NCAA Aircraft Maintenance Engineer Licence - Avionics/Electrical (Nigeria)

An aircraft DC circuit powered by a 28 V DC bus draws a constant current of 4.0 amperes. According to Ohm's Law, what is the total resistance of the circuit load?

• A7.0 Ohms
• B112.0 Ohms
• C0.14 Ohms
• D14.0 Ohms

What is the standard frequency of main AC electrical power generation in modern commercial aircraft?

• A400 Hz
• B50 Hz
• C60 Hz
• D1000 Hz

What is the primary function of a Transformer-Rectifier Unit (TRU) in an aircraft electrical system?

• AStep down 115 V AC power and convert it into 28 V DC power
• BConvert 28 V DC battery power into 115 V AC 400 Hz power
• CRegulate the output voltage of the main engine-driven AC generator
• DIsolate essential avionics buses during engine start

Which flight instrument receives input EXCLUSIVELY from the static pressure port of the pitot-static system?

• AAltimeter and Vertical Speed Indicator (VSI)
• BAirspeed Indicator (ASI)
• CMachmeter
• DTurn and Slip Indicator

What is the main purpose of equipping an aircraft pitot tube with an internal electrical heating element?

• APrevent ice formation from blocking the ram air inlet during flight in icing conditions
• BHeat static pressure lines to prevent water vapor condensation
• CMaintain calibrated airspeed sensor temperature at a constant value for digital conversion
• DPrevent thermal expansion of the pitot tube housing at high speed

What is the designated frequency band allocated for civil aviation VHF voice communication transceivers?

• A118.000 MHz to 136.975 MHz
• B108.000 MHz to 117.950 MHz
• C225.000 MHz to 399.950 MHz
• D2.000 MHz to 29.999 MHz

Which frequency band is allocated for V-O-R (VHF Omnidirectional Range) navigation stations?

• A108.00 MHz to 117.95 MHz
• B118.00 MHz to 136.975 MHz
• C962 MHz to 1213 MHz
• D190 kHz to 535 kHz

What is the primary function of vent plugs on aircraft lead-acid or nickel-cadmium storage batteries?

• ASafely vent hydrogen and oxygen gases produced during charging while keeping electrolyte…
• BAllow manual addition of concentrated sulfuric acid during routine maintenance
• CProvide pressure relief during high-altitude rapid decompression only
• DDrain excess electrolyte into the battery sump compartment

In digital logic circuits, what is the output state of a standard 2-input A-N-D gate when Input A is HIGH (1) and Input B is LOW (0)?

• ALOW (0)
• BHIGH (1)
• CPulsing at 400 Hz
• DHigh Impedance (Tri-state)

Why are static discharge wicks installed on the trailing edges of aircraft wingtips and control surfaces?

• ABleed off accumulated precipitation static charge into the air to reduce radio interferen…
• BProvide electrical bonding paths across control surface hinges
• CAct as lightning strike dissipators to prevent structural melting
• DGenerate localized turbulence to delay air separation over flight controls

Under Nigeria Civil Aviation Regulations (Nig. CARs) Part 2, what is the minimum age requirement for an applicant to be issued an Aircraft Maintenance Engineer (AME) Licence?

• A21 years
• B18 years
• C25 years
• D20 years

In an aircraft DC generator system, what component prevents the storage battery from discharging back into the generator when generator voltage drops below battery voltage?

• AReverse Current Cutout Relay (or Reverse Current Diode)
• BVoltage Regulator
• CEqualizer Resistor
• DOvervoltage Relay

Three resistors with values of 10 Ohms, 15 Ohms, and 25 Ohms are connected in series across a 50 V DC bus. What is the total equivalent resistance of the circuit?

• A50 Ohms
• B4.8 Ohms
• C25 Ohms
• D150 Ohms

What information does the turn element of a standard gyroscopic Turn Coordinator present to the pilot?

• ARate of roll and rate of turn about the roll and yaw axes
• BPitch attitude and bank angle relative to horizon
• CAbsolute magnetic heading of the aircraft
• DRate of climb and descent in feet per minute

What type of gyroscope is utilized in an aircraft Attitude Indicator (Artificial Horizon)?

• AEarth gyro (vertical gyro) mounted with its spin axis aligned vertically
• BTied gyro mounted with its spin axis horizontal
• CRate gyro with one degree of freedom
• DDirectional gyro aligned with magnetic North

Within what specific frequency range do Instrument Landing System (I-L-S) Localizer ground stations operate?

• A108.10 MHz to 111.95 MHz (odd-tenths decimals)
• B118.00 MHz to 136.95 MHz
• C329.15 MHz to 335.00 MHz
• D962.00 MHz to 1213.00 MHz

What electrical conversion process is performed by a static inverter in an aircraft power system?

• AConverts Direct Current (DC) input into Alternating Current (AC) output
• BConverts 115 V AC 400 Hz into 28 V DC
• CConverts single-phase AC into three-phase AC at the same voltage
• DConverts high-voltage DC into low-voltage DC

Why are electrical wire bundles in aircraft routed and clamped with a minimum clearance away from fluid lines (such as fuel, hydraulic, or oxygen pipes)?

