The TB20 is rather rare so might not see it. The SR22, C182 and Bonanza are candidates.
Sure – same with the DFC90. Never relevant to so many people. There are ~2000 TBs, of which most are 20s and 21s. That’s not a bad market.
The SR22 is an obvious market but whenever I go to a fly-in in Europe, or just fly to some airport longer than the usual burger run, I see very few of them. That’s just the European perspective, and of course there are exceptions (e.g. Bosco here) but the GA scene is very diverse, and just going for the low hanging fruit deals mostly with the burger run crowd (in Europe – in the USA SR22s fly a lot more and fly a lot further). The SR22 which was based at Shoreham (now at the bottom of the sea) was doing mostly trivial flights.
Most GA flying is short hops and patterns and there is virtually no stochiometric mixture involved. Most pilots don’t even know how to do that.
Exactly… so the reason for spending a load of €s on a diesel retrofit is close to zero, and way below zero when you work out how long it will take you to recover the money, especially in the UK where diesel is now taxed like avgas. Unless one is a champagne environmentalist, but when it comes to the crunch there aren’t many of those…
The other problem is that all the diesel packages seem to always be priced to look good for commercial ops i.e. schools. The vendors just know the private market is tiny…
Is it however a reality that a petrol engine, running stochiometric, is not going to be much improved on with FADEC
A petrol engine that “WE THINK” is running stoichiometric – based on RPM adjustment by the ear and dodgy tachometers, or marginally less dodgy EGT probes… :)
bq
And herein, dear Achim, lies the problem. It’s all very well for Mercedes to invest a billion or two in engine design that will be spread over a few million engines sold. Quite different, if you have to spread that money over a few thousand aero engines. Hence the Thielerts and Austros – modified car engines, where the investment is recouped on the road (by Mercedes, in this case). The market for pure aero engines is simply too small.
The market for aero-engines will never get beyond small if the makers keep selling outdated inefficient designs of poor metallurgical quality that break down whenever they fancy. Mercedes didn’t start out with a few million engines either.
Shorrick, you actually don’t need an accurate tachometer to set the mixture – you do need to understand a little about how engines work.
Nobody is going to sink billions of dollars into GA engines, because if they did the price would be outside of what the real world market is willing to pay, and any increase in efficiency is likely to come with other technical compromises that the market does not want to accept. That’s not rocket science to understand, eh? We are very lucky to have reliable, simple engines right now, designed when there was a bit more R&D money available due to higher sales volumes. Obviously Europeans don’t like that they didn’t design those engines. Europeans are bitter about all kinds of stuff. Tough.
Nowadays the best place to put money in GA is in airframe design, anywhere in the world, because its cheaper, and specifically Experimental airframes to be sold in the US because that’s where a price point can be achieved that generates feasible sales volume. If you simply cannot accept that reality, there’s really not a lot that can be done about it.
You don’t need accurate EGT measurement to operate at peak EGT.
You just start a bit rich (like we all do when we get into flying, eh 
) and then lean until you find peak EGT.
The absolute EGT value doesn’t matter.
My EGT is slow to react and I run out of patience! Plus if you have only one probe the whole thing is an approximation. Regardless, If you do it the ‘fixed pitch’ way you get a fair fraction of the reduction in fuel consumption and the extra (let’s say) 0.5 GPH is not really worth me getting excited about. The main benefit comes from leaning in any way that’s reasonable versus not doing it at all.
Quick leaning – pull back mixture until RPM drops (fixed pitch) or the engine runs rough (VP prop). You are now lean of peak. Enrich quickly until engine is smooth again / RPM back to normal. You are now somewhere around peak. Now you can start finding the peak and staying there. Leaning a non-turbo engine at FL100 using the vernier is taking too long, I agree.
You don’t need accurate EGT measurement to operate at peak EGT.
You just start a bit rich (like we all do when we get into flying, eh ) and then lean until you find peak EGT.
The absolute EGT value doesn’t matter.
I suppose this is correct for non-turbo engines, but for turbo engines? A friend of mine just bought a Turbo Commander and we are both trying to find out how to operate it. The POH is very specific about never letting the EGT get higher than 1725 degrees, and sure enough the EGT gauge shows a red line there. I suppose it has to do with not damaging the exhaust driven part of the turbo, right? The other day we went out to lean the thing and peak EGT was right about at that 1725, so that didn’t feel all that comfortable, especially assuming that a gauge is never accurate..
Also we were a bit surprised to see that the indications of % power on the EDM engine monitor were quite a bit higher than what the POH says at a given MAP/RPM.
Any advice welcome..
[quote fixed]
I am no specialist in this but I do know that in the TB21 you can exceed the TIT, whereas in the TB20 there is no way to produce an excessive EGT.
So a lot of turbo owners fly ROP, because they would exceed the TIT at the power setting at which they choose to fly (you could always stay below the TIT limit, at peak EGT, by reducing the power output).
That is probably a big factor in why the range of a TB21 is usually said to be quite a lot less than that of a TB20. I could never understand why this should be; it doesn’t make any sense (assuming you have oxygen).
