The only snag you have with airborne diesels conquering the world is convincing the USofA....

“With diesel engines, all the problems with fuel availability goes away”

From a strictly UK perspective the reverse is true. The problem with diesel engines in aviation is that most will not run on diesel, but use Jet A1. Most small airfields and strips are near a filling station and it is 95% likely you can get Mogas as it is the fuel used by almost all micros and quite a bit of light GA. Very very few will have Jet A1.

The Rotax has been certified for years and will have logged lots of time IFR. The new bread of 4 seaters using the 912 will be much cheaper to run than the old American machines (P400 MCR4s). The next gen home built 2 seaters which are on the drawing boards will give 90kn on 50 hp using industrial engines (mogas or Avgas), with similar lifting power to a Jodel.

Rod1

Not doubting diesel engines at all - I have one in my car - but when you say no temperature problems for diesel, I thought it got waxy when cold (and by cold I mean -10Degc not the considerably colder an airbourne engine's going to meet.

Not questioning what y'all say, just trying to understand it from a position of lack of knowledge :ok:

Depends upon the additives.

Plain, unadulterated Diesel fuel, this is true.

Automotive Diesel gets different additives added at different times of the year, and military and civil jet fuel comes in quite a variety of flavours depending upon where you're planning to go with it.

G

Diesel engine doesn't neccessarily mean diesel fuel and that's why I say diesels are future - they run on Jet A-1, which doesn't have problems until -35°C ;) Plus the engine heats the fuel (at least in DA40D), so once you start the engine, the problem with fuel temperature is more or less gone. Just for information, I think that for Centurion 2.0 limits for Diesel fuel are 0°C for takeoff and -5°C in flight.

Rod1: If you look globally, there is a large trend to eliminate 100LL, mainly because it includes lead, but there are also economical reasons: why produce, transfer, store (remember, you must have seperate trucks & tanks) and sell 100LL to very limited number of customers, when you can sell one type of fuel for ALL aircraft? :cool: Looking more globally than UK (I don't know the situation there), but even some developed (well, that's debatable, but let's stick to the topic) countries in Europe are decreasing supply of 100LL. For example in Italy, it is recommended, but I'd say practicaly mandatory to check for 100LL availability with actual fuel supplier at the airport before making the flight and realising that the only 100LL at the airport is the one in your tanks :ugh:

In the interim, before diesels take over (they are much more efficient, stronger, liquid cooled etc...), I am surprised we haven't seen more FADECs attached to conventional Lycomings and Continentals.

I reckon if you had a one lever operated Lycoming with a computer to take care of power setting and mixture control, you could probably improve the efficiency a lot and possibly reduce maintence costs.

Exactly. Simple engines work fine for aircraft, if comparing efficiency.

Diesels got hit on two fronts: first by Mr Thielert's "little accounting adventure" resulting in its collapse, and second by taxation. In the UK, the financial case for an aero diesel has basically disappeared.

Lycoming FADEC
 

A FADEC is on the way from Lycoming, I would guess that they could reduce the fuel burn by 25-30%, (after all you can see a 20% reduction in fuel burn by fitting a LASOR ignition system).

Lycoming are of the opinion that the problems that require Deisel engines to have dampers fitted are outweighed by the advantages of a MOGAS burning FADEC controled engine.

At the moment I have yet to be convinced of the advantages of the diesel as an aircraft power plant, may be when I do the Thielert course next year I will adjust my opinion.

Compared with flying full rich, sure.

Otherwise they must have invented a whole new branch of physics :)

I can get the same result by flying at peak EGT.

I am sure that is true - so long as the juice is available, so OK from the US perspective. The case for burning avtur hangs 75% on availability and taxation. The other 25% is better MPG, but it is only about that much.

FlyingStone

You have gone on and on about 100LL. If you reread my post you will see I do not use it!

Rod1

IO540
 

You are correct about saving 20% on the fuel burn by leaning to peak however you are still stuck with the ignition timing fixed firmly in one place.

The LASOR ignition system uses inputs from RPM and MP to move the ignition timing to the optimum position for the power setting and saves fuel in all phases of flight.

A FADEC will take this one stage further by enableing the engine to run so lean that it is right on the cusp of detonation, Lycoming are saying that with the FADEC they are working on the engine will in fact be four engines (or in your case six) conected to one crankshaft as each cylinder will be individualy managed.

In short the FADEC will be able to achive the sort of mixture control for each power stroke that you or I can achive only after we have been in the cruise for some time and it can also adjust the ignition timing, that we can't do.

Admitting this box of wiggly amps is better at controlling the engine comes hard from someone who's ultimate job would have been flight engineer on a Lockheed Constellation but that's what they call progress!

