Air Safety

Factual Information

History of the flight. The [Boeing 747, G-AWNC) aircraft was operating as British Airways Overseas Division (BAOD) scheduled passenger service BA 888 from London to Melbourne via Bahrain, Bangkok and Kuala Lumpur. The flight crew, consisting of the commander, copilot and flight engineer had taken the aircraft over at Bahrain after a 24hr layover from the previous day’s service. (In BAOD terminology the flight engineer is called the engineer officer). The aircraft had departed Bangkok at 1040 (all times are GMT on a 24hr clock) and after an uneventful flight at flight level (FL), 330 made an approach to land on Runway 15 at Kuala Lumpur International Airport, it being flown manually by the commander.

The approach was being made in visual meteorological conditions but the commander had elected to carry out the instrument approach procedure based on the very high frequency, omnidirectional radio range (VOR). Before descent from cruising altitude, the commander had briefed the copilot and flight engineer on the procedure.

The VOR (call sign VBA) is 12. 4nm from the threshold of Runway 15 and is offset about to the north of the extended centreline of the runway. The approach procedure requires the aircraft to cross VBA at or above 2000ft (QNH – sea level altitude) and then to track out on the 158 deg radial descending towards the NM medium frequency locator beacon, which is on the runway centreline approximately 4nm from the threshold. If visual contact with the ground is established at the decision height of 860ft (QNH) over NM then 860ft is maintained in level flight until intercepting the nominal glide path, as defined by VASI or by visual estimation. If not visual at 860ft over NM the aircraft overshoots and proceeds according to its ATC clearance.

Approaching VBA in descent from cruising level both pilots set the Kuala Lumpur QNH of 1012 millibars on their pressure altimeters and also set the indices on the pressure altimeters to the decision height of 860ft in accordance with BAOD procedures. They also set the indices on their radio altimeters to 791ft, this value is derived by subtracting the runway threshold elevation of 69ft from the decision height of 860ft.

With this setting the radio altimeter audio warning should have started approximately 75ft above 791ft and continued with an increasing amplitude down to 791ft which over level terrain, would coincide with 860ft on the pressure altimeters.

As the aircraft crossed VBA at 2000ft tracking out on 158 deg (M) the runway lights were clearly visible to the flight crew, and about this time the commander called for the landing checks. Wing flaps were extended progressively to one, five and finally 10 and when the aircraft had descended to about 1000ft the flight engineer made a warning call of “no flags, 10 flaps set”.

The aircraft levelled off at about this time and almost simultaneously the radio altimeter decision height audio warning began and was apparently much louder and persisted for much longer than the crew had anticipated. During the period that the audio warning was operating the commander stated that he called for landing gear down and 20 flaps. The landing gear lever was selected down but one of the landing gear warning lights became dislodged from its holder.

This caused an interruption to the light engineer’s drill while he verified the door status from the systems panel.

Neither the copilot nor flight engineer heard the call for 20 flap and consequently, it was not selected; the commander was not aware of this but he did not query why the actioning response was not repeated back to him.

Airspeed had been excessive throughout the approach. The failure to extend 20 flaps exacerbated the situation so that as the aircraft approached NM the commander was faced with the necessity of aligning the aircraft with the runway, maintaining height and reducing airspeed.

From this point, about two miles before NM. the crew’s recollection of events is fragmentary and confused. The commander stated that he was flying the aircraft by reference to altitude, speed and rate of descent but he could not recall any power settings. Despite the requirement to hold decision height until intercepting the visual glide path, descent restarted before NM but neither the commander nor the other two flight crewmembers appear to have been aware of the premature loss of height or of a significant rate of descent. Just after passing NM at a speed of about 170kt, the commander called for 25 flaps. This was twice queried by the copilot as “25 from 10?” because of the missing intermediate 20 flap call and also because the airspeed was close to the limiting speed for 25 flaps. There was, however, no response from the commander. During this period of time the flight engineer was completing the landing checklist, the copilot was operating the radio and both were monitoring the 25 flap extension.

