I was on annual leave when this incident happened, but regularly followed the reports and PPrune. I was determined to be extra vigilant...
So on my first day back, (after 35 days off), I'm teamed with a new-hire FO. Good chap, but only 50-odd hours in the seat, 1st post-line indoc pairing. He flew the first leg, whilst I got caught up on brekkie and some housekeeping details.
Leg 2. My takeoff brief was routine (however, omitted reference to permanently displaced threshold on planned departure runway), and we requested the longer runway (circuit traffic was on the shorter one, due to light favourable winds).
Cleared to backtrack to position, we carried out the Before Takeoff C/L. Here's my SNAFU: Passing the displaced threshold (Big numbers, big white lines, arrows pointing to it), I turned to line up there. Force of habit, distraction, aircraft on approach 10 miles back, complacency? Pick one...
Tower advises: "Lucky flight 764, you realize you're not at the end of the runway?"
Shock. There's still 1600 feet to go...(8400 disp thrsh vs 10000 full length).
New F/O guy thought about saying something, then didn't based on suppposing I knew what I was doing.
We turned around. Our thrust setting, flap, and speeds all based on 10000 feet. Not 8400. Obviously very long runway in either case...throw in contaminants, an engine failure, whatever, I would have still been fine. I think. However, with ACARS generated (I mean "optimized") calculations, whatever gravy that was there in the good ole days, isn't there in our modern era. (minimal thrust=minimal engine overhaul cost)
Let the same thing happen with shorter runway...you get the picture...
So I put in a company safety report. Then I beat myself up for a few days, and then realized it could happen to us all, and went back to work the next day, a better, professional pilot.
Fly safe fellow colleagues.
Note: in this example the full 10000 ft is available for t/o, but only 8400 for landing...