Brunei DCA CPL(A) Instrumentation cheat sheet

Static pressure decreases about 1 hPa per 27 ft near sea level; the standard atmosphere uses 1013.25 hPa and 15 °C at MSL with a lapse rate of 1.98 °C per 1000 ft.

Pitot pressure = static pressure + dynamic pressure; dynamic pressure q = ½ρV², so the ASI indicates true dynamic pressure only at the calibrated density.

Rigidity in space: a spinning rotor resists change of its spin axis; precession: an applied force produces drift 90° ahead in the direction of rotation.

A gyro needs two freedoms (spin axis plus one gimbal) for rigidity and three freedoms for a free gyro; the attitude indicator is earth-referenced, the heading indicator is not.

Real gases and instrument mechanisms give position error, density error, compressibility error and lag; only position error is corrected by the calibration chart (PEC).

Instrument lag and hysteresis are mechanical; temperature changes alter spring stiffness and fluid viscosity, so readings drift with temperature.

Random and real errors: parallax, friction in pivots, and scale error; a pre-flight check compares readings with known values (e.g. altimeter field elevation).

A vacuum- or pressure-driven gyro depends on a suction source; a low-vacuum warning or slow erecting indicates a degraded pneumatic supply.

ASI: capsule senses pitot (total) pressure, case senses static; the differential drives the pointer. Blocked pitot with open static makes the ASI behave like an altimeter.

Blocked static with open pitot: ASI over-reads in climb and under-reads in descent; altimeter freezes; VSI reads zero after a transient.

Altimeter: aneroid capsule responds to static pressure; subscale sets the reference. QNH gives elevation, QFE gives height above the reference, QNE (1013.25) gives flight level.

Altimeter errors: incorrect subscale (1 hPa ≈ 30 ft at low level), temperature error (cold air - the altimeter over-reads, true altitude lower), and lag/position error.

The 1-in-60 rule and temperature correction: in cold air, true altitude is lower than indicated; apply cold-temperature corrections when operating below 0 °C.

VSI: a calibrated leak (choke) delays case pressure change; the needle shows rate of change of static pressure. Lag of several seconds is normal; a stuck VSI reads zero.

VSI errors: lag, and a momentary reverse indication after a rapid attitude change; instantaneous VSI uses an accelerometer-based or electronic sensor.

Pitot heat and drain checks: pitot heat prevents icing; a blocked pitot drain hole causes ASI to under-read or freeze; static ports must be clear of ice and tape.

Colour arcs: white = flap operating range, green = normal operating range, yellow = caution range, red line = VNE; the ASI is calibrated in knots or mph.

Attitude indicator: vertical gyro, two freedoms (pitch and roll), erection mechanism (pendulous vanes or accelerometer) keeps the spin axis vertical; it indicates pitch and roll relative to the horizon.

Attitude indicator errors: acceleration error (during acceleration the horizon bar falsely shows a climb), turn error, and erection error; it must be caged/uncaged and checked for erection.

Heading indicator: horizontal gyro with a vertical spin axis, three freedoms; it drifts and must be reset to the magnetic compass periodically.

Heading indicator errors: real drift from friction and earth's rotation, apparent drift from latitude (transport wander), and precession from turns; it is not a magnetic instrument.

Turn coordinator: a rate gyro with its spin axis tilted about 30°, so it senses yaw rate and roll rate; it shows rate of turn and slip/skid via the ball.

Turn and slip indicator (turn needle): a rate gyro sensing yaw only; the ball is an inclinometer showing slip or skid, not rate of turn.

Standard rate of turn = 3°/s (2 minutes per 360°); the turn coordinator is calibrated to show standard rate at the appropriate airspeed.

Slip/skid: ball to the outside of the turn = skid (too much rudder); ball to the inside = slip (not enough rudder); step on the ball.

Gyro failure signs: attitude indicator flags or tilts, heading indicator drifts rapidly, turn coordinator fails to show rate; cross-check with standby instruments.

Construction: two or more magnets attached to a float and card, pivoted in a fluid-filled bowl; the fluid damps oscillation and supports the card.

The compass senses the horizontal component of earth's magnetic field; dip (inclination) increases with latitude and causes turning and acceleration errors.

Variation: the angle between true and magnetic north; deviation: error from the aircraft's own magnetic fields, corrected by a compass swing card.

Turning error: when turning through north the compass under-reads (lags), through south it over-reads (leads); the error is largest on north/south headings and near the poles.

Acceleration error: on east or west headings, acceleration causes a false turn indication toward north; deceleration gives a false turn toward south.

ANDS: Accelerate North, Decelerate South - the compass card swings toward the apparent turn during acceleration/deceleration on E/W headings.

Oscillation and settling: the compass is unreliable in turbulence and during turns; use the heading indicator as the primary heading reference.

Compass checks: the compass swing is performed on a known heading; the deviation card must be present and the compass readable from the pilot's seat.

Magnetic heading = true heading ± variation; compass heading = magnetic heading ± deviation.

Tachometer: mechanical (cable-driven) or electronic; reads engine/propeller RPM. A stuck or fluctuating reading suggests a drive or sensor fault; verify against other indications.

Manifold pressure gauge: absolute pressure in the induction system, in inches of mercury; it indicates power at a given RPM. A blocked line gives a fixed or wrong reading.

