Brunei DCA CPL(A) Instrumentation flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Standard sea-level pressure

The standard atmosphere uses 1013.25 hPa (29.92 inHg) and 15 °C at mean sea level, with a temperature lapse rate of about 1.98 °C per 1000 ft.

Dynamic pressure formula

Dynamic pressure equals one half times air density times true airspeed squared. The airspeed indicator responds to this dynamic pressure, so density changes alter the indicated speed.

Rigidity in space

A spinning gyroscope resists any change to the direction of its spin axis. This property gives attitude and heading instruments a stable reference in space.

Precession rule

When a force is applied to a spinning gyro, the spin axis moves in a direction 90 degrees ahead in the direction of rotation. This explains drift and turn errors.

Blocked pitot with open static

If the pitot tube blocks, the airspeed indicator receives trapped pressure plus changing static pressure. In a climb it under-reads, in a descent it over-reads, acting like an altimeter.

Blocked static port

With the static port blocked, the airspeed indicator over-reads in a climb and under-reads in a descent, the altimeter freezes, and the vertical speed indicator reads zero after a transient.

Altimeter subscale error

An incorrect pressure setting causes an altimeter error of about 30 ft per hectopascal at low level. Setting QNE instead of QNH gives flight level rather than altitude.

Cold temperature altimeter error

In air colder than standard, the altimeter over-reads and the true altitude is lower than indicated. Apply cold-temperature corrections when operating in sub-zero conditions.

Vertical speed indicator lag

The vertical speed indicator uses a calibrated leak to delay case pressure, so it lags several seconds behind actual climb or descent. A stuck instrument reads zero.

Attitude indicator erection

Pendulous vanes or an accelerometer keep the attitude indicator's spin axis vertical. During acceleration the horizon bar falsely shows a climb, which is an acceleration error.

Heading indicator drift

The heading indicator is a free gyro with no magnetic reference, so it drifts from friction and earth's rotation. It must be reset to the magnetic compass periodically.

Turn coordinator design

The turn coordinator uses a rate gyro with its spin axis tilted about 30 degrees, so it senses both yaw and roll rate. The ball shows slip or skid.

Standard rate of turn

A standard rate turn is 3 degrees per second, completing 360 degrees in two minutes. The turn coordinator is calibrated to show this rate at normal airspeeds.

Slip and skid

The ball in the turn coordinator moves to the outside of the turn during a skid and to the inside during a slip. The pilot steps on the ball to correct.

Magnetic variation and deviation

Variation is the angle between true and magnetic north. Deviation is the error caused by the aircraft's own magnetic fields, recorded on the compass swing card.

Compass turning error

The magnetic compass under-reads when turning through north and over-reads when turning through south. The error is largest on north and south headings and increases with latitude.

ANDS rule

ANDS means Accelerate North, Decelerate South. On east or west headings, acceleration causes a false turn indication toward north and deceleration toward south.

Compass dip

The compass senses only the horizontal component of the earth's magnetic field. Magnetic dip increases with latitude and causes the turning and acceleration errors.

Manifold pressure gauge

The manifold pressure gauge shows absolute pressure in the induction system in inches of mercury. At a given RPM it indicates engine power and is read with the tachometer.

Fuel quantity sensors

Float-type or capacitance sensors measure fuel quantity. Capacitance gauges are affected by fuel dielectric changes and water, so they are imprecise for flight planning.

Suction gauge

The suction gauge shows the vacuum supplied to the gyro instruments. Low suction degrades gyro accuracy, so the gauge is checked before flight and in the air.

EFIS primary display

The primary flight display shows attitude, airspeed, altitude, heading and flight director. The navigation display shows track, navaids, weather and traffic.

EICAS and ECAM

EICAS and ECAM display engine parameters and system synoptics. Messages are classified as warning in red, caution in amber, and advisory in white or green.

Electronic standby instrument

The electronic standby instrument is a self-contained unit with its own battery, providing attitude, airspeed and altitude independent of the main air data and attitude systems.

GPWS modes

Ground proximity warning modes include excessive descent rate, terrain closure, altitude loss after take-off, unsafe gear and glideslope. EGPWS adds a terrain database and look-ahead.

TCAS resolution advisory

A TCAS resolution advisory requires immediate manoeuvring and takes priority over ATC instructions. TCAS II gives vertical RAs; TCAS I gives traffic advisories only.

Master caution and warning

The master warning is red and calls for immediate action. The master caution is amber for non-immediate items. Press to cancel and read the annunciator.

Autopilot mode annunciation

Autopilot modes are shown on the PFD: armed modes in white and engaged modes in green. Lateral modes include heading, navigation and approach; vertical modes include altitude, vertical speed and glideslope.

Autopilot disconnect

An autopilot disconnect gives an aural warning and a flashing annunciation. The pilot must take manual control, trim the aircraft, and monitor the flight path.

Flight director function

The flight director computes steering commands and displays them on the PFD. The autopilot follows the same commands when engaged, so both share the same modes.

Alternate static source

If the static port blocks, selecting the alternate static source restores static pressure to the instruments, though it may introduce a small position error.

Loss of vacuum response

A vacuum failure disables the attitude and heading indicators. The pilot should use the standby instrument, the magnetic compass and the electric turn coordinator, and land as soon as practicable.