AT76, Ende Indonesia, 2015
AT76, Ende Indonesia, 2015
On 19 October 2015, an ATR 72-600 crew mishandled a landing at Ende, Indonesia, and a minor runway excursion occurred and pitch control authority was split due to simultaneous contrary inputs by both pilots. A go around and diversion direct to the next scheduled stop at Komodo was made without further event. The Investigation noted that the necessarily visual approach at Ende had been unstable with a nosewheel-first bounced touchdown followed by another bounced touchdown partially off-runway. The First Officer was found to have provided unannounced assistance to the Captain when a high rate of descent developed just prior to the flare.
On 19 October 2015, the landing of an ATR 72-600 (PK-GAF) being operated by Garuda on a scheduled domestic passenger flight from Kupang to Ende as GAI2017 was mishandled in day VMC and, after a minor runway excursion, the landing attempt was abandoned and a 40 minute diversion to the next intended stop at Komodo was flown without further event other than split control column authority. When the engineer meeting the aircraft there reported finding grass and dirt on the right side of the aircraft and reported this to the Captain, he was only told that there had been several bounces at Ende but not also about the runway excursion. The sixteen passengers on board for the investigated event were uninjured and the aircraft was undamaged.
After the engineer had re-connected the pitch control system and obtained approval to release the aircraft to service, the same crew continued with their final rostered flight leg to Denpasar uneventfully. Following their arrival there, the crew reported the occurrence at Ende to their Chief Pilot but did not mention that it had included a runway excursion.
Approximately 2½ hours after it had arrived at Denpasar, another flight crew operated the same aircraft on an uneventful flight to Komodo. At this point, the Indonesian DGCA received a report from AirNav Indonesia about the Ende runway excursion and advised the Garuda Safety Department, who in the absence of a report from the flight crew were unaware of it, accordingly. The Safety Department then sought information about the occurrence and, once it had been confirmed, the aircraft was grounded and the event reported to the Indonesian National Transportation Safety Committee (NTSC) - the Komite Nasional Keselamatan Transportasi (KNKT) by the Safety Department, which commenced a Serious Incident Investigation.
The CVR and FDR were removed from the aircraft and it was subsequently possible to download relevant data from the FDR. Relevant data on the CVR had been overwritten.
It was noted that both pilots were French nationals. The 53 year-old Captain, who was PF for the flight, had a total of 9,701 hours flying experience of which 609 hours were on type and the 27 year-old First Officer had a total of 2,300 hours flying experience of which 335 hours were on type.
The aircraft and flight crew involved were rostered to operate six sectors that day, Denpasar- Komodo-Ende-Kupang and return. The event at Ende occurred on the fourth sector of this sequence for which the Captain was the pilot flying (PF). The flight from departure until visual positioning for the second landing of the duty at Ende commenced was uneventful with the Ende ACO (Aeronautical Communications Officer) advising on first contact that runway 27 was in use with the wind from between 140° and 180° with a mean speed of 13 knots gusting to 18 knots and scattered Cumulus at 1,500 feet. After configuring the aircraft for a flap 30 landing, the First Officer subsequently transmitted that they were about to complete the left turn onto final approach and the ACO responded that the spot wind direction was from 150° at 18 knots and advised that the runway was clear.
The AP was disconnected passing a recorded 654 feet agl and on completing the turn onto finals, the aircraft passed over a 180 foot high atoll which was 1200 metres from the threshold and very close to the extended runway centreline at approximately 360 feet agl. The Captain then increased the rate of descent and, although the power was also reduced, the speed increased briefly to 140 knots. On short final, the First Officer recalled having confirmed that the wind sock close to the beginning of the runway was indicating a similar wind velocity to that provided by the ACO. FDR data subsequently showed that from 500 feet agl to touchdown the mean wind direction had remained around 140° whilst the wind speed varied between 7 and 33 knots with a mean of 24 knots.
At a recorded 26 feet agl, FDR data showed that with the rate of descent at 1000 fpm a 13 second duration pitch up input on the First Officer’s control column had begun. Six seconds later, at 11 feet agl, a simultaneous pitch down input had begun on the Captain’s control column.
