Incident Overview

Date: Friday 8 March 1968
Aircraft Type: Fairchild F-27
Owner/operator: Air Manila International
Registration Number: PI-C871
Location: ca 2 km N off Ibajay – ÿ Philippines
Phase of Flight: En route
Status: Destroyed, written off
Casualties: Fatalities: 14 / Occupants: 14
Component Affected: Right-hand outer wingRight-hand outer wing
Category: Accident
Air Manila Flight 507 experienced a significant incident due to severe thunderstorm conditions. The aircraft deviated 10 nautical miles right of the airway to avoid the hazardous weather, leading to a sudden and unexpected encounter with a developing cumulonimbus cloud. This cloud, initially appearing as a minor buildup, rapidly escalated into a fully developed cumulonimbus, causing a loss of control and subsequent fire. The aircraft flew at a high speed, exceeding recommended turbulent air operating speed, resulting in structural failure.Air Manila Flight 507 experienced a significant incident due to severe thunderstorm conditions. The aircraft deviated 10 nautical miles right of the airway to avoid the hazardous weather, leading to a sudden and unexpected encounter with a developing cumulonimbus cloud. This cloud, initially appearing as a minor buildup, rapidly escalated into a fully developed cumulonimbus, causing a loss of control and subsequent fire. The aircraft flew at a high speed, exceeding recommended turbulent air operating speed, resulting in structural failure.

Description

Air Manila Flight 507 departed Manila (MNL) at 18:14 for a flight to Mactan at FL130. Thunderstorms existed along the route and the crew probably deviated some 10nm right of the airway to avoid the hazardous weather. It was believed that the aircraft suddenly flew into a hidden cumulonimbus that may have appeared as a minor build up, but which was actually a fully developed and active cumulonimbus. Air loads associated with a sudden pull up manoeuvre, combined with gust loading probably caused both horizontal stabilizers to fail. The right-hand outer wing then failed due to air loads generated by a high angle of attack. The F-27 then went out of control and the fuel, escaping from the ruptured fuel tanks, ignited. The aircraft was flown at 180 knots, 40 knots more than recommended turbulent air operating speed. Parts of the aircraft fell into the sea, just offshore. PROBABLE CAUSE: “In-flight structural failure due to air loads exceeding the design strength, while flying in a thunderstorm cell.”

Primary Cause

In-flight structural failure due to air loads exceeding the design strength, while flying in a thunderstorm cell.In-flight structural failure due to air loads exceeding the design strength, while flying in a thunderstorm cell.

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