leg, or I'd never get there.

[Say again s l o w l y]

Maybe a bit of a sweeping statement, but the vast majority will never get above 5k let alone 10. Being in east anglia means that we do try to take advantage of altitude, but many people fell very uncomfortable above 5k in a 'normal' light a/c. Yaks are a very different proposition, anyway you can't fit a diesel on a 52!

[IO540]

S.A.S.

"Definately tounge in cheek! Having a portable O2 system is all very well, but PPL's without an IR will never get near 10K, let alone FL250!"

Want a bet? I've been to FL150 as a "PPL" (my IMCR is no good in e.g. Spain), and O2 is highly desirable at FL80+ or FL50+ at night. I agree one can't do it much in the UK but one arrives a LOT less tired after an hour or two even at FL50 if using O2.

"It seems to make more sense to buy new a/c with Diesels than to retrofit an old knackered airframe with a state of the art engine."

Absolutely! I know some people here will think "yes but most people never go to anywhere one could use the altitude", but if you talk "new a/c" then you are looking upmarket already, in respect of both self fly hire and owner pilots. A lot of this stuff is tied up with people being able to get into interesting flying, going to far away places which one cannot drive to in an hour.

"3 years ago we bought some brand new a/c and compared to our existing fleet of Cessna, they make fortune. We have well over twice the use despite the price being higher. There is alot to say for the magpie affect "OOH, shiny!"
So we are seriously thinking about replacing whats left of our old fleet with some modern tackle. A risk, but maybe worth it in the end."

I think you may have accidentally stumbled onto a major reason for the decline in the PPL training industry :O Investment in new modern planes (and I don't mean new Cessnas) is the way to get things moving - anyone who is well outside GA sees this right away.

[Say again s l o w l y]

O2 is good to have in many situation, but I know of very few people who have gone to the expense of getting oxygen and not got themselves an I/R so they can use it more readily.

It wasn't an accidental stumble by any means. We have a very profitable business and have invested in many ways to bring the standard of a/c and facilities up to something approaching a decent level. I personally trained with BAe and ever since then hate to see shonky old planes and tired old portacabins. In the end I feel they are a false economy as they put more people off than anything else.

Our prices are not the cheapest, but I do feel we give the best value for money, I mean paying £100/hr for a horrible aircraft. I wouldn't so why would anybody else? For example, our main 'touring' aircraft were 2 C172's which were in very good condition, but 6 months ago we aquired the use of a very nice TB10 and suddenly the 172's are idle whereas the TB is flying constantly, despite the fact it costs £18/hr more.

The new Cirrus's and Diamond a/c are fantastic and I for one can't wait until we get a fleet of these. But that isn't going to happen overnight unfortunately!:{

[shortstripper]

Forget the altitude bit ... It's the economy that I like the idea of :D BTW, many gliders/motor gliders and light aircraft attain 10k quite easily ... so why the IR? ... don't answer that, I know what you mean, but it's just too much of a blanket statement not to give a tounge in cheek comment back:p

I'm working on a T31 motorglider conversion, it's powered by a VW1700. If I could convert one of the new generation of light diesels to power it ( I only need 40-50hp ) I could fly for virtually nothing as I'm based on my own farm strip with a tank of red diesel not 200 yards away :)

Also, a turbo charger does not mean the engine only develops its power at high altitude ... it just means that the power will be maintained up to a higher altitude than a non turbo engine. If you are saying that a turbo diesel is only worth putting on if you plan to fly high, then I'd like to know why? That said, I can see sense in the argument that a retro fitted diesel is only a saving if your engine needs replacing anyway or you buy a new aeroplane with one fitted. After all, it would take a good many hours to make up the cost in saved fuel.

As the question was would I fit one by choice ... then my answer is a resounding YES!

IM

[A and C]

I think that you have rather missed the point with regard to the fuel, the new diesel engines that are coming on to the aviation market will NOT run on red diesel oil the aim is to use Jet A1 and have a common aviation fuel.

All the new engines are turbocharged and so will maintain power to an altitude well above that of a normaly asperated engine so one would be foolish not to take advantage of the extra speed at alititude.

Most of the engines offer a 30% decrease in SFC but are expensive to buy so the aircraft will have to do a lot of flying to make financal sence.

