lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> As I understand it, density altitude is the altitude the "aircraft thinks it is flying". Density altitude increases with temperature as the air is expanded by heat. thus less oxygen enters the engine for a given volume hence less air equates to less horsepower equals less speed. Density altitude is also affected by atmospheric pressure. A low barometer also equates to lower pressure higher density altitude again reducing performance. Also since the air is less dense, it supports less weight thus you need to increase the angle of attack of the wings to compensate to obtain the same lift amount equal to the weight of your aircraft. This increases drag which further reduces airspeed. The reason you notice the higher speed deterioration as compared to the Bonanzas and other production aircraft is they are not as efficient and clean as our birds. Consider that the bonus speeds we have, be grateful we have that benefit and do not dispair on those hot days when the ASI is slower. You can still look through your back windows and see those V-tails and all other aircraft in your wake turbulance. As I have found from experience, optimal performance, (for a non-turbo powered aircraft is around the 7500 msl on a standard day for standard temp and pressure at 24 inches manifold pressure and most props are most efficient at about 2400-2450 rpm. Of course if you are an air racer all this stuff goes out the window and reduced drag, rpms and horsepower prevail. I have also found that as you go lower to sea level you need to increase manifold pressure to obtain the same speed. the 320s have the extended wingtip option. Those birds fly faster than the standard wing at higher altitudes by about 4-8 kts. I'm not schooled in the reason except the wing loading is lower thus the pitch attitude may be reduced to produce the same lift thus less overall drag. Does this make sense? Regards to leading edge tape. You need to make the decision of (a) do I want a clean looking bird or (b)go for the increased fractional speed. What is the difference in flight time on a 2-3 hour flight? Decisions, decisions. You are more fortunate than others to have these decisions to make. Enjoy your plane. Bob Smiley N94RJ >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://www.olsusa.com/mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>