B737NG first officer reported a le transit amber light remained illuminated and the number 6 slat wa...

Narrative:

Inbound on the visual approach into ZZZ; as we configured from flaps 5 to landing gear down flaps 15; the le transit amber light remained illuminated. Looking on the overhead panel; we could see the number 6 slat was not in the commanded full extend position. Looking out the window; it visually appeared to be extended properly. We elected to go around and requested vectors to create time necessary to run the checklist. Once we leveled off; the captain called for the appropriate checklist. The captain was pilot flying as I spoke with ATC and began the checklist. At this point; multiple ATC calls created a distraction to us as we attempted to finish the checklist. On step 7 of the checklist; we were to get data for Vref15+15. We both verbally acknowledged this and I proceeded to get the landing data. However; I mistakenly selected flaps 15 data not leading edge inop flaps 15 from the non-normal option on page 2. We put the incorrectly computed data into the FMS and requested vectors again for the visual approach.on approach; as we started to configure; the captain and I both realized that the landing speeds looked incorrect. It was at this point that I realized we hadn't added the 15 knots to vref 15 as required by the checklist. 'Airspeed low' was heard once. We adjusted our airspeed to account for the mistake that was made and landed without incident.there were multiple distractions that occurred during this event that led to me being in the yellow. Trying to run a checklist while answering a dozen ATC calls as well as trying to monitor the aircraft in flight helped to induce error. At the end of all that; I made a mistake. Even though we had briefed ref plus 15; we didn't enter that nor was it caught on the descent check. I know on the [old performance computer] when a different flap setting is called for; a list populates the screen. My familiarity with [the new performance computer] is still growing and I failed to select the non-normal properly which would have prevented this error from happening.

Original NASA ASRS Text

Title: B737NG First Officer reported a LE Transit Amber light remained illuminated and the number 6 slat was not in the commanded full extend position and a go around was initiated.

Narrative: Inbound on the visual approach into ZZZ; as we configured from flaps 5 to landing gear down flaps 15; the LE Transit Amber light remained illuminated. Looking on the overhead panel; we could see the number 6 slat was not in the commanded full extend position. Looking out the window; it visually appeared to be extended properly. We elected to go around and requested vectors to create time necessary to run the checklist. Once we leveled off; the Captain called for the appropriate checklist. The Captain was Pilot Flying as I spoke with ATC and began the checklist. At this point; multiple ATC calls created a distraction to us as we attempted to finish the checklist. On step 7 of the checklist; we were to get data for Vref15+15. We both verbally acknowledged this and I proceeded to get the landing data. However; I mistakenly selected flaps 15 data not leading edge inop flaps 15 from the non-normal option on page 2. We put the incorrectly computed data into the FMS and requested vectors again for the visual approach.On approach; as we started to configure; the Captain and I both realized that the landing speeds looked incorrect. It was at this point that I realized we hadn't added the 15 knots to VREF 15 as required by the checklist. 'Airspeed Low' was heard once. We adjusted our airspeed to account for the mistake that was made and landed without incident.There were multiple distractions that occurred during this event that led to me being in the Yellow. Trying to run a checklist while answering a dozen ATC calls as well as trying to monitor the aircraft in flight helped to induce error. At the end of all that; I made a mistake. Even though we had briefed ref plus 15; we didn't enter that nor was it caught on the descent check. I know on the [old performance computer] when a different flap setting is called for; a list populates the screen. My familiarity with [the new performance computer] is still growing and I failed to select the non-normal properly which would have prevented this error from happening.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1447537
Time
Date	201705
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B737 Next Generation Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	Flap/Slat Indication
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 228
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Deviation - Speed All Types

B737NG first officer reported a le transit amber light remained illuminated and the number 6 slat was not in the commanded full extend position and a go around was initiated.