chi non ha peccato scegli la prima pietra
Tutti abbiamo fatto nella nostra vita professionale un unstabilized app,
l'importante si riassume in una parola inglese:
LESSON LEARNED
Report: Air France A319 at Tunis on Mar 24th 2012, extreme rate of descent on glideslope intercept, GPWS alerts and descent below safe altitude
An Air France Airbus A319-100, registration F-GRHU performing flight AF-2184 from Paris Charles de Gaulle (France) to Tunis (Tunisia), was preparing for the approach to Tunis, the crew briefed for an ILS approach to Tunis' runway 29 according to ATIS information. The captain (ATPL, 8,900 hours total, 2,600 hours on type), pilot flying, subsequently descended the aircraft using the autopilot in vertical speed mode at -1000 feet per minute, the aircraft initially being below the theoretical 3 degrees glidepath went through the 3 degrees glide and got high on the (far) approach. Upon contacting Tunis approach the controller advised that the active runway had just been switched to runway 19, which shortened the flying distance to land by about 20 nautical miles. The captain briefed for an ILS approach to runway 19 and decided to continue the approach in marvelous weather conditions. At the end of the briefing he realised that the autopilot was still in vertical speed mode with 1000 feet rate of descent selected. At FL207, 33nm to touch down, 276 KIAS the captain selected the autopilot into open descent, reduced the thrust to idle, deployed the speed brakes and selected a speed of 300 knots. The aircraft reached a rate of descent of about 5000 feet per minute and descended through FL120 about 20nm before touch down, the captain selected 240 KIAS which also reduced the rate of descent. The aircraft descended through FL100 13.5nm before touchdown, the autopilot was disconnected, the landing gear was selected down, the crew reported runway in sight. Doing 250 KIAS the aircraft intercepted the localizer 8nm before touchdown at 6000 feet, 3400 feet above 3 degrees glideslope, the captain selected the go-around altitude into the flight control panel which caused the flight director to revert to vertical speed (4400 fpm rate of descent). Descending through 3550 feet, 1700 feet above glide, about 5nm from touchdown, flaps still at position 0, vertical speed -4400 fpm, speed brakes and landing gear extended, the first officer (ATPL, 1,700 hours on type) transmitted they were established on the ILS 19. The autothrust was disconnected, the engines were reduced to idle thrust. The aircraft received landing clearance. 8 seconds after the landing clearance the first officer advised they were "a little high" and requested a 360 (full circle) to the right. During these communications the captain re-engaged autothrust and autopilot, the glideslope capture activates, a GPWS warning "Sink Rate!" sounds at 836 feet AGL, 220 KIAS, 2500 fpm rate of descent 2.5nm before the runway threshold. The GPWS calls "Pull Up! Pull Up!" and "Too low! Terrain!" Tower approves a 360 to the left. The captain stowed the speed brakes and disengaged the autopilot again at 428 feet AGL, 2 seconds later 398 feet AGL, the controller repeats the clearance for left hand orbit, the flaps are extended to position 1. 13 seconds later the thrust levers are placed into the TO/GA detent, the aircraft turns to the left and climbs to 2000 feet, then positions for a visual approach to runway 19 with ILS support and in the end landed safely.
The French BEA released their final report in French concluding the probable causes of the incident were:
- The crew commenced an unstabilized approach following a decision to initiate and continue the approach, that started above profile and would have required remedial action to resolve.
- inadequate communication between the crew who after a change of runway did not:
* define and implement a strategy to properly adjust the trajectory
* define criteria to abort the approach and reposition for another approach
- the documentation provided by the operator does not include operational limits to intercept a glideslope from above the profile
The BEA referenced the occurrence of F-GLZU, see Report: Air France A343 at Paris on Mar 13th 2012, intercepted mirror glide slope, large pitch oscillations and approach to stall stating, that one of the safety recommendations issued to EASA as result of that investigation was the requirement for operators to provide limits to flight crew for intercepting glidepathes from above the profile. The safety recommendation was re-iterated.
The BEA reported that the first officer in post flight interviews reported that a discussion had taken the attention of both flight crew throughout cruise flight. The approach briefing was thus started only after they had left FL350 descending towards Tunis. He realised they were above profile and made the captain aware of this fact twice, but having been commander on other aircraft types before he did not want to encroach the captain's decisions. Due to the unusual request to do an orbit on final approach his work load got so high, that he did not think of calling for a go-around. He did not hear any of the GPWS alerts, explaining he was focussed on the stabilisation criteria at 500 feet. Following the flight he believed he confused sympathy and cockpit resource management, which prevented him to fulfill his role as pilot monitoring.
The captain said in his interviews, that he realised at FL100 the approach was compromised. Given the excellent weather he wanted to descend the aircraft onto the profile however. He heard the GPWS "Sink Rate" but did not hear the other GPWS alerts.