Narrative:

We leveled off at 3000 ft south of the airport heading east on a downwind for runway xxl. This was unusual because we did not do the ILS to yyc circle to land xxl and instead were vectored for a downwind and base to xxl from the west to the east. Upon level off I heard one of the motors surging and looked down at the engine instruments to find the #1 motor surging about +- 5%. At this time my first officer who was the pilot flying had used the speed brakes on descent but had failed to stow them. I turned off the #1 power management control (pmc) and the surging stopped for the #1 motor. I then turned the pmc back on and the surging began again. I again turned off the pmc. I then went to the checklist and looked at the pmc inoperative checklist. Sometime during this; flaps 5 was selected. After running this checklist; I elected to turn both pmcs off and continue with the approach. At this point we were approaching base and landing gear down; flaps 15 was selected. At this point I noticed a slight rumbling or airframe vibration to the aircraft. On base now; flaps 30 was selected and the airframe rumble became more apparent. I asked the first officer if he felt this and he responded that he did. I then placed my hands on the yoke and asked my first officer if one could feel the rumble through the yoke. Once I place my hands on the yoke my first officer gave me the aircraft. After a positive change of aircraft control I selected flaps 40 and we accomplished the before landing checklist. All cockpit indications were normal except for the rumble that was occurring. After confirming our configuration to include the aft overhead flap indicator gauge and confirming the flap gauge circuit breaker was in; I elected to continue the approach and land. I told my first officer that the aircraft was handling and flying normal and that the engines were responding to my throttle inputs accordingly. Not knowing what the vibration was and given the fact that we had just had an engine malfunction weighed heavy on my decision to land and not go around.landing was unusually smooth for the airport and after touchdown I told my first officer that I did not want him to change the aircraft configuration because of the rumble. Upon clearing the runway it hit me when I placed my hand on the speedbrake handle to manually stow the speedbrakes that I never remembered arming the speedbrakes. Upon this revelation I told my first officer that we had just landed flaps 40 with full speedbrakes and that is why the aircraft was rumbling. I directed a flaps up clean up and we taxied to the gate. After looking back at this event and reflecting on how things transpired there were a lot of factors that contributed to the mis-configuration on final approach. 1. My first officer having been here only 2 years did not concentrate on fully flying the aircraft by letting the engine problem distract him and watching me accomplish the checklist. 2. The checklist I used really just gave me guidance and there really is no checklist for this problem. It is more just common knowledge to turn off the pmc if the motor is behaving in this manner. 3. Being vectored for an approach to a known runway differently than what we were expecting. 4. The fact that we have an aircraft difference between the B737 models aircraft. This was huge because if we had been in a B737-ng this would have never happened. We would have gotten the 'speedbrakes extended' light. Because of the rumbling and the previous engine problem I was not going to release the controls and that is probably why I did not do a check of the speedbrake being armed. I had both my hands on the controls after I took aircraft control and given the rumble and engine problem we had was not going to release the controls to touch anything else. We accomplished the before landing checklist 3 times; once with the card and twice verbally between us. Having said and saw 'armed green light' and saw a green light for the speedbrake; I assumed it was armed. I am normally not in the habit of grabbing the speedbrake while saying 'armed green light' during the before landing checklist anyway and the fom gives us no guidance for grabbing or looking at the speedbrake handle for this checklist. It would be nice to have a 'speedbrakes extended' light in the classic fleet but that probably will not happen. I am going to develop a habit of placing my hand on the speedbrake from now on during the before landing checklist to make sure they are not extended.

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Original NASA ASRS Text

Title: A B737 crew on final approach was distracted by an engine RPM fluctuation and failed to recognized the airframe's rumble was caused by extended speedbrakes that remained up the entire approach and landing.

Narrative: We leveled off at 3000 FT south of the airport heading east on a downwind for Runway XXL. This was unusual because we did not do the ILS to YYC circle to land XXL and instead were vectored for a downwind and base to XXL from the west to the east. Upon level off I heard one of the motors surging and looked down at the engine instruments to find the #1 motor surging about +- 5%. At this time my First Officer who was the Pilot Flying had used the speed brakes on descent but had failed to stow them. I turned off the #1 power management control (PMC) and the surging stopped for the #1 motor. I then turned the PMC back on and the surging began again. I again turned off the PMC. I then went to the checklist and looked at the PMC Inoperative checklist. Sometime during this; Flaps 5 was selected. After running this checklist; I elected to turn both PMCs off and continue with the approach. At this point we were approaching base and landing gear down; Flaps 15 was selected. At this point I noticed a slight rumbling or airframe vibration to the aircraft. On base now; Flaps 30 was selected and the airframe rumble became more apparent. I asked the First Officer if he felt this and he responded that he did. I then placed my hands on the yoke and asked my First Officer if one could feel the rumble through the yoke. Once I place my hands on the yoke my First Officer gave me the aircraft. After a positive change of aircraft control I selected Flaps 40 and we accomplished the Before Landing checklist. All cockpit indications were normal except for the rumble that was occurring. After confirming our configuration to include the aft overhead flap indicator gauge and confirming the flap gauge circuit breaker was in; I elected to continue the approach and land. I told my First Officer that the aircraft was handling and flying normal and that the engines were responding to my throttle inputs accordingly. Not knowing what the vibration was and given the fact that we had just had an engine malfunction weighed heavy on my decision to land and not go around.Landing was unusually smooth for the airport and after touchdown I told my First Officer that I did not want him to change the aircraft configuration because of the rumble. Upon clearing the runway it hit me when I placed my hand on the speedbrake handle to manually stow the speedbrakes that I never remembered arming the speedbrakes. Upon this revelation I told my First Officer that we had just landed Flaps 40 with full speedbrakes and that is why the aircraft was rumbling. I directed a flaps up clean up and we taxied to the gate. After looking back at this event and reflecting on how things transpired there were a lot of factors that contributed to the mis-configuration on final approach. 1. My First Officer having been here only 2 years did not concentrate on fully flying the aircraft by letting the engine problem distract him and watching me accomplish the checklist. 2. The checklist I used really just gave me guidance and there really is no checklist for this problem. It is more just common knowledge to turn off the PMC if the motor is behaving in this manner. 3. Being vectored for an approach to a known runway differently than what we were expecting. 4. The fact that we have an aircraft difference between the B737 models aircraft. This was huge because if we had been in a B737-NG this would have never happened. We would have gotten the 'speedbrakes extended' light. Because of the rumbling and the previous engine problem I was not going to release the controls and that is probably why I did not do a check of the speedbrake being armed. I had both my hands on the controls after I took aircraft control and given the rumble and engine problem we had was not going to release the controls to touch anything else. We accomplished the before landing checklist 3 times; once with the card and twice verbally between us. Having said and saw 'armed green light' and saw a green light for the speedbrake; I assumed it was armed. I am normally not in the habit of grabbing the speedbrake while saying 'armed green light' during the before landing checklist anyway and the FOM gives us no guidance for grabbing or looking at the speedbrake handle for this checklist. It would be nice to have a 'speedbrakes extended' light in the classic fleet but that probably will not happen. I am going to develop a habit of placing my hand on the speedbrake from now on during the before landing checklist to make sure they are not extended.

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.