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On 16 August 2015, Trigana Air Flight 267 crashes into a mountainside while nearing its destination of Oksibil Airport in Papua, Indonesia, killing all 54 people on board. The pilots had intentionally deviated from the standard flight path and deactivated the ground proximity warning system.
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00:00on approach to a remote town in indonesia's papua province you're down a turboprop plane vanishes
00:12we tried to think positively that there's a chance the aircraft ended up landing at a
00:23different airport with limited communication overseas a search is underway for an indonesian
00:30plane carrying more than 50 people a treacherous climb up a steep mountain leads to the worst
00:36possible news we'll reach the crash site no survivors the number one priority is to find
00:44the black boxes with no clues investigators hope the damaged black boxes will solve this puzzling
00:53case can you turn that up that's it
01:23centani airport in papua province indonesia
01:41trigana air service pilots captain hassanudin and first officer ariadin are on a short layover before the
01:45flight of the day we got like 20 minutes about that yeah i think i'll get up and stretch my legs
02:02anything from the terminal i'm okay thanks
02:05the pilots have already flown four short flights today in papua this leg will take them to a remote
02:17airport in the oxybill area typically the flights of a commuter aircraft would be an hour or less
02:23so the typical duty day for a pilot might include four or more takeoffs and landings
02:29it's challenging the sense of taking off and landing are the most risky parts of any aircraft flight
02:35and doing so several times in a day could put different kinds of stresses on a pilot
02:40hello flight attendant dita amelia kunyawan good afternoon has been with trigana air service for
02:49three years and knows many of the regulars who fly this route good to see you again
02:5449 passengers will be making the short trip to oxybill
03:02oxybill is a very remote area so most of the passengers would be local government officials
03:15local businessmen very few tourists go to oxybill
03:19you want to stretch on the way back no i'm good for one more leg
03:32i'll set back there dita good to go thank you dita
03:39at 2 22 p.m flight 267 takes off
03:52landing gear up landing gear is up slap set to zero
04:01flap zero
04:06the flight to oxybill takes 40 minutes
04:09the estimated arrival time is 304 p.m
04:14we're at 2 000 feet want to turn on the autopilot
04:20autopilot engaged
04:23the pilots are flying an atr 42 300
04:30a twin turboprop short haul aircraft
04:33the atr 42 is a medium capacity commuter type aircraft
04:39they're popular because they can get into smaller airports
04:42places where you can't really get an airplane that's a 737 or 747 size
04:48into and out of the airport
04:50minutes later the plane reaches its cruising altitude of 11 500 feet
05:00water
05:02the flight is so short
05:10we'll call oxybill
05:12the captain is already preparing for the descent into oxybill
05:17oxybill trugana 267
05:21trugana 267 oxybill copy
05:25we are beginning our approach
05:27elected descent from 11 500 feet
05:29confirm descent from 11 500
05:32let me know when you are positioned over oxybill
05:35oxybill is a small airport situated in a valley
05:40the mountains surrounding it can reach 11 000 feet
05:45decreasing engine thrust
05:50244 knots and dropping
05:55oxybill airport is in a mountainous area
06:00it sits in a valley and on top of that they have very limited navigational aids at that airport
06:08without the aid of advanced landing systems seen at bigger airports
06:13pilots flying into oxybill must keep the runway in sight during the approach
06:21a visual approach as the name implies is an approach where the flight crew has to have
06:27the airport and the surrounding area inside
06:32cabin crew prepare for landing
06:37in preparation please straighten your seat back and store your tray
06:40i'll be coming around to collect any garbage you may have
06:49big plans for the family
06:50yeah looking forward to some time off
06:53yes it's been very busy these past few weeks
07:06flap 15
07:23gear down
07:34wings air one two five zero confirmed descent from 12 000
07:50report when you are positioned over oxybill
07:56five minutes later
07:59the air traffic controller at oxybill realizes flight 267 hasn't reported in as expected
08:06trigona 267 oxybill do you copy
08:11trigona 267 oxybill do you copy
08:14one of the common things that happens when an airplane doesn't land at an airport for some
08:24reason is they may divert to another airfield the crew landing the aircraft may have been too busy to
08:30call the airport before diverting to another airfield hey this is oxybill we've lost contact with flight 267
08:37have you heard from the pilots
08:43you haven't
08:45we might have a problem here
08:52word of the missing plane travels fast
08:54overseas a search is underway for an indonesian plane carrying more than 50 people
08:59the flight lost contact today over a remote area of the country
09:05as the news spreads investigators with indonesia's national transportation safety committee the knkt
09:13fear the worst my first impression was
09:18that something wrong had happened
09:22not looking good
09:25well maybe they just diverted and haven't checked in yet
09:29we tried to keep thinking positively that there's a chance the aircraft suffered from some damage
