Lets say a plane had 2 engines located 9m ahead of its rear wheels. Give each engine a mass of 7.5 tonnes. A force of 147150N will act 9m ahead of the rear wheels. lets say the aircraft was 133 tonnes in total.
My question is if you were trying to determine the position of the centre of mass of the aircraft would 133 tonnes act through the centre of mass or would 133 tonnes subtract the weight of the 2 engines act through the centre of mass? So what would be the equlibrium equations when resolving vertically and taking moments?
I have made up some numbers for the distance between the front and rear wheels and the overall length of the aircraft in my diagram. I have indicated an guess for the mass centre using a cross.