203: Avionics/Electrical System

203.1.1 Discuss the purpose of the following navigation systems

a. Attitude Director Indicator (ADI) – The ADI on the pilot and copilot instrument panel is the primary attitude reference in all phases of flight. Pitch and roll indicators are displayed by a sphere in relation to a fixed miniature aircraft symbol displays indications. The sphere is light colored above the artificial horizon bar, black below the bar, and is marked in 5-degree pitch increments in both directions. Roll indications are given by two markers 180 degree apart that move around the periphery of the sphere. Ten degree bank increments to 30 degree, then 30-degree increments to 90 degree are marked on the bottom of the increment. Magnetic heading indications are also provided around the sphere’s horizon. The ADI has unlimited freedom of movement about the pitch and roll axes.

b. Standby Attitude Indicator – A backup attitude indicator is on the pilot instrument panel for use should the ADIs become unreliable.

c. Computer Aided Inertial Navigation System (CAINS) - The inertial Navigation Set, commonly termed Carrier Aircraft Inertial Navigation System, provides primary long-range navigation data. The CAINS, through the Inertial Navigation Control Group, commonly termed Inertial Navigation System Interface (INSI) interfaces with other aircraft navigation systems. The CAINS and INSI are integrated in a complete functioning Inertial Navigation System (INS) that provides aircraft velocities, attitudes, and positions to associated aircraft systems.

d. Attitude Heading Reference System (AHRS) – Two identical AHRSs provide roll, pitch, and heading information for display on the pilot and copilot ADI, BDHI, and CI. The AFCS, weather radar, Doppler antenna, and Omega receiver also use information from the system selected by the pilot. AHRS No. 1 is ordinarily selected by the pilot while AHRS No. 2 is ordinarily selected by the copilot. Each pilot may select either AHRS No. 1 or AHRS No. 2 through the use of the two AHRS select switches.

e. Tactical Air Navigation (TACAN) – The tactical air navigation set is a UHF navigation receiver-transmitter that is used to provide navigation information by determining slant range and relative bearing to a selected tacan station. The tacan station can be surface (land-based or shipborne) or airborne. Surface stations can be either tacan or vortac. An airborne station supplies only slant-range distance unless the aircraft is specially equipped with a bearing transmitter and a rotation antenna.

f. Global Positioning System (GPS) – The C-2A GPS navigation set is a worldwide all weather navigation aid that receives and processes navigation information from NAVSTAR GPS satellites. GPS is a space-based radio positioning system that provides its users with highly accurate position, velocity, and time data. This service is provided globally, continuously, and under all weather conditions to users. GPS receivers operate passively, thus allowing an unlimited number of simultaneous users. The GPS has features that can deny accurate service to unauthorized users, prevent spoofing, and reduce receiver susceptibility to jamming.

203.1.2 Discuss the purpose of the following communication systems

a. Intercommunication System (ICS) – The ICS provides voice communication among four primary ICS stations (pilot, copilot, and forward cabin left side and aft cabin right side), and two auxiliary ICS stations (nose wheelwell and aft cabin left side.) The ICS also connects with the radio equipment. At each of the four primary ICS stations, control panel switches permit the operator to select the desired operation mode. Each ICS station operator may listen to any or all of the radios and to audio from the tacan, LF, ADF, VIR-31 navigation receivers, IFF Mode 4 interrogations and replies, and the public address system.

b. Ultra High Frequency (UHF) Radio – The aircraft is equipped with two UHF communication radios. The ARC-159A has frequency range of 225.000 to 399.975 MHz and can be manually tuned in 25-kHz steps, making 7,000 channels available. Twenty channels can be preset. There is a guard receiver tuned to 243.0 MHz that can be operated simultaneously with the main receiver. The radio has an ADF capability in conjunction with the OA-8697/ARD.

