TMA DHC6 at Vommuli on May 16th 2023, wing strike with water

Last Update: April 30, 2024 / 17:46:12 GMT/Zulu time

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Incident Facts

Date of incident
May 16, 2023

Classification
Accident

Airline
TMA Trans Maldivian Airways

Departure
Aluvifushi, Maldives

Destination
Vommuli, Maldives

Aircraft Registration
8Q-TAQ

Aircraft Type
De Havilland DHC-6 Twin Otter

ICAO Type Designator
DHC6

A TMA Trans Maldivian Airlines de Havilland DHC 6-300 on floats, registration 8Q-TAQ performing a charter flight from Aluvifushi to Vommuli (Maldives) with 5 passengers and 3 crew, landed at the water aerodrome at Vommuli however hit a swell, bounced, the left wing dropped and contacted the water surface. The crew did not notice any anomalies immediately during landing, there were no injuries, however, substantial damage to the left hand wing was discovered later.

Maldives CAA released their preliminary report summarizing the sequence of events:

The flight from IVL to VOM was uneventful until the initial touch down on water.

The crew did a circuit to conduct a visual check of the landing area and then decided to land parallel to the waves and continued the approach. The PIC estimated the wind was from 280° at a speed of approximately 10 knots.

During landing, the aircraft impacted a swell, resulting in a bounce that led to the LH wing drop and the wing contacting with the water. Immediately after the aircraft came to a stop, the crew checked for any damages and found the damaged LH wing was damaged.

The aircraft taxied and docked on the fixed platform and shutdown both engines. The passengers then disembarked through the main airstair door.

On Apr 30th 2024 the CAA released their final report concluding the probable causes of the accident were:

The AICC determines that the probable causes of the accident were:

1. The aircraft inadvertently hit a swell during landing.
2. Limited experience of the PF to operate to Category C water aerodromes.
3. Complacency and lack of vigilance on the part of PM to closely monitor the situation and take over when necessary.
4. Non-conducive power management for the aircraft behaviour during a bounce.

The AICC/CAA analysed:

In general, wind direction and strength may be difficult to gauge in the absence of an appropriately located windsock, especially where local geography may affect the winds in the landing area. At the time of the landing at Vommuli, the wind was westerly with an estimated speed of 10-15 knots with high swells. During westerly winds, landing areas surrounding Vommuli island experiences wave heights of two to three feet with roller waves, typical for the time of the year. The waves move into the atoll from the north-west and passes through the atoll in a south easterly direction.

While these waves flow between the two islands - Dhoores and Vommuli, the waves create unpredictable, multi–directional swell patterns. Another peculiar feature of these waves is that they have unusually long swell distances.

The PIC was familiar with the VOM landing areas and stated that the water conditions at VOM was ‘nice’ and way better than the previous two days, and this is one reason why the PIC decided to let the FO land.

Crew Co-ordination during Landing & Aircraft Handling

The accident sector was flown by a qualified FO, but having limited experience in landing under the prevailing water conditions. The PIC (a Line Training Instructor) stated that both crews discussed and selected the most suitable landing line which was towards the edge of the Vommuli island reef. As required by the procedures in the TMA Operations Manual, Part A, the aircraft performed a flyover inspection to assess the aerodrome surface conditions prior to landing.

The crew interviews confirm that the required landing checks were carried out including the selection of the flaps. It was noted that the aircraft was relatively lightweight and as per checklist the ref speed (Vref) was less than 70 knots. Both crew members confirmed that the FO briefed the PIC on the landing and that the PIC advised the FO to amend the landing direction and the way to approach for landing.

Hence, the FO was briefed to go to the west on quartering the wind (from the right) paralleling the swells. The PIC stated that this instruction was given to avoid landing head-on (perpendicular direction) due to the large gaps between the swells, as it was the best option under the given water conditions.

The direction of landing was westbound, aiming towards the tip of the lagoon on Vommuli island, and not directly towards Vommuli island. This was to ensure that the go-around path was maintained clear, and Vommuli island will be on the right, in the event a go-around becomes necessary.

The PIC advised FO to land parallel to the waves and continued a normal approach.

During landing, with reduced power, the aircraft hit a swell and bounced. After the bounce, the aircraft experienced a left bank with the left wing impacting the water.

Immediately after the bounce the PIC instructed FO to add power. Following up, the FO stated that the power levers were moved FWD to add power. However, the FO felt the power was insufficient due to the delay in engine spooling up and the aircraft continued to yaw to the left. The PIC took control, recovered and landed the aircraft.

It is noted that the PIC and FO statements contradict each other regarding power management. While the FO stated that the power levers were moved forward to add power as advised by the PIC, the PIC stated that the power levers were retarded instead of moving forward, thus reducing the power. The PIC further stated that he added power after taking over the controls, but the aircraft did not respond fast enough due to the lag in engine spooling.

When asked, the PIC stated that the PF was competent to land under the
circumstances and would let the PF land again, under similar circumstances if the opportunity arises. The PIC added that the lesson learnt was to be more vigilant and prepared to take over from the PF, when needed.