Apologies for the lack of posts – I’m on holiday, However, I’ve been given what seems to be a plausible version of events in the Emirates A340-500 tailscrape at Melbourne, which tallies with earlier rumours. To the best of my knowledge there’s still no official statement on all this so I’ll caution that this below is strictly unconfirmed.What I’m told is that the first officer entered a digit 2 instead of a3 when entering the take-off weight in the laptop that the crew uses -resulting in a selection of a weight 100t less than the actual.
Following a 14 hour deadhead flight to Dubai some time later, the captain was taken to his office and soon resigned.
Thedevil’s in the detail of course, but the fact is that there have nowbeen numerous examples of data misentry – some resulting innear-disaster, many going unreported – particularly on less-criticalnarrowbody operations.
Here’s an early one that I happen to be particularly familiar with:
SAS probes procedures after close call on take-off
Kieran Daly, London (03Sep99, 12:16 GMT, 759 words)
SASis reviewing its cockpit procedures after a Boeing 767 came close tocatastrophe on take-off when the crew used the wrong aircraft weightfor its performance calculations.
The captain of the Tokyo-bound 767-300ER aborted take-off at Copenhagen after rotation when he realised something was wrong and managed to stop inside the length of the airport’s 3,570m (11,713ft) runway 22R from a speed of around 140kt (260km/hr).
The aircraftsuffered a minor tailstrike and burst tyres and it has since beenestablished that the crew had entered the aircraft’s zero fuel weight(ZFW) instead of its gross weight – about a 65t difference.
SAS, whichrecently changed its procedure for calculating take-off speeds -switching from using a hand-held computer in the cockpit to the use ofthe ACARS (aircraft communications addressing and reporting system)datalink to have the final calculation performed elsewhere – is nowtrying to see if there is a way to reduce the chance of a repetition.
A senior Captain involved in the review tells ATI:”This happened to a very experienced professional colleague of mine. Myfirst thought was that if this can happen to a solid fellow like thisthen it can happen to anyone. So we have to look into it and see whatwe can do.”
Another SASofficial – director of flight operations in Denmark, Fleming Jeppsson -relates how in the 24 August incident the co-pilot was conducting thetake-off and rotated the aircraft at the calculated speed (VR).
Jeppsson says: “The take-off data computation was based on far too low a take-off weight. So that gave a very, very low V1, V2, and VRand when the rotation was performed it did not give the desiredresults. The aircraft over-rotated and there was a tailscrape althoughit turned out to be not bad enough to warrant changing the skid.
“The captainrealised that something was wrong and told the co-pilot to lower thenose. All the indications told him to carry on, which is what they aretold to do, but he realised something was wrong and he aborted thetake-off.”
Remarkably theaircraft suffered only a scraped tailskid and three of four tyres burston the left main landing gear, requiring the tyres and brakes to bereplaced. Jeppsson says some passengers did not immediately evenrealise anything was amiss.
The SAS captain explains that since implementing ACARS some six months ago, SAS‘procedure on the 767 fleet is for one pilot to enter the data for thecalculations into the flight management system datapage and for bothpilots to verify the inputs and the results.
The data enteredcomprises the aircraft’s actual gross weight as passed to the crew, thewind, temperature, altimeter setting and runway condition. That is transmitted via ACARS to SASoperations’ department and, within about 20s, the calculated flapsetting, full thrust, derated thrust if possible, and speeds aretransmitted back and printed out in the cockpit.
Before the introduction of ACARS, the SAS767 fleet was using hand-held “take-off calculators” in the cockpit tocalculate the same data – a major advance on the paper charts used byairlines for decades.
The SAScaptain says: “The charts gave us very exact but very conservativefigures so the calculator was a great step forward and ACARS is evenbetter. I don’t think I would want to revert to the old system.”
Because the oldchart system required the use of very conservative assumptions itactually constrained the loads that aircraft could carry at marginalairports, meaning the switch to computed solutions had a direct effecton operating efficiency.
Both SASofficials confirm that, although the Swedish investigation authoritiesare examining what happened, there is no question that it was the crewthat made the error and not the operations staff.
Jeppsson says:”As soon as we identify the weak area then my idea would be toimmediately correct it. But we don’t want to change a procedure oranything like that until we know exactly what we want to do.
“We have sent amessage to pilots to say that obviously this is a grey area to put itmildly. It seems like something very basic but clearly it can happen.”
What is certain is that SASwould be extremely reluctant to reduce the use of ACARS itself – it hasbeen a hugely enthusiastic user of the system and datalink programmemanager, Bjorn Syren, publicly identified its role in take-offcalculations as “a big success” at an ARINC symposium in May.
Source: Air Transport Intelligence news