c. High Frequency (HF) Radio – The HF communications radio has a frequency range of 2.0000 to 29.9999 MHz and can be manually tuned in 100-Hz increments making 280,000 channels available. Thirty channels may be preset. The radio has six operation modes: voice upper sideband, voice lower sideband, amplitude modulation equivalent, continuous wave, data upper sideband, and data lower sideband.

d. Very High Frequency (VHF) – The ARC-175/VHF-20 (B) has a frequency range from 116.000 MHz to 151.975 MHz and can be tuned in 25-kHz steps providing 1,440 channels. There is no preset channel capability and each frequency is tuned manually. There is no direction finding capability.

e. Public Address – The PA system permits crew-to-passenger voice communication, provides a tie-in with the LF ADF receiver for passenger entertainment, and signals with distinctive chiming tones whenever a passenger advisory light is turned on by the crew. Volume of speaker output is automatically adjusted for ramp/flight operation and for cabin depressurization.

203.1.3 Discuss the purpose of the following systems

a. Identification Friend or Foe (IFF) – The AN/APX-72 transponder provides coded identification and altitude signals in response to interrogations from surface or airborne stations so that the stations can establish aircraft identification, control air traffic, and maintain vertical separation. The system has five operating modes: 1,2,3/A, C and 4. Modes 1 and 2 are IFF modes, mode 3 (civil mode A) and C (automatic altitude reporting) are primary air traffic control modes, and Mode 4 is the secure (encrypted) IFF mode.

b. Weather Radar – The weather radar provides weather avoidance information out to a range of approximately 240 miles by means of a three-color map display showing increasing levels of rainfall intensity in green, yellow, and red, with red being the most intense. Blue is used for range circles and for the azimuth line, which are displayed as dotted lines, and for the alphanumeric. A track cursor is displayed in yellow. In addition to its primary weather function, the radar can be used for ground mapping. A Doppler derived display of navigation information can be superimposed on either the weather or the mapping display, or displayed alone. If the aircraft incorporates AFC 150 (GPS), the navigation information is supplied by the CDNU.

c. Radar Altimeter – The AN/APN-194 radar altimeter in a pulsed, range-tracking radar that measures the height of the aircraft over the surface, operating in a range of from0 to 5,000 feet. Altitude is continuously presented on an indication that has the only operation control. When the aircraft exceeds 5,000 feet AGL or loss of signal is experienced, an OFF flag is displayed and the pointer is rotated behind a mask to prevent use of the information.

d. Crash Survivability Flight Incident Recorder (CSFIR) – The Flight Recorder Set (FRS) acquires selected flight data and records a minimum of 2 hours of this information into crash – protected memory. The flight data being recorded in Time, Day, Year, Latitude, Longitude, Velocity East, Velocity North, Velocity Up, Pressure Altitude, Indicated Airspeed, Magnetic Heading, Normal Acceleration, Pitch Attitude, Roll Attitude, Elevator Position, Aileron Position, Rudder Position, Left Engine Torque, Right Engine Torque, Left Engine Tach, Right Engine Tach, and Weight On Wheels. When the flight data portion of crash – protected memory becomes full, the newest information is recorded over the oldest information so that the most recent information is available. The FRS also records 30 minutes of the following audio information: Pilot Intercom, Copilot Intercom, Cargo Door Intercom, and Cockpit Wide – Area Audio. When more than 30 minutes of audio is recorded, the newest audio is recorded over the oldest audio so that the most recent 30 minutes of audio from each position is available.

203.1.4 Discuss the purpose of the following landing aids

a. Automatic Carrier Landing System (ACLS) – The term ACLS applies to aircraft equipped with ASW-25 data-link receivers using carrier- or – shore – based AN/SPN – 10, SPN-42, or MPN-T1 ACLS facilities. Four modes of approach are available, depending on aircraft equipment. In Mode 1 approaches, data-link-transmitted ACLS signals are coupled to the autopilot after ACLS radar lock-on and control the aircraft until touchdown. Mode 1A approaches differ form Mode 1 approaches in that data-link ACLS signals are uncoupled at ½ mile (approximately 200 feet altitude) from touchdown. Mode 2 approaches the pilot-controlled using data-link needles information displayed on the ADL or CI. A Mode 3 approach is a controller talk-down approach using no special equipment on the aircraft. The C-2A has a capability Mode 2 and 3.

