14.4 Flight Controls, Autoflight, Fuel, Oil, Brakes, and Fire Protection

Complete the Aircraft Systems Picture

The practical test includes flight controls, autoflight, fuel and oil systems, landing gear/brakes, fire protection, and avionics, in addition to electrical, hydraulic, pneumatic, and pressurization knowledge. The dispatcher should understand how a defect changes capability, performance, and emergency options. Aircraft-specific architecture and procedures come from the assigned AFM and operating manuals; a generic transport diagram is not proof that every airplane has the same arrangement.

Flight controls and high-lift systems

Primary controls govern pitch, roll, and yaw. Secondary controls, such as flaps, slats, spoilers, and stabilizer trim, modify lift/drag or control balance. Modern aircraft may use mechanical linkages, powered hydraulic actuation, fly-by-wire electronics, or combinations. Redundancy can preserve control after a failure, but remaining laws/modes and restrictions are design-specific.

A flap or slat defect can change takeoff/landing speeds, field lengths, climb performance, and approach capability. A spoiler defect may affect braking, roll control, or descent planning. Review the actual MEL/AFM conditions and use the correct configuration in performance calculations. Do not assume a “small control surface” has negligible dispatch impact merely because the airplane can taxi normally.

Autoflight and flight management

Autopilot, flight director, and autothrottle/autothrust perform different tasks. The FMS can supply route, prediction, and guidance data without independently proving that the airplane is following the cleared route. Mode awareness matters: selected heading, lateral navigation, altitude capture, vertical navigation, and approach modes can have different behavior and constraints.

An autoflight defect can remove a low-visibility capability, increase crew workload, or affect authorization for a particular route. Whether one remaining channel supports CAT II, CAT III, or RVSM depends on the approved aircraft and operation, not a universal autopilot count. Dispatch evaluates the required capability and the actual MEL restriction; the crew follows approved mode-management and abnormal procedures.

Fuel systems and fuel availability

Aircraft may have wing, center, and other approved tanks, with pumps, transfer, crossfeed, venting, indication, and sometimes inerting or jettison systems. Crossfeed commonly allows an engine to draw from another supply path; it does not necessarily transfer fuel from tank to tank. The exact valve and pump logic is aircraft-specific.

Usable fuel quantity, fuel distribution, fuel availability to an engine, and fuel-quantity indication are separate issues. A full tank can be unusable under a particular failure or feed restriction. A pump deferral can impose minimum fuel, altitude, temperature, or operating-procedure conditions. A fuel imbalance can affect loading or aircraft handling and may indicate a leak rather than simply requiring a routine transfer.

Fuel sources and properties also matter. Use the approved fuel grade and limits, and consider temperature/freezing margins on long cold routes. A generic claim that all Jet-A and Jet-A-1 fuels have identical freezing points is incorrect. Do not substitute a nominal fuel-grade value for actual approved fuel/aircraft planning data where required. The dispatcher coordinates fuel-supplier and aircraft information through the approved process.

Oil systems and engine monitoring

Oil lubricates and cools engine components. Pressure, temperature, quantity, and consumption trends can indicate different problems; a normal quantity display does not prove adequate pressure. Turbine-engine and APU oil requirements are aircraft-specific, and ETOPS maintenance includes applicable consumption monitoring and predeparture checks.

A high-temperature indication or abnormal consumption can require maintenance action, an operating restriction, or an inflight abnormal response. Dispatch supplies suitable-airport, weather, terrain, and fuel support while the flightcrew follows the approved procedure. Avoid diagnosing a specific internal failure from one telemetry number without the authorized maintenance/crew process.

Landing gear, brakes, and anti-skid

Landing gear supplies support, retraction/extension capability, and steering functions as designed. Brakes absorb kinetic energy; anti-skid helps prevent wheel locking and preserve braking effectiveness under its operating conditions. Autobrake commands deceleration but does not make a wet or contaminated runway behave like a dry one.

A gear, steering, brake, or anti-skid defect can change takeoff/landing performance, maximum weight, runway selection, taxi restrictions, and rejected-takeoff capability. Use the correct approved defect-specific data. Brake energy depends on weight and speed; a high-speed rejected takeoff can require cooling/inspection before another departure. Follow the assigned aircraft's maintenance and dispatch conditions rather than inventing a universal waiting time.

Fire detection and suppression

Transport systems can detect and address fire in engines, APUs, cargo compartments, and specified aircraft areas using their approved architecture. A detection system can have redundancy and an extinguishing system has finite capacity or endurance. An indication, detector defect, or bottle/agent limitation requires the actual approved procedure and MEL conditions.

Fire or smoke in flight is time-critical. The PIC follows the aircraft's abnormal/emergency instructions and evaluates prompt landing at a suitable airport; dispatch supports airport, weather, runway, rescue, and route information. A suppression indication does not prove every fire is permanently extinguished or justify a long continuation for commercial convenience. ETOPS planning must also respect the applicable time-limited-system provisions, including cargo fire suppression where relevant.

Avionics and surveillance

Communication, navigation, terrain awareness, weather radar, collision avoidance, transponders, and displays support different operational functions. A flight-management route is not a weather-radar image; ADS-B broadcasts are not a crew–controller communication exchange; and an altitude-encoding fault can affect surveillance despite otherwise normal flight controls. Check the actual route and airport equipment requirements when evaluating a defect.

Group I and Group II implications

Group I includes reciprocating and turbopropeller airplanes; Group II includes turbojets. A propeller aircraft may use blade-angle changes and feathering to control thrust and engine-out drag. A windmilling propeller can impose substantial drag, and the approved procedure determines how the failure is handled. Do not use a turbojet's generic thrust or driftdown model unchanged for a turboprop. The assigned aircraft's data and certification basis determine the performance calculation.

Worked interaction scenario

A fictional flight has an anti-skid deferral and an autoflight limitation. Individually each item permits some operations. Together, the wet destination runway and planned low-visibility approach may be unavailable under the actual approved conditions. The dispatcher checks the combined restrictions, changes runway/destination/timing or aircraft as necessary, recomputes performance and fuel, and briefs the crew. This demonstrates systems knowledge through operational consequences instead of memorizing a parts inventory.

Propeller and Reciprocating Foundations

A propeller converts shaft power into thrust, with efficiency depending on blade angle, rotational speed, airspeed, and configuration. A constant-speed propeller adjusts blade angle to control selected RPM within its approved range; feathering reduces the drag of an inoperative propeller where that system is provided. Reciprocating-engine performance also depends on induction pressure, mixture and cooling within the approved system, while turboprops combine turbine shaft power with propeller thrust. These principles explain why an engine-out propeller state or a hot/high condition can significantly affect a Group I dispatch calculation. In simplified propeller models, maximum endurance relates to minimum power required, while maximum range has a different efficiency criterion. Do not substitute the jet’s constant-TSFC thrust model for the propeller aircraft’s approved performance charts.

Official References

Source check: 2026-10-12. Transport systems certification; Part 121 oxygen and equipment; FAA aircraft systems handbook. For operational use, apply current issued authorizations and the assigned aircraft’s approved data.