AOPA will be closing at 2:30pm on Friday, May 24th and will also be closed on Monday, May 27th. We will reopen Tuesday morning, May 28th th at 8:30am ET.
Get extra lift from AOPA. Start your free membership trial today! Click here

Partial-panel in the PFD era

Realistic instrument failures while flying ‘glass’

By Bruce Williams

The most unrealistic task in the Instrument Rating-Airplane Airman Certification Standards, the standards for IFR-related practical tests and instrument proficiency checks, is VII D, “Approach with Loss of Primary Flight Instrument Indicators.”

Failure of the AHRS in a G1000 as shown in an ATD, the best tool for learning about system and component failures in a glass panel.
Zoomed image
Failure of the AHRS in a G1000 as shown in an ATD, the best tool for learning about system and component failures in a glass panel.

The ACS explains that the goal of that demonstration is “performing an approach solely by reference to instruments with the loss of primary flight control instruments.” The document further specifies that “One [approach] is expected to be flown with reference to backup or partial panel instrumentation or navigation display, depending on the aircraft’s instrument avionics configuration, representing the failure mode(s) most realistic for the equipment used.” But while the ACS also emphasizes “risk management and skills,” training for that task typically doesn’t prepare you to deal with the challenge on a real instrument flight.

First, when we practice or demonstrate a partial-panel event, we pretend that we’re on our own. We don’t declare an emergency and ask ATC for assistance such as no-gyro turns—certainly no holds or instructions that require combinations of turns, descents, and speed changes. Instead, during training and on the checkride, we fly an otherwise normal approach looking at the backup instruments, with ATC none the wiser.

Second, given the myriad combinations of avionics now available in even a basic GA aircraft, “failure mode(s) most realistic for the equipment used” isn’t much help if you’re trying to teach or practice partial-panel scenarios realistically in an aircraft with particular complement of “glass.”

For example, when flying an aircraft with a Garmin G1000, most instructors demonstrate partial-panel by dimming the primary flight display (PFD), and the student pushes the big red button between the screens to convert the multifunction display (MFD) into a display of key information—attitude, airspeed, altitude, heading, and a course deviation indicator. Those actions simulate failure of the display, but not underlying systems, such as the attitude heading reference system (AHRS) or the air data computer (ADC).

And what does “loss of primary flight control instruments” mean if your panel is based on an Aspen Evolution 1000 or Garmin G5s with standby batteries? Does “backup or partial panel instrumentation or navigation display” include an EFB that, in addition to providing a moving map, can also display synthetic flight instruments using its built-in sensors and GPS-derived ground speed and altitude?

Garmin publishes free PDF guides for CFIs, designated pilot examiners, and flight schools that offer some help. For example, DPE and CFI Avionics Guide-G1000 NXi recommends using sticky notes to simulate failure of a single G1000 component (“For example, to fail AHRS, cover the attitude indicator.”) That guide also offers “Method 2: Dimming the Display (Preferred-Display Failure).” The similar DPE and CFI Avionics Guide: Retrofit suggests methods for simulating failures of PFDs such as the G500Txi, G5, and GI 275, and navigation systems like the GTN and GNS avionics. The Integrated Flight Deck Pilot Training Guide and its companion instructor’s guide, also from Garmin, are additional training resources. You can adapt those procedures if you fly with avionics from other manufacturers. Note that Garmin does not recommend pulling circuit breakers to simulate failures. That advice is consistent with Special Airworthiness Information Bulletin CE-10-11 and AC 120-80 from the FAA.

To understand how to deal with realistic-partial-panel scenarios, first learn the backup features of and connections among the avionics in the aircraft you fly. For example, if the PFD in a G1000 system goes blank, you also lose the number 1 com and nav radios. Failures of internal components such as the AHRS or ADC limit the information shown on panel displays and restrict autopilot functions. (To see one example of this process, see “Flying Smart”)

Next, practice techniques for dealing with realistic failures, first in an aviation training device (ATD) or other simulation, then in an airplane while operating under VFR. For example, if you lose the heading indicator, forget about trying
to wobble through compass turns. Instead, inform ATC (or your fiendish CFI) that you’ll fly GPS tracks, using the moving map, track bug, track trend vector, and digital track display to keep you pointed where you need to go until you can monitor a CDI to fly an approach to a runway.

Suppose all the navigation receivers in your panel fail. With a GPS-enabled EFB, practice using the own-ship symbol and trend vector on georeferenced charts to intercept courses and final approach paths (you can connect an EFB to most simulations). The climb/descent gradient display available on most EFBs can
help you fly a stable descent when a glideslope or glidepath isn’t available. Finally, learn how to maintain control with only the synthetic vision instruments on an EFB.

To simulate GPS failures, use bearing pointers to maintain situational awareness and navigate to and from VORs. To test these skills, turn off the own-ship marker on your EFB and set your MFD to the traffic page, which still provides warnings about nearby aircraft but doesn’t show where you are.

Finally, remember that partial-panel scenarios reinforce the value of basic attitude instrument flying skills. If you set a pitch attitude, adjust the manifold pressure and/or rpm to a known combination, and then select flaps and landing gear for a phase of flight, predictable performance results. Knowing and practicing the key “numbers,” for example, for the intermediate stages of an approach and for a stable
descent along the final approach course, greatly reduces your workload when you’re coping with instrument and navigation failures.

For more information about practicing partial-panel scenarios and related IFR skills, see “When the Screens Go Dark” in the January/February 2023 edition of Flight Training and “Sipping Information from the Right Glass” and “What’s the Point?” in the December 2023 and August 2023 issues of AOPA Pilot.

Bruce Williams is a CFI, writer, and aviation consultant. Find him at youtube.com/@BruceAirFlying and bruceair.wordpress.com

Failure of the top G5 in a dual G5 setup converts the HSI into a PFD that includes navigation information. You can use large sticky notes to simulate different system failures. Trim them to obscure specific information. If you lose the heading display, don’t chase the compass when GPS track information is available.
Click images to enlarge and view captions.

Related Articles

Get the full story

With the power of thousands of pilots, members get access to exclusive content, practical benefits, and fierce advocacy that helps enhance and protect the freedom to fly.

JOIN AOPA TODAY
Already a member? Sign in