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Report: Boeing 707 stalls during emergency return after losing engine cowlings
14 March 2013
No.4 engine cowlings of Boeing 707 ST-AKW (photo: GCAA)

No.4 engine cowlings of Boeing 707 ST-AKW (photo: GCAA)

A stall situtation during an emergency return to the airport after separation of the no.4 engine cowlings was concluded to have caused a fatal accident involving a Boeing 707 cargo plane , according to the UAE General Civil Aviation Authority (GCAA). It was also concluded that there was poor safety oversight within the airline as well as by the Sudanese CAA.

On October 21, 2009 a Boeing 707 cargo plane, owned by Azza Transport of Sudan, was destroyed when it crashed in a desert area immediately after takeoff from Sharjah Airport (SHJ), United Arab Emirates. All six on board were killed.

The airplane flew on behalf of Sudan Airways, carrying  air conditioning units, auto parts, computers and personal effects to Khartoum, Sudan. During initial climb, the core cowls of engine no. 4 separated and fell on the runway.

The aircraft continued in a shallow climb with level wings when the pilot informed the ATC that he lost engine no.4. He assumed this because the no. 4 Engine Pressure Ratio (EPR) manifold flex line had ruptured, leading to erroneous reading on the EPR indicator. The crew interpreted the EPR reading as a failure of the engine. Accordingly they declared engine loss and requested the tower to return to the airport.
The aircraft went into a right turn, banked and continuously rolled to the right at a high rate, sunk, and impacted the ground with an approximately 90° right wing down attitude.

The investigators concluded that the accident was caused by:
(a) the departure of the No. 4 engine core cowls;
(b) the consequent disconnection of No. 4 engine EPR Pt7 flex line;
(c) the probable inappropriate crew response to the perceived No. 4 engine power loss;
(d) the Aircraft entering into a stall after the published maximum bank angle was exceeded; and
(e) the Aircraft Loss of Control (“LOC”) that was not recoverable.

Contributing factors to the accident were:
(a) the Aircraft was not properly maintained in accordance with the Structure Repair Manual where the cowls had gone through multiple skin repairs that were not up to aviation standards;
(b) the Operator’s maintenance system failure to correctly address the issues relating to the No. 4 engine cowls failure to latch issues;
(c) the failure of the inspection and maintenance systems of the maintenance organization, which performed the last C-Check, to address, and appropriately report,
the damage of the No. 4 engine cowls latches prior to issuing a Certificate of Release to Service;
(d) the Operator’s failure to provide a reporting system by which line maintenance personnel report maintenance deficiencies and receive timely and appropriate guidance and correction actions;
(e) the Operator’s quality system failure to adequately inspect and then allow repairs that were of poor quality or were incorrectly performed to continue to remain on the Aircraft; and
(f) the SCAA safety oversight system deficiency to adequately identify the Operator’s chronic maintenance, operations and quality management deficiencies..

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