WestJet flight in Sint Maarten


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Couldn't find the original post re this incident but here are the results of the investigation>

Misidentification of runway in reduced visibility contributed to the March 2017 risk of collision with terrain of a WestJet flight in Sint Maarten Français


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Transportation Safety Board of Canada

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GATINEAU, QC, June 4, 2018 /CNW/ - In its investigation report (A17F0052) released today, the Transportation Safety Board of Canada (TSB) found that unexpected weather conditions on final approach, reduced runway conspicuity, and inadequate flight path monitoring led to a risk of collision with terrain.

On 7 March 2017, a WestJet Boeing 737-800 was operating as flight 2652 from Toronto/Lester B. Pearson International Airport (CYYZ), Ontario, to Princess Juliana International Airport (TNCM) in Sint Maarten with 158 passengers and six crew members on board. It entered a significant rain shower shortly after crossing the MAPON (missed approach point) waypoint. The crew initiated a missed approach 0.30 nautical miles from the runway threshold at an altitude of 40 feet above water. Once visibility improved, the crew conducted a second approach and landed without incident.

The investigation determined that the runway lights and the visual guidance system (PAPI) had been set at a low intensity during the rain shower that had obscured the view of the airport environment. Both the shower and the low lighting limited the visual references available to the crew to identify the runway properly until the aircraft had exited the rain shower and visibility sharply improved.

The sudden and unexpected poor visibility during the final approach increased the flight crew's visual workload and led to inadequate altitude monitoring. The crew did not notice that the aircraft had descended below the normal angle of descent to the runway threshold until the enhanced ground proximity warning system issued an alert.

After the occurrence, WestJet developed a corrective action plan, including information for pilots regarding possible challenges and threats on approaching and landing at Princess Juliana International Airport. WestJet also revised its Route & Aerodrome Qualification for TNCM with additional information. In addition, guidance on airport lighting system management will be added to the Air Traffic Services operations manual in TNCM by September 2018.

The TSB is an independent agency that investigates marine, pipeline, railway and aviation transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.

The TSB is online at www.tsb.gc.ca. Keep up to date through RSS, Twitter (@TSBCanada), YouTube, Flickr and our blog.

SOURCE Transportation Safety Board of Canada

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For further information: Transportation Safety Board of Canada, Media Relations, 819-994-8053, media@tsb.gc.ca

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http://www.bst.gc.ca

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1 hour ago, rudder said:

Many similarities to AC at YHZ. Non precision approach. Poor visibility encountered below MDA.

If the WJ 737 did not have EGPWS, I wonder if the outcome would have been less favourable.

The YHZ approach was in marginal conditions whereas the SXM was a passing rainshower. As far as airport lighting you have to remember where you are landing. Also, if this had been an ILS approach through a rain shower would they have flown below the path before the runway? The 737NG would have had a Vnav path displayed so no real excuse for getting low in my opinion. 

Edited by blues deville
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56 minutes ago, blues deville said:

The YHZ approach was in marginal conditions whereas the SXM was a passing rainshower. As far as airport lighting you have to remember where you are landing. Also, if this had been an ILS approach through a rain shower would they have flown below the path before the runway? The 737NG would have had a Vnav path displayed so no real excuse for getting low in my opinion. 

No Vnav path into TNCM once passed mapon the MAP.  At most airports the MAP is the rwy so we have path info right to touch down. MAP TNCM is 2nm from rwy threshold.  Lots of opportunity to drift low once vis was restricted.

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55 minutes ago, cjet said:

No Vnav path into TNCM once passed mapon the MAP.  At most airports the MAP is the rwy so we have path info right to touch down. MAP TNCM is 2nm from rwy threshold.  Lots of opportunity to drift low once vis was restricted.

Okay understood. But one could argue why a normal rate of descent from the MAP was not better maintained. 

Anyway, they did the right thing and went around, re-grouped letting the passing shower clear. 

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1 hour ago, cjet said:

No Vnav path into TNCM once passed mapon the MAP.  At most airports the MAP is the rwy so we have path info right to touch down. MAP TNCM is 2nm from rwy threshold.  Lots of opportunity to drift low once vis was restricted.

So does the 737 not present some type of pseudo glide path below the MDA?

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Actually, these two incidents are exactly the same. In both cases fully qualified crews flying perfectly serviceable aircraft were not fully aware of their aircraft position relative to the ground and the runway below the MDA.

Lesson for all of us is if you are not 100% certain below the MDA then go around. It is no different than the stabilized approach criteria. It is not a snapshot taken at a specific point but rather a set of criteria that must be met AND maintained from the assessment point all the way to touchdown.

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Still don’t understand why, if a passenger looking out the window has time to recognize that they are “so low”, why the pilots would have put themselves so low, so far back from the threshold, and then fly along for a few thousand feet before doing a g/a. Nobody monitoring the rad alt??

From the video, it looks like they had some visibility, at least enough out the side windows, to determine where they were.

 

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1 hour ago, rudder said:

Actually, these two incidents are exactly the same. In both cases fully qualified crews flying perfectly serviceable aircraft were not fully aware of their aircraft position relative to the ground and the runway below the MDA.

