Module 12: Helicopter Aerodynamics, Structures and Systems

12.1Theory of Flight — Rotary Wing Aerodynamics

• Terminology (rotor disc, tip path plane, advancing/retreating blade, etc.)
• Aerodynamic principles of rotary wing flight
• Torque reaction and directional control (tail rotor, NOTAR, Fenestron)
• Gyroscopic precession and phase lag
• Dissymmetry of lift and blade flapping
• Ground effect and translational lift
• Autorotation principles
• Vortex ring state, blade stall, compressibility effects
• Coriolis effect on blade lead-lag
• Hovering, forward flight, climbing, descending, turning flight

12.2Flight Control Systems (ATA 67)

• Swashplate assembly: rotating and non-rotating stars
• Collective pitch control system
• Cyclic pitch control system
• Tail rotor / yaw control system
• Mixing unit and control rods
• Servo and hydraulic boost units
• Flight control rigging and adjustment
• Stability augmentation systems (SAS)
• Autopilot systems and AFCS (Automatic Flight Control Systems)
• Trim systems
• Active vibration control systems
• FBW (fly-by-wire) helicopter applications

12.3Blade Tracking and Vibration Analysis (ATA 18)

• Vibration theory: frequency, amplitude, sources
• Rotor track and balance fundamentals
• Blade tracking methods (flag, strobe, electronic)
• Vibration analysis techniques
• 1-per-rev, 2-per-rev, and higher-order vibration identification
• Span-wise and chord-wise balance
• Autobalance and automatic tracking systems
• Vibration health monitoring (VHM) systems

12.4Transmissions

• Main gearbox: types, construction, operation
• Intermediate and tail rotor gearboxes
• Freewheeling units (sprag clutches, roller clutches)
• Rotor brakes
• Transmission lubrication and cooling systems
• Drive shafts, couplings, and hangers
• Chip detectors and debris monitoring
• Health and Usage Monitoring Systems (HUMS) for transmissions
• Gearbox inspection and maintenance requirements
• Over-torque and over-speed procedures

12.5Airframe Structures

12.5(a)Structural Requirements

• Airworthiness requirements for helicopter structures (CS-27, CS-29)
• Structural classification: primary, secondary, tertiary
• Damage tolerance and safe-life concepts
• Crashworthiness requirements
• Fatigue life and component retirement
• Zonal and structural inspections

12.5(b)Construction Methods

• Fuselage construction: skin, frames, bulkheads, stringers, longerons
• Tailboom and tail pylon construction
• Composite materials in helicopter structures
• Bonded and riveted construction
• Structural repairs: temporary and permanent
• Rotor blade construction (spars, skins, honeycomb, erosion strips)
• Main rotor head components (hub, grips, dampers, bearings)
• Elastomeric bearings (spherical, lamiflex)
• Pylon mounting and vibration isolation
• Engine mounting systems

12.6Air Conditioning (ATA 21)

12.6.1Air Supply (ATA 21)

• Sources of bleed air (engine, APU)
• APU bleed air
• Ram air and fresh air ventilation
• Combustion heaters

12.6.2Air Conditioning (ATA 21)

• Heating and ventilation systems
• Vapour cycle cooling systems
• Air cycle machine cooling
• Temperature control and distribution
• Pressurisation systems (where applicable)
• Cabin environmental monitoring

12.7Instruments / Avionic Systems

12.7.1Instruments

• Pitot-static instruments (ASI, altimeter, VSI)
• Gyroscopic instruments (attitude indicator, HSI, turn coordinator)
• Engine instruments (torque, N1, N2, TOT/TGT, oil pressure/temp)
• Rotor RPM indicators (Nr, Nf)
• EFIS and glass cockpit displays
• Caution and warning systems

