Aviation history shows that taxiing has always been a dangerous phase of any flight, but it is still the Cinderella among safety subjects

The worst accident in aviation history was caused by a crew thinking they had take-off clearance when they did not. That was at the old Tenerife airport on the Canary Islands on 27 March 1977, and 583 people were killed.

It is worth revisiting this disaster to appreciate how little aviation has learned about runway safety since then. Tenerife was uncommonly busy because a bomb had exploded in Las Palmas airport's terminal and many aircraft had been diverted. A KLM Boeing 747 was backtracking along runway 12 for a 180° turn at the end ready for take-off. Meanwhile, a Pan American World Airways 747 was also cleared to backtrack along 12 about 3min behind KLM, but to leave the runway at the third exit and report clear. Meanwhile, the KLM crew reported ready for take-off and were given their departure clearance. The KLM crew read back the departure clearance and then, in a famously ambiguous message, reported: "We are now at take-off," and released the brakes to roll. Tenerife tower replied: "OK, stand by for take-off, I will call you," but this message was obscured by Pan Am's simultaneous transmission: "No, we're still taxiing down the runway." The KLM 747 hurtled down the foggy runway and collided with the Pan Am aircraft.

This tragic event contained most of the airport manoeuvring area errors that Eurocontrol, from early analysis of its new central incident reporting system, confirms are still the most common mistakes pilots and controllers make. The top risk is still pilots taking off without clearance. Second is lining up on the runway for take-off without clearance.

Most other events occur because the pilot is uncertain of his position on the airfield, says Eurocontrol. The classic recent example was the October 2001 Scandinavian Airlines Boeing MD-87 runway collision with a Cessna Citation CJ2 at Milan Linate airport, Italy in which 122 people died. This event also occurred in limited visibility, so the tower depended upon position reports from the pilots. The Citation pilot was cleared to leave the business aircraft apron by a taxiway that did not cross the active runway, but took the wrong one which did cross it, and that was the fatal difference. The long-awaited report is also likely to fault radio telephony (R/T) discipline on the part of the pilot and ATC. Linate's delay in installing a long-planned surface-movement surveillance and control system will be mentioned, but while its existence might have prevented this accident, the system's absence did not cause it - human factors did. Any part that might have been played by non-standard or unclear manoeuvring-area surface markings and airport signage is secret until the report is published.

At Paris Charles de Gaulle airport on 25 May 2000 the co-pilot of a Streamline Aviation Shorts 330 freighter was killed when the wingtip of an Air Libert‚ Boeing MD-83 that had been cleared for its take-off cut into the cockpit as the 330 was entering the active runway. The MD-83 pilot abandoned take-off. The controller thought the 330 was following the MD-83 to the same holding point, but the Shorts was preparing to start its take-off on the same runway from a taxiway intersection 1,000m (3,280ft) along it. Visibility was poor, but to exacerbate the situation, the controller was talking to Air Libert‚ in French and to Streamline in English. The Streamline pilots did not understand French.

Paul Wilson, Eurocontrol's head of airport operations, highlights language problems: "ICAO standard phraseology for instructing a pilot to hold short of the runway is 'taxi to holding position', but in the USA they use a similar instruction 'taxi into position and hold' to mean line up on the runway and wait. Both expressions have the same key words 'position' and 'hold', but they mean crucially different things. The result is that, several times, American pilots abroad have heard 'taxi to holding position' and interpreted it as an instruction to line up on the runway and wait."

As part of its European Action Plan for the Prevention of Runway Incursions, Eurocontrol has released a CD with all the common hazards illustrated on it. It includes ATC language, procedures, airport layout hazards, signage and surface markings, seen from the points of view of pilots, controllers and vehicle drivers, and of the airlines and airports that employ them. In these days of ever more congested and complex airports, anyone who wants to be shocked out of their complacency should try the CD quizzes before checking the illustrated information sections. Evidence shows people don't realise how little they know - or perhaps how much they have forgotten - about this Cinderella subject. Unless they find out, another Tenerife is just a matter of time.

Source: Flight International