It is stated that a turbofan engine produces 15000 pounds of

It is stated that a turbofan engine produces 15,000 pounds of thrust to propel an aircraft forward. Is \"pound\" mentioned here lbm or lbf? Explain.

Solution

Pound-mass lbm is the mass unit in English system whereas pound-force lbf is the force unit. One pound-force is the force required to accelerate a mass of 32.174 lbm by 1 ft/s². In other words, the weight of a 1 lbm mass at sea level is 1 lbf.

The pound mentioned here must be “lbf” since thrust is a force.