I have just carried out an experiment using the default C172 and the Flight1 C172 -- with basically the same results on both a/c.If I fly at 2000', the max groundspeed I can get (indicated on the GPS with zero wind) is 127 knots. However at 7000', I can only get 118 knots. Now at the higher altitude, I have leaned the engine for best performance.I have always thought that real life pilots use a higher altitude to attain higher true air speeds and higher ground speeds.What am I doing or thinking wrong??Thanks Barry

>I have always thought that real life pilots use a higher>altitude to attain higher true air speeds and higher ground>speeds.Not usually true for normally aspirated (non-turbo) engines. You go higher not because of speed but because of fuel consumption. You can fly a lot further in a C172 at 8,000 ft than at sea level. In a turbo-piston you will get both higher speed and better economy (range) at higher altitudes.Michael J.

There is a performance curve that combines engine power efficiency and drag effect at different altitudes. In thinner air at higher altitudes you have less parasitic drag but your aspirated engine gets less air to perform less efficiently.As the other reply stated, until you get to really high altitudes turbine powered engines are not affected as much. Turbo charged engines are better than standard reciprocals, but do suffer some loss as well and are not as good as turbine powered props or jets.To confuse matters further, maximum efficiency for cruise speed (time) does not equal maximum range. You would think that flying faster would enable you to go farther but then your fuel consumption is higher.That is why in the POH there are graphs for both conditions.

>>I have always thought that real life pilots use a higher>>altitude to attain higher true air speeds and higher ground>>speeds.>>Not usually true for normally aspirated (non-turbo) engines.>You go higher not because of speed but because of fuel>consumption. You can fly a lot further in a C172 at 8,000 ft>than at sea level. In a turbo-piston you will get both higher>speed and better economy (range) at higher altitudes.Thanks for that -- looks like my understanding is limited and incorrect.Barry

what you are getting is a lower indicated airspeed at higher altitudes because the air is thinner. You are really going faster than you would at lower altitudes, it's just the indicated won't show it.