TB 1--1520--238--20--95
2.
Task/Inspection Suspense Date. Within next 20 flight hours/30 days.
3.
Reporting Compliance Suspense Date. N/A.
4.
Summary of the Problem.
a. During a recent 250 hour phase maintenance inspection, a main rotor retention nut was found to
be cracked. The failure of this nut was attributed to stress corrosion cracking. The basic and --3 configuration
main rotor retention nuts are of a harder material than the --5 and are more susceptible to this type of failure.
b. For manpower/downtime and funding impacts, see paragraph 12.
c.
The purpose of this TB is to direct initial and recurring inspection of AH--64 main rotor retention nuts.
5.
End Items to be inspected. All AH--64 aircraft.
6.
Assembly Components to be Inspected. N/A.
7.
Parts to be Inspected.
PART NUMBER
NATIONAL STOCK NUMBER
NOMENCLATURE
Main Rotor Retention Nut
7--311411102
5310--01--160--6767
Main Rotor Retention Nut
7--311411102--3
5310--01--160--6767
Main Rotor Retention Nut
7--311411102--5
5310--01--350--1346
8.
Inspection Procedures.
a. On or before the next 20 flight hours/30 days, review the DA Form 2408--16 entry to determine the
configuration of the main rotor retention nut installed.
b. If P/N 7--311411102--5 is installed, this inspection is complete. Continue with current 250 hour phase
magnetic particle inspections. Physically verify part number on removal. If you cannot positively identify the
part number, measure outer diameter (OD) of the nut. If the OD measurement is 8.120 inches, it is a --3 or
basic configuration nut. If the OD measurement is 8.350 inches, it is a --5 nut.
c.
If P/N 7--311411102 or 7--311411102--3 main rotor retention nut is installed, do the following:
(1) Review the DA Form 2408--15 entries to determine completion date of last phase inspection.
(a) If completion date of last phase inspection is within the last six (6) months, schedule a
magnetic particle inspection of the main rotor nut----to be complied with no later than the end of the 6
month period that the last phase inspection was accomplished or next phase inspection, whichever
comes first.
(b) If the last phase inspection was not accomplished within the last 6 months, perform a
magnetic particle inspection of the main rotor retention nut prior to the task inspection suspense date of
this message. Physically verify part number on removal.
(c) If part number cannot be positively identified, measure outer diameter (OD) of nut. If the
OD measurement is 8.120 inches, it is a --3 or basic configuration nut. If the OD measurement is 8.350
inches, it is a --5 configuration nut.
(2) Perform a magnetic particle inspection every 6 months or 250 hour phase maintenance in-
spection, whichever comes first.
(3) Annotate the DA Form 2408--18 with the following recurring inspection requirement, "Main
Rotor Retention Nut P/N 7--311411102/7--311411102--3 Magnetic Particle Inspection" for every 6 months or
250 hour phase. ULLS--A units will use their 800 inspection numbers for these inspections. Exceptions to
this timeline are authorized in accordance with TM 1--1500--328--23 DTD 28 February 1995 paragraph 2--10,
scheduling of recurring special inspections, page 2--8.
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