caps are temporarily attached to the tip of each blade. The  high-intensity strobe light flashes in time with the rotating  blades. The strobe light operates from the aircraft electrical  power supply. By observing the reflected tip cap image, it  is possible to view the track of the rotating blades. Tracking  is accomplished in a sequence of four separate steps: ground  tracking, hover verification, forward flight tracking, and  autorotation rpm adjustment. The marking and electronic methods of tail rotor tracking  are explained in the following paragraphs. maintenance manual. Run engine with pedals in neutral  position. Reset marking device on underside of tail boom  assembly. Slowly move marking device into disk of tail rotor  approximately one inch from tip. When near blade is marked,  stop engine and allow rotor to stop. Repeat this procedure  until tracking mark crosses over to the other blade, then  extend pitch control link of unmarked blade one half turn.  The electronic Vibrex balancing and tracking kit is housed in  a carrying case and consists of a Model 177M-6A Balancer,  a Model 135M-11 Strobex, track and balance charts, an  accelerometer, cables, and attaching brackets.  The Vibrex balancing kit is used to measure and indicate the  level of vibration induced by the main rotor and tail rotor of  a helicopter. The Vibrex analyzes the vibration induced by  out-of-track or out-of-balance rotors, and then by plotting  vibration amplitude and clock angle on a chart the amount  and location of rotor track or weight change is determined. In  addition, the Vibrex is used in troubleshooting by measuring  the vibration levels and frequencies or rpm of unknown  disturbances. Procedures for tail rotor tracking using the marking method,  as shown in  Figure 2-55 , are as follows: NOTE: Ground run-up shall be performed by authorized  personnel only. Start engine in accordance with applicable  •  After replacement or installation of tail rotor hub,  blades, or pitch change system, check tail rotor rigging  and track tail rotor blades. Tail rotor tip clearance shall  be set before tracking and checked again after tracking. •  The strobe-type tracking device may be used if  available. Instructions for use are provided with the  device. Attach a piece of soft rubber hose six inches  long on the end of a ½  ×  ½ inch pine stick or other  flexible device. Cover the rubber hose with Prussian  blue or similar type of coloring thinned with oil.  Electronic Method Marking Method Tail Rotor Tracking Figure 2-55. Tail rotor tracking. Figure 2-54.  Vibrex tracker. TESTER Interrupter plate Motor 2-33