Instrumentation – About ATPL Subjects

Instrumentation in a cockpitIn Instrumentation, you will learn about the various systems and instruments onboard an aircraft that are essential for a pilot to understand.

This includes speed, navigation and system monitoring.

This is only meant as a guide to the Instrumentation subject as it applies to the Bristol Groundschool ATPL theory course.


Instrumentation Topics

Below is a look at the individual topics the Bristol Groundschool ATPL course breaks Instrumentation into and some of the things you’ll learn in each topic.


Principles and Sensors

Primary instruments, electronic flight instrument systems, resistive sensors, thermocouples, air temperature probes, time measurement, the Hobbs meter, and accelerometers.

Pressure Sensing

Diaphragms, pressure capsules, the Pitot Static System, finding dynamic pressure, the static ports, large aircraft systems, angle of attack sensors, and pressure type alpha sensors.

Pressure Altimeters

Simple altimeters, sensitive altimeters, ADC driven systems, altimeter errors, line blockages, and leaks, and altimeter pressure settings.

Vertical Speed Indicators

The simple VSI, instantaneous VSIs, instrument displays, errors, and blockages.

Airspeed Indication

IAS and TAS, units, flat plate indicators, the mechanical airspeed indicator, ADC driven instruments, calibrated airspeed, density, TAS calculations, alternative phraseology, instrument displays, pitot blockages and leaks.

Machmeters and ADCs

The machmeter, the local speed of sound, calculating mach number, cockpit indicators, EAS/CAS/TAS/Mach relationship, crossover altitude, air data computers, ADC inputs, and outputs.


The molecular theory of magnetism, magnetising and demagnetising, magnetic fields, the Earth’s magnetism, variation, magnetic direction, compass direction, and the compass swing.

Direct Reading Compasses

The direct reading compasses, acceleration errors, turning errors, steep turns, and liquid swirl.


Rigidity, precession, gimbals, classification of gyroscopes, degrees of freedom, classification by use, gyroscope wander, rate gyros, rate integrating gyros, ring laser gyros, frequency lock and dither.

Turn Indicators

The turn indicator, the importance of orientation, slip and skid indicators, and the turn coordinator.

Attitude Indicators

Direct reading attitude indicators, bank indicators, turning errors, acceleration on take-off, the principle of operation, servo-driven attitude indicators, vertical gyros and the AHRS and EFIS displays.

Direction Indicators

Directional gyros, the direction indicator, DI construction and operation, DI errors, apparent drift caused by Earth’s rotation, the latitude nut, transport wander and DI drift calculations.

Remote Reading Compasses

The flux detector, measures the component of H in each leg, transmitting the signal, the gyro unit, initial alignment, and system errors.

Inertial Navigation Principles

Basic principles, the acceleration axes, stable platforms, and strapdown systems, initial levelling and alignment, levelling, latitude and longitude, navigation, calculating longitude, calculating heading, track and drift, controls and indicators, the control display unit (CDU), INS terminology, passing a waypoint, the wander angle INS, inertial systems errors, schuler tuning and schuler errors.

Inertial Reference Systems

Initialisation, controls, and indicators, setting up, fast re-alignment, IRS errors, IRS outputs, and inputs.

Flight Management Systems

FMS components, FMS performance database, LNAV and VNAV, FMS vertical navigation, cost management with the FMS, FMS inputs and outputs, control display units, determining aircraft position, FMS set-up, position initialisation, routing, performance initialisation, altitudes and winds, take-off reference and ACARS speeds.

Using the Flight Management System

Flight process, nav display output, navigation, ANP and RNP, map shift, Calculated ETAs, changing the routing, lateral offset, fuel calculations, approach and landing, FMS outputs and dual FMC dual MCDU operation.

