Saturday, September 17, 2011

Sector Altitudes?

Question: What action should be taken when a pilot is "cleared for approach" while being radar vectored on an unpublished route?

Answer: Remain at last assigned altitude until established on a published route segment.

In Canada, cleared to the approach I would be able to, and probably would get into an untenable position later on the approach if I didn't, immediately descend to the 100 nm or 25 nm safe altitude published on the plate, as appropriate, in preparation for intersecting a published route segment. I would tell ATC I was "leaving one fife tousand for one zero tousand tree hundred" or whatever the sector altitude was, but I'm not sure I'd be required to do that. Saying it helps me remember it, and allows ATC to know what to expect.

I remember being told by a flight instructor long ago that in the US you were not allowed to descend immediately on being cleared for the approach, and commenters here told me that yes you were, but with this question I may have finally found the case that the original flight instructor was considering. It looks like if I'm on an airway or a published transition to an approach, cleared for the approach clears me to the MEA for that route, but if I'm off airway just being vectored towards the airport, I can't descend to a published safe altitude until directed? I suspect this is more because US airspace have more published transitions and routes and less just hammering around through the clag towards the NDB at the airport.


Frank Ch. Eigler said...

The bible, ATC 7110.65 Order, gives on section 4-8-1, the instructions about how ATC is to issue approach clearances to off-route aircraft. An altitude needs to be assigned until a specified point.

Colin said...

In general, I think that U.S. controllers are probably more controlling than those in the rest of the world. At least in my limited experience flying U.S. and Canadian airspaces.

So in the U.S. I have always been told the altitude to descend to prior to being established on the approach, and this has always been lower than the 100nm or 25nm altitude on the plate.

My CFII said the 25nm altitude was something I would never use unless I had lost communications.

Except in one instance in the wilds of New Hampshire I have always been vectored around to a low enough altitude that I didn't have to do any depicted procedure turn. When I say they are controlling I meant they practically hold your hand (at least with small GA pilots) all the way to the ground.

(That one time in New Hampshire I realized my mistak a little late and wound up diving through a clouds a little high on airspeed. Classic recipe for CFIT, but I had the moving map, terrain highlighting and all of that.)

As far as I understand it from the controller side, there are Letters of Agreement and all sorts of directives (gates to each approach) which dictate what they are to do with each plane. So there's no just delivering a flight into the airspace that includes the approach and wishing them godspeed.

jimmbbo said...

The MSA within 25 NM provides terrain clearance only for use in an emergency/lost situation... The controller should provide an altitude to maintain until on a published portion of the approach procedure, or an airway.

Anonymous said...

@ several commenters: Flying IFR into uncontrolled airports, without radar coverage in many parts of Canada, can often produce a "you're cleared for an approach, call XYZ radio to advise intentions..." This can come while many miles back at higher altitudes - descent pilot discretion, so that's where 100 and 25 nm sector altitudes can come in handy. just FYI..

david said...

That's an important point: in Canada, MSA is operational (like procedure-turn altitude or MDA), while in the US, it's just advisory. As Aviatrix hints, if you ask a controller for an altitude after being cleared for a non-Radar approach in Canada, she'll wonder if you actually have an approach plate.

Aviatrix said...

I learn more about the US system from hearing commenters explain our system for their benefit than I do from the Americans trying to explain theirs to me. As fish, they can't describe the water.

I had been trying to imagine how the 25 nm safe altitude could possibly be for emergencies only!

Sarah said...

The flight instructor long ago who told you you were not allowed to descend immediately on being cleared for the approach with radar vectors was correct. Because of this accident, US ATC always adds the words "cleared for the X approach, maintain Y until established". If they're vectoring you onto a localizer instead of to an IAF they'll add "on the localizer".

If you're on a feeder route ( or enter an RNAV TAA sector ) and "cleared for the approach" without an altitude restriction, you can descend to the MEA or TAA sector altitude.

The MSA being "operational" is an interesting difference in US/Canadian practice. Related: CA/US SID/STAR differences

IANAinstructor - anyone please correct me if I've misstated anything above.

Helicopter Schools said...


More controlling are you serious? I can see that you've only flown in the US and Canada..

Cedarglen said...

We'd sure like you to return to regular postings. Is it gonna happen? -Craig