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Accident: Aeroflot SU95 at Moscow on May 5th 2019, aircraft bursts into flames during rollout and burns down
| By Simon Hradecky, created Sunday, May 5th 2019 16:19Z, last updated Wednesday, Jun 5th 2019 15:27Z An Aeroflot Sukhoi Superjet 100-95, registration RA-89098 performing flight SU-1492 from Moscow Sheremetyevo to Murmansk (Russia) with 73 passengers and 5 crew, departed Sheremetyevo's runway 24C at 18:04L (15:04Z) but stopped the climb at about FL100 following a lightning strike, declared loss of radio communication first, later emergency via transponder codes and returned to Sherementyevo for a landing on runway 24L at 18:31L (15:31Z). During the roll out the aircraft burst into flames, veered left off the runway and came to a stop on the grass adjacent to the runway, the aircraft burned down. 41 occupants perished in the accident (28 occupants still missing were declared dead), 35 occupants were able to evacuate the aircraft via both front door emergency slides, the 2 flight crew escaped via the escape ropes through the cockpit windows, there were 11 injuries. The aircraft's tail section completely burned down and was destroyed.
Emergency services reported the fire was extinguished about 45 minutes after landing. According to preliminary information there were 10 fatalities. Emergency services later updated the count to 13 fatalities, 6 injuries and a still undetermined number of missing occupants.
Russian News Agencies claim the aircraft received a lightning strike causing a total electrical failure and subsequent return and a hard landing.
Russia's Emergency Ministry originally claimed all occupants had evacuated the aircraft and were accounted for.
Local hospitals report more than 10 people on board of the aircraft are being treated.
Moscow's Interregional Transport Prosecution Office opened an investigation into the emergency landing at Moscow Sheremetyevo. The office initially confirmed one fatality, later confirmed 13 fatalities including two children. The Prosecution Office subsequently reported, only 37 occupants have been accounted for and are alive, 41 people are feared dead.
The Investigative Commission of the Russian Federation opened an investigation into the accident, the office declared 41 occupants of the aircraft (40 passengers, one crew) dead, 37 occupants are alive.
The Interstate Aviation Committee (MAK) have opened an investigation and are going to read out two of the black boxes, that have been recovered from the wreckage. On May 6th 2019 the MAK formally announced Superjet RRJ-95B registration RA-89098 suffered an accident at Moscow Sheremetyevo causing the death of 40 passengers and one crew member, the aircraft partially burned out. The MAK have formed a commission which started its work.
Late May 6th 2019 the MAK reported the CVR is in satisfactory condition, the FDR however was exposed to intense heat and was sustantially damaged. Specialists are dismantling the recorder and preparing the storage media for copying the data.
Aeroflot reported there have been fatalities, the number is being determined. In the evening the airline released a list of 33 passengers name, who have survived the accident, of those 5 were hospitalized.
Listeners on frequency report the aircraft lost radio contact at about FL100 and returned to Sheremetyevo without radio contact with ATC.
A ground observer reported he witnessed the landing. The aircraft bounced, on the third critical touchdown both main gear struts collapsed and the aircraft caught fire.
On May 6th 2019 Roaviatsia (Russia's CAA) reported a static atmospheric discharge at about 2100 meters (6900 feet MSL) resulted in the failure of the radios and other equipment including the autopilot. The crew returned to Sheremetyevo squawking loss of radio contact, subsequently emergency. While landing on runway 24L the aircraft experienced a rough landing, bounces and partial destruction of the aircraft. Following the 4th touch down fire broke out at the tail section of the aircraft and the aircraft veered left off the runway coming to a stop between taxiways A2 and A3. The aircraft burned partially out, there were fatalities and injuries.
On May 17th 2019 the MAK reported that the read out and analysis of the data off the flight data recorder has been completed.
