TMA DHC6 at Finolhu on Nov 13th 2021, right wing damage during water takeoff
Last Update: March 21, 2023 / 18:21:01 GMT/Zulu time
Date of incident
Nov 13, 2021
TMA Trans Maldivian Airways
De Havilland DHC-6 Twin Otter
ICAO Type Designator
The aircraft was seen at the mooring at Finolhu in the evening of Nov 16th 2021 (see photos below) having suffered a dent and penetration to the leading edge of the right hand wing as well as the right hand propeller being removed and the right hand engine supported by a crane, works going on on the wing and prop/engine.
According to ground observers at Finolhu the aircraft collided with a water bungalow during its takeoff run and received damage to its right hand wing.
A ground observer reported the aircraft underwent engine and propeller tests on Nov 17th 2021, obviously after an engine change, the two tears at the right hand wing were patched up, the aircraft subsequently departed Finolhu.
The aircraft positioned from Finolhu to Male on Nov 17th 2021 and is still on the ground in Male about 5 hours after landing there.
On Dec 10th 2021 the Maldives AICC (Accident Investigation Coordinating Committe) released their preliminary report summarizing the sequence of events:
Aircraft daily inspection was carried out on 12 November 2021, and there was no record of any open deferred defects listed in the Aircraft Technical Log (ATL).
The incident flight was operated by the PIC who was seated on the right seat as it was intended for a training flight for the other crew member. According to the flight crew, no abnormalities were observed in any of the previous flights and on this flight until the aircraft failed to produce sufficient lift for take-off and subsequently the take-off was aborted. As the crew were unable to move the power levers to the reverse position, the crew decided to shutdown both engines.
The aircraft moved forward under momentum even after the engines were shut down and collided with water bungalows. As a result of the collision, both the aircraft and the bungalows sustained damages. The RH propeller, RH wing tip and the LH wing were damaged.
The aircraft was towed back to the platform by a dinghy.
The commander (44, ATPL, 14,706 hours on type) was seated in the right hand seat providing training to the first officer (34, CPL, 4,851 hours on type) in the left hand seat, the commander was pilot flying. The AICC stated: "A Mass and Balance Report produced by the Flight crew before departure was available on the tablet. For both the take-off and landing, the CG remains within limits."
The AICC stated to the meteorologic conditions:
There was no recorded weather data available at the Finolhu water aerodrome, and the nearest was recorded data was available from Dharavandhoo automatic weather station, which is approximately 25km north-east of Finolhu water aerodrome. At 17:10 hrs on 13 November the weather data was mean winds at 24.5 mph (gusting 30.6 mph) from WSW direction.
A weather alert over Baa Atoll was active from 1700 to 1800 hrs on 13 November 2021. A yellow alert was issued at 15:40 hrs on 13 November 2021 suggesting strong winds of 25 -30 mph and gust s of 40mph with rough seas expected.
The AICC stated in their iniital findings that the aircraft became airborne for a few seconds.
On Mar 21st 2023 the AICC released their final report concluding the probable causes of the serious incident were:
a. The take-off direction was inappropriate as the take-off line passes over the water bungalows;
b. The crew were unable to apply reverse power after rejecting the take-off;
c. The crew were unable to shutdown the engines in a timely manner;
d. The crew were unable to turn the aircraft away from the bungalows;
The AICC stated:
The wing and the right hand propeller sustained minor damages, as detailed
1. Left Wing leading edge dented in three places
2. Right Wing tip fairing damaged
3. Right propeller – One blade damaged
The AICC analysed:
The aircraft attempted to take-off in a North Westerly direction towards a stretch of water bungalows. During the take-off run the aircraft was momentarily airborne and the aircraft settled back on water, the PIC decided to abort the take-off.
The crew then attempted to apply engine reverse power to stop the aircraft forward movement, but despite repeated attempts, they were unable to select engine reverse power and hence engaged the fuel shut-off valves to shut down both the engines. In spite of shutting down the engines, the aircraft moved on its own momentum and came in contact with two water bungalows.
The PIC who was the PF, stated that the weather was below favorable conditions at the time of the incident. He noted that on the incident flight the most favorable take-off path would have been a westerly direction as the wind was from WSW. However, in order to avoid taking-off towards the island or between the island and the water villas (over the walkway between the island and the water villas) the PIC chose a north westerly direction towards the water bungalows (having an approximate height of 7.2 meters above mean sea level). The PIC confirmed that once airborne, he was hoping to level off and turn right slightly and climb out to avoid flying over the water bungalows.
For the selected take-off path, the distance from the point where the take-off was seem to initiated up to the water villa with which the aircraft contacted was approximately 2260 ft.
