Aviation Aerodynamics & Aircraft Performance 2 — Questions and Answers
Question 1: What four factors affect aircraft performance at takeoff?
- Wind, fuel type, passenger weight, tire pressure
- Density altitude, aircraft weight, wind, and runway surface/slope (Correct answer)
- Air temperature only, runway length, fuel quantity, engine type
- Altitude, humidity, propeller pitch, and oil viscosity
Correct answer: Density altitude, aircraft weight, wind, and runway surface/slope
Density altitude, aircraft weight, wind direction/speed, and runway surface condition and slope are the primary factors affecting takeoff performance.
Question 2: What is density altitude?
- The altitude shown on the altimeter when set to 29.92 inHg
- Pressure altitude corrected for non-standard temperature (Correct answer)
- The altitude above mean sea level at a given airport
- The altitude calculated from GPS coordinates
Correct answer: Pressure altitude corrected for non-standard temperature
Density altitude is pressure altitude corrected for non-standard temperature; it represents the air density equivalent to a standard atmosphere altitude.
Question 3: An aircraft's POH states a ground roll of 1,000 feet under standard conditions. If density altitude is significantly higher than field elevation, what should the pilot expect?
- A shorter ground roll due to reduced friction
- The same ground roll because indicated airspeed is constant
- A longer ground roll because the aircraft needs higher true airspeed to lift off (Correct answer)
- A shorter ground roll because the wings produce more lift in thin air
Correct answer: A longer ground roll because the aircraft needs higher true airspeed to lift off
At high density altitude, thinner air requires the aircraft to reach a higher true airspeed before lift-off, resulting in a longer ground roll.
Question 4: How does a headwind affect takeoff performance?
- It increases ground roll because thrust is reduced
- It decreases ground roll by adding to the aircraft's airspeed relative to the air (Correct answer)
- It has no effect on takeoff distance
- It increases stall speed, requiring more runway
Correct answer: It decreases ground roll by adding to the aircraft's airspeed relative to the air
A headwind provides additional airspeed relative to the air mass, allowing the aircraft to reach lift-off speed at a lower ground speed and shorter ground roll.
Question 5: What is the best rate-of-climb speed (Vy) used for?
- Achieving the steepest climb angle to clear obstacles
- Gaining the greatest altitude in the shortest distance
- Gaining the greatest altitude in the shortest time (Correct answer)
- Maintaining level flight at minimum power
Correct answer: Gaining the greatest altitude in the shortest time
Vy (best rate of climb) provides the greatest altitude gain per unit of time, maximizing vertical speed in feet per minute.
Question 6: What is the significance of Vx (best angle of climb speed)?
- It provides maximum altitude gain per minute
- It provides maximum altitude gain per horizontal distance traveled (Correct answer)
- It is the speed for maximum endurance in cruise
- It is the maximum speed in level flight
Correct answer: It provides maximum altitude gain per horizontal distance traveled
Vx provides the greatest altitude gain per unit of horizontal distance, making it ideal for clearing obstacles after takeoff.
Question 7: If an aircraft's weight is increased, what happens to its stall speed?
- Stall speed decreases because the wings carry more momentum
- Stall speed increases because more lift is required to support the greater weight (Correct answer)
- Stall speed remains the same regardless of weight
- Stall speed decreases due to increased inertia
Correct answer: Stall speed increases because more lift is required to support the greater weight
A heavier aircraft requires more lift to remain airborne, which means a higher minimum airspeed (stall speed) is needed to generate that lift.
Aviation Aerodynamics & Aircraft Performance 2
What four factors affect aircraft performance at takeoff?