SAA A346 over Switzerland on Nov 6th 2018, overspeed, dual ADR failure

Last Update: December 3, 2019 / 12:05:59 GMT/Zulu time

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Incident Facts

Date of incident
Nov 6, 2018

Classification
Incident

Flight number
SA-260

Aircraft Registration
ZS-SNF

Aircraft Type
Airbus A340-600

ICAO Type Designator
A346

A SAA South African Airways Airbus A340-600, registration ZS-SNF performing flight SA-260 (dep Nov 5th) from Johannesburg (South Africa) to Frankfurt/Main (Germany), was enroute at FL380 climbing to FL390 over Switzerland about 40nm southsoutheast of Zurich (Switzerland) when the aircraft encountered overspeed, the speed over ground increased to 530 knots. The crew slowed the aircraft and continued to Frankfurt for a safe landing about 35 minutes later.

Germany's BFU reported the aircraft encountered an overspeed event, rated the occurrence a serious incident and opened an investigation.

According to information The Aviation Herald received the aircraft sustained multiple system faults in flight including the failures of Air Data Reference 2 (ADR2) and 3 (ADR3) associated with the autopilot and autothrust disengaging and the fall back of the FBW into alternate law.

The occurrence aircraft remained on the ground for 3 days, then returned to Johannesburg as flight SA-4263.

On Mar 1st 2019 South Africa's CAA (SACAA) reported they have opened an investigation into a SAA pilot, who had allegedly been flying commercial aircraft with a forged air transport pilot license for more than 20 years. The matter came to light during the investigation into the flight SA-206 (editorial note: this is in error, correct flight number was SA-260) from Johannesburg to Frankfurt in November 2018, which had a reportable incident in Swiss Airspace. The pilot in question has already resigned.

Sources in South Africa state, the pilot held a correct and valid CPL. After joining SAA in 1994 he was expected to upgrade to ATPL within 5 years by SAA (but not by regulations or authorities), however failed to do so and forged his ATPL. The pilot refused to be upgraded to captain when asked and remained first officer.

Germany's BFU reported in their November Bulletin that the aircraft was enroute at FL380 with winds from 215 degrees at 65 knots (tail wind). When crossing the main ridge of the Alps near the Clariden peaks (Switzerland) the winds changed to 175 degrees at 15 knots, with the windspeed reducing from 50 knots to 15 knots in 15 seconds, causing the airspeed increase from 0.82 to 0.88 mach, the overspeed warning activated for 8 seconds, the speed increased further to 0.89 mach before reducing again to 0.86 mach. 4 seconds after the overspeed warning activated the autopilot was disengaged, the captain (59, ATPL, 17,694 hours total, 16.5 hours on type) took control of the aircraft, the pitch angle increased from 3.5 degrees to 11 degrees by manual inputs resulting in a vertical acceleration of +1.6G, the aircraft climbed up to 5700 feet per minute. The first officer (61, CPL, 18,532 hours total, 5,274 hours on type) observed a rapid increase of the Alpha Protection speed in his primary flight display and suspected a possible erroneous behaviour of the stall protection. The captain therefore instructed to turn off two air data reference units. In the meantime autothrust had reduced the engine thrust from 1.09 to 0.7 EPR, while the aircraft climbed through FL390 ADR#2 and ADR#3 were turned off, the flight control system changed from normal to alternate law, autothrust disengaged. The crew declared PAN PAN, the pitch angle began to reduce again. At FL400 the IAS had reduced to 203 knots (0.68 mach), the aircraft began to descend, the pitch angle was increased again resulting in a stall warning at 0.7 mach and 7 degress nose up angle of attack. Manual inputs by the left sidestick to lower the nose brought the pitch to below 6 degrees nose up, the stall warning ceased. In the following 23 seconds there were alternating inputs on the side stick to pull the nose up and push the nose down with the pitch ranging from -4.6 degrees (4.6 degrees nose down) to 6.3 degrees nose up pitch with associated angles of attack between 3 and 8 degrees, the stall warning activated three more times for up to 4 seconds. 14 seconds after the last stall warning the engine thrust increased to above 1.00 EPR, the crew declared Mayday, Mayday reporting they had no control [...]. At that point the aircraft was descending through FL370 at 6600 fpm. About 30 seconds later the sinkrate briefly reduced to 100 fpm, in the following 3.5 minutes the aircraft continued to descend before stabilizing at FL340. Subsequently the two ADR units were turned on again and the crew reported they were able to engage autoflight again, about 5 minutes after the onset of trouble. The aircraft landed in Frankfurt about 36 minutes after the onset of trouble.

The BFU reported a second first officer (39, ATPL, 11,453 hours total, 3,901 hours on type) was augmenting the flight crew and was licensed to occupy the left hand seat while acting as relief pilot for the commander. At the time of the occurrence he was seated in the observer seat.

With respect to the captain the BFU stated, he had acquired his ATPL on Nov 19th 1990, the license was valid through Mar 31st 2019. He had completed his training for A340-600 on Oct 29th 2018. A proper medical was presented to the BFU.

With respect to the first first officer the BFU reported he held a valid CPL issued on Jan 20th 2018 by South Africa's CAA valid through Jan 31st 2019. He had completed his training for A340-600 in Feb 2005. The BFU was not presented with a medical by the first first officer.

The second first officer had received his ATPL on Jan 26th 2005 issued by South Africa's CAA, which was valid through Mar 31st 2019. He completed his training for the A340-600 on Aug 17th 2013. A proper medical was presented to the BFU.

The BFU reported that an operations engineering bulletin (OEB) had been issued in 2015 in addition to the FCOM. The OEB describes how to disengage Alpha Protection in case of an erroneous activation by switching two ADR units off, if in straight level flight without any changes in load the indication of the V-Alphaprot increases with increasing mach number. The OEB had been released after it was established that in some case an erroneous activation of the protection had occurred.

A weather model computed the presence of mountain waves in the area of the occurrence.
Incident Facts

Date of incident
Nov 6, 2018

Classification
Incident

Flight number
SA-260

Aircraft Registration
ZS-SNF

Aircraft Type
Airbus A340-600

ICAO Type Designator
A346

This article is published under license from Avherald.com. © of text by Avherald.com.
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