mixing up mass balance and aerodynamic balance

Exam question

What does the term mass balance mean?

A.Weights used to balance any primary control surfaceCorrect
B.Aerodynamically shaped weights attached to the flaps
C.Very heavy weights attached to the nose of the aircraft

Explanation

Mass balance means weights used to balance a primary control surface about its hinge.

Rui

asked · 2 Sep 2026

Author

doing m11 practice and keep getting these two confused. mass balance is the weights forward of the hinge line so the surface doesn't flutter, right? and aerodynamic balance (horn, inset hinge etc) is a completely different thing, it's just there to make the surface easier to move for the pilot and has nothing to do with flutter. keep seeing questions that seem to test one when i think it's actually asking about the other. is there an easy way to keep them straight

Discussion1

Part66Exams team

26 Sep 2026

yep you've basically got it. mass balance is the weights in front of the hinge line so the surfaces cg sits on or close to the hinge, thats what stops flutter. aerodynamic balance (horn balance, inset hinge, balance tab etc) has nothing to do with flutter, it just puts some of the surface area ahead of the hinge so the airflow helps you move it and the control forces are lighter. how i kept them apart for the exam: mass = weight = flutter, aero = air = forces. if the question mentions flutter, vibration or cg its mass balance. if it talks about stick forces or hinge moment its aerodynamic balance.