On May 18th 2019 Rosaviatsia reported the captain (43, ATPL, 6,844 hours total, 1,570 hours on type) was assisted by a first officer (36, CPL, 773 hours total, 623 hours on type). About 30-40km (16-21nm) west of Sheremetyevo Airport there was rain in clouds, the clouds extended to a height of 8000 to 9000 meters (FL262-295) and contained a thunderstorm. The aircraft was climbing through 7900 feet at 15:08Z when an electrical failure occurred, the flight control system (FCS) degraded to "DIRECT MODE", the autopilot automaticaly disconnected, the aircraft was in the middle of thunderstorm activity. The captain assumed manual control of the aircraft until the end of the flight. Radio communication, that had taken place on VHF #1 radio so far, became unavailable, the crew was able to partially restore communication via VHF #2 on the emergency frequency only. The crew set the squawk for loss of communication. The crew decided to return to Sheremetyevo and performed a manual ILS approach to runway 24L. At the time the aircraft intercepted the glideslope the aircraft's mass was 42,600kg, which was 1600kg above the maximum landing weight. The crew deployed the flaps to 25 degrees in accordance with the flight crew operating manual for flight with minimum mode (DIRECT MODE) of the FCS as well as landing above MLW. At 15:26Z the crew set the emergency transponder code. Vapp was determined to be 155 KIAS, the descent on the glideslope was stabilized and without any deviation from Vapp. Winds during the approach came from 190 degrees at 30 knots, descending between 1100 and 900 feet the crew received 5 cycles of predictive windshear warnings "Wind Shear ahead, go around!". Descending through 260 feet AGL the aircraft began to deviate below the glide slope, a "GLIDESLOPE" warning occurred, descending between 180 to 40 feet the engine thrust was increased causing the aircraft to accelerate to 164 knots, at 16 feet AGL the speed was 170 KIAS. A Terrain Awareness Warning System aural signal "Retard" occurred, the engine thrust was reduced to idle. At that point the captain began to apply oscillating pitch inputs with increasing amplitude which changed the pitch angle up to +6 and -2 degrees. The aircraft made a "three point" touchdown 900 meters past the runway threshold at 158 KIAS and a vertical load of +2.55G and bounced up to 6 feet AGL. The spoilers did not deploy, in DIRECT MODE they are not permitted to operate automatically and need to be extended manually, however, the spoilers were not manually extended by the crew. 2 seconds after the first touch down the aircraft touched down a second time with the nose gear first at 155 KIAS and +5.85G, the aircraft bounced off again to 18 feet AGL. A third touchdown occurred at 140 KIAS in excess of +5G resulting in the destruction of the construction, a fuel spill and fire. While the aircraft was skidding along the runway at 100 KIAS a first fire alarm triggered in the aft cargo compartment, 16 seconds later in the tail section of the aircraft, the aircraft came to a stop 20 seconds after the first fire alarm. 40 seconds after the first fire alarm the fire extinguisher in the tail section was activated. The engines continued to run until end (at 15:31:04Z) of the FDR recording 47 seconds after the first fire alarm. The MAK is conducting the investigation which focusses also on the predicitive wind shear alerts and the reaction to them.
On Jun 5th 2019 the MAK reported the preliminary report of more than 100 pages has been drafted and is currently being proofread, it is estimated to be released in the coming days. The on field work has been completed, including mapping of the aircraft parts, study and analysis of the aircraft fragments, decoding and analysis of ground based and airborne objective monitoring data, collection and anaoysis of surveillance camera recordings, analysis of data received so far. Based on data from objective data recorders a complete flight reconstruction was performed including synchronised crew communication and ground based dispatching services at Sheremetyevo Airport. A number of recommendations were already drafted.
A video shows no smoke and no fire from the aircraft prior to touchdown.
