PMD
Well-Known Member
With all of our discussions around engine types, configurations, sources, etc. it occurs to me that we should have some kind of "standards" with easy reference mileposts to be able to relate one power system to another.
Let me first advance a couple of suggested values.
Bare Engine: dry, everything directly attached from motor mount interface to prop flange. I say that specifically as some engines (Rotax 9xx for instance) use a separate mounting structure to be able to use a "normal" engine-to-firewall tubular mount and many engines that are promising need a workable PSRU before they are of any real use.
As Installed Engine: Every attached system needed to make it run, including cooling and lube systems, induction, exhaust, etc. i.e. ready to hang on firewall.
For these two, I feel the bare minimum to be "aviation - like" is around 1Kg/KW (1.6 lb/HP) and the holy grail is more like 1 lb/HP (0.6 Kg/KW)
5 Hour Weight: Here is the one that to me is most important, especially when we discuss alternative energy sources. Everything it takes including starting systems, prop, mounts, fuel and fuel tanks (when not part of structure - and then including bladders or sealants). I suggest that time as pretty much normal for a 4 place spam can. Curiously, it is also right around the crossover for sub-flight-levels turbine installations vs. recips.
1,000NM Weight: Similar to 5 hour for travelling machines IMHO 1k NM is pretty much what you need to avoid a lot of fuel stops. Not a lot of airplanes can actually do this but if you want to compare apples to apples this is something almost any ICE airframe can easily be configured to do.
Two things in particular sent me down this road: discussions regarding automotive engines that look just great sitting in a junkyard and of course the whole gamut of alternative energy systems when you actually have to configure them to be useful in an airplane. I am guestimating that the 1000NM weight is around double the installed engine weight.
Maybe best to think about these 4 standards as: 1. Think about flying, 2. Get off the ground, 3. Stay off the ground and 4. Go somewhere.
Let me first advance a couple of suggested values.
Bare Engine: dry, everything directly attached from motor mount interface to prop flange. I say that specifically as some engines (Rotax 9xx for instance) use a separate mounting structure to be able to use a "normal" engine-to-firewall tubular mount and many engines that are promising need a workable PSRU before they are of any real use.
As Installed Engine: Every attached system needed to make it run, including cooling and lube systems, induction, exhaust, etc. i.e. ready to hang on firewall.
For these two, I feel the bare minimum to be "aviation - like" is around 1Kg/KW (1.6 lb/HP) and the holy grail is more like 1 lb/HP (0.6 Kg/KW)
5 Hour Weight: Here is the one that to me is most important, especially when we discuss alternative energy sources. Everything it takes including starting systems, prop, mounts, fuel and fuel tanks (when not part of structure - and then including bladders or sealants). I suggest that time as pretty much normal for a 4 place spam can. Curiously, it is also right around the crossover for sub-flight-levels turbine installations vs. recips.
1,000NM Weight: Similar to 5 hour for travelling machines IMHO 1k NM is pretty much what you need to avoid a lot of fuel stops. Not a lot of airplanes can actually do this but if you want to compare apples to apples this is something almost any ICE airframe can easily be configured to do.
Two things in particular sent me down this road: discussions regarding automotive engines that look just great sitting in a junkyard and of course the whole gamut of alternative energy systems when you actually have to configure them to be useful in an airplane. I am guestimating that the 1000NM weight is around double the installed engine weight.
Maybe best to think about these 4 standards as: 1. Think about flying, 2. Get off the ground, 3. Stay off the ground and 4. Go somewhere.
