As a companion piece for Discussion Topic 24-2: Learning to Manage Distractions More Skillfully, I offer NASA ASRS report #2051046. In this event, a malfunctioning radio altimeter generated spurious low altitude warnings in a CRJ200 during an ILS approach. Distraction, confusion, and unskillful flightpath management resulted in an unstabilized approach, change of aircraft control, and landing from an approach instead of going around.
First Officer’s report (flying a Pilot Flying-PF until the Captain takes over, then as Pilot Monitoring-PM): On departure from ZZZ CA (Captain) noticed that the RA [radio altimeter] was showing 0 ft [sensor input indicating that the aircraft was on the ground]. We were on a cruise altitude of 12,000 ft, as soon as we started to descend, the gear horn started to warn that the gear was not down. Disregarded that warning because it was due to the RA. We were cleared for the approach for visual XXL, backed up by ILS. FO (First Officer) turned into green needles 18 miles from ZZZ1 [Airport] and armed APPR mode. Soon the FMA showed the green ‘GS’ mode captured. Soon Captain and FO noticed that the autopilot was not descending for us. Canceled AP (Autopilot) and GS was already 1.5 dots going down [above glidepath]. The airspeed was 180kts with flaps 20, FO called gear down. After the gear, FO tried to put flaps 30 and therefore almost leveled off for the airspeed to reach below 180 (we were nose down to follow the GS so airspeed didn't slow down much). During this attempt, GPWS false alarm started, yelling at us “Terrain, Terrain, Pull Up”, “Too Low, Terrain”, “Glide Slope” and “Sink rate”. Captain called out disregard, it was clear that there was no terrain, but FO got distracted with the aural and started to lose cross-check. The warnings have continued all the way down to the landing, therefore distracting us from normal sequence and ATC calls. After the flaps 30 configuration was established, FO started to follow down the GS, but the lateral side was off the centerline. At some point we had PAPI showing 3~4 red lights [a below glideslope indication], and Captain called out “You’re Low”. Passing ZZZZZ, at 6,800 ft FO called Flaps 45, Before Landing Checklist. FO called “One Thousand” at 6,100 ft. At this time, we were already in an unstable condition but continued. Soon after FO got even more unstable again showing 4 Red lights, Captain called “my controls”. After the Captain took control we were established again with 2 white 2 red. Around 300 AFE the aural warning said something other than usual, “Too low, Flaps”. FO noticed that the flaps were at 30 configuration, and called “Flaps 45?”. It was unstable but FO did not call “Go around”, CA put flaps 45 and landed.
Lack of hand-flying skills. Distraction management. [Lack of] confidence to call go around. Maybe muting the aural warnings might have helped, but also on the other hand, aural did let us know that we were in flaps 30. I think it would’ve been better if I was trained as: If “Too Low, Flaps” is heard, the next callout is “Go around”. Just like an automatic call out like “Go around thrust flaps 8” being automatic if I hear “Missed Approach”. The first thing I heard “Too Low, Flaps”, my instinct thought was “Okay, we’re low and flaps 30... so put flaps 45?”
Briefing potential warnings during approach: The crew knew after takeoff that they had a malfunctioning radio altimeter (indicating zero). Perhaps they didn’t know that this malfunction might generate spurious aural warnings during the approach. The report does not say whether they discussed these possible approach warnings or how they intended to handle them. When the spurious warnings began to happen, the report implied that the Captain immediately knew that the warnings were false since they instructed the FO to disregard them. It further implied that the FO became significantly distracted and affected their ability to fly the approach. Perhaps if the Captain had briefed this while in cruise flight, the FO might have been less vulnerable to distraction.
Getting behind on the approach parameters: The first warning they received was a landing gear warning horn as they descended out of 12,000’. The next distraction was the failure of the autopilot to capture the glideslope and descend. As the flightpath reached 1.5 dots high on glideslope, the FO disconnected the autopilot and started down. This went poorly. The FO admitted their lack of hand-flying skills. The flightpath became steep and fast. The FO called for landing gear down (to increase drag and reduce airspeed). The combination of their steep descent and high airspeed prevented them from extending the flaps to 30. They leveled until they could decelerate below flap placard speed and extend more flaps. After extending flaps to 30, the FO again increased descent rate to rejoin the glideslope. At this point, the approach appeared to be salvageable.
