During an engine test on the ground, a propeller thrust is generated on the 1500

Question

During an engine test on the ground, a propeller thrust is generated on the 1500 kg airplane with mass center at G. The main wheels at B are locked and do not skid; the small tail wheel at A has no brake.

1) Calculate the normal forces NA and NB and the frictional force FB when the engine is off(T=0)

2) Calculate the normal forces NA and NB and the frictional froce FB when the engine thrust is T=3000N

During an engine test on the ground, a propeller thrust is generated on the 1500 kg airplane with mass center at G. The main wheels at B are locked and do not skid; the small tail wheel at A has no brake. Calculate the normal forces NA and NB and the frictional force FB when the engine is off(T=0) Calculate the normal forces NA and NB and the frictional force FB when the engine thrust is T=3000N

Explanation / Answer

1) NA + NB = W = 1500Kg*(10m/s^2) = 15000 N

Also, On torques,

NA*0.8 = NB*4 (Since opposing torques)

=> NA = 5* NB

=> 5NB + NB = 15000 => NB = 2500 N

and NA = 12500 N

Engine is off, so Fictional force FB is unnecessary and is 0.

2) At T=3000 N,

Horizontal force to right is Tcos12 = 2934.44 N

and Vertical force upwards = Tsin12 = 623.735 N

So Frictional force FB = Horizontal force (equal opposite forces) = 2934.44N to left.

Also, NA + NB = W - 623.735 = 15000 - 623.735 = 14376.265 N

(Since Torque condition is same):

=> NB = 14376.265/6 = 2396 N

and NA = 5NB = 11980.2 N

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