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Author Topic: Approach Clearance from an Airway  (Read 14394 times)
mavericksfan412003
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« on: February 07, 2011, 10:12:42 PM »

Here's the scenario:

Pilot is IFR, en-route to KLEB, and is traveling westbound on V496 to LEB. The MEA along the final airway segment to LEB is 5000'. The pilot is assigned the ILS 18 approach flown from the LEB VOR. The MEA from the feeder route (LEB) to the IAF (BURGR) on this approach is 3900'. ATC's clearance to the pilot is "N12345, cross LEB at or above 3900, cleared ILS runway 18 approach".

As the pilot, I'm thinking that this is not legal, because I've essentially been authorized to descend below the MEA on the airway. ATC's response is that the phrase "at or above" in the approach clearance keeps it legal (as opposed to a "cross LEB at 3900").

If any crossing restriction is given in the approach clearance for whatever reason (not required, because I already have an MEA to comply with on the airway, correct?), I'm thinking it would have to be "cross LEB at (or above) 5000" or higher.

Who's correct here? Thanks guys.
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Jason
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« Reply #1 on: February 08, 2011, 08:46:00 AM »

The approach clearance included a crossing restriction which authorizes you to descend prior to LEB. The MVA is likely lower than the MEA in the area you are talking about. The MEA is no longer applicable since the approach clearance included a lower altitude.

Personally I may wait to descend to 3,900' MSL until reaching LEB outbound since you only have to descend 1,100 feet between LEB outbound and the procedure turn.  With mountainous terrain in the area, I don't have much issue waiting to descend the 1,100 feet on this approach.

Hope this helps.

Jason
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ogogog
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« Reply #2 on: February 08, 2011, 09:08:18 AM »

if you were in radar contact and the controllers mva was 3900 in that area it is a leagle clrn, if you were non radar than it would not be.
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sykocus
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« Reply #3 on: February 08, 2011, 09:47:30 AM »

if you were in radar contact and the controllers mva was 3900 in that area it is a leagle clrn, if you were non radar than it would not be.

Yes, and just to add to that. As it says in from the AIM:

"Because of differences in the areas considered for MVA, and those applied to other minimum altitudes, and the ability to isolate specific obstacles, some MVAs may be lower than the nonradar Minimum En Route Altitudes (MEAs), Minimum Obstruction Clearance Altitudes (MOCAs) or other minimum altitudes depicted on charts for a given location. While being radar vectored, IFR altitude assignments by ATC will be at or above MVA."

The one caveat would be that MVA's do not account for receiving a usable signal from a navaid, but since you were heading over the VOR that was not be a concern.
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Jason
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« Reply #4 on: February 09, 2011, 11:16:27 AM »

Since I've recently given this scenario some more thought, I thought I would expand on my post above.  If a ZBW area B controller (CON 37 sector) happens to be lurking out there, your local knowledge would certainly be appreciated.

The radar coverage at LEB is poor or nil at best until at or above 4,500 - 5000 ft MSL so assuming the MVA is the same or higher than the MEA on V496, the controller would not be able to legally issue the clearance, "cross LEB at or above 3900, cleared ILS runway 18 approach."  I don't have access to the MVA chart for that area off hand, but the validity of this clearance largely has to do with the MVA in the area (and if radar coverage is sufficient).

Now from a pilot's perspective, is there any way to know what the MVA is in a particular sector?  Not really unless you somehow have access to the MVA charts which in flight is a slim chance.  Some rely heavily on ATC to provide terrain and obstacle clearance though most of the time it is our responsibility.  In this case, it would be rather difficult to know off hand that the clearance is or is not valid and thus whether complying with the clearance will provide adequate terrain clearance.  Some quick pre-flight planning with a glance at the sectional chart and surrounding IAPs may lead you to question this clearance after you have some more information about the local terrain.  If in doubt, it never hurts to ask.
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Walters
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« Reply #5 on: February 09, 2011, 12:22:32 PM »

MIA in the LEB area is 4800. should have just been cleared for approach with no altitude or cleared direct leb cross leb at or above 4800
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sykocus
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« Reply #6 on: February 13, 2011, 01:55:56 AM »

Some rely heavily on ATC to provide terrain and obstacle clearance though most of the time it is our responsibility.