The commander recalled that on looking up after an instrument scan the runway lights had disappeared; at about this same time the copilot noticed that his radio altimeter was reading about 150ft and called urgently “100ft above ground level”. As this call was made the commander advanced the thrust levers and rotated the aircraft into a climbing attitude. As the thrust levers were being advanced the commander heard a noise like an engine surge. No 1 engine indications were seen to falter then recover; the aircraft yawed and banked to the left and the commander applied corrective control. Overshoot drill was carried out using less than maximum go-around thrust and, during this period, the flight engineer told the commander that he thought they had struck the ground the commander however was not convinced that they had done so.

Following the overshoot, the aircraft entered the holding pattern over the KL beacon to the south of the airport. Aircraft systems, flying controls and handling characteristics were checked. All indications were normal but as a precautionary measure, the airport fire and rescue services were requested to stand by. The commander then elected to land on Runway 33 and asked for the Standard VASI to be switched on.

He carried out the KL NDB let-down procedure and made an uneventful landing on Runway 33 with the airport emergency services in close attendance. Inspection of the aircraft after landing showed evidence of engine and landing gear damage consistent with the aircraft having hit the tops of trees.

The accident occurred at night at approximately 1220hr at a position latitude 03 deg 10 min N, longitude 101 deg 31 min E at an elevation of approximately 170ft above mean sea level (amsl) and 2. 2nm from the threshold of Runway 15.

Injuries to persons:

None.

Damage to aircraft:

The airframe and engines sustained superficial damage and ingestion contamination.

Other damage:

The aircraft flew through the tops of mature rubber trees on an estate knocking down two trees and felling several large boughs. The area affected was approximately 200 metres long and 30 metres wide.

Wreckage information:

Accident site – The position at which the aircraft had struck the trees was identified from the air by lines of discolouration in the tops of rubber trees on a low hammock about two miles short of the runway and about 400 metres to the right of the runway extended centreline. The ground elevation at this point is about 140ft and the tops of the trees are about 60ft above ground level. The main impact mark was a 200-metre-long swath of defoliated branches heading directly toward the airfield; the width of this swath corresponded to the width of the main landing gear and to the left of this swath were two deep straight “trenches” in the tree tops at a spacing appropriate to the aircraft’s left side engines. To the right of the swath, there was a faint trough at the correct spacing for the number three engine.

On the ground, there were small fragments of flap structure and along the line of the main swath, two complete trees and several large boughs had been felled by the passage of the aircraft. Witness marks on the trees indicated that the aircraft had penetrated the foliage down to a depth of about 15ft from the tree tops. The length of the trail of broken branches was measured at about 200 metres with some traces of freshly broken foliage extending a further 100 metres.

Damage to aircraft:

Examination of the aircraft after the landing on Runway 33 showed that there had been some damage to the hydraulic and electrical systems on all the main landing gear legs. From strike marks on the fuselage, landing gear and engine intakes it was evident that the aircraft had been immersed in foliage to a depth corresponding to the height of the main wing landing gear legs, the left side of the aircraft having penetrated deeper into the foliage than the right. The longitudinal distribution of strike marks indicates that the aircraft had been in a slight nose-up attitude. Numbers one and two engines, although undamaged, were found to be deficient in thrust because of ingestion contamination.

Survival aspects:

The passengers were all seated with their safety belts fastened for landing when the aircraft struck the trees. When power was applied for the overshoot some of the cabin crew heard an unusual noise, felt a bump and a lurch, and sparks were seen coming from No 1 engine. The cabin services officer (CSO) went to the flight deck and reported to the flight engineer that sparks had been seen From No 1 engine.

At this time the flight crew were preoccupied in checking the aircraft’s system and the CSO was informed by the EO to the effect that “there was a serious problem and to make sure everyone was strapped in”. The CSO then advised the cabin staff to be extra vigilant and to ensure that all door areas were cleared of loose articles.

There was no PA announcement but the CSO’s instructions were relayed verbally to each door position and the cabin staff were alerted to the possibility of an emergency evacuation after landing. The CSO reported back to the flight deck that everything was secure for the landing. Passengers were not aware, nor were they made aware, that anything unusual had occurred.

Other information:

BAOD operating procedures – The relevant BAOD Boeing 747 crew manuals contain appropriate instructions for flight crew members.

Items of particular relevance to this accident are as follows: “In respect of crew co-ordination: “Cross-checking, monitoring and call outs.

