Wet Runways, Hydroplaning, Wake Turbulence and Windshear Explained
During the winter an aircraft is parked overnight prior to an early morning departure. The crew notice a slight glistening ice deposit on top of the wings or blades which appears translucent. Under these conditions:
Special Operational Procedures and Hazards: GCAA ATPL Essentials
Under the GCAA Air Law and Operational Procedures syllabus at ATPL level, pilots are expected to understand how operational threats translate into concrete procedures. A key example is runway surface condition. When the Aircraft Flight Manual (AFM) does not provide supplementary wet-runway landing data and reports indicate a wet surface at ETA, aviation regulations require increasing the computed dry-runway landing distance by 15% to maintain safety margins. Hydroplaning (aquaplaning) further shapes procedures: minimum hydroplaning speed in knots is approximately 9 × √(tyre pressure in psi). For a tyre at 10.8 bar (~157 psi), this yields about 113 kt. To mitigate hydroplaning risk, make a positive touchdown in the touchdown zone, promptly deploy spoilers, and apply maximum reverse thrust and braking as runway friction allows. Following a heavy-mass landing on a short runway, monitor brake energy and brake temperature to prevent fade or fuse plug release. Note that viscous hydroplaning is especially likely in the smooth, rubbered touchdown areas near runway ends, even with shallow water films.
Wake turbulence and windshear are recurring operational hazards. Wake intensity is greatest when an aeroplane is heavy and at low airspeed; avoid the flight path of a preceding heavy, especially in light crosswinds that can drift vortices. For a right crosswind, prefer a takeoff path right of and above the preceding aircraft’s track. Microbursts can rapidly shift headwind to tailwind and introduce strong downdrafts; an aircraft encountering a 40 kt headwind on entry to a microburst may face an 80 kt total shear as the wind flips to a 40 kt tailwind. Expect both vertical and horizontal windshear—often first indicated on approach near fixes such as the outer marker on an ILS. A sudden horizontal tailwind gust reduces angle of attack and lift, tending to make the aircraft descend; immediate windshear guidance and power application are critical. With regard to community noise, ICAO PANS-OPS Doc 8168 notes that the most beneficial noise abatement procedure near the airport depends on the wind component; pilots must balance noise mitigation with performance and obstacle clearance requirements.
Hazard reporting and onboard systems knowledge are equally important. The ICAO Bird Strike Information System (IBIS) standardizes the collection and dissemination of bird-strike data to improve risk management around aerodromes. In the realm of security, after an act of unlawful interference, the State where the aircraft lands must promptly notify the State of Registry, the State of the operator, and ICAO; the commander must submit a report to the designated local authority and the Authority in the State of the operator. Regarding aircraft systems, an excessive cabin altitude warning must trigger at approximately 10,000 ft. Firefighting knowledge is tested too: Halon (or equivalent) is suitable for use in the cockpit and cargo compartments, while H2O extinguishers are intended for carbonaceous (Class A) materials and must not be used on energized electrical or flammable liquid fires.
Topics covered in this question bank
- Runway performance on wet surfaces and the mandated 15% landing distance factor when AFM wet data is absent
- Hydroplaning theory (dynamic and viscous), hydroplaning speed calculation, and landing/braking techniques
- Wake turbulence generation, category effects, and avoidance procedures in crosswind conditions
- Windshear and microburst recognition, expected wind changes, and recovery procedures on approach and departure
- Brake energy/temperature management following heavy-mass or short-field operations
- ICAO PANS-OPS noise abatement procedures and the influence of wind components
- Bird-strike reporting via IBIS and related aerodrome hazard mitigation
- Security: reporting requirements after unlawful interference (States to notify and commander’s obligations)
- Aircraft systems: cabin altitude warning thresholds and cockpit/cargo fire-extinguishing agent suitability
- Core ATPL operational procedures aligned with GCAA and ICAO aviation regulations