Definitions — Page 20, Lesson 29

I want to walk you through the definitions that anchor the whole of Air Law. These are the exact, legally binding meanings you'll be tested on, so I'll take them in the order they appear. Let's start with Flight Visibility. This is the visibility forward from the cockpit of an aircraft in flight. Notice the precision: it's specifically forward from the cockpit, not all around. That's the legal definition you must know. Next, Free Balloon — a balloon which, when in flight, is not attached to the surface by any form of restraining device. So if it's tethered, it's not a free balloon. Then we have Free Controlled Flight. This is a specific type of balloon flight. It means flight during which the balloon is not attached to the surface by any restraining device — other than a tether not exceeding 5 metres in length, which may be used as part of the take-off procedure. And during that flight, the height of the balloon must be controllable by means of a device attached to the balloon, operated either by the commander of the balloon or by remote control. So the key elements are: no restraining device except that short take-off tether, and height control by a device on the balloon. Ground Visibility is the visibility at an aerodrome, as reported by an accredited observer. Note the contrast with flight visibility — this one is on the ground at an aerodrome, and it's a reported value. Government Aerodrome means any aerodrome in the United Kingdom which is in the occupation of any Government Department or visiting force. So it's about who occupies it — a government department or a visiting force. Heading is the direction in which the longitudinal axis of an aircraft is pointed, usually expressed in degrees from North — and that North can be true, magnetic, compass, or grid. So heading is where the nose is pointing, measured from one of those four references. Heavier Than Air Aircraft — any aircraft deriving its lift in flight chiefly from aerodynamic forces. That's the defining characteristic: lift from aerodynamic forces. Height is the vertical distance of a level, a point, or an object considered as a point, measured from a specified datum. So it's always relative to a chosen reference point. Now we move into the instrument-related definitions. IFR is the symbol used to designate the instrument flight rules. IFR Flight is a flight conducted in accordance with those instrument flight rules. IMC is the symbol for instrument meteorological conditions. Instrument Approach Procedure is a longer one. It's a series of predetermined manoeuvres by reference to flight instruments, with specified protection from obstacles, from the initial approach fix — or, where applicable, from the beginning of a defined arrival route — to a point from which a landing can be completed. And thereafter, if a landing is not completed, to a position at which holding or en route clearance criteria apply. So it defines the whole protected path from the initial approach fix down to landing, and beyond if you have to go around. Instrument Flight Time is time during which a pilot is piloting an aircraft solely by reference to instruments and without external reference points. The key word is solely — no outside visual references at all. Instrument Ground Time is time during which a pilot is practising, on the ground, simulated instrument flight in a synthetic flight trainer approved by the Licensing Authority. So it's ground-based practice in an approved trainer. Instrument Meteorological Conditions are meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling, less than the minima specified for visual meteorological conditions. So IMC is defined by being below VMC minima, measured in those three terms: visibility, distance from cloud, and ceiling. There's also a note here: in a control zone, a VFR flight may proceed under instrument meteorological conditions if and as authorized by air traffic control. Instrument Time is simply instrument flight time or instrument ground time — the sum of both. Finally, the institutional definitions. JAA means the Joint Aviation Authorities, an associated body of the European Civil Aviation Conference. And JAR means a joint aviation requirement of the JAA bearing that number as it has effect under the Technical Harmonization Regulation — and a reference to a numbered JAR is a reference to such a requirement. So the pattern to hold onto: these definitions are precise legal instruments. Every qualifier matters — forward from the cockpit, solely by reference to instruments, not exceeding 5 metres. That precision is what makes them examinable, and it's exactly how you should read them.