Cessna 208 Caravan I – 5N-PAN

Incident Overview

Date: Wednesday 25 November 1998

Aircraft Type: Cessna 208 Caravan I

Owner/operator: Pan African Airlines

Registration Number: 5N-PAN

Location: Warri – ÿ Nigeria

Phase of Flight: Approach

Status: Destroyed, written off

Casualties: Fatalities: 0 / Occupants: 2

Component Affected: Bypass valve in the engine.Bypass valve in the engine.

Investigating Agency: AIPBAIPB

Category: Accident

A chartered flight from Lagos (LOS) to Warri involving a Cessna Caravan (5N-PAN) experienced a significant incident during descent and approach. The aircraft initially cleared to 1,000ft, then called Lagos Approach, which cleared it to 3,500ft with instructions to report at TMA. The pilot initiated a descent to 700ft, then switched to a normal flight path, ultimately reducing speed to 120 knots and selecting gear down with flap 15ø. Approximately 5 nautical miles from Warri, the pilot reduced speed to 120 knots and selected gear down with flap 15ø, experiencing a shudder and subsequent power loss. The pilot then retracted flaps and feathered the propeller, subsequently re-selected flap 30ø and unfeathered the propeller to restore engine torque. The pilot, driven by a visual obstruction of a building structure ahead, veered off the approach path, resulting in a skid into swampy terrain. The probable cause was a fractured cotter pin within the bypass valve of the engine, causing a malfunction that resulted in a partial flameout, sustaining idle running of the engine.A chartered flight from Lagos (LOS) to Warri involving a Cessna Caravan (5N-PAN) experienced a significant incident during descent and approach. The aircraft initially cleared to 1,000ft, then called Lagos Approach, which cleared it to 3,500ft with instructions to report at TMA. The pilot initiated a descent to 700ft, then switched to a normal flight path, ultimately reducing speed to 120 knots and selecting gear down with flap 15ø. Approximately 5 nautical miles from Warri, the pilot reduced speed to 120 knots and selected gear down with flap 15ø, experiencing a shudder and subsequent power loss. The pilot then retracted flaps and feathered the propeller, subsequently re-selected flap 30ø and unfeathered the propeller to restore engine torque. The pilot, driven by a visual obstruction of a building structure ahead, veered off the approach path, resulting in a skid into swampy terrain. The probable cause was a fractured cotter pin within the bypass valve of the engine, causing a malfunction that resulted in a partial flameout, sustaining idle running of the engine.

Description

A float-equipped Cessna Caravan, 5N-PAN, departed Lagos (LOS) on a chartered flight to Warri with a scheduled stop-over at Lekki. The aircraft was airborne at 07:34 hours UTC and was cleared to 1,000ft by Lagos Tower and landed at Lekki at 07:42 hours UTC. At 08:20 hours UTC, the aircraft departed Lekki and called Lagos Approach which cleared it to 3,500ft with further instructions for the aircraft to report at TMA. The aircraft reported at TMA and continued its normal flight at 3,500ft. On contact with Escravos Tower, it requested for a descent from 3,500ft to 700ft in order to over-fly the Chevron facility at Opuekaba for an aerial inspection. After the inspection, the aircraft was cleared to 2,500ft to resume its normal flight to Warri. The pilot made an out-bound turn to line up for the final approach to runway 03. At about 5 nm DME from Warri the pilot chose to reduce speed to 120 knots and he selected gear down with flap 15ø. At 3 nautical miles out, the aircraft was about 900 feet high above the approach path, and cleared to land. The aircraft was now configured for landing with flap at 30ø and the pilot reduced the speed to between 85 and 90 knots. At about 1.5 miles out, the aircraft was between 350 – 400ft high, gliding with 400 lb of torque, the pilot felt a small shudder from the engine which was instantaneously followed by a need for power input, so he advanced the throttle but there was no response from the engine. He quickly retracted the flaps and feathered the propeller. Then the pilot re-selected flap 30ø and also unfeathered the propeller which restored the engine to full torque. The pilot decided to abandon the approach mainly because of the a building structure ahead, close to the runway threshold. The pilot chose to veer the airplane to the left of the approach path centerline and ditched into the swampy terrain, cutting through some scattered trees and shrubbery. PROBABLE CAUSE OF THE ACCIDENT: “The probable cause of the accident was the little old fractured cotter pin which lodged itself in the orifice and caused the BOV to malfunction at the very critical instance when more power output was demanded from the powerplant. The engine did not completely flameout, because of the position of the BOV valve in partially/fully open position which, could only sustain idle running of the engine.”