09:34and ended up landing at a different airport with limited communication
09:40a search and rescue team is assembled consisting of army soldiers and search and rescue personnel
09:51they immediately began the search around oxybill airport because we learned from air traffic control
09:56that its last location was quite close to the airport
09:59flight 267 was only 15 miles from oxybill airport when it last checked in with air traffic control
10:11but search efforts come up empty
10:16until a pilot flying out of oxybill airport spots smoke billowing from nearby tango mountain
10:26we don't have a lot of information
10:29we can only hope that the people on board have survived
10:42the day after a pilot reports seeing smoke in the mountains surrounding oxybill indonesia
10:50the crash site of trigana flight 267
10:53is located
11:04yeah
11:07140 degrees 29 minutes
11:1151.18 seconds east okay got it thank you
11:16thank you the wreckage is at approximately 8 300 feet on a ridge of tango mountain
11:2510 nautical miles from oxybill airport
11:33they went off course how do they end up over there
11:37we need to get eyes on that crash site
11:39a search and rescue team takes a KNKT investigator to the crash site
11:56at over 4 000 feet above ground level there are no roads runways or clearings
12:09the only way to get to the crash site is on foot
12:15to reach the area the team have to walk for about four and five hours
12:20they have to climb and quite steep with the dense vegetation it's quite hard to get to the site
12:29after climbing for five hours
12:37the team finally reaches the crash site
12:44a field of debris stretches through tango's thick forest
12:56and we're going to be able to get to the crash site
13:16go ahead oxybill
13:18jakarta we'll reach the crash site
13:21no survivors
13:22okay
13:27once you catch your breath the number one priority is to find the black boxes
13:31okay
13:36hey guys check it out
13:42we're looking for the fdr and the cvr
13:44because of the remote location
13:50bringing much of the wreckage down from the mountain will be impossible
13:55so the investigator at the scene must document as much as he can
14:00and send photos back to headquarters
14:02while the search and rescue team retrieves the remains of the 54 people that died
14:17the knkt investigator tries to determine exactly how the plane hit the mountain
14:22the trees surrounding the crash site provide an important clue
14:31they are sheared off in a straight line
14:35indicating the plane flew head-on into the mountain
14:38that's right there's no sign they pulled up
14:43how could the crew have flown straight into a mountain that's so well known to pilots
14:48the investigation team's top priority will be to figure out what was happening in the cockpit
14:57at the time of the crash
15:07the plane's flight data recorder
15:09and cockpit voice recorder can be invaluable tools for the investigation
15:23the damaged black boxes are shipped out for analysis
15:43in the days that follow
15:44family members mourn while they wait for the recovery of loved ones
15:59search and rescue along with the local help
16:04have been successful in retrieving the 54 bodies
16:06they are desperate to know what caused the crash that killed everyone on the flight
16:18it's up to knkt investigators to figure that out
16:22they first need to determine why the plane ended up off course
16:26blues the flight path in the approach chart
16:32here's where they crashed
16:32flight 267 crashed about 10 miles west of the approach path into oxybill airport
16:44it went right
16:47and ended up here
16:49i'd like to know more about the terrain around here
16:53to determine the height of the terrain along the flight's path
16:57investigators use special software that generates topographical data for the area
17:02the topographical map reveals that the pilots were flying a treacherous route
17:32they were surrounded by mountains as high as 9 000 feet
17:39why didn't they fly above them
17:43investigators wonder if there was a mechanical problem with the plane that caused it to plow into a mountain
17:50maybe the fdr can tell us
17:55certainly there would have been something in the flight data recorder that may have
17:59given an indication that some system on the aircraft wasn't operating as it should have
18:05when the recovered flight data arrives
18:08nakayo and weboa are eager to get their first look at how the plane was functioning at the time of the crash
18:14wait a minute
18:25this doesn't make any sense he says the plane was going east not south
18:30we were able to download this data that contained all the flight information
18:40but the flight data we recovered didn't correlate with what might have happened on the day of the crash
18:48and the time of day is wrong so was the speed
18:50what can the flight data was not from the day of the accident
18:59digging even deeper into the data the investigators come to a disturbing realization
19:05the recorder wasn't working at the time of the crash
19:09useless
19:10we found that the fdr has been experiencing several problems since 2012 it has been installed to an
19:20aircraft and found fault and then offloaded went to the shop for repair back again to the aircraft
19:29the malfunctioning fdr had no connection to the accident making it much harder for nakayo and
19:35wibowo to figure out what caused it investigators still don't know why flight 267 slammed into the side of a mountain
