RNAV Approach & TAA

[RocktheWings]

Quick question, on a IFR flight within the TAA of my destination airport. ATC states "maintain 3000 until established, cleared for RNAV etc". The fact that I was within the TAA, would I be "established" and able to descend to that sectors minimum altitude of say 2500? Or do I need to be on some initial, intermediate, final segment?

Thanks

 

[David Megginson]

Quick question, on a IFR flight within the TAA of my destination airport. ATC states "maintain 3000 until established, cleared for RNAV etc". The fact that I was within the TAA, would I be "established" and able to descend to that sectors minimum altitude of say 2500? Or do I need to be on some initial, intermediate, final segment?

Thanks

Any altitude restriction that ATC gives you overrides MSA (in Canada) or TAA (in the U.S.). In this case, you need to stay at 3,000 until you're actually established on a leg of the approach. I assume they gave you an initial waypoint, e.g. "Cleared to XXXXX for the RNAV 03 Approach into MyAirport", so if XXXXX is a waypoint on the approach, you maintain 3,000 ft to XXXXX, then can descend to the charted altitude for that approach leg.

 

[MauleSkinner]

You can descend. From the AIM:

Altitudes published within the TAA replace the MSA altitude. However, unlike MSA altitudes the TAA altitudes are operationally usable altitudes. These altitudes provide at least 1,000 feet of obstacle clearance, more in mountainous areas. It is important that the pilot knows which area of the TAA the aircraft will enter in order to comply with the minimum altitude requirements. The pilot can determine which area of the TAA the aircraft will enter by determining the magnetic bearing of the aircraft TO the fix labeled IF/IAF. The bearing should then be compared to the published lateral boundary bearings that define the TAA areas. Do not use magnetic bearing to the right-base or left-base IAFs to determine position.

1. An ATC clearance direct to an IAF or to the IF/IAF without an approach clearance does not authorize a pilot to descend to a lower TAA altitude. If a pilot desires a lower altitude without an approach clearance, request the lower TAA altitude from ATC. Pilots not sure of the clearance should confirm their clearance with ATC or request a specific clearance. Pilots entering the TAA with two-way radio communications failure (14 CFR Section 91.185, IFR Operations: Two-way Radio Communications Failure), must maintain the highest altitude prescribed by Section 91.185(c)(2) until arriving at the appropriate IAF.
2. Once cleared for the approach, pilots may descend in the TAA sector to the minimum altitude depicted within the defined area/subdivision, unless instructed otherwise by air traffic control. Pilots should plan their descent within the TAA to permit a normal descent from the IF/IAF to the FAF. In FIG 5-4-5, pilots within the left or right-base areas are expected to maintain a minimum altitude of 6,000 feet until within 17 NM of the associated IAF. After crossing the 17 NM arc, descent is authorized to the lower charted altitudes. Pilots approaching from the northwest are expected to maintain a minimum altitude of 6,000 feet, and when within 22 NM of the IF/IAF, descend to a minimum altitude of 2,000 feet MSL until crossing the IF/IAF.

 

[David Megginson]

You can descend. From the AIM:

Note the "unless otherwise instructed by air traffic control" condition in item 2. In this case, the pilot was instructed to maintain 3,000 ft until established on the approach, so they may not descend until then.

 

[MauleSkinner]

Note the "unless otherwise instructed by air traffic control" condition in item 2. In this case, the pilot was instructed to maintain 3,000 ft until established on the approach, so they may not descend until then.

“Maintain 3000 ft until established” isn’t “otherwise instructed”, it’s part of the approach clearance.

Any altitude restriction that ATC gives you overrides MSA.

keep in mind, the question was about TAA, not MSA.

 

[N1120A]

Until you are established, you don't descend below the ATC instruction. ATC can override altitudes on approaches, both above and below the published altitudes.

