Large Transport; Low Wing; 2 Turbojet Eng
Maintenance Airframe; Maintenance Powerplant
Communication Breakdown; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control
Procedure; Human Factors
[This] morning I and another Mechanic were asked to take an Aircraft from the ramp to the gate at the terminal. I rode brakes and [Maintenance] towed with the super tug (Douglas) it must have been very busy this morning because when we got lined up with the gate it took the wing watchers and guide man at least 1/2 hour to guide us in. Anyway we were guided in. I received a call over the radio to set brakes from the [maintenance]; which I did; I waited a short time to get plugged in for external power during this time I turned off hydraulics and the anti-collision lights. I then left the cockpit to door 2L to open it for the gate agent; when I noticed the plane was rolling. I ran back to the cockpit to get back on the brakes; as I was getting back to the cockpit I heard so body yelling for brakes or chalks I couldn't tell. Maintenance then contacted me thru cell phone to reset brakes which I was already doing. He then re-positioned the tug back under the aircraft to recapture it. During this time I turned hydraulics back on along with the anti-collision lights and verified that there was brake pressure. Maintenance then asked to release brakes again to reposition the aircraft back on the line. We were marshaled back to the line; Maintenance asked me to reset the brakes again which I did. I then turned off the hydraulics and anti-collision lights; I stayed in the seat till the available external power light came on; and turned off the APU. I then exited the 2L door. There were no injuries to personnel or to the aircraft and there were no delays to this Flight!
After towing an aircraft to the terminal; with the tow tractor disconnected; the Mechanic riding brakes left the cockpit seat before ground power was available to pressurize the hydraulic system so he could set the brakes.