19:51in the indonesian province of papua the families of the 54 people on board trigana flight 267
19:59lay their loved ones to rest
20:01including flight attendant dita amelia kunyawan
20:13overcome by grief they want answers as to what happened authorities have released new pictures
20:19showing the wreckage from the indonesian passenger plane that crashed in the country's remote eastern region over the weekend
20:26k-n-k-t investigators are facing intense pressure to determine why flight 267 crashed
20:37without recorded flight data the plane's cockpit voice recorder is investigators last hope to learn
20:44what was happening in the air at the time of the crash they would be able to understand what was said
20:51to and from air traffic control and they can also understand any kind of communication formal or
20:57informal that was taking place within the cockpit that can be a huge indicator of something going
21:03wrong with that flight fortunately the cvr data is successfully recovered all right we're ready okay play it
21:13the cvr contains two hours of audio including from the two flights prior to the accident flight
21:23i'll call down and let them know we're coming
21:26investigators first listen to the pilot's flight into oxybill from earlier in the day
21:31in the hopes of finding clues oxybill trigana 267
21:37trigana 267 oxybill copy we're beginning our approach would like the descent from 11 500 feet
21:45confirm descent from 11 500 let me know when you are positioned over oxybill uh oxybill we won't be
21:52over the airport we're going to fly direct to our left base leg to runway 11. copy that left base leg
22:00that's not what it says in the charts they took a shortcut the cvr reveals that the pilots made an
22:06intentional deviation in their approach during their prior flight into oxybill
22:13the official approach directs aircraft to fly over the airport and then circle back and land
22:20but on the earlier flight the pilots flew directly to runway 11 without looping around
22:38500 feet landing flaps and propeller speed are set and confirmed
22:42after flying the shorter approach the pilots landed on the runway at oxybill
22:54without incident
22:59investigators wonder if the pilots tried to repeat that shorter approach a few hours later
23:05but with a very different result let's skip ahead to the accident flight
23:12we're at 2 000 feet want to turn on the autopilot autopilot engaged
23:21confirmed descent from 11 500 let me know when you are positioned over oxybill
23:27oxybill we're flying direct to a left base leg to one way 11. copy that
23:31so they take the same shortcut for the accident flight the last flight proceeds much like the
23:38crew's earlier flight into oxybill
23:41big plans with the family
23:42investigators listen closely for any signs of danger yeah looking forward to some time off
23:51been very busy it's past
23:54it's what they don't hear that raises questions
23:57they're not doing their approach briefing and checklist
24:01briefings and checklists serve several functions one of the key functions is to give the flight crew
24:07a better understanding of their environment not doing that makes it less likely that the pilot will remember
24:14to do certain things or to take certain precautions or to be aware of certain hazards that could be happening on that particular flight
24:24the team now knows that the crew missed a crucial step on their approach
24:28but can the recording reveal anything about how the plane was functioning mechanically just before the crash
24:37can you turn that up
24:44picking up anything with the engines
24:48we try to analyze the sound of the engine
24:52flaps 15 gear down
24:54based on the frequency and amplitude of the sound of the propeller
25:03we concluded that the engine and propeller were both in good shape
25:11nothing unusual
25:15on the last phase of the flight the cvr recorded that the condition in the cockpit was normal
25:24while listening to the final moments of the crash
25:30investigators make a baffling discovery
25:40that's it
25:43normally at the last second of the flight the pilot will have been scream or do something
25:48happened so fast sounds like they didn't even see the mountain
26:02the crash of trigana flight 267
26:18investigators have a theory about the crash of trigana flight 267
26:24they believe that weather may have obscured the pilots view of the mountain
26:28the team scrutinizes weather data recorded less than an hour before the crash
26:35oxabill was covered by dense clouds
26:38the data reveals that at the time of the accident
26:42flight 267 would have been flying through an area of low clouds
26:47the clouds could have been quite dense here
26:50pilots wouldn't have been able to see much
26:51yeah but you know papua you never really know what the weather's going to be like unless you're
26:56looking out the window yourself
27:00it is difficult to determine whether the flight was in cloudy conditions or not
27:04in the mountainous area it can be cloudy in one valley it can be perfectly clear in another valley and
27:09you go to another valley and it's completely covered
27:11to get a first-hand account of the weather conditions on the day of the accident
27:20investigators speak to the controller on duty
27:25what was the weather like on our first flight into oxabill
27:28it looked mostly clear
27:31and did the weather change on their second flight yeah the clouds rolled in it was so dense that i couldn't
27:37even see the mountains the controller tells the investigators that he did inform the pilots about the cloudy conditions
