One of the first issues not addressed by a rather damning ATSB report into the problems a Qantaslink 717 experienced in 2010 while attempting to land at Kalgoorlie is exactly what Qantas was thinking when it entrusted its brand to Cobham Aviation Services.
This reporter has on various occasions been told that Qantas selects those it entrusts with flying jets covered with its brands on the basis of impeccable high standards equal to those of the parent brand.
Let’s hope Qantas was kidding about that. I think Qantas selected Cobham because it was cheap, or alternatively, it did assess Cobham as being on the same level of excellence as the brand, and thus totally dropped the ball, which resulted in the jet covered in their branding getting into a situation where it might have been dropped into the red dirt of the gold fields.
This is why this ATSB report is of special importance. It shows how a Qantas contractor did things that Qantas passengers don’t expect from a Qantas jet.
The series of stick shaker incidents described in the report occurred to a Cobham flown Qantaslink branded Boeing 717 trying to land at Kalgoorlie on 13 October 2010 carrying 97 passengers, three cabin crew and two pilots.
The first two attempts to land were flown by the co-pilot. The third successful attempt was flown by the captain. The co-pilot told the ATSB he later realised he may have been affected by personal stresses, but the report doesn’t elaborate on this and it is fair to say that given the contents of the report, this doesn’t seem to be material, and it isn’t mentioned in its list of factors in the incidents.
The crew had incorrectly entered a landing weight for the jet in its flight management system computer that was 9,415 kilogram less than its actual landing weight, resulting in the first two approaches, which were abandoned, being flown at too low a speed.
On each occasion the aircraft behaved as if it was experiencing turbulence and the stick shaker briefly activated, warning the pilots that airspeed was falling toward stalling speed.
However, the jet did not enter aerodynamic stall, but the pilots didn’t know what was really going on either.
In its restrained but appropriate prose, this is how the ATSB described the situation which gave passengers a total of three scenic if bumpy views of the approaches to Kalgoorlie.
The flight crew’s pre-landing preparations included the selection of an approach speed (Vapp) based on the flight management system (FMS) generated reference speed (Vref) of 116 kts and an additive to allow for local weather conditions. As the reported weather conditions were relatively benign, the flight crew accepted the FMS default approach speed of 121 kts (Vref+5 kts).
However, unbeknown to the flight crew, the required approach speed based on the aircraft’s weight was actually 135 kts. The effect was that the margin to the actual stall speed of 106 kts in straight and level flight was reduced from 29 kts to 15 kts. Similarly, the margin to stickshaker activation was reduced from 24 kts to just 10 kts. In addition, due to the predictive nature of the stall protection system, the margins were probably further reduced.
The slower-than-required approach speed led to a higher angle of attack and an increase in drag that had an adverse effect on the aircraft’s performance and flight control responsiveness. As a result, the engine power and pitch attitude required to maintain the desired flight profile were higher than usual and significant pitch oscillations were evident. Those pitch oscillations contributed to the difficulty experienced by the flight crew controlling the aircraft’s flightpath and maintaining a stabilised approach.
The flight crew was provided with an indication of the aircrafts proximity to the stickshaker activation speed by the relative positions of the pitch limit indicator (PLI) and the red checker column (Red zipper) on the primary flight display. Although the flight crew noted that the positions of the PLI and Red zipper were closer to stickshaker activation than was normal, they attributed those indications to the g-loading effects induced by turbulence. Those indications were symptomatic of an inappropriate approach speed and consistent with the degraded performance and controllability experienced by the flight crew.
Unfortunately the cockpit voice recorder was overwritten before the ATSB was able to recover the no doubt interesting and insightful conversations between the pilots. (It is quite surprising how often this happens in abnormal aircraft operations.)
This in part is what the ATSB says about the landing weight error, and the procedural failures that ensued.
At the time of the incident, the operator’s procedures did not include a validation check of the landing weight. As such, there was the potential for a pre-departure data entry error to adversely affect the accuracy of the landing data. The absence of an independent method for validating the accuracy of the FMS-generated landing weight, resulted in a lack of assurance that the approach and landing speeds were valid.
Although the operator did not have a validation check of the landing weight, there were procedures in place to ensure that the take-off weight (TOW) was correct. If the TOW was correct, the landing weight based on the same ZFW figures and fuel load was likely to also be correct. In this case, the procedural check of the TOW was not effective in detecting the two data entry errors.
The first data entry error occurred during the transfer of baggage compartment weights from the electronically transmitted load information sheet to the hand-held computer. There was a check prescribed of the load sheet for accurate figures, but the PIC did not detect the error. That data entry error created a deficit of 315 kg in the ZFW, which was not in itself a significant disparity and did not have an influence on the occurrence.
The second data entry error occurred during the transfer of the ZFW from the load sheet print-out to the FMS. Instead of selecting the ZFW figure from the load sheet, the PIC selected the aircraft operating weight (essentially an empty aircraft) and read it out for the copilot to enter into the FMS. The FMS then added the fuel load to the ZFW to generate the TOW. When the copilot called out the FMS TOW for the PIC to validate, the proper response of ‘RTOW checked’ was probably made, but the significant disparity between the TOW calculated by the FMS and the actual TOW on the load sheet was not detected.
As a result of the undetected data entry errors, the FMS-calculated TOW was 9,415 kg less than the aircraft’s actual TOW. Although that disparity had a significant effect on the required take-off speeds, due to aircraft design and the available runway length, the error went unnoticed at Perth and did not manifest as an operational problem until the approach into Kalgoorlie Airport.
The ATSB then turns its attention to how the pilots, which passenger may have assumed were Qantas pilots, handled the stick shaker events.
The flight crew reported that their response to the handling anomalies and first stickshaker were based on their assessment that they encountered turbulence while operating above 1,000 ft. Consequently, the turn and approach were continued. Eventually the approach became unstable and a go-around was completed.
On the second approach, the stickshaker occurred below 1,000 ft and with wings level. The flight crew reported that a missed approach was subsequently initiated because the approach was no longer stable.
However, the stall recovery procedure to be followed during an approach included applying maximum normal thrust, and rolling wings level. Furthermore, a stall recovery must then be followed by a mandatory go-around. Not following the prescribed stall recovery procedure increased the risk of the aircraft becoming aerodynamically stalled.
The flight crew’s training records indicated that they had not received stall recovery training since completing their initial type endorsements in 2008. The operator’s recurrent training programmes were designed to maintain and improve their pilot’s competencies and skills. However, there was no recurrent training that addressed recovery from a stall or stickshaker activation.
Although stickshaker and stall recovery training was completed as part of the flight crews’ initial endorsement, their ongoing competency was not assured.
These references to a lack of recurrent training at Cobham at the time of the incident, are deeply disturbing. At the end of the report (a full reading is urged) the ATSB notes the Cobham is in the process of putting in place responses to its findings. Not has, but is.
To a casual reader, who may have been under the impression that Qantas actually means Qantas, the ATSB report may cause discomfort. It also omits the usual courtesy of saying that the ATSB is satisfied with the safety outcomes.