Metars:
UUEE 051600Z 16004MPS 9999 -SHRA SCT055CB 16/11 Q1012 R24L/290045 R24C/290045 NOSIG=
UUEE 051530Z 17007MPS 9999 SCT060CB 17/11 Q1012 R24L/290045 R24C/290045 NOSIG=
UUEE 051500Z 14003G08MPS 9999 FEW060CB 17/13 Q1012 R24L/290045 R24C/290045 NOSIG=
UUEE 051430Z 16003MPS 130V230 9999 FEW060CB 17/13 Q1011 R24L/290045 R24C/290045 NOSIG=
UUEE 051400Z 19004G09MPS 9999 FEW060CB 17/12 Q1012 WS R24L R24L/290045 R24C/290045 NOSIG=
UUEE 051330Z 25006MPS 9999 SCT053CB 16/11 Q1012 R24L/290045 R24C/290045 NOSIG=
UUEE 051300Z 18006G15MPS 9999 -SHRA SCT053CB 20/08 Q1011 R24L/CLRD62 R24C/CLRD62 NOSIG=
UUEE 051230Z 15006MPS 9999 SCT053CB 21/08 Q1011 R24L/CLRD62 R24C/CLRD62 NOSIG=
Ground observer video showing short final and all bounces (Video: Aviation News 24):
Ground observer video first bounces until fire broke out (Thumbnail is wrong, video is correct):
Surveillance video (Video: 112 emergency services):
Evacuation in progress (Video: L.Metskhvarishvili):
The begin of the evacuation (Video: fatimakhadueva):
Passenger video of approach, final approach and landing until first bounce:
Scenes in the cabin:
The remains of the aircraft in close view:
The remains of the aircraft in the distance:
The aircraft seen after the fire was put out:
Evacuation in progress:
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By Simon Hradecky, created Friday, Jun 14th 2019 19:22Z, last updated Friday, Jun 14th 2019 19:22ZOn Jun 14th 2019 the MAK released their preliminary report (editorial note: in English!!) reporting the captain (42, ATPL, 6,800 hours total, 1,570 hours on type thereof 1,428 hours in command) was pilot flying, the first officer (36, CPL, 765 hours total, 615 hours on type) was pilot monitoring.
The MAK reported that examination of the fuselage revealed typical traces of "lightning impact" was found on the right hand angle of attack sensor, the right temperature probe and right ice detector.
The MAK reported the sequence of events stating the crew performed a normal departure though noticing flashes to their right, had cleaned up the aircraft and were cleared to climb to FL070. The MAK wrote:
At 15:07:10, the «HEADING» / «HDG» mode was engaged in the lateral control channel, and the selected heading was set to 327°. According to the Vnukovo doppler weather radar, the aircraft was flying through the active thunderstorm area (Fig. 3), that was moving from the southwest to north-east with the speed of 40-45 km/h. The transition to the selected heading mode caused the aircraft to initiate the right turn earlier than it is prescribed by SID KN 24E (Fig. 4). The crew did not requested the active thunderstorm area avoidance clearance.
On contacting the Approach controller, the crew was instructed to climb to FL 90. At 15:07:21, the crew set the new selected altitude of 8992 ft (2741 m) and activated the "CLIMB" / "CLB" mode.
During the period from 15:07:30 to 15:07:33, there is the following conversation in between the crew members was recorded: PIC: "We are going to get shaken", FO: "Damn it.", PIC: "Nothing to worry about".
At 15:07:34, the Approach controller instructed the crewto climb to FL 100. At 15:07:39, the selected altitude was 9984 ft (3043 m), with "CLIMB" / "CLB" mode continued to be engaged in the longitudinal control channel.
At 15:07:43, the "LATERAL NAVIGATION" / "LNAV" mode was engaged again in the horizontal plane. By that time, the aircraft was flying with heading of 317°, the right roll of 24° and the indicated speed of 250 kt (463 km/h).
At 15:08:03, the Approach controller instructed the crew to climb to FL 110. When the FO confirmed receiving the instruction, recorded by the CVR, the sound effect lasting for 1.5 seconds, starting from 15:08:09.7, was recorded. Most probably, at this stage, an atmospheric electricity impact affected the aircraft. 3 seconds prior, the FDR started to record the single commands, indicating the engagement of the permanent ignition on the both engines.
At 15:08:11, the crew set new selected altitude of 11008 ft (3355 m) and the new selected vertical speed of 3281 ft/min (16.7 m/s), and the "VERTCIAL SPEED" / "VS" mode was engaged.