Electronic Flight Instrument Systems

Components, primary flight displays, the speed tape, decision height and radio height, pitch limit symbols, flight mode annunciator, flight directors, Boeing navigational displays, full VOR/ILS mode, full nav mode, the map mode, the plan mode, weather radar colouring, remote light sensor, transferring data feeds, EFIS control panels, ROSE VOR, ROSE NAV, ARC, PLAN, engine and systems screens and typical indications.

Datalink Communications

The different systems, CPDLC ground systems, CPDLC aircraft equipment, the CMU, CPDLC messages, CPDLC frequencies, automatic dependent surveillance (ADS) broadcast, ADC-C report contents, emergency mode and future air navigation systems (FANS).

Automatic Flight

A three axis system, regulatory requirements, autopilot control, and stability, inner and outer loops, gain variation, gain adaptation, direct control law, flight envelope protection, trim systems, yaw damping, and AFCS protection systems.

Automatic Flight Path Guidance

Selected modes, engaging the autopilot, LNAV and VNAV, vertical speed and flight path angle, altitude control, heading control, VOR tracking, control wheel steering, speed control and autothrottle.


Autoland, fail operational and fail passive, two channel fail operational systems, the alert height, localiser capture, glideslope capture, the final stages, after touchdown and three channel terminology.

Flight Directors

Flight directors, integrating autopilot and flight directors, flight director demands, satisfying a roll demand, rolling out, ignoring a roll demand, alternative display and independent operation.

Alerting Systems

Alerting systems, alerting mechanisms, cockpit equipment, EICAS, stall warning and protection, inputs and outputs, stall warnings, speed strip low speed markings, overspeed warning, take-off warning system, the altitude alerting system, low level radio altimeters, radio altimeter system operation, frequency bands and radio altimeter cockpit equipment.


Ground proximity warning equipment, terrain awareness warning system, cockpit equipment, GPWS modes, EGPWS and classification of warnings and alerts.

Airborne Collision Avoidance System

ACAS/TCAS requirements, principle of operation, the tau area, traffic advisory, resolution advisory, range and limitations, cockpit displays and terminology, symbol for traffic causing an RA, symbol for traffic causing a TA, proximate traffic, no-bearing advisories and TCAS system components.

Flight Data Recording

Flight data recording, the cockpit voice recorder, components, the digital flight data recorder, DFDR components and ACMS.

Powerplant System Monitoring

RPM measurement, the mechanical tachometer, the mechanical tachometer display, the electrical tachometer, turbine displays, the synchroscope, vibration sensors, torque measurement, gas turbine thrust indications, EPR gauges and analogue instrumentation.

Fuel Flow and Contents

Fuel and the hazards of different units, indications provided, resistive float volume indicators, capacitative mass measurement, manual fuel contents checking, fuel flow gauging, variable orifice volume flow indicators, turbine volume flow indicators, mechanical mass flow indicators, rotor torque and electronic mass flow indicators.

Digital Circuits and Computers

The von Neumann model, central processing units, memory, ROM, PROM, EPROM, software, 64 bit binary, machine code, assembly languages, high-level languages, scripting languages, connections and software certification.

Newer Technology

Electronic flight bag, electronic checklists, head-up display, synthetic vision system and enhanced vision system.


Instrumentation Exams

The exam for Instrumentation lasts 1 hour and 30 minutes. You’ll have 60 multiple-choice questions to answer during this time, with the pass rate being 75%.


An Example of an Instrumentation Exam Question

This is an example of the type of question you may have in an Instrumentation exam. For more questions like this one, visit the BGSonline question bank to start revising with over 15,000+ ATPL, CPL, IR, and PPL questions. Subscriptions start from £23 for one month for access to ATPL/CPL questions.

Question: Which component of the B737-400 Flight Management System (FMS) is used to enter flight plan routing and performance parameters?

A) Multi-Function Control Display Unit

B) Flight Director System

C) Flight Management Compute

D) Inertial Reference System

Click to reveal the answer

The answer is A, Multi-Function Control Display Unit.

The CDU is used to enter start-up position, route etc.


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