b. Aircraft Approach Control System (AACS) – The AACS receiver-decoder is an ILS receiver used with carrier-based SPN-41 (C-scan) transmitters for manual instrument approaches and landing or for an independent monitor during an ACLS approach. The system operates in the range between 15.4 and 15.7 GHz on any of 20 channels selected by the copilot. Channel selection is made on the ARA-63 control panel in the right console.

203.1.5 Discuss the purpose, location, and color of the following exterior lights

a. Wing and tail position – There are three position lights: one on each wingtip and one at the aftmost fuselage station. The left wingtip light is red, the right is green, and the taillight is white. The lights provide a visual indication of aircraft attitude and direction.

b. Anti-collision – There are two dual lamp unit anticollision strobe lights: one on the right outboard vertical stabilizer and one on the lower fuselage aft of the nose wheel well. The lights can be selected to flash either red or white. The white strobe lights are disabled when the aircraft is on the deck, but may be tested on the deck using the approach lights test switch.

c. Landing/taxi – The taxi/landing light is on the forward nosewheel door, and is used to illuminate the area in front of the aircraft.

d. Approach – An approach light assembly on the nose gear fairing indicates aircraft AOA to the LSO during a carrier or field carrier or landing approach. The approach light assembly contains three individually controlled lights: red, green, and amber to indicate low, high, or optimum AOA, respectively. The approach light system operates when the landing gear is locked down and the hook is extended. The approach lights can be checked while the aircraft is on deck by setting the approach light switch on the center overhead console from NOR to Test. This causes the light corresponding to the AOA pointer position to come on. If the ANTICOLLISION light switches are at WHT and Both or Upper, the white strobe lights will also come on regardless of the position of the exterior lights master switch.

203.1.6 Discuss the purpose of the following lights

a. Advisory – The advisory lights panel on the lower right of the center instrument panel consists of the 23 advisory lights and 1 spare (24 advisory lights for aircraft incorporating AFC 150). The panel is visible to both the pilot and the copilot. The advisory lights provide information on system operation or malfunctions of which the pilots should be aware. Pressing the LIGHTS MASTER TEST button tests all lights on the panel.

b. Caution – The caution lights panel is on the upper left of the center instrument panel visible to the pilot and copilot. The panel composed of 22 caution lights and 2 spares. Each caution light provides an indication of a malfunction or system condition requiring corrective action. When a caution light comes on, the two MASTER CAUTION lights also come on. The caution lights remain on until the cause has been eliminated; the MASTER CAUTION lights can be reset. All lights on the caution lights panel is tested by pressing the LIGHTS MASTER TEST button.

203.1.7 Discuss the purpose of the following flight reference system

a. Pitot Static – The Pitot-static system provides Pitot (impact) and static (ambient) pressure as needed to the airspeed indicators, vertical speed indicators, SCADC, and the standby function of the servoed barometric altimeters. Pitot pressure is admitted through two electrically heated Pitot tubes forward of the windshield. The left tube directs pressure to the pilot airspeed indicator and the SCADC; the right tube directs pressure to the copilot airspeed indicator and the impact pressure transducer (q-feel monitor). The two Pitot systems are completely independent of each other and the static system. Static pressure comes through six static ports, three on each side of the fuselage. The two forward ports supply the pilot airspeed indicator, vertical speed indicator, the SCADC, and the standby function of this altimeter. The two aft static ports supply the impact pressure transducer, the copilot airspeed and vertical speed indicators, and the standby function of the altimeter. The two static ports between the pilot and the copilot ports (one on each side of the fuselage) supply static pressure to the cabin pressurization system pressure regulator sensor. The cabin pressurization port is below the pilot/copilot ports on the left side and above them on the right side. Pitot anti-icing power is provided by setting the two position PITOT toggle switch on the ANTI-INCING, DE-ICING, DE-FOG panel to ON. This provides 115 VAC power for heating the Pitot tubes and the total temperature probe, and 28 vdc for heating the AOA transmitter probe.