27:46oxabill tragana 267. tragana 267. oxabill go ahead
27:52are the weather looking for our approach you've got a cloud base of 8 000 feet
27:59the pilot's decision to continue flying with so much cloud cover surprises investigators
28:07in principle when flying using visual rules
28:13only one rule applies to arrive safely you must maintain visual contact at all times
28:19visual contact bisa didapatkan gear down
28:25the visual approach is not allowed to be done in the cloudy condition so when the cloudy condition and
28:32they unable to see the whole mountain they should follow the procedures
28:41but instead of following procedure
28:46they knew the base of the clouds was 8 000 feet
28:51they took a gamble that they would eventually catch sight of the runway
28:55they were descending expecting to drop out of the clouds
29:02at any minute instead they crashed into a mountain
29:09at 8 300 feet
29:25we still don't know why they didn't know they were in the path of a mountain
29:33with modern aviation technology even if the pilots didn't see the mountain the plane should have
29:40so why didn't they know they were heading straight into one
29:43we need to check their warning system
29:51when a plane is in close proximity to terrain
29:55or about to hit an object
30:00there's a warning system that warns the pilot when the plane is very close to terrain
30:05the warning system uses gps and a terrain database to monitor an aircraft's height above the surrounding terrain
30:19if the plane comes too close to the ground the system will warn the flight crew with audio messages
30:25terrain terrain terrain pull up so pilots know to increase their altitude
30:32this is the profile of the mountain
30:35this is our flight descending through clouds and the pilots can't see the ridge in front of them
30:43their proximity to the terrain would have activated the terrain caution here
30:48here 60 seconds before impact now the pull-up warning should have gone off here 30 seconds before
31:03were there any warnings going off in the cockpit no there's nothing in the transcript
31:08the absence of audible alerts leads investigators to wonder if the plane's warning system was working properly
31:19the team knows the fdr wasn't properly maintained could the same be true for the warning system
31:27we tried to dig deeper to see if the warning system had been properly installed in trigona 267
31:34last maintenance was performed on august 14th two days before the crash it appeared to be working normally
31:50when we looked into the maintenance record we did not find any significant mention of something
31:55broken in the warning system
31:56with a faulty warning system ruled out investigators now wonder if the terrain data used by the system was accurate
32:12this area is not very well mapped some of the papua area was a very rough data the precision of the data was
32:23not as close to the actual conditions
32:29if you fly in a mountainous area the database itself might not detect the fine details of the contour
32:36of the terrain around you did the lack of accurate terrain data mean the system wasn't able to warn pilots
32:43when they were too close to the mountainous terrain
32:46the trigona 267 investigators decide to speak with trigona pilots who regularly fly in the oxybill area
32:56to find out if they received terrain warnings the pilots report that not only did the system provide
33:04warnings it gave an excessive amount of false warnings due to the poor quality data if you're flying within a
33:11mountainous area it can give you false warning or unnecessary warnings was this area prone to false alarms
33:20imagine you are trying to land in a small airport in the middle of the valley
33:25you can see the airport in front of you in visual conditions and then the system starts giving a warning
33:29terrain terrain pull up you think well i can see the airport in front of me i can see the terrain behind it
33:35that that that that warning is is annoying and what do you normally do when you keep getting these false warnings
33:45hold on he says sometimes they deliberately pull the circuit breaker
33:53sorry go on it's an astonishing finding
33:56it might have been because of spurious or inappropriate warnings by the system that is
34:02it's telling you that you're close to the ground when in fact you're not this is what i like to call
34:07the boy who cried wolf syndrome terrain terrain pull up you know the other flights we've done we've had no
34:14problem let's just turn this thing off terrain but if you pull the circuit breaker you might forget that
34:22you've pulled it and that's not good because if you're going into a valley when it's still cloudy
34:28you still need your systems no matter how unreliable that is any warning you get if you don't have
34:34visual contact with the ground you follow it okay thank you
34:41they just pulled the breaker to get rid of the false warnings
34:47apparently it's common practice are you kidding me
34:50this revelation leads investigators to ask themselves a difficult question did flight 267 lack terrain warnings
35:03because the pilots intentionally turned the system off
35:08both the captain and the first officer were very experienced
35:11in fact i think these pilots are much more experienced than the average turboprop pilot
35:20we reached cruising out to 11 500
35:25is it possible the pilots were overconfident because they had flown this route so often
