An Embraer Legacy 500 corporate jet was to operate a private flight from Moscow-Domodedovo airport (Russia) to Paris Le Bourget airport (France). There were no other occupants than the two pilots of the flight.
The failed right-hand main landing gear (Source & © BEA) Prior to departure, a thin layer of ice was observed on the wings. The crew arranged de- and anti-icing and the aircraft was subsequently free of ice and protected against icing for its departure. (Limited protection in accordance with the valid hold over time tables in the aircraft flight manual).
During the flight preparations, the crew set the selector of the ice protection control panel to ALL before starting up the engines. During the engine start an "A-I WINGSTAB FAIL" message (indicates a failure of the anti-icing system of the wing and horizontal stabilizer leading edges.) was displayed on the EICAS (Engine Indication and Crew Alerting System). The crew attempted to reset the system by pressing the WINGSTAB push button and then using the ICE PROT MODE selector. They were unsuccessful in clearing the failure message.
Overhead control panel with detail of Ice Protection Control Panel
(Source; BEA © Embraer)
After attempts to reset the system failed the crew taxied to the assigned runway and took off after receiving their take-off clearance. ~5 minutes after lift-off a "STALL PROT ANTICIPATE" was presented on the EICAS and remained on the display for the duration of the flight. The flight continued without problems with the Captain as Pilot Flying (PF) and the co-pilot as Pilot Monitoring (PM). The weather for Le Bourget airport did not give any risk of icing;
Wind 220º at 7 knots
Visibility > 10 km
Clouds Few at 2800 feet, broken at 4200 feet
The flight was cleared for an ILS approach to runway 27 at a speed of between 120 knots and 130 knots. While on the glide path, at an altitude of 2200 feet, the Angle Of Atack limiter protection activated, and the autopilot (AP) automatically disengaged. The aircraft subsequently descended below the glideslope, resulting in an aural glideslope warning. The PF increased the thrust and leveled off in an attempt to return to the glide path.
The AOA limiter protection was deactivated automatically and the crew re-engaged the AP.
At ~1000 feet the AOA limiter protection activated itself again and the AP disengaged again as well. The PM advised the captain to keep the speed above the red tape, which is the minimum speed authorised by the AOA limiter protection. This protection limits the angle of attack and did not allow the captain to sufficiently increase the airplane’s pitch attitude in order to flare, despite making a full nose-up deflection on the sidestick.
Speed tape indication on a Legacy 500
This resulted in a touchdown with a high rate of descent (1350 ft/min) at a load factor of
4 G. The right-hand main landing gear failed and the right-hand main landing gear upper rear hinge puncture the wing upper surface. The aircraft came to a stop on a runway exit.
There were no injuries, however, the damage to the aircraft was substantial.
Synthesis of FDR & OMS (Onboard Maintenance System) data
The BEA (Bureau d'Enquêtes et d'Analyses pour le sécurité de l'aviation civile) was allerted and initiated an investigation. In their accident investigation report (which served as the source for this blog) they described their findings and came to the following conclusion (copied from the report);
"The crew undertook the flight to Le Bourget airport despite the presence of the A-I WINGSTAB FAIL message and icing conditions at departure from Moscow. The occurrence of the failure is linked to the activation of the ice protection system in the ALL position before engine start-up. The procedure associated with this failure, as written at the time of the accident, did not enable the crew to reinitialize the ice protection system. The BEFORE TAKEOFF procedure and then the consultation of the MEL should have resulted in the crew postponing the flight. During the climb, the appearance of the STALL PROT ANTICIPATE message on the EICAS informed the crew of the increase in AOA limiter protection activation speeds. The associated procedure should have led the crew to increase the reference speed by 30 kt during the approach."
The investigation report is available below with more details on the accident for the readers' reference, click on the .pdf file below to access the report;