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B733, Tabing Padang Indonesia, 2012

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Summary
On 13 October 2012, the crew of a Boeing 737-300 destined for the new Padang airport at Minangkabau inadvertently landed their aircraft on runway 34 at the old Padang Airport at Tabing which has a similarly-aligned runway. The Investigation found that the Captain disregarded ILS indications for the correct approach after visually acquiring the similarly aligned runway when the correct runway was not also in sight. Since the chosen runway was some 6 miles ahead of the intended one, a high descent rate achieved through sideslip, followed with this unstable approach, continued to an otherwise uneventful landing.
Event Details
When October 2012
Actual or Potential
Event Type
Human Factors, Runway Incursion
Day/Night Day
Flight Conditions VMC
Flight Details
Aircraft BOEING 737-300
Operator Sriwijaya Air
Domicile Indonesia
Type of Flight Public Transport (Passenger)
Origin Kualanamu International Airport
Intended Destination WIEE
Actual Destination WIMG
Take off Commenced Yes
Flight Airborne Yes
Flight Completed Yes
Flight Phase Landing
LDG
Location - Airport
Airport WIMG
General
Tag(s) Approach not stabilised,
Airport Layout,
Approach to Wrong Airport,
Approach Unstabilsed at Gate-no GA,
Copilot less than 500 hours on Type
HF
Tag(s) Manual Handling,
Procedural non compliance,
Violation
RI
Tag(s) Wrong Runway"Wrong Runway" is not in the list (ATC error, Accepted ATC Clearance not followed, Incursion pre Take off, Incursion after Landing, Runway Crossing, Intersecting Runways, Intersecting extended centrelines, Towed aircraft involved, Near Miss, Ground Collision, ...) of allowed values for the "RI" property.
Outcome
Damage or injury No
Causal Factor Group(s)
Group(s) Aircraft Operation,
Air Traffic Management
Safety Recommendation(s)
Group(s) Aircraft Operation,
Air Traffic Management
Investigation Type
Type Independent

Description

On 13 October 2012, a Boeing 737-300 (PK-CJT) being operated by Sriwijaya Air on a scheduled domestic passenger flight from Medan (Polonia) to Minangkabau, Padang as SJY 021 commenced an ILS approach to runway 33 at destination but then unexpectedly made an approach and landing in day VMC on a nearby and similarly-aligned runway 34 at the old Padang Airport at Tabing. After completing the landing and taxi in to the available parking area, the Captain advised the actual location of his aircraft to ATC at the intended destination and the 96 passengers on board were then disembarked at Tabing.

Investigation

An Investigation was carried out by the Indonesian National Transportation Safety Committee. Data from the FDR were successfully downloaded and available to assist the Investigation but relevant data on the CVR had been overwritten when it was allowed to continue running by the Captain after the landing at Tabing.

It was found that the 58 year-old Lithuanian national who was Captain of the 737 had a total of 15,500 flying hours and was accompanied by a 45 year-old First Officer of Indonesian nationality who held a permanent residence permit for Japan and had a total of 800 flying hours including 173 hours on type. He had completed his initial line training one month prior to the occurrence of the investigated event. The Minang (Minangkabau) TWR controller who had been working the aircraft during the final stages of its approach was found to hold a controller licence issued four months before the occurrence and since then had, after an initial one week period observing, worked in the TWR at Minangkabu.

It was noted that the flight had proceeded uneventfully until the aircraft was descending on the ILS approach to runway 33 in IMC and working Minang APP. It was noted that the earlier crew approach briefing by the Captain who was acting as PF had not mentioned the presence of a similarly-aligned runway sited around 6nm before the designated destination landing runway which was noted on the applicable Jeppesen ILS approach chart (reproduced below). The cautionary note on this subject included on the chart was apparently not noticed by either pilot, possibly due to the poor quality of the black and white photocopy of the chart which they had available. However upon spotting a runway approximately 10° to the right of track through a gap in the cloud which had the superficial appearance of the expected orientation, the crew reported to Minang APP that they had the runway in sight and were transferred to Minang TWR. When the 737 checked in, the controller stated that he "saw the aircraft was on long final and issued a landing clearance for runway 33". However, the Captain then decided to make a visual approach to the runway which had come into view through a gap in the clouds (and which he believed was Minang) and quickly disconnected the AP and "flew manually toward that runway". In doing so, he "assumed that the localiser indication was incorrect" since it began to indicate a need to fly left to regain the localiser whereas the runway in sight was on the right. Having called for landing gear down and flaps 40, the Captain continued the descent using a sideslip technique to achieve what he considered was a rate of descent which would bring the aircraft onto an appropriate vertical profile for a landing at an airspeed in the vicinity of the calculated one. This rate was about 1,700 fpm and the objective was achieved. The subsequent landing at the visually-acquired runway was uneventful and the aircraft was taxied to the apron and parked. The Captain then called the cabin crew and "clarified that they had landed at Tabing" and advised Minang TWR likewise.

