Accident: Trigana B733 at Wamena on Sep 13th 2016, hard landing results in main gear collapse

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Accident: Trigana B733 at Wamena on Sep 13th 2016, hard landing results in main gear collapse

By Simon Hradecky, created Tuesday, Sep 13th 2016 05:20Z, last updated Monday, Aug 3rd 2020 22:31Z

A Trigana Air Service Boeing 737-300 freighter, registration PK-YSY performing flight IL-7321 from Jayapura to Wamena (Indonesia) with 3 crew and 15.3 tons of cargo (fuel, rice, sugar), landed on Wamena's runway 15 at 07:35L (22:35Z Sep 12th) but touched down very hard in a nose high attitude, left the left main gear behind, the right main gear collapsed, and the aircraft slid on nose gear, belly and both engines to a halt at and partly beyond the right hand edge of the runway. There were no injuries, the aircraft sustained substantial damage.

A ground observer reported, the cloud base was about 150-200 feet, the aerodrome features no instrument approaches and thus is strictly visual approach only. A Trigana Boeing 737-300 landed successfully a few minutes earlier, then PK-YSY was seen breaking out of cloud, correcting to the right and pitching down to descend towards the runway. The aircraft subsequently touched down very hard in a nose high attitude, the left main gear separated from the airframe, the right main gear collapsed, and the aircraft skidded on nose gear, both engines and the belly to a halt right of the right hand edge of the runway past the new apron. The airport is currently closed.

Indonesia's Ministry of Transport reported flight TGN-7321/IL-7321, carrying 15,353 kg of freight consisting of drums of Diesel as well as sugar, rice and other goods, was involved in an accident at Wamena at 07:35L, when the aircraft slid to a halt at the right hand side of the runway. There were no injuries. The condition of the runway surface is being assessed, the accident is being investigated by Indonesia's NTSC/KNKT.

On Dec 8th 2016 the NTSC released their preliminary report reporting the aircraft impacted the runway producing a vertical acceleration of +3.25G causing the left main gear to collapse and separate and the right main gear to collapse, the aircraft received substantial damage.

The NTSC reported that the flight was conducted in visual meteorologic conditions, enroute at FL180 the flight crew was able to identify another Trigana flight heading for Wamena. The aircraft was number three in landing sequence and entered a hold before being cleared for the approach.

At about 7000 feet the crew received landing clearance however could not identify visual checkpoint Mount Pikei and decided to check another visual reference, a church at the right base runway 15. The captain (59, ATPL, 23,823 hours total, 9,627 hours on type) decided to reduce the rate of descent. The first officer (22, CPL, 650 hours total, 480 hours on type) reported that the runway was not in sight and called for a go-around. At 5700 feet MSL and about 2nm from the runway threshold the crew acquired visual reference with the runway and increased the rate of descent, that ultimately led to a "touch down" at +3.25G. The aircraft came to a stop about 1890meters past the runway threshold.

The weather office reported the weather at the time was defined by haze, visibility was 2000 meters.

On Aug 4th 2020 the KNKT released their final report concluding the probable cause of the accident was:

Refer to the previous aircraft that was landed safely, the pilot confidence that a safe landing could be made and disregarding several conditions required for go around.

The KNKT analysed:

The Flight Data Recorder (FDR) data showed that during approach the aircraft descend with rate of about 1,500 feet/minute and at altitude about 6,200 feet or at about 1,000 feet above ground level (AGL), the altitude was maintained for about 18 seconds. Thereafter, the aircraft descend with average rate of about 900 feet/minute. The Cockpit Voice Recorder (CVR) data showed that after the GPWS altitude callout �one thousand� the PF able to see the church, however the pilot had not seen the runway.

The pilot decision to maintain the altitude likely due to the weather condition that made the pilot did not have visual references. After the pilot saw the church, the descend approach continued.

