Aviation Electronics Technician 1 - Historic Naval Ships Association

stabilized deck-coordinated system referenced to thetouchdown point on the flight deck.3. Digital computer. This is a general-purposecomputer used to provide functions for radar datastabilization, data filtering, and computationsrequired for control of the aircraft.4. Data link monitor. This subsystem continuouslychecks data link transmissions for errors. Ifthe messages do no check properly, the monitor willswitch the system to either Mode II or Mode III, orwill generate a waveoff signal.5. Control console. This console monitors andcontrols the various functions of the landing system.RADAR BEACON AN/APN-154BThe radar beacon is located on the aircraft and isused to receive the Ka-band signal interrogationsfrom the LCC radar. The radar beacon then transmitsX-band replies to the carrier to provide preciseaircraft position data.APPROACH POWER COMPENSATORAN/ASN-54The approach power compensator (APC)automatically adjusts throttles to maintain theangle-of-attack, and thus, the airspeed during aircraftlanding approach. It can be used for all carrierlandings and is required for Mode I approaches. ForMode II and Mode III approaches, the APC isoptional. Data from the angle-of-attack transducer,normal accelerometer, and the stick/stabilizer positionare used to control an electromechanical servoactuator. This servo actuator is coupled to the throttlelinkage on the engine fuel control.ATTITUDE REFERENCE INDICATORID-1791/AThe ID- 1791/A (VGI) is used to display the glidepath errors from either the data link or monitor link oncross pointer needles. This indicator also determinesand displays backup pitch and roll attitude, as well asdisplaying side-slip and turn rate.DISCRETE MESSAGE INDICATOR128AV66836This indicator is located on the aircraft. Itdisplays nine status indications from the one-way linksystem, autopilot, and the beacon radar.WARNING INDEXER PANELThree warning lights on the warning indexerpanel informs the pilot of the status of the approachpower compensator, the status of the AFCS, andwhether a waveoff has been initiated. The threeindicators are the APC STBY, AFCS OUT, and theWAVEOFF indicators. The APC STBY willilluminate when the APC is in standby. The AFCSOUT will illuminate when the autopilot system is notoperating properly. The WAVEOFF indicator willilluminate when a wave-off has been initiated. Wheneither the AFCS OUT or the WAVEOFF indicatorsilluminate while in Mode I approach, the pilot isrequired to immediately take over control of theaircraft.APPROACH INDEXER 1284V653-1This unit is located on the aircraft. It provides anadditional angle-of-attack in the pilot’s field of view.This unit is used when flying cross pointers on aMode II approach or when monitoring display on aMode I approach.PRINCIPLES OF OPERATIONLearning Objective: Recognize the operatingprinciples of the automatic carrier landingsystem.The all-weather combination AFCS/ACLSprovides automatic, semiautomatic, or manualoperation for aircraft carrier operations withminimum use of airborne electronic subsystems. Theaircraft control commands are generated by shipboardcomputers so that the necessary pitch and banksignals can be received by the AFCS via the one-waydata link system. This closed-loop operation betweenaircraft and carrier provides automatic control totouchdown. This system provides a final approachand landing for carrier-based aircraft during daylightor darkness, with minimum interference forconditions of severe weather and sea state, and nolimitation due to low ceiling and visibility.There are three modes of operation of the ACLSthat can be selected by the pilot—Mode I, Mode II,and Mode III. Mode I is a fully automatic approachfrom entry point to touchdown on the flight deck.Mode II requires manual control of the aircraft. Inthis mode, the pilot controls the aircraft by observing9-3