Air carrier pilots who fly GA aircraft for personal or recreational purposes often report to ASRS that partially automated GA aircraft require a more disciplined instrument scan. One such pilot, accustomed to the built-in “protections” of the air carrier Flight Management System (FMS), experienced an altitude deviation while monitoring the VNAV page of the GPS.

• On IFR flight plan, under ATC control, Approach assigned me a descent from 8,000 feet to 4,000 feet.
  
  Aircraft operated was a Maule M5 equipped with GPS, which I operate for personal pleasure and business flights. My full time job is flying air carrier aircraft with FMS.
  
  While descending, I began monitoring the VNAV page of the GPS since descent was initiated a bit later than normal. I rarely use this page since its functionality seems awkward compared to the FMS I use at work. A VMC day seemed a good time to use it.
  
  There is no altitude alerting system on the M5 and the GPS will build a profile all the way to the set point, in my case, destination. No protection is provided for intermediate level-off as in the air carrier aircraft.
  
  I focused mainly on the descent profile, being accustomed to this on FMS aircraft, and missed my assigned altitude. Approach queried my altitude when I was at 3,500 feet (4,000 feet assigned) and I realized I had blown it!
  
  ...Most IFR GPSs use a VNAV function that provides very few protections to this scenario. They are advisory in nature, but the pilot may be led to focus on them....
  
  Stepping from a technologically advanced aircraft into a partially advanced aircraft can lead a pilot astray as he/she loses system protections that have been previously available.

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Distraction By Glass Cockpit Programming

Modern digital avionics systems have unique operating techniques and unique functionalities. An unintended consequence of this complexity is that it may create “what’s it doing now, what’s it going to do next” scenarios for unwary pilots, such as this flight instructor and student.

• My student and I were flying an Eclipse jet doing practice approaches. We were holding over the VOR and commenced the Runway 33 approach with the goal of doing a circle approach to a missed approach. Inbound towards the VOR, the student was trying to input the minimum descent altitude via the FMS keyboard. He had inputted it correctly so that the aural warning would announce, ‘Approaching minimums’ and ‘Minimums,’ but was trying to set the MDA into the altitude select window so the autopilot would level off at the inputted MDA. The current avionics suite in the EA50 has a feature that when the navigation page is selected, it returns to the communication page after 30 seconds automatically.
  
  After the student realized he did not ‘drive’ the MDA up to the altitude pre-select, he pushed the concentric knob which would normally drive the minimum altitude to the altitude pre-select window, but at this time the navigation page had returned to the communication page. This caused the communication frequencies to switch over, which made our standby frequency active and we did not catch this. After level-off at MDA, we heard radio chatter but something didn’t seem right and we then changed the frequencies appropriately.
  
  At this time Tower called and said they tried calling us. We apologized, completed the approach and left the airspace. We were given a number to contact Tower.
  
  Upon landing we contacted Tower and he advised us of the impending situation that could have occurred. We told him what happened and he said this was not the first time this happened with the avionics in the Eclipse jet in regards to communication.

  What we learned from this was to ALWAYS verify the transmission frequency as part of the scan because of this 30-second change of [pages] that is standard on the current avionics suite, and be VERY aware of our frequency after the minimum altitudes are selected and driven to the altitude select window.

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