I can see the SMA and Thilert engines doing rather well as the engine makers are getting into both the new and retro-fit market , I have my doubts about the wilksch engine not from a technical point of veiw but from a business stand point it seems to me to be an under funded cottage industry that is unable to take advantage of the potental growing market , however I hope that I am proved to wrong about the Wilksch engine.

[shortstripper]

A and C,

I don't really think I missed the point. I was just looking at the other end of the scale. There is nothing wrong with the idea of a small car diesel conversion that will run on red diesel ... is there?
If you read back through the thread you'll see that that is kind of where we started ... we just ended up talking about avtur verses diesel. I really rather think that once you get to the higher performance twins ect, you'd be better off retro fitting a turboprob anyway. Also a normal diesl with a redesigned pump sounds like it might work OK on avtur as well, although I'm not sure on that score?

For smaller training aircraft a 100-150 hp turbo diesel would be fine. For that a car diesel conversion is quite possible and has been done quite successsfully with a Citreon engine already.

In my case a 50 hp diesel weighing about 180 lbs would be fantastic for reasons already stated. With some of the new generation of aluminium diesels powering tiny cars, it's only a matter of time before one is found that would be suitable to convert.

I do see where you're coming from and agree to a certain extend. Certainly for a new generation of training or light touring aircraft, a new generation of avtur burning engines really should be developed and I suppose are being. However, as for retro fitted these engines? ... they need to be a lot cheaper to make sense. In the meantime and before any new generation is mass produced enough to be cost effective, I think it would be more sensible for someone to find a suitable car engine and do a good conversion. If successful there'd be a very good market for either the conversion kit, or to have the converion done and fitted.

IM

[Saab Dastard]

Isn't the UK MoD aiming for a "Single Fuel" solution for battlefield use encompassing road, off-road and air use and AvTur is the chosen fuel to simplify logistics?

Given that this is the case, surely they will want to extend this as far as practical to have a single fuel for training purposes also - so perhaps this will give some impetus to equip the RAF with diesel-powered trainers.

This might help to accelerate the adoption of diesel engines and break the "chicken and egg" situation of cost vs. volume.

Just a thought.

SD

[Arclite01]

I hardly think that the number of trainers the RAF would buy would make any difference to the cost arguements - it's a totally different marketplace.

Arc

[ShyTorque]

I think the CAA would be very unhappy to allow the use of red diesel for aviation, because the regulations for its storage are not as strict as for petrol.

There is a very real quality problem with fuel that is not subject to daily water checks, for example.

Call me picky if you like but I wouldn't be personally happy to fly in any aircraft powered by fuel that has possibly sat in a farm tank for a few months.

AVTUR from a regulated source has to be the only way to go.

[Say again s l o w l y]

Saab,

Many moons ago, all the NATO countries wanted a complete fuel solution with all vehicles using the same JP8 fuel, including motorcycles, anyone remember the armstrong diesel motorcycle?

Not sure if it is a current issue with the MoD however.

[shortstripper]

"Call me picky if you like but I wouldn't be personally happy to fly in any aircraft powered by fuel that has possibly sat in a farm tank for a few months."

Are you joking? lol .... The fuel in our farm tank is lucky to last a month! Modern farming ain't like "The Darling Buds of May" image of old!

Red diesel is perfectly clean too ... If anybody thinks a farmer or fisherman is going to stand for poor, contaminated rubbish, they are deluding themselves. The main issue if any, is in making sure winter diesel is available in the summer. Summer diesel is likely to freeze (not quite the right term, but will do for illustration) in very cold temperatures. If flying very high this might be an issue. Winter fuel has an additive, or rather is brewed to freeze at a lower temp than summer fuel ... it's a kind of halfway house between diesel and household heating "oil". I guess it wouldn't be to hard to standardise a best suited diesel with enough demand ... but then I bet that would the attract tax!

IM

[ratsarrse]

Engine management is a real culture shock when you first start flying. When I first learnt to drive, I had a car with a manual choke and a carburettor. It was built in 1980, but even by then it was starting to look archaic. The next car I drove had an automatic choke. The last three cars I've had were fuel injected. Since Honda introuduced the VTEC engine, not one of them has failed.