The approach descend once again was stopped, and the aircraft maintained at about 5,600 feet or about 400 feet AGL for about 21 seconds. The CVR data showed that after the EGPWS altitude callout �five hundred�, the PF instructed the PM to check the runway. This showed that up to this point, the pilot had not seen the runway. The PM replied that they were one mile away which probably refer to the runway threshold and advised for go around and also mentioned that they were too far. The stop descend might had made the aircraft deviated from the approach profile and became above the correct glide path.

At 22:30:41 UTC, the CVR recorded EGPWS warning SINK RATE which indicates that the aircraft was on excessive descent rate. The FDR showed the attitude recorded pitch down to 11�, the calculated rate of descend reached up to 3,200 feet/minute, the aircraft rolled to the right up to 28� and the speed increased by 7 knots. The video footage showed the aircraft attitude was rolling and pitching down. The CVR recorded EGPWS warning �PULL UP�. During this time, the PM reported to the tower controller, that the runway was in sight. Five seconds after the EGPWS warning �SINK RATE� the aircraft touched down.

The rate of descend was recorded up to 3,200 feet/minute while normal approach landing rate of descend for approach was between 700 to 800 feet/minute. This excessive rate of descend indicated that when the pilot able to see the runway, the aircraft was too high for approach and require excessive sink rate to reach the touch down point.

The aircraft touched down with vertical acceleration 3.25 g, the aircraft speed 137 knots, pitch 7� up and roll to the left 5�. The calculation of FDR data showed that the rate of descend prior to touch down was 2,300 feet/minute.

The CVR recorded the pilot statement of the power levers were advanced but the power did not increase. The advancing power levers might be the pilot attempt to reduce the rate of descend by pitch up and advanced power. The aircraft pitch changed from 11� down to 7� up reduced the rate of descend from 3,200 feet/minute to 2,300 feet/minute on touchdown. The CASR Part 25.473 requires the landing gear able to support a landing with the rate of descend 10 feet/second (600 feet/minute). The aircraft landed with the rate of descend of 2,300 feet/minute was greater than the requirement.

The pilot stated that the power levers were advanced to recover the sink rate but the engine power did not increase, this might be caused by the delay of the engine to accelerate. The FDR did not record the engine parameters therefore, the throttle movement and the change of power could not be determined. These pilot actions indicated that the recovery to the condition was not in timely manner.

The aircraft touched down with recorded vertical acceleration was 3.25 g and roll 5� to the left. The impact force was received mainly by the left main landing gear. The excessive vertical acceleration created significant force to the left main landing gear combined with the side force which not aligned with the normal landing direction resulted in the collapse of the left main landing gear.

Excessive sink rate resulted in touched down with high vertical acceleration and led to the failure of the main landing gears.

The instrument approach procedure was not available for Wamena Airport and the approach and landing shall be performed under Visual Flight Rules (VFR). The visual navigation aids such as Visual Approach Slope Indicator (VASI) and several runway lights were unserviceable at the time of occurrence.

According to the CASR Part 91, the weather minima for approach in VFR was
visibility of 4.8 km and ceiling 1,000 feet.

During the flight preparation, the pilot received weather information of Wamena Airport which stated on the right base runway 15 of Wamena Airport, on the area known as mount PIKEI, low cloud was observed with the cloud base was increasing from 200 to 1000 feet and the visibility was 3 km.

The weather report of Wamena Airport between 2130 � 2230 UTC indicated that the visibility between 2 to 3 km and the cloud base (ceiling) between 100 to 400 feet.

The weather information showed that the weather condition did not meet the minima for VFR flight. The pilot decision to depart to Wamena Airport might be caused by the assumption that the weather would improve at the time of arrival.

During descend, the Wamena Tower controller informed that the wind was calm, QNH 1010, temperature 16�C. The weather information did not contain the information of ceiling and visibility which required by the crew to determine the weather minima for approach.

After completed holding and approved for approach, there were several conversations between pilots, indicated that the weather was not suitable for approach. It was indicated by some visual reference points that were not visible. The PF also stated that the flight would direct to PIKEI. The other pilot of aircraft ahead of the accident aircraft stated that only the bottom of Mount Pikei was open. This indicated that the ceiling was low and the visibility was limited. Based on the FDR data and the video footage, it was estimated that the pilot able to see the runway about 400 feet AGL.

