Figure 4-12.—Water-brake pressure gauges and switches.
adjacent to the tank. The switches are electrically tied
in with the console to prevent operation in case the
pressure falls below normal. Water pressure keeps the
switch contacts closed, thus completing a circuit.
Should the pressure fall below normal, either one or
both of the switches will drop open, breaking the
circuit. There are also two pressure gauges in the lines
to give a visual indication of the pressure, commonly
referred to as “elbow pressure.”
VELOCITY INDICATOR
INSTALLATION
A velocity indicator is used to determine the
endspeed of the shuttle and attached aircraft, or
deadload. Endspeed records provide one of the means
by which catapult operation can be checked. The
velocity indicator installations consist of either a
chronograph installation (fig. 4-13) or a digital
endspeed indicator installation (fig. 4-14).
The chronograph consists of a 230-volt direct-
current power supply, three switches fastened to each
side of the shuttle track, a brush mounted to each side
of the shuttle frame, and a transfer switch to select
speed-sensing from either side. Paper record strips for
the chronograph are also provided to record the speed
of each launch. The paper strips are placed on the
inside of the chronograph drum with the unwaxed side
against the drum. When the catapult is fired, the shuttle
passes along the track, and the brush on the shuttle
contacts the switches on the side of the track. At the
instant the brush contacts the first switch, a spark jumps
from the top spark needle on the chronograph, through
the record strip, to the drum. The spark burns a small
hole in the strip. The drum revolves, and when the
second and third contacts are made, sparks jump from
the middle and bottom needles to bum two more holes
in the strip. After each launch, the drum motor is
stopped and the spark circuit is de-energized. The
record strip is removed from the drum and laid on a flat
surface. An appropriate scale, which is supplied with
the chronograph, is then placed on the record strip, and
the endspeed, in knots, is read directly from the scale.
In reading the endspeed, position the scale so as to read
from the first (top) mark to the second (middle) mark,
then position it to read from the second (middle) mark
to the third (bottom) mark. The average of these two
endspeeds is recorded in the shot log or the appropriate
record.
The digital endspeed indicator (DESI) is located
near the central charging panel, and a remote endspeed
indicator is located at the catapult officer’s control
console. The DESI displays the time of day, shot count,
CSV setting, and shuttle endspeed. For more detailed
4-12
