DGCA CPL Tech Specific flashcards

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

Four-stroke cycle order

Induction, compression, combustion (power), exhaust. The crankshaft turns twice per complete cycle, so each cylinder produces one power stroke every two revolutions of the engine.

Detonation versus pre-ignition

Detonation is explosive uncontrolled combustion after normal ignition, raising CHT. Pre-ignition is ignition before the spark. Both are countered by richer mixture, lower power and cooler plugs.

Best power mixture ratio

Approximately 12:1 air-to-fuel by mass, richer than the chemically correct 15:1. Best economy is near 16:1, and exhaust gas temperature peaks close to the stoichiometric ratio.

Constant-speed propeller governor

A governor with flyweights and a speeder spring controls blade angle to hold the selected RPM. If RPM rises above the setting, blade angle increases to absorb more power.

Semi-monocoque structure

The stressed skin carries shear and tension while stringers and frames stabilise it and carry bending loads. This gives a light, strong airframe used in most modern light aircraft.

Aircraft DC system voltage

Light aircraft use 14 V DC systems with a 12 V battery, or 28 V DC systems with a 24 V battery. The alternator output is rectified and regulated to charge the battery.

Density altitude formula

Density altitude equals pressure altitude plus 120 times the difference between outside air temperature and ISA temperature at that level. Higher density altitude reduces performance and lengthens take-off runs.

Crosswind component formula

Crosswind equals wind speed multiplied by the sine of the angle between wind direction and runway. Headwind equals wind speed multiplied by the cosine of the same angle.

Centre of gravity formula

CG equals the sum of moments divided by the sum of weights, where each moment is weight multiplied by its arm from the datum. Loading aft of the aft limit reduces longitudinal stability.

Stall speed with load factor

Stall speed increases with the square root of load factor: Vs(n) = Vs × √n. A 60-degree bank gives load factor 2, so stall speed rises by about 41 percent.

Climb gradient calculation

Climb gradient in percent equals rate of climb in feet per minute multiplied by 100, divided by ground speed in feet per minute. It depends on excess thrust, not on excess power.

Maximum range speed

Range is greatest at the speed for minimum fuel flow per nautical mile, roughly 1.32 times best-endurance speed for a piston aircraft. Endurance peaks at minimum fuel flow per hour.

Effect of weight on take-off

Ground roll varies roughly with the square of weight. A 10 percent increase in weight raises the ground roll by about 21 percent and also reduces climb gradient.

Blocked pitot with open static

The airspeed indicator then behaves like an altimeter: climbing causes the trapped pitot pressure to exceed falling static pressure, so indicated airspeed increases as altitude rises.

Altimeter pressure conversion

Near sea level, 1 hectopascal equals about 27 feet and 1 inch of mercury equals about 1,000 feet. Flying from high to low pressure without resetting reads higher than actual altitude.

Standard-rate turn

A standard-rate turn is 3 degrees per second, giving 180 degrees in one minute and 360 degrees in two minutes. It is marked on the turn coordinator and used for timed turns.

True airspeed approximation

True airspeed approximately equals indicated airspeed multiplied by 1 plus 0.02 times altitude in thousands of feet. The precise relation uses density ratio: TAS = IAS divided by √σ.

Magnetic compass acceleration error

In the northern hemisphere, acceleration causes the compass to turn north and deceleration to turn south. The error is greatest on east or west headings and zero on north or south.

Gyroscope rigidity and precession

Rigidity in space keeps a spinning gyro axis fixed relative to inertial space. Precession is the apparent tilt caused by an applied force, exploited in rate instruments such as the turn coordinator.

Great circle versus rhumb line

A great circle is the shortest path between two points. A rhumb line maintains constant track and appears straight on a Mercator chart, but it is longer than the great circle.

Latitude and longitude distance

One minute of latitude equals one nautical mile, or 1,852 metres. One minute of longitude equals one nautical mile multiplied by the cosine of the latitude.

Variation east is least

When converting true to magnetic, subtract easterly variation and add westerly variation. The mnemonic is variation east, magnetic least; variation west, magnetic best.

ADF relative bearing

The ADF needle points to the station relative to aircraft heading. Relative bearing plus heading equals the magnetic bearing to the station, used to track or home to an NDB.

VOR TO/FROM indication

A centred course deviation indicator with a FROM flag means the aircraft is on the selected radial. With a TO flag it means the aircraft is on the reciprocal of the selected course.

Three-degree glide path

A 3-degree ILS glide path descends about 300 feet per nautical mile, giving roughly 700 feet per minute at 140 knots ground speed. Marker beacons mark outer, middle and inner positions.

One-in-sixty rule

A track error of one nautical mile over 60 nautical miles flown equals 1 degree of drift. It quickly estimates heading corrections for diversions and intercepts without a computer.

VHF airband frequency range

Civil VHF airband covers 118.000 to 136.975 MHz with 25 or 8.33 kilohertz channel spacing. The emergency frequency is 121.5 MHz, with 243.0 MHz used by military UHF.

Transponder emergency codes

Squawk 7700 for a general emergency, 7600 for radio failure and 7500 for unlawful interference. Mode C additionally transmits pressure altitude to the ground radar.

MAYDAY versus PAN-PAN

MAYDAY, spoken three times, signals distress and immediate danger. PAN-PAN, spoken three times, signals urgency without immediate danger. Both are followed by callsign, position and intentions.

Radio failure in visual conditions

Continue under visual flight rules, land at the nearest suitable aerodrome and report arrival to air traffic control. Squawk 7600 and remain clear of controlled airspace unless cleared.

VHF line-of-sight range

VHF range in nautical miles approximates 1.23 times the square root of antenna height in feet. Raising altitude therefore extends communication range because the horizon moves further away.

Mandatory readback items

Pilots must read back clearances, runway assignments, altimeter settings, headings, altitudes, frequencies and transponder codes. Readback confirms the clearance was received and understood correctly.