Sukhoi SU95 at Keflavik on Jul 21st 2013, belly landing
Last Update: March 30, 2016 / 19:38:20 GMT/Zulu time
Incident Facts
Date of incident
Jul 21, 2013
Classification
Accident
Airline
Armavia
Departure
Keflavik, Iceland
Destination
Keflavik, Iceland
Aircraft Registration
97005
Aircraft Type
SUKHOI Superjet 100-95
ICAO Type Designator
SU95
Authorities in Iceland do not rule out a technical problem or human error as cause of the accident. Iceland's RNF have opened an investigation into the accident.
Sukhoi reported the aircraft was conducting test flights to evaluate the CAT IIIa automatic landing system on one engine in strong crosswinds. 3 flight crew and 2 certification engineers were on board. One of the certification engineers received a leg injury during evacuation.
On Mar 30th 2016 Iceland's RNF released their final report concluding the probable causes of the accident were:
The ITSB determined the most probable cause of the accident to be flight crew fatigue.
The ITSB belives the following to be contributing factors to the accident:
- The left A/T was automatically disengaged when the left TQL was at 16.59°, at the moment of touchdown, which was an insufficient thrust setting for goaround
- The right engine was shut off and right engine A/T was disengaged, in accordance with the flight test card, at the moment of setting ENG R MASTER SWITCH to OFF
- Advancing the inoperative engine TQL, resulted in insufficient engine power being available for the go-around
The RNF reported the crew was on their 4th test flight since the test programme started the previous evening. The flight included a test scenario of a CATIIIa approach near maximum landing weight at crosswinds exceeding 19.5 knots with the critical engine failing at 25 feet AGL prompting a go around.
For this purpose a flight certification expert was occupying the observer's seat with access to a test panel permitting to shut the engine down.
A captain (58, Test Pilot License, 12,288 hours total experience, 102 hours on type) occupied the left hand seat and was pilot monitoring, the commander/captain of the flight (45, Instructor and Test Pilot License, 2,789 hours total, 963 hours on type) was pilot flying, the flight certification expert (63, Test Pilot, 10,465 hours total, 419 hours on type) occupied the observer's seat.
All three were well rested when they showed up for the first test flight the previous evening.
The CATIIIa approach was flown on autopilot with flight director engaged, both left and right autothrottles were engaged.
The flight and approach was uneventful. Descending through 17 feet AGL, in accordance with the autoland logic, the thrust levers began to move to idle (retard). At 10 feet AGL the flight certification expert shut the right hand engine down using the engine master switch. The right autothrottle disconnected as result of the engine shutdown, the lever stopped moving and remained at 13.6 degrees, the left thrust lever continued to move towards idle position.
Descending through 4 feet AGL, the left thrust lever had reached idle position in the meantime, the PF disengaged the autopilots using the AP OFF button and called go around. All autopilot and flight director control modes disengaged, the left autothrust channel reverted to speed mode. The aircraft had already slowed below the minimum selectable airspeed, the left autothrust channel therefore started to move the left thrust lever forward.
The PF pressed the TOGA button on the right thrust lever, almost simultaneously the main gear touched down and the weight on wheel sensors indicated ground mode, as result the left authrust channel and left flight director disengaged automatically, the left thrust lever remained at 16.59 degrees.
The PF noticed that TOGA had not engaged and autothrust as well as FD had disengaged and reverted to a manual go around. He advanced the right hand thrust lever, pitched up and commanded the landing gear up.
The landing gear retracted, the airspeed decayed however as the operative left hand engine was not delivering go around thrust with the lever still at 16.59 degrees (the PF had advanced the thrust lever of the inoperative right engine).
