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One of my 2018 goals that I know of already is to become a licensed aircraft dispatcher. The aircraft dispatcher exam (ADX) shares many of the same questions as the airline transport pilot (ATP) exam, as thirteen areas for testing are identical. In preparation for 2017 rolling into 2018, I will be posting a series of blog post lessons, which will include 10-20 questions each, the correct answers, and some discussion and explanations.

Aerodynamics and Aircraft Systems – Overview of Subsections

The Aerodynamics and Aircraft Systems section covers a lot of topics, called subsections.  Some of the questions may be basic private pilot stuff, but there are questions on turbine engine systems, de-ice, anti-ice, glass cockpit systems and more.  Below is the list of subsections and the number of questions in my question bank:

• Ailerons, Flight Controls and Trim Tabs (14 questions)
• Wing Lift Devices (20 questions)
• Lift and Drag (20 questions)
• Stall Speeds (14 questions)
• Load Factor (6 questions)
• Turns and Climbs (11 questions)
• Stability and Loading (13 questions)
• Takeoff and Landing Performance (14 questions)
• Maximum Range (7 questions)
• Propeller Pitch, Engine Performance and Turbochargers (6 questions)
• Multi-Engine Airplane Operation (14 questions)
• Turbine-Engine Operation (11 questions)
• Compressor Stall (5 questions)
• Mach Flight (12 questions)
• Hydroplaning (8 questions)
• Thrust Reversers (3 questions)
• Aircraft Icing and Performance, De-icing, Anti-icing (20 questions)
• Pitot-static and Altimeter Systems (5 questions)
• Glass Cockpit Systems (9 questions)

Aerodynamics and Aircraft Systems – Ailerons, Flight Controls and Trim Tabs

Question 1.  What is the purpose of the servo tab?

a. Move the flight controls in the event of manual reversion.
b. Reduce control forces by deflecting the proper direction to move a primary flight control.
c. Prevent a control surface from moving to a full deflection position due to aerodynamic forces.

The correct answer is ‘b’ – Reduce control forces by deflecting the proper direction to move a primary flight control. Servo tabs reduce control forces by deflecting in the proper direction to move a primary flight control. You can read more about servo tabs on Wikipedia.

Question 2. When are inboard ailerons normally used?

a. Low-speed flight only.
b. High-speed flight only.
c. Low-speed and high speed flight.

The correct answer is ‘c’ – Low speed and high-speed flight. I don’t know the point of this question, but I guess that makes the answer easy to remember (for me). The question is there, I suppose, because some commercial aircraft have inboard ailerons, and some don’t. Airbus aircraft do not have inboard ailerons because they move the flaps differently (straight back as opposed to perpendicular to the hingeline, like a Boeing).

Question 3.  Precise roll control using a rudder on a transport category airline

a. can be effective when turbulence is encountered.
b. is difficult and therefore not recommended.
c. should be considered to assist the yaw damper.

The correct answer is ‘b’ – is difficult and therefore not recommended. Remember that differential lift for roll control is typically obtained by some type of ailerons or spoilers movement. Rudder is used to control yaw about the vertical axis. Using rudders primarily to achieve roll control can contribute to dihedral effect, which can lead to a few problems, including the tailwagging, side-to-side dutch roll.  In jets, we use a yaw damper to increase stability and prevent these tendencies.

Question 4. Which direction from the primary control surface does an elevator adjustable trim tab move when the control surface is moved?

a. Remains fixed for all positions
b. Opposite direction.
c. Same direction

The correct answer is ‘a’- Remains fixed for all positions. This question seemed like basic common sense for me, so I was able to come up with the answer immediately. Trim tabs remain in a fixed position relative to the control surface.

Question 5. Which direction from the primary control surface does a servo tab move?

a. Opposite direction.
b. Same direction.
c. Remains fixed for all positions.

The correct answer is ‘a’ – Opposite direction. Servo tabs work to reduce the control forces required from the pilot, and move in the opposite direction from the primary control surface.

Question 6.  When are outboard ailerons normally used?

a. High-speed flight only.
b. Low-speed flight only.
c. Low-speed and high-speed flight.

