Got a question that is mostly directed towards the DJ 737 crew although it does also apply to a few of the QF 737 mob also.
On the few occasions where I taxi out behind a DJ 737 (mostly we're in front
) I've noticed that when the DJ 737 is cleared to line up (and often when cleared for take off also) they mostly go for a 'mini back track'. IE if cleared to line up at 34 Juliet in MEL, rather than taxi out and do a 90 degree right turn to align with the center line, they follow the lead in line
to the south before lining up with a 110 degree (or more) turn to the north to line up. I've seen the same thing in at MEL 27, SYD 16R Foxtrot and even 16R B2!
To ensure that this isn't seen as a DJ bashing exercise I've seen a few of our guys do it as well.
When seeing it I've always thought that if you were that desperate for runway length then surely full length would be a better option. I admit that perhaps I've missed something so I have a number of questions relating to this that tend to flow on from each other.
- Is it simply about not wasting the runway?
- If so, is the 30m saved that critical?
- If the 30m isn't that critical and you're using it simply to increase your margin then in the event of a subsequent incident is a lawyer is going to have a field day and say that if you felt that the extra distance was warranted then why not go to full length?
- I presume you're de-rating in which case why not just reduce the de-rate?
I'm familiar with the old axiom about 'runway behind', etc. We can leave that behind because that's only one aspect of being a professional aviator. Besides, if that were the case then we'd all be taking off from A, B1 or B2 on SYD 16R.
Another reason I ask (apart from idle curiosity) is that there have been a couple of times where this 'mini back track' has taken up enough extra time to ensure that the next aircraft in line (not always me) hasn't gotten away due to the preceding departing taking too long and the next arrival now too close. I've started the clock on a few occasions and from the line up clearance (or take off clearance) to a particular point on the runway on the take off roll (no delay on take off clearance) has taken significantly longer than someone who followed the lead in lines onto the runway and applied thrust along the way- up to 30 seconds. Even taking into account individual pilot nuances, in times of peak congestion this is a significant issue in utilising the runway environment effectively.
Anyone able to shed some light? PM if you like.