inspection requirements for helicopter after incidents 1

FOR TRAINING PURPOSE ONLY Malaysian Institute of Aviation Technology

AJD21603 ROTORCRAFT SERVICING, MAINTENANCE AND ROLE EQUIPMENT

WEEK 10INSPECTION REQUIREMENT FOR HELICOPTER

AFTER INCIDENTS


LESSON OBJECTIVE & OUTCOMEOBJECTIVE:

1. GAIN KNOWLEDGE ON VARIOUS TYPES OF HELICOPTER INCIDENTS AND ACTIONS TO BE TAKEN AFTER SUCH INCIDENTS OCCURS.

OUTCOME:1. EXPLAIN THE MAINTENANCE ACTIONS TO BE

TAKEN AFTER A HELICOPTER IS INVOLVED IN AN INCIDENT.


INTRODUCTIONIN THIS LESSON WE WILL DISCUSS THE INSPECTIONS TO BE CARRIED OUT AFTER A HELICOPTER IS INVOLVED IN ANY OF THE FOLLOWING INCIDENTS;

1.1. HEAVY LANDINGSHEAVY LANDINGS

2.2. MAIN AND TAIL ROTOR STRIKESMAIN AND TAIL ROTOR STRIKES

3.3. TRANSMISSION OVER-TORQUETRANSMISSION OVER-TORQUE

4.4. SUDDEN MAIN ROTOR STOPPAGESUDDEN MAIN ROTOR STOPPAGE


INTRODUCTION (CONT)Aircraft are designed to withstand flight and landing loads within specified limits; these limits are calculated to allow for all normal maneuvers and exercises which may be undertaken by that aircraft and include safety factors to allow for unforeseen circumstances. If design limits are exceeded due to abnormal occurrences, the integrity of the structure may be jeopardized and safety impaired.


INTRODUCTION (CONT)Any report or evidence on the aircraft which suggests that the design limits have been exceeded or equipment damaged should, therefore, be followed by a careful inspection appropriate to the nature of the occurrence and in accordance with the Approved Maintenance Manual.


HARD LANDING


PRELIMINARY STEPSThe appropriate aircraft Maintenance Manual and other relevant literature, such as Service Bulletins, should be consulted to ascertain the particular inspections which are necessary and the areas where damage has been known to occur in similar circumstances on aircraft of the same type. The aircraft should then be viewed for obvious damage such as distortion or twisting of the main structure, before carrying out the detailed inspections applicable to the particular incident.


HARD/HEAVY LANDINGAn aircraft landing gear is designed to withstand landing at a particular aircraft weight and vertical descent velocity. If either of these parameters is exceeded during a landing, then it is probable that some damage may be caused to the landing gear or its supporting structure. Overstressing may also be caused by landing with drift or landing in an abnormal attitude, e.g. nose or tail wheel striking the runway before the main wheels


HARD LANDING (CONT)In all cases of suspected heavy landings, the flight crew should be consulted for details of aircraft weight, fuel distribution, landing conditions and whether any noises indicative of structural failure were heard.The damage which may be expected following a heavy landing would normally be concentrated around the landing gear, its supporting structure in the fuselage and the engine mountings.


HARD LANDING (CONT)Secondary damage may be found on the fuselage upper and lower skin and structure and wing skin and structure, depending on the configuration and loading of the aircraft. On some aircraft it is specified that, if no damage is found in the primary areas, the secondary areas need not be inspected; but if damage is found in the primary areas, then the inspection must be continued


INSPECTION AREA – LANDING GEARExamine tires for excessive creep, flats, bulges,

cuts, pressure loss, excessive growth and security of balance weights/patches.Examine wheels and brakes for cracks, other damage and fluid leaks.Examine axles, struts and stays for distortion and other damage.Check shock struts for fluid leaks, scoring and abnormal extension.


INSPECTION AREA – LANDING GEARExamine landing gear attachments for signs of cracks, damage or movement. In some instances this may require removal of certain bolts in critical locations, for a detailed magnetic crack detection test.


