TM 1-1520-253-23
COMBINING TRANSMISSION SUPPORT FITTINGS AND LONGITUDINAL BEAMS (ET).
4.12.1 Description (Figure 4-1, Index No. 12). The combining transmission has four support fittings which are bolted to
the longitudinal support beams of the fuselage ceiling. This inspection is applicable to both the interior and exterior.
4.12.2 Defects. Cracks may occur anywhere on the fitting or beams. No cracks are allowed.
4.12.3 Primary Method. Eddy Current.
a.
Eddy Current Inspection Unit
b.
Probe, straight, shielded surface, 100 KHz-500 KHz
c.
Probe, right angle, shielded surface, 100 KHz-500 KHz, 901/2 inch drop
d.
Cable Assembly
e.
Reference Block, three-notched aluminum (0.008, 0.020, and 0.040 EDM notches)
f.
Teflon Tape, refer to Table 1-8
g.
Aircraft Marking Pencil, refer to Table 1-8
4.12.3.2
Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. Partial
inspection for cause (visual indications, sites of mechanical damage, corrosion, etc.) may be performed on all exposed
surfaces of the installed part using this procedure. If required, the components shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
4.12.3.3
Access. Access is through pylon combiner transmission hinged fairing, doors, or the fuselage ceiling. See
WARNING.
Maintenance Platforms/Workstands
Use only appropriate platforms, workstands, or other approved locally procured stands
and restraint equipment when working above 10 feet on helicopter in a nontactical
environment. Otherwise, personnel injury could result from accidental falls.
4.12.3.4
Preparation of Part. The combining transmission support fittings and longitudinal beams shall be
thoroughly cleaned. Refer to Preparation of Part or Area for NDI, paragraph 1.4.4.
