CAA NZ AME Licence Exam - Rotorcraft key terms

Contact between a rotor hub and the mast caused when flapping or teetering limits are exceeded during low-G or low-disc-loading flight. It can damage the mast and control linkages and has caused fatal accidents.

The upward angle a rotor blade assumes above the horizontal under aerodynamic lift. It increases with blade loading and is accommodated by the flapping hinge or flexible hub element to relieve bending loads at the root.

A hinge that allows each blade to move up and down relative to the hub, relieving root bending loads as advancing and retreating blade lift varies. Fully articulated rotors have one per blade.

A hinge permitting in-plane fore-and-aft blade motion to absorb Coriolis and drag forces as blade speed varies around the disc. Its damper prevents oscillation and ground resonance.

A flapping hinge whose axis is skewed relative to the blade axis, so flapping produces a pitch change. It is used to tune flapping and pitch coupling and improve stability.

A two-blade rotor where blades are joined rigidly to each other and see-saw about a single teetering hinge. It needs no individual flapping hinges but is sensitive to mast bumping.

A rotor in which each blade has its own flapping, lead-lag and pitch change bearings, allowing independent motion. It gives smooth operation and good control response but requires more maintenance and lubrication.

A destructive self-excited oscillation occurring when rotor lead-lag motion couples with airframe vibration on the ground. Correct landing gear and damper condition is critical; immediate liftoff or shutdown is the standard recovery.

The sideways drift of a single main rotor helicopter caused by tail rotor thrust. It is balanced in the hover by a small lateral cyclic input or by a built-in mast tilt.

The unequal lift produced on advancing and retreating sides of the disc in forward flight due to differing blade airspeeds. Flapping and cyclic feathering equalise lift and prevent roll.

The lateral force from tail rotor thrust that pushes the fuselage sideways in the hover. Pilots counter it with cyclic, and maintenance checks confirm it does not mask control rigging errors.

The assembly that converts non-rotating cyclic and collective control inputs into rotating blade pitch changes. It has a stationary and a rotating plate separated by bearings that must be inspected for wear and free play.

The rod connecting the rotating swashplate to a blade pitch horn, transmitting pitch inputs to the blade. Correct length, spherical bearing condition and locking are essential for tracking and control integrity.

Adjusting blade pitch so all blades follow the same flight path in the same plane. Poor tracking causes vibration and is corrected by pitch link adjustment or tab setting during ground and hover checks.

Balancing a rotating assembly in motion, usually by adding weights to the hub or blades after tracking, to reduce vibration. It is performed with specialised equipment and confirmed across a range of rotor speeds.

Balancing a component such as a blade or tail rotor about its axis of rotation while stationary. It is a prerequisite for dynamic balance and is checked by weighing or using a balance stand.

A rotor state in which upward airflow through the disc drives the blades without engine power. The freewheeling unit must engage correctly for safe entry, and rotor RPM is controlled by collective and airspeed.

A one-way clutch or sprag assembly that disconnects the engine from the rotor during autorotation while allowing the engine to drive the rotor normally. It must be tested for correct engagement and release.

A device that progressively engages the engine to the rotor system, allowing the rotor to be accelerated gently. It is used on piston and some turbine types and is inspected for slip and wear.

An instrument indicating the torque being transmitted to the main rotor, used to set power limits on turboshaft helicopters. It may sense oil pressure, shaft twist or engine output and requires calibration.

A gas turbine that delivers shaft power rather than jet thrust, used in most modern helicopters. Its output is governed to maintain rotor RPM, and it is monitored for torque, temperature and gas generator speed.

A turboshaft layout in which the power turbine is mechanically independent of the gas generator. It allows the rotor to stop while the engine runs and simplifies the freewheeling and starting arrangements.

The turbine stage that extracts energy from the exhaust gas to drive the output shaft. Its speed and temperature limits are monitored, and its blades are inspected for erosion and hot-section distress.

A maintenance procedure using water or solvent to remove salt, dirt and deposits from compressor blades, restoring performance and reducing corrosion. It follows approved procedures and is followed by a drying run.

