MaxSez; This is a continuation of the Saturday Series of Significant Aircraft
Accidents under unusual circumstances. This one is another “Pilot Error” event…
Final Accidant Board Result.
Date: Tuesday 3 November 2015
Type: Boeing 737-4H6
Operator: Shaheen Air
C/n / msn: 27166/2410
First flight: 1992-12-10 (22 years 11 months)
Total airframe hrs: 51585
Engines: 2 CFMI CFM56-3C1
Crew: Fatalities: 0 / Occupants: 7
Passengers: Fatalities: 0 / Occupants: 114
Total: Fatalities: 0 / Occupants: 121
Airplane damage: Substantial
Airplane fate: Written off (damaged beyond repair)
Location: Lahore-Allama Iqbal International Airport (LHE) ( Pakistan)
Phase: Landing (LDG)
Nature: Domestic Scheduled Passenger
Departure airport: Karachi-Jinnah International Airport (KHI/OPKC), Pakistan
Destination airport: Lahore-Allama Iqbal International Airport (LHE/OPLA), Pakistan
A Boeing 737-400, operating Shaheen Air flight 142 from Karachi, sustained substantial damage in a landing accident at Lahore-Allama Iqbal International Airport (LHE), Pakistan.
The flight took off from Karachi at 03:08 UTC. The captain was Pilot Flying (PF) and first officer (FO) was Pilot Monitoring (PM) for the flight.
The en route part of the flight was uneventful. Before initiating descent as per flight plan, the cockpit crew obtained latest weather of destination aerodrome Lahore which mentioned visibility 1200 meters. This visibility was below the minimum required (1600m) for carrying out a VOR/DME approach and necessitated decision for diversion to alternate aerodrome. The cockpit crew decided to continue for the destination.
At 03:59 UTC the flight changed over to Lahore ACC, which cleared the flight the VOR/DME approach to runway 36L. Latest weather was reported a visibility of 1200 meters. Since runway 36R was closed for maintenance, the crew planned to follow the ILS procedure for runway 36R with intention to break off after acquiring visual with the runway and landing on runway 36L. This was a non standard procedure.
The first officer failed to establish radio contact with the first diversion alternate, Sialkot International Airport. At this time, the FO discussed with the captain that in case of diversion their alternate aerodrome was Peshawar which required additional fifty minutes of flying time.
At 04:04 it was discussed if an RNAV approach could be flown and the captain told the FO to request an RNAV approach. However, the aircraft was not equipped with mandatory navigation equipment (GNSS). At this stage, when the FO was cross checking the arrival procedure on the Flight Management Guidance Computer (FMGC) he noted that by mistake the captain had selected runway 18L instead of runway 36L and the FO was advised to change the arrival procedure. The conversation between captain and FO at this time indicates that the captain had difficulty in identifying/reading and feeding the correct arrival procedure due to inability in concentration.
The FO was continuously found to be prompting the captain for decision making. In order to calculate RVR for their VOR/DME approach runway 36L, the FO calculated RVR as 1800 meters by multiplying visibility (1200m) with 1.5. He lacked the knowledge of RVR calculation procedure and did not consider availability of other services at runway 36L, like high intensity approach lighting system (HIALS) or high intensity runway lights (HIRL). The incorrect calculation of the RVR value was not corrected by the Captain as well.
In fact, RVR was the same (1200m) as the reported visibility. The required RVR for carrying out a VOR/DME approach by a Cat C airplane on runway 36L was 1600m.
At 04:12 UTC, the cockpit crew changed frequencies to Lahore Approach as cleared by Lahore ACC. Lahore Approach found the flight being right of track and inquired if they were right of track. The captain quickly asked the FO to tell Lahore Approach that they were following the RNAV procedure for runway 36L. Further descent instructions were given.
At 04:16 UTC Lahore Approach cleared the flight for the RNAV LEMOM ONE CHARLIE arrival runway 36L and, “descend down to 3000 ft on QNH 1018 hecto pascal and report position ELAMA”. The FO acknowledged the approach by correctly reading back. At 04:20 UTC Lahore Approach observed the flight passing through FL85 at 20 track miles which was approx 2000-2500 ft higher than the assigned altitude. At this time, the cockpit crew selected Flaps-1, 2 and 5 in quick succession in order to increase the rate of descent. Speed brakes were not used. Lahore Approach contacted the flight to reconfirm whether they would be able to make approach or discontinue due to being high.
The captain immediately prompted FO to reply by saying “Affirmative”.
At this stage, it is established that the flight was neither following the track (it was right of track) nor the assigned altitudes as per ATC clearance. The FO then suggested the captain to use the speed brake so that the flight could quickly descend to the desired altitude. The captain in response voiced “haye…haye…haye” indicating that he was exhausted and unable to cope with the situation.
