Answer :
Thrust Horsepower (THP) is calculated by multiplying the propeller's thrust in pounds by the True Airspeed (TAS) in knots, then dividing by 375. For a propeller generating 280 pounds of thrust at 88 knots, the THP is approximately 66 hp, so the nearest correct answer choice is 67 THP. Hence, C is the correct option.
To calculate the Thrust Horsepower (THP) produced by a propeller, we use the formula:
THP = (Thrust *TAS) / 375
where:
- Thrust is given in pounds (lbs)
- TAS (True Airspeed) is given in knots
- The constant 375 converts the product of thrust and speed from pound-feet per minute to horsepower (since 1 horsepower is defined as 550 foot-pounds per second, and there are 33,000 foot-pounds per minute in a horsepower); the conversion factor is actually 33,000 / 88 (the feet per minute in one knot).
So, the Thrust Horsepower can be calculated for a propeller generating 280 pounds of thrust at a TAS of 88 knots as follows:
THP = (280* 88) / 375 = 24640 / 375
= 65.7066667 hp, which we round to 66 hp.
Therefore, the closest answer to the question is C. 67 THP, rounding to the nearest whole number.