The Visual Approach Guidance for Runway 15 Wamena Airport, published by the aircraft operator, showed that if at 6,100 feet, at 2.8 Nm from runway or about point PIKEI, a safe landing cannot be made, the aircraft should go around.

During the approach, when the aircraft was about 1,000 feet AGL, the PM reminded the PF that the approach was too high. The PM also suggested the PF to go around and followed by the statement that they were too far. None of PM advice were taken by the PM. The suggestions was not seriously considered by the PF was caused by the successful landing of previous aircraft.

After the pilot able to see the runway, the descend approach was continued and the calculated rate of descend was 3,200 feet/minute. The excessive rate of descend contrary to the stabilized approach criteria and triggered the EGPWS warning of SINKRATE and PULL UP to active.

The PM reported to tower controller that the runway was in sight and two seconds after the aircraft touched down. Landing clearance had not been issued by the tower controller.

The reminder and suggestion of the PM were not taken by the PF indicated lack of crew coordination and resulted in the flight continued the approach landing under the un-stabilized approach condition and the weather that was not suitable for landing.

While PK-YSY aircraft on holding, another aircraft was successfully landing on existing weather condition. The success of another flight landing on the existing weather condition had made the pilot confidence that the aircraft could be landed safely.

Several indications of weather below the visual approach minima, un-stabilized approach, the PM suggestion to go around, EGPWS warning, and absence of landing clearance did not make the pilot decided to go around. The pilot was confidence that safe landing could be made as the previous flight landed safely.

Related NOTAM:
C5495/16 - RWY DISPLACED FM BEGINNING RWY 33 DUE TO BLOCK BY ACFT, DECLARED DISTANCE AS FLW:
RWY 15 TORA 1000 LDA 1500
RWY 33 TORA 1500 LDA 1000
13 Sep 04:55 2016 UNTIL 13 Sep 07:00 2016. CREATED: 13 Sep 04:55 2016

Observer Video, now in HD and used by KNKT (Video: MD):

https://www.youtube.com/watch?v=xEiKpp8lH60

The left main gear (Photo: Aviatren):

Ground tracks and PK-YSY (Photos: MD):

Point of first impact (Photo: MD):

Map (Graphics: AVH/Google Earth):

Visual Approach Chart Wamena (Graphics: NTSC):

Reader Comments: (the comments posted below do not reflect the view of The Aviation Herald but represent the view of the various posters)

Life is not easy in Indonesia.
By Kalle on Saturday, Aug 8th 2020 20:04Z

Just read the names on the approach chart:
pyramid
pass valley
north gap
middle gap.....

Same airline, same airport, same cowboy flying
By Extremely Worried on Tuesday, Aug 4th 2020 19:01Z

This is the 1st in a chain of 3 reported events on AVH about events besetting this so called airline with some really wild flying.
The most recent event from just a week ago seems a mirror event of busting limits, taking extreme measures to �complete the mission, no matter what�, and this investigation from almost 4 years ago illustrates the utter contempt that these �pilots� have for safety and CRM.
Clearly the culture of contempt and disregard for safety lies with the management since they fostered an indifference to what happened 4 years ago, which manifested itself in almost a duplicate attempt to getting the cargo delivered no matter the potential for a real tragedy of killing innocent bystanders on the ground.
Probably the same lunatics upfront at the helm of the two crashes.
Enough is enough. Indonesia aviation authorities have to shut this outfit down NOW, otherwise they give carte blanche to every rogue operator to go it alone with no palpable oversight or consequences.

@Andy:
By Beobachter on Saturday, Dec 10th 2016 19:39Z

Yes, it looks like the other aircraft stands in the grass, but if you look closer, you'll see that it's actually a small taxiway.

