Maldivian DHC6 at Kuredu on Jul 2nd 2015, hard emergency landing, aircraft sunk
Last Update: February 19, 2017 / 20:41:16 GMT/Zulu time
Authorities are still engaged in attempting to prevent the aircraft from getting completely submerged and tow it to ground. Authorities reported the captain of the flight had accumulated more than 15,000 hours of flying experience.
On Jul 3rd 2015 Maldives Civil Aviation Authority reported that the aircraft performed an emergency landing about 2nm from the destination. Although the aircraft sustained substantial damage and part of the aircraft sank into the sea, no passenger or crew sustained any injury and they were safely taken to Kuredu Resort. The occurrence was rated an accident and is being investigated by the CAA and the Accident Investigation Coordination Committee.
In 2017 the Maldives Civil Aviation Authority (MCAA) released their final report concluding the probable causes of the accident were:
The investigation identified the following causes;
- The aircraft was operated outside the centre of gravity limitations on the sector in which the accident occurred.
- The load distribution errors went undetected because the mass and balance calculations were not carried out in accordance with the approved procedures, prior to the accident flight.
- The co-pilot (PF) was not alerted to the impending stall as she neither saw the stall warning light illuminated nor heard the aural stall warning.
- The PIC was not able to gain control of aircraft as developing stall was not recognised and incorrect recovery procedures were applied.
The MCAA reported the aircraft was being loaded for the flights to Komandoo, 4 passengers were destined for Komandoo, and to Kuredo (11 passengers destined for Kuredo). Ground handlers loaded 779lbs of luggage, therefore 166 lbs for Komandoo, 279 lbs were loaded into the aft luggage compartment. A total fuel load of 835 lbs was on board, the aircraft thus departed with a takeoff weight of 12,484 lbs. The captain (39, ATPL, 5,075 hours total, 4,200 hours on type) was pilot flying for the sector to Komandoo, the flight was without anomalies and landed safely.
The passengers for Komandoo, who were seated in the first and second row of double seats. The 166 lbs of luggage were offloaded, 3 suitcases from the cabin and one hand luggage from the aft luggage compartment.
The aircraft subsequently departed from Komandoo, the first officer (32, CPL, 988 hours total, 705 hours on type) was pilot flying. The takeoff weight was 11,240 lbs with 11 passengers, 613 lbs of luggage and 435 lbs of fuel remaining on board. According to a captain's statement a number of passengers were moved forward in the cabin to maintain center of gravity within limits.
On approach to Kuredo the aircraft joined a left downwind, the speed was reduced to about 75-80 KIAS and the flaps extended to 20 degrees. After the aircraft had joined the final approach, the first officer commanded the flaps to full and propeller levers fully forward. As soon as the flaps were selected fully down, the aircraft began to pitch up and vibrations started. The first officer felt she could no longer control the aircraft and handed controls to the captain, the aircraft was descending through about 300 feet at that time. The captain saw the stall warning light had illuminated (the stall warning horn had been deactivated on the aircraft), noticed a right hand bank and concluded the aircraft was going into a right hand spin.
The captain therefore applied full left rudder, moved the control column forward and reduced the power levers to idle, the aircraft nose continued to rise however. The captain then selected the flaps to fully up and was able to regain some sort of control, the aircraft however impacted the sea before the captain could regain full control. The left float detached upon impact with water, the aircraft bounced, the right hand float detached on second touch down, the right float became trapped between fuselage and engine for some time.
The captain initiated the evacuation of the aircraft, all passengers and crew were able to escape through the left passenger door before the aircraft became completely submerged. A number of people at the Kuredo jetty observed the accident, a boat at the jetty started out to the accident site and arrived about 5 minutes after the impact. Another boat arrived a short time later, the boats collected all 11 passengers and 3 crew, all of them wearing their swim vests and took them to Kuredo jetty.
The aircraft continued to sink, flipped over left and sank to the bottom of the sea 36.5 meters below the water surface.
