Demo: PPL/H

A flashing green light means return for landing, but actual landing clearance will be given later with a steady green. The other answers are incorrect: they either indicate immediate clearance, unsafe airport, or just circling, which is not correct.

A steady green light to an aircraft in flight means 'Cleared to land'. This signal authorizes landing. The other options are incorrect as they refer to waiting, returning, or not landing, which is not the case here.

A flashing red light on the ground means the aircraft must immediately taxi clear of the runway in use. The other answers are incorrect: they refer to take-off clearance, returning to starting point, or general taxi clearance, which do not apply here.

The landing direction indicator is in the shape of a 'T'. The 'T' shows the direction for landing. The other shapes, such as 'L', a straight arrow, or an angled arrow, are not used as landing direction indicators.

The signal square is used to display ground symbols that visually inform overflying aircraft about the aerodrome's conditions. The other options describe functions unrelated to the signal square's actual purpose.

The correct answer is White, as ICAO Annex 14 states that all runway markings must be white. Yellow, Blue, and Green are used for other markings like taxiways or special areas, not for runways.

Longitudinal stripes across the runway mark the threshold. You must not touch down before them. The other options are incorrect as they refer to different markings or functions.

"06L" and "06R" are correct, as parallel runways use the same number with L (left) and R (right). The other options are incorrect because they use different numbers or non-standard designators like "-2".

Correct: A rotating beacon installed at an airport to indicate its location to pilots from the air. The other options are incorrect because they refer to pilots on the ground, a fixed beacon, or a beacon at the final approach, which is not the purpose of an aerodrome beacon.

Correct: From this intersection the available runway length is 2500 m in the stated direction. The sign indicates the remaining usable runway from this point. The other options refer to total length or distance to other points, which is incorrect.

The correct answer is 'Prohibition on landing for a longer period.' The yellow cross on red means no landings are allowed for an extended time. The other options are incorrect as they refer to caution, ground movement, or turn directions, which do not apply here.

The sign means that glider flying is in progress at the aerodrome. The other options are incorrect: it does not mean caution, a landing prohibition, or that only right turns are allowed after take-off and before landing.

DETRESFA means distress phase, which is declared when there is immediate danger to people or aircraft. Alerting phase and uncertainty phase are lower levels, and rescue phase is not an official term.

Rocking the wings is the international signal to confirm understanding of a search and rescue signal during the day. The other actions are not recognized signals and could be misinterpreted.

The correct order is: Incident, Serious incident, Accident. These are the official categories. The other options use incorrect terms or the wrong sequence, which do not match the standard classification.

You must not fly below bridges or similar buildings under any circumstances, as this is prohibited for safety and legal reasons. The other answers are incorrect because they allow exceptions that are not permitted.

Most aviation accidents are caused by human error, as mistakes in judgment, communication, or actions are the leading factors. Technical failure, geographical, or meteorological influences are less often the main cause.

The 'swiss cheese model' explains the error chain. It shows how several small errors or weaknesses can align and lead to an accident. The other answers are incorrect because the model does not describe pilot readiness, emergency landing procedures, or optimal problem solving.

At 6,000 ft, air still contains about 21% oxygen. The percentage stays nearly constant up to about 10,000 m; only the total pressure drops. 12%, 78%, and 18.9% are incorrect—78% is nitrogen, the others are too low.

At about 18,000 ft, atmospheric pressure is roughly half the standard sea level value. At 5,000 ft and 10,000 ft, pressure is still much higher. At 22,000 ft, pressure is already less than half.

The correct answer is 1%. Air is about 78% nitrogen, 21% oxygen, and around 1% other gases. 0.1% is too low, 21% and 78% are the shares of oxygen and nitrogen, not other gases.

Carbon monoxide poisoning can be caused by smoking, as burning tobacco produces carbon monoxide. Alcohol, unhealthy food, and little sleep do not cause carbon monoxide poisoning.

Cracks in the heat exchanger can let exhaust gases with carbon monoxide enter the cabin air. Pitot icing, generator failure, and fuel or hydraulic fluids do not cause carbon monoxide poisoning.

Cyanosis (bluish skin discoloration) is NOT a symptom of hyperventilation; it occurs with lack of oxygen. Tingling, spasm, and disturbance of consciousness are typical for hyperventilation due to changes in blood CO2 levels.

Blue discolouration of lips and fingernails indicates hypoxia, as lack of oxygen causes cyanosis. Muscle cramps, blue marks, or joint pain are not typical signs of hypoxia.