The Other 737-200
By Andy on Saturday, Dec 10th 2016 03:53Z

Did anyone else see the other 737-200 before the plane landed? It looked like it taxi'd into the grass. Anyone confirm, or just a bad picture and looks like its in the grass?

@JW
By Jon on Friday, Dec 9th 2016 20:00Z

The outboard tire is deflated but without weight on it doesn't compress to the rim. Based on the skid mark photo it looks like the plane landed rolled to the left putting most of the load on the outboard wheel (and adding lateral load that likely caused the separation).

L main gear tires
By JW on Friday, Dec 9th 2016 19:10Z

Someone who knows: explain how a main gear leg can be broken off without deflating the tires.

@ Iain on Friday, Dec 9th 2016 16:52Z
By Tango Sierra on Friday, Dec 9th 2016 18:48Z

I remember working wight & balance with a pre-printed document of e European airline on which the headerline really read LOADSH*I*T.

@ IAIN
By JH on Friday, Dec 9th 2016 17:00Z

It's just you.

By Iain on Friday, Dec 9th 2016 16:52Z

Is it just me or is it common to see spelling errors on a company chart?

737
By Ray on Monday, Oct 31st 2016 00:28Z

I fly around this area, this airport is 6000 Feet AMSLelevation with high terrain.

there are 3 airlines fly cargo here, now they DO NOT follow any procedures at all. they do not have airman ship, and even a xxxxxing basic common sense that other aircrafts too flying around this area, they would turn final 9Miles at 14,000 feet direct to finals, i dont know how thy do that. of course end up in hand landing and break the wheel just like this incident.

I hope they would at least for god sake repects others pilots life and follow a porcedure or even follow a checklist, its a total bush flying with the 737 classic earring cargo.

@goodShipAirMan
By 727driver on Wednesday, Sep 21st 2016 09:25Z

Stall?

possible, but don't think so.

"I wonder why they didn`t perform a go around since the approach was obviously unstable."

That's the million dollar question, not dumb at all :).

Dragging it in?

Stall?
By goodShipAirMan on Tuesday, Sep 20th 2016 18:05Z

I wonder why they didn`t perform a go around since the approach was obviously unstable. Is it possible that we have seen a stall from which they almost recovered from by pitching the nose downwards to get some airspeed quickly?

I apologize for bad English and maybe dump question but I am just a german fsx pilot :-)

PK-YSY
By 727driver on Monday, Sep 19th 2016 20:00Z

Delivered 1986 to Western Airlines.

RNAV....?

@Robert
By 727driver on Monday, Sep 19th 2016 19:30Z

Yes, they now have a RNAV 15 approach.

Minimum 6.450' that's 1.033' AGL... !!!!!!!!!!!!!

RNAV
By Lee on Monday, Sep 19th 2016 18:57Z

Was the RNAV network actually operational?

Not quite true that airport is visual only
By Robert on Monday, Sep 19th 2016 18:03Z

There actually is an Rnav approach to 15 at Wamena.

@Lee
By No surprise on Sunday, Sep 18th 2016 19:57Z

Your succinct summary says it all. However the pilots in this outfit and the region aren't rewarded for being cautious, careful and by the "book" based on criteria employed throughout the rest of the world. Crap nav aids, lax SMS culture, no proper regulatory oversight and operators whose sole objective is to get a completed flight at any cost, leads to a culture of " get it done, or get another job" leading o the outcomes we read here.
The local populace is not up in arms about some rules being bent- nor does it seem is the government or else operating licenses would not be granted so liberally. Only when there is a dire shortage of food, supplies, fuel etc will anything tangible be done, and then it will take a page cultural change of valuing life that will get any real change.
Don't blame the pilots who are getting the job done under tough circumstances.they are a product of their environment.

summary
By lee on Sunday, Sep 18th 2016 17:01Z

- visual runway used in IMC conditions
- unstabilized approach
- last second nose push-down (to aggravate a bad situation)

did I miss anything else

737-200
By Tech on Sunday, Sep 18th 2016 01:30Z

Check out the old 737-200 in the foreground on the video. I have not seen one of those in the U.S. in a very long time.

