Medium Large Transport
Flight Crew Air Transport Pilot (ATP)
Time Pressure; Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Returned To Clearance
Human Factors; Procedure
We were taxiing to runway 25R for departure in trail of a B767.  I said to my FO [First Officer] 'Let's make sure we have spacing behind the heavy'.  We started our before takeoff check and the 767 began its takeoff roll; we started our clock.  An aircraft landed and we were clear for takeoff.   We took the runway and I asked for additional 30 seconds to make sure we had at least 6 miles (I tend to be conservative).  The controller informed us we were 8 miles in trail and there was an aircraft 2 miles behind us.  Since 8 miles was more than enough space we departed.  Checking with departure we were told to call tower on landing and given a phone number.  I should have verified the proper spacing before taking the runway thus adding to the controllers stress and potentially creating a hazard.  For some reason I didn't think about the 767 again until we lined up and thought 'Oh; we need spacing' and then asked for more time (I think the Before Takeoff Check hogged my short term memory).  I looked at the clock and we were around two minutes and thirty seconds which was plenty of time; and I think 3 minutes is only required for 757.  The controller advised us of 8 miles separation and I departed because the margin was plenty and there were no exaggerating factors for wake.  I think my instinct for more separation for a departing heavy is a good thing; I just need to ask sooner.  I thought the spacing was not sufficient I would not have departed causing a go around.  Also; lining up on 25R usually has no pressure from final; but 25L closed two days ago and I know the controllers are getting adjusted to blending departures and arrivals from one runway.  I knew there was traffic on final; but did not think it was that close.I called the phone number and spoke to the tower representative and they said there was no record or any notes for Aircraft X.  I asked if I should leave my number and they said 'Nope'.  He advised they are frustrated in the tower dealing with the 25L closure.
Pilot reports of discussion with his First Officer about getting more spacing between them and the previous departure before they take the runway. When they take the runaway they ask for an additional 30 seconds for separation. The controller advises the distance they already have and they depart.