Air carrier flight crew reported brake system overheated and observers reported smoke coming from the main gear while taxiing on to the runway.
Synopsis
Air carrier flight crew reported brake system overheated and observers reported smoke coming from the main gear while taxiing on to the runway.
Narrative
We received clearance to line up and wait runway XXC. As we started to move; the FO and I felt the aircraft shake. I thought we may have a problem with our brakes or a flat tire. I received a call from my #4 FA stating that she felt like we ran over something. I thanked her and told her we would not be taking off. I told the FO to advise ATC we will need to vacate the runway due to a mechanical issue. ATC cleared us to taxi via runway XXC; Taxiway 1; Taxiway 2; Taxiway 3. At that time; the aircraft behind us; a company 737; reported smoke coming from our left main landing gear. ATC gave us [priority handling] and we requested ARFF (Airport Rescue and Firefighting). I continued to taxi at a very slow speed onto Taxiway 1 but stopped short of Taxiway 2 making sure I was clear of the RSA (Runway Safety Area). I started the APU and shut down both engines for ARFF to inspect the aircraft. There was no smoke visible from other aircraft or the control tower after we stopped.I considered the event to be stable at that point and I tasked my FO with contacting MX (Maintenance) via radio and OPS to let them know of a gate return. I did an all-call with all 4 FAs and advised them that we had a mechanical issue with our brakes and safety vehicles would be inspecting the aircraft. I then made a PA and let the passengers know we had a mechanical issue with our brakes and safety vehicles would be inspecting the aircraft and to please remain seated with your seat belts fastened.ARFF arrived at the aircraft and I began to communicate with them. I advised them both engines were shut down and told them I suspected a problem with our brakes; possibly a dragging or locked brake on the left side. They advised brake temps were 150; 300; 150; 150. We cancelled the [priority handling] but requested at least one ARFF truck to remain present.ZZZ MX told us to call maintenance control. I called my dispatcher and told him of the situation and asked for a patch with maintenance control. Maintenance control advised we will need a tow from the taxiway to the gate and to call ZZZ MX using the radio. ZZZ MX sent a mechanic with a super tug to the aircraft. We were advised that they did not have a headset to communicate directly with us. We decided to use the MX frequency to communicate directly. The mechanic chocked and inspected the landing gear. He asked us to release the parking brake and see if the aircraft would roll back into the chock. It did and he said it looked good and wanted to hook up the super tug and try to pull us about 20 feet. I advised the FAs and PAX (Passengers) of our plan.Shortly after we started to move; I felt the aircraft start to shake again and told them 'stop; stop; stop' on the MX radio frequency. 'Smoke' started coming from the #2 wheel again which was seen by ARFF; MX; and OPS on the ground. We came to a stop and the smoke dissipated. A plan was made to deplane using stairs and buses on the taxiway. I called my dispatcher again and updated him; also advising that [priority handling] was declared by ATC for smoke from our landing gear. I received a phone call from my Chief Pilot. I updated him on the situation and how the crew and passengers were doing. He let me know that leadership will meet us and the passengers and to call him if we needed anything. I made a PA to the passengers updating them on our plan; that we would need to deplane using stairs and be bussed back to the terminal. I turned off the seatbelt sign; let them know that they could use the lavatory but please remain seated unless you need to get up. I also told them the use of PEDs (Personal Electronic Device) was now allowed.The buses and airstairs showed up and pulled up to the aircraft. I made a PA advising the FAs to disarm doors. The L1 door was opened and we were greeted by leadership and I was briefed on the plan for the passengers and crew. I made a PA to the passengers telling them that the buses were here and we would be deplaning shortly. I let them know we had a new aircraft and that once they get into the terminal to proceed to gate XX and that our aircraft will be there in about 20 minutes.After the passengers were off the aircraft; I met with the FAs and my FO and conducted a debriefing of the incident. The entire crew operated as a perfect team and in a very professional manner. The biggest takeaways from the debriefing were that effective; honest; and thorough communication from the flight deck was vital in keeping the flight attendants informed and the passengers calm and teamwork led to a successful and effective outcome.After the passengers were off the airplane I did a cabin inspection with ARFF and verified that no passengers were onboard. I made a logbook entry and collected my belongings. I did the first half of the securing checklist but left the APU/batteries on. I turned off the bleed at the request of the mechanic so he could start working on the wheel. I made a final cabin check before getting off the airplane and turning it over to