UTAir B735 in Usinsk on Feb 9th 2020, landed short of runway, gear collapse and runway excursion on landing

Last Update: March 14, 2021 / 16:50:04 GMT/Zulu time

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Incident Facts

Date of incident
Feb 9, 2020

Classification
Accident

Airline
UTAir

Flight number
UT-535

Departure
Moscow Vnukovo, Russia

Destination
Usinsk, Russia

Aircraft Registration
VQ-BPS

Aircraft Type
Boeing 737-500

ICAO Type Designator
B735

A UTAir Boeing 737-500, registration VQ-BPS performing flight UT-535 from Moscow Vnukovo to Usinsk (Russia) with 94 passengers and 6 crew, was on final approach to Usinsk's runway 13 at about 12:21L (09:21Z) but touched down hard about 15 meters ahead of paved surface of the runway and went through heaps of snow. Both main gear struts collapsed, the aircraft skidded on its nose gear and belly to a stand still off the runway causing damage to a wing resulting in a fuel spill. No fire broke out. The passengers evacuated via slides and overwing exits. The aircraft received substantial damage. There were no injuries (though there were claims of one or two injured passengers).

The airline reported the ILS and approach lights were out of service. However, the approach to Usinsk was possible with the assistance by ATC.

No Metars are available for Usinsk.

According to local weather data the winds were blowing from 150 degrees at 6 m/s (11 knots) gusting 11 m/s (20 knots), temperature was -21 degrees C, dew point -23 degrees C, visibility 1100 meters, QNH 1063 hPa, RVR 1700, 1100 and 1400 meters, cloud ceiling 450 meters/1500 feet.

According to NOTAMs both ILS and approach lights runway 13 were not operative.

On Feb 10th 2020 the Interstate Aviation Committee (MAK) announced they have formed a commission to investigate the accident. The commission has already started to work. According to available information so far there had been no injuries, the aircraft received damage.

On Feb 11th 2020 Rosaviatsia reported the aircraft landed on runway 13 (heading 134) but touched a snowy parapet about 15 meters before the runway with its main gear. The right main gear was torn off and came to rest 1000 meters down the runway, the left main gear fractured and came to rest under the left wing of the aircraft. The aircraft came to a stop about 2000 meters down runway 13 about 80 degrees off the runway heading. Apart from both main gear legs being damaged both left and right inboard flaps were damaged above the landing gear. The right main gear doors penetrated the right wing. There were no injuries amongst the 94 passengers and 6 crew.

On Feb 11th 2020 the airport reported the runway adhesion coefficients were between 038 and 035 at a rate of 032. The airport stated: "At the time of the plane’s landing, Usinsk Airport was operating normally and was fully prepared to receive aircraft. The airport in Usinsk operates in full compliance with federal aviation regulations. Not a single remark has been received from any crew in the last two years."

On May 28th 2020 the MAK silently (without any announcement or entry in the updates' list) released their interim report stating the aircraft impacted a wall of snow of 1.1 meters height, that had been created by snow removal works, with its main gear 32 meters before the runway threshold. The aircraft subsequently touched down 30 meters past the runway threshold, the right main gear collapsed, the left main gear fractured. The aircraft skidded along the runway and came to a stop 2,155 meters past the runway threshold.

According to ATIS the visibility at the aerodrome was 1300 meters, the glide path transmitter as well as the approach lights were not operating, apron and taxiways were covered with snow, the runway was covered with 2mm frost, the runway friction factor was 0.38. The visibility did not permit an approach to the runway.

The crew however hoped for weather improvement and decided to continue the flight to Usinsk and perform a GNSS (RNAV) approach to the aerodrome.

While descending towards Usinsk the latest weather information indicated a visibility of 1600 meters (RVR 1600, 1300, 1400), cloud ceiling at 450 meters, the weather conditions were just at the minima required for landing. ATC cleared the aircraft for the GNSS approach to runway 13.

The crew performed the approach with autopilot engaged in LNAV and VNAV and autothrust active, the modes remained active until the aircraft was shut down. The aircraft interecepted the final aprpoach at 2200 feet AGL and 190 KIAS, flaps had already been set to position 5. ATC reported the RVR was now 1800, 1700 and 1700 meters, the crew announced they were continuing for landing. The landing gear was lowered, the flaps extended to 30 degrees. While settling in the final descent the wind reduced from 40 to 14 knots. The aircraft descended through 1530 feet AGL at 143 KIAS slightly below the glide path at 1570 feet.

