Backup Method. None required.
System Securing. The vertical stabilizer, if removed, requires installation in accordance with the applicable
technical manuals listed in Table 1-1.
4.20 VERTICAL STABILIZER BARREL NUTS (MT).
Description (Figure 4-1. Index No. 20)
. The vertical stabilizer barrel nuts are located beneath the vertical
stabilizer lugs and may only be seen when the vertical stabilizer is removed.
Defects. This inspection is used to verify crack indications found visually on the vertical stabilizer barrel nuts.
No cracks are allowed.
Primary Method. Magnetic Particle.
NDI Equipment and Materials. (Refer to Appendix B.)
Magnetic Particle Inspection Probe/Yoke
Fluorescent Magnetic Particles, refer to Table 1-8
Consumable Materials, refer to Table 1-8
Aircraft Marking Pencil, refer to Table 1-8
Hand-held magnetic coil may be used. Refer to paragraph 220.127.116.11.2 and Figure 1-6.
Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance and the vertical
stabilizer barrel nuts removed in accordance with the applicable technical manuals listed in Table 1-1.
Access. Not applicable.
Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
NDI Equipment Settings. Refer to Magnetic Particle Method, paragraph 1.4.8.
Inspection Procedure. A magnetic field shall be applied to the part perpendicular to the orientation of possible
cracks. The position required for this inspection is illustrated in Figure 4-20.
Select AC on the AC/DC power switch.
Place probe/yoke on part in position 1 as shown.
Press the test switch and apply a light coat of magnetic particle media at the same time. Remove the media
momentarily before removing the current. Current should be applied for no more than five seconds.
Inspect for cracks using the black light.