20 Sep 2019 - Final report published into Yan Air 737-400 UR-COI 737-400 Loss of cabin pressure on 23 Jun 2018
On 23 Jun 2018 A Yan Air 737-400, UR-COI (24550/1793), was operating Kharkiv (UKHH) to Batumi (UGSB). It had despatched with ENG # 2 bleed INOP and APU INOP. During the climb, the was a left engine "Bleed Trip Off". The crew managed to resume air extraction from the left engine for a while by pressing the reset button of the Trip Reset auto-off, but at 16,000 feet altitude began to rise in the cockpit. The crew levelled off at FL200. The altitude in the cockpit continued to increase and the crew requested to reduce to 10,000 feet and change course to land at Kiev base (Zhulhany), due to heavy thunderstorm activity in the area of departure aerodrome and excess landing weight at the airport landing mass. The cabin altitude continued to increase during descent, and the CABIN ALTITUDE signal panel sounded when 10,000 feet was reached. The QRH crew complied with the relevant NNC Donned oxygen masks and provided emergency oxygen supplies.
Due to the fact that the cabin pressure and altitude were not controlled, the crew, according to QRH, activated the "PASS OXYGEN" oxygen mask in the passenger cabin. After reducing the flight altitude to 10,000 feet, the crew leveled off. During this event, the crew did not declare an emergency. At 15:20 UTC the crew landed at the Kyiv (Zhulhany) airport. During the reduction and use of oxygen, the crew and passengers were not injured.
On 19 Sep 2019 the NBAII published their final report into the incident.
It concluded that:
Extracts of the report are given below
*** Updated 23 Nov 2020 ***
23.06.2018 while flying ANR223 on Kharkiv Airlines (UKHH) - Batumi Airlines (UGSB), on a Boeing 737-400 aircraft, the UR-COI registration number of YANEIR LLC, a serious incident occurred during which flight members crew needed emergency oxygen.
After departure from Kharkiv Airport at 14:18 UTC, during the process of climbing up to FL240 (24000 feet), an alarm was automatically triggered by the automatic shut-off of the air extraction from the left engine "Bleed Trip Off" with the MEL-deactivated pressure selection and control valve " PRSOV »from the right engine. The crew managed to resume air extraction from the left engine for a while by pressing the reset button of the Trip Reset auto-off, but at 16,000 feet altitude began to rise in the cockpit.
The crew reduced the vertical speed of climb and, in agreement with ATC, stopped the climb at an altitude of 20,000 feet. The airplane again triggered the automatic shut-off of the left bleed trip off engine and, subsequently, pressing the "Trip Reset" button did not resume the air supply.
The altitude in the cockpit continued to increase and the crew requested to reduce to 10,000 feet and change course to land at Kiev base (Zhulhany), due to heavy thunderstorm activity in the area of departure aerodrome and excess landing weight at the airport landing mass.
The cabin altitude continued to increase during descent, and the CABIN ALTITUDE signal panel sounded when 10,000 feet was reached. The QRH crew complied with the relevant NNC (page 2.1.), Donned oxygen masks and provided emergency oxygen supplies.
Due to the fact that the cabin pressure and altitude were not controlled, the crew, according to QRH, activated the "PASS OXYGEN" oxygen mask in the passenger cabin. After reducing the flight altitude to 10,000 feet, the crew leveled off.
During this event, the crew did not declare an emergency. At 15:20 UTC the crew landed at the Kyiv (Zhulhany) airport. During the reduction and use of oxygen, the crew and passengers were not injured.
The aircraft maintenance was performed in accordance with the applicable operational technical documentation of the Boeing aircraft. All modifications and airworthiness directives required at the time of this report have been complied with. Aircraft time after the last periodic MOT in the amount of 1A Check, CRS # YA-COI-18-30 from 06.06.2018, was 179 hours, 72 cycles.
The last operational maintenance of DY / WEEKLY CHECK was held on 23.06.2018. in the a / p Kyiv Zhuliany before departure (logbook page 18578). The pre-flight inspection of the aircraft was performed by the aircraft crew on 23.06.2018. at the departure airport of Kharkiv (logbook page 18580).
