Inspection requirements for helicopter after incidents 1

FOR TRAINING PURPOSE ONLY
Malaysian Institute of Aviation Technology
AJD21603 ROTORCRAFT SERVICING,
MAINTENANCE AND ROLE EQUIPMENT
WEEK 10
INSPECTION REQUIREMENT FOR HELICOPTER AFTER
INCIDENTS

LESSON OBJECTIVE & OUTCOME
OBJECTIVE:
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.

INTRODUCTION
IN 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 STEPS
The 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 LANDING
An 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 GEAR
Examine 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.

Examine 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.

Examine 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 AREA
Check 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 AREA
Examine 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

ENGINE
Check 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

ENGINE
Examine 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 RUNS
Provided 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 BLADES
Remove 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 HEAD
Disconnect 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 ROTOR
Examine 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 GEAR
With 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 STRIKES
IMPACT DEFINITION

SEVERITY OF IMPACT

INSPECTION REQUIREMENT AS355

INSPECTION REQUIREMENT – AS355

TRANSMISSION OVERTORQUE
CASE STUDY
ON
AS355

SUDDEN MAIN ROTOR STOPPAGE
IN 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

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