The aircraft sustained substantial structural damage including the right hand wing strut being bent. The engines were damaged beyond economic repair.
The aircraft was recovered from the seabed. The investigation found no anomalies with the flight controls.
The stall warning sensors were found intact and without anomalies, however, the stall warning horn had been de-activated although required to work. The MCAA wrote: "It was understood later that it was deactivated primarily due to false activations of the stall warning system distracting the flight crew during the landing and take-off phases, which is inherent in the Wipaire 13000 floats installation. This modification, which alters the Type Certificate of the aircraft, was not approved by the relevant Certifying Authorities. However, the CAA was made aware, in writing, of the deactivated condition since September 2014, and updated through regular updates."
The investigation determined that at the time of landing the Center of Gravity was located at 36% MAC, the forward limit for the CG was 25% MAC and the aft limit 32% MAC, the landing weight was estimated at 10,927 lbs.
The MCAA analysed:
The take-off from Komandoo was normal without any problems and the pilots did not report any difficulties en-route to Kuredu. There was no evidence within the wreckage (or in subsequent tests) of any significant aircraft defect. Meteorological information covering Kuredu area was not available despite requirements under MCAR-OPS 1 to have weather information at intended landing sites. The company’s Operations Manual permits Dispatch to inform crew about destination conditions prior to a flight. No adverse weather conditions were reported.
Crew reports indicate that the aircraft started to pitch up at an approximate altitude between 400 – 300 feet, immediately after the flap controls were moved to the fully down position (37.5°).
Initial investigation was focused on any mechanical failures that could have prevented the normal operation of the aircraft. The investigation identified no failures that could have prevented the normal operation of the aircraft. The investigation team also examined the floats but did not find any pre-existing defects that could have caused leaks. The investigation then moved on to the analysis of the aircraft’s mass and balance as a significant amount of baggage was found in the aft cargo compartment. Calculation of the aircraft’s mass and balance, based on the distribution of passengers and baggage, showed that the weight was within the approved limits but the centre of gravity position was significantly aft of the approved limits before the aircraft left Komandoo.
Consequently, there can be no doubt that this accident was triggered by operating the aircraft outside the Centre of Gravity limitations. The error went undetected at the time of departure from Komandoo because the crew did not ensure the aircraft Centre of Gravity was within limits.
With respect to the recovery attempt the MCAA analysed:
The flight characteristics described by the flight crew from the time the co-pilot stated she was unable to control the aircraft, to the time the aircraft crashed, bear the hallmarks of a stall. The pilot flying was, however, unable to determine the aircraft was going into a stall and handed over the controls to the PIC. The PIC interpreted the flight characteristics as those of a spin and applied the spin recovery procedures.
The PIC applied full left rudder, moved the control column forward and put the power levers to idle. These proved ineffective as the loss of engine power would reduce thrust and speed aggravating the stall condition. The nose of the aircraft thus continued to rise. The PIC, then moved the flaps to the fully up position where a measure of control was gained.
With respect to the stall warning the MCAA analysed:
It is not clear why the PIC did not react to the stall warning light that illuminated and the unusually nose up attitude of the aircraft and subsequent buffeting before the PF asked him to take over the controls. It is common that the stall warning (light and horn) activates at both the take-off roll and touch down during the landing phase. The flight crew are accustomed to this but should have recognised the warning light illuminating while still in flight. However, had the aural warning been active this would have made the crew become alerted to take corrective action in time.
With respect to emergency response the MCAA analysed:
The crash was seen by four people at Kuredu jetty (which included a TMA pilot and cabin crew) and immediately took on a launch to rescue any survivors. The passengers were rescued before any planned emergency response can take effect.
ASC 14-2 paragraph 11 requires a standby boat at least 200 m away from the floating platform when the aircraft is ready to land. Further paragraph 15 requires a trained firefighting and rescue agent to be in attendance on the boat at any landing. This standby boat was not at the platform at the time of the accident.
This article is published under license from Avherald.com. © of text by Avherald.com.
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