Flight Rules

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Aquaplaning / Hydroplaning

Aquaplaning is the phenomenon of a tire skating (not rotating) over the runway surface on a thin film water. It is caused by the buildup of a layer of water beneath the tire, which becomes…


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The Right of Way

With two aircraft converging in the air, which one must give way, and how? When two aircraft are converging, i.e., at a constant relative bearing at the same altitude, the aircraft that has the other…



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Mayday / Panpan

What is a Mayday call, and when is it used? The radiotelephony (RT) spoken word Mayday indicates that an aircraft is threatened by grave and immediate danger and requests immediate assistance. A typical Mayday call…


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What are VASI lights?

Visual approach slope indicator (VASI) lights are a system used to provide slope guidance during the visual stage of the approach. They will assist pilots to maintain a stable descent path down to the runway…


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OCA DA DH MEA MSA

What is OCH(A)? OCH is the obstacle clearance height above the aerodrome level (and so has relevance when using QFE). OCA is the obstacle clearance altitude above mean sea level (and so has relevance when…