Logbook and deferred defects
In the logbook of the airplane, from 20.06.2018 to the date of occurrence of 23.06.2018, records of the remarks concerning the operation of the air supply system in the pneumatic system of the airplane are made, namely:
According to the list of deferred maintenance, the aircraft had six deferred defects, two of which were related to the operation of the pneumatic system and supercharging, namely:
The commission's analysis of operational and technical documentation, evaluation of the organization and maintenance of aircraft maintenance and maintenance showed that the technical operation of the Boeing 737-400 aircraft registration number UR-COI, was mainly carried out in accordance with the Technical Program servicing the aircraft of the airline of the company "JanEyr", the guidance documents of the aircraft manufacturer and the State Aviation Service of Ukraine.
Boeing 737-400 UR-COI installed L3 Aviation Solid-State Flight Data Recorder (SSFDR) parametric recorder.
Information was read based on NAU using standard equipment, computer files were provided for analysis. After decryption of flight information it became clear that the binary signals of the system of signaling the failure and operation of the pneumatic and air-conditioning system, the flight information recorder was not registered both during the occurrence of this event and during the execution of 6 previous flights (Fig.8), which indicates a partial malfunction of the recorder or DFDAU device that generates signals that are logged by the drive.
To find out the reasons that could lead to the absence of binary signals of the parametric registrar, the commission checked the order of control of the parametric registrar of the flight information of the aircraft by the airline. The Commission requested that the airline provide the results of a mandatory annual inspection of the aircraft's QAF, as well as testing the QAF while performing the latest C1 Form MA, but no requested Commission information was provided.
The absence of the flight attendant to record flight alarm information on the dangerous altitude in the cabin, as well as the operation of the pneumatic and air-conditioning system, made it difficult to analyze the sequence of occurrence of the hazardous situation, crew actions and increase the time required to investigate the event.
During the investigation, in order to find out the circumstances of this event and the results of troubleshooting and troubleshooting of the airplane airplane system, the commission decrypted two flights, namely on 23.06.2018 and 22.06.2018. For greater clarity of the spatial position of the aircraft during the flight, the report provides images from FlightRadar 24. The dispatcher-crew negotiation statement below is set out to eliminate conditions that adversely affect flight safety.
2.1. Commission work:
During the investigation (analysis) of the event, the commission carried out the following work to find out the circumstances, causes and related factors: - the explanatory notes of crew members and technical staff were analyzed; - the analysis of the work of the crew during the flight, including the materials of the JCC;
2.2. Based on the study of the explanatory notes of the aircraft crew, flight and technical documentation, analysis of the QMS materials, the commission established the following course of events. 23.06.2017 Boeing 737-400 UR-COI crew consisting of: CPS, 2nd pilot, cabin crew members (10 people - all Ukrainian citizens), prepared for ANR223 flight on the route Kharkiv (UHF) - a / n Batumi (UGSB). In the course of preparation for flight the CPS found that according to the list of deferred TO (DMI), the aircraft did not work - auxiliary power unit (“APU is inop”) and air extraction from engine # 2 (“ENG # 2 bleed is inop” ).
According to the procedures in MEL, the PRSOV valve from engine # 2 was deactivated in the closed position, and when the air was removed from engine # 2, the flight altitude was limited to FL 250. Note: In the event of failure of two air supply systems from engine # 1 and # 2, the compressed air supply may be provided from the operating DSU up to a height of 17,000 feet (FL 170).
That is, during the scheduled flight, the airplane airplane system will have only one compressed air source from engine # 1, and when the engine is idle, if the compressed air supply from engine # 1 is stopped, the airplane refueling will stop. Assessing the risks (the air intake from the left engine was good, the duration of the flight - two and a half hours - the load on the left ВLEED is small), the CPS decided to take off.
Note: Given that sealing and air supply failures on airline aircraft and CAs are generally quite frequent, and malfunctioning to stop air supply from the left engine has been repeated many times during previous flights, the commission considers that the likelihood of a compressed air supply system failure from engine # 1 was high and risk was not acceptable.
According to the distribution of duties in the cockpit, the pilot pilot (PF) was the second pilot and the supervisor (PM) of the CPS. At 14:18 the crew took off from the runway 25 of Kharkiv (UKHH) airport. Take-off, initial climb, landing gear and wing mechanization are performed in accordance with the operating documentation. The climb was carried out at a vertical speed of 2000 to 3300 ft / min. After crossing the altitude of 10,000 feet (FL100) at 14:22:27, the vertical speed began to decrease from 2000 to 1050 ft / min at 14:23:00, and at 14:23:01 it again began to increase to 1730 ft / min at 14: 23:26 at an altitude of 11310 feet.
