Whether you are aware of it or not, we are on the initial wave of a diesel revolution in the aviation industry. Over the past decade, there have been a few manufacturers starting to invest heavily into diesel engine technology for the air.
Of course the issue with the air is that the engine cannot fail. Many times there are redundant systems in place for critical components that could result in engine failure midflight. These redundant systems add weight to the engine. Considering the fact that diesel engines already weight a substantial amount more than a relatively similar displacement gas engine, diesel for years have had a hard time making their way into the air.
So, what has changed?
With recent advances in manufacturing and materials diesel engine are starting to be manufactured in lighter packages. CGI blocks and aluminum blocks are starting to become a reality for diesel engines. Add in aluminum cylinder heads and diesel engine packages are starting to become much lighter than they used to be, still not quite the same as a gasoline engine, but getting close.
Diesel lovers already know but the aviation world is starting to learn that diesel engines are much more fuel efficient than gasoline engines. It is not uncommon for a diesel to get 20-percent better economy. That 20-percent can mean less fuel needed to get somewhere (making up for the additional weight of the engine) or it can mean a greater distance between fill ups. Great for cross country traveling.
The EPA and other regulatory agencies all over the world are trying to remove avgas. Unlike the gasoline in our engines on the road, avgas still contains tetraethyllead. This is a toxic substance that was removed from our fuels in the ‘70s but not in avgas. Currently there is a big push to get rid of this toxic gas and as a result, manufacturers see the writing on the wall. Having an engine that is able to run on an available Jet-A fuel would position them well for the future. While many smaller airports and fields don’t carry Jet-A, it could be foreseen that they may add it if more plane owners start requesting it.
What are the hurdles?
There are still some hurdles facing the good ole compression ignition engine through. They are relatively new for airplanes and their maintenance cycles will be low for quite some time. Needing to overhaul an engine early means lots of extra money spent.
In addition, there are concerns about how high they can fly. As altitude increases, air becomes less dense and colder. The combination of these two could put out the flame and cause a stall out. This issue is known and manufacturers are designing for this. There are prototype diesels able to fly at 30,000 feet but 18,000 is about as high as one is certified to fly.
So, next time you see a plane, keep an ear out to hear if it is a diesel or not!