Hola Dean...
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I could help you a little if you were able to give me the TSFC of your type of engine, and its rated thrust at sea level... How I explain this in classroom for the 747 engines is as follows...
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747-287 - Engine P&W JT9D-7Q
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Maximum rated thrust sea level = 52,700 lbs
TSFC thrust specific fuel consumption = .378
Fuel flow at takeoff = 19,915 lbs (to get 52,700 lbs of thrust)
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So if in cruise, FF is 4,000 lbs, thrust is about 10,500 lbs
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Happy contrails