Descending through 1000 feet AGL the crew received the clearance to land on runway 13. At 700 feet both crew were visual with the runway, at 620 feet the autopilot and autothrust were disconnected. The captain (55, ATPL, 17,852 hours total, 7,672 hours on type) instructed the first officer (44, 6,595 hours total, 4,989 hours on type) to also recycle the flight directors and set the altitude target for the go around. The first officer confirmed the flight directors were switched off and on, and the altitude target was set to the go around altitude. The captain took control of the aircraft. The first officer commented they were below the glide path, the captain should not go below the glide path, the captain confirmed. The EGPWS announced 100 feet AGL, at 60 feet AGL the first officer again commented they were below the glide path, this time there was no response from the captain, however engine thrust was increased. The aircraft descended at 140 KIAS and 600 fpm. The EGPWS announced 50 and 30 feet, no correction to the glide path was yet made, the main gear impacted the snow bank 32 meters ahead of the runway threshold, which was 1.1 meters (3.5 feet) high. At that point the aircraft was doing 138 KIAS at 3 degrees nose up and experienced a vertical acceleration of +1.6G, a longitudinal acceleration of -0.7G and a lateral acceleration of -0.6G. The aircraft touched down on the runway 30 meters past the runway threshold at +1.86G. However, the air/ground switches remained in the position air. The right main gear separated from the airframe, the left main gear fractured and collapsed. The aircraft skidded to a halt on the engine reverser covers and the fuselage.

The captain did not recognize the main gear had collapsed even though the first officer suggested to evacuate. THe captain believed it was fine with the exception of nose wheel steering, which didn't appear to work. Only when the flight attendants reported fuel was leaking from the right hand side (which in fact was hydraulic fluid however), the captain decided to evacuate the aircraft.

There were no injuries.

ON Mar 14th 2021 the MAK released their final report in Russian only (Editorial note: to serve the purpose of global prevention of the repeat of causes leading to an occurrence an additional timely release of all occurrence reports in the only world spanning aviation language English would be necessary, a Russian only release does not achieve this purpose as set by ICAO annex 13 and just forces many aviators to waste much more time and effort each in trying to understand the circumstances leading to the occurrence. Aviators operating internationally are required to read/speak English besides their local language, investigators need to be able to read/write/speak English to communicate with their counterparts all around the globe).

The report concludes the probable causes of the accident were:

The accident of the Boeing 737-500 VQ-BPS occurred during the landing as result of collision of the aircraft with a snow bank of 1.1 meters height 32 meters ahead of the runway threshold (within the paved safety area of the runway), that caused damage to the main gear struts and subsequently their collapse while travelling down the runway.

The accident has been caused by a combination of following factors:

- the existance of contradictions in Federal Aviation Regulations in Airspace of the Russian Federation, the airline's standard operating procedures and the operations manual of th eaircraft with respect to temperature corrections to barometric altimeter readings at low temperatures of ambient air

- The Usinsk aerodrome operator's failure to comply with FAP-262 for aerodromes required a paved safety area free of snow banks

- The Usinsk aerodrome operator's failure to eliminate shortcomings in the winter operations of the aerodrome that were noted in a Rosaviatsia commission inspection on Jan 22nd 2020

- Lack of risk assessment by the airline of conducting baro-VNAV approaches in the presence of factors hampering such approaches (low ambient air temperatures, presence of snow cover on surfaces, drifting snow/snowstorm, significant changes in terrain profile before the runway, no approach guidance lights like PAPI) as well as lack of according recommendations to crews of how to conduct such approaches including the transition to visual approach, and lack of training of crews

- insufficient assessment of present hazards and threats during pre-landing preparations by the crew reaching an insufficiently substantiated decision to perform a RNAV (GNSS) approach under control of the autopilot in LNAV/VNAV without introduction of correction for the low ambient temperature which led to the approach flown below the glidepath

- performing a flight below extended glidepath after the autopilot was disconnected and transition to manual control without attempting to acquire the correct glide path

- the captain may have been under the illusion of being high on the glide path due to the snow covered surface, blowing snow and the presence of a ravine directly in front of the runway's paved surface in absence of PAPI lights, which led to incorrect estimation of the aircraft's height, lack of timely call outs by the first officer leading to crossing the begin of paved surface of the runway significantly below the required height.

The MAK analysed that the crew had checked ATIS while nearing Usinsk, which provided a visibility of 1300 meters runway 13, PAPI and runway approach lights were inoperative, taxiways and apron slippery covered with snow, runway 13 covered with frost 2 millimeters, braking action medium (friction value 0.38). This visibility did not permit to perform the approach.

The crew discussed the weather conditions and decided to continue to Usinsk hoping for weather improvement. This decision was not in conflict with the regulations.

In the following briefing the crew identified their landing aerodrome as well as their alternate aerodrome, the approach method, the method to apply brakes after touch down (maximum braking), the wind components and friction values were assessed, checked the fuel remaining and computed their waiting time available before diverting to their alternate, the crew reviewed the arrival and approach procedures, actions on go around and diverting to the alternate and entered all relevant data in the flight management system. The crew computed their Vapp at 140 KIAS (Vref30 at 129 KIAS).