The Crew had the option of selecting other paths for take-off. Had the crew moved further out (north-east) before lining up for take-off, where adequate take-off distance was available, ensuring clearance from the water bungalows. Thus, the decision taken by the PIC to initiate the take-off run from where he did, instead of taxiing out further north-east, is construed as a contributing factor.
The G950 (Garmin G950 flight management system) data suggests the aircraft lifted off within 23 seconds into the takeoff run and the aircraft appeared to be off the water for about 3 seconds covering a distance of about 164 feet. When the aircraft settled back on water, the aircraft was approximately 750 feet from the water villas.
The PIC recalls that as soon as the aircraft was airborne, an unfavorable gust of wind caused the aircraft to settle back on water. The G950 data also indicated that, at around the same time, engine power on both engines was reduced to idle thus indicating the take-off was aborted at that point.
According to both the crew members, while rejecting the take-off, the PIC moved the power levers to ground idle, but was unable to move the power levers to the reverse position. The PIC stated that three attempts were made to move the power lever aft of the gate position, while verbally calling out his actions. The FO suggested to shut off the fuel but the PIC decided and advised the FO to try and engage the reverse as the situation could be brought under control once the reverse power is applied. Hence a fourth unsuccessful attempt was made to engage reverse power. The PIC finally permitted the FO to shut off the fuel and subsequently propeller blades were feathered.
Immediately after the propeller blades were feathered, the aircraft veered further towards left and continued to move forward, under momentum, until the aircraft came in contact with the water villas in front.
Failure to move the power levers aft of the gate position could be attributed to the following two main reasons:
1. The position of both propeller levers not at full forward (fully fine) position would mechanically lock the power levers at the flight idle position (also known as gate position); hence the power levers cannot be moved aft of the idle position. (TMA Operations Manual Part B – Vol I float Operation Issue 2 Rev 4 dated 11 Jul 2017, under 188.8.131.52 – Landing Procedures – under clause 15, a caution states that the reverse power cannot be applied unless BOTH the propeller levers are at full forward position) The power lever linkage is designed to mechanically lock the power lever being pulled aft of the flight idle position whenever any one of the propeller levers is not fully forward.
2. If the crew operating the power lever fails to twist the power lever grips to overcome the mechanical stop while attempting to reverse, the power levers will not move beyond the mechanical stop.
During the investigation, both the power levers and propeller levers were checked for full and free movement and both power levers and both the propeller levers were found to be functioning satisfactorily with no mechanical failures or restrictions. . The LH engine was run and when reverse was selected, the engine responded accordingly. The RH engine was not run due to damages on the propeller blade. The operation ruled out any mechanical malfunction of the power levers.
At the time of rejecting the take-off, the Np of both the propellors were below the maximum which indicated that the propellor levers were not fully forward. The propellor levers may have moved back due to aircraft bumping on waves during the take-off run in the rough weather. Experience of the operator has shown that the propellor levers move back during bumpy takeoff
uns. In this occurrence, it would appear that the propellor levers have moved back from the fully forward position as indicated by the propellor Np values.
Hurry-Up Syndrome is defined as any situation where a pilot's human performance is degraded by a perceived or actual need to hurry or rush tasks or duties for any reason. These time-related pressures include the crew desire to meet a restriction in clearance time, the pressure to keep on schedule when delays have occurred due to weather, or the inclination to hurry to avoid exceeding duty time regulations, and many other situations.
It was noted that the crew had strong concerns relating to completing last scheduled flight of the day from MLE to Rangali island before the twilight ends. Crew were also aware of the unfavorable weather situation and its potential to delay the impending take-off and the possibility that they may not make it to the final destination for the night before twilight ends. Considering nearing completion of a very long day, it can be deduced that crew performance would have tended to wane.
Based on the above twilight end time the crew would have 61 minutes from the time of the incident, which occurred at 17:11 hrs, to complete the last flight before twilight ends.
The shortest possible flight distance (straight line) from FIN to MLE is 60.48 nm and the distance from MLE to Conrad Maldives water aerodrome is 59.83 nm. To cover both flights approximately 61 mins of flying time is required based on average cruising speed of 120 knots. This does not include any air traffic delays and the turnaround time at MLE.
Considering the circumstances, the crew appear to be under pressure to return to main base and complete the last flight of the day to Conrad Maldives water aerodrome at Rangali island, Alif Dhaalu atoll. There was very limited time left to complete both the flights before the twilight ends in Rangali island, and therefore it is highly likely that the ‘Hurry-up syndrome’ would have contributed to this incident.
Date of incident
Nov 13, 2021
TMA Trans Maldivian Airways
De Havilland DHC-6 Twin Otter
ICAO Type Designator
This article is published under license from Avherald.com. © of text by Avherald.com.
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