Netters To simply expand on what Larry is saying, the most dramatic that high density altitude has on an airplane is to its power and thrust output. Thinner air (for discussion) regardless of how you get it, whether you are high elevation, or just very hot, or combinations will yield much lower power output from the powerplant, and less thrust achieved from the prop. This being said, you will also have a higher speed on takeoff roll, longer takeoff roll, higher stall speeds, due to the lowered amount of lift that the wing is able to achieve at this higher density altitude. The KR typically has a short takeoff roll anyway so it may not be that noticeable to someone with good power, but a marginal aircraft on a cool day at sea level, may not get off or out of ground effect on a high density altitude day. Just yesterday I was taking off in a C172, 180hp O-360 with an outside temp of 97 degrees, density altitude close to 2000 feet, field elevation of only 55 feet above sea level. The Vr for the aircraft is published as 55 knots, but we did not separate from the runway until nearly 65 knots, and rolled 2/3 of a 3500 foot long runway. Climb on a cool day is this aircraft is normally on the order of 1250-1500fpm with only 2 on board, yet 750-800fpm was the best it would do until passing through 1200ft then it started running alittle stronger as the air cooled alittle. The indicated speeds will be adjusted by the change in density altitude by the way the indicator works, so they will appear in the normal range, but actual speeds are higher, no difference then when flying at 6000-8000. The difference being you are still touching the ground in the takeoff instance. Those with surplus hp and torque do not notice these effects as much, but a clue might be to take note that most aircraft that I have seen that fly mountainous areas regularly are either turbo-charged, or the next size larger engine available, i.e.: IO-540 in place of an O-360 etc...
Colin & Bev Rainey KR2(td) N96TA Sanford, FL crain...@cfl.rr.com http://kr-builder.org/Colin/index.html
