Check density altitude before departing. When parking aircraft on sloping terrain, be alert to the possibility of fuel siphoning overboard. When taking off into the wind in a narrow canyon with several sharp bends, downdrafts may be encountered without warning. Often, pilot reports are the only reports you get in the mountains. Monitor 122.0 for current reports.
Density altitude is a crucial criterion that determines the performance capabilities of an aircraft.
Air density decreases with altitude. The further effects of high temperature and high humidity are cumulative, resulting in an increasing high density altitude which reduces all aircraft performance parameters. If the CG is set to the forward position, a stall will be encountered at a higher than normal stall airspeed configuration. Density altitude is the altitude at which the aircraft thinks it is and performs accordingly. Full power leaning may be necessary for takeoff and landing procedures with normally aspirated engines.