A2 CofC - Drone Certificate of Competency Meteorological Considerations Questions and Answers — Questions and Answers
Question 1: On a hot and humid summer day in the UK, a remote pilot notices their UAS requires more throttle to hover and has a reduced flight time compared to a cool, dry day. What is the primary meteorological cause for this decrease in performance?
- The higher air pressure increases the overall drag on the airframe.
- The humidity can interfere with the radio control signal strength.
- The lower air density provides less lift for the propellers. (Correct answer)
- The onboard electronics are more likely to overheat in the warm air.
Correct answer: The lower air density provides less lift for the propellers.
Hot, humid air is less dense than cool, dry air. This condition is often referred to as a high-density altitude. Propellers generate lift by moving through the air, and in less dense air, they must spin faster or at a greater pitch to produce the same amount of lift, consuming more power and reducing flight time and overall performance.
Question 2: A remote pilot is planning to operate a 1.5kg UAS near a group of tall office buildings on a day with a steady 15-knot wind. Which of the following meteorological phenomena presents the most significant and unpredictable danger to the flight?
- Anabatic wind flowing uphill.
- Advection fog forming over the area.
- Katabatic wind flowing downhill at night.
- Mechanical turbulence from wind interacting with the buildings. (Correct answer)
Correct answer: Mechanical turbulence from wind interacting with the buildings.
Mechanical turbulence is created when wind flows over and around obstacles, such as buildings. This creates powerful, unpredictable eddies, downdraughts, and updraughts in the immediate vicinity of the structures, which can easily overwhelm a small UAS and lead to a loss of control. The other options are large-scale weather phenomena and are less relevant to this specific, localised scenario.
Question 3: You are reviewing a Terminal Aerodrome Forecast (TAF) for a nearby airport to plan a flight for later today. The forecast includes the code 'TEMPO 1417 3000 SHRA'. What should you interpret from this information?
- A permanent improvement in visibility to 3000m is expected between 14:00 and 17:00 UTC.
- There is a 30% probability of rain showers between 14:00 and 17:00 UTC.
- Temporarily, between 14:00 and 17:00 UTC, there will be periods of rain showers and visibility reduced to 3000 metres. (Correct answer)
- The wind will temporarily shift to 300 degrees with heavy rain after 14:17 UTC.
Correct answer: Temporarily, between 14:00 and 17:00 UTC, there will be periods of rain showers and visibility reduced to 3000 metres.
In a TAF, 'TEMPO' indicates temporary fluctuations in weather conditions expected for less than an hour at a time. '1417' specifies the time window (from 14:00 to 17:00 UTC). '3000' is the visibility in metres, and 'SHRA' stands for rain showers. Therefore, the code predicts temporary periods of rain showers with visibility dropping to 3000 metres during that three-hour window.
Question 4: Under UK drone regulations, maintaining Visual Line of Sight (VLOS) is mandatory for all Open Category operations. Which of the following weather conditions would most directly make a flight non-compliant with this rule?
- A surface wind of 20 knots.
- An ambient temperature of -2°C.
- Fog that reduces flight visibility to less than the planned operating distance. (Correct answer)
- A broken cloud layer at 800 feet above ground level.
Correct answer: Fog that reduces flight visibility to less than the planned operating distance.
Visual Line of Sight (VLOS) requires the remote pilot to be able to see the drone and its orientation without aid at all times to avoid collisions. If fog reduces visibility to a point where the pilot can no longer see the aircraft, they cannot maintain VLOS, making the flight illegal. Strong winds and cold temperatures affect performance, and a cloud base at 800ft is not an issue for flights conducted below 400ft, but a lack of visibility directly breaches the VLOS rule.
Question 5: On a humid day with the ambient air temperature at +1°C, a remote pilot notices a sudden, unexplained loss of performance and increased vibration from their UAS. What is the most likely meteorological cause?
- Propeller icing. (Correct answer)
- Sudden battery voltage drop due to the cold.
- Water ingress into the motors.
- Loss of GPS signal due to atmospheric moisture.
Correct answer: Propeller icing.
Even when the ambient temperature is slightly above freezing, air accelerating over the leading edge of a propeller blade can cause a significant temperature drop (the Venturi effect). In humid conditions, this can cause moisture to freeze onto the blades, forming ice. This ice disrupts the aerofoil's shape, leading to a loss of lift, imbalance, and severe vibration.
Question 6: Which of the following describes the most significant risk when flying a UAS in light, steady rain, even if the aircraft is rated as water-resistant?
- The water can refract radio signals, causing a loss of control link.
- The aircraft's colour may become difficult to see against a grey sky.
- Water droplets on camera lenses will obscure the video feed.
- Reduced propeller efficiency due to water on the blades. (Correct answer)
Correct answer: Reduced propeller efficiency due to water on the blades.
While all are potential issues, the most significant direct risk to flight performance is the effect of water on the propellers. Water droplets accumulate on the blades, disrupting the smooth airflow over the aerofoil. This reduces their aerodynamic efficiency, meaning the motors must work harder to generate the same lift, which significantly increases power consumption and reduces flight time.
A2 CofC - Drone Certificate of Competency Meteorological Considerations Questions and Answers
On a hot and humid summer day in the UK, a remote pilot notices their UAS requires more throttle to hover and has a reduced flight time compared to a cool, dry day.
What is the primary meteorological cause for this decrease in performance?