Operation - TM-9-1270-212-14-P0037

TM 9-1270-212-14&P

linkage steel fastener has been connected to the helmet.

b. Operation. For operation, connector A1P1 is

The lamps in the helmet sight are so wired that they can

connected to the helicopter helmet sight connector in the

be tested in series. The series test bypasses the action dis-

pilot's compartment or the gunner's compartment. Only

connect relays. The three lamps in the sight assembly are

the gunner's connector has wires to pins 7 and 8; therefore,

potted into a single replaceable lamp assembly with unit

the retract-solenoid feature is operative only in the gunner's

designator DS1.

compartment. The solenoid is mechanically operated by

pressing a button on the top of the sight housing; it is

f. Reed Switch. Reed switch S1 in the magnetic

electrically operated in the gunner's compartment as the

receptacle on top of the helmet sight senses the presence of

ACQ TRK STOW switch (refer to figure 2-5) is moved from

the steel fastener on the end of the linkage arm. The reed

ACQ to TRK. Actuating the solenoid allows a spring in the

sight housing to drive the eyepiece counterclockwise to the

switch is open when no fastener is connected and closes

when the fastener contacts the magnet. Proper magnet

horizontal position; the eyepiece must be manually

returned to the vertical position. The spring-loaded solenoid

position in the housing is important for correct operation

engages a detent to hold the eyepiece in its previously set

of the reed switch. White dots on the housing and magnet

position.

must be aligned for the reed switch to sense the presence of

the steel fastener.

c. Eyepiece Adjustment. The eyepiece can be moved up

NOTE

and down by compressing the spring on the straight shaft,

and the whole sight assembly can be adjusted laterally by

White dots on the housing and magnet may

manually rotating the sight housing. Vertical security is

have to be slightly offset for reed switch to

controlled automatically as the spring contacts the shaft.

sense the presence of the steel fastener.

Lateral security is controlled by the tightness of the screw

inside the helmet that secures the sight housing to the

helmet.

g. Reticle Lamp Test. The reticle lamps in each helmet

sight are tested by actuating the reticle-lamp test switch on

d. Boresighting. The helmet sight transfers the plane A

the related armament control panel. Actuating this switch

line of sight provided by the reticle in the eyepiece to the

on the pilot or gunner armament control panel energizes a

plane B surface of the four-section magnet in the

relay in the IFCU; this disconnects the ac power and ac

receptacle. Therefore, the vertical and lateral position of

returns from the related helmet sight and applies 15-volt dc

the eyepiece has negligible effect on helmet sight alignment.

power between pins 1 and 4 of the helmet-sight connector.

The alignment o f these two reference planes is

The series-connected dc power checks for a burned-out

accomplished by adjusting three sockethead setscrews to

lamp (which may not otherwise be detected). Thus, if the

move the magnet in its receptacle. For helmet boresighting,

reticle disappears when the reticle-lamp test switch is

the plane of the magnet is established by the use of the

actuated, one or more of the lamps in the sight is

helmet boresight tool (fig. 2-16), and the two lines of sight

inoperative and the lamp assembly must be replaced. The

are then brought into coincidence by adjusting these

15-volt dc power for the pilot lamp test is supplied from

sockethead screws. Two operators are required for this

dropping resistor R7 on TB1 in the EIA through J1-HH to

adjustment, one to sight through the reticle while the other

the IFCU; 15-volt dc power for the gunner lamp test is

sights through the helmet boresight tool and adjusts the

supplied from dropping resistor R8 on TB1 through J1-GG.

setscrews as required.

e. Power. During normal operation, 0- to 5-volt ac

1-21. Linkage and EIA Theory.

power is provided on pins 1 and 3 of A1P1 from the IFCU

a. General.

through the mating helicopter connector (17P1 or 17P2).

Returns are connected to pins A1P1-2 and -4. This arrange-

ment connects the three lamps in the lamp assembly in

(1) The pilot and gunner linkages operate with part

parallel. However, thc return circuit is provided through

of the EIA circuitry to provide error signals that drive the

the helicopter pilot and gunner action disconnect relays,

TSU or turret servo system into coincidence with the HSS

K83 and K84, when they are energized. These relays are

linkage position. (The remaining EIA circuitry provides the

energized when the reed switch in the helmet sight is closed

BIT capability and is discussed in paragraph 1-22.) The

and deenergized when the reed switch is open. The return

linkages operate with independent but highly similar EIA

circuit for the lamps is complete only when the linkage

circuitry and, thus, for example, the gunner is able to direct

steel fastener (or helmet boresight tool) is connected to the

the TSU with his helmet sight while the pilot directs the

magnetic receptacle. Thus, a reticle is visible only after a

gun turret with his helmet sight.

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