31st of January 1986, Icing, Blog #733
- V2Aviation
- 1 day ago
- 3 min read
On this day in aviation history, 31st of January 1985, a Shorts SD3-60 (Shorts 360-100) was operating a scheduled passenger flight from Dublin (Ireland) to East Midlands (United Kingdom). During the flight preparation, weather information (including a report of severe icing) and operational restrictions at the destination airport (precision approach radar unserviceable) were reviewed by the crew.
The aircraft was refuelled and fully serviced before boarding the 33 passengers, besides the two pilots (both qualified captains), a cabin attended were onboard the aircraft when it lifted off from the Dublin runway at 17.25 lt (local time).
During the climb to cruise flight level (FL 90), both wing and tail anti ice system were used as the aircraft climbed through the layers of stratiform clouds. Once above the clouds, the anti-ice systems were switched off. The flight continued without any issues.
As the aircraft was descending towards East Midlands, the crew switched on the aircraft's anti-ice system, which heats the windscreen, engine air intakes, propellers, static air vents and pitot probes, in accordance with normal operating procedure, they did not use the wing and tail anti-ice systems. The clouds were dense during the descend ice was heard striking the fuselage, which was being thrown off the propellers. The crew increased the propeller rpm to increase the ice shedding from the propeller blades. Visual inspections of the wing from the cockpit at that time did not reveal any ice built up on the wings.
After an uneventful approach, the aircraft was fully established on the ILS for runway 09 at East Midlands. The crew received the latest wind data when at ~1000 feet height, at 160̊ /15 kts, with gusts reported up to 30 kts.
Once below 1000 feet, the aircraft suddenly rolled very sharply to the left without apparent cause. With the application of corrective aileron and rudder, the aircraft rolled rapidly right, well beyond the wings' level position. This alternate left and right rolling motion continued with the angles of bank increasing for some 30 seconds, causing the commander to believe that the aircraft might roll right over onto its back. The angles of bank then gradually decreased. During this period and the subsequent few seconds, the aircraft established a very high descent rate approaching 3000 feet/min. Subsequently, with the aid of full engine power, the airspeed increased, and the rate of descent was arrested just as the aircraft struck an 11 KV power cable. It continued through another similar cable, two of the supporting wooden poles and the tops of two trees, before coming to rest nose into a small wood edging a field of barley, some 460 metres from the impact with the first power cable.
The cockpit and passenger cabin were relatively undamaged, and there was no fire. The aircraft came to rest lying virtually upright, and the passengers and, subsequently, the crew successfully evacuated from the front and rear emergency exits. The crew assembled the passengers a short distance away from the aircraft and ensured that everyone was present. One passenger had suffered a broken wrist and another an injured back, but the crew and the remaining passengers were unhurt.
When the emergency vehicles arrived, the survivors were escorted down through the field and were subsequently taken to the airport terminal. The two injured passengers were taken to the Derbyshire Royal Infirmary.
The accident was investigated by the Air Accident Investigation Branch, who, after an extensive analysis of the accident, completed their report with several findings, among others;
The aircraft's performance degraded steadily during the descent through cloud and was most probably caused by the indicated accretion of clear ice on the airframe. Ice on the propeller may have contributed to a small extent.
At around 1000 feet agl, almost all control was lost.
The major factor responsible for the initial departure from controlled flight was· the continued presence of ice on the aerodynamic surfaces, but turbulence may have precipitated it.
The precise profile of the ice formation on the airframe could not be determined, nor could the manner in which the airflow was modified
They concluded that the cause of the accident was:
The effects of a significant accumulation of airframe ice degraded the aircraft's stability and control characteristics, rendering the crew unable to maintain control.
The full accident investigation report, which served as the source for this blog, can be accessed by clicking on the .pdf file below:
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