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QNH and Transition Level
sydpilot
Topic Author
sydpilot created the topic: QNH and Transition Level
Hi,
This may sound like a silly question with an obvious answer but I still need clarification.
With reference to QNH, Transition Altitude, Transition Layer and Transition Level, the Transition Altitude is always 10,000 feet AMSL for all QNH values and at all times. The thickness of the Transition Layer however will change depending on the QNH.
The AIP lists the flight levels not available when the QNH is lower than 1013 but what happens when the QNH is higher than 1013?
For example, on a day when the QNH is 1028 and the transition layer is 1450 feet thick, will the lowest flight level available be 11450 or 11500? Or will it still be 11000 with a transition layer of 1450 feet?
bobtait replied the topic: QNH and Transition Level
The purpose of the transition layer is to ensure that all aircraft operating on QNH are always separated from aircraft operating on 1013 by at least 1000 feet. If the QNH is greater than 1013, the transition layer will be greater than 1000 feet even when the higher aircraft is cruising at FL110. So the requirement for the lowest flight level to be at least 1000 feet above the transition altitude is met - even at FL110.
If the QNH is higher than 1013, FL 110 will always be available.
