Flight control balancing

Question 1

Unbalanced control surfaces lead to what?

Answer 1

-Control surface fluttering
-Fatigue cracking of mounting structure
-Loss of the control surface itself or the whole wing/stabilizer structure

Question 2

When should flight control limits be checked? List at least 3 reasons

Answer 2

-After paintings
-After repairs
-Loss of balance weight

Question 3

Different aircraft configurations may have different control surface limits. T/F?

Answer 3

True

Question 4

The moment of a flight control should be checked if it is being __________. Even if its being exchanged with a flight control from same type aircraft

Answer 4

Should be checked if it is being replaced

Question 5

What is a hinge line?

Answer 5

A line that extends through the pivot point of the surface hinge

Question 6

What is a balancing fixture?

Answer 6

A device that supports the control surface while allowing it to pivot around the hinge line

Question 7

Overbalance is when the center of mass is what?

Answer 7

When the center of mass is ahead of the of the hinge line

Question 8

Underbalance is when the center of mass is what?

Answer 8

When the center of mass is behind of the hinge line

Question 9

Moment is defined as the measure of torque that does what?

Answer 9

Measure of torque that the control imbalance puts on the control surface

Question 10

What is balance weight?

Answer 10

Material that is added to the front of the hinge line to bring the surface moment into limits

Question 11

What is positive and negative stability?

Answer 11

Positive stability is defined as the tendency to return to equilibrium while negative stability is the tendency to continue in the displacement direction

Question 12

What is meant by AERODYNAMIC BALANCE?

Answer 12

The surface area AHEAD of the hinge line to assist in pilot control

Question 13

What is the formula for calculating moment?

Answer 13

(Xoz/ 16oz/lb) x distance between hinge line and trailing edge

Question 14

Some manufactures refer to
overbalance as negative (-) moment, and others positive (+) moment. T/F?

Answer 14

True

Question 15

Generally speaking, there are three methods of balancing, what are they?

Answer 15

Scale method
Trial weight method
Component method

Question 16

Describe the scale method:

Answer 16

This method revolves around the use of a scale to weigh the amount of imbalance in level attitude

Question 17

Describe the trial method:

Answer 17

This one involves adding weight to either the leading or trailing edge of the control surface depending whether it is over balanced or underbalanced

Question 18

Describe the component method:

Answer 18

The use of a balance beam on a control surface in which a weight is added to the beam and slid around until the surface is balanced

Question 19

Most flight controls require weight in front of the hinge line to properly balance the surface. These are called what?

Answer 19

Counterweights

Question 20

Counterweights need to be very heavy and often have limited space to occupy. Hence, are often made from what?

Answer 20

Heavy high density material such as steel. depleted uranium, tungsten, lead. etc

Question 21

Control surfaces balance moments MUST fall within the manufacturer specifications to be considered airworthy. And if they don’t you can resolve these issues by doing what?

Answer 21

Adding counterweights (usually ahead of the hinge line
Removing counterweights (if the said surface is overbalanced

Question 22

Do control tabs need to be balanced?

Answer 22

Yes, some may require counterweights to prevent flutter

Question 23

When are ICCs required and what are the 4 main checks that are required?

Answer 23

Required after maintenance is performed that may have disturbed the flight controls. There must be a check for Correct assembly, safety devices, correct sense and range of travel