Narrative:

We were departing. I was the non-flying pilot while we departed runway 32. I noticed a very slight yaw at about 120 KTS but it was not noticed by the flying pilot and I thought he had just done a rudder correction or compensated to maintain center line. The take-off continued and gear retraction and all indications were normal. Well into the climb after 10;000 ft the flight attendant called and said that there were multiple passengers telling her that it sounded like we ran something over on take-off and there was also a very loud bang right before rotation. We then discussed the situation between the flight crew and decided to use some team building by bringing maintenance and dispatch into the decision. We then agreed that the safest thing to do was return to our departure airport. We did declare an emergency and had the equipment standing by as a precaution in case there was gear or tire damage. I explained to the passengers that we were returning as a precaution and they would see the emergency equipment on arrival. The landing was uneventful and I informed them to remain seated and we would be stopped for a few moments on the taxiway while the ground personnel checked the gear and tires for obvious damage. They reported no damage visible and we taxied to the gate. After we got to the gate and I talked to maintenance I went to the back and talked to the passengers as they got off the airplane. They did not seem upset as they went into the terminal. Passengers reported that they thought we ran something over and they heard a loud bang. We did not hear the bang from the cockpit. These passengers ride on our airplanes all the time. I took seriously the information they were telling me. This was a mechanical failure that we had no control over. After we identified that we may have a problem I started talking to maintenance control and dispatch to make a decision to return. This was a malfunction in the #3 brake assembly that caused the tire to lock up as the weight came off the tire on rotation.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B737-400 brake locked up on takeoff causing a noise loud enough to concern passengers. The aircraft was returned to the departure airport for maintenance.

Narrative: We were departing. I was the non-flying pilot while we departed Runway 32. I noticed a very slight yaw at about 120 KTS but it was not noticed by the flying pilot and I thought he had just done a rudder correction or compensated to maintain center line. The take-off continued and gear retraction and all indications were normal. Well into the climb after 10;000 FT the Flight Attendant called and said that there were multiple passengers telling her that it sounded like we ran something over on take-off and there was also a very loud bang right before rotation. We then discussed the situation between the flight crew and decided to use some team building by bringing Maintenance and Dispatch into the decision. We then agreed that the safest thing to do was return to our departure airport. We did declare an emergency and had the equipment standing by as a precaution in case there was gear or tire damage. I explained to the passengers that we were returning as a precaution and they would see the emergency equipment on arrival. The landing was uneventful and I informed them to remain seated and we would be stopped for a few moments on the taxiway while the ground personnel checked the gear and tires for obvious damage. They reported no damage visible and we taxied to the gate. After we got to the gate and I talked to Maintenance I went to the back and talked to the passengers as they got off the airplane. They did not seem upset as they went into the terminal. Passengers reported that they thought we ran something over and they heard a loud bang. We did not hear the bang from the cockpit. These passengers ride on our airplanes all the time. I took seriously the information they were telling me. This was a mechanical failure that we had no control over. After we identified that we may have a problem I started talking to Maintenance Control and Dispatch to make a decision to return. This was a malfunction in the #3 brake assembly that caused the tire to lock up as the weight came off the tire on rotation.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.