The Jeppesen Chart for the ILS Approach at Minangkabau used by the crew [reproduced from the Official Report]

The Investigation noted that runway 34 at Tabing had the same asphalt surface and was the same width (45 metres) as runway 33 at Minangkabau but was shorter - 2150 metres long instead of 2750 metres. Tabing had been the commercial airport serving Padang until July 2005 when commercial operations moved to the new Minangkabau airport and Tabing became a military aerodrome. The relative position of the two runways is shown on the diagram below - Tabing is 6nm southeast of Minangkabau and the runway 33 extended centreline passes approximately 2nm west abeam of the threshold of runway 34 at Tabing - although it would have been a little closer than that when the Tabing runway was first seen by the 737 Captain and the assumption that it was the Minangkabau runway made.

The relative positions of the two runways [reproduced from the Official Report]

It was noted that the Boeing 737-300 FCTM described the elements of a stabilised approach including a maximum rate of descent of 1,000 fpm by 500 feet agl if on a visual approach and stated that a landing from an unstabilised approach should not be attempted. It was also noted that TWR controller Standard Operating Procedures (SOPs) were described in an associated AIC as requiring that, visibility permitting, "controllers shall maintain a continuous watch on all flight operations on and in the vicinity of an aerodrome".

The annotated ground track of the aircraft showing its deviation from the ILS [reproduced from the Official Report]

Four Safety Issues which led to the pilot continuing the approach to a landing and to the controller not noticing the deviation were identified by the Investigation as follows:

  • Predicted flight profile
Although aware that the extended centreline of the runway visually acquired did not correspond to the indication of an extended runway centreline which would be expected to correspond to a centred ILS LOC display, the Captain "assumed that the ILS signal was in error" and therefore disregarded it. A replication of the lateral deviation flown is illustrated above.
  • Runway identification
The 737 crew reported having "the runway in sight" when they were at an altitude of 3,300 feet (the destination airport ARP is only 18 feet amsl) and only 6nm from the runway concerned. The aircraft was at that point on a vertical profile which corresponded to the ILS GS and would have been clearly indicating as such. It was considered that the Captain's assumption that the runway in sight was the correct landing runway may have been affected by a previous experience of a false VOR indication during one particular VOR approach at another airport. It was considered that this, the poor readability of the note about Tabing on the approach plate photocopy and the fact that it was the Captain's first experience of the runway 33 approach to Minangkabau meant that the Captain was "insufficiently familiar with the approach environment".
  • Decision to land
The use of sideslip and a rate of descent of 1,700 fpm was "against stabilised approach criteria" in the absence of a prior "special briefing". The decision to land from such an approach in those circumstances "could lead to ineffective flight deck coordination that might increase the flight risk".
  • Attention of the controller to the landing aircraft
During the occurrence, it was noted that the TWR controller was responsible for just one other aircraft besides the approaching 737 and that aircraft was on the ground being pushed back from its gate. It was considered that "controlling two aircraft can be considered as a low traffic movement condition and can be assumed to be a low workload". However, the controller still failed to monitor the progress of the 737 on final approach. This "absence of aircraft observation meant that the abnormal approach of the 737 went unobserved and un-assessed and the aircraft was not advised to avoid what was an unnecessary deviation". It was considered that "this inappropriate implementation of the regulations on aircraft observation” might possibly be an indication of insufficient assessment and/or insufficient time under supervision prior to release to unrestricted duty.

The Investigation determined that the Contributing Factors to the accident were as follows:

  • The indistinct but significant information (about Tabing) on the (black and white) photocopy of the ILS approach chart might have been missed by the pilots and reduced their awareness of the runway at the nearby airport which had a similar direction and dimensions.
  • The Captains previous experience of a false VOR signal might have been why the approach was continued when the aircraft was not stabilised on the approach.
  • Information on the existence of a potentially confusing runway was not provided by ATC during the abnormal approach to it as it was not being monitored by the controller.

Safety Action taken as a result of this event and known to the Investigation included the following:

  • Sriwijaya Air introduced a system to allocate all its airports into A, B or C Categories using conventionally-applied criteria and pilot familiarisation requirements commensurate with the level of operational challenge presented by each airport. They also introduced a restriction on the rostering of foreign or newly qualified Captains with newly type-qualified pilots.
  • The Operator of Minangkabau Airport issued a NOTAM advising of the presence of the similarly aligned runway at Tabing and amended ATC procedures by adding a requirement for ATC to require pilots on approach to runway 33 to "report 7nm".

Four Safety Recommendations were made as a result of the Investigation as follows:

  • that Sriwijaya Air should emphasise the implementation of stabilised approach procedure. [04.O-2016-61.1]
  • that the AirNav Indonesia District Office Minangkabau Padang should ensure the air traffic controllers maintain a continuous watch as required by Advisory Circular 170-02. [04.A-2016-53.2]
  • that the AirNav Indonesia District Office Minangkabau Padang should review the rating assessment process for air traffic controllers to ensure that the applicant meets the appropriate levels of knowledge and ability. [04.A-2016-61.1]
  • that the Directorate General of Civil Aviation should ensure that additional information or a caution in respect of approach hazards is provided in the published Aeronautical Information Publication and included on relevant Instrument Approach Charts. [04.R-2016-62.1]

The Final Report was released on 10 October 2016.

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