• APrevent electrical arcing from puncturing fluid lines and causing fire or explosion hazard
• BPrevent magnetic interference from fluid flow from corrupting wire signals
• CAllow cooling airflow to pass between wires and pipes
• DPrevent hydraulic fluid from absorbing electrical charge

How many total bits compose a standard ARINC 429 digital data bus word?

• A32 bits
• B16 bits
• C24 bits
• D64 bits

What parameter is directly measured by an airborne Distance Measuring Equipment (D-M-E) interrogator?

• ASlant-range distance between the aircraft and the ground transponder
• BDirect horizontal ground distance to the runway touchdown zone
• CTrue groundspeed of the aircraft over the terrain
• DGeometric altitude above mean sea level

An aircraft landing light connected to a 28 V DC bus draws a current of 10 amperes. What is the power consumed by the landing light?

• A280 Watts
• B2.8 Watts
• C38 Watts
• D784 Watts

Under Nig. CARs Part 5, what mandatory document must be signed by an authorized AME prior to releasing an aircraft to service after avionics maintenance?

• ACertificate of Release to Service (CRS)
• BAirworthiness Directive Compliance Form
• CCertificate of Airworthiness (C of A)
• DMaster Minimum Equipment List (MMEL)

What is the primary function of a Yaw Damper system in a jet transport aircraft?

• ASuppress Dutch roll oscillations automatically by commanding rudder deflections
• BMaintain wings-level attitude during turbulence without pilot input
• CPrevent overspeeding during high-speed descents
• DAutomatically trim the elevator for elevator pitch changes

What visual and aural indications does a pilot receive when passing over an ILS Outer Marker (OM) beacon?

• ABlue light flashing and continuous 400 Hz Morse code dashes
• BAmber light flashing and 1300 Hz alternate dots and dashes
• CWhite light flashing and continuous 3000 Hz Morse code dots
• DGreen light flashing and continuous 1000 Hz audio tone

In digital logic, what is the output state of a 2-input O-R gate when Input A is 0 and Input B is 1?

• AHIGH (1)
• BLOW (0)
• CUndefined
• DInverted (0)

In what radio frequency spectrum band do ILS Glide Path (Glideslope) transmitters operate?

• AUHF band (329.15 MHz to 335.00 MHz)
• BVHF band (108.10 MHz to 111.95 MHz)
• CLF band (190 kHz to 535 kHz)
• DSHF band (4.2 GHz to 4.4 GHz)

An aircraft emergency battery has a rated capacity of 36 Ampere-hours (Ah). If it delivers a steady discharge current of 6 Amperes to essential avionics, how long will the battery last before complete discharge?

• A6.0 hours
• B216 hours
• C0.16 hours
• D1.5 hours

Why are flexible metal bonding jumpers connected across aircraft movable flight control surface hinges?

• AProvide a low-resistance electrical path to prevent electrostatic charge accumulation and…
• BTransfer mechanical trim loads across the structural hinge line
• CProvide grounding paths for high-voltage de-icing boots
• DPrevent galvanization between aluminum skins and steel hinge pins

What physical environmental parameter is directly measured by an aircraft barometric altimeter to indicate flight altitude?

• AAmbient static atmospheric pressure
• BRam air dynamic pressure from pitot tube
• CReflected radio wave propagation time
• DAir density change inside sealed aneroid capsule

What is the standard characteristic impedance of coaxial cables used for interconnecting aircraft radio RF antennas and receivers?

• A50 Ohms
• B75 Ohms
• C300 Ohms
• D600 Ohms

An AC inductor with an inductance of 5.0 millihenries (mH) is connected to a 115 V, 400 Hz aircraft AC power bus. What is the inductive reactance ($X_L$) of the inductor?

• A12.57 Ohms
• B2.00 Ohms
• C25.13 Ohms
• D0.08 Ohms

Two avionics DC loads with resistances of 20 Ohms and 30 Ohms are connected in parallel across a 28 V DC bus. What is the total equivalent resistance ($R_{eq}$) of the combination?

• A12.0 Ohms
• B50.0 Ohms
• C600.0 Ohms
• D25.0 Ohms

In an aircraft DC generator control system, what protection circuit action occurs if the Generator Control Unit (G-C-U) detects a sustained overvoltage condition?

• ATrips the Generator Field Relay (GFR) to remove generator excitation
• BOpens the main battery circuit breaker
• CSwitches the generator output to an auxiliary dummy load resistor
• DIncreases field current to force voltage breakdown

What immediate cockpit indication and backup behavior occurs if an aircraft Air Data Computer (A-D-C) experiences a primary pitot-static sensor data failure?

• ARed flags or amber dashes appear on the PFD airspeed and altitude tapes, reverting to sta…
• BThe autopilot automatically pitches down 15 degrees
• CThe radar altimeter displays negative altitude
• DThe TCAS system immediately initiates a resolution advisory descent

What causes position (installation) error in an aircraft pitot-static instrument system?

