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Trimmed Aircraft Answers
  1. An airplane in trimmed flight has a wing lift(W) of 30,000 Newtons. It has a wing distance(dw) of 2 meters and a tail distance(dt) of 10 meters both located aft (behind) the center of gravity(cg) . Assume that the direction aft of cg is positive.
    1. What is the magnitude of the the tail lift(T)? 6,000 Newtons
    2. Is the tail lift positive or negative? Negative
    3. What is the total lift of this trimmed aircraft? 24,000 Newtons
  2. You must design an airplane with a wing with a lift(W) of 40,000 Newtons, a tail lift(T) of - 8,000 Newtons and a wing distance(dw) of 3 meters aft of cg.
    1. What is the total lift? 32,000 Newtons
    2. What must the distance of the tail(dt ) be aft of cg? 15 m
    3. Your customer now wants a wing distance(dw ) of 2 meters aft of cg, what must the tail distance(dt ) be aft of cg? 10 m

  3. Your customer now wants the tail in the original design placed forward of the center of gravity(a canard configuration).
    1. Is the canard lift in this design positive or negative? Positive
    2. What must the distance of the tail(dt ) be forward cg? 15 m
    3. Is the canard distance(dt) from the cg positive or negative? Negative
    4. What is the total lift for this canard configuration? 48,000 Newtons
    5. How does the total lift differ from the conventional design? Greater by 16,000 Newtons
    6. What type of tail design did the Wright Brothers Airplane have? Canard Configuration
  4. A cargo plane trimmed for normal flight has a total lift of 120,000 Newtons. This aircraft's Wing lift(W) is 150,000 Newtons and it's wing distance(dw) of 5 meters behind cg. What is the tail distance(dt) behind cg? 25 m 

  5. The airplane in the previous problem had some of it's cargo shift aft. This caused it's cg to shift 2 meters aft.
    1. What is dw now? 3 m
    2. What is dt now? 23 m
    3. With no adjustment by the pilot, what will the airplane do? Lose lift/ Fall back and lose altitude/Tail First
    4. If wing lift(W) remains constant, the pilot must adjust tail lift (T) to what value to maintain trimmed flight? 19,565 Newtons

 

Please send any comments to:
Curator: Tom.Benson@grc.nasa.gov
Responsible Official: Kathy.Zona@grc.nasa.gov