Figure 1-9. Typical HSS operating signals

TM 9-1270-212-14&P

resolver body. When the worm-gear locking screw is

released, the worm gear can be rotated to cause the resolver

body to turn within the linkage to obtain adjustment of the

resolver elevation output. The worm wheel provides for a

minimum of 20 degrees of body travel. In each linkage,

the shaft of B1 is factory-set to take into account the

depression angle at which the linkage is mounted in the

AH-1S(Mod) helicopter, so adjustment of this resolver

at installation will normally be minimal in this helicopter

. In

and fairly great in the AH-1S helicopter

the AH-1S(Mod) helicopter, the pilot linkage is depressed

4 degrees and the gunner linkage is depressed 8 degrees; in

the AH-1S helicopter, the pilot linkage is at 0 degrees and

the gunner linkage is depressed 11-1/2 degrees. Final

adjustment of these B1 resolvers is made during bore-

sighting.

(9) The elevation and azimuth fine-adjustment

potentiometers on the EIA allow exact coincidence to be

obtained between the helmet line of sight and the turret

line of sight. Refer to foldout FO-4 or FO-5, sheet 1, and

observe that these potentiometers (Rl, R2, R3, and R4) are

connected to 0.5-volt reference signals, with the pin-3

Figure 1-9. Typical HSS operating signals

clockwise end to the in-phase signal and the pin-1

counterclockwise end to the out-of-phase signal. A voltage

(7) The phase of the B4-R2 output signal at J3-42

null occurs at the center of each potentiometer. The R3

remains constant, although the amplitude may vary from a

outputs of resolvers B3 and B4 at J3-43 and J3-46 are

null at 90 degrees left to maximum amplitude straight

connected to the non-inverting pins of amplifiers AR1,

ahead and to a null at 90 degrees right. If the 90-degree

AR2, and AR5, AR6 (see foldout FO-1), and thus no phase

positions are exceeded, the phase on either side is inverted.

shift occurs through these amplifiers. The signals at TP6,

NOTE

TP7, and TP15, TP13 on A13 are in phase. The

potentiometer wipers, however, are connected to the

inverting inputs of these amplifiers (see foldout FO-10),

A mechanical alignment of the rails in azimuth,

and thus the fine-adjust potentiometer outputs are inverted

roll, and pitch must be made at installation and

through amplifiers AR1 and AR5.

at major overhaul. The alignments of the rails in

azimuth and roll are accomplished by means of

1-22. Linkage and EIA BIT Theory.

the adjustable rail supports. This alignment of

the rails in the helicopter also aligns azimuth

a. General. When the HSS BIT switch on the gunner

resolvers B2 and B3 to the armament

armament control panel in the helicopter is momentarily

coordinate reference axes. Alignment in pitch

actuated, the HSS automatically initiates an EIA and

of elevation resolvers B1 and B4 to the

linkage self-test. If both linkages have been placed in their

armament coordinate reference axes is

BIT brackets, the special BIT circuitry insures correct

accomplished by adjustment of the B1 resolver

subsystem operation, or it isolates between an EIA failure,

by means of the fine-adjustment worm gear and

including a defective buffer amplifier, and a linkage failure.

worm wheel during system boresighting.

The status of the system at the end of the test is indicated

by means of four indicators on the gunner armament

(8) Resolvers B2, B3, and B4 in the linkages are

prezeroed at the factory and are not adjustable. Both the

control panel. The indicators are marked Go INTFC (in

bodies and the shafts of these resolvers are securely

the AH-lS(Mod) helicopter) or EIA (in the AH-1S heli-

mount ed in the linkage arms. Pitch resolver B1 may require

copter

), PLT and GNR. After the BIT is

field adjustment during system boresighting. The shaft of

initiated, it the EIA and linkages operate normally, the

green GO indicator lights within 0.3 second and remains

this resolver is factory adjusted and securely fastened;

on for 5 to 10 seconds. When the indicator lights, the sys-

however, the body is fitted with a fine-adjustment worm

tem returns to normal operation. A failure is indicated if

gear and worm wheel. The worm wheel is attached to the

1-16