B737-700
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 271; Flight Crew Type 16000
Confusion; Troubleshooting; Communication Breakdown
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Other / Unknown
General Maintenance Action
Aircraft; Human Factors; Weather
We pulled into ZZZ for an unscheduled plane change. The weather was cold; with 'heavy' horizontally-blowing snow and a layer of ice covering the whole ramp. After we pushed back; the four ramp agents walked away and stuck their hands up over their heads; while facing the other way. With the blowing snow and darkness; it was hard to see if they were showing me a pin or just waving goodbye. As we began the turn to the right; the nosewheel was unusually difficult to move with the tiller; and we decided that was probably due to sliding on the icy ramp. I used appropriate differential power to start the turn; and the nosewheel followed; but not perfectly. I told the FO (First Officer) we would try to complete the turn and see if the nosewheel straightened out and acted normally if I taxied forward. As I rolled out of the turn; the nosewheel was still extremely hard to move; and I decided it wasn't the icy ramp; it was a loss of hydraulic power to the nosewheel. I called Ops to have a Ramp Agent come check the nosewheel for a forgotten bypass pin. Eventually a Ramp Supervisor came out; went under the nosewheel; and came out and gave me a thumbs up. Sure enough; I had nosewheel steering back. We went over for a lengthy deice; and I called Ops on my cell phone and then the Ramp Supervisor who had come out to the airplane to find out what had happened. He explained to me that the handle had frozen in the 'BYPASS' position when the pin was removed due to a large chunk of windblown ice and snow. After he moved the handle back and forth a few times; the hydraulic piston popped out to the 'NORMAL' position. I had never heard of this before. The next day; in the daylight; I went out and asked a Ramp Agent to demonstrate the use of the bypass pin to me. I understand now how this could happen--it is a very subtle movement from bypass to normal. In BYPASS; the handle is vertical; pointing up. A protuberance on the handle pushes the inner piston. This is the BYPASS state. When the bypass pin is removed; the handle should swing to point forward at about a 10 degree angle off of vertical; and the piston should pop out about [distance]'; no more. This is the NORMAL; full hydraulic pressure position. In the dark; with a buildup of snow and ice; this would be very difficult to see--I think a Ramp Agent would have to take off his glove and feel the button; or use a flashlight; to make sure it popped out. I think this (relatively) new bypass pin procedure has some complications that were not considered when this change several years ago was forced down from above. The Ramp Supervisor explained that they had a lot of new Ramp Agents; and they were trying to tell all of them to insure when they removed the pin that the lever moved to the NORMAL position and the button popped out. Please make sure this makes it into the ASAP publication and a Flight Ops memo to let Pilots know about this--no one I have talked to in the last week has ever heard of this. I have been flying here over 20 years now; and have never heard of it. I will ask the pushback crew to verify the handle and button were in the right position from now on when it is cold outside; and especially if there is snow and ice.
B737-700 Captain reported the nosewheel steering bypass handle was frozen in the bypass position after the pin was removed. The ground crew was unaware this problem could occur in freezing weather.