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Tecnam P2012

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I find it hilarious:
Tecnam fits the new P2012 Traveller with state of the art, turbocharged Lycoming.

Someone put Lycoming and state of the art in one sentence. I think those 2 words contradict each other.

United Kingdom

Actually, as long as there is nothing better, it IS “the state of the art” ;-)

Flyer59 wrote:

Actually, as long as there is nothing better, it IS “the state of the art” ;-)

How about a PT6?

EKRK, Denmark

Saying a PT6 is a state-of-the-art piston engine is like saying a 100HP motorcycle is a state-of-the-art bicycle.

Joking aside – the engines are “T*_E_*O-540”, with electronic iginition, leaning, and individually controlled fuel injection, anti-knock sensors etc, so everything other than the basic engine it appears to have modernised substantially and has arrived in the late 90’s.

Last Edited by Cobalt at 27 Nov 12:57
Biggin Hill

It would be interesting to see how fuel consumption is effected by such developments

I suspect, not much over flying the same engine lean of peak.

Assuming the same basic engine geometry, there are three things you can do
– mixture
– ignition timing
– valve timing

Mixture is most of the efficiency improvement potential. Electronic mixture settings with oxygen- and anti-knock-sensors will make sure that you can more reliably fly the engine at peak or lean of peak, and a modern ignition system will make it run smoothly there, but this will not be a game changer for someone who already flies LOP.

Iginition timing will help a bit – in general, for LOP operation you would like to increase the advance a bit to get more power at the same fuel flow, so that could give you a bit more HP per pound of fuel

Valve timing is almost irrelevant for engines that operate at a constant RPM in a very narrow range. And these engines don’t do it, anyway.

Biggin Hill

I agree; unless Lyco are completely stupid, they will have set the ignition timing to be optimal for cruise.

However, there is a second order effect: low RPM cruise. At low rpm, deeper LOP works better because the slower burning mixture matches with the lower RPM. See the table here for example. And it’s not a tiny effect. So dynamic optimisation of ignition timing would be beneficial, for pilots who take the time to learn about this.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

However, there is a second order effect: low RPM cruise. At low rpm, deeper LOP works better because the slower burning mixture matches with the lower RPM. See the table here for example. And it’s not a tiny effect. So dynamic optimisation of ignition timing would be beneficial, for pilots who take the time to learn about this.

Fixed ignition timing is set for max rpm, max sea level or turbo MP. The pilot can reduce power by reducing rpm, in which case the engine needs less advance (in degrees), if he reduces power with MP (throttle or climb) the engine needs more advance, if he leans at any power setting the engine needs more advance. So what’s theoretically needed to optimize spark timing (assuming pilot controlled load configuration and no feedback) is advance selected by a four dimensional ignition map. The funny thing is that because two of those factors tend to push the optimum timing in opposing directions, the theoretical map will be pretty flat for typical low altitude pilot controlled operation and there will be no great efficiency benefit for variable ignition timing. It is in high altitude operation where there’s an advantage, and where the load configuration is more like a car: in that case there is little reduction in rpm and a large reduction in MP, pushing the optimum spark timing in one direction (more advance). Leaning LOP then pushes further in the same direction.

Last Edited by Silvaire at 27 Nov 16:48

Brilliant explanation, Silvaire

But how many pilots will lean at the same time as reduce RPM? If you just reduce RPM, but increase the MP in order to maintain the power output (i.e. IAS) you don’t get much benefit. Or did I get that wrong?

Administrator
Shoreham EGKA, United Kingdom

The engines are a substantial step forward in technology terms. OK, maybe it’s not revolutionary technology, but we should not complain. As for the aeroplane, it’s like a modern Navajo.

Darley Moor, Gamston (UK)
29 Posts
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