Bhoja B732 at Islamabad on Apr 20th 2012, impacted terrain on approach
Last Update: January 22, 2015 / 12:01:08 GMT/Zulu time
Incident Facts
Date of incident
Apr 20, 2012
Aircraft Registration
AP-BKC
Aircraft Type
Boeing 737-200
ICAO Type Designator
B732
The ineffective automated flight deck management in extreme adverse weather conditions by cockpit crew caused the accident. The ineffective automated flight deck management was due to various factors including; incorrect selection of cockpit crew on account of their inadequate flying experience, training and competence level for Boeing 737-236A (advanced version of Boeing 737-200 series), absence of formal simulator training in respect of FO for handling an automated flight deck, non-existence of cockpit crew professional competence / skill level monitoring system at operator level (Bhoja Air).
- The cockpit crew incorrect decision to continue the flight for destination and non- adherence to Boeing recommended QRH and FCOM remedial actions / procedures due to non-availability of customized aircraft documents (at Bhoja Air) for Boeing 737-236A (advanced version of Boeing 737-200 series) contributed towards the causation of accident. The inability of CAA Pakistan to ensure automated flight deck variance type training and monitoring requirements primarily due to incorrect information provided by the Bhoja Air Management was also a contributory factor in causation of the accident.
The CAA Pakistan reported the captain (58, ATPL, 10,158 hours total, 2,027 hours on type, 82 hours on -236A subtype) was pilot flying, the first officer (54, CPL, 2,832 hours total, 750 hours on type, 82 hours on subtype -236A) was pilot monitoring. The first officer was due for his recurrent simulator training session, however requested and was granted additional two months to complete that training. His previous simulator training had been done on -200 subtypes without advanced automated cockpits.
During the descent towards Islamabad the crew observed several thunderstorm cells and navigated the aircraft through gaps, the crew therefore discussed possible alternates and briefed for approaches to both runways 12 and 30 of Islamabad.
The aircraft intercepted the localizer to runway 30 at 3600 feet MSL, both autopilots armed for the ILS approach, while turning onto the localizer the crew configured flaps 5, the sounds of light precipitation began and the aircraft entered an active thunderstorm cell. The aircraft subsequently intercepted the glidepath from below, both autopilots activated. However, the aircraft was still at flaps 5 at 175 KIAS, landing gear should have been extended and flaps at 30 degrees according to FCOM at that stage.
39 seconds after the light precipitation began the aircraft's systems began recording an increasing downdraft, the autopilot countered by increasing the pitch angle, the speed reduced. 5 seconds after the downdraft began a sudden change of precipitation to extreme occurred, the aircraft was at 1900 feet AGL at that point, 4 seconds later the aircraft was at 900 feet AGL with the pitch increasing from 6 to 12 degrees nose up. The GPS alert "Windshear! Windshear" sounded. Autothrottle and Autopilot continued, no remedial action was taken by the crew. The CAA annotated, that there were differences between the -200 and -236A types flown by Bhoja, the relevant FCOM and procedures were not available on board of the aircraft.
2 seconds after the GPWS alert the captain shouted "no ... no", the first officer shouted "Go Around! Go Around!", still, no go-around was initiated, neither captain initiated the go-around nor first officer took control of the aircraft. The CAA annotated: "It appeared that Captain and FO were not sure about the behavior of the aircraft in automation mode during wind shear conditions due to their lack of formal training during simulator sessions."
The downdraft reduced, after a maximum of 2400fpm the downdraft reduced to 600fpm resulting in a change of angle of attack and a vertical acceleration peak of +1.4G, while previously a minimum of +0.2G had occurred. The pitch attitude reduced to about 5 degrees nose up, the aircraft drifted left off the localizer until 2 dots were reached.
Both autopilots were disconnected, the autothrust remained engaged in speed mode, the aircraft rolled right 10 degrees. The CAA annotated: "Probably the autopilot channels got disconnected due to the aircraft deviation beyond the autopilot maximum authority limits. Following autopilot disconnect, there was no control wheel activity recorded for approximately 6 seconds and no control column activity for approximately 8 seconds. The cockpit crew was probably in a state of confusion and unsure of remedial actions to be taken to get out of unsafe set of conditions, as the aircraft was still observed flying with auto-throttle in engaged mode."
Another downdraft began.
During the period of lack of control activity at the controls of the Boeing, ATC handed the aircraft off to tower. 4 seconds later the TAWS sounded "Whoop! Whoop! Whoop!", however no reaction occurred from the crew.
The pitch angle decreased from 5 degrees nose up to 0 degrees, the first officer reported on tower and received landing clearance.
The autothrust reduced thrust in order to maintain the target speed.
