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This is a follow-up to my previous question here - Lost radio communication after take-off in IMC - what are my options?. Please refer to that to understand the scenario of this question.

If, for e.g, at one point during the flight, I see a minimum en-route of 9000' and so I climb up to 9000' from 8000'. Now, if the next segment has a minimum en-route altitude of 3000', shall I go back to my previously held altitude of 8000' (which became my assigned altitude before and is now the maximum amongst all the other available altitudes) or shall I maintain 9000' and consider it to be my "new" assigned altitude?

Apart from a regulatory perspective, I'd also like if someone could weigh-in on practical perspective - would it be better in terms of traffic separation for ATC, etc.

So the question really is - is it practical to descend, or do the regulations want you to descend and hence ATC does not expect you to descend?

I've had different answers to this particular question from different Flight Instructors, and hence looking for a definite answer.

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    $\begingroup$ You may put you scenario here rather than refer to the previous question. The story seems to be: I take off from untowered aerodrome KSSI, fly IFR (KSSI SSI V441 MONIA GNV OCF V581 DADES KTPA). I was cleared by FSS: Climb and maintain 4000 expect 8000 20 mins after departure. I realize I lost my comms, I squawk 7600. And then explain. Note you need to fly the highest of assigned altitude, expected altitude, and MEA (FAR 91.185). So 8,000 (not 9,000) unless MEA forbids. Also note that ATC will try to talk to you on nearby VOR audio. $\endgroup$
    – mins
    Nov 7, 2015 at 10:21
  • $\begingroup$ It is my understanding you would descend back down to 8000' since that is now the highest altitude. $\endgroup$
    – wbeard52
    Nov 7, 2015 at 14:50
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    $\begingroup$ The regulations are clear on the altitudes to fly so I'm not sure why you think that it might be "practical" to ignore them and do something else? Those regulations exist to make your actions predictable to ATC, so if you do something else then you're going to create some confusion. Unless of course you enter VMC, in which case you can land VFR if you decide it's the most practical option. If you want to give more details of the different opinions you've heard then maybe we can help to clarify them. $\endgroup$
    – Pondlife
    Nov 7, 2015 at 23:14
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    $\begingroup$ Maybe you should add in your question what country you are asking about. Rules can all be different in different countries... $\endgroup$
    – Maverick283
    Nov 8, 2015 at 21:48

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The rules on this are well-established and clear. They are laid out in FAR §91.185(c)(2). In particular, you should fly at an altitude which is (emphasis mine):

At the highest of the following altitudes or flight levels for the route segment being flown:

(i) The altitude or flight level assigned in the last ATC clearance received;

(ii) The minimum altitude (converted, if appropriate, to minimum flight level as prescribed in §91.121(c)) for IFR operations; or

(iii) The altitude or flight level ATC has advised may be expected in a further clearance.

For each segment of your route, you evaluate the minimum, assigned, and expected altitudes, and fly the highest. In this case, you'd fly at 9,000 feet on the leg where the MEA is 9000, and then descend back to 8,000 when the MEA drops to that altitude or lower.

If you lose your radios and squawk 7600 (or stop squawking altogether), ATC will expect you to fly those altitudes. They will provide separation between you and all other IFR traffic at 9,000 feet on the first leg, and 8,000 on the second leg. The only exception to this is if you encounter VFR conditions, in which case you should maintain VFR, land, and call ATC so they stop holding the airspace open for you.

In this situation, you should not worry about inconveniencing ATC or other traffic. We have these rules specifically set up so that nobody trades paint if a radio fails. ATC will manage IFR traffic separation for you. "Better in terms of traffic separation" happens when everybody follows the same plan.

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