Altimeter Subscale Setting Procedures
I had a hand in writing the Flight Operations Department Communication (FODCOM) 2/97 which contained what we thought was very clear advice to the operators of public transport/commercial air transport operations on altimeter subscale setting procedures, and was closely involved in the research that the UK CAA undertook to find out what could be the causes of altitude/level busts.
Within this FODCOM, which can be accessed through the CAA website (www.caa.co.uk/docs/33/FOD199702), the topic of, 'When to set Standard (1013/29.92)' received special attention.
As it was evident that many pilots failed to set 'Standard' when the rules required the subscale setting to be changed 'on reaching Transition Altitude' due to distraction, failure to remember what it was, etc, the requirements changed to what appears in the UK AIP today. It was also evident that not setting Standard until passing TA on occasions when the pressure was low simply invited high performance aeroplanes to zoom through their cleared level before the adjustment could be completed and cross-checked.
The only procedure to be followed is that specified by the operator. For the pilots of UK-registered aircraft this should be along the lines of, 'Immediately after being cleared to climb to a flight level, set and cross-check that 'Standard' is set, then commence the climb.' The only exception to this rule is where State regulations require that this adjustment is made close to the TA, such as in the USA, where the TA is relatively high. It is ususal for many operators to require that the third altimeter remains on QNH until the aircraft has passed above either the TA or the Minimum Safe Altitude, whichever is the higher, so that there is a means of rapidly knowing altitude if the need arises.
Last edited by Nugget90; 12th Jul 2002 at 08:27.