Date: 201312
Local time of day: 1801-2400
Location: FWA.Airport, IN
Flight conditions: Marginal
Light: Night
Aircraft: Boeing Company Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Initial Approach
Airspace: Class C FWA
ATC / advisory: Tower FWA
Aircraft component: Autoflight System
Component problem: Malfunctioning
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: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Aircraft Terrain Warning; Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: A number of factors; weather; experience level; system malfunction; and less-than-ideal decisions lead to a situation where an EGPWS Caution was experienced as a go-around was initiated. ATIS was broadcasting marginal VFR conditions. The planned approach was to the Company preferred runway (quickest access to ramp); RNAV (GPS) Runway 23 with visual conditions expected in vicinity of FAF. I am very familiar with this approach and had flown it as the pilot not flying the night before in better weather conditions in the same aircraft. The aircraft flew it flawlessly as it usually does. On initial contact to Approach Control I advised having the ATIS which was the same as the current METAR: 21012KT 6SM BR OVC016 13/12 A2974. We were not advised that the airport weather was any different; but FWA ATC is notorious (in my experience) for not updating the ATIS in a timely manner around our arrival time in the evening. I later found out it had gone IFR for a period; before returning to VFR.The First Officer was pilot flying and had less than 100 hours in type but impressed me as being very competent. He had been to FWA before (but not with me). During the approach briefing we discussed manipulation of the MCP; and the need for VNAV PATH. Approach clearance was direct SLYDR; cross SLYDR at or above 3;000; cleared straight-in RNAV (GPS) Runway 23. With autoflight on; the First Officer began to slow and configure nicely for a planned approach in visual conditions; though it would have been late for an approach in IMC; which the weather at the field had deteriorated to unbeknownst to us. Over SLYDR; the First Officer performed 'LAVS'; setting up the autoflight system to fly the approach. He called for gear; flaps; and the Before Landing Checklist as he slowed the aircraft to Vapp. As I performed the checklist I lost my pilot not flying SA (Situational Awareness) and; in retrospect; things went downhill pretty fast. I recall breaking out of the clouds above 1;000 AGL and reminding the First Officer that we had until 500 AGL to be stable as we assumed the airport was VFR. For some reason I was unable to see the airport where I expected it to be; [Was] scud obscuring the view? Though I had ground contact as we approached 'Minimums'; something definitely did not seem right. For about one second my brain attempted to make sense of the outside picture; and then I called for a go-around. Almost simultaneously; we received an EGPWS caution 'TOO LOW; TERRAIN' as the go-around was in progress. Later during the debrief; the First Officer said that once the go-around was commanded; he hit the G/A switch but does not think it engaged (due to lack of force from his finger). He then reacted to the GPWS by abruptly pulling back on the yoke to initiate the climb; but with the power back; we briefly entered 'the foot' on the airspeed tape; and he recalls momentarily getting the stick shaker before manually adding full power. As I was not on the controls; I don't have the same recollection he does; but as I was reaching for the flaps (to raise them to 20) I noticed the airspeed out of the corner of my eye and also reached for the throttles. Again; it all happened very quickly; but my recollection is that we immediately began climbing rapidly at a safe speed; the GPWS had silenced; and I continued to configure the aircraft for the go-around. I don't recall hearing a GPWS Warning (i.e. 'PULL UP') which would've dictated the EGPWS escape maneuver (we had visual contact with the ground but it was night); and I'm sure I would not consciously make a decision not to follow the procedure. Knowing the terrain near the airport and observing the airplane's performance; I felt the go-around was an appropriate and satisfactory action at the time. As we leveled at 3;000 ATC asked if we had any issues; and I reported that we did not see the runway at minimums and that the weather seemed lower than reported. They didn't advise us of the latest weather (which had officially returned to VFR) and; for some strange reason; I did not ask. They then asked our intentions; and after briefly discussing the choice of an ILS Runway 32 or another RNAV (GPS) 23; we opted to repeat the approach. In retrospect; clearly the correct decision should have been to select an approach with ground-based navaids; vertical guidance and lower minimums. I'm not sure how much of a factor fatigue or schedule pressure played but; at that point; we assumed any problems with the approach had been 'operator error' and Runway 23 seemed to be the most efficient option. On the subsequent approach; we would be extremely alert for anything not right. We were vectored to intercept the final between SLYDR and the FAF; AKEWS; on about a 7 mile final. Looking back; I have no idea why I accepted this clearance instead of requesting to join outside SLYDR again; but at the time it seemed acceptable. The First Officer was again pilot flying and I was pilot not flying; both of us watching the autoflight system very carefully. Approaching BABAC I noticed the MCP VNAV switch annunciator extinguish and the FLCH switch illuminate. What the heck? The aircraft was now descending below profile; I took the controls; added power; but