“Safety demands that the 747 is operated strictly in accordance with recommended procedures and techniques, varied only as dictated by common sense and airmanship, having regard to all the circumstances prevailing. The occupants of the pilot’s and E/O’s seats must operate as an integrated crew, monitoring and cross-checking each other’s actions insofar as is practical . . .

“The navigation and flight progress indications must be cross-checked and monitored continuously; any crew member must advise the captain immediately if:

• “It appears that the aircraft is departing significantly from its intended flight path OR
• “Any abnormal instrument indications, comparator, annunciator flag or light warnings are observed.
• “Any hazardous situation is developing.

“During the takeoff, climb and approach to land phases of flight, the non-handling pilot who will be responsible for monitoring and cross-checking instruments should call out appropriate information; on final approach, it is vitally important that the non-handling pilot continues to monitor the aircraft flight path by references to instruments even after becoming visual, until the threshold has been crossed.

“Flap retraction and extension procedure.

“When making a flap selection the copilot should check the airspeed and keep his hand on the selector until the flaps have stopped at the desired position before reporting the selection complete, eg: “Captain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ‘Flap 20 set. ‘ “Copilot . . . . . . . . . . . . . . . . . . . . . . . . ‘Speed OK, Flap 20. ‘ “E/O checks copilot makes correct selection and monitors.

The copilot keeps their hand on the flap lever and watches indicators to check the flaps operate symmetrically and stop in the correct position.

“Copilot reports . . . . . . . . . . . . . . . . . . . . . . . . ‘Flap 20 set. ‘ “General – Flight handling.

“The sheer mass and inertia of the 747 will naturally tend to make for stability of flight path and speed thus accentuating the necessity tor toward planning and, for example, for early establishment of ‘slot’ conditions during the approach for landing. ”

BAOD Boeing 747 operations and route checking – Most BAOD Boeing 747 operations are into airports equipped with modern approach aids, and involving either automatic approaches or, if manual, then at least approaches in which the aircraft is stabilized in speed and rate of descent at an early stage. Up to the time of the accident, BAOD Boeing 747 route checking was confined mainly to this environment. The airline structure is such that the training of pilots and the routine route checking of pilots is carried out by two different departments. It is not BA policy, once a pilot has successfully completed his training, for its route checking organisation to be alerted to any possible weaknesses exhibited by pilots during their training. This is in line with the provisions of CAP 360.

BAOD use of radio altimeter indices – At the time of this accident BAOD procedures called for the setting of a height related to decision height on the radio altimeter indices regardless of the type of approach or the terrain in the approach area. With a low decision height, a stable rate of descent and a flat area before the threshold, the related audio warning period is necessarily brief and pertinent. However, in a case such as Runway 15 at Kuala Lumpur, with a high decision height, rising terrain before the threshold and a requirement for extended level flight at about decision height the warning period will be prolonged with the aircraft still at a significant height. The noise level is high and produces a considerable degree of distraction, also a serious interference to voice communication between crew members particularly when, as is generally the case with the Boeing 747, noise-excluding headsets for radio and inter-communication are not used on the flight deck.

Commander’s training and subsequent checks – The commander began his conversion training on the Boeing 747 in February 1974; he experienced difficulty in assimilating operational procedures applicable to the aircraft type and also that his airmanship was at times demonstrably weak. Towards the end of the simulator phase of his training his progress gave rise to concern in BAOD training management when he failed his instrument rating renewal. However, when retested after a refresher detail the following day his standard was adjudged satisfactory and he was considered fit to progress to base flying training. He then received 12hr 44min dual instruction and 38 landings on the aircraft itself before progressing to route training, where he flew six North Atlantic sectors under supervision. On the completion of his route supervision, he was issued with an operations certificate as captain on Boeing 747 aircraft for Category 1 weather minima.

On July 30, 1974, three months after qualifying as captain on type, he failed the initial competency check in the flight simulator. In particular, an ADF procedure was incorrectly flown with RMI tracking below standard. This poor showing was attributed to a lack of recent route flying practice (2hr during the preceding calendar month): he was retested the next day and his performance was deemed satisfactory.

On Feb 25, 1975, he underwent a six-monthly competency check in the flight simulator and was required to be retested for renewal of instrument rating; Category 2 renewal check; all requirements for a periodic base check. He satisfactorily completed the check when subsequently retested on Mar 2, 1975.