The aircraft reached a maximum of 27 feet AGL during the go around, then the airspeed had decayed below 120 KIAS and the aircraft descended again. The PF set the right hand thrust lever to MAX. The PF recognizing the loss of speed and altitude lowered the nose to counter the stall, an aural alert "landing gear not down" activated, the PF checked the engine instruments, saw the right hand engine shut down and the left hand engine at 50% N1, recognized he had been controlling the inoperative engine and moved the left thrust to MAX position. While the left hand engine was spooling up the aircraft hit the ground with its aft lower belly (landing gear was up), the engine cowlings made contact with the runway, the PF retarded both thrust levers, and steered the aircraft towards the runway center line and shut the left hand engine down. The aircraft overran the end of runway 11 and came to a stop 163 meters past the runway end.
The commander (PF) ordered the evacuation of the aircraft, the left forward door was opened, the slide did not deploy however. The right forward door was opened, the slide was blown under the aircraft by the wind. The left rear door was opened, the slide deployed and the crew evacuated via the left rear door. One crew member received minor injuries in the evacuation.
The aircraft received substantial damage. 5 rows of approach lights runway 29 were damaged during the overrun, a runway light at the intersection of runways 11 and 20 was damaged, the asphalt of runway 11 received minor damage.
The left forward slide was found not armed.
The RNF analysed that the aircraft had been defined as a state aircraft, rather than an experimental aircraft, based on diplomatic communication received from the Embassy of the Russian Federation stating "Sukhoi
Civil Aircraft of the Ministry of Industry and Trade of the Russian Federation" and therefore approved the operation in Icelandic Airspace on that basis.
The RNF analysed: "The investigation showed the Sukhoi Civil Aircraft RRJ-95B airplane registered 97005 to have an Experimental Aircraft Airworthiness Certificate issued by the Ministry of Industry and Trade of the Russian Federation and a Special Airworthiness Certificate issued by the Interstate Aviation Committee."
The RNF analysed that during the last accident flight 9 approaches were flown, 7 to runway 20 and the last two to runway 11.
The RNF analysed: "The objective of flight test #978 was to simulate CAT IIIA automatic approach and then to assess the AFCS performance in FD mode during go-around from radio altitude of 2-3 feet, close to the airplane‘s maximum landing weight limit, with the right engine shut down and crosswind exceeding 10 m/s (19.5 knots). This was done as part of extending the type certificate to CAT IIIA certification. For the initiation of automatic go-around, the TOGA button must be engaged prior to touching the runway. Otherwise manual go-around will be required. This is because touching the runway leads to main landing gear strut compression which signals WOW (weight on wheels) to complex avionics hardware on the aircraft. In accordance with EASA AMC48 AWO 316, section “1.2 inadvertent go-around Selection”, an inadvertent selection of go-around mode after touchdown should have no adverse effect on the ability of the aircraft to safety rollout and stop. As a result of this EASA design requirement, the TOGA switches are automatically disengaged after touchdown to prevent inadvertent selection of goaround mode after landing."
The RNF analysed the go around:
The pilot flying pressed the TOGA button on the right TQL to initiate a go-around and, according to the cockpit voice recorder, called out “go-around.” Almost simultaneously, at 05:23:28:70, the main landing gear touched the RW and as a result of left main LG shock strut compression a/c avionics complex received WOW (weight on wheels) signal.
In response to WOW signal and in accordance with AFCS logic and SC AWO 316 requirements, the left A/T disengaged automatically. At the moment of left A/T disengagement, the left engine TQL was at 16.59°.
The pilot flying noticed at the primary flight display that the go-around mode had not engaged. He also noticed that the flight director was not available. After the AP disconnected, the pilot flying attempted go-around by pressing the TOGA button on the right throttle immediately prior to the landing gear touching the runway at 05:23:28.7. The FTI52 recorded a short “pulse” of GA mode engagement, which confirms that the signal from the TOGA button reached the auto flight system and its attempt to engage the GA mode on this computational step.
