INFO AT A GLANCE:
200mL translucent Sistema, off to the east of the track (see hint), below the communications station north of the trig, a bit of a walk.
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| You will be able to see an slightly unaligned runway in the distance. |
Final Approach
Atop the actual Colonial Knob (which is ironically higher than the location the trig is sited) sits the Colonial Knob Communications Station, which handles and relays communications between the ground and the air, and vice versa – and is one of the few communications stations in the North Island, with another notable station sited at Mount Egmont. This means a plane is in touch with ground controllers constantly as it is passed between the relay stations.
Colonial Knob Communications Station also checks with the Hawkins Hill radar and the Mt Robertson radar in the South Island to assist in the radar control of aircraft.
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| Colonial Knob Communications Station. |
When a plane is 100 miles from Wellington airport, it will appear on screen there and the plane can then be tracked all the way to the airport. Wellington airport (IATA: WLG, ICAO: NZWN) has only one runway, 16/34, which measures in at 2,081 metres, a very short distance for how many aircraft movements and passengers are recorded annually, the terrain is challenging, and the weather can make the approach dangerous at times (for when it was Rongotai Airport back in 1947, the then-grass runway was often unusable during winter months, and was subsequently shut down).
All these factors require vigilance on the part of both ground controllers and flight crew, and therefore multiple checks and measures have been introduced, along with network of stations which has been set up.
Wellington employs radar in two main forms – surveillance radar and precision approach radar.Surveillance radar enables the operator (radar director) to observe and control all aircraft within about 100 miles of Wellington. An aircraft wishing to land at Wellington may be taken over at a certain point (between 6 and 10 miles from Wellington) by precision approach radar which enables the radar director to watch the aircraft so closely that he can “talk it down” virtually to the runway threshold; the final landing is made by the pilot who can then see the runway and, if it is at night, the runway lighting.
Just north of here is the Titahi Bay NDB (non-directional beacon) which is a radio transmitter used as a navaid (navigational aid) for aircraft in the ‘TY’ holding pattern which flies over Titahi Bay and Mana Island, and planes making their way down the Ngauranga Valley flight path. It transmits two letters (TY) through morse code on a frequency of 234 KHz. Once a plane has acquired the signal, the pilots can now very accurately know where they are relative to other points. And they can then fly at 159° directly to Wellington Airport, assuming they aren’t placed in the holding pattern.
There are very strict speed requirements put in affect by Wellington ATC (Air Traffic Control). Arriving aircraft must not exceed 250kts IAS (indicated air speed – which differs from the true speed) below 10,000ft within 30 nautical miles of the airport, and on final approach, aircraft must fly an instrument approach (rather than visual) at a maximum of 170kts IAS at 8 nautical miles, and then a minimum of 160kts IAS at 5 nautical miles.
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| Looking north towards Kapiti from Colonial Knob |
The cache
At the cache site, a sign is attached to the building fence perimeter, which reads “Airways New Zealand, Colonial Knob Communications Station, Critical to aircraft flight safety”. The towers visible just north of here are used for commercial radio and cellular, and are not part of the NDB, which is not visible from here. What you can see however, is spectacular views of Wellington Airport, the Colonial Knob Trig, Ohariu Valley, Tawa, Mana Island, Titahi Bay, Plimmerton, Paraparaumu, Kapiti Island, and the Tararua’s. If your keen-eyed, you may be able to spot the Brother’s Islands of the Marlborough Sounds coast, and the three islands between Kapiti Island and the Mainland. If the day is very clear, haze-free, and the conditions are right, you might even be able to see Mount Egmont.
The cache is a 200mL snaplock Sistema which when placed had a logbook, geocaching notice, pencil, and a prize for the FTF. Remember to replace it well.
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| Final approach on Runway 34 |