Narrative:

Upon the end of the LINNK1 arrival; we were cleared for the ILS 27 into iah. Knowing the LINNK1 has a transition to ILS 27 with mandatory speeds and altitudes; and the LINNK1 says to expect the 27 transition; we briefed the arrival; approach; and the transition between the two before descending below 18;000. Sometime between rdfsh and geygr; the ca (captain) began adjusting the automation. As I was watching altitude and comparing them to the chart; I'm not sure exactly what was pressed; but noticed the ca had ended up in rol mode. While we were still tracking the lateral course just fine; with only a very slight trend to the right; I made a casual statement 'it looks like you're in rol mode'. The ca made a statement similar to 'what...why is it....' and began adjusting the automation. After a few seconds of trying to re-engage LNAV; the ca disconnected the autopilot and began hand flying. At this point we were leveling at 4000 ft for geygr; while correcting our slight (1/2 needle width deflection) course deviation. I make a statement 'ok; geygr at 4000; then syyko at 3000; 210 until festa; then 170 until redoc'. At this point the ca appeared to become flustered; and started verbalizing why she thought there was an error in automation; while simultaneously attempting to re-engage the autopilot as we were leveling at 3000 ft for syyko. While attempting to watch the ca's button presses and trying to follow her train of thought; I took my eyes off of the altimeter for not more than 5-10 seconds. When I look back I see that we are now at 3300 ft between syyko and trann; when we should be at 3000 ft. In a stern voice I say '3000....we are supposed to be at 3000'. The ca replies with 'oh yeah'. Not seeing an immediate change in altitude; I say again in a stern voice '3000; 3000; 3000'. At this point in time; the controller comes on and asks us to change to tower freq; I read back the new freq; but before I change over another controller comes on and says 'descend to 3000; you're supposed to be at 3000 there....contact tower now'. At trann; we reach 3000 ft; I then call tower. While making the radio call; I glance back to the altimeter and see we are now descending below 2800 ft. I say again to the ca '3000....we are supposed to be at 3000'. The ca responds in a seemingly flustered voice 'oh...oh yeah.....but we are between trann and dento now.... So we are ok.' we were in fact between trann and dento; which has a MEA of 2000; so while I did not like that we were now leveling at 2500 ft; I did not push the issue further as we were above MEA with the aircraft holding altitude and localizer; with the ca hand flying; and seemingly flustered. With the aircraft stabilized; I believed any more mention of the issue would only further fluster the flying pilot; resulting in another undesired aircraft state. I twisted in 210 on the speed which was assigned until festa (we were 200); and the ca responded with 'yeah; 210 at festa then 170 to redoc; sorry about that'. No further mention of the event was made; we held 2500 ft until glide slope intercept and continued the approach as normal from just before festa to the runway in a stabilized standard fashion. The undesired aircraft state was an initial +300 ft altitude deviation from a mandatory altitude; followed by a -200 ft deviation below a briefed altitude. There was also a minor lateral deviation that was corrected immediately. The primary threat; was a mishandling of the automation in a critical phase of flight; lack of crew communication regarding what was being done with the automation; which lead to distraction of the pilot monitoring the altitude long enough to allow a 300 ft deviation to be generated before verbalizing the undesired aircraft state so that the pilot flying could correct it. While we utilized good briefing techniques; and FMS programming; however an unannounced manipulation of the automation in a critical phase of flight led to confusion between both pilots asto what the autopilot was doing; and what was done to the autopilot. While I believe it was a good decision to disconnect the autopilot before an undesired aircraft state was generated; further manipulation of the autopilot by the pilot flying while hand flying lead to the pilot monitoring being focused on the further unannounced manipulation of the automation; which ultimately lead to both pilots fixating on the same automation inputs; which led to multiple altitude deviations being generated with the pilot monitoring catching it after the fact. As a pilot monitoring; aside from what I did with providing authoritative altitude announcements to assist the pilot flying; short of inputting corrections into the flight controls myself; I believe I could have been more inquisitive as to what the flying pilot was doing to the automation initially before a deviation occurred; and later on after a deviation was happening advising the pilot hand flying to just 'fly the airplane' while offering to correct the automation myself.

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Original NASA ASRS Text

Title: EMB145 First Officer reported confusion during an arrival when the flying Captain begin making FMC changes that necessitated disconnecting the auto pilot that resulted in deviations above and below the desired altitude.