Cylinder head and oil temperature: thermocouple (CHT/EGT) or resistance (oil) sensors; a sudden rise suggests cooling or lubrication problems.

Oil pressure: direct pressure gauge or transducer; low pressure with normal temperature indicates pump or leakage failure; high pressure suggests a blocked relief valve.

Fuel quantity: float-type or capacitance sensors; capacitance gauges read incorrectly with changes in fuel dielectric or with water; they are not precise for flight planning.

Fuel flow: turbine or vane flowmeter; used to compute range and detect leaks; a sudden drop or rise in flow with steady power indicates a fault.

Suction gauge: shows vacuum for gyro instruments; low suction degrades gyro accuracy; the gauge itself can fail.

Electrical indications: ammeter/voltmeter show charging status; a discharge with the alternator offline requires load shedding.

Cross-check rule: a single abnormal indication is suspect; two related indications agreeing indicate a real fault.

EFIS: PFD shows attitude, airspeed, altitude, heading and flight director; ND shows heading, track, navaids, weather and TCAS traffic.

EICAS/ECAM: engine parameters and system synoptics; messages are classified as warning (red), caution (amber) and advisory (white/green).

Glass cockpit: solid-state AHRS/IRU and air data computers replace mechanical gyros and pitot-static instruments; redundancy is by multiple ADCs and displays.

Display failure: a failed display shows a red X or blank; reversion modes allow remaining displays to show essential data.

Electronic standby instrument (ESI): self-contained attitude, airspeed and altitude with its own battery and sensors; it is independent of the main system.

AHRS vs IRU: AHRS uses magnetometer and accelerometers for attitude/heading; an IRU uses laser gyros and accelerometers and provides position as well.

Colour conventions: red = warning/limit, amber = caution, green = normal, white = advisory; a red line on a gauge marks the limit.

Data-source failure: a failed ADC or AHRS causes flags (e.g. ATT, HDG, IAS) and the crew must select an alternate source.

Integration caution: glass displays can fail in ways that look valid; cross-check the standby instrument and raw data.

Stall warning: a reed or vane sensor near the leading edge sounds a horn or voice; it must be tested before flight and is inhibited with flaps at high angles on some types.

Overspeed warning: a clacker or aural warning triggered near VNE/VMO; the red line on the ASI marks the limit.

GPWS/EGPWS: modes include excessive descent rate, terrain closure, altitude loss after take-off, unsafe gear and glideslope; EGPWS adds a terrain database and look-ahead.

GPWS alerts: 'SINK RATE', 'PULL UP', 'TERRAIN', 'TOO LOW GEAR'; the correct response is maximum power and wings level climb.

TCAS: traffic advisories (TA) and resolution advisories (RA); an RA requires immediate response, and the pilot must follow it even if it conflicts with ATC.

TCAS II gives vertical RAs; TCAS I gives TAs only. TCAS does not provide terrain warning.

Master caution/warning: a centralised alert; the master warning (red) is for immediate action, master caution (amber) for non-immediate items; press to cancel and check the annunciator.

Alert priorities: warning > caution > advisory; aural warnings may be inhibited in some phases (e.g. gear warning with full flaps).

Alert system checks: pre-flight test buttons verify lamps and aural warnings; a silent test indicates a failed alert system.

Flight director: computes steering commands shown on the PFD; the autopilot follows the same commands when engaged.

Autopilot modes: lateral (HDG, NAV, APR, LOC) and vertical (ALT, VS, IAS, GS); mode annunciation on the PFD shows armed (white) and engaged (green) modes.

Autopilot limitations: maximum engage altitude, minimum speed, and bank limits; it disconnects automatically on excessive bank, stall warning or power loss.

Autopilot disconnect: an aural warning and flashing annunciation; the pilot must take manual control and trim.

Flight director modes: GA (go-around) modes command a climb and wings level; approach mode captures localiser then glideslope.

Autopilot servo failure: the aircraft may deviate or the autopilot may disconnect; monitor the flight path and be ready to disconnect.

Autopilot use in turbulence: it may disconnect or cause altitude deviations; reduce speed and monitor.

Autopilot pre-flight: check the mode annunciations, disconnect test, and that the trim and servos respond correctly.

Autopilot and stall: an autopilot may not recover from a stall; the pilot must disconnect and recover manually.

Pitot-static failure: cross-check with the standby instruments and the GPS altitude; use the alternate static source if fitted.

Blocked pitot: the ASI behaves like an altimeter; use pitch and power and cross-check with GPS ground speed.

Blocked static: the ASI over-reads in climb and under-reads in descent; the altimeter freezes; select alternate static and use GPS altitude.

Gyro failure: a flag or a red X on the display; use the standby instrument and the magnetic compass.

Electrical failure: the standby instrument has its own battery; shed load and land as soon as practicable.

Loss of vacuum: the attitude and heading indicators fail; the turn coordinator may be electric; use the standby instruments.

Alert system failure: a missing aural warning or a failed test indicates a fault; treat the system as inoperative and apply the relevant procedure.

Abnormal engine indications: high CHT, low oil pressure or high oil temperature require reducing power and landing as soon as practicable.

Pilot response priority: aviate, navigate, communicate; identify the fault, apply the checklist and cross-check the indications.