Dealing with Display Failures

by HPA · September 3, 2011

What To Do When Murphy Shows Up, Part II

By Hank Gibson, CFI, CFII, MEI

Dealing With GDU Failures

On the long list of what can go wrong in a G1000 cockpit, a Garmin Display Unit (GDU) failure is less of a Maalox moment than other failures. A non-proficient pilot, though, might be lost when the PFD or MFD goes black. Here’s how to handle the situation. (Note: This article will only deal with the traditional G1000 configuration with one PFD and one MFD)

The GDU and the Failure

The reader may have seen the subtitle for this article and thought, “GDU failure? What does the Global Defense Union have to do with flying and why do I care when they fail?” (Please, hold all laughter till the end) A Garmin Display Unit, or GDU, is the name Garmin gave the computer that runs the Primary Flight Display (PFD) and the Multi-Function Display (MFD). They are commonly referred to as screens, so pilots may be more familiar with the term “screen failure” instead of “GDU failure.” Screen failure seems to flow off the tongue a little better, but it’s a computer, so there has to be a technical term for it.

Like the AHRS/ADC failure, most pilots won’t ever experience a GDU failure, but, it is always best to maintain proficiency with any and all possible failures. The best thing to do is to go up with an instructor and do a few instrument approaches with one or the other GDU failed. Change it up a bit for the different approaches, as well. Fail the MFD on one approach, then fail the PFD on the next approach. The scan on the MFD failure is much easier since everything moves to directly in front of the pilot, but since when does Murphy’s law ever mean easy?

Regardless of which display fails, the procedure is the same. For this article, I’ll just discuss an MFD failure (Note: With a PFD failure, the only difference will be the pilot will have to turn his head to the right and scan the MFD). In training flights with my students, I usually like to fail the MFD first since, most of the time, he will just sit there and continue scanning his instruments. The thought process is, “Okay, I lost my moving map, but I still have all my instruments in front of me. I don’t need to do anything, I’m fine!” WRONG. It might be important to know if the engine is running properly too….

I usually try to give the failure when we are close to a descent. If the student starts the descent and still hasn’t done anything, I usually ask some leading questions to get him thinking about power and engine gauges (or he might start the descent, realize he can’t see his tachometer, then start to wonder how to read engine RPM with a dark MFD). I always brief the student on the failure and what to do on the ground, but, in the midst of an instrument approach, he will sometimes forget.

Now, the light has usually come in my student’s mind that, “Oh yeah, I need to see my engine information! What color was that button? Oh yeah, the red display backup button!” Bingo! I love seeing light bulbs come on.

Display Backup Button

G1000 Display Backup Button

The red display backup button is at the bottom of the GMA Audio Panel, right below the intercom volume button. In a simulated display failure, all a pilot has to do is push that button and that will move the GDUs into reversionary mode. In this mode, both the PFD and the MFD will display the same information: all the flight instruments along with the engine indicating system along the left hand side. The giant moving map is lost, but the inset map is still available. In this instance, a pilot would have to choose between the inset map and the flight plan because they are both displayed in the same place on the screen.

Now, the way Garmin designed the system, if a GDU actually does fail, then the system will automatically go to reversionary mode. In an actual failure, all the display backup button is used for is, simply, backup in case some wires aren’t doing what they are supposed to. Otherwise, the system should enter reversionary mode on it’s own and the pilot doesn’t have to do a thing! Isn’t technology great?

Reversionary Mode PFD

All pilots hope to never ever have a failure, but it still happens. Hopefully, parts one and two of this article series will help keep pilots a little safer out there.

How it Started

One of my best friends in high school, (Doug Gray) was a private pilot. He offered to take me up for a flight in a 1967 Cessna 150, N6228S. We took off from Calhoun, Georgia, and he took me on a scenic tour of the area, I was hooked. I later found out that my English teacher, (Jan Haluska) was also a flight instructor and the school was offering a ground school course the next year, which he taught, along with flight training with the goal of becoming a private pilot. I managed to talk my dad into funding the training, at the time the total cost was right around $500. Cessna 150 rental rates where $12 an hour, and the 172 we used for cross country was $15 an hour including fuel.

