Part-66 Module 11: turbine aeroplane structures and systems

Module 11 is 140 multiple-choice questions in 175 minutes, the largest Part-66 exam. It follows the ATA chapters of a jet transport.

High-speed flight and controls

• Critical Mach number: free-stream Mach at which local flow first reaches Mach 1. Sweep and supercritical aerofoils raise it.
• Mach tuck (nose-down at high Mach) is countered by Mach trim. High-speed buffet and stall speeds meet in the coffin corner.
• Swept wings tip-stall; fences, vortex generators and stick pushers (T-tails, deep stall) help. A yaw damper stops Dutch roll.
• Mass balance prevents flutter; balance, servo and trim tabs reduce or hold control forces.

Structures (ATA 51–57)

• Fail-safe (multiple load paths), safe-life (retire before a set life) and damage tolerance (find cracks before critical).
• Locations: fuselage station, buttock line, waterline, wing station; ATA zones (100 lower fuselage, 500/600 wings).
• Semi-monocoque: skin carries shear and hoop tension; frames, stringers and tear straps. Ultimate load = limit load × 1.5.
• Plug doors cannot open when pressurised; cabin windows have a fail-safe inner pane and vent hole.

Air conditioning and pressurisation (ATA 21)

• Packs: bleed air cooled in heat exchangers and expanded across an air cycle machine turbine; water separator removes moisture; trim air sets zone temperature.
• The outflow valve controls cabin pressure. Positive and negative relief valves protect the hull. Normal cabin altitude ≤ 8,000 ft; warning at about 10,000 ft.

Avionics and electrical (ATA 22–24, 31, 34)

• Pitot-static feeds the ADC; IRS needs a stationary alignment. TCAS gives vertical RAs; EGPWS uses a terrain database.
• AC: 115 V 400 Hz three-phase from IDGs; TRUs give 28 V DC; a static inverter gives AC from the battery. The RAT deploys on total power loss. GCUs protect generators; load shedding drops galleys first.

Fire, flight controls, fuel (ATA 26–28, 47)

• Cargo: smoke detectors, Halon high-rate then metered discharge (Class C). Lavatory bins have heat-activated extinguishers.
• Powered controls need artificial feel (q-feel). After disturbing controls: independent inspection. Flap asymmetry protection locks the drive.
• Integral wing tanks, boost pumps, crossfeed, capacitance gauging (mass), surge tanks, inerting with nitrogen-enriched air. Tank entry is a confined-space task.

Hydraulics, ice, gear (ATA 29, 30, 32)

• Phosphate ester fluid at 3,000 psi, engine-driven piston pumps, EMDPs, PTU, accumulators (check pre-charge depressurised), priority valves and fuses.
• Leading edges use hot bleed air; probes and windows are electrically heated; holdover time limits ground anti-icing.
• Oleo struts (oil + nitrogen), anti-skid, autobrake, carbon brakes with wear pins, fusible plugs, nitrogen tyre inflation checked cold.

Lights, oxygen and others (ATA 33–46)

• Navigation lights: left red, right green, tail white. Emergency lighting has its own batteries.
• Passenger oxygen from chemical generators (masks drop at ~14,000 ft); crew gaseous oxygen with diluter-demand masks; keep oil away from oxygen.
• Pneumatics (36), water and waste (38), central maintenance computer and BITE (45), IMA with partitioning and AFDX (42), cabin systems (44) and information systems/EFB (46).