At 15:08:11.9, the disengagement of the autopilot occurred, accompanied by the corresponding aural alert and the switching of the automatic flight control system into the "DIRECT MODE" (see Section 1.18.% of the present Report) with the audio alert "DIRECT MODE. DIRECT MODE". After the sound effect, simultaneously with the autopilot disengagement, the emotional exclamation of one of the crew members was recorded: "Wow!". The auto throttle continued to be engaged. The aircraft was in 20° right roll, crossing FL 89 (2700 m) in climb.
Starting from 15:08:12, during 15 seconds, the FDRs incorrectly recorded single commands and the analog parameters, which are usually recorded via the electronic interface unit, EIU-100. Two single commands and , "EIU1 FAULT" and "EIU2 FAULT", were recorded simultaneously.
The conducted examinations (Section 1.16.2 of the present Report) have shown that, most probably, at that stage, a reboot of the data concentrator units occurred, which caused the switching of the automatic flight control system into the «DIRECT MODE». According to the "List of special situations for the RRJ-95B aircraft" during the certification this event had been classified as a "complicated situation" (Section 1.18.14)
After the switching to the "DIRECT MODE", the "FLAPS ICE" configuration (slats 0°, flaps 1°) was engaged automatically.
Starting from 15:08:16, the aircraft control was switched to manual control of from the lefthand side pilot station. During the period of approximately 4 seconds, starting from the moment of the autopilot disengagement and till the PIC took over the aircraft control, the right roll decreased to 13°, pitch attitude increased (from 11° to 12°). The PIC's first control input from was affecting the roll channel, the sidestick was declined to 11.7° to the left (which is for more than half of its travel range), after that the sidestick was advanced to 6.8° (which corresponds to the half of its pitch-down travel range). Further sidestick control movements both in the roll and in pitch channels was of an abrupt and intermittent character. At 15:08:22, the aircraft was turned to the right via multiple impulse deflections of the sidestick ranging from 30% to 65%. To set the roll of ≈20° the pilot performed more than 10 roll deflection movements of the sidestick during the period of 18 seconds. Moreover, at different moments of the further flight the PRIORITY / APOFF8 button was pressed momentarily (for approximately 1 second) on the left sidestick 6 times.
The aircraft continued to develop the right turn in accordance with the KN 24E chart and continued to climb. At 15:08:47, the auto throttle was disengaged by the overriding movement of the thrust lever. At 15:09:17, the aircraft was put out of the right roll mode and was set to the heading of about 60°.
After short discussion with the FO, the PIC made the decision to return to Sheremetyevo and ordered the FO to report PAN-PAN. After several failed attempts to contact the controller on the working frequency via VHF-Station 1 (the one that was used from the beginning of the flight), at 15:09:32, after the discussion, the crew set the 7600 squawk code (for the lost radio communication).
At 15:09:35 radio-contact was restored at the emergency frequency (121.5 MHz) via VHFStation 2. After that, at 15:09:39, the FO reported the Approach controller: "Moscow-Approach, request return of 14-92, radio lost, aircraft in direct mode". The controller issued an instruction to descend to FL 80. Maximum altitude the aircraft gained was 10600 ft (3230 m) (QNE). The crew responded: "Aeroflot 14-92, heading 0-57, descending to FL 8-0". The controller confirmed the clearance for the descent with the maintained present heading. Further flight till the moment of the glideslope capture was performed by means of vectoring.
At 15:09:52, the crew set the selected altitude of 8000 ft (2438 m) and disengaged the FMS speed control mode, set the selected speed of 250 kt (463 km/h) and put the aircraft into the descent mode. In descending, the PIC maintained the indicated air speed by changing the pitch angle and the thrust levers' positions.
Later into the descent while intercepting the localizer the MAK writes:
At 15:15:34, the controller cleared the crew for the ILS Yankee approach, RWY 24 left.
After the permission confirmation, the FO started reading section QRH "F/CTL DIRECT MODE", inter alia: "… Auto throttle should not be used, fly smoothly. … Balance manually. … Speed brake no less than a half. … use Flaps 3. TAWS, landing gear, Flaps 3 on. V approach, V reference plus 10. Landing distance – increase by 1-34. … Speed brake set to full after touchdown. Go-around lever to NTO". At 15:16:54, the controller instructed: "… proceed right heading 210 till localizer capture …".
