AACs - Part 1-59 - Airworthiness Articles
Part 1 - Airworthiness Articles
Pacific Scientific Reel-O-Matic Inertia Reel
An accident involving a Hughes 269 helicopter highlighted a potential problem with the installation of the inertia reel for the crew harness. Fortunately, in this accident, the crash loads were not high. However, each harness was severed by the sharp edge of its inertia reel slot! The webbing was torn much like a sheet of paper across a cutting edge!
The Pacific Scientific "Reel-O-Matic" inertia reel is used in many aircraft. The design allows for the installation of the reel in either direction, ie so that the rewind of the reel is either clockwise or anti-clockwise.
However, if the reel is installed such that the webbing bends across the slot in the cylinder of the inertial reel, there is a potential problem (Figure 1 illustrates). The webbing can wear the edge of the slot in the cylinder until the lip becomes a knife-edge. Then as happened in the accident, the knife-edge can shear through the webbing when subjected to sudden load.
Airworthiness Directive AD/HU269/77, which referred to Schweizer Service Information Notice N-194, was raised in 1985 to address this problem. However, this inertia reel is also used in many other aircraft.
It is strongly recommended that each aircraft be checked to determine if such reels are fitted,and if so, check that the webbing does not rub on the lip as in figure 1.
Note: The plastic shield on the cylinder must be removed to ensure a proper check. If necessary reposition as illustrated in figure 2 and 3.
The slot should be positioned such that the webbing remains clear throughout the range of travel. The slot can be indexed by rotating the cylinder in 60 degree increments in relation to the mounting feet.
Note: PLASTIC COVER REMOVED