TM 1-1520-265-23
5-22
Change 4
5.13 HIRSS AND NACELLE FAIRING SUPPORT MOUNTS (PT).
5.13.1 Description (Figure 5-1, Index No. 13). The hover infrared suppression system is contained
within the HIRSS module. Parts of the support mounts are: fail-safe plate, rear suppressor support
fitting and link, lower nacelle support fitting and link, and upper nacelle support fitting and link.
5.13.2 Defects. Defects can occur anywhere on the surface of the described parts. No cracks are
allowed.
5.13.3 Primary Method. Eddy Current.
5.13.3.1 NDI Equipment and Materials. (Refer to Appendix B.)
a. Eddy Current Inspection Unit
b. Probe, straight, shielded surface, 100 KHz-500 KHz
c. Probe, right angle, shielded surface, 100 KHz-500 KHz, 90_ 1/2 inch drop
d. Cable Assembly
e. Reference Block, three-notched aluminum (0.008, 0.020, 0.040 EDM notches)
f. Teflon Tape, refer to Table 1-8
g. Aircraft Marking Pencil, refer to Table 1-8
5.13.3.2 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance
in accordance with the applicable technical manuals listed in Table 1-1.
5.13.3.3 Access. Not applicable.
5.13.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or
Area for NDI, paragraph 1.4.4.
5.13.3.5 NDI Equipment Settings.
a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19eII.
Frequency F1
- 200 KHz
F2
- off
HdB
- 57.0
VdB
- 69.0
Rot
- 56_ Adjust as needed
Probe drive
- mid
LPF
- 100
HPF
- 0
H Pos
- 80% Adjust as needed
V Pos
- 20% Adjust as needed
b. Refer to Eddy Current Method, paragraph 1.4.11. Set up on test block as follows:
(1) .Null probe on test block.
(2) .Adjust phase as required to obtain horizontal lift-off.
(3) .Move probe over all three notches in test block. Adjust gain to obtain a three block vertical
signal when probe is passed over 0.040-inch notch in test block. (See the standard
instrument display shown in Figure 1-7.)