During the subsequent climb at approximately 14:23:42, at an altitude of 11,720 feet (from the words of the crew at the 12,000-foot echelon), the Master Caution alarm and the BLEED TRIP OFF control panel on the air conditioning system control panel worked. Note: The left BLEED TRIP OFF indicated that the left engine had been withdrawn and that air was supplied to the air-conditioning system and maintained the required cabin pressure.
The crew stopped climbing and from 14:23:42 to 14:24:26 maintained an altitude of 11720 feet. According to QRH, the crew performed the appropriate NNC (p.2.8. "BLEED TRIP OFF"), after which the "BLEED TRIP OFF" board went off, indicating that the air intake system was restored from the left engine. After the system was restored, the crew continued to climb up to FL160 at a vertical speed of 140 to 1020 ft / min. Note: from the 14:25:56 negotiation statement between the Kharkov Radar dispatcher and the crew, the crew reported to the controller that FL160 had been recruited.
According to the crew, after a while the situation repeated, the alarm "Master Caution" and the left panel "BLEED TRIP OFF" on the control panel of the air conditioning system and the crew again performed NNC (2.8.) "BLEED TRIP OFF". The system was restarted. After the system was restarted, the crew continued to climb up to the FL240 flight level assigned by the flight attendant. Note: from the 14:25:56 - 14:26:13 negotiation statement between the Kharkov Radar Manager and the crew, the dispatcher gave the command to recruit FL280, but the crew replied that the final flight FL240 and the FL280 was not able. The dispatcher allowed climbing to the FL240 level, to which the crew gave the appropriate confirmation.
According to the crew at 16000 feet (at 14:29:55 at 16000 feet according to ZOK), the Master Caution alarm and the BLEED TRIP OFF control panel on the air conditioning control panel again worked. The crew again performed NNC (2.8.) "BLEED TRIP OFF" and the system resumed, but continued to rise in altitude in the cabin. At 14:31:19, at an altitude of 17210 feet, the crew reduced the speed of flight altitude, and then, having reached an altitude of 20,000 feet, at 14:36:24 transferred it to level flight.
At 14:36:19 the Dnipro Radar dispatcher asked the crew whether he could gain FL240 echelon, which received a negative response from the crew and confirmation that the aircraft had reached FL200 altitude and was following 180 °. At 14:36:38, the dispatcher confirmed the information received and instructed the crew to support the FL200 echelon. Note: according to the KLA information at 14:36:07 the flight was 359 °, not 180 °, as declared by the crew.
According to the crew, after a while the "BLEED TRIP OFF" board again worked. The crew again performed NNC (2.8.) "BLEED TRIP OFF", but the system did not recover. Due to repeated repetition of the BLEED TRIP OFF scoreboard, the crew decided to suspend the task, lower the aircraft to 10,000 feet and head to a spare base airfield in Kyiv (Zhulhany), due to thunderstorm activity in Kharkiv RC, and the need to prevent fuel consumption to prevent landing at the Kharkiv airport to exceed the maximum landing weight.
Note: According to the ATC report, the crew did not request a reduction to the altitude of 10,000 feet but tried to continue their flight to Kiev (Zhulhany) airport for FL200. In addition, the crew continued to change their flight to Kiev (Zhulhany) airport without requesting permission from the controller.
At 14:36:52 the crew confirmed the flight level of FL200 and asked the dispatcher permission to fly to Zhuliany at FL200 level. The controller confirmed the information received and the fact that the crew was sending to Zhuliany.
At 14:37:28 the crew requested the controller to turn the course on Zhuliany. The controller asked the crew whether he could follow the 300 ° course, to which the crew agreed.
At 14:38:07 the crew contacted the dispatcher during which he said: «Break, break. YANAIR two two three it necessary to down level follow heading three zero zero. It necessary down to Zhulyany ». That is, the crew decided to immediately reduce and made a request for a reduction to Zhuliany. Note: For a minute, the crew, using the non-standard "necessary necessary down" terminology, tried to obtain permission from the dispatcher for the reduction, but the dispatcher could not understand the crew's request for a reduction, but only confirmed the flight course to Zhulyany. The use of non-standard terminology may indicate that the crew was in a state of stress and high emotional stress in the current situation.
