SAA A346 at Johannesburg on Feb 25th 2021, Alpha Floor Activation on departure

Last Update: March 25, 2021 / 12:45:20 GMT/Zulu time

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Photo of SAA South African Airways ZS-SNG, Airbus A340-600 — SAA South African Airways ZS-SNG, Airbus A340-600 (Photo credit: Dulles_Aviation / Flickr / License: CC by)

Incident Facts

Date of incident
Feb 25, 2021

Classification
Incident

Airline
SAA South African Airways

Flight number
SA-4272

Departure
Johannesburg, South Africa

Destination
Brussels, Belgium

Aircraft Registration
ZS-SNG

Aircraft Type
Airbus A340-600

ICAO Type Designator
A346

Airport
OR Tambo International Airport, Johannesburg

Airport ICAO Code
FAOR

A SAA South African Airways Airbus A340-600, registration ZS-SNG performing flight SA-4272 (scheduled Feb 24th, actual dep Feb 25th) from Johannesburg (South Africa) to Brussels (Belgium), was climbing out of Johannesburg's runway 21R just after midnight at 00:11L (Feb 24th 22:11Z) when the crew after gear retraction began to retract the flaps and slats. While retracting the flaps/slats Alpha Floor Protection activated, the aircraft sent out ACARS messages to the aircraft and engine manufacturer as well as dispatch. The aircraft reduced rate of climb to about 500 fpm while climbing through 7000 feet MSL (aerodrome elevation 5558 feet MSL), lost about 10 knots of speed over ground briefly before the recovery returned the aircraft into a stable climb again. The aircraft continued to Belgium for a landing without any further apparent incident.

SAA on order by South Africa's Government had conducted the flight to pick up vaccines from Brussels. The flight had originally been scheduled for Feb 18th 2021, however, South Africa's CAA did not grant permission claiming that the pilots were not current due to SAA not operating flights due to Covid Pandemic and other local issues surrounding SAA. However, after some additional training the CAA granted permission for the flight to take place departing on Feb 24th 2021.

According to information The Aviation Herald received the flight crew created a manual flight plan for the trip to Brussels. It is being claimed that there was a confusion on the takeoff mass computation being about 90 tons below the actual takeoff mass.

However, there are also reports of a well known software bug in the FMS, which is known at least since 2016 and reduces the takeoff mass by about 90 tons on the FMS (affecting F and S speeds, but not affecting the manually entered V speeds) if the takeoff mass is entered before engine start. This could result in incorrect flaps monitoring speeds, incorrect flaps schedule and stall speed indications (which would become around about 35 knots lower than correct) while not affecting the actual takeoff performance. However, if the flaps are retracted according to the schedule displayed on the PFD, high angles of attack and Alpha Floor Activations are possible.

According to an A346 pilot, The Aviation Herald spoke to, this fault was actually personally observed by the pilot and caught by stringent standard operating procedures preparing for departure, which do require to compare the FMS takeoff mass again after engine start. This software issue is well known and the pilot had been informed about the bug some time prior to his observation. The pilot re-entered the correct takeoff mass and subsequently departed without any further incident.

According to information The Aviation Herald received, the crew denied the occurrence and even stated: " The aircraft lied!". The crew also refused to participate in a meeting on Mar 16th 2021 intended to discuss the occurrence.

South Africa's CAA confirmed to local South African media that the occurrence took place indeed stating however, that although they were required to be informed within 72 hours at the latest (for that serious incident actually 48 hours) they were not informed about the occurrence until Mar 17th 2021. An investigation team has been formed.

South Africa's Pilot Association stated they are aware of the automated messages sent by the aircraft and contacted SAA to ensure, that a proper investigation was being carried out, however, received no reply.

On Mar 25th 2021 the airline reported flight SA-4272 was departing Johannesburg to Brussels to collect a consignment of Johnson&Johnson vaccines, when a "pending Alpha Floor" was signalled. The crew recognized the symptoms prior to the Alpha Floor, took appropriate actions and thus prevented any further warnings. The aircraft continued with its acceleration schedule and continued to Brussels. A full investigation is being conducted by the SAA Safety Department, South Africa's Civil Aviation Authority was informed.

After receiving first information about the occurrence in the evening of Friday Mar 19th 2021 and first investigations, The Aviation Herald inquired with South Africa's CAA on Sunday Mar 21st 2021, however, did not receive a reply so far.

The aircraft remained on the ground in Brussels for about 24 hours. Sources tell The Aviation Herald that on departure from Brussels' runway 25R on Feb 26th 2021 at 19:00L (18:00Z) the aircraft accelerated reaching more than 200 knots over ground at less than 1500 feet AGL and thus did not adhere to the noise-abatement procedures at Brussels Airport. The aircraft returned to Johannesburg without any apparent further incident.

Metars:
FAOR 250200Z 01008KT 4700 BR BKN003 16/15 Q1020 NOSIG=
FAOR 250100Z 01009KT 5000 RA SCT003 16/15 Q1020 NOSIG=
FAOR 250000Z 04004KT CAVOK 16/15 Q1020 NOSIG=
FAOR 242300Z 07004KT CAVOK 16/15 Q1021 NOSIG=
FAOR 242200Z 08005KT 8000 -RA FEW045 16/15 Q1022 NOSIG=
FAOR 242100Z VRB04G15KT 8000 -SHRA SCT037TCU BKN042 16/15 Q1022 NOSIG=
FAOR 242000Z 11005KT 6000 FEW004 BKN037 16/16 Q1022 NOSIG=
FAOR 241930Z 16003KT 6000 FEW006 16/16 Q1022 NOSIG=
FAOR 241900Z 16005KT 5000 BR FEW006 16/16 Q1022 BECMG NSW=
FAOR 241830Z 15003KT CAVOK 17/16 Q1022 NOSIG=