Dispatcher License (DL)

Correct: Propulsive efficiency is a measure of how effectively the engine’s energy is converted into aircraft motion. By accelerating a large mass of air only slightly, the engine generates thrust with much lower kinetic energy waste than a turbojet, which accelerates a small mass of air to very high speeds.

Correct: According to FAA standards, galvanic corrosion occurs when two dissimilar metals are in contact in the presence of an electrolyte; the less noble metal, which is the aluminum in this pairing, becomes the anode and undergoes oxidation.

Incorrect: The strategy of identifying stainless steel as a sacrificial anode is incorrect because steel is more noble than aluminum in the galvanic series. Focusing only on high-resistance barriers and thermal oxidation confuses electrical power dissipation with electrochemical corrosion processes. Opting for the explanation that aluminum absorbs electrons to become brittle misidentifies the anodic reaction, which involves the loss of electrons and metal ions.

Correct: High aspect ratio wings are more efficient because they have a longer span relative to their chord. This geometry reduces the strength of the vortices that form at the wingtips. Since these vortices are the source of induced drag, a higher aspect ratio results in less drag for the same amount of lift produced.

Correct: The no-back brake is a critical safety component that prevents aerodynamic loads from back-driving the ball screw, which ensures the control surface remains in its commanded position when the motor is not energized.

Incorrect: Relying solely on mechanical hard stops describes the function of travel limits designed to prevent structural damage from over-extension. The strategy of synchronizing extension speeds is typically managed by electronic control units using feedback sensors rather than a friction-based brake. Choosing to disconnect the drive during an obstruction refers to the operation of a torque limiter or shear pin.

Correct: Upward elevator deflection changes the effective camber of the horizontal stabilizer to generate a downward aerodynamic force. This force creates a moment around the lateral axis that rotates the nose upward.

Incorrect: The strategy of suggesting that upward deflection increases lift on the tail is aerodynamically incorrect and misidentifies the axis of rotation as longitudinal. Simply conducting an analysis based on shifting the center of pressure forward fails to account for how control surfaces actually generate moments. Opting for an explanation based on drag and inertia ignores the primary role of lift-induced moments in pitch control.

Takeaway: Pitch control is achieved by varying the aerodynamic force on the tail to create a moment around the lateral axis.

Correct: Fuel System Icing Inhibitor (FSII) works by partitioning into any water present in the fuel. Because water is less soluble in fuel at low temperatures, it can freeze and block filters. FSII lowers the freezing point of this water, ensuring it remains liquid and passes through the system safely.

Correct: A constant-speed propeller utilizes a governor to automatically adjust the blade pitch. This mechanism ensures the engine maintains a constant RPM by increasing or decreasing the air load on the blades.

Incorrect: Relying solely on a ground-adjustable propeller is incorrect because the pitch can only be changed while the aircraft is stationary. The strategy of using a fixed-pitch propeller is inefficient because the blade angle is permanent and cannot adapt to different flight conditions. Opting for a controllable-pitch propeller allows for manual adjustments by the pilot but lacks the automatic governing system to maintain a steady engine speed.

Takeaway: Constant-speed propellers use a governor to automatically adjust blade pitch, maintaining a steady engine RPM throughout different flight attitudes.

Correct: Under Federal Aviation Administration (FAA) regulations, any modification that changes the empty weight or center of gravity requires an immediate update to the aircraft’s weight and balance records. This ensures that the pilot has accurate data to calculate the actual weight and balance for every flight, which is a critical component of airworthiness and safe operation.

Correct: Under 14 CFR Part 39, the FAA issues Airworthiness Directives to correct unsafe conditions in aircraft products. These directives are mandatory legal requirements. If an operator fails to perform the required structural inspections or modifications within the specified timeframe, the aircraft’s airworthiness certificate is no longer valid. This regulatory mechanism ensures that critical structural threats, like fatigue cracking, are mitigated to maintain the safety standards established during the aircraft’s certification.

Correct: Dissymmetry of lift occurs because the advancing blade experiences a higher relative wind speed than the retreating blade. To compensate, the flapping hinge allows the advancing blade to rise, which creates a downward flow of air relative to the blade. This motion effectively decreases the angle of attack and the lift produced. Simultaneously, the retreating blade flaps down, increasing its angle of attack and lift, resulting in a balanced lift distribution across the rotor disc.

Correct: In high-frequency applications common in modern US aviation electronics, grounding a shield at both ends is necessary to provide a low-impedance path for induced currents, effectively attenuating electromagnetic interference.

Incorrect: Relying solely on a single-point ground is an approach suited for low-frequency audio circuits but fails to protect against high-frequency EMI. Simply conducting the shield to a DC power return is incorrect as it does not provide a proper path for interference. The strategy of leaving the shield ungrounded entirely is a failure in design that allows the shield to act as an antenna.

