History of the Flight
On 1 May 2003 at 16:30 UTC, a Jabiru SK ultralight, registration CS-UJB, departed from runway 30 of Lagos Municipal Aerodrome. The aircraft was part of a group of four similar airplanes returning to Lezírias airfield. Immediately after takeoff, the pilot initiated a left turn and reported via radio that the engine cowl had opened in flight, necessitating a return to the runway. A witness, pilot of the second aircraft, observed the downwind leg at approximately 300 ft AGL, noting the circuit appeared tighter than normal. During the left turn to final, the aircraft stalled, rolled to the right, and collided with the ground near a residential area at coordinates 37°07′009″N, 008°40′35″W.
Injuries and Fatalities
Both occupants died. The pilot, a 54-year-old male with 555 hours total flying time (17 hours in the last 90 days), succumbed to traumatic injuries five days after the accident. The passenger died immediately from blunt force trauma, as confirmed by autopsy reports.
Aircraft Damage
The aircraft was destroyed. The engine cowl was found approximately three meters ahead of the main wreckage, damaged on the right forward side by the propeller. The two side latches were intact, closed, and with their safety pins inserted. The right wing was damaged at the root and tip, and the right main landing gear leg was deformed. Two pieces of the propeller were separated.
Meteorological Conditions
Weather was good with wind from 310° at 10–12 knots.
Aerodrome Information
Lagos Municipal Aerodrome is approved for ultralight operations. Runway 12/30 measures 560 by 30 meters. A hill with power lines lies 600 m from threshold 30.
Medical and Pathological Information
The pilot's autopsy determined death due to traumatic injuries from the accident. The passenger's autopsy attributed death to blunt force trauma.
Fire
No fire occurred, but firefighters applied foam to prevent ignition due to fuel spillage.
Survival Aspects
The pilot was found outside the aircraft with his seatbelt open; he was transported to Portimão hospital and later evacuated to São José Hospital in Lisbon, where he died five days post-accident. The passenger remained inside the aircraft, restrained by the seatbelt, and required extrication.
Examination of Cowl Latching System
The engine cowl is removable and secured by two side latches, each engaging with a hook on the airframe. Each latch incorporates a safety pin to prevent inadvertent opening. The investigator found that while the design normally prevents in-flight opening unless the pin or hook fails, it is possible to insert the safety pin without the latch being fully closed.
Stall Characteristics
Stall tests conducted on a similar Jabiru SK showed that with 40° flaps and power reduced, stall buffet was minimal with no significant wing drop tendency. With flaps retracted, maximum power, and full aft stick, the aircraft stalled gently while yawing right. In turning stalls with 30° bank left and power on, the aircraft tended to roll right into a descending spiral.
Probable Cause
The primary cause was loss of control during the turn to final. An accessory cause was the in-flight opening of the engine cowl due to improper use of the safety catch.