NATCAONLINE

This paper could be subtitled 'The Controllers' View of Runway Safety', because the controllers' ability to physically see the runway is a critical issue in this matter. No matter what sophisticated systems or aids the controller or the pilot may have the controller's ability to see the runway is a basic requirement - when all else fails the Mk. 1 eyeball is the final vital link in the safety chain.

In a recent survey of runway incursion incidents in the US, in 89% of the cases weather was not a contributing factor. We can all understand that in low visibility conditions pilots and drivers can get disorientated and the controller cannot visually monitor the manoeuvring area. But in 9 out of 10 cases this was not the situation and the controller should have been able to see what was happening.

Industry has provided some assistance to the controller - surface movement radar tracks aircraft and vehicles around the airport. The most recent models incorporate various runway intrusion prediction facilities or runway traffic conflict systems, but these only provide very short notice alerts at best.

There are also several aircraft cockpit systems undergoing evaluation that provide the pilot with a moving map display of the airport or a virtual image of the aircraft's location in respect of taxiways and runways.

When such systems are certified and become standard equipment on modern aircraft, unfortunately runway safety incidents will still occur. One only has to look at the number of accidents that are classified as 'controlled flight into terrain', even after many years of GPWS and now, Enhanced GPWS operation.

No matter what modern facilities are available, the Mk 1 eyeball still has a lot of advantages:

The controller can see when an aircraft or vehicle intrudes on to a runway.
The controller can see when a pilot or driver takes a wrong taxiway and is 'unsure of their location' thereby risking an unintentional blunder on to a runway.
The controller can see when an aircraft is not aligned on the correct runway.

Therefore it is regrettable to see that in many of the new control towers the prime function of the structure, a place for the visual control room, has scant priority in the design criteria.

With airports getting larger, inevitably control towers are getting taller in an attempt to provide the best overall view of the airport. Unfortunately this means that the control tower must be located a long way from the runway for it not to be an obstruction.

Therefore even before the first stone is laid and concrete poured, the controllers are limited to a distant view of the runway.

In an ideal world the controller would have an unobstructed view of the manoeuvring area from the control tower. However, similar to the book, 'Women are from Venus, Men are from Mars', there should be a book, 'Controllers are from Saturn and control tower architects are from Uranus'. When left to their own devices, architects love to fill control towers with columns and frame every window with wide stanchions and oversized pillars.

There are many control towers around the world where it is impossible to see all of the critical runway areas from the control position. It is a basic requirement to simultaneously visually monitor the approach area, runway holding position, touchdown area and rapid exit area without having to resort to gymnastics at the control position - it is all too easy to 'loose' a 747 behind a control tower window frame, an inappropriately placed hangar, or bulky terminal building.

The situation is frequently exacerbated at night when the glare from poorly positioned apron floodlighting masks the controller's view in vital directions.

Only a few years ago in the USA the controllers refused to work in a new replacement control tower because of the restricted view caused by the thick window frames and console design. The staff eventually moved into the new tower after major modification work to resolve their concerns.

What can be done to alleviate these problems?

In the modern world, extra manpower means more money out of the budget - and nowadays nobody has money to spare. Instead at Paris Charles De Gaulle and Amsterdam Schipol as these airports have expanded and built new distant runways they have built second control towers, providing the controllers with a close vantage point to clearly view the new runways.

There are a few airports imaginative control tower designs located in strategic positions with frameless windows giving controllers practically an uninterrupted view of the entire airport.

Tallest and biggest does not always mean the best!

Standard Phraseology

In every analysis or report on a runway incursion a significant contributing factor, if not the primary factor of the incident, will be communication.

The primary link between the pilot and the controller remains the R/T - since the relegation of the Morse code to the museum, the primary means of communication has been R/T and will remain so for the foreseeable future.

Everyone knows that each radio transmission must be clear, concise and unambiguous; therefore it is essential that standard phraseology be used. You only have to listen in to a busy tower frequency to hear an endless stream of instructions from a single controller with a high workload and congested frequency, this again highlight the need for everyone to always use standard phraseology.

Unfortunately sometimes there are many different versions of 'standard phraseology' - consider the following:

'Taxi to holding position.'
'Taxi to holding point'
'Taxi runway _ _'
'Hold short'
'Hold position'
'Taxi into position and