LOWER DRAG LINK (ET).
4.21.1 Description (Figure 4-1 . Index No. 21). The lower drag links support the aft landing gear swivel housings and
are connected to fuselage fittings.
4.21.2 Defects. Defects may occur anywhere on the surface of the lower link. No cracks are allowed.
4.21.3 Primary Method. Eddy Current.
Eddy Current Inspection Unit
Probe, straight, shielded surface, 100 KHz-500 KHz
Probe, right angle, shielded surface, 100 KHz-500 KHz, 901/2 inch drop
Reference Block, three-notched aluminum (0.008, 0.020, and 0.040 EDM notches)
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 lower drag link shall be removed in accordance with
the applicable technical manuals listed in Table 1-1.
Access. Not applicable.
Preparation of Part. The lower drag link shall be thoroughly cleaned. Refer to, Preparation
NDI Equipment Settings.
Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19e .
- 200 KHz
Probe drive - mid
Null probe on test block.
Adjust phase as required to obtain horizontal lift-off.
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. (Refer to standard instrument