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Good day for GPWS

Old 01-24-2018, 06:57 PM
  #21  
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Originally Posted by JohnBurke View Post
Your sentence is not very clear, however, according to the article under discussion:

"A Skywest Canadair CRJ-900 on behalf of Delta Airlines, registration N162PQ performing flight OO-3567/DL-3567 from Salt Lake City,UT to Medford,OR (USA), was on approach to Medford's runway 32 cleared for the VOR/DME C via the arc approach with the additional instruction "cross CEGAN at or above 7800 feet". "

ATC cleared the flight to begin the arc "at or above 7,800." The arc begins at CEGAN.

The crew descended to the altitude in the clearance, which was the MVA, and had a GPWS terrain warning, to which they responded, hence the article.
I am one to admit error i did not realise cegan was the start of the arc, i see the confusion.
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Old 01-24-2018, 08:03 PM
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Originally Posted by JohnBurke View Post
Your sentence is not very clear, however, according to the article under discussion:

"A Skywest Canadair CRJ-900 on behalf of Delta Airlines, registration N162PQ performing flight OO-3567/DL-3567 from Salt Lake City,UT to Medford,OR (USA), was on approach to Medford's runway 32 cleared for the VOR/DME C via the arc approach with the additional instruction "cross CEGAN at or above 7800 feet". "

ATC cleared the flight to begin the arc "at or above 7,800." The arc begins at CEGAN.

The crew descended to the altitude in the clearance, which was the MVA, and had a GPWS terrain warning, to which they responded, hence the article.
Why did the crew descend mindlessly to 7800' approximately 40 miles, by way of planned course, away from the airport? I think the international situation has changed but an ATC clearance would be given to a final altitude that would require you to still comply with enroute or terminal altitude restrictions. Even in the old days some "drivers" who had gotten by being hand hold by ATC in the US got some rude awakenings elseware.
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Old 01-25-2018, 02:35 AM
  #23  
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I've noticed in southeast Florida, the ATC will generally instruct to cross at or above/descend maintain the minimum altitude for the fix or segment. We got a clearance today to cross at or above which was 500 feet lower than the minimum altitude for the segment. Student took the bait. Heck of an easy trap to fall into. The altitude he gave us was likely the MVA for that area, and the controller was getting his tail kicked due to saturation. Happens, but we're supposed to catch it.
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Old 01-25-2018, 07:39 AM
  #24  
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Originally Posted by 1wife2airlines View Post
Why did the crew descend mindlessly to 7800' approximately 40 miles, by way of planned course, away from the airport? I think the international situation has changed but an ATC clearance would be given to a final altitude that would require you to still comply with enroute or terminal altitude restrictions. Even in the old days some "drivers" who had gotten by being hand hold by ATC in the US got some rude awakenings elseware.

Yes, mindless on their part. But many, many other US domestic pilots would have fallen for that, very common to get vectored below published step-down altitudes in the US. Getting vectored or cleared below published altitudes would not have automatically raised eyebrows. You would have to look at the actual terrain in that case.
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Old 01-25-2018, 03:28 PM
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At or above doesn't mean you have to start down right away. Studying that approach chart should show that high terrain goes all the way through the arc and through BRKET and SERTE. Some people are just wired to put the lowest cleared altitude and start down.

These approach plates are color coded now so telling terrain apart is really easy. Yikes on this approach! Glad EGPWS saved them.
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Old 01-26-2018, 05:43 AM
  #26  
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The black arrow is your friend.
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Old 01-29-2018, 02:07 PM
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Originally Posted by rickair7777 View Post
Yes, mindless on their part. But many, many other US domestic pilots would have fallen for that, very common to get vectored below published step-down altitudes in the US. Getting vectored or cleared below published altitudes would not have automatically raised eyebrows. You would have to look at the actual terrain in that case.
I agree with this. In MANY airports in the US, I've been cleared down to the MVA, then told to cross a fix 1000 feet below its charted altitude restriction. Within radar contact, if ATC clears you to cross a fix at or below a certain altitude, in the US, this assures terrain clearance. While the crew *SHOULD* have done a better job of cross-checking the clearance, it is not their solely their fault. ATC holds the lion's share of the blame in this situation. With as much responsibility as they have placed on our shoulders over the last decade with regards to charted procedures, I'm not surprised this has happened. All the guy had to do was clear them to the IAF and then cleared for the approach. Issuing an altitude is a completely unnecessary piece of information, unless of course he intended them to descend to the bottom altitude at CEGAN.
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Old 01-29-2018, 05:24 PM
  #28  
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FAA ATC is required to assign an altitude with the approach clearance when clearing an aircraft on an unpublished route. See FAAO 7110.65 4-8-1 Approach Clearances. This was very technically legal as the MVA was 7,800 from where the aircraft was located to CEGAN. It was erroneous due to the MVA later on the arc rose to 8,700’. The ATCO would have been better to say, “cross CEGAN at or above 10,000’”.

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Old 01-30-2018, 02:43 AM
  #29  
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Originally Posted by galaxy flyer View Post
FAA ATC is required to assign an altitude with the approach clearance when clearing an aircraft on an unpublished route. See FAAO 7110.65 4-8-1 Approach Clearances. This was very technically legal as the MVA was 7,800 from where the aircraft was located to CEGAN. It was erroneous due to the MVA later on the arc rose to 8,700’. The ATCO would have been better to say, “cross CEGAN at or above 10,000’”.

GF
Given that the aircraft was not provided vectors at this point and ATC would not be providing terrain separation or guidance during the approach, use of the MVA was at best misleading and erroneous, and at worst, very dangerous. The use of MVA in the descent and approach clearance, even if not explicitly stated as MVA, implies that ATC has ratified that as an acceptable altitude. The use of MVA from an ATC perspective also implies a willingness or capability of continuing to provide vectors or direction at that altitude, if given as available, to ensure continued terrain clearance at that altitude.

Unless ATC had every intention of continuing to use MVA throughout the flight progress to the airport in the form of vectors, it shouldn't have been given in the approach clearance.
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Old 01-30-2018, 07:35 AM
  #30  
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John,

I agree and the controller, if using MVA, had, by policy, to have the arc displayed on the video and monitored the flight progress. Certainly, the latter was not done. I’m not arguing the controller was correct, just a very narrow read of .65. Pilots always need to assume terrain clearance responsibility, if only, because they die if they’re wrong.

GF
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