Any display pilot who strays outside his allotted box during flight demonstrations this week is best advised to plead guilty immediately.

Protestations of innocence will be met with evidence from a source that is difficult to contradict - the 1m (3ft)-accurate radar normally used by France's national flight test centre for pinpoint tracking of manoeuvring aircraft.

The Thomson Adour mobile trajectory-radar is the key tool used to ensure that pilots remain in the designated area and to provide grounds for a warning - or worse - if they do not. Its high sampling rate means that an aircraft is tracked effectively for every second of its flight.

Show director Gilles Fournier says the system, known here as Sampam, is so important that flying may not take place without it, and two examples have been brought in from France's Centre d'Essais en Vol (CEV) to ensure that the eventuality is unlikely to arise.

Fournier notes that the permitted area at Le Bourget is "very strict" for safety, environmental and air traffic control reasons.

The zone varies according to the aircraft type, but in general Runway 03/21 marks the eastern boundary, and flight is not allowed below 500ft over the town of Dugny to the south-west, or above limits of 3,000ft or 5,000ft. The boundary with Paris Charles de Gaulle airspace is known as the "Roissy wall".

"If a pilot flies at 450ft over Dugny then the radar will tell you and you print out the trajectory and you can show the pilot that at a precise time he was 50ft too low," says Fournier. "Where it is below the limit it is printed in red."

The system has been used since last Wednesday to check pilots' displays during rehearsal and will also be used in real time during the show. Offenders are warned over small infractions and ultimately can be suspended or banned. Potentially a display could be immediately halted by the flight director, although that has never happened.

Fournier says: "During the last three shows only one pilot had the maximum sanction, which is suspension of flying the next day or the next two days because of the Roissy wall.

"Normally if a pilot is only 50ft low then he has a warning and maybe a second warning. We stress to pilots that Le Bourget is not a competition, it is a presentation of aircraft."

Ultimate arbiter is show director Stephane Pichene, codename Jupiter, an experienced air force text pilot who consults with four other "wise" test pilots before taking action. "But it is very rare," says Fournier.

Source: Flight Daily News