I've heard it put another way in the context of avgas vs mogas. Something like 30% of the GA fleet uses something like 70% of the Avgas and these are mostly airplanes that have engines that cannot use mogas - but I digress.TimS wrote:
You can do more then just size, you can also do shapes. People are trainable. e.g. extreme oval versus round. As long as it is smaller in diameter then the standard gas cap which is about about 2-3 inches, it will continue to work for the existing/legacy fleet.
I would also state there have been a multiple of surveys by the FAA, and fleet data provided by Cirrus, that between 60-80% of the avgas in the country is consumed by planes less then ten years old (the large range depends on assumptions).
Lastly, the newer aircraft are the most active part of the fleet, they also tend to be the models most likely to have Jet-A and 100LL variants. e.g. DA42, PA46, DA40.... So reducing the chance of human error for something that is reasonably simple technically would be a smart thing to do (in my opinion).
I do not think many avgas powered DA-42s were delivered in the US. The few that were are mostly on line at university based training facilities. DA-40's in the US I think are virtually all avgas powered and only the -FP could use mogas.
But besides the PA-46 which is close to 50:50 avgas:jet-A, there are about 130 Cessna 210-P's converted to turbine. Then there are a few dozen Bonanza's that have been converted. Then the twin market although much smaller gets more confusing. The Piper PA-31 series were delivered as avgas powered models such as the Navajo and Chieftain, and as turbine models called the Cheyenne I & II.
The Cessna twins such s the 414/421 were avgas powered but the nearly identical looking Conquest I was turbine powered. Then there are the Cessna 340's that have been converted to turbine as well as a couple of dozen Beech Dukes that have been converted to PT-6's.
It seems like the best solution is better training of line personel. All they need to do is look at the fuel placard at each filler BEFORE throwing the protective rubber mat on the wing that usually obscures the placard.