Narrative:

The captain was the pilot flying and the first officer was the pilot monitoring. We were doing an ILS in marginal VFR weather. The autopilot was off and I asked for flaps 40 approaching the FAF. I heard a loud bang and the left wing dropped. I immediately used full right ailerons. I then declared to the first officer that we had a spindle failure and commanded a go-around with flaps 15 landing gear up. The first officer responded to my command and informed the tower of our go-around. I climbed from 2000' to 2500'; felt the airplane stabilizing; and then commanded flaps 5 and then flaps 1. Then I called for the spindle failure checklist. We had another company captain and another carrier's captain in the jumpseats. Our company captain suggested that another company captain was riding the fourth jumpseat. The first officer contacted him to do a visual inspection. The captain on the fourth jumpseat called back saying that the left wing looked like there was something hanging from it and that he was 95 percent sure it was a spindle failure. We then declared an emergency and informed ATC of intention to divert. We messaged dispatch via acars. We requested emergency equipment. The other carrier's captain was familiar with diversion airport and got us the ATIS. The other company captain on the cockpit jumpseat ran the performance and checklist. We did an ILS; completed the spindle failure checklist; and landed with autobrake 3. We exited high speed 9000' down the runway and had the emergency equipment do an inspection for hot brakes/smoke. We made a PA. We contacted dispatch and were assigned a gate at another carrier's terminal. We had the emergency equipment follow us to the gate. We ran the QRH for brake cooling which resulted in 92 minutes. We had the aircraft chocked and shutdown the engines at the gate. We made another PA. We called dispatch and did a postflight walkaround. We spoke to maintenance duty control. We also spoke to a company customer service at our original destination airport and informed the passengers. We wrote up the logbook; the first officer did a postflight; and put gear pins in. We shut down the airplane. This was a text book event. Two lessons learned: 1) the checklist was designed well and slow; and 2) slow and deliberate following the procedure saved the day. A competent first officer plus three captains riding on the plane was a plus. We had good communication amongst us and ATC was very accommodating. I was surprised at the initial full right yoke it took to keep the airplane under control; and with each flap retraction it just got better. Flaps 1 required a four-degree correction. I was leery to use the autopilot did not want to add an unknown. The landing speed was 186 plus 5; and flaring at that high speed was not prudent. I landed firmly with autobrake 3 plus full reversers and we were able to stop. I worried about hot brakes and after the inspection by the fire department; we did a slow long taxi to the gate without the use of the brakes.

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Original NASA ASRS Text

Title: A B737-300 flap actuator failed as flaps 40 was selected resulting in a large amount of aileron deflection. An emergency was declared and the flight diverted to a nearby airport with a long runway.

Narrative: The Captain was the pilot flying and the First Officer was the pilot monitoring. We were doing an ILS in marginal VFR weather. The autopilot was OFF and I asked for flaps 40 approaching the FAF. I heard a loud bang and the left wing dropped. I immediately used full right ailerons. I then declared to the First Officer that we had a spindle failure and commanded a go-around with flaps 15 landing gear up. The First Officer responded to my command and informed the Tower of our go-around. I climbed from 2000' to 2500'; felt the airplane stabilizing; and then commanded flaps 5 and then flaps 1. Then I called for the Spindle Failure Checklist. We had another Company Captain and another carrier's Captain in the jumpseats. Our Company Captain suggested that another Company Captain was riding the fourth jumpseat. The First Officer contacted him to do a visual inspection. The Captain on the fourth jumpseat called back saying that the left wing looked like there was something hanging from it and that he was 95 percent sure it was a spindle failure. We then declared an emergency and informed ATC of intention to divert. We messaged Dispatch via ACARs. We requested emergency equipment. The other carrier's Captain was familiar with diversion airport and got us the ATIS. The other Company Captain on the cockpit jumpseat ran the performance and checklist. We did an ILS; completed the Spindle Failure Checklist; and landed with autobrake 3. We exited high speed 9000' down the runway and had the emergency equipment do an inspection for hot brakes/smoke. We made a PA. We contacted Dispatch and were assigned a gate at another carrier's terminal. We had the emergency equipment follow us to the gate. We ran the QRH for brake cooling which resulted in 92 minutes. We had the aircraft chocked and shutdown the engines at the gate. We made another PA. We called Dispatch and did a postflight walkaround. We spoke to Maintenance Duty Control. We also spoke to a Company Customer Service at our original destination airport and informed the Passengers. We wrote up the logbook; the First Officer did a postflight; and put gear pins in. We shut down the airplane. This was a text book event. Two lessons learned: 1) the checklist was designed well and slow; and 2) slow and deliberate following the procedure saved the day. A competent First Officer plus three Captains riding on the plane was a plus. We had good communication amongst us and ATC was very accommodating. I was surprised at the initial full right yoke it took to keep the airplane under control; and with each flap retraction it just got better. Flaps 1 required a four-degree correction. I was leery to use the autopilot did not want to add an unknown. The landing speed was 186 plus 5; and flaring at that high speed was not prudent. I landed firmly with autobrake 3 plus full reversers and we were able to stop. I worried about hot brakes and after the inspection by the fire department; we did a slow long taxi to the gate without the use of the brakes.

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.