When I climbed into a PA28 for the first time, it had magnetos (when did a car last have magnetos), a mixture control, a carb that can get iced up in just about every weather situation you get in the UK, used leaded fuel that costs a fortune, and needed maintenance on a scale that made your eyes water. It had the excuse of being 20 years old, but if you were to buy a brand new PA28, it would be exactly the same. Frankly, it's a disgrace. It does the industry a huge disservice to inflict aging and substandard equipment that was abandoned 20-30 years ago by the car manufacturers on consumers.

[WelshFlyer]

When I climbed into a PA28 for the first time, it had magnetos (when did a car last have magnetos), a mixture control, a carb that can get iced up in just about every weather situation you get in the UK, used leaded fuel that costs a fortune, and needed maintenance on a scale that made your eyes water.

Cars don't really need the reliability of a magneto - much less a pair of magnetos. Take a look the ignition systems from cars from the last twenty years - lots of moving parts and dependent on the alternator.

With an aircraft, using magnetos is favouable - I think people who have converted car engines in their A/C retro fit magnetos. They are lighter, more efficient and have lower fail-rates.

As for carbs - have you flown a C172SP? They use direct-injection technology not diss-similar to your Honda.

Carb-icing is something that really P***s me off as well. The A/C Manufacturers know this is an archaic system and are replacing it with a much more eficient component.

My Problem is with FADEC - apart from this I think these Diesel engines are fantastic, who would not want a £6 per hour drive?

WF.

[Say again s l o w l y]

Welshflyer,

Are you kidding? Magnetos lighter and more reliable than an electronic ignition system? I don't think so. If they were a better system, why on earth do we not still use them on cars?

Please have a proper look at the modern systems, you will see that apart from rumour and innuendo about computers taking over from pilots, I think you'll find that modern systems, ESPECIALLY FADEC, have made life much better in the commercial world in terms of operability and component life.

There will never be a system fitted that is completely fool proof, but it is extremely unlikely that there won't be any fail safes or redundancies built in.

People usually remove the ecu's from the car engines because there are many different and unnecessary systems in a car compared to an aviation installation, and instead of going to the expense of having an ecu reprogramed they just replace it. This also allows for redundancy, since car ecu's generally don't have any, unlike a similar system that would be specifically designed for an aircraft.

[IO540]

WF

Cars don't really need the reliability of a magneto - much less a pair of magnetos. Take a look the ignition systems from cars from the last twenty years - lots of moving parts and dependent on the alternator.

This is true but in fact if an ignition system were to be duplicated (which on an aircraft it normally would be) the overall reliability (i.e. the probability of at least one working) goes up astronomically.

The dependency on a single power source is trivial to address: a small backup battery.

Also, car makers have had decades to learn exactly what tends to pack up, and they have been free to address it as necessary, with no certification issues. The only thing which has ever stopped them achieving aerospace reliability levels has been the fact that everything has to be dirt cheap.

I believe that the only reason we still fly this WW2 c**p is not certification or anything like that; it is the Cessna/Piper near-monopoly ensuring there is as little innovation as possible; the utterly conservative U.S. market, with their cheap fuel; pilots have long ago got used to this state of affairs, and anyone entering this field via a flying school (which is just about everybody) has never seen anything better, so they accept it.

[WelshFlyer]

I believe that the only reason we still fly this WW2 c**p is not certification or anything like that; it is the Cessna/Piper near-monopoly ensuring there is as little innovation as possible

Then why would they go to the trouble of developing the fuel-injected engine in the 172SP?

Technology is profitable. Most of the adverts when the 172SP was launched made a big thing of the fuel-injection. It sold qite a few aircraft that's for sure!

I think when they get it into their numbskulls that compression-ignition is the way forward, i.e. when people start retrofitting with Thilert engines, they will jump on the band wagon. Cessna and Lycoming are part of the Trexton Cessna company - they will (of course) start fitting their own brand of compression ignition units.

While we're on the trend of ignition systems; dose the 172SP have electronic ignition? I was under the inpression it had a CDI system instead of mags.

WF.

[IanSeager]

Welsh Flyer

Sorry for being a bit late, but yes, that's me I'm afraid.

Ian

[ShyTorque]

Shortstripper,

All you have to do then is to convince the CAA (and pay them) to approve your red diesel fuel and installation for aviation use and subsequently operate it to their requirements.

