12.100 Performance Factors

12.100.2 Describe the general effects of altitude on aircraft performance.

As altitude increases, air density decreases, and this generally causes a reduction in aircraft performance.

Effects of Increased Altitude

Reduced Lift

• Thinner air produces less lift at a given IAS and angle of attack
• Higher true airspeed is required to generate the same lift

Reduced Engine Power

• Less dense air contains less oxygen for combustion
• Engine power output decreases (particularly in normally aspirated engines)

Reduced Propeller Efficiency

• The propeller has less dense air to accelerate
• Thrust production is reduced

Reduced Climb Performance

• Less engine power, reduced propeller efficiency, and reduced lift all combine to reduce rate of climb

Longer Take-off Distance