FADEC, LASOR ignition, ECUs, electronic injection, common rail for diesels, that is progress???
I thought we were talking magnetos here. And the one overiding quality of mags is that they are independent of the electrical system and continue to keep an engine running without electrical power.
All the gismos above require power, and are totally useless when the fan belt breaks or a short knocks out the electrical system. In fact with all that electronics on board a simple electrical failure will lose the engine and you will be looking for somewhere flat to put down your can of electronic goodies.
We have had this discussion here before, and IMO the advantages of diesel (simplicity, economy, reliability) have been trashed by Thielert and their ill concieved super complex and unreliable engines.
There are plenty of really good diesel designs out there which have not made it to the market because Thielert hogged the development money with their honeyed words. Now having soured the market they continue with their over complex turkeys. :\

http://www.ppdgemini.com/_PDF/Gemini...-10-09_B&W.pdf

If only some of that development money went into this (based on the highly successful Junkers WWII design)

...or in the Wilksch or DAIR engines... There have been diesel initiatives enough, besides Thielert. I can only suppose their makers were less good at marketing than at engineering - which is much better than the other way round. Yet here we are, without any reliable affordable diesel engine available.

Everything I have read about engine management suggests that any improvement on the present mags will be really minimal and probably well below 5% on SFC - once you are peak-EGT or LOP.

Electronic ignition would be nice because in theory it could last "for ever". But these old companies are not IMHO capable of designing a piece of electronics that lasts. They can only just barely make a crankshaft that's had the right heat treatment, without any of the steps having been skipped ;)

Favoris

This aircraft can fly for nearly nine hours :eek: , and gets approx 70 mpg on Jet A1.

French homebuilders are using Peugeot/Citroen car engines to achieve astounding performance on very low HP. The simple reduction gear and high diesel torque allows a large diameter slow turning prop. This efficiency helps to offset the weight of the iron car diesel engine.

Ah but check out the cruise settings for the Favoris. Max torque is at 2400 engine rpm which gives 1280 prop rpm, for a cruise at 200 kph.
Take off engine rpm is 5000 which gives 2600 prop rpm, and t/off roll of 350m. Not an impressive rate of climb however at only 550 ft.min; I should have thought a turbo diesel might have been a better engine choice.
Also I wonder how a car engine copes with regular thrashings at 5000 rpm for take off?

I think car engines have a long life history in aviation of just about exactly zero.

I know this has been done to death here many times but a typical car engine runs at 10-20% power most of the time. A typical 2000cc engine (i.e. assuming top speed of 120mph; my 1987 Celica would do 130) doing 70mph is running at about 30-40% power.

Anybody trying to run them at 65% or g0d forbid 75% power finds they fall apart fast. On serious rally cars, they change engines almost as often as they change tyres (but you don't see that on the TV coverage).

OK, one can "do a Thielert" and beef up the bits which you think are most likely to fall apart, but this is still a long way from "most" engines (well, non turbo ones, anyway ;) which is why I never bought a TB21) making a 2000hr TBO without any issues.

Back to mags, in the 1970s I used to make electronic ignition systems for motorbikes. These initially used the contact points (which would last for ever, due to the elimination of arcing) and later I did a magnetic pickup. I don't think there was any real obvious failure mechanism, and one could massively over-engineer the bits which were most stressed (the capacitor, and the semiconductors) but I would not trust Lyco or Conti to get somebody competent on the job, even though the car makers have pretty well sussed this in the intervening 30+ years.

Mags are damn expensive. I have just paid $2.5k for a factory overhauled D3000 mag, and that is just the mag, not the lid with the ignition harness. That is plenty of a budget for an electronic ignition and a distributor.

I think variable timing on a Lycoming would be great because when the mixture is leaned to ROP through LOP it moves the position of the peak pressure pulse towards top dead centre. This puts more stress on the engine as the power pulse occurs when the conrods are virtually straight up and down, resulting in "punching" the piston assembly into the crank. If the ignition timing can be advanced it'd move this peak pressure pulse futher away from TDC resulting in more efficient running and less stress on the engine bits, with the leanest possible mixture setting. It is easier for a computer to accomplish this, along with prop setting that fiddling constantly with the mixture and prop.

Sure one could fine tune things.

However, I have done very careful flight tests and have not found any MPG improvement from LOP, compared with peak EGT.

LOP makes you fly slower, which obviously helps MPG, but if you do the test at a fixed IAS (i.e. a fixed thrust), fixed RPM (i.e. fixed prop efficiency) then LOP does not produce a better MPG. It possibly delivers a cooler combustion, but that is an issue only at high power settings, which is in issue (in practical IFR flight, which is all high altitude) only with turbo engines.

Sure I would like electronic ignition. I am just not going to be their beta tester #23 :)