• ADisturbance of airflow surrounding static pressure ports at varying angles of attack and…
• BFriction within the mechanical linkage connecting aneroid capsules to indicators
• CCapillary restriction in long static lines during rapid climb
• DThermal expansion of air inside the pitot tube

According to the principle of gyroscopic precession, if a deflecting force is applied to the rim of a spinning gyroscope rotor, where will the resulting angular displacement occur?

• A90 degrees ahead in the direction of rotor rotation
• B90 degrees behind the direction of rotor rotation
• C180 degrees opposite to the point of applied force
• DAt the exact point of force application

How does an airborne V-O-R receiver determine the aircraft's magnetic bearing (radial) from a ground station?

• AMeasures phase difference between a 30 Hz reference phase signal and a 30 Hz variable pha…
• BCompares signal amplitudes of two directional loop antennas set at right angles
• CCalculates carrier Doppler shift as the aircraft moves toward the station
• DMeasures pulse time delay between interrogation and reply signals

How does an ILS Localizer receiver interpret horizontal deviation from the runway approach centerline?

• ACompares relative depth of modulation between 90 Hz (left) and 150 Hz (right) audio signa…
• BMeasures phase difference between horizontal and vertical antenna elements
• CMeasures frequency offset of the VHF localizer carrier wave
• DCompares pulse arrival times from dual ground transmitters

In an ILS Glide Path (Glideslope) system, what audio modulation frequencies define deviation above and below the proper glidepath slope?

• A90 Hz dominates above glidepath; 150 Hz dominates below glidepath
• B150 Hz dominates above glidepath; 90 Hz dominates below glidepath
• C400 Hz dominates above glidepath; 1300 Hz dominates below glidepath
• D1020 Hz dominates above glidepath; 3000 Hz dominates below glidepath

Why does an Automatic Direction Finder (A-D-F) system combine signals from both a Loop Antenna and a Sense Antenna?

• AEliminate 180-degree directional ambiguity in bearing to the NDB ground station
• BIncrease receiver operating range in the HF spectrum
• CProvide automatic gain control for single sideband audio
• DFilter out atmospheric precipitation static noise

What is the key operational advantage of Single Sideband (S-S-B) emission used in airborne HF communication transceivers compared to conventional Double Sideband AM?

• AConcentrates transmitter power into a single sideband, conserving power and spectrum width
• BEliminates need for an antenna tuning unit (ATU)
• CPermits line-of-sight satellite communications
• DProvides stereo audio quality free of fading

How does an aircraft S-E-L-C-A-L (Selective Calling) decoder alert flight crews to incoming radio calls?

• ADecodes a unique 4-tone audio pulse sequence to sound a cockpit chime and illuminate a ca…
• BContinuously monitors VHF voice channels and un-mutes speakers upon sensing pilot voice
• CTransmits a digital squelch signal to ground ATC controllers
• DScans all HF frequencies simultaneously until a carrier is locked

An aircraft step-down transformer has a primary-to-secondary turn ratio of 5:1. If 115 V AC 400 Hz is applied to the primary winding, what voltage is produced at the secondary winding?

• A23 V AC
• B575 V AC
• C28 V DC
• D115 V AC

What condition can cause catastrophic thermal runaway in aircraft Nickel-Cadmium (Ni-Cad) batteries during constant-voltage charging?

• AHigh battery temperature reducing internal resistance, causing increased charging current…
• BLow ambient temperature causing electrolyte freezing
• COverfilling cells with distilled water prior to charging
• DOperating the battery below 50% state of charge

What is the capacitive reactance ($X_C$) of a 20 microfarad (uF) capacitor operated on a 115 V, 400 Hz AC aircraft power bus?

• A19.89 Ohms
• B50.27 Ohms
• C0.05 Ohms
• D125.66 Ohms

In an automatic flight control system (AFCS), what is the fundamental difference between inner loop control and outer loop control?

• AInner loop provides rate damping/attitude stabilization; outer loop provides navigation g…
• BInner loop controls autothrottle; outer loop controls elevator trim
• CInner loop processes GNSS data; outer loop processes pitot-static data
• DInner loop operates manual elevator cables; outer loop operates hydraulic servos

What radio frequency band and typical operating frequency are used by airborne weather radar systems to detect precipitation droplets?

• AX-band (approximately 9.3 GHz to 9.5 GHz)
• BC-band (approximately 4.2 GHz to 4.4 GHz)
• CVHF band (approximately 108 MHz to 118 MHz)
• DK-band (approximately 24 GHz to 26 GHz)

What modulation method and operating frequency band are used by precision Radio Altimeters to measure aircraft height above terrain?

• AFrequency-Modulated Continuous Wave (FMCW) in the 4.2 GHz to 4.4 GHz band
• BPulse Modulation in the 1090 MHz band
• CAmplitude Modulation in the 118 MHz to 136 MHz band
• DPhase Shift Keying in the 1.5 GHz L-band