Good day for GPWS
 

This goes back to the pre-TEM days of swiss cheese layers.

They punched thru 3 layers of cheese and they just missed the hole in the 4th layer. Good thing the GPWS was there as a 4th layer.

The 5th unintended cheese layer of 7800 feet may have saved them by a few hundred feet, but maybe not at at 6 degrees celsius?

Big fat Awe-Crap on ATC for a LET THE LAWYERS SORT IT OUT clearance. I'm not a controller, so I will defer judgement.

Aw-crap on the crew for taking the ambiguous ATC clearance bait.

Big fat Atta-boy to the crew for following the GPWS. Many FOQUA events reflect crews disregarding GPWS or being dangerously slow to react.

No, but IIRC it's a 1 or 3 day MEL.

Not that I have a dog in this particular fight, but I am seeing a trend with ATC here. I have been getting cleared for approaches into nontowered airports where they “allow” me to descend below a published segment. I say allow because those clearances are extremely misleading. A simple, cleared at or above “fix minimums” cleared “approach “ would suffice. Not clear us for anything lower than the segment altitude.

Just my .02

In US domestic ops, RJ drivers get used to quickly dancing to arbitrary and constantly changing ATC instructions in large terminal areas. If you fail to respond instantly, you'll likely create a conflict.

This leads to the mindset of comply now, think about it later. In this case the crew should have at least double checked what they were doing after they initiated the descent.

But these guys have been trained by the system to react quickly... foreign aircraft are handled with kid gloves, and the locals are assumed to be familiar with the area, experienced, with a good command of english so they get used and abused when ATC needs buffers and adjustments.

They are also very accustomed to getting vectored in below published altitudes... even on complex non-precision approaches in the mountains. Most of them are probably not aware that a "cross at or above" clearance could legally be issued with an altitude below safe altitudes on the approach. Most would tell you (based on common practice) that you can immediately descend to the at or above altitude.

What the controller did may or may not have been legal, but it sure wasn't consistent with what his buddies do in practice

SKW CRJ has near CFIT:
 

https://www.airlinepilotforums.com/skywest/110739-good-day-gpws.html

/close

GPWS saves the day
 

A Skywest CRJ9 was cleared to "at or above 7800'" on an approach that specified an altitude of 10000'. Down they went to 7800, but the GPWS prevented collision with the mountains.

Any thoughts on the appropriateness of the ATC clearance?

Details:

http://www.avherald.com/h?article=4b3d8f81&opt=0

Several things spring to mind.

The ATC clearance to cross CEGAN at or above 7,800' implies that the crew is safe all the way down to 7,800.' It appears that ATC took the position that the procedure required 10,000 at CEGAN, and therefore a clearance to cross at or above 7,800 didn't prevent them from following the published numbers. This is a very dangerous slippery slope, and I don't buy it.

What if ATC had said "at or above 1,000?" Clearly it's not possible, but it implies that the crew may commence the procedure at the ATC altitude. ATC frequently provides vectors at altitudes lower than procedure altitudes, such as vectors to a localizer or ILS. The approach guidance with a glideslope is nearly always intercepted from below.

In this case, I'd be leary of beginning the approach at CEGAN at anything less than 10,000. That said, one might look at the arc and the high points along the arc to note that The highest point to be encounered is joining the inbound course from the arc, and that altitude is 7655. One might be forgiven for hearing the altitude restriction, glancing at the chart, and believing that based on the presented data, the clearance and arc imply guidance safe from terrain.

At the same time, neither crewmember had flown this procedure or routing before?

While the arc is beyond the 25 nm MSA radius, the radius for that area varies between 8,800 and 10,700; a crucial clue that 7,800 may be unwise, despite the potentially disasterous clearance.

Another important clue is that BRKET (27 DME OED) is published at 10,000, the next fix inbound is SERTE (21 DME OED) at 8,500. Clearly at that point in the approach one is still restricted well above 7,800, and a review of the procedure and briefing of the procedure should be enough to convince to fly the published altitudes.

Another observation is that both crewmembers heard the clearance and both agreed to the decision to descend below published altitudes, apparently. The narrative doesn't suggest one crewmember voicing an objection.

This reminds me somewhat of the B757 mishap in Colombia years ago, American 965, in which the crew was cleared via an NDB, but entered the wrong one. Both crewmembers bought into the decision, and ultimately they did get a GPWS alert prior to impact.

If this procedure was database selectable, were they not seeing the segment altitudes in more than one place; procedure charts or displays as well as on the FMS/FMC?

Holy crap....

A quick glance at the chart shows about a 20 mile arc and a 20 mile final. Why would they want to get down and close to the terrain and get bounced around when not necessary if they had any vertical navigation awareness? The FMC might also have given them some vertical navigation info if time permitted finger fking it.

