DGCA Air Regulations: Airworthiness of Aircraft Questions

Correct answer: C. Is modified or repaired otherwise than in accordance with the provisions of the rules

A Certificate of Airworthiness CofA) guarantees the aircraft is built and maintained to approved standards. If someone modifies or repairs the aircraft in a way that does NOT follow the approved rules and procedures, the CofA is automatically suspended — because the aircraft is no longer in its certified, airworthy condition. Being in an accident does not automatically suspend the CofA; it is the non-compliant modifications that do.

Correct answer: B. 25/25

FDR Flight Data Recorder) and CVR Cockpit Voice Recorder) — the black boxes — must retain data for a minimum duration. For large aircraft over 27,000 kg) certified from January 2022 onward, ICAO requires BOTH the FDR AND the CVR to retain at least 25 hours of recorded data. So the answer is 25 hours for FDR / 25 hours for CVR = 25/25. Older rules only required 2 hours for CVR, but the new standard is 25/25 for improved accident investigation.

Correct answer: C. Laws of the state of registry

Every aircraft has a Certificate of Airworthiness CofA) that proves it is safe to fly. According to ICAO Annex 8, this certificate is issued by and remains valid under the laws of the STATE OF REGISTRY — the country where the aircraft is officially registered. For example, an Indian-registered aircraft VT-XXX) has its CofA governed by Indian DGCA rules, regardless of where it flies. The state that registers the aircraft is responsible for its airworthiness.

Correct answer: B. Increasing RPM, mass and radial displacement of mass

Gyroscopic rigidity is improved by three factors: 1. Higher RPM — spin faster = more rigid. 2. Greater mass — heavier rotor = more rigid. 3. Greater radial displacement of mass — mass at the RIM rather than the centre = more angular momentum = more rigid. All three together give maximum rigidity. This is why gyro rotors are designed as heavy rings spinning at very high RPM.

Correct answer: B. All of the above

A DGI suffers from ALL four types of errors: 1. Transport wander — as the aircraft moves over the curved Earth, the gyro appears to drift relative to the ground. 2. Earth rate — the Earth's rotation causes apparent drift. 3. Heading errors when banking/pitching — gimbal limitations cause errors during manoeuvres. 4. Mechanical imperfections — bearing friction causes real wander. All four apply!

Correct answer: C. More accurate, electrical pick off coils

A servo altimeter is MORE ACCURATE than a conventional aneroid altimeter. Instead of the aneroid capsule mechanically driving the needles directly, the servo altimeter uses ELECTRICAL PICK-OFF COILS to detect tiny movements of the capsule and drive the display electrically through a servo motor. Removing mechanical linkages dramatically reduces friction, backlash, and hysteresis errors.

Correct answer: C. V S1 to V NO

The GREEN ARC on an ASI shows the normal operating speed range — from VS1 stall speed in clean configuration) at the bottom to VNO maximum structural cruising speed) at the top. Green arc = safe normal operations. Yellow arc caution range) runs from VNO to VNE. White arc flap operating range) runs from VSO to VFE.

Correct answer: A. The horizontal plane

In gyroscope terminology, DRIFT specifically refers to the unwanted movement of the gyro spin axis in the HORIZONTAL plane — meaning the gyro slowly rotates around a vertical axis when it should stay fixed. This is why Directional Gyro Indicators need to be reset periodically. TOPPLE refers to wander in the vertical plane. Drift = horizontal wander, Topple = vertical wander.

Correct answer: C. i) vacuum or a very low pressure) ii) static pressure

An altimeter works by comparing two pressures. The ANEROID CAPSULE is sealed and contains a near-vacuum — almost no pressure. The CASING surrounding it is connected to the static port and filled with the current static pressure. As you climb and static pressure d rops, the sealed vacuum capsule expands, moving a mechanical linkage that drives the altitude display. Vacuum inside, static outside.

Correct answer: C. Time passed at a given altitude.

Hysteresis error in an altimeter is caused by mechanical lag in the aneroid capsule material. After being compressed or expanded, the metal takes time to fully respond and settle. This error varies with how long the aircraft has been sitting at a particular altitude. It is most significant during rapid climbs or descents followed by levelling off. Time at altitude = main factor.

Correct answer: C. Bank right nose up.

A classic artificial horizon has gyroscopic rigidity but is affected by precession errors during sustained turns. After a 270° turn, gyro precession causes the horizon bar to show: Bank right and nose up. This is a well-known instrument error in conventional gyro horizons during prolonged turns.

Correct answer: A. 1,2,3,4

The key gyroscopic properties are: 1. Mass — heavier rotor = more stable. 2. Rigidity in space — a spinning gyro keeps its axis pointing in the same direction in space. 3. Inertia — resistance to change of motion. 4. Precession — force applied causes reaction 90° later in direction of rotation. Option 5 is WRONG — rigidity is in space, not with reference to Earth. So 1, 2, 3, 4 are correct.