TB 1--1520--248--20--58
4. Summary of Problem.
a. There are two issues in the fuselage/tailboom interface area addressed in this technical bulletin --
(1) A recent quality audit of the OH--58D tailboom assembly at Bell Helicopter has revealed that the requirement to
identify a part as flight safety was inadvertently omitted on some dash numbers for the assembly of tailboom longeron and
intercostal fittings. Consequently, "critical characteristics" were not annotated on the manufacturing planning documents.
As a result of that omission, critical characteristics requiring deburring during the manufacturing process were not verified.
Deburring of drilled holes is standard practice for assembly in this area. However, the possibility exists that sixteen (eight
each side) specific rivet holes on the lower left interface between the longeron fitting and intercostal may not have been
deburred. Failure to deburr can cause cracks to develop in the longeron fitting attached to the intercostal.
(2) Reports from the field and Bell Helicopter have indicated incidents of cracking in the aft fuselage frame assembly
where the tailboom attaches. The cracks primarily appear near the outboard bend radius of the frame forward side in the
upper right area (1 to 2 o'clock position looking forward).
b. Manpower/downtime and funding impacts -- See paragraph 12.
c. The purpose of this technical bulletin is to --
(1) Perform initial and recurring inspection of the tailboom intercostal assembly for cracks.
(2) Perform initial and recurring inspection of the aft fuselage frame assembly for cracks.
(3) Change frequency interval of progressive phase maintenance (PPM) inspection number 4.1 and emphasize inspec-
tion of the lower left tailboom attachment fitting and aft fuselage frame for cracks.
5. End Items to be Inspected -- All OH--58D aircraft.
NOMENCLATURE
PART NUMBER
NSN
Tailboom, Assembly
206--032--004--177
1560--01--419--7889
Tailboom, Assembly
206--032--004--171
1560--01--383--0102
Tailboom, Assembly
206--032--004--157
1560--01--341--6074
Tailboom, Assembly
406--961--024--151
N/A
Tailboom, Assembly
406--961--024--149
N/A
Tailboom, Assembly
406--961--024--111
N/A
7. Parts to be Inspected
NOMENCLATURE
PART NUMBER
NSN
Fitting, Tailboom
206--031--403--5
N/A
Frame, Aft Fuselage
206--032--308--103
N/A
8. Inspection Procedures
a. Loosen screws on countermeasures set AN/ALQ--144 IR jammer mount, if installed (Reference Task 2--3--4, TM
1--1520--248--23--1).
b. Remove 27 screws from tailboom access panel (P/N 206--032--328--115, Item 4, Figure 28, TM 1--1520--248--23P).
c. Remove tailboom access panel.
d. Inspection of Tailboom Fitting --
(1) Using a mirror and flashlight, visually inspect the lower left tailboom attachment area. Emphasis is on the sixteen
rivets (eight each side) that attach the intercostals (P/N 206--032--410--17/--19, Items 17 and 18, Figure 43, TM
1--1520--248--23P) to fitting (P/N 206--031--403--5, Item 22, Figure 43, TM 1--1520--248--23P).
(2) Check for cracks propagating from under the rivets.
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