Narrative: Upon the end of the LINNK1 arrival; we were cleared for the ILS 27 into IAH. Knowing the LINNK1 has a transition to ILS 27 with mandatory speeds and altitudes; and the LINNK1 says to expect the 27 transition; we briefed the arrival; approach; and the transition between the two before descending below 18;000. Sometime between RDFSH and GEYGR; the CA (Captain) began adjusting the automation. As I was watching altitude and comparing them to the chart; I'm not sure exactly what was pressed; but noticed the CA had ended up in ROL mode. While we were still tracking the lateral course just fine; with only a very slight trend to the right; I made a casual statement 'It looks like you're in ROL mode'. The CA made a statement similar to 'what...why is it....' and began adjusting the automation. After a few seconds of trying to re-engage LNAV; the CA disconnected the autopilot and began hand flying. At this point we were leveling at 4000 ft for GEYGR; while correcting our slight (1/2 needle width deflection) course deviation. I make a statement 'ok; GEYGR at 4000; then SYYKO at 3000; 210 until FESTA; then 170 until REDOC'. At this point the CA appeared to become flustered; and started verbalizing why she thought there was an error in automation; while simultaneously attempting to re-engage the autopilot as we were leveling at 3000 ft for SYYKO. While attempting to watch the CA's button presses and trying to follow her train of thought; I took my eyes off of the altimeter for not more than 5-10 seconds. When I look back I see that we are now at 3300 ft between SYYKO and TRANN; when we should be at 3000 ft. In a stern voice I say '3000....we are supposed to be at 3000'. The CA replies with 'oh yeah'. Not seeing an immediate change in altitude; I say again in a stern voice '3000; 3000; 3000'. At this point in time; the controller comes on and asks us to change to tower freq; I read back the new freq; but before I change over another controller comes on and says 'descend to 3000; you're supposed to be at 3000 there....contact tower now'. At TRANN; we reach 3000 ft; I then call tower. While making the radio call; I glance back to the altimeter and see we are now descending below 2800 ft. I say again to the CA '3000....we are supposed to be at 3000'. The CA responds in a seemingly flustered voice 'oh...oh yeah.....but we are between TRANN and DENTO now.... so we are ok.' We were in fact between TRANN and DENTO; which has a MEA of 2000; so while I did not like that we were now leveling at 2500 ft; I did not push the issue further as we were above MEA with the aircraft holding altitude and localizer; with the CA hand flying; and seemingly flustered. With the aircraft stabilized; I believed any more mention of the issue would only further fluster the flying pilot; resulting in another undesired aircraft state. I twisted in 210 on the speed which was assigned until FESTA (we were 200); and the CA responded with 'yeah; 210 at FESTA then 170 to REDOC; sorry about that'. No further mention of the event was made; we held 2500 ft until glide slope intercept and continued the approach as normal from just before FESTA to the runway in a stabilized standard fashion. The undesired aircraft state was an initial +300 ft altitude deviation from a mandatory altitude; followed by a -200 ft deviation below a briefed altitude. There was also a minor lateral deviation that was corrected immediately. The primary threat; was a mishandling of the automation in a critical phase of flight; lack of crew communication regarding what was being done with the automation; which lead to distraction of the pilot monitoring the altitude long enough to allow a 300 ft deviation to be generated before verbalizing the undesired aircraft state so that the pilot flying could correct it. While we utilized good briefing techniques; and FMS programming; however an unannounced manipulation of the automation in a critical phase of flight led to confusion between both pilots asto what the autopilot was doing; and what was done to the autopilot. While I believe it was a good decision to disconnect the autopilot before an undesired aircraft state was generated; further manipulation of the autopilot by the pilot flying while hand flying lead to the pilot monitoring being focused on the further unannounced manipulation of the automation; which ultimately lead to both pilots fixating on the same automation inputs; which led to multiple altitude deviations being generated with the pilot monitoring catching it after the fact. As a pilot monitoring; aside from what I did with providing authoritative altitude announcements to assist the pilot flying; short of inputting corrections into the flight controls myself; I believe I could have been more inquisitive as to what the flying pilot was doing to the automation initially before a deviation occurred; and later on after a deviation was happening advising the pilot hand flying to just 'fly the airplane' while offering to correct the automation myself.

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.