If we're talking purely during IFR flying then I don't really agree with you there. As a controller the only time I can think of that I'm not responsible for an IFR aircraft's terrain clearance is if it's cleared for a visual or contact approach, if it's requesting an IFR clearance and has stated it can maintain it's terrain and obstacle clearance or if the pilot choses not to comply with an ODP.

For the visual approach the wx has to be VFR and the pilot needs the field or preceding traffic in sight. A contact approach cannot even solicited by the controller. For an IFR "pop-up" the aircraft is VFR until the pilot accepts responsibility or the controller will withhold the IFR clearance until he climbs VFR to an appropriate altitude. So there's some very specific actions and requirements so that the pilot has to be aware that they taking responsibility. The ODP is really the only without a confirmation or clearance from ATC which would indicate they are taking the responsibility for terrain clearance on their own.
« Last Edit: February 13, 2011, 05:46:15 AM by sykocus » Logged

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Jason
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« Reply #7 on: February 13, 2011, 11:04:01 AM »

If we're talking purely during IFR flying then I don't really agree with you there. As a controller the only time I can think of that I'm not responsible for an IFR aircraft's terrain clearance is if it's cleared for a visual or contact approach, if it's requesting an IFR clearance and has stated it can maintain it's terrain and obstacle clearance or if the pilot choses not to comply with an ODP.

During an IFR departure from an uncontrolled field prior to entering controlled airspace terrain and obstacle clearance is the pilot's responsibility.  You may choose to fly the ODP if one is available but either way the pilot is responsible for not turning early into the side of a mountain or hitting an antenna.  The same situation exists departing IFR from a tower controlled airport where departure instructions include an initial heading to fly or clearance involving a turn (ie. "after departure turn left heading 180" or "after departure turn right on course to ...").  Once terrain and obstacle clearance permits, you can start the turn but it is at pilot's discretion.

It is also the pilot's responsibility when executing an instrument approach procedure since the IAP specifies altitudes which will maintain safe terrain and obstacle clearance.  It's especially important in non-radar environments and approaches into uncontrolled airports where ATC may not have you on radar or have already terminated your radar services and switched you to the advisory frequency.  Pop up IFRs are another good example as you mentioned.

While ATC does often provide terrain and obstacle clearance, I believe it's important to recognize those scenarios in which we as pilots are responsible for not hitting something in the IFR environment.  Perhaps I should revise my statement to say, "Some rely heavily on ATC to provide terrain and obstacle clearance though in some unique cases it is our responsibility."
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sykocus
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« Reply #8 on: February 13, 2011, 12:54:00 PM »


During an IFR departure from an uncontrolled field prior to entering controlled airspace terrain and obstacle clearance is the pilot's responsibility.  

That's a good one I hadn't thought of.

When a pilot is following the ODP or IAP I still consider the onus for terrain/obstacle clearance being off the pilot, other then in the general sense that pilots are always the ones in control of the plane.

Like I said the ODP situation is probably the trickiest for the pilot. If the tower says "after departure fly heading XXX" then it is still the pilot's choice to follow the ODP first or go it on his own. However if he hears "radar contact fly heading XXX" then ATC is responsibly for his terrain separation. It's just two words that make all the difference.
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w0x0f
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« Reply #9 on: February 13, 2011, 04:27:46 PM »

If we're talking purely during IFR flying then I don't really agree with you there. As a controller the only time I can think of that I'm not responsible for an IFR aircraft's terrain clearance is if it's cleared for a visual or contact approach, if it's requesting an IFR clearance and has stated it can maintain it's terrain and obstacle clearance or if the pilot choses not to comply with an ODP.