They're used to getting slam dunked in places like that, so they're spring-loaded to get down sooner rather than later, especially on a complicated approach.

Worth noting that a SLC 900 probably had a very, very senior CA (who grew doing a VOR approaches into mountain holes in a metro), so there's likely some cultural misunderstanding about how those at-or-above clearances work.

I agree. Confusing at best, if not an outright bogus clearance.

SKW CRJ's don't do coupled VOR approaches with the FMS. They could, and likely would, use the FMS for the ARC, but would need to switch to raw data before the marker. They still typically would have displayed the FMS course w/ constraints on the MFD.

But I don't think awareness of the stepdown altitudes was the problem. I think the problems were...

- Assuming that they were good down to 7800 based on an MVA.

- Lack of awareness of actual terrain (this is all on them).

When I worked there, I could have gotten sucked into this right up until that last part... I like to read the terrain highlights on approach plates... especially doing DME arcs to a VOR approach in mountains in IMC.

Lots of valuable lessons here. Pilots Must query ATC if a clearance does not make sense or is unclear.

250Kts and 10000' at Cegan would be my off the cuff planning depending on the type of course. In areas of terrain I would rather be high and adjust. Why drive around at 7800' 40 miles out? A 27 mile arc to final would not be complicated even with just a bearing pointer.

MVA at Cegan is 7,800, which is apparently why the controller issued such a dangerous clearance, but the controller shouldn't have done it unless he or she intended to provide vectors and terrain clearance continuously. MVA is, after all, for vectoring. To assign an altitude at the MVA, or even suggest it as part of a clearance when a vector is not part of the assignment, is setting the crew up. Very dangerous.

A firefighting operator (no longer in business) that used P-3's accepted a dispatch to Missoula a number of years ago. Conditions required the use of an approach at Missoula. The nature of that kind of operation means very short notice dispatches or diversions; it's a constant thing. On arrival, the crew found that they did not have a printed chart for the procedure, and ATC provided it for them verbally.

Without the ability to see the procedure in front of them, they did not have the situational awareness. The arc at Missoula arrives to final from two directions, at two altitudes. They were fine at their arrival altitude on the arc, and fine if they made the correct turn to final and completed the approach. They were not fine if they missed the turn and continued on the arc into rising terrain, which is what happened. The altitude worked for one segment of the approach, but not all...much like an MVA in the case of the procedure in this thread, which was acceptable at CEGAN perhaps, but not for the remainder of the procedure.

The two cases are not identical, but do draw on some salient points. The procedure doesn't help much if not followed. The diagram and details aren't much use if not used. While an ATC clearance should be flown when received, the old adage to trust but verify seems cogent. The entire procedure should be reviewed, particularly in mountainous terrain.

Deviations from published procedures, even on vectors, can be invitations for Murphy. We got vectors to the procedure in Kabul one night, which means off course in very tall mountainous terrain. It ought not be a problem, but heavy jamming was taking place with difficult communications; ATC was in and out. At some point, we lost all electrical, dark cockpit, loss of displays. We found ourselves going to memory items then trying to rebuild the system by checklist, and unable to copy additional vectors, with other aircraft nearby. Dominos. At what point, when accepting deviations from what's published, or even when getting to what's published, do we find the gates starting to close? At the point it becomes critical to know the high points, know the terrain, and know the details, it's already too late to begin looking it up. Hence prebriefing.

Ultimately, all that could have been avoided here by simply flying the published procedure in accordance with the clearance, which was "at or above 7,800." 10,000 on the arc is at or above, and hides a multitude of sins.

I was going into JFK that day, never seen worse low level turbulence. Had the F/O call airspeed on final, as the panel was unreadable. One of those days you earn it for the year. We got to the gate, passengers had to jump to the jetway. Outbound Capt. gave me a dirty look. (JFK-BDL):eek:

ATC did not say descend and maintain 7800 ft until the fix just cleared the arc and cross xxx at or above 7800ft. One look at the chart shows the arc to be 10000 until intercept.

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.

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.

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.

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.

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.

The black arrow is your friend.

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.

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.

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

Part of being PIC is making the call to refuse an aircraft that has an operational MEL if the situation warrants it. If I'm going into mountainous terrain, at night, in the wx, you can be damn sure I'm not going without a GPWS.

No. This crew gets no slack. It was a poorly crafted, no-sense clearance and they shouldn't have accepted it or simply complied with the non-precision approach for which they were cleared (since the at or above clearance gave them that latitude).

First of all - anyone in 121 ops receiving a clearance to fly a full, No-PT arc to a vor/dme-C in the mountains needs to have their guard up. I think their eventual choice to get the ILS should have been exercised upon arrival looking at the wind trend.

