Date: 201306
Local time of day: 0601-1200
Location: LGA.Airport, NY
Flight conditions: VMC
Weather elements / visibility: 8
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ramp LGA
Aircraft component: Nose Gear
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Distraction
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Detector: Person Ground Personnel
Result: Aircraft Aircraft Damaged; Flight Crew Returned To Gate
Contributing factors: Procedure; Human Factors
Primary problem: Human Factors

Narrative: We were cleared to push from the gate to perform an experimental silent push procedure onto Spot XX on Taxiway M. When we were cleared to push from Ramp; I inquired on the Ramp Frequency as to the operational requirements to push based on the memo I had read and what was given to us with the paperwork. I had not operated out of that gate for several months or maybe even a year and wanted clarification on certain details like dates of operation; etc. (There was not a mention of the pulling the plane up to the spot.) After asking the push crew if it was ok to release the brakes; I released the brakes; I commanded the push crew to push back to Spot XX-Y. As we began to push; I monitored both radios for Ground Control to listen to the ground operations. I was trying to ascertain how long it would take for us to get off the ground in order to plan my taxi operations and engine start. As we neared the spot; I loaded the ZFW; Vspeeds; and Flex; while carefully reviewing each page of the Takeoff Data for accuracy. As we got closer to the spot; we received a call from the Flight Attendant stating the 'cabin was secure for takeoff.' As I commonly do; I focused on the speeds and Takeoff Data while I believe the First Officer may have taken the interphone call. At approximately that same time; the aircraft came to what I thought was a complete stop. Also; at the exact same time; as the First Officer spoke to the Flight Attendant on the interphone; or Ground Control; I was distracted when I looked down at my coffee cup and it was spilling on my charts during the pushback. I don't know if it was due to the push crew's technique of not smoothly pushing back; or if the lid had opened and started spilling onto my charts. So then I looked up at the First Officer and muttered something like 'Oh; crap; my charts...' and then the aircraft came to a complete stop. While the both radios were continuing to blast into my headset; and the Flight Attendant may have been talking to the First Officer; I heard a mumble from the push crew. His wording was not very audible and nearly unreadable; but since I had heard it thousands of times before over the years; I heard/assumed that he said to set the brakes. So I did what he commanded me to do; and I set the brakes. I do not recall what exactly he said; but I thought it was to set the brakes which is what I was expecting him to do. At that instance; after pausing the push; he did not mention he was going to continue to pull me forward; and proceeded to pull the aircraft forward. It was at that instance that the sheer pin on the tow bar broke and a loud popping noise was heard and a sudden jolt. I looked down at the tug driver and he said 'oh no.' The First Officer and I looked at each other and I asked 'what just happened?' The Tug driver said 'the tow bar broke.' And we asked what happened down there? Is there any damage?' He said; 'No it looks ok; we just need to get another tow bar.' First Officer and I looked at each other discussed what we should do. We both thought it would be better to just be safe. We asked them to pull us back into the gate and we would call Maintenance in order to be safety conscious as to the possible damage done to the nosewheel and gear. I called Maintenance to describe the event and wrote up the nose gear for possible damage. When Maintenance came out; they immediately said it looked fine; and that we should be ok to continue. After further review; Maintenance Control decided to perform an aircraft swap and perform further inspections. We tried to be safety conscious at all times and erred on the side of caution; though the tug driver said it looked ok. I have never had an incident ever of any damage to an aircraft over the nearly 20 years of flying. There was Organizational/Operational Pressure to get the flights out on time; with full loads. We felt we needed [to] complete the flights before the weather began to move into the area and cancel our later flights (losing revenuefor the company and pay for our crew.) The gate agent also was not comfortable with the boarding of this aircraft. We pushed back on time or even early; and felt the operational pressure to get the flight out and begin taxiing as the delays began to build up due to approaching weather.


Second narrative: Prior to pushback; the ramp gave us instructions for the new experimental 'silent' pushback procedures for the Mike taxiway and it was evident that my Captain was not comfortable with the procedure. He had a memo regarding the procedures dated May [2013] and mistakenly took that to mean the procedures would only be in effect on June [2013] only. At the time; he had not noticed the memo was dated May [2013] and did not give a specific date for the procedures. I had heard a CRJ ask for clarification and I listened to the instructions; therefore I was completely comfortable with ramp clearing us to Spot XX on Mike and then contacting Ground for taxi. However; the Captain was visibly uncomfortable during the push. On the reverse push; I noted that we would need to be pulled forward in order to reach Spot XX. As a result; we were not completely on the taxi line and the Captain made a disgusted comment as he looked down to the left (thinking pushback was complete). To the best of my recollection; right at that time the flight attendants called from the back to inform us that the cabin was secure for takeoff. I was not listening to the ground crew at that time but as I turned to look at the source of the Captains disgust; I watched him pull the parking brake just as the ground crew began to pull us forward. The result was a violent 'lurch;' resulting in the shear pin shearing on the tow bar. Apparently; the Captain had misunderstood the ground crew and thought pushback was complete. We discussed the situation and decided that it would be wise to return to the gate for a nosewheel inspection. Due to Maintenance procedures; the airframe needed to be removed from service to have the landing gear cycled.


Synopsis: During pushback; while utilizing a new procedure; the Captain misunderstood the ground crew and thought the pushback was complete; and set the brakes. When the ground crew attempted to move the aircraft forward to the intended parking spot; the tow bar shear pin broke. The aircraft was returned to the gate for a Maintenance Inspection.