Tower controllers at locations with MSAW are required to take appropriate actions when receiving low altitude alerts on all aircraft, even those on visual approaches. Approach controllers are required to ensure that tower controllers have received low altitude alerts for any aircraft switched to the tower frequency, even those on visual approaches. So technically, controllers are still responsible to ensure terrain and obstacle clearance for aircraft on visual approaches. 

I have seen aircraft line up for a closed airport and also for a highway on a visual approach at night.  I had to take actions to resolve both of these errors.
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Jason
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« Reply #10 on: February 13, 2011, 04:43:45 PM »

When a pilot is following the ODP or IAP I still consider the onus for terrain/obstacle clearance being off the pilot, other then in the general sense that pilots are always the ones in control of the plane.

I would agree with that statement adding the stipulation that the pilot must be flying the ODP or IAP correctly.  Once cleared for the approach, the pilot is responsible for complying and maintaining the altitudes prescribed in the IAP.  Any deviation from a mandatory altitude could cause a substantial threat for CFIT and thus the pilot would be responsible for terrain and obstacle clearance.  If the pilot correctly flies the procedure, then terrain/obstacle clearance is really on TERPs.

Like I said the ODP situation is probably the trickiest for the pilot. If the tower says "after departure fly heading XXX" then it is still the pilot's choice to follow the ODP first or go it on his own. However if he hears "radar contact fly heading XXX" then ATC is responsibly for his terrain separation. It's just two words that make all the difference.

It's also important to point out the scenario where your departure airport has no published ODP.  That doesn't necessarily mean there is nothing to hit just that no ODP has been published for that airport.  From fields without ODPs I teach my students to evaluate the terrain based on the sectional chart and also to consult the missed approach procedure for the IAPs published for the departure runway.  At a controlled field you would need to specifically request to fly it, but from an uncontrolled field there is no stipulation which prevents you from flying the missed approach procedure for an IAP to the departure runway prior to entering controlled airspace.  It will usually keep you out of trouble too, depending on the terrain and specific area.
« Last Edit: February 13, 2011, 04:48:41 PM by Jason » Logged
sykocus
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« Reply #11 on: February 13, 2011, 10:03:35 PM »


Tower controllers at locations with MSAW are required to take appropriate actions when receiving low altitude alerts on all aircraft, even those on visual approaches. Approach controllers are required to ensure that tower controllers have received low altitude alerts for any aircraft switched to the tower frequency, even those on visual approaches. So technically, controllers are still responsible to ensure terrain and obstacle clearance for aircraft on visual approaches. 

Well it's still the pilot who's responsible for his terrain clearance. He's choosing his descent based on local contions and topography. If he wants to fly 50' over a hill top on his way to a runway he can chose do so. It *is* however always a controller's responsibility to take appropriate action if they observe a potentially dangerous situation. "Just in case" the pilot didn't mean to top the hill at 50'.

« Last Edit: February 14, 2011, 07:16:28 AM by sykocus » Logged

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byoungblood
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« Reply #12 on: March 24, 2011, 09:13:16 PM »

There was no need for a crossing restriction in this clearance anyway. If the pilot is flying an airway that goes to a fix/navaid that is on the approach, or where there is a transition to the approach, the controller does not need to provide any altitude information to the pilot, as they already have it on the charts. As mentioned before, the crossing restriction did not negate the MEA on the airway, as it was an "at or above" restriction that merely implored the pilot to not descend below that altitude until the VOR. Crossing the VOR at the MEA certainly complies with that restriction.

On the other hand, I know some controllers will give a such a crossing restriction regardless of the circumstances out of habit or to CYA. As long as the altitude given is the higher of the MEA, MIA/MVA, or minimum altitude specified on an approach procedure, there's nothing wrong with doing it every time.
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