35:30we also asking questions to some pilots particularly pilots that had experience flying with these two
35:43accident pilots will you excuse me i now have a pilot on the line that says he's personally seen captain
35:52hassen and pulling the circuit breaker we found some information that some co-pilots flying with the captain knew that captain had the habit to inactivate the system
36:09decreasing engine thrust
36:12hooray hooray
36:14overconfidence and complacency are two of the issues that are common in aviation
36:22and what it leads to is certain equipment could be turned off because the pilots think that their
36:27experience in other aspects of flight will more than compensate hooray hooray yeah yeah yeah
36:35when a flight crew operates deliberately with an aircraft that's not fully capable they're increasing the risk
36:42risk of that flight
36:52looking through the captain's records investigators discover that the airline knew about his habit of
36:58pulling the circuit breaker
37:02says here that they scheduled the briefing with him to address it
37:05based on this information we assume that that day on the accident day the captain also inactivate
37:15the system
37:17terrain terrain pull up terrain terrain pull up
37:25investigators now believe that the pilots intentionally disabled their warning system
37:30on an earlier flight that day and then never reset it if the system was active i'm sure that the
37:39accident would have been avoided because the last seconds of the flight before the impact
37:46the system will scream pull up pull up
37:49the pilot would have to take action to save the flight
38:05no wreckage relating to the warning system is recovered from the crash site
38:09investigators can't know for sure if the circuit breaker had been pulled
38:19but even if the pilots were overly confident they could make the approach without the aid of the warning
38:24system there's still something else that doesn't add up
38:28the pilots flew into this area all the time
38:34why were they flying so close to the mountains in the first place
38:41investigators are trying to determine why pilots who were very familiar with the oxabill area
38:47would risk flying so close to the mountains below them
38:51can you pull up this approach chart
39:06a diagram in the corner of the approach chart informs pilots about the safe minimum altitudes in areas
39:13surrounding the approach path
39:15the approach chart says the minimum safe altitude in this area is 8 000 feet
39:21flight 267 crashed at 8 300 feet they were adhering strictly to the information that was there
39:30in the approach chart but the information was wrong
39:33and that wrong information put them at risk for colliding with terrain
39:42we're good to 8 000 feet
39:47investigators believe the pilots were aware of the minimum
39:50safe altitude published on the approach chart
39:55it's the last piece of the puzzle
40:02the crew thinks they're safe down to 8 000 feet
40:09and on the accident day the base of the clouds is 8 000 feet
40:14it makes the pilots feel as long as they're in the clouds they're safe
40:24decreasing engine thrusts
40:25244 knots and dropping
40:34cabin crew prepare for landing
40:38what struck me more than anything was that this was so very preventable
40:41this was a controlled flight into terrain event the investigation has uncovered a confluence of factors that led to the crash of flight 267
40:52big plans for the family
40:55yeah looking forward to some time off
40:59it's been very busy these past few weeks
41:01at the core
41:03two pilots who had grown overconfident flying the route so many times before
41:08terrain terrain terrain pull up terrain terrain pull up terrain terrain
41:17we got this
41:18pull up terrain terrain
41:21because the captain had a reputation for pulling the ground proximity warning system circuit breaker
41:27investigators suspect he disabled the system on an earlier flight that day
41:39then on the last flight into oxy bill
41:42we're beginning our approach would like the descent from 11 500 feet
41:46confirm descent from 11 500 let me know when you are positioned over oxymoron
41:52clear down
41:57the pilots failed to do their approach briefing or safety checks
42:02and relied on faulty approach charts
42:05there are three key things that could have avoided this accident
42:09adherence to standardized procedures
42:12the use of warning systems
42:14and the use of cockpit resource management techniques
42:17which could be as simple as
42:20is there a checklist that should be used
42:30so
42:40three very clear areas where any one of them would have prevented this accident
42:46none of them happened
42:48in the aftermath of flight 267 the knkt makes a series of safety recommendations that will make the skies of
42:55indonesia safer
42:57first of all
42:59the charts need needed to be updated
43:03we also asked the airline operator to request the database for the warning system
43:09to be updated with a more accurate version
43:16up to now we noticed a significant drop in warning system violations
43:20also since the approach chart for oxy bill has been fixed
43:28we've seen a positive impact in terms of flight safety in papua
43:32the lessons from this accident the insights from the investigation
43:42won't go away they'll be here decades from now
43:46i'm confident that the insights from this report will influence design of equipment
43:51will influence the design of procedures will influence the kind of hazards that flight crews
43:56will look out for in the future
44:06you