At 14:39:08 the crew contacted ATC, confirmed the direction of flight to Zhuliany and asked ATC to descend to FL100 ("Descend, request descend flight level one zero zero").
At 14:39:17 ATC confirmed the information received and gave the crew permission to descend to FL100, transit through FL120, pressure QNH 1006.
At 14:39:25 the crew confirmed the pressure value and reported to the dispatcher the reduction to the height of FL100, thanked and informed the course of the direction to Zhuliany.
At 14:39:38 ATC asked the crew about the reason for heading to Zhuliany.
At 14:39:52 the crew replied about some problems, but the controller at 14:40:13 said that the message was unintelligible and once again asked to repeat the reason for heading to Zhuliany, but the crew did not answer the reason for heading to Zhuliany. Multiple requests from ATC to explain the reason for heading to Zhuliany, the crew did not respond.
At 14:45:28 ATC last asked if he could tell the reason for going to Zhuliany and suggested - "through the weather" or not? To which the crew at 14:45:36 answered, "because of the weather". Thus, after the occurrence of a non-standard situation, the crew did not inform the dispatcher about the malfunction of the aircraft, the reason for the need to reduce to FL100 and heading to the Kiev (Zhuliany) airfield. In the process of lowering the crew repeatedly tried to restore the system, but the height in the cabin continued to increase. Note: Increasing cabin altitude means lowering the air pressure in the cabin and passenger cabin.
From the analysis of the DOC decryption materials, the crew made a descent from the FL200 level to the FL100 level for 4 min 54 sec with a maximum flight speed of 301 knots and a maximum vertical descent rate of 2970ft/min (15m/s), which did not exceed the CLE limits. The CABIN ALTITUDE signal panel was activated during the descent, when the cabin height was 10,000 feet. The QRH crew performed the appropriate NNC (page 2.1.) "CABINE ALTITUDE WARNING", put on oxygen masks, applied 100% oxygen, switched on the seat belt buckle, switched the "PASS" switch OXYGEN "to" ON "and continued to descend to 10,000 feet. At an altitude of 10,000 feet, the crew moved the plane horizontally. Note: The crew activated the "PASS OXYGEN" oxygen mask in the passenger compartment due to the fact that the air intake from the left engine had not recovered and the cabin pressure was not controlled.
2.3. The NBRSA and the chairman of the commission received a complaint from the passenger of this flight about the malfunction of oxygen masks. According to the statement of the passengers of the aircraft occupying the seats 16 D, E, F of the right block of chairs, after the fall of the oxygen masks and their activation of oxygen in the masks did not enter. They called in a flight attendant to help with oxygen masks, but after unsuccessful attempts, two passengers were asked to take up vacancies where oxygen masks worked and provide oxygen, but one remaining 16-seat passenger was not provided with oxygen until the plane was safe. altitude. The commission failed to verify the technical status of the oxygen generators from the site 16 D, E, F of the right armchair block because the treatment came after the oxygen generators were disposed of.
2.4. Based on an analysis of the performance of the pneumatic system described in section 1.6.4, it can be concluded that the multiple Bleed Trip Off timer operation during flight was due to inefficient cooling of the primary left air cooler Precooler due to its clogging, which resulted in the closure of the left engine's PRSOV and the shutdown of air supply to the system to maintain the required pressure in the cabin.
The cause of the serious incident with the Boeing 737-400 PS, UR-COI registration number operating ANR223 on the route Kharkiv (UKHH) - Batumi (UGSB):
- complete cessation of compressed air supply to the airplane air system by automatically closing the left engine's PRSOV valve and adjusting the pressure due to an increase in compressed air temperature above 490 ±10°F (254 ±6°C). clogging of the primary cooler (Eng. Precooler) of the left engine with the PRSOV of the right engine deactivated and the defective DSU.
Event Category: SCF-NP (system or component failure or power failure). Factor: human.
Using non-standard R/T phraseology in the event in radio calls with ATC to reduce the aircraft to a safe altitude;
Insufficient level of training and qualification of technical personnel to repair defects in the airplane airplane system.
Recommendations for improving flight safety:
4.1. State Aviation Service of Ukraine:
4.2. YANEIR Airlines PJSC:
4.3. Airport Operators:
Carry out preliminary questioning of the crew and passengers of the aircraft regarding the possible circumstances of the occurrence of an aviation incident or serious incident, as well as the known facts that may be related to them.