before I could say 'go-around' we acquired the runway visually; and I opted to continue the approach visually. The landing was uneventful. I made a logbook entry for the VNAV system malfunction and; after consulting with Maintenance Control and Operational Control; we MEL'd the VNAV switch prior to departure. On the next leg; we had a malfunction of the autothrottle system on approach (which was written up upon arrival); and this may have been the root cause of the VNAV malfunction.As usual; a number of factors [contributed to] this event; however; I believe familiarity with the aircraft; airport; and approach; may have led to a level of complacency on my part as pilot not flying. I fault myself primarily for allowing the planning of the RNAV (GPS) approach as a back-up to a visual; instead of planning it as an instrument approach in marginal VFR conditions. Doing so would have required slowing and configuring sooner and; with the Before Landing Checklist complete that much earlier; I could've devoted all my attention to my pilot not flying role. I believe I would've noticed what I now assume was a VNAV malfunction on the first approach. I also believe my First Officer's inexperience in the aircraft and with RNAV approaches may have caused him to become task saturated with slowing and configuring the aircraft during the approach and diverted his attention from monitoring autoflight's performance. I should have given more consideration to his experience level; and encouraged him to fly a conservative approach as opposed to allowing him to fly it as I might have. Contributing to the event was lack of appropriate weather updates from ATC; which surely would have prompted a more conservative approach. And lastly; an aircraft system malfunction and failure to recognize it sooner was the final piece to the puzzle. On the second approach; I think I made several questionable decisions; and while I know that schedule never trumps safety; I have to wonder if it was a significant influence to some of my choices. Finally; I have only briefly mentioned fatigue; but I wonder if that was a factor in my sub par monitoring and decision making that night. This particular trip can be challenging; with the amount of block time (around 6 hours); a relatively short layover; and back-side of the clock flying. The layover was further shortened due to delay to the layover destination. While I felt 'fine' when I reported for duty the night of the event; I have to wonder if my decision making was affected by less than normal rest. I've spent many hours this past weekend reflecting on what happened and thinking how to prevent it from happening again. The most significant lesson learned is; when planning an approach to an airport reporting marginal VFR conditions; treat it as an instrument approach. Allow for earlier configuration and checklist completion so that your attention can be devoted to the pilot not flying role (or if pilot flying; monitoring the autoflight). Breaking out into visual conditions over the FAF should just be a bonus. Other things that would have helped are more obvious such as; if you don't get the information you need (i.e. weather); ask for it! If the first approach is unsuccessful; seriously consider a different one. Never let schedule pressure cause you to make unsafe decisions. And finally; with short layovers; do your best to get adequate rest so you report for duty with a clear head.

Callback: The Captain provided additional information regarding the LAVS procedure and its requirements. When asked about setting the MCP altitude to field elevation plus 100 feet he advised that doing so was now SOP on all approaches at his air carrier. After a discussion of how the reversion to FLCH had gone undetected until the CFTT warnings were received; and the possible mitigating effects of how setting a higher initial altitude might prevent subsequent such events he advised that doing so was procedurally out of the question because it is an SOP mandate that if the FMA ever changed from VNAV--as it would if an intermediate altitude such as the FAF were intercepted--an immediate go-around must be initiated. The intention of that stipulation is that once the LAVS procedure is complete the flight crew is tasked exclusively with monitoring the function of autoflight and intervening only when appropriate in the final stages of the approach should it not be an autoland procedure (with the exception of resetting the MCP altitude to the MAP altitude descending through 1;000 AGL).He paused for a moment after those comments and admitted that in this event; due to completing pilot not flying duties; checklists; etc. the 1;000 foot above callout was never made; the MCP altitude had remained set at FE +100 FT and the jet continued to descend at a much greater than anticipated rate. He then commented that routine scanning of the centered flight director command bars--which remained centered--while cleaning up the pilot not flying tasks reinforced the perception that all was going as intended.He was also unaware of any faults that are known to cause the reversion to FLCH. He did; however; have a discussion with a mechanic who suggested he suspected that an autothrottle fault might do that...although there was no EICAS message of such during the event.Finally; he reinforced his comments relative to the dangers of planning an approach based on anticipated VMC conditions and finding they fail to materialize. He believed his distraction from monitoring the approach in order to complete checklists and other pilot not flying duties compromised his ability to short circuit the errors and resulted in the failure to monitor situationally revealing raw data sources.

