Date: 201409
Local time of day: 1201-1800
Location: DEN.Airport, CO
Flight conditions: VMC
Light: Daylight
Aircraft: Medium Large Transport
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower DEN
Second aircraft: Medium Large Transport
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Distraction; Communication Breakdown; Confusion
Second reporter function: First Officer; Pilot Not Flying
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Became Reoriented
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: On taxi out; my First Officer (FO) was instructed to contact tower on taxiway F. He either misunderstood or received the wrong tower frequency. We held short of 34R at F1. I looked down to the radio display unit once the parking brake was set; and saw that he had selected 133.30; which is the wrong tower frequency for 34R. He inquired; and was given the correct frequency. When he checked on the correct tower frequency; he was told to hold short; as the controller had already cleared someone for takeoff down field. We waited about 30 seconds; and an air carrier entered the runway at F2; paused; and began his takeoff roll. Immediately at this point; she cleared us for takeoff. I could still read the tail number on his aircraft. My FO responded on the radio; 'Are you sure about that?' I believe he thought she had meant to say 'Line up and wait' and was trying to give her a chance to correct herself. She replied that she did indeed say 'Cleared for takeoff'. My FO then responded a bit unprofessionally and I said to him we would just pause until the preceding aircraft was airborne. On initial climb; we were told to contact the tower upon landing.I think that my FO's intention was safety; and trying to clarify the clearance. The aircraft ahead still continued his takeoff roll for approximately 45 seconds. It only takes about 15 seconds for our airplane to begin the takeoff roll from holding short. If at anytime during that span he had rejected; untold lives would have been lost. The tower supervisor assured me that all separation was met; even though to me; it seemed like a terrible idea. We held in position until I was confident that the air carrier was not going to abort. I think we; or the tower; should have made that communication clear that we were going to do that. While we hadn't used standard phraseology; I think that we were just flabbergasted and caught off guard that we would be cleared for takeoff with another aircraft just in front of us.


Second narrative: While taxiing to the runway I was given the incorrect tower frequency from ground. It took less than 45 seconds to realize this and changed to the correct frequency. In the time it took us to realize that we had the wrong frequency; Tower had already cleared an air carrier for takeoff on the intersection next to us. I called the tower and informed them I was on the correct frequency they informed us to hold short runway 34R. The air carrier took the runway; and as they were pushing the power up; the control tower cleared us for takeoff. The captain and I were very concerned about this and I wasn't sure what so say so I said 'Are you sure?' She responded 'Yes; fly heading 360.' The Captain and I were upset that she still was not seeing what we were seeing. At this point the other aircraft was approximately 2000 feet or less down the runway. I then used non standard phraseology by saying 'Call me crazy; but I'm not used to being cleared for take off when an aircraft is still on the runway.' I then responded 'Cleared for takeoff 34R Aircraft X'. We slowly taxied onto the runway waited until the air carrier was approximately 8;000 ft down the runway exchanged controls and I started the take off. Tower informed us to call them when we arrived on the ground. They said that they felt the separations was adequate; we disagreed.I should have used Standard Phraseology and spoke in plain language to convey my concern.


Synopsis: Air carrier flight crew describes being cleared for takeoff as soon as a previous departure was cleared for takeoff. Pilot waited until aircraft was safely airborne then started the takeoff roll.