The second downdraft had increased over 15 seconds reaching a vertical rate of 3000 fpm. Again, there was no response from the crew. TAWS sounded "Whoop! Pull Up! Whoop! Pull Up!", the captain provided nose up inputs, yet altitude and thrust continued to decrease. The downdraft suddenly stopped, the vertical rate reduced from 3000 fpm to close to zero in 4 seconds, the aircraft encountered a vertical acceleration of +1.7G following +0.25G during the downdraft, the stick shaker activated, nose down inputs occurred, the pitch changed from 2 degrees nose up to 12 degrees nose down, the vertical acceleration reduced to +0.45G. The EPR on both engines reduced to 1.0 at 40-45% N1 and remained at that value until impact with the ground. Stick shakers activated again, the first officer called "Stall, let's get out", the captain made control inputs obviously in an attempt to recover out of the critical situation, but neither pilot applied the FCOM/QRH procedures. The TAWS activated "Whoop! Whoop! Pull Up!" until end of recording. The pitch angle increased again reaching 0 degrees at 215 KIAS when the main gear contacted ground first 4.24nm short of the runway threshold slightly to the right of the extended runway centerline, 83 seconds after the light precipiation began. The aircraft disintegrated due to high impact loads.
Examination of the wreckage did not reveal any technical defects prior to impact, the engines were operating, there was no fire prior to impact.
The CAA analysed: "Bhoja Air was asked by investigation team to submit the copy of entire ground schooling curriculum and training schedules of cockpit crew. Bhoja Air Management forwarded only the transition ground schooling as appended in Ops Manual; however, the mishap aircraft was the advanced version of Boeing 737-200 series ie Boeing 737-236A which was equipped with automated flight deck. The ground schooling curriculum of Bhoja Air for cockpit crew did not include the automation of Flight deck. Bhoja Air did not submit the detailed ground schooling programmes as requested by the investigation team. It was observed that Boeing 737-200 which was taught during ground schooling and Boeing 737-236A being inducted in Bhoja Air were completely two different variants of Boeing 737 series. In the case of former variant, it is equipped with semi automated flight deck whereas the latter one with automated flight deck. The information with regards to automation capabilities of aircraft which was to be acquired by Bhoja Air, was not in the knowledge of cockpit crew even after the formal ground schooling which also did not cover the variant training of Boeing 737-236A. It is evident that Bhoja Air cockpit crew ground schooling did not cater for the automation of Boeing 737-236A aircraft."
The CAA analysed: "Cockpit crew at first place never obtained ATIS Islamabad and got the weather update from radar controller BBIAP, Islamabad. The presence of squall line en-route to BBIAP, Islamabad was observed and discussed in detail amongst the cockpit crew. It was also discussed that there was hardly any gap between the active weather cells en-route to BBIAP, Islamabad but still continued their flight to destination and did not take the decision to divert to the alternate aerodrome as it was the evening inaugural flight of Bhoja Air on Karachi – Islamabad sector."
The CAA analysed: "The critical violation of procedures was observed with regard to implementation and conformance of QRH, FCOM and Ops Manual recommended actions / instructions. As per the CAA Pakistan approved Ops Manual of Bhoja Air, the aircraft was supposed to remain clear of an active weather cell by 5 to 10 nm which was not followed by the cockpit crew during the conduct of ill fated flight to destination. The cockpit crew were observed not complying with any Boeing recommended FCOM and QRH remedial actions to recover out of wind shear, TAWS / GPWS warnings and stall conditions."
The CAA analysed: "It was important to find out the reasons of CRM failure which otherwise could have averted the accident. It was observed during the process of investigation that Captain of mishap aircraft was one of the instructional staff when FO was undergoing his initial flying training at PAF Academy as a cadet. Captain always remained a fatherly figure in the mind of the FO. Captain looked after the FO in SAI and later became a factor in his joining Bhoja Air. In Bhoja Air FO flew a total of 23 flights, 16 of which were flown with Captain. FO had an average flying experience and not undergone any simulator training of automated aircraft / flight deck management. That is why, FO kept on reminding the Captain and suggesting a go around to get out of unsafe / hazardous set of conditions after entering the severe weather, but remained reliant on Captain to take the required actions. The FO should have taken over the controls of aircraft to execute a go around once there was inadequate response / inaction by the Captain."
The CAA analysed the weather: "Due to increasing southerly winds with height, the convective cloud would have been vertically sheared towards the north with height. As the aircraft entered the convective system from the south, they would have likely flown under the back sheared anvil cloud while in warm inflow. Then as they continued to enter the convective system, they would have entered the downdraft region. Given the high cloud bases on this day, there was potential for considerable subcloud evaporative cooling resulting in significant cold downdraft production. Therefore deteriorated weather condition was one of the factor in the causation of this accident."
The CAA reported that a weather model by Boeing resulted in a potential of downdrafts of 40-50 knots (4000-5000 fpm).
Incident Facts
Date of incident
Apr 20, 2012
Aircraft Registration
AP-BKC
Aircraft Type
Boeing 737-200
ICAO Type Designator
B732
This article is published under license from Avherald.com. © of text by Avherald.com.
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