Unstabilized Approach Leads to Aircraft Ground Impact in Papua

Casualties unknown • Bilai Airstrip, Papua, ID

A PAC 750 XL cargo flight experienced a heavy landing and subsequent excursion at Bilai Airstrip, resulting in significant aircraft damage but no injuries.

What happened

On 04 February 2012, a PAC 750 XL aircraft, registration PK-BSA, was conducting an unscheduled cargo flight from Nabire to Bilai, Papua. The flight, operated by Ersa Eastern Aviation, was the second leg of the day's operations. After a successful initial flight, the aircraft was reloaded with 1,100 kg of cargo, including six drums of diesel fuel.

During the approach to the Bilai airstrip, the aircraft maintained an altitude of approximately 5,757 feet before a slight increase in engine power caused the aircraft to climb to 5,764 feet. Upon touchdown, the aircraft experienced two bounces. Following the impact, the aircraft veered to the left, despite the pilot's attempts to maintain the centerline using braking and power reverse. The aircraft eventually struck a hillside, causing the nose gear to sink into the mud and the propeller to strike the ground. The incident resulted in no injuries to the two crew members on board, but the aircraft sustained significant damage, including a broken left flap, a torn left upper wing skin, and a displaced left main landing gear.

The investigation

The investigation examined engine trend monitoring data and witness accounts from the maintenance engineer on board. Analysis of the engine parameters revealed that during the final approach, the aircraft was in a configuration that made it difficult to manage descent rates effectively. Data indicated that the aircraft was descending at approximately 1,100 feet per minute, which is significantly higher than the standard 500 feet per minute for this model.

Furthermore, the investigation noted that the engine power and propeller settings were not optimized for the descent, which likely contributed to a heavy landing. The monitoring data also showed that the propeller RPM dropped to zero after striking the ground, and the engine shut down approximately nine seconds after the impact.

Findings

  • The approach was unstabilized, characterized by a high descent rate and an approach path that leveled with the runway before climbing.
  • The aircraft experienced two bounces during the touchdown phase.
  • The aircraft veered left after the initial impacts, leading to the propeller striking the ground and the nose gear entering the mud.
  • The aircraft was configured with engine parameters that reduced responsiveness to attitude changes during the descent.

Probable cause

The primary cause of the incident was an unstabilized approach, involving a high descent rate and improper engine configuration, which led to a heavy landing, multiple bounces, and a subsequent runway excursion.

Frequently asked questions

What happened in the 2012-02-04 PAC 750XL accident near Bilai Airstrip, Papua, ID?

A PAC 750 XL cargo flight experienced a heavy landing and subsequent excursion at Bilai Airstrip, resulting in significant aircraft damage but no injuries.

What aircraft was involved and where did it happen?

The accident on 2012-02-04 involved a PAC 750XL, registration PK-BSA, operated by Ersa Eastern Aviation, at Bilai Airstrip, Papua, ID.

What was the probable cause of the accident?

The primary cause of the incident was an unstabilized approach, involving a high descent rate and improper engine configuration, which led to a heavy landing, multiple bounces, and a subsequent runway excursion.

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