P.S. don't forget to tell HM Customs & Excise or they might confiscate and crush your aircraft, like what's recently happened to certain illegally operated cars near where I live... LOL

[Rod1]

I used to fly an AA5B until a few weeks ago. It uses 9.5 imp GPH at 75% power giving 120 – 125 k. Six years ago I was purchasing Avgas at 52 ppl, it is now 99 ppl. My AA5 was already costing just under £40 per hour in fuel. If the cost continued to increase over the next six years, which seems likely, I would end up paying £80 + per hour on fuel!

Almost exactly one year ago I started looking at alternatives. Converting the AA to diesel was possible, but the cost was about £40,000! Permit aircraft seemed to offer significant savings, but several very large problems appeared.

Firstly, I tend to get off the beaten track a lot. I soon noticed that very, very few of my common haunts had Jet A1. Almost all had Avgas, and an increasing number had petrol by arrangement.

Secondly, most of the engines did not seem to have been widely tested in the air. I was very unhappy about being somebody’s unpaid test pilot.

The Diesel engines were too heavy for the more modern designs. Even if they did fit, there were c of g and useful load issues.

Questions to PFA Engineering, showed that the Rotax 912 is the most reliable engine in the PFA fleet. My new 912S is arriving in 4 weeks, total cost £8500 inc. vat. It will burn £12 of petrol an hour at 125k in my late 90’s designed composite, which will also de rig to save on hangarage. It think it unlikely petrol will increase too rapidly in cost over the next 10 years, given that the last time they tried it, the country ground to a halt.

A year later, I remain certain I made the right decision. I can count the number of aircraft I have seen flying on diesel power on the fingers of one hand. In perhaps another 5 years or so, the numbers will have increased and the hours flown will be reasonable, but there still remains another problem. Most of the aircraft which will fit diesel engines over this period, will have been designed in the 50’s and 60’s. For diesel engines to come good, people need to design modern airframes around them or their weight needs to reduce, which would solve some of the design problems, but both of these scenarios seem some way off.

Rod1

[shortstripper]

"P.S. don't forget to tell HM Customs & Excise or they might confiscate and crush your aircraft, like what's recently happened to certain illegally operated cars near where I live... LOL"

You may be right? However, the law is quite specific when it comes to using red diesel in cars on the public highway. There is nothing specific in law about its use in aircraft with regard to tax so I think they'd have a hard time trying to nab your aeroplane for using it. The PFA (who would have to seek CAA approval)would have to approve its use for homebuilds I suppose to be properly legal. There is talk of a new experimental category coming in (this is a rumours network) if it does, then diesels in experimental a/c would be OK for sure.

IM

[A and C]

I,m not sure that red diesel is the way to go for your woodern airframe.

The red diesel oil would do a lot of damage if it soaked into the structure.
I have the feeling that Jet A1 would do a lot less damage but I dont know of any turbine engine woodern aircraft so cant be sure if this is a problem.

[delta96]

<The red diesel oil would do a lot of damage if it soaked into the structure.
I have the feeling that Jet A1 would do a lot less damage but I dont know of any turbine engine woodern aircraft so cant be sure if this is a problem.>

De Havilland Vampire?

On the subject of OX for high flight, would the new composite structured a/c lend themselves to pressurised cabins up to FL150?

[shortstripper]

Dehavilland Venom was wood skinned:ok:

I'd hope not to have a fuel leak bad enough to do damage in the first place! There was a Jodel fitted with a Citreon diesel in one of the popular flying mags last year ... or was it PFA mag? ... I can't remember now.

IM

[WelshFlyer]

Wow! Ian, what's your opinion on Cessna/Lycoming developing compression-ignition engines?

Also, a question I have; Would you buy a diesel for your own A/C?

Wf.

[GTOTO]

Would I buy an Aero Diesel absolutely.

The better question is why would you fit an Avgas engine.

There is absolutely no advantages, only disadvantages.

On a 200hp Lycoming burning 35/40 ltrs/hour with a
2000hour TBO, the saving is about £60,000 pounds over this period and that's only on the fuel.

Most of the new Diesels will probably go to 3000 TBO, with field experience, even more savings.

Range increases will be 50 to 100% on the same tank size also.

There are 5 Aero Diesels I know off, flying or in development.

SMA, Thielert, Zoche, WAM, Diesel Air, Delta Hawk(USA), Continental (been dropped)
and some French automotive conversions.