Second narrative: We elected to fly the RNAV 23 with the expectation of breaking out around glideslope intercept from AKEWS inbound. We were cleared to descend at or above 3;000 until SLYDR and then cleared for the approach. As we proceeded on the approach we broke out of the weather and I began cross checking the approach and taking a couple of quick looks for the airport environment. Then; prior to our 500 foot; stabilized call and our approach minimums; we both simultaneously realized something was wrong. Upon cross checking of the FMAs [Flight Mode Annunciators] we had somehow switched to FLCH and were no longer descending on the approach. We both looked outside again and tried to visually acquire the airport and quickly came to the conclusion we were too low; too early in the approach. I disconnected the autopilot and autothrottles; pitched the aircraft nose up; wings level and began to add power. Since we had degraded situational awareness; I was beginning the GPWS escape maneuver because I was not sure exactly how much vertical separation we had from the ground and I wanted to get the aircraft climbing as quickly as possible. However; I initially pitched the aircraft too quickly without having sufficient power on the aircraft and we intermittently received stick shaker warnings. We then discussed what we thought had happened. Both of us felt that we had set the aircraft up properly; so we elected to try the approach again; assuming I had made an error somewhere during the approach that we did not catch. We slowed and configured the aircraft early and made sure we would have sufficient time to recognize any anomalies should they arise again. We again began the approach and the aircraft again switched out of VNAV into FLCH.

Second callback: The secondary reporter was uncertain of exactly how far from the airport they were when the alerts were given but believes they were just inside of the FAF; AKEWS. He believes their altitude at the initiation of the go-around was 800 low or about 700 AGL. He stated it was dark but thinks they had ground contact although the airport was not in sight. He had no idea when the switch from VNAV to FLCH occurred and felt it was likely the fact that the Flight Director (FD) command bars remained centered (autoflight was following the active mode; FLCH) probably minimized his scan of raw data. Their ultimate awareness; coincident with the automated warnings; was triggered by the recognition that the throttles were at idle and their rate of descent was about 1;500 FPM down.He discussed the company 'LAVS' SOP; a mnemonic acronym which directs the crew to select the following: 'L' to insure the appropriate Lateral Mode; 'A' to set the appropriate Altitude (more following); 'V' to select VNAV for vertical compliance with procedural restrictions; and; 'S' to select the desired MCP Speed.The LAVS procedure is to be performed at or just prior to intercepting the procedure; in this case at the IAF; SLYDR. LNAV selected for the lateral mode; 100 FT above field elevation would set the lowest altitude to which the jet would fly in VNAV; VNAV the selected Vertical mode to insure VNAV compliance with crossing altitudes; and the appropriate airspeed. Finally; the FMS line selected approach procedure provides a 'computed' glidepath consistent with that charted; which will be conducted by VNAV inside the FAF. The FE+100 FT setting will remain in the MCP altitude window until passing 1;000 AGL on final when the pilot not flying will set the MAP altitude. The descent will now be continued to the DA(H) which will be determined from the barometric or radar altimeter as appropriate.When the above procedure is properly programmed the approach from that point on is FMS/autoflight driven with the exception of the MCP altitude change and the need; for RNAV approaches; to disconnect the autopilot and manually land the jet. He believes what happened is that; for an unknown reason; the change from VNAV mode occurred without immediate flight crew recognition. When FLCH became active the FD command bars and; thus; the jet would reflect compliance with the demands of FLCH mode; i.e. an idle thrust descent at the speed selected on the MCP (about 1;500 FPM down) continuing down to the altitude set in the MCP altitude window...100 FT above field elevation. The FLCH descent rate would be approximately twice that required to fly the computed glidepath; thus; the jet would descend rapidly below the glidepath but the command bars; now reflecting compliance with FLCH mode; would remain essentially centered and look exactly like they would in VNAV. Lacking a timely observation of raw data--altitude; DME or FMS computed distance to the airport; IVSI indications; etc. the descent would be continued at that excessive rate until; as happened in this case; EGPWS or ATC Altitude Alert warning direct recognition of their actual situation.During a discussion of setting the MCP altitude window the reporter ruminated that he would prefer that; instead of initially setting FE+100 FT many miles from the airport it might be better to set the FAF crossing altitude as a backstop in the event of similar failures. He felt that; although doing so could require reselecting VNAV after compliance with the FAF altitude is assured; doing so would both provide an altitude safety net in that any alternative vertical nav mode would never inadvertently descend below the FAF altitude but would also require greater situational awareness on the part of the flight crew with respect to raw data information; defending against over-reliance on FD command bars which; as appears to have been the case in his event; can on rare occasion provide accurate but dangerous indications.

Synopsis: The flight crew of a Boeing RNAV capable; GPS equipped; twin jet cleared for the RNAV (GPS) Runway 23 at FWA were alerted by an EGPWS warning and a low altitude alert from the Tower that they had descended excessively below the RNAV generated glidepath. Simultaneous with the warning the crew was surprised to see that the autoflight system had somehow reverted from VNAV PATH to FLCH. An immediate EGPWS escape maneuver was executed by the pilot flying who applied insufficient pressure to the go-around button to activate go-around guidance and autothrottle response and a short duration stick shaker warning occurred; silenced quickly by manual thrust lever advancement. A subsequent approach under close observation repeated the anomaly with VNAV/FLCH.