At 04:22 UTC the captain asked the FO to lower Flaps-10 and lower the undercarriage. The FO complied with the instructions and confirmed. The captain again voiced “haye…haye…haye”. At this stage, they also lowered Flaps-15, landing lights on and Flaps-30. The captain asked FO to complete landing checklist which was accomplished successfully.
When the flight reported position over ELAMA, the Lahore Approach controller observed the flight to be at 5000 ft altitude instead of already cleared 3000 ft. The duty controller cautioned the flight by telling them that their altitude at ELAMA should have been 3000 ft whereas he had observed it to be 5000 ft. He also advised them to continue at pilot’s own responsibility.
After passing over ELAMA, the flight turned left heading 355° and lowered Flaps-30. The speed at this time was 180 kts and flight was descending through 5000 ft. At 04:23 UTC the captain disengaged the autopilot at 9NM from RWT to lose the excess height by increasing rate of descent and also executed turns to acquire the runway. However, the captain’s decision to disengage autopilot at this stage without being visual with the runway increased his workload. Resultantly, the aircraft descended with very high descent rate from 2000–3500 ft/min. The excessive rate with Flaps-30 selected resulted in exceeding the flap speed limit.
By the time the flight reached 4.6 NM from runway threshold, the altitude was almost correct but they were still not visual with the runway. The cockpit crew was actually carrying out a VOR/DME approach instead of the RNAV approach for which the aircraft was not suitably equipped. The captain kept flying the aircraft with no visual cues due poor visibility, increased stress level, loss of situational awareness and reduced mental ability which led to ending up low on approach with high speed. The approach was unstabilized at that point.
At 04:24 the captain asked the FO whether the runway was visible. The FO replied in negative and advised the captain to engage the autopilot, which could make runway contact easier. However the autopilot was not engaged.
When reported at 4 DME, the controller cleared the flight to land runway 36L. The runway was still not sighted as the airplane was descending through 460 ft AGL. Airspeed at that time was 150 kts, which was 14 knots above the calculated landing speed.
Just before the aural alert “Minimums” sounded, the FO saw the runway towards the right. The FO also took over the controls and asked the captain to inform ATC that the runway was in sight. The aircraft temporarily levelled off at 400 ft AGL for approximately 7 seconds and simultaneously a right turn was initiated. While descending below 400 ft AGL, the vertical speed kept varying between -1100 ft/min to -180 ft/min. At 200 ft AGL, power was advanced to 55%-65% which increased airspeed and temporarily decreased sink rate. Although the FO picked up visual with the runway at Minimum Descend Altitude (MDA) by chance, the aircraft was not stabilized and a go around should have been initiated instead…
At 04:25 the captain also sighted the runway at approximately 150ft and took over the controls from FO. However, the captain was still unable to correctly align the aircraft with the runway, as the aircraft had ended up towards right side of the runway and a left turn was required. The FO was found asking the captain to turn left but the captain advised the FO to ‘relax’.
After descending through 100 ft AGL, the FO made an effort to take over the controls from the captain in order to land the aircraft. The captain was heard uttering “Haye…Ok…Haye…Oh…” indicating total exhaustion and inability to cope up with the situation. The captain was unaware that he was still holding the controls despite handing over to FO. The FO was heard urging the captain to leave the controls. The captain again voiced, “Haye…Oh”. The FO was busy in landing the aircraft while the captain kept uttering exhausting voices besides being hyperventilated.
At 04:26 UTC the aircraft touched down 1400 feet from the threshold, to the left of the centreline. An 8° right bank and 4.5° crab angle caused the right hand main landing gear to touch the runway first. Airspeed was 166 knots, as opposed to the reference speed (Vref) of 134 knots. The speed brakes deployed and the aircraft slightly bounced. The left main gear touched down, followed by the right main gear again. The left main gear then broke after a shimmy. With thrust reversers being deployed, the aircraft ran off the left side of the runway. Upon entering soft soil, the right main gear also broke. The aircraft skidded 8000 feet before coming to rest. An evacuation was carried out.
An investigation revealed that the blood alcohol level of the captain was 83 mg/dl (BAC 0.07%). Many countries use a legal limit for drivers of 0.05%. Moreover, the blood lactate level of 70 mg/dl interprets fatigue due to increased stress as the normal level ranges from 4.5 to 23 gm/dl.
Cause of Occurrence. The accident took place due to:
- Cockpit crew landing the aircraft through unstabilized approach (high ground speed and incorrect flight path).
- Low sink rate of left main landing gear (LMLG) as it touched down and probable presence of (more than the specified limits) play in the linkages of shimmy damper mechanism. This situation led to torsional vibrations / breakage of shimmy damper after touchdown. The resultant torsional excitation experienced by the LMLG due to free pivoting of wheels (along vertical axis) caused collapse of LMLG.
- The RMLG collapsed due to overload as the aircraft moved on unprepared surface.
(Source: AvSafeNet, Photo; Copyright fee paid)