Lesson for all of us is if you are not 100% certain below the MDA then go around. It is no different than the stabilized approach criteria. It is not a snapshot taken at a specific point but rather a set of criteria that must be met AND maintained from the assessment point all the way to touchdown.

Have to disagree with you on your comparison of these events. 

1. AC at YHZ: Non-GPS A320 with x-wind gusting to 21kts, 1/2 mile vis in moderate snow, vertical vis 200’, temp -5, QNH 29.62”.

2. WS at SXM: See photo 

 

66FDFC7A-448E-4444-907A-97922F731EBF.jpeg

Edited by blues deville
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6 hours ago, J.O. said:

So does the 737 not present some type of pseudo glide path below the MDA?

Only if the MAP is the runway threshold.  If the MAP is the threshold we have a VNAV path all the way down.  

 

CJET

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Most telling is this:

Quote

Approximately 1 nm from the runway, the aircraft exited the shower; the visibility sharply improved, and the crew realized that they had been tracking toward an incorrect visual reference, which was a hotel situated to the left of the runway. At this point, the aircraft was 190 feet AGL, descending at 940 fpm, rather than 320 feet AGL on a standard 3° angle of descent. Now able to see the actual runway, the crew recognized that the aircraft had deviated laterally to the left of the inbound final approach course, but they were not immediately able to assess their height above water. The PF advanced the throttles from 52% to 75% N1 and began to correct the lateral deviation, but the aircraft continued to descend at about 860 fpm.

At 1534:03, when the aircraft was 63 feet above the water, the aircraft's enhanced ground proximity warning system (EGPWS) issued an aural alert of "TOO LOW, TERRAIN" and the PF increased the pitch to 4° nose up. The aircraft continued to descend, and a second aural alert of "TOO LOW, TERRAIN" sounded as it passed from 54 feet to 49 feet AGL (Figure 2).

 
Figure 2. Standard 3° angle of descent versus the aircraft vertical approach path
Standard 3° angle of descent versus the aircraft vertical approach path
 

At 1534:12, when the aircraft was 40 feet above the water and 0.3 nm from the runway threshold, the crew initiated a go-around. The lowest altitude recorded by the EGPWS during the descent had been 39 feet AGL.

for those interested here is a link to the complete report. http://www.tsb.gc.ca/eng/rapports-reports/aviation/2017/a17f0052/a17f0052.asp

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The issue I raised in the original thread on this subject was that the  incident was not reported immediately to (DX-FLTOPS) so that DFDR and CVR could be re-covered. As well it appears that 2 EGPWS warnings and an GA at 39 ft did not warrant suitable notification as  a "reportable incident" to the TSB.  Am I to assume (ass out of you and me) that the TSB investigation was initiated by media and social media reports (and pictures) of the approach? 

 

1.11 Flight recorders

The aircraft is equipped with a digital flight data recorder (DFDR) and a cockpit voice recorder (CVR). Because the occurrence was originally assessed by WestJet as a non-reportable event, it was not reported directly to the TSB. The CVR and the DFDR data were overwritten and were not available to the investigation.

The quick access recorder (QAR) data file was sent to the TSB laboratory for analysis. QAR data is recorded by the aircraft's digital flight data acquisition and management unit, which stores the data on a Personal Computer Memory Card International Association (PCMCIA) card for flight data monitoring (FDM) purposes. The data on the card is an exact duplicate of that collected by the DFDR; however, the DFDR is crash-protected whereas the QAR is not, and the latter typically holds many more hours of data.

 

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"If the MAP is the threshold we have a VNAV path all the way down."

 

Is the pilot able to create a threshold MAP with the FMS?

If pilots were to start hand flying non-precision profiles in good weather conditions instead of relying almost entirely on 3D guidance and auto flight  

 these sorts of events might be reduced. 

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7 hours ago, DEFCON said:

"If the MAP is the threshold we have a VNAV path all the way down."

 

Is the pilot able to create a threshold MAP with the FMS?

If pilots were to start hand flying non-precision profiles in good weather conditions instead of relying almost entirely on 3D guidance and auto flight  

 these sorts of events might be reduced. 

No we can’t.  FMS sequences to the missed after the MAP.  F/D guidance is gone as well.

 

Cjet

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2 hours ago, cjet said:

No we can’t.  FMS sequences to the missed after the MAP.  F/D guidance is gone as well.

Cjet

As you know after arrival on profile at the MAP the approach becomes a visual manuever. If the decision is to continue, you must establish and maintain a safe rate of descent as you would on any aircraft. 

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29 minutes ago, anonymous said:

Does the airline involved have a statement with regards to the finding of the investigation?

 

From the report:

After the occurrence, WestJet developed a corrective action plan, including information for pilots regarding possible challenges and threats on approaching and landing at Princess Juliana International Airport. WestJet also revised its Route & Aerodrome Qualification for TNCM with additional information. In addition, guidance on airport lighting system management will be added to the Air Traffic Services operations manual in TNCM by September 2018.

Edited by blues deville
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