 

[RocktheWings]

I think MaulSkinner cleared it up, the question mainly is being within the confines of the TAA is considered being "established". Seems similar to say a feeder route that if I were on that I would be cleared to descend to that minimum altitude. It really wasn't a huge deal today bc we were 5 miles or so outside the IF/IAF and just descended when arriving there. But if were say 29 miles out, would ATC be expecting us to descend since the TAA is part of the approach.

 

[LesGawlik]

If you're within the TAA you're established.

"An aircraft still outside the TAA should receive a clearance like this: “Cleared direct [fix name]. Maintain at or above [altitude] until entering the TAA, cleared RNAV runway one eight approach.”

Absent any altitude restrictions included in that clearance, the pilot should confirm that the airplane is within one of the TAA and descend to the altitude charted for that segment of the TAA. In effect, such a clearance is like the more familiar form “N1234, cross XXX at 3000, cleared ILS runway xx approach."

 

[MauleSkinner]

But if were say 29 miles out, would ATC be expecting us to descend since the TAA is part of the approach.

A TAA is an “at or above” altitude. ATC has cleared the airspace from your altitude down to the TAA floor.

once you report leaving an altitude, they’ll start making it available to others.

 

[David Megginson]

I think MaulSkinner cleared it up, the question mainly is being within the confines of the TAA is considered being "established".

It will be interesting to hear from a controller, but I'm fairly certain that "established" means actually on a leg of the approach, not just within TAA distance (just as, with an older ILS approach, "established" means you're on the LOC track inbound, not just on a vector to intercept it). When the controller says "maintain 3,000 ft until established," that overrides any other altitude, including TAA.

For comparison, note that MSA is also operational in Canada. If I'm cleared for an approach on this side of the border, that implies that I can descend to MSA immediately unless ATC gives me an altitude restriction, just like with TAA in the US.

In both countries, "maintain 3,000 until established" is an altitude restriction overriding any published altitudes, and "established" means on a segment of the approach, not just within 10 miles of it.

 

[MauleSkinner]

It will be interesting to hear from a controller, but I'm fairly certain that "established" means actually on a leg of the approach, not just within TAA distance (just as, with an older ILS approach, "established" means you're on the LOC track inbound, not just on a vector to intercept it). When the controller says "maintain 3,000 ft until established," that overrides any other altitude, including TAA.

For comparison, note that MSA is also operational in Canada. If I'm cleared for an approach on this side of the border, that implies that I can descend to MSA immediately unless ATC gives me an altitude restriction, just like with TAA in the US.

In both countries, "maintain 3,000 until established" is an altitude restriction overriding any published altitudes, and "established" means on a segment of the approach, not just within 10 miles of it.

So you’re saying there’s no difference between a TAA and an MSA other than the name?

 

[David Megginson]

So you’re saying there’s no difference between a TAA and an MSA other than the name?

Here's my understanding (pending clarification from a controller or other expert).

In Canada, MSA is an operational altitude (an approach clearance implies permission to descend to it unless otherwise stated). In the U.S., TAA is operational, while MSA is advisory (for emergency use). ATC can override MSA in Canada or TAA in the U.S. with a specific altitude instruction, as happened in the OP's case.

 

[MauleSkinner]

Here's my understanding (pending clarification from a controller or other expert).

In Canada, MSA is an operational altitude (an approach clearance implies permission to descend to it unless otherwise stated). In the U.S., TAA is operational, while MSA is advisory (for emergency use). ATC can override MSA in Canada or TAA in the U.S. with a specific altitude instruction, as happened in the OP's case.

So the question is whether the TAA counts as "established" or not. If it's not considered "established", it can't be an operational altitude.

if you have to be specifically cleared to that altitude, it’s the same as an MSA in the U.S., and is not an “operational altitude”.

 

[Fracpilot]

Per the Pilot Controller Glossary:

Established: To be stable or fixed on a route, route segment, altitude, heading, etc.

AIM 5-4-6 Approach Clearance

1. Maintain the last altitude assigned by ATC until the aircraft is established on a published segment of a transition route, or approach procedure segment, or other published route, for which a lower altitude is published on the chart. If already on an established route, or approach or arrival segment, you may descend to whatever minimum altitude is listed for that route or segment.

