COMBINING TRANSMISSION OUTSIDE SURFACE (ET).
3.16.1 Description (Figure 3-1. Index No. 16). The combining transmission receives input torque from the two engine
transmissions through the engine driveshafts. It combines the torque and transmits it to the forward and aft driveshafting
through output shafts.
3.16.2 Defects. Defects may occur anywhere on the surface of the combining transmission outside surface. Any
damaged area shall be inspected both before and after rework. No cracks are allowed.
3.16.3 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 combining transmission shall be removed in accordance with the
Access. Access is through the combiner transmission door. See Figure 1-4 - CH-47: 23; MH-47: 30.
Preparation of Part. The area to be inspected shall be thoroughly cleaned. Refer to Preparation of Part or
NDI Equipment Settings.
Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19elI.
- 200 KHz