ENSTROM F-28F/280F SERIES MAINTENANCE MANUAL
Rev.
8
MM-4-63
Sep
20/17
(2) Inspect the forward and aft crosstube attachment clamps for damage and
cracks. Inspect all fittings and bolt holes for elongation. See SDB 0124 for
additional inspection criteria.
(3) Inspect the landing gear leg assemblies for distortion or deformation. Inspect all
fittings and bolt holes for elongation. Inspect all welds and gussets for cracks.
(4) Inspect the skid tubes for damage and straightness. Inspect all hardware
attachment holes for elongation or tears.
(5) Inspect the oleos for damage, freedom of movement, and leakage.
(6) Inspect the tailcone to pylon, main rotor transmission to pylon, engine to pylon,
crosstube to pylon, and cabin to pylon attachment points for deformation or
hardware failures.
(7) Inspect the keel structure edges, beams, lightening holes, and intercostals for
buckling or deformation. Closely inspect the keel structures for interference or
contact with flight control mechanisms.
(8) Check the main rotor shaft run out. Maximum allowed is 0.012 inch/0.305 mm
FIM.
(9) Check the main rotor transmission mount bolt torque. If torque is lost, replace
the hardware or remove and magnetic particle inspect the hardware.
(10) Inspect the main rotor transmission mount lugs with liquid penetrant method.
(11) Refer to the latest revision of Textron-Lycoming Service Bulletin 533B for the
recommended engine inspection.
4-61. Main Rotor Overspeed – Special Instruction
A. Overspeeds from 385-405 rpm for 5 seconds or less. No inspection required.
NOTE
If any damage is found, remove the main rotor hub and return to Enstrom
Helicopter Corporation for inspection and overhaul/replacement.
B. Overspeeds from 385-405 rpm for more than 5 seconds or overspeeds from 406-420
rpm. Perform the following:
(1) Remove the main rotor blades and inspect flapping axis for proper drag,
notchiness, and freedom of movement.
(2) Inspect the main rotor blade retention for any deformation.
(3) Inspect the lamiflex bearings for deformation, proper thickness, delamination or
extruded brass. Inspect the nylatron strap for any damage or unusual wear.
(4) Inspect the main rotor spindles for pulled or distorted threads.
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