12.7.2Avionic Systems

• Communication systems (VHF, HF, SATCOM, intercom)
• Navigation systems (VOR, ILS, GPS, RNAV, ADF)
• TCAS and transponder systems
• Radio altimeter
• Weather radar
• ELT (Emergency Locator Transmitter)
• CVR and FDR (recorders)
• TAWS/EGPWS (Terrain Awareness)

12.8Electrical Power (ATA 24)

• DC generation (starter-generators, battery systems)
• AC generation (alternators, inverters)
• Power distribution and bus architecture
• Circuit protection (breakers, fuses, current limiters)
• External power connections
• Battery types and maintenance (lead-acid, NiCd, Li-ion)
• Emergency power systems
• Electrical load management

12.9Equipment and Furnishings (ATA 25)

12.9(a)Emergency Equipment (ATA 25)

• Emergency equipment (ELT, life rafts, flotation)
• Emergency flotation systems
• Life jackets and emergency breathing systems
• First aid kits, portable fire extinguishers
• Emergency exit marking and lighting

12.9(b)Cabin/Cargo Layout (ATA 25)

• Cabin layout and configuration
• Seats, harnesses, and restraint systems
• Cargo handling and securing
• Emergency exits and jettison systems
• Soundproofing and insulation

12.10Fire Protection (ATA 26)

• Fire detection systems (thermocouple, thermistor, continuous loop)
• Fire extinguishing systems (engine, APU, baggage)
• Fire extinguishing agents (Halon alternatives, dry powder)
• Fire zones and firewall construction
• Smoke detection systems
• Portable fire extinguishers
• Fire protection system testing and maintenance

12.11Fuel Systems (ATA 28)

• Fuel system layout (gravity feed, pressure feed)
• Fuel tanks (bladder, integral, crashworthy)
• Fuel pumps (boost, transfer, engine-driven)
• Fuel quantity indication systems
• Fuel jettison and crossfeed systems
• Fuel filtration and water separation
• Refuelling and defuelling procedures
• Crashworthy fuel system requirements

12.12Hydraulic Power (ATA 29)

• Hydraulic system architecture (single, dual, utility/flight)
• Hydraulic pumps (engine-driven, electric, hand)
• Reservoirs, accumulators, filters
• Hydraulic fluid types and maintenance
• Servo actuators for flight controls
• System monitoring and warnings
• Hydraulic system maintenance and troubleshooting

12.13Ice and Rain Protection (ATA 30)

• Ice formation and effects on helicopters
• Anti-icing systems (electrical, bleed air)
• De-icing systems (pneumatic boots, electro-thermal)
• Rotor blade de-icing/anti-icing
• Windshield wiper and rain repellent systems
• Engine intake anti-icing
• Ice detection systems

12.14Landing Gear (ATA 32)

• Skid-type landing gear (cross tubes, skid shoes)
• Wheeled landing gear (fixed, retractable)
• Ground resonance and shimmy dampers
• Float gear and emergency flotation systems
• Helicopter Ground Handling Wheels (HGW)
• Bear paw / snow shoes
• Shock absorbers and energy absorption

12.15Lights (ATA 33)

• External lighting (navigation, anti-collision, landing, search)
• Internal lighting (cockpit, cabin, instrument)
• Emergency lighting systems
• NVG-compatible lighting

12.16Reserved

12.17Integrated Modular Avionics (ATA 42)

• IMA concept and architecture
• Common computing resources
• Core processing and I/O modules
• ARINC 653 partitioning
• IMA advantages for helicopter systems
• Configuration and line replaceable modules

12.18On Board Maintenance Systems (ATA 45)

• Central maintenance computers
• Built-in test equipment (BITE)
• Data loading systems
• Health and Usage Monitoring Systems (HUMS)
• Vibration health monitoring integration
• Fault reporting and diagnosis

12.19Information Systems (ATA 46)

• Electronic Flight Bag (EFB)
• Aircraft communications addressing and reporting (ACARS)
• Cabin management systems
• Data network systems
• Software configuration management