Douglas C-47A-10-DK (DC-3) – OO-CBL

Incident Overview

Date: Tuesday 31 August 1948

Aircraft Type: Douglas C-47A-10-DK (DC-3)

Owner/operator: Sabena

Registration Number: OO-CBL

Location: near Kimbwe – ÿ Congo (Democratic Republic)

Phase of Flight: En route

Status: Destroyed, written off

Casualties: Fatalities: 13 / Occupants: 13

Component Affected: The C-47 passenger plane’s control surfaces (wing, stabilizer, rudder, etc.) and the aircraft’s airframe.The C-47 passenger plane’s control surfaces (wing, stabilizer, rudder, etc.) and the aircraft’s airframe.

Category: Accident

The C-47 passenger plane impacted terrain near Kimbwe, resulting in a catastrophic loss of the aircraft. Initial examination reveals a complete destruction of the plane, with debris suggesting a significant impact. The investigation points to a complex sequence of events, including potential fire, loss of critical components, and vibration issues, potentially exacerbated by a faulty weight balance. While definitive cause determination remains challenging due to the wreckage, several assumptions have been made, including pilot incapacitation, a dry tornado, and a failure of the autopilot. The unusually strong updrafts in the region, as reported by the Territorial Administration Kipushi, contributed to the conditions that led to the tornado. The investigation also points to a history of similar failures in DC.3 aircraft, notably the Sperry A-3 autopilot, suggesting a systemic issue with control system functionality. The incident highlights a critical failure in the aircraft’s control system, potentially stemming from a combination of factors.The C-47 passenger plane impacted terrain near Kimbwe, resulting in a catastrophic loss of the aircraft. Initial examination reveals a complete destruction of the plane, with debris suggesting a significant impact. The investigation points to a complex sequence of events, including potential fire, loss of critical components, and vibration issues, potentially exacerbated by a faulty weight balance. While definitive cause determination remains challenging due to the wreckage, several assumptions have been made, including pilot incapacitation, a dry tornado, and a failure of the autopilot. The unusually strong updrafts in the region, as reported by the Territorial Administration Kipushi, contributed to the conditions that led to the tornado. The investigation also points to a history of similar failures in DC.3 aircraft, notably the Sperry A-3 autopilot, suggesting a systemic issue with control system functionality. The incident highlights a critical failure in the aircraft’s control system, potentially stemming from a combination of factors.

Description

The C-47 passenger plane impacted terrain and broke up near Kimbwe. The airplane was en route to Elizabethville (now Lubumbashi). CONCLUSIONS (translated from French): From the examination of the debris the orientation and trajectory of the various components of the aircraft before impact can be established more or less likely, but it has not been possible to determine the actual cause us to the events due to the almost complete destruction of the airplane. We are therefore reduced to make assumptions. Some can be removed with a near certainty: a.- fire in flight b.- in flight loss of an essential element of the for the stability of the aircraft like wing, stabilizer, etc. c.- airframe vibration which might have come from a faulty weight balance. All control surfaces were identified on site with their weight balance. None carries traces of damage. Note that, in Service Bulletin No. 207 Section I, DOUGLAS states: “It is emphasized that the DOUGLAS COMPANY has experienced no trouble in the past with the Control surfaces nor have any been reported either to us or to the Civil Aeronautics Administration.” Certain assumptions can not be ruled out: a.- Pilot incapacitation (natural or accidental: bird through the windshield, explosion of a cylinder, etc., etc.) b.- Dry tornado. The weather at the alleged time of the accident was: – Haze – Calm air, little cloudy – Average visibility. According to the crews who flew over the site of the accident during search the region was know for violent updrafts. The Territorial Administration Kipushi (30 Km. SW Elisabethville) confirmed that the day of the accident at 15.00 local time a dry tornado removed the roof of a house. c.- failure autopilot suddenly putting the aircraft into a dangerous position before the pilot could disconnect it. Several DC.3 airplane accidents in the USA have been attributed to autopilots. At the airline T.W.A. the Sperry A-3 autopilot was removed from the DC.3 aircraft. Several other companies have done the same. From this point of view, these are the most characteristic failures: a. Seizing of the “Air Relay”. b. Seizure of the “Balancing Oil Valve” c. Operating stop of the “following-up cable”: – Cable detached – Pulley stuck – Rupture of the cable return spring. d.- Failure or wedging of an essential control element or permanent deformation of the airfrane after a local failure This is an assumption that we can not report, although nothing positive can confirm it.

Primary Cause

Combination of factors including a likely fire, loss of critical components (particularly the wing, stabilizer, and control surfaces), vibration from a faulty weight balance, and a failure of the autopilot, potentially exacerbated by the unusually strong updrafts in the area.Combination of factors including a likely fire, loss of critical components (particularly the wing, stabilizer, and control surfaces), vibration from a faulty weight balance, and a failure of the autopilot, potentially exacerbated by the unusually strong updrafts in the area.

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