TM 55-4920-390-13&P
SECTION I
INTRODUCTION AND DESCRIPTION
1-1. INTRODUCTION. This handbook contains operating and service instructions and appropriate parts lists and
illustrations for the Strobex Blade Tracker, Model 135M-9.
1-2. PURPOSE AND USE. The Strobex Blade Tracker, Model 135M-9 (Figure 1-1), is a
bright, collimated, stroboscopic
light source whose flash rate is controlled by an internal oscillator locked to a one-per-rev rotor signal. It is used for
observing the "track" and "lead-lag" of helicopter blades both during ground run-up and in flight. "Track" refers to the
relative path (vertical) of the helicopter blade tips as they pass any given point in azimuth, and "Lead-lag" refers to errors
in uniform azimuth relations of the blades. Faulty track or lead-lag induces low frequency vibrations in the air frame of
the helicopter which adversely affect service and life and constitute a hazard and inconvenience to crew and passengers.
1-3. DISPLAY OBSERVED. When directed so as to illuminate the rotating blade tips, the properly synchronized
Strobex displays the previously attached, retro-reflective tip targets so as to present a grouped display of all targets in the
sky. This "stopped" display enables the operator to observe the relative positions of the targets (blades) and thus
determine track and lead-lag.
1-4. DESCRIPTION OF EQUIPMENT. (See Figure 1-1) The M-9 Strobex consists of a
hinged, sealable case with an
electronics compartment, the hand-held lamp on a flexible 9' cable, with its pistol grip handle and oscillator controls, and
two 40' cables one for each 28 VDC and signal input. All cables are secured to the instrument (without connectors) so
they cannot be inadvertently lost, and provision is made within the case for storage. When the case is closed (as in
Figure 1-1 a), the unit is
sealed and entirely self-contained.
TABLE 1-1. EQUIPMENT SUPPLIED
Quantity
Item Description
C-H Part No.
NAT. Stock No.
10 sets
Tip Target Numbers (1 thru 6)
B2764-16
1 each
Spare Flash Tube
35 S
6240-019-5835
2 each
Spare fuses
5 amp 32V slo blo
1 each
Rubber Hand Roller
A 2787
1-1