Incident Overview

Date: Thursday 20 August 1964
Aircraft Type: BAC One-Eleven 201AC
Owner/operator: British Aircraft Corporation – BAC
Registration Number: G-ASJD
Location: near Tilshead – ÿ United Kingdom
Phase of Flight: Landing
Status: Substantial, repaired
Casualties: Fatalities: 0 / Occupants: 4
Component Affected: Aircraft Control System (specifically, the pilot’s control input and the tail parachute deployment).Aircraft Control System (specifically, the pilot’s control input and the tail parachute deployment).
Category: Accident
A test flight involving two test pilots and two flight test observers was conducted on pre-certification stalling tests. The aircraft was fitted with a tail parachute and modified engine reverse thrust cascades, designed to induce a powerful nose-down pitching moment during stalling. During the first test run, the aircraft experienced oscillations and the pilot determined a stable stall was imminent. The pilot streamed the tail parachute, believing the aircraft was in a stable stall. Later, full flap and full power reduced descent rate, leading to a wheels-up landing on undulating grassland. The aircraft sustained minimal damage and no injuries to the crew.A test flight involving two test pilots and two flight test observers was conducted on pre-certification stalling tests. The aircraft was fitted with a tail parachute and modified engine reverse thrust cascades, designed to induce a powerful nose-down pitching moment during stalling. During the first test run, the aircraft experienced oscillations and the pilot determined a stable stall was imminent. The pilot streamed the tail parachute, believing the aircraft was in a stable stall. Later, full flap and full power reduced descent rate, leading to a wheels-up landing on undulating grassland. The aircraft sustained minimal damage and no injuries to the crew.

Description

G-ASJD, with a crew of two test pilots and two flight test observers, was being flown on pre-certification stalling tests, with the centre of gravity at 0.15 standard mean chord, the furthest forward position for which the aircraft was then cleared. For the purposes of the test flying programme, the aircraft was fitted with a tail parachute and with modified engine reverse thrust cascades; these two modifications were designed to produce powerful nose-down pitching moments, if an excessively high angle of incidence was experienced during the stalling tests. During the first test run at just over 20000 ft. the aircraft developed a slight oscillation in pitch and the pilot decided to recover and begin again. During the intended recovery, he gained the impression that the aircraft’ s response to elevator movement was not normal and that the aircraft might be in a stable stall. The tail parachute was therefore streamed although the IAS had by then increased to 225 knots and the incidence was 6ø. Forward and upward thrust was also applied on a number of occasions, but this served only to increase the pilot’s conviction that a stable stalled condition existed. Late in the descent it was found that full flap and full power reduced the rate of descent considerably, and a wheels-up landing was made on undulating grassland. The aircraft was relatively little damaged in the ground slide and none of the crew were injured. It was concluded that, when the pilot pushed the control column forward after the stalling run, the aircraft had responded correctly as indicated by the instruments. Under the erroneous impression that the aircraft was in a stable stall however, the pilot streamed the tail parachute and it was the retention of the streamed parachute that made the emergency landing necessary. Had it been jettisoned during the descent, the flight could have continued normally.

Primary Cause

Pilot error ? inducing a stable stall through improper control input and retention of the tail parachute.Pilot error ? inducing a stable stall through improper control input and retention of the tail parachute.

Share on:

Leave a Reply

Your email address will not be published. Required fields are marked *