Training Begins

It started August of 1977. The fall semester rolls around, and I am enrolled in ground school, and if memory serves me, we met twice a week. First came the paperwork for my student pilot certificate, which at the time was included with the 3rd class medical. I loved ground school, especially learning navigation, plotting courses on the sectional, again this was before iPads and GPS, so we did a lot of dead reckoning and VOR navigation for cross countries. At the end of the course, I made an 83% on the Private Pilot written exam, remember this was before we had the question-and-answer books that on future test I would consume before taking a written.

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The fun really began on August 22, 1977, it was my first flight. To my surprise we used the same Cessna 150, N6228S that my friend Doug Gray had taken me for a ride in. The Cessna 150 had a standard VFR instrument panel, with one NAV/COM, and one VOR CDI. No intercom, so no headset, at the time I didn’t know what I was missing. I didn’t get my first headset until I started my instrument training in 2003. I was a big guy, I was 6’ 4” and weighed 245 lbs. but I do not remember being uncomfortable in the 150 even with the instructor in the right seat.

First flight lasted .8 hours, and we accomplished orentation, shallow turns, stability, and effects of flight controls. Over the next few months we added steep 720’s, slow flight, stalls, turns around a point, S-turns, emergencies, landings, (short field, soft field and normal).


At this point I want to talk about a training experience that still stands out. We were close to solo and were practicing takeoffs and landings. Turning base to final Jan got very upset at the way I was cross controlling the aircraft. Cross control is when you are in, say a left turn, and use opposite rudder to line the nose up with the runway. So, he had me depart the pattern and head east to the practice area, and climbing up to 5500 feet MSL, he had me slow down to just above stalling speed, start a left shallow turn and add right rudder. As the airplane stalled I had the strangest sensation, no roller coaster has ever come close, instead of blue sky in the windscreen I was looking at brown ground, and as far as I could tell we were upside down, through the terror of the moment Jan talked me out of the spin, controls neutral, oposite rudder, pull slowly out of the dive. As we leveled off he asked me what altitude we were at, as I remember it was around 2,800 feet MSL. Then he asked me what would happen if I experenced this on base to final in the traffic pattern. The answer was obvious, I would be a pile of wreckage off the end of the runway with a very short-lived aviation career. Needless to say this cured my cross-control tendencies.

Another training event the sticks out in my mind was the first time we did takeoffs and landings at the High School runway. The runway was 1,500 feet long, not sure of the width, but it seems like we had about 5 feet on each side of the wheels when on the center line of the runway. Landing from the south you also had to go between a cutout in the trees to be able to stop in time on the runway. After getting confortable landing here every runway since seemed huge. I remember landing at Chattanooga (KCHA) on a night cross country and commenting to Jan, that I felt like I could of landed sideways on the runway, it felt that large.

Very soon after this I started wearing old shirts to all my flight lessons, the reason for this occurred on February 8, 1978. The lesson that day was stalls, takeoffs and Landing. As we were taxing back in Jan told me it was time for my first solo. I was very excited, and after some last minute advice from Jan, including watch for floating on landing the plane will be light with him not in the right seat, complete 3 takeoffs and landings to a full stop. It was a blast, and at the end of my shirt was shorter in the back because Jan cut the tail out of it signed and dated my solo [an aviation tradition]. Total flight time accumulated on the day of my solo was 18.1 hours. I was now officially a pilot with solo priveleges.

In my next article I start cross country training, when Jan decided that it would be best accomplished this in the 172. Checking out in N5970R was like moving into a 747, this started a love affair with one of my faviriote planes to date. Since this time I have flown over 900 hours in many different models of the 172 and feel like I am stepping into an old friend every time.

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