On 24th February 2020, Trans Maldivian Airways DHC6-300 seaplane Twin Otter Reg: 8Q-MBC, on a flight from Velana International Airport to Kuredhu Island Resort with fifteen passengers, two pilots and one cabin crew, sustained substantial damage to the aircraft during a bounce landing.
The aircraft while landing touched down and bounced; after the bounce while the aircraft was still airborne, the aircraft banked to the left dipping the left wing-tip into the water and the aircraft veered to the left. The right wing of the aircraft then abruptly dropped. The PIC attempted to to intiate a go around after the bounce without success. During the accident the fuselage, wings, engines and propellers of the aircraft sustained substantial damage. Both the floats were intact and the aircraft was upright after the event. The aircraft was moved and tied to the buoys with the assistance of the left engine and a dingy. All passengers and crew were able to evacuate, safely. However, as a direct consequence of the accident, two of the operating crew and one passenger suffered minor injuries.
The captain was a 31 year old with 4,436.3 hours of total flight time with 2,774.5 on type while the first officer was a 31 year old with 1,007 hours of total flight time with 768 on type. The FO was the PF for the sector for the flight. According to the flight crew, no abnormalities were observed throughout the flight. Descent began 15 mins prior to landing at Kuredhu, and the FO gave the briefing and descent checks were carried out. The winds were easterly, and the sea conditions were found to be rough.
The FO requested the PIC to ‘standby for the line’ and once Kuredhu was visible, the FO infomed that it would be “Right base for north east bound landing”. The FO reported seeing white caps and the waters were choppy but was confident of landing in such rough waters, as having done similar landings even the week before. The FO communicated the line to the PIC and stated “in case of go-around we will climb to 500 feet as per the SOP”. The PIC advised the FO to keep the aircraft slightly to the left, closer to the reef, just on the lighter blue area, as it was believed that look this area was relatively calmer. At around 400 feet, FO called out for full flap and max rpm, and repeated for a second time “that in case of ground we will climb to 500 feet as per the SOP” and FO stated that there was no obstruction. The PIC confirmed landing just outside the lagoon and about 10 degrees into the wind. Landing inside appeared to be more risky to the PIC, due to number of obstructions including boats and buoys, and the landing outside the lagoon was believed to be safer. No circle overhead was carried out due to not realizing the rough conditons. During approach, at about 100 to 150 feet the PIC noticed the speed was low and instructed the FO to correct the speed. The FO responded by correcting the speed. The FO reported noticing an altimeter difference of 20 to 40 feet between the altimeters. The FO also reported noticing a difference of 2 to 3 knots on the ASIs. The aircraft, while landing touched down and bounced, which appeared to be manageable, according to both the flight crew. As soon as the aircraft bounced the FO was advised by the PIC to add power for a go-around. At the same time FO heard the fire alarm. As power was added after the bounce, the aircraft banked to the left with the left wing tip dipping into the water and veering the aircraft to the left.
Once the aircraft bounced, the PIC attempted to intiate a go-around by adding power but the speed bled off and there was a simulataneous left wing drop. The FO tried to level off the aircraft but reported controls extremely heavy.
Immediately after the dip, the PIC attempted to shut down the right engine as the fire bell was continuously ringing, but could not move the fuel levers as it was jammed, and as a precautionary measure subsequently activated the fire extinguisher bottles, and then switched off the fuel shutoff valves and also shut-off the right engine boost pump. The PIC instructed the FO to visually check for a fire in right engine, to which the FO confirmed there was no visible fire, but smoke emanating due to engine exhaust. The FO recalled continuously checking outside checking for the float damages as usually float damages are associated with heavy landings.The FO after seeking approval from the PIC, started to follow the evacuation procedure and with the assistance of the cabin crew instructed and assisted the passengers to remove the seat belts. The passengers were instructed to remove the life jackets from under the seat and all passengers were made to wear the life jackets but was instructed not to inflate the life jackets. The passengers were told to wait for the boat.
FO reported calling the TMA dispatch three or four times and reported an accident and requested for help. A jetski (water scooter) and a speedboat arrived but the jetski declined to tow the aircraft as jetski would not have the capacity to tow the aircraft. Using the operable left engine and controlling the aircraft using the left engine power lever the PIC attempted to maintain the aircraft. After about 15 minutes the resort dinghy arrived and helped the aircraft to be secured to the buoy. Once the aircraft was secured the left engine was shut down, the passengers disembarked and baggage was offloaded, after which the crew went to the resort.
INITIAL FINDINGS
Based on the information gathered during the course of the investigation, the facts listed
below have been determined:
- The aircraft had a valid certificate of airworthiness;
- The crew had valid licenses and qualifications to conduct the flight;
- The aircraft was subjected to abnormal force during landing.
- The Engine vibration isolator assemblies installed on the right-hand engine which failed during the landing had previously undergone eddy current inspections as called for in the Maldives CAA Airworhtiness Directive. The mount has sufficient hours left for next inspection;
- As per the operator, normally SD cards are installed in all the aircrafts. However, the SD card which normally capture the operating data on Garmin G950 system was found missing;
- The weather condition at KUR water aerodrome was unknown prior to departure of the aircraft from main base MLE.
- Poor coordination between the PIC and FO and misjusdgment of the pilot flying.
- No Pre flight briefing
- CAA Air Safety Circular ASC14-2 Amendment 1, Procedure and requirements for
licensing water aerodromes and floating platforms, dated 04 February 2009, requires one wind direction indicator to be mounted on the movement area, but none was available.
SAFETY RECOMMENDATIONS:
- Since fracture of the engine mounts had occurred on several other DHC6 aircraft in the past, it is recommended that sheared mount undergo metallurgical test alongwith one other serviceable engine mounts belonging to the same batch available with the operator;
- Since the aircraft is installed with Garmin 950 avionics suit under STC and the system is capable of recording several parameters normally captured on a FDR, it is recommended that CAA Maldives establish procedures to prevent loss of the data card installed on the display;
- It should be noted that the AICC in its recommendations following several previous accident investigations, has recommended CAA to re-examine the criteria for carriage of flight recorders on transport category aircraft, certified to carry more than 9 passengers, with a view to requiring all aircraft to carry at least a CVR. It is therefore recommended MCAA consider previous recommendations by AICC.