After a long night with a fellow pilot, albeit a talented unlimited aerobatic one, we inevitably ended up in the pilot vs engineer discussion. The head ache the next day was due to the booze ;-)
The point; how much power/weight ratio would you need more to give up a constant speed prop if you owned say an unlimited Extra with stock power and wanted to keep aerobatic performance identical. 10 more hp? 50 or even a hundred?
The background? I've earlier reasoned towards an ultra-light weight unlimited aerobatic ship, using something like the Rotax or the ULpower 350. Some recent work showed me just how little the weight penalty is of installing a 2nd seat if the other parameters (MTOW, engine etc) remain the same. Then, a good old O-360 is no more expensive than a Rotax, so one could just as well shove that in. Turns out that as long as you keep the total empty weight under 600 lbs, at least based on specs that should have roughly equivalent performance to an E330SC.
Such a low empty weight with that engine obviously means fixed-pitch prop and a few other trade-offs, hence the question.
The earlier topics in which this came up:
https://www.homebuiltairplanes.com/forums/showthread.php?t=23473
https://www.homebuiltairplanes.com/forums/showthread.php?t=24830
The point; how much power/weight ratio would you need more to give up a constant speed prop if you owned say an unlimited Extra with stock power and wanted to keep aerobatic performance identical. 10 more hp? 50 or even a hundred?
The background? I've earlier reasoned towards an ultra-light weight unlimited aerobatic ship, using something like the Rotax or the ULpower 350. Some recent work showed me just how little the weight penalty is of installing a 2nd seat if the other parameters (MTOW, engine etc) remain the same. Then, a good old O-360 is no more expensive than a Rotax, so one could just as well shove that in. Turns out that as long as you keep the total empty weight under 600 lbs, at least based on specs that should have roughly equivalent performance to an E330SC.
Such a low empty weight with that engine obviously means fixed-pitch prop and a few other trade-offs, hence the question.
| Extra 330SC | New proposal | Old proposal | ||
| Power | 350 | 180 | 130 | hp |
| EW | 1300 | 600 | 400 | lbs |
| Pilot | 200 | 200 | 200 | lbs |
| Fuel | 175 | 90 | 65 | lbs |
| AUW | 1675 | 890 | 665 | lbs |
| power/weight | 0,209 | 0,202 | 0,195 | hp/lbs |
| Prop dia | 1980 | 1980 | 1700 | mm |
| Prop disk | 3,08 | 3,08 | 2,27 | m2 |
| Disk loading | 114 | 58 | 57 | hp/m2 |
The earlier topics in which this came up:
https://www.homebuiltairplanes.com/forums/showthread.php?t=23473
https://www.homebuiltairplanes.com/forums/showthread.php?t=24830
