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During the descent, how are the Minimum Rate of Descent and Minimum Descent Gradient affected by a decrease in mass? The Minimum Rate of Descent:
  • A
    increases, and the Minimum Descent Gradient remains unchanged.
  • B
    remains unchanged, and the Minimum Descent Gradient increases.
  • C
    decreases, and the Minimum Descent Gradient remains unchanged.
  • D
    remains unchanged, and the Minimum Descent Gradient decreases.

Refer to figure.
Effect of weight on a Glide Descent

SIN (θ) = (D - T) ÷ W

For the effect of weight on the descent we shall only consider the effect in a glide, in other words with idle power:

SIN (θ) = D ÷ W

Considering Weight almost the same as Lift:

SIN (θ) = D ÷ L or SIN (θ) = CD ÷ CL

Best glide angle occurs at maximum CL ÷ CD, VMD. Also, can be deducted that the best glide angle is unchanged by Weight. However, a lighter aircraft will a have a lower VMD, the aircraft fly’s at a lower airspeed throw the same glide path.

Rate of Descent (fpm) = Gradient of Descent x TAS (VMD)

Maintaining the same Gradient of Descent with a lower airspeed, ROD decreases.

Note: Since question mentions Minimum Rate of Descent and Minimum Descent Gradient we believe that it is about glide.

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