Hughes500,
Cool your jets. If you have an engine that is 75% thermodynamically efficient, run, don't walk, to the patent office, you are an instant millonaire!
The hype in the above posts is like those internet legends about an engine that runs on water, but is suppressed by the "oil companies" or some such truck.
The figures given by rotorrookie are truly from a rotor rookie, the typical helicopter gas engine weighs about 0.66 Kg per HP, not the inflated numbers he found somewhere. While there might be some advantage to diesels in aircraft, I think the data must speak for itself, and it should be good data, not that drawn from sites that are selling.
I'd suggest that you have a bit of trust in the guys who build what you fly. Do you feel like the people who design and build the machines know what you do? Do you think the design engineers at the manufacturers wait for the latest "Pilot" magazine to help them drum up new ideas?
The engines we use are proven and work well. The margins in the helo industry don't allow much error in picking the engine. I am also intrigued by the web site that shows a diesel that is 10% lighter than a gas engine (nice trick, when the 17:1 compression ration dictates much higher stresses and more engine structure to withstand the ass-kicking thoise pistone give the engine). I am not saying that I disbelieve the diesel sites, but I surely would like to see their Type Certificate Data Sheets, issued by a strong governmental test org, before I took those figures to the bank (or trusted my family to the reliability of the engine they are selling.)
Frankly, the Deltahawk site impresses me, the figures look about right, and the engine is not overplayed. It will be quite something if they make a good FAA certificate, but they haven't even started down that path. Note the worry about endurance at high power. This is where you cut the nut in engine design/test. I wish them best of luck, but FAA test is when the fun begins, I think!
Last edited by NickLappos; 28th Dec 2004 at 19:03.