Montserrat BN2P at Antigua on Oct 7th 2012, lost height after takeoff, contaminated fuel
Last Update: October 16, 2015 / 15:47:54 GMT/Zulu time
The airline confirmed the aircraft crashed shortly after takeoff, one passengers survived with critical injuries, the pilot and 2 passengers have died. The United Kingdom's AAIB is investigating the accident.
Police initially reported a British couple, passengers of the flight, had died in the accident, two people were taken to the hospital in critical condition. The pilot later succumbed to his injuries.
A preliminary report released by the East Caribbean Civil Aviation Authority on Oct 13th 2012 states, that the aircraft yawed to the right shortly after becoming airborne and stopped climbing while rolling to the right. The aircraft subsequently lost height and impacted ground right wing tip first at low forward speed and cart wheeled before coming to rest in an upright position. The fuselage section forward of the wing was destroyed, the rest of the aircraft sustained comparately less damage. The pilot (31, CPL, 710 hours total, 510 hours on type) and two passengers were killed, another passenger survived with serious injuries. Examination of the wreckage showed that the right hand engine was not producing power at the time of impact, investigation of the fuel system showed contamination with significant quantities of water. The right hand propeller was not feathered.
On Oct 16th 2015 the British AAIB released the final report by the Eastern Caribbean Civil Aviation Authority (ECCAA) concluding the probable causes of the crash were:
- Significant rainfall, and anomalies in the aircraft’s fuel filler neck and cap, led to the presence of water in the right-hand fuel tank
- Shortly after takeoff, the water in the right-hand fuel tank entered the engine fuel system causing the engine to stop running
- Control of the aircraft was not retained after the right-hand engine stopped
The investigation identified the following contributory factors:
- No pre-flight water drain check was carried out; such a check would have allowed the presence of water in the right-hand fuel tank to be detected and corrective action taken
- It is possible that performance-reducing windshear, encountered during the downwind departure, contributed to a reduction in airspeed shortly before the aircraft stalled
The ECCAA reported that the pilot and a passenger died on the spot, a second passenger succumbed to her injuries before she could be recovered from the wreckage, and the third passenger was recovered with serious injuries and survived.
The ECCAA reported the aircraft departed with a takeoff mass of 5,540 lbs below the structural limit of 6,600 lbs. The aircraft entered runway 07 at taxiway B and did not backtrack. Ground observers did not notice any power checks (the ECCAA annotated that power checks routinely were not carried out except for the first flight of the day).
Ground witnesses observed the aircraft initially depart normally reaching a height of about 200-300 feet then appeared to sink a small amount without yawing or rolling followed by a right yaw, a subsequent right roll, the nose pitched down and the aircraft entered a right spin.
The surviving passenger recalled, that the stall warning activated in the cockpit and a red light activated at that time, both remained active until impact.
The aircraft was flown by a sole pilot (31, CPL, 710 hours total, 510 on type). After obtaining a Transport Canada issued CPL the pilot had flown for another operator from December 2011 to April 2012. The ECCAA summarized the operator's comments: "When questioned about the pilot’s performance, the operator’s accountable manager stated that the pilot was ‘very inconsistent’ and that the weak areas in his performance were ‘maintaining airspeed and directional control’. In particular, ‘on departure and final approach… airspeed will bleed to critical levels without him noticing’."
Fly Montserrat reported that they had not observed any anomaly with the performance of the pilot.
The aircraft, built in 1969, had accumulated 22,064 flight hours in 55,851 flight cycles. It had last undergone maintenance, a hundred hour inspection, on September 11th 2012 and a maintenance action on Sep 29th 2012, when the left hand fuel filler cap had departed the aircraft during takeoff from Antigua, the loss was discovered after arrival in Montserrat, the filler cap was subsequently recovered from the runway but was found damaged to an extent that it could not be reinstalled on the aircraft. On Oct 3rd 2012 a replacement filler cap was installed.
Maintenance records also indicated that the left fuel filler cap had to be replaced in Nov 2010 after it had leaked water into the fuel tank.
No maintenance record regarding the right filler cap was found, the ECCAA wrote: "which suggested that it may have been on the aircraft at least since November 2009."
Prior to the accident departure of the aircraft there had been a thunderstorm over Antigua aerodrome with light rain, reported at 16:00L (20:00Z). In a special weather observation on 16:32L (20:32Z) following the accident it was noted, that the thunderstorm and light rain ceased at 20:12Z.