MX.I inspected the aircraft before leaving. The mechanic showed me the damage to the wheel. A tie bolt broke and went into the brake assembly. The cloud of 'smoke' was actually carbon dust from the brakes as they were being destroyed by the bolt. I thanked OPS and ARFF for their assistance; got into the bus and returned to the terminal. I met with my Chief Pilot and called the ATCT.I want to give credit to all parties involved in the incident. Everyone performed their roles in the incident with extraordinary professionalism. The aircraft behind us speaking up was vital in determining the severity of our problem leading us to [request priority handling]. ATC gave [priority handling] and dispatched ARFF as well as working with us to safely clear our disabled aircraft from the active runway. ARFF secured the scene and performed a safety inspection of the aircraft. They remained present through the deplaning process. Airport OPS acted as the liaison between the parties involved and was instrumental in developing and executing the ever evolving plan to recover the aircraft and transport my passengers; crew; and airline leadership to and from the incident site. MX was able to determine the severity of our problem and develop a plan to recover the disabled aircraft. My chief pilot office for keeping tabs on us; making sure I had everything I needed to ensure a successful outcome; and providing behind the scenes support for the operation. And finally but certainly not least; my crew was an invaluable team that performed their roles flawlessly and without hesitation. Without them; I would have been overloaded with work and my passengers would not have been calm and willing to deplane as if it were normal and routine.Cause: Mechanical failure
Second reporter narrative
Captain and I began in ZZZ. Day one consisted of three legs with Flight ABCD being the third leg intended from ZZZ to ZZZ1. All pre-checks; walk around; flows; and checklists were normal and completed in accordance with company SOP's and policy. The flight originated from gate XX and was approved for push and taxi to runway XXC. The aircraft handled normally throughout the taxi along Taxiway 1. As we turned left onto Taxiway 2; I felt something as if our left main ran over something or a brake locked. Simultaneously; we were given a clearance to lineup and wait on runway XXC. The Captain and I both concurred that there was something wrong with the plane and I requested a straight ahead taxi through the runway to the other side on Taxiway 2. Tower ATC instructed us to make a left hand turn onto the runway; right turn onto Taxiway 3; right onto Taxiway 4; and right onto Taxiway 2. As we were following towers instruction; the aircraft behind us on Taxiway 1 stated over the tower frequency that they had seen smoke come in from our left main as we were approaching the hold short stop bar. Additionally; one of the flight attendants called to the flight deck stating that she felt like we ran over something with our left main. We made the turn onto the runway with no incident; however; upon turning right onto Taxiway 3 we felt the same indication from the left main. We decided to stop straight ahead on Taxiway 3 facing away from the runway.Captain instructed me to inform tower that we would not be moving any further and that we needed ARFF (Airport Rescue and Firefighting) disbursed to our location. He set the parking brake; shut down the engines; and we went through the shut down flows and checklist. Captain informed the flight attendants and passengers of what was happening and ensured that we would keep them apprised of any information and plans moving forward. He also communicated with company maintenance; operations; and maintenance control to discuss the plan for the disabled aircraft. Once ARFF arrived; we cleared them in to inspect the aircraft and it was determined that our left inboard break was at 300°; significantly higher than the other three. No other indications were mentioned by ARFF. Initially; maintenance determined that a tug would be dispersed to our location to tow us back to a gate to deplane the passengers. Maintenance arrived with the tug and captured the plane following their inspection. They informed us that they would move the aircraft approximately five feet to determine if the plane would be able to be towed to a gate. After that test; the plane was determined safe to tow. Once it began the right turn onto Taxiway 4; however; we again felt the dragging of the left main and informed the tug driver to stop. Later; it was relayed to us that black smoke was seen from the left main during that right hand turn prior to us stopping. Maintenance personnel on scene evaluated the left brake area and determined that the aircraft would not be able to be towed and that buses and air stairs would be needed to deplane on the taxi way. It was relayed to us that a lug nut on the tire had sheared and worked its way into the brake pad causing axle grinding and locking. Buses and air stairs arrived approximately 20 minutes later when all passengers and crew were transported back to the terminal.This was a material failure and limited mitigation by air crew could be assessed.
More incidents for this aircraft family →
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.