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Which of the following statements is correct?

I. A high limit load factor enables the manufacturer to design for a lower stick force per g.
II. The stick force per g is a limitation on the use of an aeroplane, which the pilot should determine from the Aeroplane Flight Manual.

  • A
    I is incorrect and II is incorrect.
  • B
    I is correct and II is correct.
  • C
    I is incorrect and II is correct.
  • D
    I is correct and II is incorrect.
Refer to figure.

The most direct appreciation of the maneuvering stability of an airplane is obtained from a plot of stick force versus load factor.

The airplane with positive maneuvering stability should demonstrate a steady increase in stick force with increase in load factor or “g”. The maneuvering stick force gradient - or stick force per “g” - must be positive but should be of the proper magnitude.

The stick force required is the amount of effort necessary to overcome the longitudinal static stability of the airplane. To fly the airplane at an airspeed different from that for which it is trimmed the stick force required is dependent on the location of the CG and the size of the tail plane.

The stick force per g must have upper and lower limits to ensure that the airplane has acceptable control characteristics at all times.

A forward CG position increases longitudinal static stick-force stability. The magnitude of the stick force required decreases as the CG moves aft; therefore, the maximum permitted aft position of the CG is limited by the minimum acceptable value of the stick force per g.

As seen in figure 1, a lower stick force per g means that to attain a certain load factor a smaller stick force is required. This means that it is ‘easier’ to stress the aircraft and so a higher limiting load factor is desirable. Therefore, statement 1 is correct.

There is no way of the pilot knowing the value of stick force that he is applying. Therefore, it is not a limitation included in the Airplane flight manual. Statement 2 is incorrect. The maximum load factor, on the other hand, is a limitation on the use of an airplane, which the pilot should determine from the Airplane Flight Manual.

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