The ECCAA analysed: "The examination of the aircraft wreckage revealed that the fuel filler caps in use on the aircraft were of the type designed to be used with Modification NB/M/477. However the filler necks were of the pre-modification standard and retained the original adapter plates (on the right tank, at least) and rainwater drain channels. During the course of the investigation no examples of the earlier type of fuel cap were seen, which probably reflected the fact that these components had been out of production for many years. Although the caps appeared to fit satisfactorily, it was found that the right tank cap did not always seal properly, with corrosion on the adapter plate possibly contributing to this condition. A simple experiment indicated that water could leak past the cap seal and into the tank, although the leakage rate tended to vary each time the cap was re-seated such that it was sometimes possible to achieve an effective seal. On the left tank, a non-approved modification had been conducted in which the adapter plate had been fashioned from stainless steel; however the smooth surface had resulted in an effective seal."
The ECCAA continued analysis: "The examination of the aircraft fuel system confirmed that the right engine had stopped due to the presence of a significant quantity of water. Earlier in the day of the accident the aircraft had arrived from Montserrat and had been refuelled from a bowser. It had then been parked outside during a period of heavy rain, with the airport rain gauge recording 42 mm of rainfall in two hours. A sample from the refuelling bowser was found to be free from water contamination; furthermore there were no reports of problems occurring on other piston engine aircraft operating out of Antigua. It is thus reasonable to conclude that the water entered the fuel tank during the period the aircraft was parked in heavy rain."
The ECCAA continued: "In the case of VP-MON, the variable efficacy of the fuel right tank fuel cap seal would have led to water periodically entering the tank, although it is likely that this could have been removed by the daily water drain checks. The fact that the Technical Log page for the day of the accident did not display a signature for the daily Check ’A’ (which would have included the water drain check) raises the possibility of the check being omitted. However, the aircraft flew without problem from Montserrat to Antigua earlier in the day, indicating that either there was no water or there was insufficient quantity to be drawn into the fuel system. It was therefore concluded that a combination of the heavy rainfall and a relatively high leakage rate past the fuel cap resulted in a significant quantity of water entering the right fuel tank."
The ECCAA analysed that the water was not present in the fuel line, otherwise the aircraft would not have become airborne before the engine began to fail. It was therefore "more probable that the water was drawn into the fuel line as the aircraft rotated to the takeoff attitude."
The ECCAA analysed the operational aspect of the accident flight:
The presence of a cumulonimbus cloud on the approach to Runway 07 had caused the air traffic controllers on duty to select Runway 07 for departures, although aircraft taking off would experience a tailwind.
Either windshear associated with the cumulonimbus cloud, or the wind gradient, may have caused the accident aircraft to experience performance-reducing shear in its climb, as it flew from relatively weaker westerly winds at the surface into relatively stronger winds aloft. The description, by some eyewitnesses, of the aircraft appearing to ‘sink’ before it rolled and yawed, would be consistent with a performance-reducing shear. An into-wind takeoff would have reduced the probability of performance-reducing windshear.
The witness accounts and evidence from the accident site combine to indicate that during the aircraft’s initial climb, the right-hand engine ceased producing power. This may have occurred just after, or during, the effect of any windshear. No evidence suggested that the pilot had attempted to secure the failed engine or feather its propeller; if these actions had been completed and control of the aircraft retained, continued flight to a safe landing would have been a possibility.
TAPA 072200Z VRB02KT 9999 TS FEW012CB 25/24 Q1013
TAPA 072100Z VRB02KT 9999 FEW012CB 25/23 Q1013
TAPA 072032Z 26009KT 9999 FEW012CB SCT034 24/22 Q1012
TAPA 072000Z 19012KT 6000 -TSRA FEW012CB SCT013 24/22 Q1013
TAPA 071945Z 16014KT 2000 -TSRA FEW012CB BKN013 24/22 Q1013
TAPA 071900Z 03008KT 2000 +TSRA FEW012CB BKN013 24/22 Q1013
TAPA 071820Z 06012KT 9999 -TSRA FEW012CB BKN015 29/24 Q1012
TAPA 071800Z 13012KT 9999 BKN016 29/24 Q1012
This article is published under license from Avherald.com. © of text by Avherald.com.
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