At 15:17:39, the FO, after the command from the PIC, reported to the controller that the crew was not ready to perform landing approach and requested an «orbit», but then corrected himself: "the circuit" and the controller responded: "… heading 360 to the right".
At 15:18:53, the PIC tried to contact the controller himself: «Aeroflot 14-92, holding area above Kilo November, if possible». The message was not recorded by the controller's recorder. The PIC did not raise this question again.
When performing an orbit flight at 600 m QFE, the PIC could not maintain the altitude precisely. During right turns with roll up to 40°, the deviation from the selected altitude exceeded ±200 ft (60 m), and that triggered multiple aural alerts. The PIC was aware of that, at 15:22:53: "How come… plus-minus 200 feet".
During the orbit flight performance, the FO was reading out the QRH "OVER MAXIMUM LANDING WEIGHT LANDING" section (1.18.7). The weight of the aircraft was about 42 600 kg which exceeded the maximum landing weight by 1600 kg. To gain the maximum thrust in order to be able to perform the go-around, the crew switched off the engine air bleed supply to the conditioning system. The FO also read out that the maximum vertical speed of descend before the touchdown must be no more than 360 ft/min (1.8 m/s). During the standard approach and landing (the Standard Procedures)) the vertical speed recommended by FCOM is 150-200 ft/min (from 0.76 to 1 m/s).
At 15:20:41, the crew started the APU.
At 15:21:38, at 225 kt (415 km/h) the crew initiated the flaps deployment to FLAPS 1 (slats 18°, flaps 3°).
At 15:23:03, after the PIC's order, the FO reported the controller that the crew was ready for landing.
At 15:23:19, at 190 kt (350 km/h) the crew initiated the flaps deployment to FLAPS 2 (slats 24°, flaps 16°).
At 15:23:58 the crew started the landing gear extension.
At 15:24:02, the crew armed the speedbrake system.
Note: Automatic speedbrake deployment mode which can be engaged during the landing and which is inactive when the Remote Control system is in the "DIRECT MODE"». At 15:24:20, at 170 kt (315 km/h), the crew set the flaps into the landing configuration, FLAPS 3 (slats 24°, flaps 25°).
During the landing gear and flaps deployment, the PIC performed stabilizer trimming manually. When the aircraft was set to the landing configuration, the stabilizer deflection angle was ≈3.5° pitch-up and it almost did not change until landing (one short pitch-up pressing was recorded during the glideslope descent).
The aircraft was put to the landing heading at the distance of more than 20 km from the RWY 24L threshold. The final approach fix is located at the distance of 9.3 km.
At 15:24:38, the crew responded to the controller's request that they would perform the ILS approach (the QRH the ILS approach is required with the use of the instrument-landing horizondirector indicator). By 15:25:57, the crew had finished the "DURING LANDING" section checklist.
The crew performed neither the before-landing briefing nor the "APPROACH" checklist.
At 15:26:05, the crew had the following conversation: the FO "Should I set the transponder to 7700? Or leave as it is? Ok, roger.". The PIC: "We could have done it long before, actually." The CVR record does not provide us with clear understanding of the PIC's decision. Nevertheless, at 15:26:31 the crew set the transponder to 7700.
At 15:27:20, the glideslope descent was initiated. The go-around altitude was not set by the crew.
During the approach about 2 minutes prior to landing the MAK describes:
At 15:28:26, at 1600 ft (490 m) QNH (at the radio altitude of 1100 ft (335 m)) the "WINDSHEAR" warning was recorded, it is generated by the crew alerting system based on the wind shear forecast data of the weather radar, accompanied by the voice message "GO-AROUND, WINDSHEAR AHEAD". This warning informs the crew about the possible wind shear enroute. The alert lasted for 11 seconds and included 2.5 warning cycles (5 voice messages, each cycle consisting of 2 messages one after another, with the 1 second interval in-between). The crew had no discussion of this warning triggering.
