Obstacles and unserviceable areas

Make an obstacle conspicuous

Colour, markers, flags and lights have different applications.

Day marking

Fixed or mobile objects requiring marking may use conspicuous colour patterns, markers or flags as appropriate. Orange/white or red/white contrasting bands or chequered patterns are used according to the object’s geometry. If colour is impracticable, markers or flags provide conspicuity; wires and cables can use conspicuous spherical markers at the prescribed spacing.

Flags are conspicuous and positioned to identify the object’s extent; they do not make a wire safe to overfly without clearance. Mobile objects on the movement area have the specified marking and lighting, with emergency vehicles distinguished as required. The published obstacle data remains necessary even when marking is visible.

Obstacle lights

Low-intensity obstacle lights are generally steady red for fixed objects; mobile-object lights use the prescribed flashing colours. Medium-intensity systems include flashing white or red and steady red types; high-intensity systems are flashing white. The selected type depends on height, location and background conditions. Lights identify the top and, for tall or extensive structures, intermediate levels and extent as specified.

Aircraft navigation and anti-collision lights follow Annex 2/SERA; they are not the same as obstacle lights on a mast. A blinking red light alone does not identify the complete height or lateral extent of an obstacle.

Closed is different from non-load-bearing

An apparent paved surface may be unusable for normal aircraft movement.

Closure and shoulders

Closed runway or taxiway portions carry crosses of the prescribed colour: white for a runway and yellow for a taxiway. A temporarily closed area can use the applicable alternative physical closure/warning arrangement. Unserviceability lights are fixed red and mark the hazardous area as required; do not infer an open route through a gap in cones.

Non-load-bearing shoulders alongside a taxiway, apron or holding bay are identified with conspicuous boundary/shoulder markings, often yellow hatching as prescribed. Pre-threshold pavement unsuitable for normal use is marked with yellow chevrons. This is different from a displaced-threshold area still declared usable for some operations.

Make the movement decision

Cross-check the current NOTAM, aerodrome chart, sign, marking and clearance. A closure overrides an old chart depiction of available pavement. A taxi clearance does not certify every shoulder as capable of supporting the aircraft.

The model lets the learner switch between a closed runway, a displaced threshold and an unusable blast pad. The same physical-looking extension produces different declared uses depending on the marking and publication.

Can you apply the rules?

Four original questions. Choose from the facts, then review the explanation.