The correct answer is ‘b’ – Low-speed flight only. To remember the answer to this question, I think about this little diagram I found on the internet. The outboard aileron is called the low speed aileron.  Don’t  get confused though, remember question 2? Inboard ailerons are used for low-speed and high speed flight.

Question 7. Which of the following is considered an auxiliary flight control?

a. Upper rudder.
b. Ruddervator
c. Leading-edge flaps.

The correct-answer is ‘c’- Leading-edge flaps.  I have never flown a V-tail airplane, so I had never heard of a “ruddervator” until this study session, but it is a hybrid of elevator and rudder, both primary flight controls. I’ve also never flown a split rudder airplane, but again, I know that rudders are primary flight controls. Flaps are NOT primary flight controls, they are secondary (along with trim devices). In the case of this question, auxiliary means the same thing as secondary. Leading edge flaps ae secondary or auxiliary flight controls.

Question 8. Which direction from the primary control surface does anti-servo tab move?

a. Remains fixed for all positions.
b. Same direction.
c. Opposite direction.

The correct answer is ‘b’ – Same direction. The key to answering this question correctly is reading it closerly. The Pilot’s Handbook of Aeronautical Knowledge (PHAK) says in chapter Five that anti-servo tabs move in the same direction as the primary control service.

Question 9. What is the purpose of an anti-servo tab?

a. Move the flight controls in the event of manual reversion.
b. Reduce control forces by deflecting in the proper direction to move a primary flight control.
c. Prevent a control surface from moving to a full-deflection position due to aerodynamic forces.

The correct-answer is ‘c’- Prevent a control surface from moving to a full-deflection position due to aerodynamic forces. Another question right out of PHAK, Chapter 5. Anti-servo tabs work to decrease the sensitive of the control surface, and preventing a surface from moving to a full-deflection position.

Question 10. Why do some airplanes equipped with inboard/outboard ailerons use the outboards for slow flight only?

a. Increased surface area provides greater controllability with flap extension.
b. Aerodynamic loads on the outboard ailerons tend to twist the wingtips at high speeds.
c. Locking the outboard ailerons in high-speed flight provides for variable flight control feel.

The correct answer is ‘b’ – Aerodynamic loads on the outboard ailerons tend to twist the wingtips at high speeds. This goes back to the diagram in question 6. On planes with both inboard and outboard ailerons (Boeings), the outboard ailerons tend to be locked into the neutral position during high-speed flight to avoid twisting the wingtips. This isn’t a real concern at lower speeds.

Question 11. What is the purpose of a control tab?

a. Reduce control forces by deflecting in the proper direction to move a primary flight control.
b. Prevent a control surface from moving to a full-deflection position due to aerodynamic forces.
c. Move the flight controls in the event of manual reversion.

The correct-answer is ‘c’- Move the flight controls in the event of manual reversion. Control tabs are linked directly to the pilot controls.

Question 12. Which of the following is considered a primary flight control?

a. Dorsal fin.
b. Elevator.
c. Slats.

The correct answer is ‘b’ – a question straight out of the Private Pilot Exam! This was an easy one – straight out of PHAK chapter 5.

Question 13. What is the purpose of an elevator trim tab?

a. Modify the downward tail load for various airspeeds in flight eliminating the flight-control pressures.
b. Provide horizontal balance as airspeed is increased to allow hands-off flight.
c. Adjust the speed tail load for different airspeeds in flight allowing neutral control forces.

The correct answer is ‘a’- Modify the downward tail load for various airspeeds in flight eliminating the flight-control pressures.  The answer to this question was simple to me, as I know from flying the Cessna, the elevator trim tab holds the elevator in proper position so that the pilot doesn’t need to put control pressure on the plane the whole flight.

Question 14:  Which of the following are considered primary flight controls.

a. Tabs.
b. Flaps.
c. Outboard ailerons.

The correct-answer is ‘c’- Outboard ailerons.  I know from my private pilot lessons that primary flight controls are elevators, ailerons, and rudders. This question is obviously designed to trick people who remember that not all planes have outboard ailerons. But it doesn’t matter. Tabs and flaps are not primary flight controls, and ailerons are primary flight controls (inboard or outboard).