The crew decided to carry out the approach in RNAV (GNSS) mode, even though the aircraft was not approved for the RNP Approach specifications. The decision by the commander to perform a RNP approach thus was unreasonable.

The crew did not discuss the risks associated with the selected RNP approach method, in particular not the low ambient temperatures while using a barometric VNAV approach method, limited visibility, difficult terrain, snowy surfaces and no PAPI lights. The commission considers the thread and error management by the crew was insufficient.

The crew subsequently requested descent from their cruise level for the approach to Usinsk. While descending towards Usinsk the crew again checked ATIS which now indicated 1600 meters vibility, the minimum required for the approach. The crew contacted Usinsk Tower, received the QFE at 989 hectopascal and cleared for the GIGES 1L standard arrival route. Tower indicated that the LOC runway 13 was available, the commander queried whether they could use the ILS then, the first officer however contradicted stating that the glideslope was not operative on the ILS. The captain thus decided to leave everything as it was setup and continued with the LNAV/VNAV approach with a cross check by NDB.

Due to the ambient temperature of -21 degrees C below the standard temperature of +15 degrees C as indicated by ATIS the barometric altimeters indicated about 280 feet higher than the actual altitude.

The crew configured the aircraft for landing and monitored the flight progress and verified the accuracy of the RNP approach establishing that the accuracy was better than required, thus decided to continue. The captain however commented: "hmmmm, that whiteness of course" which probably indicated the difficult conditions of visual orientation.

Throughout the final descent the crew verified the baromatric altitude readings with the approach chart, all of them were within 100 feet.

Boeing reviewed the aircraft system performance and found all systems including the FMC issuing commands to the autopilot to follow the glidepath based on barometric altitudes were working as designed.

The crew acquired visual contact with the runway, the commander decided to continue the approach when the aircraft was descending through 960 feet indicated about 1.9nm from the runway threshold. The aircraft reached Minimums, the commander again decided to continue the approach. Descending through 660 feet indicated altitude the commander disengaged the autopilot and continued manually, the flight directors were disconnected and the go around altitude was set. The aircraft descended at 145 KIAS and 690 to 590 fpm rate of descent.

In the final stages of the descent, while following the correct barometric altitude indications without the adjustment for low ambiert temperature, the aircraft was actually 50 feet below the intended glide path.

Without the temperature correction the aircraft would thus cross the runway threshold at an incorrect, less than required height, which, if the crew attempted to correct, required to unbalance the aircraft in visual flight without any instrument indications to verify the aircraft's position related to the runway in limited time.

PAPIs would have been significant assistance to the crew to verify their flight trajectory. However, the risks associated with the lack of PAPIs should have been carried out by the airline dispatch prior to the flight with the according instructions to the flight crew. In this case the airline did not provide the crew with recommendations for the approach.

When the EGPWS sounded the 100, 50 etc. calls, there was no reduction in the rate of descent. The main gear collided with snow banks of 1.1 meters (3.6 feet) height 32 meters before the runway threshold. The aircraft should have crossed the runway threshold at 50 feet above the runway surface.

(Editorial note: while translating the Russian report I did not discover any reference to the radio altimeter except for the EGPWS height call outs, all altitude computations were based on altitudes based on QNH, altitudes based on QNH corrected for ambient temperature, QFE altitude and QFE altitudes corrected for ambient temperatures).

FAP-262 requires the aerodrome operators to clear the (paved) safety areas of runways, ahead of the runway threshold and past the runway end, clear of snow. As such the aerodrome operator did not comply with the requirements.

Related NOTAMs:
(TS6225 / 19 NOTAMR TS3631 / 19
SH) UUYY / SHLAAS / IZH / NBO / A / 000/999 / 6600Ñ05722Â003
A) UUYS B) 1912130810 C) 2005151500 RAS4
E) Runway 13: LIGHTS OF APPROXIMATION DO NOT WORK.)

(TS0127 / 20 NOTAMR TS6431 / 19
SH) UUYY / SHCHIGAS / I / NBO / A / 000/999 / 6600Ñ05722Â015
A) UUYS B) 2001140610 C) 2002141500 RAS4
E) RUN 13: ILS TIME DOES NOT WORK ).
Incident Facts

Date of incident
Feb 9, 2020

Classification
Accident

Airline
UTAir

Flight number
UT-535

Departure
Moscow Vnukovo, Russia

Destination
Usinsk, Russia

Aircraft Registration
VQ-BPS

Aircraft Type
Boeing 737-500

ICAO Type Designator
B735

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This article is published under license from Avherald.com. © of text by Avherald.com.
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