On May 13, 1975, after completing the appropriate training syllabus and the requisite number of autolands in service he was certificated to operate Category 3 weather minima.

His last two periodic base checks were satisfactorily completed in January and April 1976.

Analysis

The commander’s decision to carry out a practice cloud break procedure followed by a straight-in approach from a decision height of 860ft was in accordance with BAOD policy and was sound in principle since it did not entail delay or hazard to the service. The weather was fine and the runway lights were clearly visible when the descent started from 2000ft. There was no fault in the aircraft’s flight instrumentation or radio navigational equipment to account for the accident nor was there any fault in the ground radio installations or airport runway lighting systems.

Over VBA the airspeed was above that recommended in the BAOD 747 Flying Manual for the distance from touch down (12. 4nm) but not so high as to have prevented a reduction to the recommended value Of 156kt by the time the aircraft reached eight miles from touchdown, provided that appropriate action was taken in good time. Delay in extending the flaps to 10 reduced the rate of airspeed decay and prevented attainment of the recommended approach airspeed during the period of level flight before NM and the subsequent failure to deploy flaps to 20 exacerbated this airspeed problem.

Approaching NM the aircraft began to diverge from the approved procedure. It has not been possible to establish whether this was intentional or unnoticed but, if intentional, certainly no indication of a change in plan was communicated to the copilot or flight engineer nor was there any reason for such a divergence. It is therefore considered more probable that the divergence was unintentional.

It is apparent that the commander was unaware that 20 flaps had not been selected. His expectation that the speed would reduce and the pitch attitude would change following the selection of 20 flaps was therefore not fulfilled. It may be that while he was attempting to resolve this apparent disparity in the aircraft’s behaviour that he relaxed his scan of the instruments, and allowed the aircraft to descend inadvertently.

As he took no action to correct this premature descent it must be presumed that he did not notice it and since neither the copilot nor the flight engineer drew his attention to it, it must also be assumed that they were not aware of it. In particular the copilot appears not to have been continuously monitoring the radio altimeter below 2500ft agl as required by the company’s operating manual. This requirement was introduced following an incident at Nairobi.

After passing NM the commander appears to have become completely absorbed in making a heading change for runway alignment and in trying to reduce his airspeed.

Descent continued apparently unnoticed and unchecked so that eventually, when he fully retarded the thrust levers, turned left towards 152 deg M, and called for 25 flap, the situation was already critical. The aircraft was then at 500ft QNH with a rate of descent of about 900 fpm.

It is evident that from the time of starting the premature descent before reaching NM, the commander did not pay sufficient attention to the attainment of a safe approach path nor did he monitor the descent by reference to his flight instruments. It is also evident that neither the copilot nor the flight engineer monitored the aircraft’s progress properly or if they did they failed to give appropriate warnings when they were necessary. These scanning and monitoring deficiencies must have persisted over a period of more than 50 sec and a failure of this order is indicative of a breakdown in monitoring at a time when the crew were not particularly pressed.

On their own evidence, the crew were not particularly tired and indeed, had they been so the commander is unlikely to have committed this crew to the additional effort the procedure entailed. Although the schedule did involve a change from their established UK work/sleep cycle, this was nothing more than is a normal part of airline activity. It would be illogical to attribute a significant proportion of the accident cause to this factor when a great number of more difficult work/sleep routines occur daily in airline operations without any such deterioration in professional standards. Nonetheless, crew tiredness may, possibly, have been a factor affecting the way in which the approach was conducted.

The prolonged noise level of the radio altimeter warning could have provided a significant distraction in the period of level flight before NM and was possibly a cause of the failure to achieve 20 flap. However, the audio warning had certainly stopped by the time the aircraft passed NM, probably 10 to 15 sec beforehand. There remains therefore some 40 to 45 sec of unmonitored descent leading up to the accident which was not subject to this distracting element and cannot be directly attributed to it.

Taking into account the marginally acceptable performance standards displayed by the commander during and after his Boeing 747 conversion training, it is perhaps not surprising that he found difficulty with and became totally engrossed in the procedure and aircraft handling.

The VOR/ADF procedure for Runway 15 at Kuala Lumpur International Airport evolved before the advent of large jet aircraft and was, as a consequence, not ideally suited to such aircraft as the Boeing 747. However, it is considered that such a procedure should not have presented a competent pilot with any problems.

