Go-round

The A330, VH-QPJ, was arriving after midnight at the end of a scheduled service from Singapore. The Perth Terminal Aerodrome Forecast, available to the crew before their departure, predicted broken cloud at 1000ft, visibility of more than 10km and a 30 per cent probability of fog after 2am. As the aircraft’s ETA at Perth was 1220am, it departed Singapore without carrying fuel for a diversion to an alternate. Even so, the crew, concerned about the forecast, did load some additional fuel.

At 9. 30pm WST, when the Airbus was midway between Singapore and Perth, the Bureau of Meteorology assessed that the onset of fog would be closer to midnight than 2. 00am and issued a Trend Type Forecast for fog from 12. 30am. The Perth TAF was also amended to forecast fog from midnight. The crew received the Trend Forecast via ACARS (the Aircraft Communications and Automatic Reporting system), and an hour later requested the amended Perth TAF.

By 11. 30pm fog was over the city, moving slowly eastwards towards the airport, and Met Bureau staff telephoned the Qantas despatch centre in Sydney to inform them of this.

The crew recalculated their Designated Point All Engines Operating (The position furthest removed from the departure airport to which an aircraft may fly and then divert to a suitable airport with all engines operating while meeting the inflight fuel requirements).

Based on a possible diversion to Learmonth, this coincided with the aircraft’s planned descent point for Perth. Nearing this point at 11. 38pm, the crew requested the actual weather at Perth, RAAF Pearce, and Learmonth. The Perth forecast still predicted

Despite not being approved for instrument approaches to lower minima than Category I, Perth Airport’s Runway 21 ILS enabled the aircraft to make a successful landing in fog.

fog from 12. 30am, while there was scattered cloud at 400ft at Pearce. Learmonth had no significant weather.

At 11. 52pm ATC informed the aircraft that the Perth ATIS was now reporting 10km visibility, reducing to 8km in mist, so with an ETA of shortly before 12. 20am, the crew began their descent. Having done so they were committed to land at Perth as VH-QPJ’s remaining fuel was now insufficient to divert to Learmonth, 600nm (1110km) north of Perth, and the only available other airport suitable for Airbus A330s.

The rate at which visibility then deteriorated at Perth while the Airbus was on descent is evident from these airport observations: 12. 03am – visibility 5000m in mist.

12. 08am – visibility 3000m in mist.

12. 12am – visibility 2000m in fog.

12. 16am – visibility 800m in fog.

12. 26am – visibility 400m in fog.

12. 30am – visibility 300m in fog.

Arriving over Perth at 12. 10am, the crew began an ILS approach to Runway 21, the main instrument runway. But at the 250ft minima, visibility was less than the required 800m, and they began a missed approach.

Because the crew of a departing aircraft reported visibility was better on the southern end of the runway, ATC then radar vectored VH-QPJ for a Runway 03 ILS approach. But again at the minima, visibility was less than required and the crew again carried out a missed approach.

The aircraft was equipped with autoland capability for Category II and III airports overseas, and with no other possibilities left to them, the crew decided they had no alternative but to carry out another ILS approach, and if necessary, to continue with an autoland to below the approved minima. (An autoland approach, landing and roll-out is controlled by the aircraft’s autopilot).

Transmitting a Mayday call to ATC because of their emergency situation, the crew announced their intention to conduct their next approach to Runway 21 to below the minima if necessary, using the A330’s autoland capability.

ATC was required to implement “low visibility operations” when the Runway Visual Range was 800m or less. This was to ensure all aircraft and vehicles on the manoeuvring area were stationary before the Tower issued a clearance to land, and that other arriving traffic had a minimum of five minutes spacing. This traffic management during low visibility conditions is to avoid affecting ILS signals. But because vehicular traffic on the perimeter road in the undershoot area of Runway 21 remained uncontrolled, the crew were informed that the “critical area is not protected”.

The crew flew the approach using low visibility procedures with autoland selected.

At 250ft, the captain had about 400m visibility (half the minimum for the normal ILS approach) with some of the approach lighting visible, and at 100ft above the runway, he could see the runway threshold lights. The landing was uneventful and the crew found they had sufficient visibility to taxi to the terminal.