Disruption of smooth airflow through the compressor, causing a bang, surge or power loss. Causes include inlet distortion, damaged blades and excessive acceleration, and the engine must be inspected after an occurrence.

Damage to engine or rotor components from ingested or impact debris such as stones, birds or loose hardware. It is found by borescope inspection and must be assessed against limits before further flight.

A key turbine health indicator measured at the turbine inlet or exhaust. Rising values for a given power setting suggest deterioration, and exceeding limits can cause hot-section damage.

Gas generator and power turbine speeds expressed as percentages of design RPM. Both are monitored for starting, governing and overspeed protection, and their indications are checked during run-up.

A control system that adjusts engine power to hold rotor speed near the selected value despite load changes. Its rigging and response are checked on the ground and in flight after maintenance.

The control lever that changes blade pitch equally on all blades, increasing or decreasing total lift. It also controls rotor RPM in autorotation and incorporates the throttle or governor twist grip.

The control that varies blade pitch cyclically around the disc to tilt the rotor and direct the helicopter. Its rigging determines control range and is checked for correct sense and freedom of movement.

The means of countering main rotor torque, typically a tail rotor, fenestron or NOTAR system. Its drive shaft, gearboxes and control rigging are safety-critical inspection items.

A small auxiliary rotor providing anti-torque thrust and yaw control. It turns at high speed, so balance, blade condition, pitch change bearings and drive shaft couplings are closely inspected.

The pressure system supplying airspeed, altimeter and vertical speed indications. In helicopters, pitot heating, drain and static port condition matter because low-speed and hovering flight rely on accurate pressure readings.

The sensors and computers that derive airspeed, altitude and temperature for displays and flight controls. Its pitot and static lines must be leak-tested and kept clear of moisture and blockage.

A cockpit display of engine-to-rotor torque used as the primary power limit. The sensor, wiring and indicator must be calibrated, as overtorque can damage the transmission.

A magnetic plug or sensor in a gearbox or engine oil system that collects ferrous particles and may trigger a warning. Findings indicate internal wear and require investigation before further flight.

A magnetic drain plug that captures ferrous debris in oil systems. It is checked at scheduled intervals and at every oil change, and unusual debris is reported and investigated.

Laboratory testing of oil samples for wear metals, contamination and viscosity changes. Trends help predict component failure and complement chip detectors and filter inspections.

Visual inspection of internal engine or structure areas using a fibre-optic or video scope. It is used to examine compressor and turbine blades and combustion chambers without disassembly.

A mandatory directive issued by the state of design and adopted by the NZCAA, requiring inspection or modification within a stated time. Compliance is recorded and is required for continued airworthiness.

Manufacturer-issued information on inspection, modification or improvement. It is advisory unless made mandatory by an Airworthiness Directive or by the operator's approved maintenance programme.

A certification by an appropriately rated licence holder that maintenance has been completed and the aircraft or component is fit for return to service. It must identify the work and any limitations.

A recorded description of maintenance performed, signed by the authorised person, including references to approved data and any defects. Accurate entries are essential for traceability and continued airworthiness.

Maintenance information accepted by the authority, such as the manufacturer's manual, service documents and approved modifications. Work must be carried out to approved data, not unauthorised guesswork.

The scheduled inspection and maintenance plan approved for an operator, defining intervals and tasks. It may be based on manufacturer recommendations and is amended as experience and directives require.

Twelve human-factor traps identified in aviation maintenance, including complacency, fatigue, pressure, distraction and lack of knowledge. Recognising them helps engineers avoid errors and report hazards.

Awareness of the current task, environment and risks, including aircraft state and team workload. Loss of it contributes to skipped steps, tool left in aircraft and wrong-aircraft maintenance.

A safety approach that distinguishes honest error from reckless or deliberate violation, encouraging reporting without fear. It supports learning from maintenance errors while preserving accountability.

A system of duty limits, rest requirements and self-reporting to control the effects of tiredness on maintenance work. Fatigue impairs judgement, attention and error detection, especially on night shift.

Procedures such as shadow boards, checklists and signed tool issue that ensure no tools or hardware remain in an aircraft. Lost items can cause foreign object damage or jam flight controls.