PlasticPilot.net

Modern general aviation planes are much more environment friendly than the previous generation, for many reasons. This also applies to modern airliners like the Airbus A380 or the Boeing 787 Dreamliner, and to all kind of planes in between.

This post is the first in a series triggered Mike Masson’s question, left in my “Any question ?” page:

“As a long term environmentalist with a deep concern about global warming, I have been watching the development of more efficient planes and engines with interest.

The engine that really attracted my attention was the Zoche - but nothing seems to have happened there for ages - is it dead or about to arrive?

Also, any information on the fuel efficiency of the new Diamond engines - are they 20% more efficient that the current DIESELS or just current Avgas? Any idea when they might be available ?”

First of all, thank you Mike for being an open environmentalist, and not an integrist. Aviation is not exactly environment-friendly, particularly when looked at as a hobby. However if any hobby or passion had to be good for our environment, the available activities would be quite reduced. No argue on this please.

Obtaining information from Diamond or Zoche is not easy, especially as it always comes wrapped in marketing. Even the concept of efficiency is not clear. Are we talking of gallons per hour, per nautical mile, per nautical mile and passenger ? I don’t want or can enter such an argument here, my goal is simply to highlight some trends and factors.

My guess on the new Diamond engine is that it will be 20% more efficient than the Thielert, as comparing AVGAS and Diesel would not make sense. Diesel engines are generally more “efficient” than AVGAS. Let me clarify what I mean by that…

From a pilot point of view, the only comparison that makes sense is amongst equivalent kind of flying in different planes. To talk about planes I know, let’s compare a DA40-TDI and a PA28-180. Both planes are good for flying with three or four persons on board, at speeds in the 120kts range.

The PA28 will need roughly 10 gallons of AVGAS per hour, where the DA40 will burn 5.5 gallons of Jet-A1. Yes, these figures depend of power setting and so on (no endless arguments please…), but they give a correct order of magnitude.

The easy conclusion is to say “Hooray, diesel is the solution, retro-fit it on all planes !”. Wait a minute…

Combusition of Jet-A1 and AVGAS do not produce the same gases. Jet-A1 combustion produces “thin particles”, which are suspected as a cancer factor. AVGAS generates more NOx (Nitrogen oxydes), which have various effects on health and environment.

However in terms of “efficiency”, the major difference is that the PA28 airframe needs 180HP to fly at 120 kts ! Change it for a 135HP and you won’t get the same performance, even with the fixed speed prop !

The DA40 can reach same speed because of its modern design and construction technique… this will be the subject of the next post in this series… stay tuned !