Demo: BPL/H

First, the valves of the gas containers must be closed to stop the gas supply and prevent the fire from spreading. Using extinguishers, making a call, or leaving the area is only effective after stopping the gas.

The correct answer is 'Altitude 9500 ft MSL' because the NOTAM specifies the altitude in feet above mean sea level (MSL). The other options are incorrect as they refer to meters, flight level, or height above ground, which do not apply here.

For cross-border flights, filing a flight plan is required so authorities are informed. The other options are not generally mandatory or relate to different situations.

The correct symbol for a general spot elevation according to ICAO is symbol C. This symbol shows a small number with a dot below it. The other symbols represent different map features and not spot elevations.

QFE is the barometric pressure at a reference datum, typically the runway threshold. The other options refer to sea level pressure, altitude above 1013.25 hPa, or magnetic bearing, which do not define QFE.

The altimeter subscale is used to reference the altimeter reading to a specific pressure level, such as mean sea level, aerodrome level, or standard pressure (1013.25 hPa). The other options are incorrect because the subscale does not adjust for temperature or system errors.

If the subscale is set to a higher than actual pressure, the altimeter shows too high. The aircraft is closer to the ground than indicated. The other answers confuse the effect or describe the opposite situation.

A lower-than-standard temperature causes the altimeter to indicate too high. This is because denser air makes the altimeter overread. The other options are incorrect: they either state the opposite, suggest perfect correction, or confuse with Pitot tube issues, which do not affect the altimeter.

True altitude is an altitude above mean sea level corrected for non-standard temperature and QNH. This gives the actual height above sea level. The other options refer only to ground level, pressure, or temperature, which is incorrect.

Altitude measurement is based on static pressure, which decreases as altitude increases. Total, dynamic, and differential pressures are used for other instruments like the airspeed indicator, not the altimeter.

Correct: The vertical speed indicator measures the rate of change of static pressure by comparing current static pressure with that inside a reservoir. The other options are incorrect: they mention total pressure, vacuum, or acceleration, which are not how the instrument works.

The vertical speed indicator measures the difference between the present static pressure and the static pressure of a previous moment. This shows climb or descent rate. The other options are incorrect because they refer to dynamic or total pressure, which are not used by the VSI.

Static pressure is the pressure of undisturbed airflow, meaning the ambient air pressure unaffected by movement. Cabin pressure is unrelated. Pressure from orderly flow is dynamic pressure. The pitot tube measures total, not just static, pressure.

With the altimeter set to QFE, it shows height above the airfield. The other options are incorrect: they refer to elevation above sea level, pressure altitude, or the airfield's elevation, not the height above the airfield.

A too big equalizing tank causes the vertical speed indicator to show too high values, as the larger volume amplifies pressure changes. The other options are wrong: the instrument still works, is not overloaded, and does not show too low values.

Correct: The VSI measures the difference between instantaneous static pressure and previous static pressure, indicating vertical speed. The other options mention total or dynamic pressure, which are not used by the VSI.

The thermometer works by the resistance or semiconductor principle: the electrical resistance changes with temperature. Bernoulli, Boyle, and Venturi principles relate to fluid or gas behavior, not temperature measurement.

The yellow arc on an envelope thermometer indicates the cautious area, where special attention is needed. It does not improve readability, is not the normal operating area, and does not show maximum permissible values.

The correct answer is: when the sensor battery is almost empty. A low battery can cause incorrect readings. Lack of visibility, receiving radio messages, or high envelope temperature do not directly affect the readout.

Correct: To prevent damage on the liquid take off tube. If transported lying down, the tube inside the cylinder can bend or break. The other answers are incorrect: gas can escape even upright, cleanliness is not the main issue, and regulations exist because of the risk to the tube.

The fuel gas from the liquid phase is pushed through the liquid take off tube to the evaporator, where it is converted to gas. The other components (controller, pressure relief device, fill level indicator) are not involved in this phase or have different functions.

The control valve is at the burner because it regulates the gas flow for heating. The envelope equator, upper envelope part, and main cylinder are not involved in controlling the gas supply in a balloon.

The sounding pipe valve indicates the volumetric filling limit, showing how full the container can be. The other options are incorrect: it does not prevent air entry, is not for venting, and does not equalize pressure at altitude.

The envelope of a hot-air balloon is made of synthetic fabric because it is lightweight, strong, and heat-resistant. Silk, cotton, and linen fabrics are too heavy or not heat-resistant enough, so they are not used.

The suspension cords of a hot-air balloon are made from stainless steel because it is strong, durable, and resistant to corrosion. Manila rope, duralum, and copper are either not strong enough or can corrode, making them unsuitable.