Diesel_Drums
By Pepe on Saturday, Sep 17th 2016 21:08Z

Is it legal to carry Diesel Drums as General Cargo ???

@Paul
By Marek on Saturday, Sep 17th 2016 19:28Z

Indeed, looks like they come down on a way too steep path. Also, it looks like they were in a bank. Absolutely not stable the last few sec being airborne.
I'm looking forward to the full report from this investigation.

Papua need operation to run like this. VFR flights into IMC. VFR flights doing visual approaches in imc. This is going on every day. They need infrastructure, such as radar, ils's and vor's, and making sure flights can operate under ifr.
This practice is done by all pilots out on papua, locals and expats on easa/faa etc licenses, every day. It is the only way, as of now. That is why the gov need to get up proper nav aids, include ifr flights by proper ifr approved crew and aircrafts, and then overseeing the operations to see if they adhere to the rules. It will take some time in this huge and remote region.

ops normal
By Pro on Saturday, Sep 17th 2016 18:01Z

Latest reports indicate it hit a Bajay (Tuk Tuk) hence the reason for the nose leg being ripped off.

Approach
By Paul on Saturday, Sep 17th 2016 16:59Z

I'm the first to admit my lack of expertise, but that approach doesn't look stabilised to me at all.
At 0:06, right before he disappears behind the parked 737,
he makes a rather sharp diving turn to the right.

Looks like a good landing
By Impressed on Saturday, Sep 17th 2016 16:31Z

The landing in the video looks well controlled, on centre line smoothly executed. Don't see bouncing or other indications of hard landing. Too bad the runway was damp and not wet- then the crew could have vacated and not blocked the runway, with surface damage to belly and engine cowlings. Shame, since a low vis- visual couldn't be complimented with standing water which would have helped with the hydro planing controlled by differential reversing for directional control.
At the least the rice, sugar and diesel arrived intact which is what is really important.

@Chris 777
By herman on Saturday, Sep 17th 2016 16:27Z

"different tire size" Chris your exactly correct! makes perfect sense to me.

Different Tire Size
By Chris 777 on Saturday, Sep 17th 2016 16:16Z

It is standard practice to rotate wheels for wear, and even put main gear wheel on the nose. This way the aircraft rolls on one nose wheel saving wear and extends the life of tires which are really expensive. Of course pilots have to compensate for this by keeping aileron down on the low side to prevent the aircraft from tipping during landing and takeoff. During fueling and passenger loading, wooden posts are place on the low side wing to also prevent tipping- much like B52s and U2.
The only limitation is putting a larger wheel on- can't put A380 wheels in 737, but 737 wheel can be put on A380.....
Excellent observation that many experts missed.

RE: stowed T/R
By GB on Saturday, Sep 17th 2016 16:13Z

Regardless of procedure, crew actions etc. Think about it!! If there is no gear at all, how could the WOW interlocks/safeties possibly be bypassed. I'm just a dumb mech and don't have B733 wrench time, but I'm pretty sure that both of the drivers could haul back on those levers till they broke off and the T/R's wouldn't budge
Just my random input

G

@Alexander Tambiev
By Been There on Saturday, Sep 17th 2016 16:00Z

Two reasons the tires look different in size. 1 - Optical illusion because of the photo angle. 2 - The tire furthest from the camera appears to be deflated. The tires are indeed different, but only because they are from two different manufacturers. This is quite common.

As for installing a nose tire in a main position, this is not possible. The axles are different sizes, wheels are different sizes, and a nose wheel will certainly not fit over a brake. In fact, a nose wheel and tire diameter are about the same size, if not smaller, than a MLG wheel.

@ Alexander Tambiev
By Michael on Saturday, Sep 17th 2016 15:59Z

Are you serious with that question?!?! :)))

By Ghee on Saturday, Sep 17th 2016 15:45Z

Incredible footage for sure, especially now that it's in HD. Seems typical that the 732 was blocking the view so we couldn't see touchdown, that would make things too easy...

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