Joined: 11 Dec 2005
|Posted: Sat Nov 26, 2016 6:53 am Post subject: Altimeter Setting Procedure
|Altimeter Setting Procedure
Avoiding Level Busts
Setting QNH when cleared to an Altitude and setting Standard when cleared to a Flight Level is something for which many of us have been campaigning over more than 25 years. This was a topic at Bluecoat 1999 in Toulouse, when it was highlighted by presentation by Debbie Westley of the UK ATC Altitude/Level Bust Team. I am sad that the message still hasn't yet got through to some.
In my firm view, Tim Atkinson, Dan Cabral and Donald Gray have it exactly right. The procedure they describe, plus associated R/T discipline, is essential to avoid a repeat of a near disaster over London in the 1960s.
This really is the only reliable way to cope with the low Transition Levels / Altitudes that still exist in Europe and elsewhere, whether we like it or not, combined with low or high baro settings - altimeters set to 977 hPa / 28.85in or 1050hPa / 30.03in are 1,000ft from 1013 / 29.92 / Standard setting.
A reminder of the near disaster: A 707 and a VC10 were in an LHR holding pattern below the Transition Level, with the QNH close to 977hPa /28.85in and theoretically separated by 1000ft vertically - I think at 3000 and 4000ft. Unfortunately the aircraft cleared to 4000ft had not set QNH so was at FL40 - the same "true" altitude as the aircraft at 3000ft. The aircraft very nearly collided - the miss distance was given as 100ft, from memory.
This concentrated the minds of European aviators, and I think brought in the procedure always to set QNH when cleared to an altitude on descent. If asked for a passing level, ATC procedures allowed the aircraft to give this as the altitude QNH.
During my 7 years with Airbus, training/checking crews from many backgrounds, the only time I can remember seeing a crew fail to set QNH, was one who waited until passing the Transition Level - and forgot.
A Common Transition Altitude
A Flight Deck Perspective: An evaluation of the impact on flight crew workload, flight deck procedures and safety implications of utilizing a common transition altitude.