The lowest instrument approach landing minima available in Australia are those offered by the Category I ILS, providing a decision height of 200ft above the threshold, with a minimum visibility of 800m. All Australian ILS facilities at airports are approved to this category only. Category II and III facilities used at some overseas airports permit lower decision heights and less visibility, but require ground based equipment capable of operating to more exact tolerances, with more extensive runway lighting and marking.

Qantas A330 aircraft are CASA approved for Category II and III operations at these airports. Defined as low visibility operations, these require specific crew procedures and use of the aircraft’s autoland capability.

On a previous occasion, the crew of an Airbus A330 approaching Sydney at the end of a flight from Perth on 6 April 2004 were forced to conduct an autoland below the Category I landing minima, after unforecast fog developed during the latter stage of the flight, resulting in a deterioration of visibility at the airport.

At the time of the Perth incident, Qantas’s fuel policy did not discriminate between

At the time of the Perth incident, Qantas’s fuel policy did not discriminate between Perth, well isolated from airports suitable for the A330, and other Australian airports.

Perth, well isolated from airports suitable for the A330, and other Australian airports. Flights to Perth therefore did not normally carry additional fuel for a diversion to a suitable alternate.

ATSB commented in its report that Qantas was conscious of the risk this posed, seeking to manage it through its integrated operations centre. And the crew’s conservative decision to carry fuel in addition to the minimum requirement demonstrated their own awareness of the risk. Even so, this was insufficient fuel to assure a landing at a suitable alternate airport.

ATSB believes the crew’s action in attempting two approaches before committing themselves to a landing below the minima was sound. Their selection of the Runway 21 ILS and use of the A330’s autoland capability reduced the risk inherent in landing in conditions below the specified minima.

Nevertheless, there were risks – the lack of assurance of consistency in the ILS signals and of the monitoring provided by Cat II and III facilities.

Landings in weather below specified approach minima are not acceptable in normal circumstances, and ATSB believes accurate fog forecasting is an essential risk control. Another is airline fuel policy. Where fuel for diversion to a suitable alternate is not routinely carried, it is important to have contingencies to manage the risk posed by unforecast weather.

Qantas subsequently implemented an interim flight planning fuel policy for Perth, requiring that all flights into Perth in the evening be planned with an alternate if there was any indication of fog, irrespective of how late the fog was forecast (eg if the ETA was 2pm and the TAF showed a 30 per cent probability of fog from 8pm, an alternate would be planned). The policy would remain in place until the Bureau of Meteorology reconsidered their forecast timings for fog, ahead of completing a longer term analysis into the onset and cessation of fog.

One press report on the Perth incident claimed that “Qantas captains were under constant pressure to carry not a litre more in fuel than company operating procedures deem appropriate for each flight. ” And that “This tight fuel policy impinges on the traditional authority of captains to rely on their experience and judgement in calculating fuel appropriate to the variable conditions under which a flight operates”.

But both Qantas and some individual airline captains strenuously denied this was so. One captain said: “The policy might require you to load the ‘minimum operational requirement’, but there is no restriction, implied or expressed, on taking whatever fuel you require for the sector. I certainly have no hesitation in adding extra fuel if I think I’m going to need it, and I’ve never had a phone call asking why. ” Another commented: “At times I take extra fuel and have never been questioned by the company, nor have I heard of anyone else being questioned. ” The chief pilot of Qantas, Captain Chris Manning, rejected any suggestion that the company pressured pilots not to take on extra fuel. “Forecasting fog is relatively difficult and comments that we pressure pilots not to take extra fuel are absolutely wrong, absolutely false,” he said. “We don’t take a note of that ever. That’s the pilot in command’s responsibility. ” Some airline pilots believe there should be higher ILS standards at Perth, because it is so remote from suitable alternates. And Sydney also. “I do think for cost versus risk, Sydney and Perth should have CAT III,” one pilot said.

“Seems to be a few diversions each year in both places. One day it may well go ‘pear shaped’ on someone. ” Another commented pertinently: “Perth is the most remote capital in the world – you would think in those circumstances it would have a CAT III ILS. ”