Date: 201502
Local time of day: 0601-1200
Location: DSM.Airport, IA
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 900 (CRJ900)
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Taxi
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Commercial
Human factors: Situational Awareness
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Became Reoriented
Contributing factors: Airport; Human Factors
Primary problem: Human Factors

Narrative: This was the first leg of the third and last day of the trip. Our original schedule was to overnight in DSM and do DSM-ZZZ-CLT-ZZZ to finish the trip. The ZZZ flight ended up being cancelled so we sat in the airport for a few hours while our next move was sorted out. We ended up being assigned to take the same aircraft and operate it with passengers to ZZZ1. We loaded up and prepared to pushback. The day before it snowed over a foot in DSM. The aircraft needed type I treatment for frost; and the ramp area was 100% covered in compact snow and ice. DSM de-ice procedures is to do a partial push back; apply fluids engines running; then complete the push. We pushed back halfway out of the gate; started engines; and completed the pre de-ice checklist. We were treated with type I; and the push crew (who was also the de-ice crew) returned to finish the push. When they started to push again; the tug appeared to be spinning out on the ice. The de-ice truck then came over and sprayed a little fluid around the tires of the tug; but the tug still wouldn't move. After about a minute of trying to get the tug loose we heard a loud pop and queried the tug driver what it was; and he said that the '____ pin' (I can't remember what it's called. It's a pin that's designed to break under pressure to preserve the nose gear. I will refer to it as the 'tow bar pin' hereafter). The tow bar pin had broken; so we needed a new tow bar. We decided to disconnect and go get a new tow bar. At this point the captain said 'brake is set'; and motioned to set the brake; and we saw that the brake had been on the whole time. We informed the crew and contacted Maintenance (MX); who came out to inspect the nose gear. It was then realized that the broken tow bar was stuck to the nose gear and they hassled with it for some time before it was finally disconnected. It turns out that it was frozen to the nose gear. Once the broken tow bar was disconnected; MX inspected the nose gear and said that there was nothing wrong with it at all. We connected a new tow bar; finished the push; and completed the flight normally; although we felt rather silly and embarrassed. Although it was our mistake; there were factors that made this mistake much more likely. The pre-ice check includes 'parking brake set'; but the post-ice check makes no mention of the parking brake. This makes sense; since most fluid applications are done while not under tow. However on one of the rare occasions application is done during partial pushback; then it is something you have to remember on your own. The other factor was the icy ramp. Since the ramp was extremely slippery and completely covered in ice; it made perfect sense that the tug would get stuck. Had it been cleared; it would have been extremely obvious to check the parking brake. But with all the ice; that didn't even go through our heads and it wasn't until the captain attempted to set the brake did we see that it was already set. The captain actually said out loud 'brake is released' to the ground crew several times; but the brake was never noticed. Adding a note to the checklist; or adding parking brake would help with avoiding a recurrence. As would extra care in actually checking things; not just saying them. (For both pilots).




Synopsis: CRJ-900 First Officer reported pushing back on an icy ramp with the brake set; resulting in damage to the tow bar pin.