But, they decided to accept the VOR. Okay, fine. But, when that clearance comes in, how can anyone flying a modern FMS equipped jet not have at least a couple of HUGE question marks over their heads? They're flying a published approach.
:confused: #1 - 7800 MSL isn't even a depicted altitude on the approach.
:confused: #2 - Why would ATC give a clearance that may require us to climb after we've already descended (I say "may" because they did have the option to stay at or above 10K)

This stuff about some RJ drivers being instinctively prone to comply and ask questions later is nonsense. Little boys worrying about making ATC mad need to grow up, put their big boy pants on and figure it out.

We input the approach in the box, check the points/altitudes and brief, with someone cross-checking the box with the plate. At some point, you would think they had to at least discuss the fact that the lowest altitude on the arc from CEGAN to BRKET was 10,000. So, they either comply with their clearance but stay at/above 10K until starting the lead turn off the arc, realizing that ATC set them up or they CLARIFY.

But, since neither of those two options were exercised, it seems pretty clear that these two guys were grossly unfamiliar with the approach they just accepted a clearance to fly. I obviously can't say for sure, but it seems like a reasonably conclusion that they didn't brief and didn't cross-check FMS inputs. If they did either of these two things, I find it hard to understand how they got to the point of a GPWS alert.

All that said, this ATC controller was an idiot. Someone needs to educate him on the huge difference between legal and smart. Combining an unrelated MVA with a clearance to begin a full-up instrument procedure from a distant IAF may be legal (don't know for sure) but it's certainly not a good practice. We get tested enough on a daily basis from threats we can't control or minimize. We don't need ATC throwing out random Easter eggs because they're too lazy to use an appropriate altitude for a VOR clearance instead of just grabbing the MVA off their screen.

Adlerdriver,

Then again, I’ve seen pilots, 250nm from the destination, act as if the descent clearance is a command and never ask, “do we need start now” or “can we make that, ‘when ready, descend’”.

GF

Quite so.

At the end of the day, the controller goes home to sleep in his own bed. This is not always true of the crew and contents.

I'm not saying I'm giving the crew slack. I said they should have known better. I'm just saying the mistake isn't SOLELY their fault. I am just as frustrated as anyone else here who watches their FO or CA dive for the AT in a At or above clearance instead of using FMS VNAV or staying level and grabbing the GS and following it down. I have found even the most experienced captains have some of the worst instrument procedure knowledge. Yes, they should have never descended below 10,000 as depicted in the arc. If they weren't comfortable flying the arc or it had been awhile since flying one, they should have requested the ILS. Unable is a beautiful creature and we need to use it more as pilots. Too often, lazy controllers do what is best for them and not always what is safest for the aircraft.

And like I said before, one of the biggest problems is that we so often get vectors for the approach, a lot of pilots get confused (their fault) on vectoring for a final and full approach procedures. We are so used to getting clearances to descend below platform altitudes that most don't even flinch anymore...like driving it in at 4000 feet over Lake Michigan to O'Hare or being 20 miles out of ATL and getting 3000 feet (not depicted on any platform).

I understand what you're saying and I respectfully disagree. They knew they were flying a full-up IAP. ATC can't override published altitude restrictions in that situation. What they chose to do did not comply with the IAP they were cleared to fly. That's 100% their responsibility. It's that simple.

If ATC had vectored them into a GPWS alert trying to get them onto a portion of the approach down track, then I would agree the blame should be shared.

The only reason I even threw a single spear in the direction of ATC was because he actually came back and defended the dumba$$ clearance he gave them. If he had acknowledged the altitude limit he provided made no sense and it was a mistake, I'd have nothing to say about him (other than it was a human error that caused confusion).

But we get confused by ATC regularly. We do the same to them. That's why we use the feedback loop and clarify as necessary. The one nice thing about being cleared to proceed direct to an IAF and cleared for the VOR/DME-C is that the communication is done. The restrictions, routings and mins are all there in black and white with no requirement for further communication until we switch to tower. This was a procedural error on the part of this crew who somehow arrived at that point in their career with the mistaken impression that ATC could lower a depicted IAP altitude restriction over VHF. The error is all theirs, IMO.

I can understand how this happened better than I can understand your position.

Okay, fair enough. I'm either off base, not making my point well or a little of both.

Sure, I can understand how this happened too. It appears that ATC instructions were perceived as the gospel even though they directly contradicted the printed information on the IAP the crew was cleared to fly.

So, these two pilots either believed ATC could clear them to start an IAP from the IAF at an altitude lower than published...or

They were unaware of the published minimum altitude on the arc.

Both of those situations are unacceptable in my opinion and point to a perception and/or procedural failure on the crew's part.

It would appear the problem is assuming ATC is infallible and blindly following their instructions in the face of very specific and clear published guidance to the contrary. That's my point.

Would you blame ATC or say they at least shared the blame if ground cleared someone to taxi across the grass to get to the gate and they complied? Some things are simply black and white and the pilots are the final quality check.