Originally Posted by Typhoonpilot

So back on topic for a minute.

It would appear there was a huge human factors trap in this particular incident. At Qatar, as at many foreign airlines, there is no Central Load Planning. The crew perform all performance calculations themselves using the Onboard Performance Tool (OPT). This could be the standard one that comes with the airplane in the Electronic Flight Bag (EFB), or it could be an external laptop.

In the standard Boeing OPT the crew inputs the airport; then the runway; then the intersection, if any. They also enter all the ATIS information for weather; the gross weight; C.G.; choices for flaps (usually set at optimum) and choices for thrust settings.

Sometimes the intersection field is not active, as in there is no intersection to choose from and you only have the ability to calculate full length. Sometimes there are lots of intersections to choose from. If the crew were to choose "ALL" or "FIRST FOUR" the OPT will calculate up to 4 sets of data. The full length data will be displayed on the main screen. The intersection data will be selectable by tabs on the lower right of the screen. Crew could forget to select their actual intersection data, but that would usually be caught in a crosscheck. I do not believe that is what happened.

What I am being told has happened was that the Qatar OPT read "RWY 09 #T1". The "#T1" did not mean intersection T1, it meant temporary runway due to a stopway change and was actually full length data. It would be great if someone at Qatar could provide a screenshot of their OPT to verify this.

So with this OPT readout the crew thought they had T1 performance data and, to take it a step further, they may have very mistakenly thought that was the only option for a takeoff point.

I listened to the Live ATC tape of the departure. The tower cleared the flight to line up at T1 and the crew acknowledged it fully in the readback. When tower told the crew to contact departure their voices were normal. I highly doubt the crew nor ATC were aware of hitting the antenna.

When crew are required to calculate their own performance data and enter it into the FMC the opportunities for error are numerous. There have been numerous weight entry errors over the years, some as high as 100 tonnes, that result in incidents/accidents. The Emirates Melbourne incident is one and a 747 freighter that crashed on takeoff in Canada is another. Air France just had one in a B777F, but that airplane is so overpowered it was just a minor incident.

Another common oversight is not checking the runway data in the OPT. The TORA, TODA, ASD must be checked against the chart to verify that the OPT database is correct. Good example is JFK runway 04L/22R with it's NOTAM for runway shortening. The OPT on most aircraft still had the old, pre-NOTAM, data for calculation purposes. So a manual change to that distance is required in the OPT via a built in NOTAM function to ensure correct calculations are made.

Had the QATAR crew checked the TORA, TODA, ASD in their OPT, even with the deceptive selection, they would have been able to realize something was amiss.

Further information for B777-300 and -300ERs. Later model B777-300ERs do not have a tailskid, only a tail strike detector. The flight control software is good enough to react to a potential tail strike by limiting elevator deflection. In the unlikely event that the tail strike detector hits the pavement it shears off and a TAIL STRIKE EICAS would appear. That message requires landing at the nearest suitable airport. Unknown as this point if this particular B777-300ER had a tail skid or not. Clearly they did not receive a TAIL STRIKE EICAS.

What is less well known is that there have been a number of tail skid contacts in B777-300s that did not result in the TAIL STRIKE EICAS because the tail skid did it's job protecting the aft fuselage. Boeing's guidance in that case, is to continue the flight since it would be near impossible to hit the fuselage without shearing off the tail strike detector. The tail skid effectively prevents that from happening. The same guidance is not given for B777-200/200ERs/200LRs/F since they do not have a tail skid and it is possible to contact the aft fuselage while not hitting the tail strike detector.




Typhoonpilot