 

[Clip4]

Once you are cleared for the approach and within the published TAA area, you are established and failure to descend may place you at a very disadvantageous altitude to complete a stabilized approach.

 

[David Megginson]

Once you are within the published TAA area, you are established and failure to descend may place you at a very disadvantageous altitude to complete the approach.

It seems strange that simply being within 30 or 10 miles of the start of the approach would count as "established" on the approach, especially if you're not on a published segment or other published route (as specified in the definition @Fracpilot quoted above).

If the controller hadn't given an altitude restriction, the OP could have descended to TAA as soon as cleared for the approach, but the restriction to a higher altitude suggested a need to avoid conflict with other traffic (e.g. an arrival or departure for another airport in the same area).

 

[MauleSkinner]

@David Megginson how do you determine in Canada when you can descend to MSA as an operational altitude? Do they not give you a “maintain xxxx until established” as part of every approach clearance?

 

[David Megginson]

Also, why would the controller have said "maintain 3,000 ft until established…" when the OP was already well within the TAA, if simply being within the TAA distance (rather than actually on a published approach segment) meant "established"? It would have been a pointless restriction.

 

[MauleSkinner]

Also, why would the controller have said "maintain 3,000 ft until established…" when the OP was already well within the TAA, if simply being within the TAA distance (rather than actually on a published approach segment) meant "established"? It would have been a pointless restriction.

Because they’re required to give an “until established” as part of every approach clearance. Doesn’t matter what altitude you’re at, even if you’re on a published segment at the appropriate altitude for that segment.

Dead people determined the need.

 

[Larry in TN]

IPH page 4-60, left column, second paragraph.

 

[Clip4]

Also, why would the controller have said "maintain 3,000 ft until established…" when the OP was already well within the TAA, if simply being within the TAA distance (rather than actually on a published approach segment) meant "established"? It would have been a pointless restriction.

Because the controller has no way to establish you have even loaded the approach and he can’t say dumb ass don’t descend if you haven’t loaded the approach and determined where you are.

 

[tsts4]

IPH page 4-60, left column, second paragraph.

This is the actual para referenced above:
"Once cleared for the approach, pilots may descend in the
TAA sector to the minimum altitude depicted within the
defined area/subdivision, unless instructed otherwise by
air traffic control. Pilots should plan their descent within
the TAA to permit a normal descent from the IF/IAF to the
FAF. "

 

[David Megginson]

This is the actual para referenced above:
"Once cleared for the approach, pilots may descend in the
TAA sector to the minimum altitude depicted within the
defined area/subdivision, unless instructed otherwise by
air traffic control. Pilots should plan their descent within
the TAA to permit a normal descent from the IF/IAF to the
FAF. "

It's the "unless instructed otherwise" part that we're discussing.

If this were an ILS approach, we'd probably all agree that "maintain 3,000 ft until established" means not to descend below 3,000 ft until you're actually on the localiser track, inbound.

Because it's an RNAV approach, however, there's a bit more confusion about what "until established" means — I believe it means that you're actually on a published segment of the approach, not just within 10nm in any random direction, and the excerpt from the controller glossary that @Fracpilot shared seems to support that, but I'm open to more information.

 

[MauleSkinner]

If this were an ILS approach, we'd probably all agree that "maintain 3,000 ft until established" means not to descend below 3,000 ft until you're actually on the localiser track, inbound.

No, we wouldn't. There are often route segments prior to the localizer track that have published altitudes that on which you would be "established".

 

[Clip4]

It seems strange that simply being within 30 or 10 miles of the start of the approach would count as "established" on the approach, especially if you're not on a published segment or other published route (as specified in the definition @Fracpilot quoted above).

If the controller hadn't given an altitude restriction, the OP could have descended to TAA as soon as cleared for the approach, but the restriction to a higher altitude suggested a need to avoid conflict with other traffic (e.g. an arrival or departure for another airport in the same area).