Two of these designs have a FADEC, SMA and Thielert and are 4 stroke units the rest are 2 strokes with straight mechanical controllers.

4 stroke is not the way to go, really on any Diesel engine, even cars. The marine industry has been using 2 stroke diesels for at least 70 years. So the SMA, for a newly developed engine is really a stupid way to go.
That's why its over weight, has high harmonics and is difficult to cool, as air cooled. Just looks like a high compression 4 cylinder turboed Lycoming and costs 80,000 dollars.

The best is a direct drive 2 stroke, with external scavenging,(no air goes through the crank case) and liquid cooling.

I think the most promising is the Delta Hawk, these are direct drive, liquid cooled, 90 degree V4 turbo/supercharged, 180 degree phased crank shaft, piston ported, loop scavenged 2 strokes (no valves). Comes in upright, inverted and vertical (for Helicopters) configurations

They are priced between $25,000 to $35,000 dollars.
They have 160/180 and 200HP models. Note Lycoming IO360 costs about $32,000 new.
The 200hp weights in at about the same as a 200hp Lycoming IO360. Also will be certified

As this is a US engine, I think it is the most important,
they have a demonstrator flying and are in a similar position in the development programme as WAM.

The Zoche, German is a radial 2 stroke all above of the Delta but air cooled.
The twin row 8 cylinder 300hp model looks fantastic, very low harmonics, 8 impulses per rev. Small round frontal area, these engines need no electrics what's so ever, uses store compressed air through the supercharger for start up. Can go from start, to full revs in 1 second, so has a preoiler fitted as standard.

The 300hp weights about the same as an IO360.
Trouble is, has been in development for 20 years.

We all know about the WAM, inverted inline 2 stroke uniflow scavenging (exhaust valves in the cylinder head, piston ported inlets) all mechanical, electric start. Comes with electronic engine monitor, not needed for operation.

Only concern on the 200hp 5cyl model gives a long crank shaft, could be a bit twisty

Diesel Air UK, have taken the old 1930s Jumo concept, a 2 stroke,
with two opposed pistons in one cylinder, so requires two geared together crank shafts and only has a supercharger at moment, Piston ported inlet and exhaust, but interesting problems with the fuel injectors and burn patterns. Has two injectors each side of the cylinder to give an even fuel burn.

The 100 hp is a 2 cylinder four piston model. Flying in airships and one aircraft.

The Theilert is a 4 cylinder liquid cooled 4 stroke, (means harmonics).
Has a reduction gear box and harmonic damper.
This has to be changed every 1000 hours cost at least £1000, price of two mags.

I believe they went down this route to slave of all the
development in automotive engines and be faster to market. Which they have been, 70 aircraft flying, so there are at least 80 Diesel air power aircraft operational.

Not the count on one hand as mentioned.

So with Diesels you can say good bye to.
Burnt valves, cracked heads, carb ice, spark plug failures, magneto failures, shock cooling, high engine management work load, leaking fuel pumps, cracked exhaust systems and high overhaul costs, just don't buy an SMA if you want to save money.

So again why would you fit an Avgas engine.

[WelshFlyer]

I think that 2-stroke engines are the best kind of engine (blame a motocross enthusiast!) And for diesel (compression ignition) don't need to be the publics perception of belching blue smoke.

Two-strokes with out FADEC excites me - I'm a traditionalist when it comes to "digi drives"

It's supprising to some that the 2-stroke can be really efficient - and less moving parts so greater life.

$25,000 dollars is very reasonable for an engine that's going to cost pennies to run - the Thilert is way too expensive. The WAM is relatavely cheap and is a very viable option for permit machines.

I'm quite excited that there are five manufacturers of compression-ignition engines. Unlike Lycoming, who have the majority of most spark-ignition engines, so many different manufacturers should promote engineering excelence that aviation engines have not had since world war II.

WF.

[Ranger One]

GTOTO:

The best is a direct drive 2 stroke, with external scavenging,(no air goes through the crank case) and liquid cooling

In other words, you're saying the Germans got it right 60 years ago :-)

e.g. http://www.histomobile.com/histomob/tech/2/120.htm

R1

[IanSeager]

WelshFlyer

There doesn't seem to be a lot happening on the Jet A front with Lycoming and Continental right now. They seem to be concentrating on MOGAS solutions.

Most airframe manufacturers are working on diesel options though.

