Aerodrome Characteristics

The actual standards that the aerodrome should comply with are contained in Advisory Circular AC139-7 Aerodrome standards and requirements, aeroplanes at or below 5700 kg MCTOW. This advisory circular specifies the standards for those aerodromes intended to be used for both daylight operations and night-time operations.

Daylight Non-instrument (VFR) Operations

As shown in Figure 1, each runway should be contained symmetrically within a runway strip. The width of this strip should be either 30 metres, or 2.5 times the wingspan of the largest aircraft intended to use the facility, whichever is the greatest.

The typical wingspan for single-engine aircraft of 5700 kg MCTOW or less is approximately 12 metres, and this would indicate that a strip width of 30 metres would be suitable for most aircraft. For twin-engine aircraft, the wingspan can be as great as 16 metres, so a width of 40 metres would be required. The surface of the strip is usually grass and should be clear of any obstructions such as ditches or fence-posts, and be of sufficient strength so as not to cause structural damage to an aircraft inadvertently running off the runway.

Figure 1: VFR Aerodrome Requirements
Figure 1

The width of the runway portion should be a minimum of 2 times the width of the undercarriage. The average width of undercarriage for these aircraft is approximately 4 to 5 metres, and therefore a runway width of 10 metres would be adequate. While there should be a portion of strip on either side of the runway, the runway may be the same length as the strip. The surface of the runway is also usually grass, and should be clear of any irregularities and strong enough to adequately support the ground movement and landing loads of the aircraft it is intended to serve.

Instrument or Night-time Operations

For aerodromes intended to be used as an instrument runway or for night operations, the specifications are slightly different. As shown in Figure 2, each runway should again be contained symmetrically within a runway strip, but this strip should now be a minimum of 60 metres wide for daytime instrument operations, or 90 metres for night-time operations. The surface of the strip is usually grass and should be clear of any obstructions such as ditches or fence posts, and be of sufficient strength so as not to cause structural damage to an aircraft inadvertently running off the runway.

Figure 2
IFR Daytime Aerodrome Requirements
Figure 2
IFR Night-time Aerodrome Requirements
Figure 2

The width of the runway portion should be a minimum of 18 metres for runways less than 800 metres in length, or 23 metres for other runways. The strip should extend beyond each end of the runway for a distance of 10 metres for runways less than 800 metres in length, and 30 metres for other runways. The surface of these runways is usually grass but some may be sealed. Again it should be clear of any irregularities, and strong enough to adequately support the ground movement and landing loads of the aircraft it is intended to serve.

Visual Aids

Runway Markers

Runway portion defined by mowing

 

Where the extent of the runway is not clearly indicated by the difference in appearance of the surface with the surrounding ground, and the strip is not suitable for the movement of aircraft, then the edge of the runway should be marked. The type of marking used should be both lightweight and frangible and sufficiently low to allow clearance for propellers. The placing of white painted concrete strips flush with the ground at intervals along the runway edge has been found to be acceptable.

Marker boards used to define strip edges

Strip Markers

The extent of the strip should also be identified. A standard post and wire fence is acceptable along the edges of the strip but should not continue across the ends as this would be considered to be an obstacle. Also used are white painted marker boards and tyres.

Windsocks

For day VFR runways at least one windsock should be provided and located, if possible, at a distance of at least 20 metres from the runway centreline. For night or instrument runways less than 800 metres in length, a single windsock should be provided at least 40 metres from the runway centreline. For night or instrument runways greater than 800 metres in length, a windsock should be provided on the left hand side of each end of the runway, located 40 metres from the centreline. For night operations, at least one windsock should be lit.

Lighting

For information on aerodrome lighting for night-time operations, see:

AC139-7 Aerodrome design, aeroplanes at or below 5700 kg MCTOW

Approach / Take-off 'Surfaces'

Approach and take-off airspace 'surfaces' rise upwards and outwards from each end of the strip. For daylight operations only, this surface rises upwards from the end of the strip at a gradient of 1 in 20, and the sides of this surface splay outwards at an angle of 1 in 20. This surface continues to rise until it reaches a distance of 1200 metres from the end of the strip.

For night or instrument operations, the surfaces rise at a gradient of 1 in 40 for a distance of 3000 metres, and the sides splay outwards at an angle of 1 in 10. There should be no trees, buildings or other obstacles that protrude through these surfaces. Figure 3 below provides a diagram of the surfaces.

Figure 3
Approach and take-off surface for day operations
Figure 3
Approach and take-off surface for instrument or night operations
Figure 3

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