Escalation of warning notifications: Around 2,000’ above runway elevation, the FO was falling behind the approach profile and struggling to shed airspeed to get landing flaps extended. Addition warnings began to sound – “Terrain, Terrain, Pull Up”, “Too Low, Terrain”, “Glide Slope” and “Sink rate”. The situation became even more distracting. The FO appeared to become so tunnel focused while trying to rejoin the glideslope that they began to “lose crosscheck” resulting in a lateral deviation. Correcting for the lateral deviation, they lost glideslope alignment and flew too low. The Captain made the callout, “You’re Low”. While we don’t know this airline’s procedures, industry conventions generally require scripted callouts for approach deviations. The Captain’s callout, while accurate, probably didn’t adhere to procedures. This transition from informative callouts to procedurally-scripted callouts is an interesting topic that we can address in a later discussion (also covered in detail in my book).
Captain also becomes task saturated and tunnel focused: The FO called for flaps 45. At this point, the Captain (as PM) should have verified placard speed compliance, announced “Flaps 45”, placed the flap lever to the appropriate position, and monitored the flap gauge for desired extension. The Captain didn’t perform any of these tasks, probably because they became tunnel focused on the unstabilized flightpath as they were approaching 1000’. Understandably, the Captain probably directed their attention to the deteriorating approach parameters and on deciding whether to assume aircraft control. Somewhere below 1000’, the Captain had seen enough and assumed aircraft control.
Procedural breakdown and unstabilized approach landing: Soon after the Captain assumed aircraft control, the crew experienced an, “…aural warning [that] said something other than the usual, ‘Too low, Flaps’”. Looking down, the FO (now serving as PM) noticed that the flaps weren’t extended to the planned 45 position. They queried the Captain, “Flaps 45?”. The FO acknowledges that they did not direct a go around. At this point, the Captain apparently reached over, set their own flaps to 45, and landed. This is considered nonstandard in most crew aircraft. First of all, they should have called for or executed a go around. Second, assuming that they were committed to land, the Captain should have called for flaps 45 to allow the FO to verify parameters, set the flaps, and confirm their extension. Third, while not stated, it is strongly indicated that they failed to complete their Before Landing Checklist.
FO’s analysis: The FO finishes their report with a brief analysis of what went wrong – “Lack of hand-flying skills. Distraction management. [Lack of] confidence to call go around.” They then suggested that “Maybe muting the aural warnings might have helped”. I am not sure of the systems of the CRJ200, but generally, many EGPWS (Enhanced Ground Proximity Warning System) warnings are not “mutable” until the out-of-tolerance conditions are corrected. The FO goes on to suggest that if their training was more specific, they would have felt more confident to call for a go around. While probably valid, this misses the larger point that their unstabilized approach parameters should have triggered a “Go Around” callout even without the EWGPS warnings.
Lack of Captain’s report: An interesting sidenote is that this record did not include a Captain’s report. Typically, this is because the report was either not submitted or because it lacked useful information. From my experience, it was probably the former. Often, pilots who choose to deviate from procedures often choose not to highlight their noncompliance by submitting written reports. We have every indication that this Captain failed to brief for expected spurious warnings, make required deviation callouts, direct a go around when the FO’s approach became unstabilized, direct the FO to set flaps to 45, call for the Before Landing Checklist, or go around from their unstabilized approach. It would also be informative to know whether the Captain documented the radio altimeter malfunction in the logbook.
Summary: This event reflects many of the distraction-related concepts detailed in my book, Master Airline Pilot. We see how a series of escalating distractions disrupted flying, led to flightpath deviations, and inhibited the FO’s ability to restore the intended flightpath. Moreover, we see how both pilots became consumed by task saturation, plan continuation bias, and event quickening. These led them to tunnel their attention focus while trying to “save” an unstabilized approach. Granted, they landed safely. Unfortunately, landing safely has an effect of minimizing past errors. Hopefully, this crew engaged in a detailed debriefing to analyze their errors and to recommit themselves to maintaining higher standards in the future. From Discussion Topic 24-2, we have the distraction parameters of:
- Intensity or severity: How much of our attention was diverted by the distraction?
- Duration: How long did the distraction last?
- Operational flow disruption: How different is our current position from where we were before the distraction?
The intensity of the distractions increasingly diverted their attention. More importantly, the severity of the distractions steadily increased. This seemed to undermine their ability to recover. The distractions demanded increasing levels of attention focus to restore their flightpath and aircraft configuration. Once the chain of distractions started, they continued. Apparently, the crew never reached a point where their distractions ceased. Finally, their operational flow remained disrupted all the way down final. When the FO failed to restore stabilized parameters, the Captain assumed aircraft control. This, in effect, became another distraction as both pilots needed to switch roles, reestablish new flight perspectives, and assume new tasks to complete. This is why most airlines encourage their pilots to go around rather than try to salvage unstabilized approaches.
I welcome your comments on this discussion.