Note: In the QRH «W/S AHEAD» Section (1.18.8) states that the triggering of this warning during the approach indicates that the crew must initiate the go-around procedure. At the same time in the beginning of the section, there is the notice that if the crew is sure that there is no wind shear hazard and there are no other signs of wind shear, and the RWS is operative, this warning may require no responsive actions from the crew. The same provisions are incorporated into the Flight Operations Manual.
The MAK continued:
At 15:29:22, the FO called out that the landing decision height was close. The PIC confirmed continuing the approach.
At 15:29:31, at 270 ft (82 m) the aural annunciator system informed the crew on reaching the landing decision height minimum, it was repeated by the FO. Starting from that moment, there was noted fast increase of the downward glideslope deviation (up to minus 1.4 dots), which caused the TAWS "GLIDESLOPE" alert triggering to indicate the glideslope deviation The alert was on for 4 seconds. The PIC confirmed hearing the alert by saying "Advisory".
The MAK added that FCOM states the GLIDESLOPE warning below decision height is "advisory", hence a go around was not required.
The MAK then continues the sequence of events:
Simultaneously with the warning triggering, the PIC increased engines power (the trust levers were set to 24° to 23°, which caused the N1 increase up to 77 to 74%). The increase of the engine power caused the increase of the indicated air speed: when the aircraft was passing RWY threshold: at 40 ft (12 m) it was up to 164 kt (304 km/h), and by 16 ft (5 m) it was up to 170 kt (315 km/h). According to FCOM, the required landing approach speed for the actual conditions was 155 kt (287 km/h). This speed was set by the crew as the selected speed. The airline's Flight Operations Manual contains the value plus 20 kt as the criterion for the stabilized landing approach (Section 1.18.9).
Over the RWY threshold, the glideslope deviation was minus 0.9 dot (i.e. below the glideslope). After passing the RWY threshold, the the vertical speed of descent was decreased. The flight parameters during landing are provided in Fig. 8.
At 15:29:54, at 17 ft (5.2 m) aural alert "RETARD. RETARD" informed the crew on reaching the height recommended for the thrust levers to be set to "IDLE" during the flare. The PIC started to change thrust levers positions simultaneously with the alert triggering.
Almost simultaneously with the thrust levers positions changed to "IDLE", the PIC initiated the flare by pulling the sidestick by 8.8° (65% of its travel range). Further on, the PIC's everamplitude increasing pitch idestick inputs were recorded up to the both maximum advanced and maximum retarded positions with a relatively long holding period in the both maximum positions. These inputs caused counter-reversal pitch change (+6…-2º). At 15:30:00, at a distance of ≈900 m from the RWY threshold at indicated air speed of 158 kt (293 km/h), first touchdown occurred. The touchdown occurred at the pitch angle close to zero ( 7 pitch up rate; at the moment of the touchdown, the sidestick was in the maximum retarded position; and during the landing within 0.4 seconds, its position was changed for the maximum advanced), for "threedots", with vertical g-force of no less than 2.55 g.
In "DIRECT MODE", the automatic deployment of the speedbrakes (spoilers) is not provided by the design, and the manual speedbrakes deployment was not engaged by the crew. After the touchdown, the aircraft bounced up for the he height of no more than ≈ 5-6 ft (2 m).
After the aircraft was bounced up, the sidestick continued to be held in the maximum advanced position, which caused the pitch downward rate of up to 10.5°/s, the rapid downward pitch angle decrease to 4° and the repeated touchdown with the nose landing gear touching the ground first.
The second touchdown occurred 2.2 seconds after the first touchdown, at the indicated air speed of 155 kt (287 km/h).
Landing performed with the nose gear touching the ground first, with the high vertical speed and the fully retarded sidestick immediately before touchdown, caused the intensive pitch-up rotation of the aircraft. The maximum pitch rate recorded was ≈25°/s and the vertical g-force was no less than 5.85 g. As the result, the angle of attack and the pitch angle increased, which, due to the remaining significant value of the indicated air speed, caused the repeated bouncing ("progressing bouncing"), despite the sidestick fully advanced position at bouncing up.
