As presented by AEROIN just over a month ago, a serious incident was recorded on May 23 in France, in which an Airbus A320 plane came closer to the ground than the minimum safe altitude during two landing approaches.
At the time, according to The Aviation Herald, the A320 aircraft registered under registration 9H-EMU, from Getjet Airlines Malta, operating for Norwegian Sweden, was performing flight D8-4311 from Stockholm, Sweden, to Charles de Gaulle airport. (CDG/LFPG) in Paris, France, when the incident took place.
The pilots were conducting an RNP (Required Navigation Performance) approach to land on CDG runway 27R under limited visibility conditions, however the Airbus A320 had a wrong altimeter setting (QNH). Instead of atmospheric pressure 1001 hPa, pressure 1011 hPa was selected in the equipment.
As a result, two approximations were performed below the glideslope (imaginary descent ramp) until the landing was completed, after the pilots gained visual contact with the runway.
Now, this Monday, July 11, the French investigative authority (BEA) has published the Preliminary Report, presenting the data already collected on the sequence of events.
According to the document, for the first approach, the air traffic controller provided an erroneous QNH (1011 hPa instead of 1001 hPa), causing the aircraft to be 260 feet (79 meters) below the correct altitude.
Although the crew reported 1011 hPa several times and other aircraft on the same frequency received the correct QNH of 1001 hPa, the error was not detected by the controller or crew.
The MSAW alarm (a system that warns the controller of increased risk of controlled flight over terrain) went off and the crew began a go-around about 1 nautical mile (1.85 km) before the runway threshold.
The aircraft reached a minimum of 405 feet according to QNH 1001hPa (679 feet by QNH 1011 hPa), while the radio altimeter, which measures the actual height above the ground from the emission of radio waves, indicated 6 feet, that is, only 1.8 meters for contact with the ground. Despite this, no TAWS (Aircraft Ground Collision Warning and Prevention System) alert was recorded during the approach.
After the go-around, the controller instructed: “turn right, heading 360, climb to 5000 feet, 1001”, but the crew read back: “360 and climb to 5000, 1011”. The response of 1011 instead of 1001 was not noticed by the controller.
As the pilots guided the aircraft to a new approach, the air traffic controller was changed. However, the correct QNH was not provided to the pilots of the A320 or any other flight until the aircraft made the new approach, still with the wrong QNH.
The aircraft was positioned for another approach, 3.1 nautical miles (5.7 km) before the runway threshold, and an air traffic control MSAW alarm was triggered again.
The controller informed the pilots that he did not understand the reason for the MSAW alarm and reported that he had visual contact with the aircraft.
In later testimonies, pilots reported that they saw the PAPIs (Precision Approach Path Indicator Lights), with one white light, one pink and two reds, maybe three reds, however, definitely not 4 reds.
They corrected their trajectory to get two white and two red and continued to an uneventful landing.
Next steps of the investigation
According to BEA, the validation and analysis of the parameters, as well as the analysis of the event as a whole, continue. Special, but not limited, attention will be given to the analysis of the following points:
– non-activation of the TAWS alert;
– triggering of automatic radio-altimeter calls on the aircraft;
– MSAW adjustments and configuration in CDG;
– MSAW phraseology;
– flight crew and air traffic controller training and procedures;
– flight crew and air traffic controller performance;
– additional ground and on-board systems to prevent CFIT (controlled flight into terrain) during approaches using the baro-VNAV function;
– safety impact assessments associated with the ICAO Performance Based Navigation (PBN) plan and its regional and national adaptations;
– similar events;
– manufacturers’ operational documentation on approximations using the baro-VNAV function.