Three seconds later, the aircraft touched down within the TDZ of the 1650 metre-long runway with the opposing pitch inputs still present. With the achieved pitch recorded as -4°, the nose landing gear was the first to touchdown on the 30 metre-wide runway quickly followed by the main gear at a recorded 1.6g. The presence of a slight left wing down aileron input at touchdown meant that after a 2 second bounce, the aircraft then touched down (and again bounced) on the left shoulder of the runway having drifted left, although this time on the main gear first at a recorded 2g. The First Officer stated that when he noticed that the right control column was functioning as the first touchdown appeared imminent, he had taken over control “whilst the Captain was trying to check the left control column function”. Two seconds after the second bounce, with opposing pitch commands still continuing, FDR data showed that a pitch disconnect warning had occurred and this was recorded as being annunciated two seconds after it happened.
Four seconds after this, the Captain ceased his pitch down input, engine power was increased and a climb away was commenced with the First Officer’s now unopposed pitch up input. After a few more seconds, the First Officer ceased using his now disconnected control column, the Captain took back control and the aircraft climbed away, turning to the right to avoid a known obstacle.
Once the go-around had been completed, the Captain reported that he had “become aware of the severity of the occurrence” and had asked the ACO to check for the possibility of debris on the runway or its left shoulder as a result of the aircraft bounces but was subsequently told that there was none. After assessing the situation, it was decided to divert to what would have been their next stop, Komodo. During this diversion, the Captain explained the situation to the SCCM and, having asked if there was any problem with the passengers, was advised that there was not. The flight to Komodo was completed without further event.
FDR data showed that the final approach had been unstable because the maximum allowable airspeed for an approach at the prevailing aircraft weight at 500 feet agl had been exceeded by either 13 knots (Flight Crew Training Manual (FCTM)) or 18 knots (the Company OM). This situation required the commencement of a go around but this was not called or initiated.
As a potentially relevant context for this finding, it was noted that despite the fact it had been approved by the DGCA , the Visual Manoeuvring Chart for runway 27 Ende published by Garuda for use by its pilots made no mention of any specific procedure to manage an arrival by avoiding the atoll located on short final. It was considered that this omission “may trigger the pilot to improvise the approach based on knowledge, skill and experience that may deviate from the standard”.
In respect of the simultaneous and conflicting attempts by both pilots to control the pitch of the aircraft for touchdown, it was noted that when the PM First Officer intervened with an unannounced pitch up input on his control column the rate of descent was about 1,000 fpm with a hard nose-down contact in prospect and imminent. It was considered that this pitch up input might have indicated that he “intended to correct the aircraft profile in accordance with the procedure and landing technique described in the FCOM” which stated that “from 20 feet agl, the flare shall be initiated by visual reference”. However, the absence of any announcement that he was taking control meant that the Captain was unaware of this.
It was thought possible that this intervention might have been based on previous experience that the First Officer had of “assisting the same Captain during landing approaches at Ende”. In his statement to the Investigation, the First Officer said that as he had often “assisted the same Captain during the landing approach at Ende”, he had assumed that the Captain was uncomfortable flying into there due to the local terrain conditions. He also described the Captain “as a person whom it was difficult to assist” and collectively “these assumptions resulted in the First Officer voluntarily assisting the PF Captain without advising him”.
The Investigation noted that the force of 114 lbs (equivalent to approximately 52 kg) was required to disconnect the control columns “to minimise the risk of untimely disconnection” and that if pitch disconnect occurs without real jamming, applicable procedures require that the airspeed does not thereafter exceed 180 KIAS and that the bank angle is limited to 30° until the flaps are extended to avoid overstressing the stabiliser.
In respect of the failure to report what had happened, it was noted that this was completely contrary to the operator's mandatory procedures as was the crew’s failure to electrically isolate the CVR following any runway excursion.
The Investigation formally identified two Contributory Factors in respect of the occurrence as:
- the continuation of an unstabilised approach with a high approach speed, a nose down attitude and with a roll of about 3° to the left resulted in the aircraft bouncing to the left of the runway centreline.
- the absence of an immediate go around after the first bounce resulted in the aircraft making a second touchdown on the left shoulder of the runway.
Two Safety Recommendations were made as a result of the Investigation as follows:
- that Garuda Indonesia review the implementation of serious incident handling to ensure the serious incident is reported as soon as possible and to prevent the loss of useful information for the investigation. [04.O-2015-23.01]
- that Garuda Indonesia review the Visual Manoeuvring Chart for runway 27 at Ende to prevent pilot improvisation that may deviate from standard. [04.O-2015-23.02]
The Final Report of the Investigation was completed on 25 June 2021 and released on 6 July 2021.