During the first bouncing up, when the aircraft was in the air, the PIC switched the thrust levers to the "Maximum Reverse" mode but the thrust reverser doors did not deployed, as there were no weight-on-wheel (WOW) signals. Upon receipt of the left and right main landing gears WOW signals, the reverser doors started to deploy, which was completed after the second aircraft bouncing up movement off the RWY. There was no engine power increase as at this moment, there was no WOW signals again.
During the second bouncing up, the aircraft reached the height of ≈ 15 - 18 ft (5-6 m). In 2-3 seconds after this repeated bouncing up, the thrust levers were set to "Takeoff" mode and the sidestick was pulled to the maximum retard position. This actions may be interpreted as an attempt to perform the go-around, as before that the thrust reverser system was engaged (the reverser doors were in the open position, though starting to close), the engine thrust did not increase.
At 15:30:05, with the indicated air speed of 140 kt (258 km/h), the third touchdown occurred with vertical g-force of no less than 5 g. The type of the markings, left on the RWY after the third touchdown, indicate that the main landing gears were by that moment already partially destroyed ("weak links" were cut off, see Sections 1.3, 1.12 and 1.18.12 of the present Report). The main landing gears collapsed, further on, the aircraft structural disintegration with fuel spillage and fire occurred.
With respect to the oscillating control inputs the MAK wrote:
The Commission carried out preliminary comparative analysis of the approaches performed by the PIC manually (with disengaged autopilot) in «NORMAL MODE», with the emergency flight (Fig. 42). The figure shows that the sidestick movements for the pitch in the emergency flight are characterized by significantly wider amplitude, and are oscillatory, which caused significant changes of longitudinal motion parameters. Similar "sweeping" movements were observed during landing performed in «DIRECT MODE» by other crews of the airline (Fig. 43). Reasons of these peculiarities are being analyzed.
The MAK reported with respect to weak links in the airframe design:
There are safety pins in the RRJ-95 landing gear design which are the elements of a certain level of strength, and they are the first to be destroyed upon the impact of a single design load, determined basing on the load application conditions given in aviation regulations, it is proved by calculations and tests. Destruction of the safety pins causes the gear to move up and backwards and does not cause the damage to the wing box.
The RRJ-95 safety analysis concerning the fuel leakage from the wing box upon the main landing gear destruction was carried out during design studies by modeling of the process of gear destruction when the calculated loads on the landing gear are exceeded. The conditions of application of the load listed in the certification requirements were considered. The certification report was issued. Basing on the calculations the strength and design requirements for safety pins in the gear hinge fitting were determined. In production the safety pins are particularly important parts, the blanks are under special control, and the parts themselves undergo periodic testing.
During operation, the confirmation of the compliance of the serial design to the design parameters was established as a result of an investigation of a serious incident - a very rough landing of the aircraft MSN 95032 with a vertical acceleration of about 4g, as a result of which the safety pins of the right main landing gear were destroyed. The corresponding report has been issued on this incident. In the course of the accident with RA-89098 there were three consequent touchdowns to the RWY with accelerations not less than 2.55g, 5.85g, 5.0g. The airframe endurance design vertical acceleration is 3.75 g.
The acceleration of 2.55 g did not exceed the value, calculated for the cut off of the safety pins of the main landing gear hinge brackets on the rear spar, so at the acceleration of 5.85 g the cut off of the safety pins of the right and the left main landing gear to the rear spar of the wing occurred. During the repeated aircraft lift of the landing gear were in the loose position towards the rear spar. The wing box was not destroyed, according to the records and the fuel gauge data, there were no fuel leakages, there were no structure fragments found on the RWY. At the third runway touchdown, with the allowable vertical loads exceeded, the structure condition did not allow the gear to absorb the loads of the landing hit and they broke down, wing structure was destroyed in the areas of the hinges of the hydraulic cylinders. The aircraft went low and moved on the nacelles and the rear part of the fuselage. The situation described above is not provided for in the current airworthiness standards.
In accordance with the certification rules, the evaluation of secondary impacts of the airframe on the ground after the destruction of the landing gear is not required.
The ground track (Photo: MAK):
Lightning strike traces at the right hand ice detector (Photo: MAK):
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