In instances where individual pilots have experienced difficulties with their conversion training, as was the case with the commander of G-AWNC, it would seem prudent for the airline training department to advise the route-checking organisation, within the same company, of the individual’s problems so that particular attention could be given to the appropriate aspects of line operations.

Both the accident under review and an earlier incident involving another BAOD Boeing 747 at Nairobi revealed inadequacies in BAOD flight deck management and crew coordination procedures. In both cases, the commander became engrossed with his own activities to the detriment of his overall supervision of the progress of the flight and BAOD integrated crew procedures were inadequate as a safeguard.

It is the responsibility of airline management to ensure that adequate procedures are adopted for the safe operation of their aircraft and that the flight crews are trained in their use. While it is relatively, straightforward to write instructions urging flight crewmembers to operate as an integrated crew and to monitor the performance of other crewmembers, it is quite another matter to ensure that the training and education of the flight crews result in safe and effective monitoring being achieved.

The two Boeing 747 investigations discussed both serve to highlight the soundness of the principle that the most effective monitoring is achieved when the person with the most authority, namely the commander, is the monitor.

Conclusions

Findings:

• The aircraft had been properly maintained, and its documentation was in order.
• The crew were appropriately licensed and experienced. They had carried out all the necessary periodic checks.
• There were no defects in the radio navigational aids on the ground or in the aircraft.
• The commander elected to carry out an approved practice instrument let-down procedure to Kuala Lumpur in weather conditions which permitted a visual approach to land.
• The let-down procedure flown by the commander was not well planned and the published profile was not correctly followed. The operator’s recommended handling techniques, recommended speeds and flap configurations for this procedure were not observed.
• A request by the commander for the selection of 20 flaps was not heard by the copilot possibly due to a loud and prolonged audio warning from the radio altimeter; this resulted in an excessive airspeed at a late stage in the landing procedure.
• The use of the radio altimeters related to a high QHN decision height presented the crew with a significant distraction without providing them with useful information.
• The extension of 25 flaps and the reduction of thrust at a late stage in the approach in an attempt to reduce airspeed caused a nose-down pitch which was either unnoticed by or uncompensated by the commander.
• The flight crew failed to notice a dangerous excursion below the safe approach path to the runway.
• Both pilots were concentrating on airspeed to the detriment of other flight instruments. There was a breakdown of overall monitoring of the flight instruments and of the visual flight path during the last 30 sec before overshoot action was taken.
• The published let-down procedure for Runway 15, at the time of the accident, was not compatible with a stabilised final approach from above 1000ft in landing configuration.
• The commander had experienced difficulty in his conversion training on 747 aircraft. His performance during type conversion and subsequent competency checks warranted more critical scrutiny by the operator.
• It is not clear whether the T-bar VASls on Runway 15 were switched on; however the commander did not request that they should be, nor did he request the standard VASI to be illuminated.
• There is a possibility that the tiredness of the crew contributed to the manner in which the approach was conducted.

Cause:

The accident was caused by insufficient monitoring of the aircraft flight path by the crew during the transition from a let-down procedure to the visual phase of a landing approach at night. Inadequate planning and a poor execution of the approach by the commander coupled with an approach procedure which did not allow a stabilised approach, and possible tiredness were contributory factors.

Safety Recommendations

It is recommended that:

• British Airways should re-examine their Boeing 747 flight deck procedures to establish whether a reallocation of crew duties and monitoring responsibilities during the landing approach would permit a greater degree of supervision.
• The VOR/ADF letdown procedures for Runway 15 at Kuala Lumpur should be reviewed with a view to making them more compatible with a stabilised final approach from above 1000ft in the landing configuration.
• Consideration should be given to the provision of ILS equipment for Runway 15 at Kuala Lumpur.
• The procedure for the use of the radio altimeter decision height warning for non-precision approaches should be reviewed.
• Operating crews should be required to take positive steps to preserve the CVR record following an incident or accident and the Air Navigation Order be amended accordingly.

 NEXT ISSUE: The world’s worst air disaster by a strange quirk of fate occurred on the ground. Air Safety for our December edition of AADR reveals the full story behind the tragedy of Tenerife.