Had traffic been an issue, the controller has other tools such as maintain #### direct to an IAF or to cross the IAF at or above an altitude.

 

[Larry in TN]

It's the "unless instructed otherwise" part that we're discussing.

The point of the TAA is to allow you to descend, often at a constant rate using VNAV.

The "unless instructed otherwise" would be something along the lines of "Maintain 3,000 until [fix], ...".

 

[David Megginson]

No, we wouldn't. There are often route segments prior to the localizer track that have published altitudes that on which you would be "established".

Fair enough, but in this case, the OP didn't mentioned being on any published segment.

 

[David Megginson]

The point of the TAA is to allow you to descend, often at a constant rate using VNAV.

The "unless instructed otherwise" would be something along the lines of "Maintain 3,000 until [fix], ...".

Or maybe "Maintain 3,000 until established"

 

[Larry in TN]

Or maybe "Maintain 3,000 until established"

You might want to look up the definition of a TAA in the P/CG.

 

[MauleSkinner]

Or maybe "Maintain 3,000 until established"

So to clarify your position, in order to use a TAA altitude, it has to be assigned by ATC? What would the OP’s full approach clearance be if he COULD descend to the TAA?

 

[David Megginson]

So to clarify your position, in order to use a TAA altitude, it has to be assigned by ATC? What would the OP’s full approach clearance be if he COULD descend to the TAA?

No, the opposite. My understand would be that TAA altitude applies by default once you have an approach clearance unless ATC gives an altitude restriction with it, just like in the text that you quoted from the AIM.

 

[David Megginson]

You might want to look up the definition of a TAA in the P/CG.

I don't think there's any debate about what a TAA is. @MauleSkinner already quoted text from the AIM stating that once you're cleared for an approach, you can descend to TAA by default unless ATC gives you an altitude restriction. Any altitude restriction would override the TAA. What we're discussing is the limit of the altitude restriction that the OP received "until established". If "until established" means "until you're on a published segment of the approach" (as the controller glossary suggests), then the altitude restriction the OP received is in force until the OP is actually on the approach, probably via a waypoint that they were cleared to directly.

This is exactly how an MSA works in Canada. By default, an approach clearance means that you can descend to MSA unless ATC gives you an altitude restriction.

Here's a non-RNAV example. If ATC says "Fly heading 100 to intercept, cleared for the ILS 07" then I can descend to MSA (in Canada) right away; however, if they say "Fly heading 100 to intercept, cleared for the ILS 07, maintain 3,000 until established" then I can't descend below 3,000 ft until I'm established on the localiser track.

In an RNAV case, it would be clearer to say " Maintain 3,000 until XXXXX" where XXXXX is the initial waypoint you're using to enter the approach, but if they said "Maintain 3,000 until established", I'd still assume they meant that.

 

[RussR]

Because it's an RNAV approach, however, there's a bit more confusion about what "until established" means — I believe it means that you're actually on a published segment of the approach, not just within 10nm in any random direction, and the excerpt from the controller glossary that @Fracpilot shared seems to support that, but I'm open to more information.

You're not within 10nm in "any" random direction, you are specifically between the provided course boundaries of the TAA.

The (U.S.) Pilot Controller Glossary has the following, emphasis mine:

TERMINAL ARRIVAL AREA (TAA)− The TAA is controlled airspace established in conjunction with the Standard or Modified T and I RNAV approach configurations. In the standard TAA, there are three areas: straight-in, left base, and right base. The arc boundaries of the three areas of the TAA are published portions of the approach and allow aircraft to transition from the en route structure direct to the nearest IAF. TAAs will also eliminate or reduce feeder routes, departure extensions, and procedure turns or course reversal.

In the U.S., they are published portions of the approach and the whole intent of the TAA is to allow ATC to clear the aircraft 30 nm out and the pilot can then navigate the rest of the way on their own. The TAA is used in lieu of specific feeder routes and has all the same obstacle clearance requirements as a feeder route.

 

[David Megginson]

You're not within 10nm in "any" random direction, you are specifically between the provided course boundaries of the TAA.

