TB 1-1520-237-20-181
(3) Final NDI inspection for cracks. I cracks are found the hub assembly will be removed from service and
scrapped. The unit will assist in removing the blade, damper and spindle and will follow TM procedures during
installation (including a main rotor blade track and balance). After completion of the inspection, the NDI requirements of
c. If edge break rework is required and a contractor team is not immediately available and the hub is required for
service, a reoccurring NDI inspection can be implemented to allow use of the hub assembly. The inspection procedures
are described in paragraph 9.d.(2). The NDI inspection is required immediately and then every 125 flight hours. If a
crack is detected, the hub will be removed from service and scrapped. If necessary, contact the logistical POC to
arrange for a rework team.
d. A NDI inspection for cracks is required on all hub assemblies. The inspection area is where the 11 O'Clock
damper bracket hole pierces the internal hub wall. Note, the 11 O'Clock hole does not cleanly exit through the internal
hub wall. Removal of the blade and spindle is required and shall be performed IAW reference 13.a. and 13.b.
(1) The following criteria shall be used to determine how many NDI inspections are required.
(a) If the hub had the edge break rework performed, a repetitive NDI inspection is required at the next
and subsequent 500 hour phase inspection until the hub has a final NDI inspection at over 1000 flight hours since rework.
Annotate the DA Form 2408-5-1 for the main rotor hub assembly.
(b) If the hub had no rework required from the edge break inspection and has over 1000 flight hours, a
repetitive NDI inspection is required at the next 500 hour phase inspection. Annotate the DA Form 2408-5-1 for the main
rotor hub assembly.
(c) If the hub had no rework required from the edge break inspection and has under 1000 flight hours, a
repetitive NDI inspection is required at the next and subsequent 500 hour phase inspection until the hub has final NDI
inspection at over 1000 flight hours. Annotate the DA Form 2408-5-1 for the main rotor hub assembly.
(2) Perform fluorescent penetrant inspection of hub as follows: (a) Remove main rotor blade(s) and spindle(s)
IAW reference 13.a. and 13.b.
(b) Remove paint, primer, and other surface contaminates from inside hub arms in the area of the 11
O'Clock damper bracket mounting hole.
(c) Mask off areas adjacent to area being inspected with pressure sensitive tape, fed. spec.
PP-T-60, or equivalent.
(d) Place rags under area(s) to be inspected to catch any chemicals during surface coating removal.
(e) Apply epoxy paint remover, MIL-R-81294, Type 1, Class 1, or equivalent, to area to be stripped,
using a small paint brush.
(f) After surface coating bubbles, remove coating using a nonmetallic scraper.
(g) Remove all remains of stripper using a rag saturated with water. Repeat as necessary to thoroughly
clean area.
(h) Perform fluorescent penetrant inspection per MIL-STD-6866 and TM 55-1500-335-23, NDI inspection
method. Use penetrant material type I, method B, C, or D, sensitivity level 3 or 4 and solvent remover and non-aqueous
developer shall be the non-halogenic type.
(i) Inspect inside of hub arms around each 11 O'Clock hole. Pay particular attention to presence of any
cracks which originate out of the 11 O'Clock damper bracket attachment holes. There will be some continuing level of
penetrate bleedout from inserts which may require wiping.
(j) If any cracks are found, replace hub.
(k) Clean part to remove penetrant inspection material.
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