b. Angle of Attack (AOA) – The AOA system measures the angle between the longitudinal axis of the aircraft and the relative wind. The system is threefold in operation and provides a visual indication of aircraft angle of attack, a physical indication through the rudder pedal shakers that the aircraft is approaching a stalling angle of attack requiring corrective flight control action, and a visual indication to both the pilots and the LSO during a field or carrier landing approach of approach speed and altitude. The AOA system is powered by warning bus No. 1 and consists of five major units: an AOA transmitter, an AOA indicator, an approach light, an approach indexer, and a rudder pedal shaker. During flight, the system is completely automatic. AOA indications are only accurate during balanced flight. Unbalanced flight conditions will give widely varied airflow direction in the vicinity of the probe.

203.1.8 Discuss the function and purpose of the following alternating current (ac) power supply and control system components

a. AC generators – The primary power supply system consists of two direct, engine-driven, 90/60 kVA, ac generators. The generators supply 115/200 vac, 400 Hz, three-phase power or two separate, non-paralleled systems. In addition to a generator, each system contains a voltage regulator, two differential current transformers, a supervisory panel, and a main line contactor. Each generator is on the reduction gear section of its respective engine and is maintained at the proper operating frequency by the constant-speed characteristics of the engine.

b. Supervisory panels – The generators are protected against undervoltage, feeder fault, underfrequency, overvoltage, and phase current unbalance by protective devices in the circuit and automatically trip off the line when one of these conditions occurs. When this happens, a caution light in the cockpit comes on to indicate which generator system is inoperative. If the generator trips off the line because of an underfrequency condition, and if the cause of that condition is rectified, the supervisory panel will automatically reconnect the generator to the system as soon as the frequency is within limits. If the generator trips off the line because of any other fault and discrepancy is corrected; the generator can be reset with the generator control switches in the cockpit. Resetting the generator causes the caution light to go out. If the generator cannot be reset, the remaining generator system can supply the entire aircraft electrical power requirements through ac bus tie circuitry when the AC BUS TIE switch is at ON.

c. Voltage regulators – The regulator controls generator output by adjusting the power to the exciter field winding, and regulates output voltage to +/- 1% under fixed ambient or fixed load conditions. This automatically compensates for excessive change in generator line voltage.

d. Emergency generator – The emergency generator is continuous duty and self cooled. It provides 115-200 vac, three phase, 380 to 420 Hz power, rated at 10 kva while turning at 7600 to 8400 rpm. The generator supports its drive motor and is self excited. It uses a control unit mounted beneath the generator to control the operation of the generator.

e. Transformer rectifier – The transformer rectifier receive ac power from left and right generator buses and feed systems that are independent of each other. If a transformer rectifier fails, the systems can be integrated so that the operating transformer rectifier supplies the entire dc load. When a transformer rectifier fails, it is automatically tripped off the line and a caution light in the cockpit informs the pilot. If both transformer rectifiers fail, operation of the emergency generator is automatically initiated.

203.1.9 Discuss the purpose of the Automatic Flight Control System (AFCS) * The AFCS provides directional stability augmentation, three-axis attitude control, and automatic flightpath control of the aircraft. The AFCS receives manual inputs from the pilot and copilot control wheels and from the switches on the AFCS control panel. Automatic aircraft sensor inputs are from the SCADC and the AHRS. AFCS outputs are sent to the elevator, aileron and rudder actuators for all axis control, to the elevator and rudder trim actuators for automatic trim, and the q-feel actuator for pitch force gradient adjustments.

For inputs, comments, or questions please contact:


AMS1 Mark L. Starr

AZC(AW/NAC) Kimberly King