Takeoff (climb)

Engine failure for unknown reasons.

The accident occurred in poor weather conditions. It was determined that during initial climb, the aircraft's attitude, speed and altitude varied suddenly and rapidly, causing the pilot flying a stressful situation insofar as he believed that artificial horizons presented technical problems. In such a situation, investigators consider probable the hypothesis that the pilot made inadequate corrections, exacerbating the abnormal situation in which he was operating. The following contributing factors were identified:
- The crew were suffered fatigue because they had been on duty for more than 15 hours and were unable to observe satisfactory rest time at Congonhas airport,
- This fatigue certainly affected the pilots in their decision-making,
- The urge to return home and distrust of instruments in difficult flight conditions seriously compromised the performance of pilots and their ability to make decisions,
- A direct contact with passengers was stressful as they were going through a period of mourning and were eager to return home to Maringá,
- Weather conditions were unfavorable and contributed to the anxiety of the crew,
- Poor assessment of these conditions by the pilots,
- The working time of the pilots exceeded the limitations and the operator did not take into account adequate rest conditions for the crew,
- The training of the captain in instrument flights in recent months was insufficient.

Improper rigging of both propeller assemblies by maintenance personnel, which resulted in the inadvertent feathering of both propellers after takeoff. Factors included a lack of rigging experience in airplane make and model by maintenance personnel, unclear maintenance manual information, and unsuitable terrain for the forced landing.

The following findings were identified:
- There are no signs of engine failure prior to the impact,
- The aircraft exceeded its manufacturer's MTOW on the flight from Datah Dawai to Samarinda,
- The aircraft center of gravity is near the aft limit of the CG flight envelope,
- The PIC apparently has a wrong perception on takeoff procedure. He thought that the optimum takeoff performance could be achieved by taking-off with a higher velocity. Meanwhile, in achieving high velocity one has to roll closer to the obstacle, which forced the aircraft to maintain a higher rate of climb,
- The PIC and Datah Dawai ground crews have endangered his passengers by letting more passengers loaded into the aircraft than the number of seats available,
- The PIC and Datah Dawai ground crews have endangered their passengers by improperly calculating the weight of aircraft payload,
- The operator did not have proper supervision system that may prevent such practice to happen,
- The operator has never filled out Flight Clearance, for its Samarinda - Datah Dawai operation,
- There are a lot more passengers or demand than the capacity of the Pioneer Flight Samarinda - Datah Dawai,
- There are not enough flight operation documents published (such as visual track and single engine emergency return guidance) to fly safely in and out of Datah Dawai,
- The exceeding MTOW, small stability margin, PIC takeoff habit, and lack of published safety documents for the area are the contributing factors to the accident.
There were found indications of practices that fit into the category of negligence, willful misconduct and violations of existing flight safety rules and regulations.

It is believed that the loss of control was the consequence of the failure of the left engine during climbout. The exact cause of the engine failure remains unknown but discrepancies were noted concerning operations, manifest and W&B documents (fuel and pax). Since last October 31, all Antonov AN-24, AN-26 and AN-32 flights were suspended in all Angolan airspace, except on the route Luanda - Namibe.

The indicated failure of the right hand AC bus during takeoff with low ceiling. The factors were the low ceiling, night, and the excessive workload the pilot experienced on takeoff with an electrical failure without a second in command.

It was determined that one of the tyres on the nose gear burst during the takeoff roll.

Findings as to Causes and Contributing Factors:
1. A planetary gear disintegrated in the propeller reduction gearbox of the No. 2 engine and caused the engine drive shaft to disconnect from the propeller, resulting in a loss of propulsion from this engine.
2. The planetary gear oil strainer screen wires fractured by fatigue as a consequence of the installation at the last overhaul. This created an unsafe condition and it is most probable that the release of wire fragments and debris from this strainer screen subsequently initiated or contributed to distress of the planetary gear bearing sleeve and resulted in the disintegration of the planetary gear.
3. Although airspeed was above Vmc at the time of the power loss, the aircraft became progressively uncontrollable due to power on the remaining engine not being reduced to relieve the asymmetric thrust condition until impact was imminent.
Findings as to Risk:
1. The propeller reduction gearboxes were inspected in accordance with the West Coast Air maintenance control manual. These inspections exceeded requirements of the de Havilland Equalized Maintenance Maximum Availability program. Since the last inspection, 46 hours of flight time before the accident, did not reveal any anomaly, a risk remains of adverse developments with
resulting consequences occurring during the unmonitored period between inspections.
2. Regulations require the installation of engine oil chip detectors, but not the associated annunciator system on the DHC-6. Without an annunciator system, monitoring of engine oil contamination is limited to the frequency and thoroughness of maintenance inspections. An annunciator system would have provided a method of continuous monitoring and may have warned the crew of the impending problem.
3. Although regulations do not require the aircraft to be equipped with an auto-feather system, its presence may have assisted the flight crew in handling the sudden loss of power by reducing the drag created by a windmilling propeller.
4. Since most air taxi and commuter operators use their own aircraft rather than a simulator for pilot proficiency training, higher-risk emergency scenarios can only be practiced at altitude and discussed in the classroom. As a result, pilots do not gain the benefit of a realistic experience during training.
Other Findings:
1. The fact that the aircraft remained upright and floating in daylight conditions contributed to the successful evacuation of the cabin without injury and enabled about half of the passengers to locate and don their life vests.
2. The aircraft was at low altitude and low airspeed at the time of power loss. The selection of full flaps may have contributed to a single-engine, high-drag situation, making a successful landing difficult.