The (U.S.) Pilot Controller Glossary has the following, emphasis mine:

TERMINAL ARRIVAL AREA (TAA)− The TAA is controlled airspace established in conjunction with the Standard or Modified T and I RNAV approach configurations. In the standard TAA, there are three areas: straight-in, left base, and right base. The arc boundaries of the three areas of the TAA are published portions of the approach and allow aircraft to transition from the en route structure direct to the nearest IAF. TAAs will also eliminate or reduce feeder routes, departure extensions, and procedure turns or course reversal.

In the U.S., they are published portions of the approach and the whole intent of the TAA is to allow ATC to clear the aircraft 30 nm out and the pilot can then navigate the rest of the way on their own. The TAA is used in lieu of specific feeder routes and has all the same obstacle clearance requirements as a feeder route.

We have the same thing on our RNAV approach plates, with the different sectors, but they're still labelled "MSA". Interesting, though. So why would a controller say "until established" when the pilot was already established within the TAA? The explanations others have given (that "until established" means until the pilot has loaded the approach into their GPS) are nonsensical, because ATC doesn't concern itself with operational details inside the cockpit. So if your suggestion holds, what do you think the controller meant?

 

[David Megginson]

I'm sure at least one of the people who's posted in this thread is a controller — if so, could you self-identify, and I'll take your explanation as the truth? Everyone else (me and other pilots/instructors) are just laypeople shooting the breeze here.

 

[Clip4]

No, the opposite. My understand would be that TAA altitude applies by default once you have an approach clearance unless ATC gives an altitude restriction with it, just like in the text that you quoted from the AIM.

If you fly IFR or in training, you need a refresher of the procedures and the charts. A lot of what happens in the RNAV world is to allow the pilot to navigate to the approach and descend with minimal ATC interaction. Those rather larger holds and the TAA have the purpose of use for altitude management by the pilot. You got to know the rules to play the game.

 

[Larry in TN]

So why would a controller say "until established" when the pilot was already established within the TAA?

Because it is up to the pilot to determine when he is established, not the controller.

 

[MauleSkinner]

I don't think there's any debate about what a TAA is. @MauleSkinner already quoted text from the AIM stating that once you're cleared for an approach, you can descend to TAA by default unless ATC gives you an altitude restriction. Any altitude restriction would override the TAA. What we're discussing is the limit of the altitude restriction that the OP received "until established". If "until established" means "until you're on a published segment of the approach" (as the controller glossary suggests), then the altitude restriction the OP received is in force until the OP is actually on the approach, probably via a waypoint that they were cleared to directly.

This is exactly how an MSA works in Canada. By default, an approach clearance means that you can descend to MSA unless ATC gives you an altitude restriction.

Here's a non-RNAV example. If ATC says "Fly heading 100 to intercept, cleared for the ILS 07" then I can descend to MSA (in Canada) right away; however, if they say "Fly heading 100 to intercept, cleared for the ILS 07, maintain 3,000 until established" then I can't descend below 3,000 ft until I'm established on the localiser track.

In an RNAV case, it would be clearer to say " Maintain 3,000 until XXXXX" where XXXXX is the initial waypoint you're using to enter the approach, but if they said "Maintain 3,000 until established", I'd still assume they meant that.

Here’s where you’re getting crossed up...in the U.S., they will never give the clearance I highlighted above. It will always include an altitude “until established”, and it will always include the words “until established” regardless of where you are in relation to the approach.

 

[LesGawlik]

When you are in the TAA you are established for the purposes of this discussion.

 

[Craigd31]

Regarding “established “, probably other references that may define it differently, but from the IPH FAA-H-80863-16B, page 4-54...

“For aircraft operating on unpublished routes, an altitude is assigned to maintain until the aircraft is established on a segment of a published route or IAP. (Example: “Maintain 2,000 until established on the final approach course outbound, cleared VOR/DME runway 12.”) The FAA definition of established on course requires the aircraft to be established on the route centerline. ”