B737 air carrier crew reported an unstabilized approach that resulted in a low speed condition on final approach in IMC weather. The crew recognized the undesired aircraft state and performed a go-around; then performed a second approach and normal landing.
Synopsis
B737 air carrier crew reported an unstabilized approach that resulted in a low speed condition on final approach in IMC weather. The crew recognized the undesired aircraft state and performed a go-around; then performed a second approach and normal landing.
Narrative
Established on localizer final for ILS XXL at 3;000 MSL. At glide slope intercept outside VOCUS; we have not been cleared to start approach. I want to query about getting down; but too much radio traffic. When about one dot high on glide slope; ATC directs us to slow from 190 kts to 170 kts and clears us to 2;000 feet and cleared the approach. At this point; I commanded LVL CHG on the Mode Control Panel (MCP). This wasn't increasing the descent rate enough to get down to the glide slope; so I turned off both Autopilot and autothrottle in order to level off slightly so I could fully configure the airplane to Flaps 40; which we had briefed for the wet runway conditions and stopping considerations. We were fully configured and the flight director was complying with ALT ACQ for the 2;000 feet altitude in the MCP window while we were now full deflection above the glide slope. I asked First Officer (FO) to give me a 1000 VS down on the MCP but it wouldn't take. At this time; since I wasn't commanding enough down pitch fully configured at F40 with my throttles back; and somewhat distracted by trying to get flight director help to descend down to glide slope; I noticed I had let my speed decay below Vref of 139. I added a lot of thrust until I saw the speed at Vref and trending faster. At this time; we were 1700 AGL and the FO pointed out we were still full deflection above the glide slope. At that time; I commanded a Go Around. The Go Around and second approach were uneventful.
Second reporter narrative
Flight proceeded normally up to the beginning of the approach; ATC vectored us for approximately a 12 mile final at 3;000 ft and assigned 190 kts. until advised. The Captain (pilot flying (PF)) asked for flaps 10 to aid in slowing. ATC told us to join the LOC only; we both noticed that we would fly through the glide slope if we didn't get an approach clearance immediately. I (pilot monitoring (PM)) attempted to make a radio call to ATC querying them about the approach clearance but could get a word in on the frequency. ATC then cleared us for the ILS XXL maintain 2;000 until established and 170 kts. to the FAF. I immediately set 2;000 in the Mode Control Panel (MCP) altitude window and the Captain asked for gear down and flaps 15. When getting the approach clearance we were already about a dot and a half above the glide slope and the Captain used level change mode to try and get to the glide slope prior to the FAF. The Captain then turned off the Autopilot and auto throttle and asked for the remaining flaps; up to flaps 40. After making the last flap selection I noticed that the flight director (FD) was commanding a level off at 2;000 feet. The Captain asked for vertical speed mode however this would not engage without resetting the altitude window. I verbalized this and returned to looking at the Primary Flight Display (PFD) I noticed we were just beyond the FAF with full scale deviation above the glide slope and airspeed several knots below Vref. The Captain immediately said he was correcting speed. I said that given the speed and glide slope deviation we should go-around. The Captain agreed and the go around was accomplished without incident for a normal landing on XXL.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.