Correct: The Generator Control Unit monitors the output voltage and adjusts the DC current flowing through the stationary exciter field. This change in current varies the strength of the magnetic field. This process controls the voltage induced in the rotating exciter armature and the main generator output.

Correct: The propeller governor is the primary component that senses engine speed via internal flyweights and adjusts the flow of high-pressure oil to the propeller hub to change the blade angle, thereby maintaining a constant RPM.

Incorrect: Relying on the propeller synchronizer is incorrect as this system is designed to match the speeds of two or more engines rather than governing the speed of an individual engine. Selecting the feathering pump is a misconception because this auxiliary component is used to provide oil pressure for feathering the propeller when the engine is not running. Choosing the beta feedback ring is inaccurate because this component is primarily used in turboprop systems to provide position feedback during ground or reverse operations rather than governing RPM in the flight range.

Takeaway: The propeller governor maintains a constant engine speed by automatically adjusting the propeller blade pitch using hydraulic pressure.

Correct: During a pull-up maneuver, the lift forces cause the wing to bend upwards, placing the upper skin under intense squeezing or compressive stress. High compressive strength is essential to ensure the skin does not buckle or fail, maintaining the structural integrity of the wing box.

Incorrect: Focusing only on tensile forces is incorrect because the upper surface of a wing experiencing positive lift is under compression rather than tension. Simply conducting an analysis of wave drag is irrelevant here as compressive strength is a mechanical property of the material, not an aerodynamic shape factor. The strategy of assuming lateral expansion of ribs is technically flawed because ribs are designed for rigidity and do not use compressive strength to change surface area.

Takeaway: Compressive strength is critical for the upper wing skin to resist buckling under the inward-pressing loads generated by upward wing bending.

Correct: Differential ailerons are designed to counteract adverse yaw. The downward-deflected aileron produces more lift and consequently more induced drag, which pulls the nose away from the turn. By deflecting the upward aileron further, the aircraft generates additional profile drag on the inside of the turn to balance the forces as per standard aerodynamic principles recognized by the FAA.

Incorrect: The strategy of addressing aileron reversal involves structural stiffening or using inboard ailerons rather than differential travel. Simply conducting checks for Dutch roll would involve looking at the relationship between lateral and directional stability, typically managed by a yaw damper. Focusing only on parasite drag reduction is incorrect because differential travel actually increases total drag to achieve coordinated flight.

Correct: The Zero Fuel Weight calculation is essential because fuel consumption during flight causes a shift in the Center of Gravity. This verification ensures the aircraft remains within its certified longitudinal stability limits from takeoff until the tanks are empty.

Correct: Pitting corrosion creates surface irregularities that disrupt the smooth flow of air, increasing skin friction and potentially causing the boundary layer to separate earlier than designed.

Incorrect: Relying on the idea that pitting significantly changes induced drag is incorrect, as induced drag is primarily a function of lift production rather than surface texture. The strategy of suggesting a shift in the aerodynamic center is flawed, as localized surface pitting does not fundamentally alter the chord-wise pressure distribution. Focusing on wave drag is inappropriate for most general aviation scenarios, especially since wave drag only becomes a factor as the aircraft approaches the speed of sound.

Takeaway: Pitting corrosion on an airfoil surface increases drag and degrades lift characteristics by prematurely disrupting the laminar boundary layer.

Correct: In fuel-injected engines, the fuel is discharged at the intake ports. This prevents the refrigeration icing that occurs in carburetors when fuel evaporates in the venturi, which can drop the temperature significantly. By moving the evaporation point to the cylinder head, the system utilizes engine heat to keep the intake clear.

Correct: Increasing the aspect ratio reduces the intensity of wingtip vortices, which are a primary source of induced drag. By spreading the lift over a longer span, the downward deflection of air (downwash) is reduced, leading to a more efficient lift-to-drag ratio.

Incorrect: The strategy of claiming a reduction in parasite drag is incorrect because increasing the wingspan adds to the total wetted area, which increases skin friction. Focusing only on the critical Mach number is misplaced as aspect ratio modifications do not inherently change the thickness-to-chord ratio or wing sweep. Opting for the elimination of wave drag is technically flawed because wave drag is a result of compressibility at high speeds and is not resolved by aspect ratio changes.

Takeaway: Increasing the aspect ratio of a wing reduces induced drag by minimizing the energy lost to wingtip vortices.

Correct: Under 14 CFR 25.1447, flight crew masks in transport category aircraft must be quick-donning to ensure that, in the event of rapid decompression, the crew can establish oxygen flow and protection immediately without interfering with their ability to fly the aircraft. This standard requires that the mask can be deployed and secured using only one hand within a five-second window, which is critical during the high-stress environment of a rapid decompression.