At 05:23:29.5, the left LG WOW status appeared. Therefore, in accordance with the auto flight system logics, the A/T system was disconnected. GA engagement was inhibited by an asynchronous acquiring of WOW status by the two auto flight system master channel computers. The GA was not displayed in PFD. So, at 05:23:29.5 the following events had simultaneously occurred:
Actual landing touchdown, A/T disconnect and GA mode engagement inhibit. The main landing gear only touched the runway at 05:23:28:70 for a brief moment (0.4 seconds) and then the airplane started to climb again at 05:23:29:10.
At 05:23:30 the right engine’s SOV53 closed as it had previously been set to failure mode by the ATTCS panel and shut down using the ENG MASTER SWITCH.
At this point the AP, the FD, the left A/T and the right A/T were all selected OFF, as was the right engine. The left engine was delivering thrust at TQL 16.59°, slightly higher than idle. Manual input from the operational engine (left engine) was therefore required to perform the go-around.
The pilot flying started to perform go around in manual mode, by setting the right (inoperative) engine TQL to TO/GA. The pilot flying pitched the airplane up and the airplane started climbing.
According to the CVR, no POSITIVE CLIMB callout was made.The pilot flying ordered landing gear retraction at 05:23:34. The landing gear was selected to up at 05:23:36 by the pilot monitoring.
The left TQL remained at 16.59 deg, until the pilot flying discovered his mistake two seconds before the airplane hit the runway and put the left TQL to TO/GA.
By then, the throttle input on the left engine was too late.
The RNF analysed the hours prior to the accident flight were spent as follows (time in local):
8:30 -10:00 – preliminary preparations to flight in the hotel;
10:00 – 12:00 – rest in the hotel;
12:00 – 13:00 – lunch in the hotel;
13:00 – 18:00 – rest in the hotel;
18:00 – 18:30 – dinner in the hotel;
18:30 – 19:00 – transfer to the airport;
19:00 – 19:35 – preflight training;
19:35 – 19:45 – transfer to the aircraft.
19:57 – 21:40 – first flight No 975;
22:35 – 00:24 – second flight No 976;
01:16 – 03:07 – third flight No 977;
04:03 – 05:2 – forth flight No 978.
The RNF continued: "During the on-site investigation it was noted by the ITSB investigators that the flight crew was reported severely fatigued. Shortly thereafter, the ITSB interviewed the flight crew. Fatigue was reported in the interviews, where it was stated that all the crew was both mentally and physically tired." and subseqently analysed: "The accident occurred during night at 05:23, at the time of day when the performance and cognative function of the pilot flying would have been at its low point per the above analysis. An indicator of flight crew fatigue was that standard callouts were not made when initiating the go-around. The pilot flying attempted the go-around with the use of the inoperative engine TQL and 15 seconds passed before he corrected this."
Metars:
IKF 210630Z 16019KT 9000 -DZ BR FEW006 BKN008 OVC011 10/10 Q1015
BIKF 210600Z 16019KT 6000 -DZ FEW005 OVC008 10/10 Q1015
BIKF 210530Z 16021KT 9999 -DZ BKN005 OVC007 10/10 Q1015
BIKF 210500Z 16018G24KT 9999 SCT004 OVC008 10/10 Q1015
BIKF 210430Z 16018KT 7000 -DZ BR FEW002 OVC005 10/10 Q1015
BIKF 210400Z 16017KT 1700 -DZ BR OVC003 10/10 Q1015
BIKF 210330Z 15021KT 1200 -DZ BR BKN001 OVC003 11/11 Q1015
BIKF 210300Z 14021KT 2000 DZ BR BKN001 OVC003 11/11 Q1015
BIKF 210230Z 14020KT 1500 DZ BR BKN002 11/11 Q1015
BIKF 210200Z 14021KT 6000 DZ BR BKN003 OVC005 11/11 Q1015
Incident Facts
Date of incident
Jul 21, 2013
Classification
Accident
Airline
Armavia
Departure
Keflavik, Iceland
Destination
Keflavik, Iceland
Aircraft Registration
97005
Aircraft Type
SUKHOI Superjet 100-95
ICAO Type Designator
SU95
This article is published under license from Avherald.com. © of text by Avherald.com.
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