Airline Pilot Central Forums

Airline Pilot Central Forums (https://www.airlinepilotforums.com/)
-   Safety (https://www.airlinepilotforums.com/safety/)
-   -   Good day for GPWS (https://www.airlinepilotforums.com/safety/110739-good-day-gpws.html)

JohnBurke 01-22-2018 08:09 PM

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?

UAL T38 Phlyer 01-23-2018 05:44 AM

Holy crap....

1wife2airlines 01-23-2018 06:59 AM

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.

rickair7777 01-23-2018 07:08 AM


Originally Posted by 1wife2airlines (Post 2509225)
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.

rickair7777 01-23-2018 07:17 AM


Originally Posted by JohnBurke (Post 2509033)
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.

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


Originally Posted by JohnBurke (Post 2509033)
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?

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.

PerfInit 01-23-2018 07:45 AM

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

1wife2airlines 01-23-2018 08:34 AM


Originally Posted by rickair7777 (Post 2509232)
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.

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.

JohnBurke 01-23-2018 09:59 AM


Originally Posted by rickair7777 (Post 2509239)
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.

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.

Hetman 01-24-2018 03:53 AM

http://libraryonline.erau.edu/online...s/AAR75-16.pdf

badflaps 01-24-2018 03:44 PM


Originally Posted by Hetman (Post 2509961)

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:


All times are GMT -8. The time now is 02:07 AM.


User Alert System provided by Advanced User Tagging v3.3.0 (Lite) - vBulletin Mods & Addons Copyright © 2024 DragonByte Technologies Ltd.
Website Copyright ©2000 - 2017 MH Sub I, LLC dba Internet Brands