TB 1--1520--240--20--141
c. Aircraft in Transit --
NOTE
For aircraft away from home station, this Technical Bulletin authorizes a
one time flight, with intermediate stops, to return to the nearest secured
maintenance facility/home station.
(1) Surface/Air Shipment -- Same as paragraph 1a.
(2) Ferry Status -- Same as paragraph 1a.
d. Maintenance Trainers (Category A and B) -- Comply no later than 25 January 2004.
e. Components/Parts in Stock at All Levels (Depot and Others) including War Reserves -- Upon receipt
of this Technical Bulletin, Depot and Materiel Activity Commanders will ensure the materiel condition tags of
all items in all condition codes listed in paragraphs 6 and 7 are annotated to read: "CH-47-02-03 (TB
1-1520-240-20-141), inspection of the tie bar assemblies and rotor tachometers not complied with."
(1) Wholesale Stock -- N/A.
(2) Retail Stock -- Upon receipt of this message, Commanders and Facility Managers maintain-
ing retail stock at installation level and below shall contact the supported aviation unit to perform the proce-
dures required in accordance with paragraphs 8 and 9 on suspect materiel. Dispose of discrepant materiel
in accordance with paragraph 10. Report compliance with this Technical Bulletin in accordance with para-
graph 14c (2) no later than 8 February 2002.
f. Components/Parts in Work (Depot Level and Others) --Depot and other Maintenance Activity Com-
manders will ensure items in paragraphs 6 and 7 are not issued until they are in compliance with this Technical
Bulletin.
Task/Inspection Suspense Date.
a. Complete the inspection in accordance with paragraph 8a prior to the next flight.
b. Complete the inspection in accordance with paragraph 8b at the next rotor head removal, but no later
than the next phase inspection or 25 January 2004, whichever occurs first.
c. Complete the inspection for all H-47D/F aircraft in accordance with paragraph 8c no later than 25
February 2002.
4.
Summary of the Problem.
a. History -- CH--47--02--02 was issued on 24 Janaury 2002 requiring inspection of the tie bar assembly
and rotor tachometer. This message superceded the requirements in CH--47--02--02. Changes have been
made to paragraph 1c, 8a, 8b, 9a and 10d.
(1) Tie Bar Plate Failure -- Reports from the field on tie bar assemblies indicate that tie bar plate
cracks have occurred much earlier than the retirement life of 8693 hours. Even though the tie bar assembly
is currently inspected at 1200 hours and at the 2400 hour overhaul, it is possible that some fielded tie bars
may have tie bar plates which have cracked.
(2) Tie Bar Over Speed Damage -- Testing has shown that initial deformation of the rotary wing
head tie bar assembly may occur at a point just above 111 percent rotor RPM. Currently, the 145ES008 rotor
tachometers (all H-47D/F) and multi function displays (MFD) (MH-47E) indicate 115 percent RPM as the max-
imum transient rotor speed limit. Because of this, some tie bar assemblies may have already been damaged
due to exceeding 111 percent RPM.
b. Manpower/Downtime and Funding impacts -- see paragraph 12.
c. The purpose of this Technical Bulletin is to --
(1) Tie Bar Assembly --
2
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