INSPECTION AREA – LANDING GEARExamine structure in the vicinity of the landing gear attachments for signs of cracks, distortion, movement of rivets or bolts and fluid leakage.Examine doors and fairings for damage and distortion.Jack the aircraft and carry out retraction and nose-wheel steering tests in accordance with the approved Maintenance Manual; check for correct operation of locks and warning lights, clearances in wheel bays, fit of doors and signs of fluid leaks.


FUSELAGE AREACheck that the inertia switches for the fire extinguishers, emergency lights, etc., have not tripped.Check instruments and instrument panels for damage and security..Examine for evidence of strike damage from the main rotor blades and if damage is found check for cracks, security and symmetry.Check ducts and system pipes for damage, security and fluid leaks.


FUSELAGE AREAExamine fuselage skin for wrinkling or other damage, particularly at skin joints and adjacent to landing gear attachments and centre section.Examine pressure bulkheads for distortion and cracks.Examine, for distortion and cracks, the supporting structure for heavy components such as galley modules, batteries, water tanks, fire extinguishers, auxiliary power units, etc.


FUSELAGE (CONTINUE)Check fit of access doors, emergency exits, etc. and surrounding areas for distortion and cracks.Check loading and unloading operation of cargo containers and condition of cargo restraint system.Check gyroscopic instruments for erection time, precession and unusual noises


ENGINECheck engine controls for full and free movement.Examine engine mountings and pylons for damage and distortion. Tubular members should be checked for bow greater than prescribed limits and cracks at welds. Mounting bolts and attachments should be checked for damage and evidence of movement.On turbine engines check freedom of rotating assemblies.


ENGINE – N1


ENGINE – N2


ENGINE


ENGINEExamine engine cowlings for wrinkling and distortion and integrity of fasteners.Check for oil, fuel and hydraulic fluid leaks.Check oil system filters/chip detectors.


ENGINE RUNSProvided that no major structural distortion has been found, engine runs should be carried out in accordance with the appropriate Maintenance Manual, in order to establish the satisfactory operation of all systems and controls. A general check for system leaks should be carried out while the engines are running and on turbine engines the run-down time should be checked..


MAIN ROTOR BLADESRemove the rotor blades and examine them for twisting and distortion. Check the surface for cracks, wrinkles, or other damage and check the security of the skin attachment rivets or structural bonding. If the main rotor blades are badly damaged through impact with the tail boom or ground, certain components in the transmission may be shock-loaded and it is sometimes specified that, for example, the main rotor shaft, pitch change rods and main gearbox mounting bolts, should also be removed for inspection.


MAIN ROTOR BLADES


MAIN ROTOR HEADDisconnect pitch change rods and dampers and check that the flapping hinges, drag hinges and blade sleeves move freely, without signs of binding or roughness.Examine the rotor head and blade stops for cracks or other damage and the dampers for signs of fluid leaks. Damage in this area may be an indication of further damage inside the main gearbox.


MAIN ROTOR HEAD


TAIL ROTORExamine the blades for damage and security and the coning stops for evidence of damage. Damage to the tail rotor blades which is beyond limits, will normally entail either inspection or replacement of the hub, pitch change links, tail rotor gearbox and drive shaft.


SKID TYPE LANDING GEARWith the helicopter jacked clear of the ground, check cross tubes for excessive bowing, fasteners for integrity and security and abrasion plates for wear. Where Float Gear is fitted, check for leaks, fabric scuffing and integrity of attachment straps.


MAIN & TAIL ROTOR STRIKESIMPACT DEFINITION


SEVERITY OF IMPACT


INSPECTION REQUIREMENT AS355


INSPECTION REQUIREMENT – AS355


TRANSMISSION OVERTORQUE

CASE STUDY ON

AS355


SUDDEN MAIN ROTOR STOPPAGEIN GENERAL, THE INSPECTION REQUIREMENT FOR SUDDEN MAIN ROTOR STOPPAGE IS SIMILAR TO THE INSPECTION AFTER MAIN ROTOR STRIKES.SUDDEN MAIN ROTOR STOPPAGE IS USUALLY DUE TO ABRUPT APPLICATION OF MAIN ROTOR BRAKE. (APPLICATION OF ROTOR BRAKE AT HIGH RPM)

inspection requirements for helicopter after incidents 1

Engineering