Date: 201502
Local time of day: 1801-2400
Location: HRL.TRACON, TX
Flight conditions: IMC
Weather elements / visibility: 2
Light: Night
Aircraft: B737 Undifferentiated or Other Model
Flight plan: IFR
Flight phase: Initial Approach
Airspace: Class C HRL
ATC / advisory: TRACON HRL
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Pilot Flying; First Officer
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Detector: Person Air Traffic Control
When detected: In-flight
Result: Flight Crew Executed Go Around / Missed Approach; Flight Crew Became Reoriented
Contributing factors: Human Factors; Weather
Primary problem: Human Factors

Narrative: The First Officer was flying the LOC/DME BC Approach [RWY] 35L. Upon intercepting the final approach course; he turned the wrong way from the correct course to capture the LOC. I told him the correct heading to fly and he initially re-intercepted the course and started to descend on the approach. He then seemed to lose situational awareness of where he was on the approach and started to deviate both laterally and vertically from the published procedure. I commanded a go-around which he did initiate. The Tower noted the deviation and I told them that we were 'going around.' We were then vectored back for another approach which was flown successfully and the landing was normal. The weather at the time was reported at 800 broken and six miles; but was in fact at minimums for the LOC/DME BC [RWY] 35L Approach.The problems were as follows: 1. the weather was much lower than reported. I let him continue to fly the approach longer than I should have; thinking we would pick up the runway visually. 2. His unfamiliarity with LOC/BC Approaches. 3. Dispatching [older aircraft] to airports where the only option is a non-precision approach in marginal weather conditions. 4. Had I known the weather was at minimums; I would have flown the approach.


Second narrative: On vector for LOC/DME BC [RWY] 35L in HRL; there was an odd localizer indication during localizer intercept that caused us to pass through the localizer. While trying to get back on the localizer course we realized we had passed the final approach fix and began a higher than normal vertical speed descent. We had planned a 700 fpm descent; but since we were past the final approach fix we increased it to 1000 fpm to make up for the late descent. Because of the increased rate of descent; and 20-knot headwind; we had arrived at our DDA approximately two miles from the field. We had ground contact but could not see the runway; at that time the Tower issued a low altitude warning for our current position. We executed the normal go-around and returned for a normal approach and landing.1. Neither one of us had executed a localizer back course approach in many years. But because we were in an [older] series aircraft; we had no other choice. 2. Both of us were distracted by the localizer corrections being made; and did not pay attention to our distance from the final approach fix. We should have just executed a missed approach before starting our descent; and started the approach out more stabilized. 3. Better planning and familiarization with the approach; or the ability to use LNAV/VNAV in the aircraft would have prevented this from happening.


Synopsis: B737 flight crew reported receiving a low altitude alert from the Tower on a Localizer/Back Course approach to HRL.