Permissible uses of VNAV

IFATC/mod answer please:
With center frequency, which of the following is permissible when away from device, either using VNAV or IFA:

  • Step climbing,
  • Changing odd/even level (when using an oceanic track, turning from east to west, or entering N/S semicircular rule),
  • Climbing/descending 100 ft when entering and leaving China?

Well you cant use VNAV for step climbing at all, it doesn’t allow

  1. Whenever you need to change altitude and you are not descending via a STAR you must request an altitude change. If you are away we will let you descend though at cruise.
  2. If you would like to descend via a STAR, request descent via a STAR or receive clearance to descend via. You will then be able to descend at your discretion and will not need altitude assignments since it’s a published procedure.
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We won’t strictly enforce odd/even altitudes but to ensure separation we may assign them. We will not be using China RVSM rules, no.

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So no more FL351 in China?

You can do that so long as you’re not flying with Center. ATC can’t issue you FL351. They can issue you FL350. We don’t have the option to give 100ft increments.

Keep in mind, ATC can tell you to maintain an altitude if needed as Center’s primary function is to provide aircraft separation. ATC does have a set of strict separation guidelines that need to be followed. That can be found here.

Flying at FL351 only provides 900ft separation with an aircraft that would be flying at FL360.


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