The procedures described in use at CDG Paris DO go wrong, despite earlier posts to the contrary. The US doesn’t use Conditional Clearances per se, but they do use multiple landing clearances – they also go wrong, regularly. UK use “Land After” at some aerodromes (probably more if they didn’t have so many problems), whilst good old Oz, and many others, continue to use outdated ICAO Conditional Clearances, and how they go wrong.
All these capacity enhancing procedures have had the band aid treatment applied over years, as the “experts” (yes, we all know the definition) try to play catch up with aircraft performance and traffic counts. The bottom line is that like everything else in aviation, there is always a down side when we compromise our standards. Safety is, and should always remain the driver. Capacity must come a clear second. The bean counters will tell us that “we agree” whilst pressuring us to keep the numbers up. The spreadsheet in the tower lift showing the performance figures (rate of landings/take offs) ensuring that (not so) subtle pressure is continuously applied. Oh for the gold watch when we retire – yeh, and look out the tooth fairy doesn’t fly in and grab it!
How many more examples are required before it is seen that the days of these type of capacity enhancement techniques are long gone, and there is an urgent need to allow the pilot to fly the airplane, and the controller to do just that. New types require more and more head down time minimising the opportunity to look out the window, sum up the situation, listen to the RT and stay on the ball. Language, cultures, rapid RTF, wide body airplanes with high body angles and so it goes on, continuously reduces the effectiveness of these antiquated procedures.
The top dozen or so aerodromes throughout the world (US) do not use conditional clearances – ATC make the decision and use that rare (become rarer) form of control, called judgement. Ask the guys in Paris how the use of this procedure worked for them. Ask the Sydney guys what a Metro looks like lining up in front of a departing jet at night. Do a little surfing to find untold many more examples, especially at night or in poor viz. Build in a couple of intersection departures, an occasional runway crossing, and multiple line ups, and see how complex it can become. Just hope that it’s not you in the cab, cockpit or cabin when it all turns to ….
Come on guys – put the responsibility for control back where it belongs, and throw away the band-aid box.