unit along steel pipe G, be compressed complete- 
ly. Spring F was compressed by hydraulically 
loading a long, thin, slotted steel rod which 
fitted over support rod H in the locking unit 
and passed up through the center fluid pressure 
equalizing tube through the tail. When spring 
F was completely depressed, toggle D was closed 
manually through one of the door ports. "Load- 
ing" the tail was done in the launching frame 
with the missile in the launch attitude. 
In Fig. 12, the drag fins are open and one 
is removed. Toggle clamp D, the key element in 
the tail-locking assembly, was released when the 
explosion motor, mounted as shown, received a 
d-c electrical impulse from a pressure switch, 
On release of toggle D the spring quickly ex- 
panded, pushing up the locking unit which re- 
leased the four toggle clamps and imparting an 
initial thrust to the tail section. 
The locking unit also controlled the doors 
or drag fins. At the time of "loading" three of 
the doors which were secured to their mounts 
were locked into place. The fourth was fixed 
in place after loading and locking toggle D. 
The doors were closed by push rods K, forced 
outward by the inclined surface I, acting against 
their inside upper edge. Each door was fast- 
ened by two bolts to a mount M which revolved 
vertically around a pin. The force exerted on 
the door by the push rods above the revolving 
mounts kept the bottom of the doors locked flush 
with the surface of the missile by simple lever 
action. The push rods were forced outward by 
incline I as the spring and locking unit were 
forced down under load. In the locked position 
the push rods were pressed between the straight 
area J and their contact points at the tops of 
their respective doors. Upon release of the 
spring F, push-rod force was released from the 
doors, or fins, and they were snapped open by 
the action of spring N (Fig. 12) against their 
bottom inside edge. The fin opening angle was 
restricted (Fig. 12). The position of the 
closed doors was kept to close tolerance and 
was critical because of the outside surface had 
to be flush, and the doors tightly held. Any 
door rattle or protrusion of the door edges 
above the missile surface during fall would dis- 
tort the hydrodynamic-flow-noise data. 
Recovery Circuitry 
The recovery circuitry served two func- 
tions: 
(a) It applied a 6-volt signal across the 
17 
explosion motor when the missile reached a pre- 
determined depth, thus initiating the tail- 
releasing sequence, 
(b) It shut off the recorder at another 
predetermined depth to keep the recorder from 
loading the nickel-cadmium battery during the 
time of missile recovery. 
Figure 15 is a complete schematic of the 
recovery circuitry. The main controlling circuit 
element was a Meletron Model 4141 pressure switch. 
Switch No. 1 of the pressure switch was set at 
35 psi or 80 ft. When the missile reached a 
depth of 80 ft, the normally open contact closed 
and the explosion motor was set off. Water pres- 
sure reached the switch through a hydraulic hose 
from the water-filled afterend of the cylindrical 
midsection of the missile, which acted as an 
accumulator. 
A few seconds prior to each drop of the mis- 
sile, the recorder was turned on by the external 
switch (Fig, 13). This energized the normally 
open relay, and closed and mechanically latched 
it. Through this switch, 12 volts was fed to 
recorder. When the missile reached 100 ft the 
normally open contact of Switch No, 2 closed, 
shutting off the recorder. A second coil was 
used to keep the recorder off during the re- 
covery of the missile as it was returned to lower 
pressure. Coil B is energized long enough to 
throw the normally closed contacts open and latch 
the relay mechanically in the open position. 
This terminated the 12-volt recorder supply. 
cutting off the current to the coil, the drain 
of current from the 12-volt battery was stopped. 
The 25-y f condenser prolonged the current pulse 
through self-cutting coil B. 
By 
Checkout and Calibration Procedures 
A calibration and circuit test unit (Fig. 
14) was designed and built for use in the field. 
This unit included a W meter, the AP23 play- 
back amplifier, a pressure-transducer simulator 
consisting of a potentiometer with precision re- 
sistor steps, two inputs to the recorder ampli- 
fiers bypassing the hydrophone inputs, control 
switches, and a 27-pin Jones plug connector, 
During the checkout the Jones plug from the 
checkout unit was inserted into the missile elec- 
tronic system in place of a similar Jones-plug 
dummy connector through which the circuits were 
connected during normal operation. 
The calibration-test unit provided means to 
determine: 
