Narrative:

After pushback and engine start the ground crew requested 'brakes set' and I responded 'brakes set; cleared to disconnect headsets.' shortly after the tug was disconnected we noticed it appeared to be moving forward towards the aircraft. As the tug continued forward the ground crew was hand signaling for 'brakes set' and I hand signaled back 'brakes set' and confirmed the [parking] brake was set. The tug continued and the radome was hit by the tug window which cracked. We contacted dispatch and maintenance control and were towed back to the gate. Maintenance arrived and inspected the aircraft. He noted a 2 inch diameter delamination of radome. When I went down to look at the aircraft; the ground crew advised the plane had rolled into the tug.after further reflection; I realized I had forgotten to turn on the hydraulic system 3 electric pump. Moreover; then realized it was a first flight of the day; so we started engine one first; not engine two. Thus; although the parking brake appeared set; there was no pump supplying pressure and the accumulator may not have held; allowing the aircraft to have possibly rolled forward.possible suggestion is to start engine two on all starts so hydraulic pressure is always available. Also changing procedure for hydraulic pump three selection. Do other operators have a different procedure for hydraulic three pump.

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Original NASA ASRS Text

Title: After pushback and engine start on the aircraft's first flight of the day the CRJ-700 rolled forward and struck the disconnected tug despite the parking brake appearing to be set. The flight crew failed to power the #3 Hydraulic System electric pumps which provide the only source of brake pressure when the #2 engine is not running.

Narrative: After pushback and engine start the ground crew requested 'brakes set' and I responded 'brakes set; cleared to disconnect headsets.' Shortly after the tug was disconnected we noticed it appeared to be moving forward towards the aircraft. As the tug continued forward the ground crew was hand signaling for 'brakes set' and I hand signaled back 'brakes set' and confirmed the [parking] brake was set. The tug continued and the radome was hit by the tug window which cracked. We contacted Dispatch and Maintenance Control and were towed back to the gate. Maintenance arrived and inspected the aircraft. He noted a 2 inch diameter delamination of radome. When I went down to look at the aircraft; the ground crew advised the plane had rolled into the tug.After further reflection; I realized I had forgotten to turn on the HYD System 3 electric pump. Moreover; then realized it was a first flight of the day; so we started engine one first; not engine two. Thus; although the parking brake appeared set; there was no pump supplying pressure and the accumulator may not have held; allowing the aircraft to have possibly rolled forward.Possible suggestion is to start engine two on all starts so hydraulic pressure is always available. Also changing procedure for hydraulic pump three selection. Do other operators have a different procedure for HYD three pump.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.