I would happily buy a diesel engine for my aeroplane if/when the price and performance were right.

Ian

[GTOTO]

Yes it would appear so on the German Jumos.

In the 50s the Jumo idea was expanded for trains to be 3 cylinders in a triangle with 6 pistons and 3 crankshaft called Deltic class, if I remember correctly.

On two stroke petrol, the marine out board two strokes now directly inject into the cylinders, so no wasted fuel. So really there is no need for 4 stroke petrol either.

History shows large established companies never innovate.

Only play with what they know about and are scared of killing their own markets. When Lycoming & Continental final wake up, it will be to late for them.

Evolution show, a new concept from a start up will come a long and eat them lunch. Look at Cirrus and Cessna.

And the future 20 years out is a product that will be just on the market now, the problem is guess which one's.

[ShyTorque]

Commer, an English company who made buses, made their own diesel engine in the 1960s, similar to the Jumo design.

It was a supercharged 2 stroke, 3 cylinder, horizontally opposed piston engine. Each horizontal cylinder had two pistons working in opposition to each other, like two boxing gloves coming together with the combustion space between them (a true "boxer" engine, a bit like a VW Beetle engine, but working inwards on itself).

The two crankshaft were connected together under the crankcase into a common output shaft.

A big advantage of this design is that there is no cylinder head and hence no gasket to fail, critical in a very high compression ratio engine.

Perhaps it will be resurrected again one day.

[WelshFlyer]

There is an entry on the Commer in a book I bought at a car boot sale. The book was from the '60s and concentrates on, as the title suggests "2-stroke engine, design and tuning"

Like I said before, two-stroke engines can be very efficient if tuned/engineerd properly.

WF.

[Croqueteer]

On the subject of red diesel, I have a reply from the customs and excise that it is perfectly legal in an aircraft. I also use it in my narrow-boat as it is legal in marine craft.

[Circuit Basher]

Just spotted this (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=2962543145&category=2983) on EBay - that'll help your low level performance a bit!!!

Save having an STC for the installation of a diesel and then one of these - just go for broke and fit this straight off!!! :D :E :ok:

[edited 'coz EBay links seem to have temporarily given up the ghost!]

[Pigasus27]

Good article on diesels in one of the 3 main GA mags this month (can't remember which one, and accidentally left all 3 on train!)

[englishal]

I'm waiting for the PAP Noble Gas Engine to make an appearance, then you could fly your aircraft for 6 months on one "tank" of gas which would cost < 5p :D

EA

[ronbvr]

One for the real techies amongst you; going back a bit, someone mentioned fitting diesels to Robin aircraft.

My club (Lasham) uses Robins as tug aircraft for gliders. One of the problems has been cylinders cracking due to the way this operation is carried out, i.e., a fairly heavy loading on take-off, climb up to 2000' to 4000', then a very rapid descent. To be carried out several times an hour, for several hours on a busy day.

We have some carefully thought out procedures in place to minimise the occurrence thanks to hard brain work on the part of some of our tuggies, but it is still extra detail for the pilots to have to remember.

Can it be assumed that a diesel would inherit a similar problem or does it run cooler? This would, I should think, reduce any sort of thermal shocking on the structure, thus reducing the problem?

Regards

[Flyed]

ShyTorque & WelshFlyer

Commer did make a horizontally opposed two-stroke engine in the Sixties (it was a true boxer design); aeons ago when I was an apprentice mechanic I had to strip one down to see what made it tick – it was actually a nice piece of kit, very well made and very light. What impressed me most was the 'con-rod' which was nothing like a normal piston-crankshaft connecting rod, it was more like a rocker arm and polished to an almost glass finish on the outside because any imperfection would have allowed cracks to form and the pistons to hurl themselves at passing pedestrians. It was quite high revving, but its major problem was that it lacked the grunt (torque) of a four-stroke; not a problem for aircraft engines, though.

Ronbvr

I'm also a tug pilot (Nympsfield) and we use a similar descent technique to you to avoid head/cylinder cracking; in theory, water-cooled diesels such as the Thielert Centurion 1.7 should have no shock-cooling problems as we pointed out in our flight tests, but I think we'd need to try it in the tugging environment to be sure. If it did work, it would make launches a heck of a lot cheaper, though :ok:

Nick

Flyer Ed