Dimming issue and blacked out screens

[APACHE 56]

I experienced an alarming incident today and it was not the result of a failure of either of my GRT displays (HXr and miniAP). However, it points out a potential safety hazard that I bring to your attention. I may find after this post that there is already a solution that I am unaware of.

I experienced a dual screen total blackout and could not get the screens back on line: note that I said nothing failed.

My aircraft is a Vans RV8 which has a bubble canopy. Today in Florida was cloudless sky and very bright. I’m going to try to describe the button pushes that got me into this predicament. I departed Venice, Florida this AM about 0945. While on runway heading and scanning for traffic I wanted to turn the heading bug about 90 degrees North to get me on a gps intercept path. I’ve done it so many times that my left hand just knows about 90 degrees I then pushed the right button to call up the AP heading mode. Looking down to fine tune the setting I was shocked to see both screen blacked out. I went thru all kinds of trouble shooting steps, cb’s, avionics master, frantic pushing of soft keys all to no avail.

First my HXr is on the Master Switch with a TCW Smart Battery so when I start the screen does not reboot. If I had cut the MS that would have helped. Second, the left knob on the GRT HXr has two functions: heading AND Dim. If you are in Screen mode the Dim feature is activated. Two short spins to the left and you are in Blackout mode; but not exactly, more on that later. If you don’t notice that you are in Blackout mode and push any softkey or button the menus change and there is no way in heck you can find your way back. Once back in my hanger with only skylight as a source of illumination the min Dim setting had enough light to see the screen BUT NOT enough light to discern any of the softkey menus which change every time you select a different mode and there is a zillion of them. Once you lose track you are toast.

I am going to recommend that the two screen system (HXr and mini AP) Dim features be decoupled (I’ll get with my avionics installer to determine if that feature is already in place). Second there should be a “panic” button that allows you to go to full bright and start over or a “user selected min Dim” setting in the setup menu. If that is already there I could not find it.

All the avionics manufacturers make a plea with their customers to wring the system out in VFR and that is good advice. I can’t imagine how I’d feel had I been in the clouds.

As an aside when I fly beyond my zip code I always take my iPad and Stratus/Foreflight backup. That was good for an airspeed/altitude swag. Plus I am unable to completely wean myself from analog so I have one of those stackable JPI oil pressure displays and my Electronic Ignition Commander is set on RPM display when I fly. I was an easy flight back to the Space Coast.

[dutchroll]

Sounds like a classic clash of those two titans: human factors and engineering.

I had the same thing occur (on a less critical scale and also under a bubble canopy) with a Garmin Aera. To this day I'm not sure how I made the screen go full dim but being a touchscreen on a bright sunny day with no other controls, it was absolutely impossible to bring it back up until I landed and took it to a dark corner of the hangar to discover what crazy menu nest I was in from my touch attempts.

I'm sure this problem could easily be "designed out" of the HXr. In the engineers' defence it's impossible to foresee all the interesting situations we pilots will end up getting ourselves into!

Mike
Down Under

[Bobturner]

I *think* the external dimmer input overrides the internal one, if present. You can also enter a table of voltage-brightness values. So a simple panic switch would apply buss voltage to an analog input configured for screen brightness. I use one external dimmer for HX, HS, autopilot panel. But for reasons you have now discovered I do not connect it to the backup Dynon D6. I tried to keep the backup as isolated from everything else as possible, for exactly the reason you found. It's hard to anticipate how a failure, including pilot error, will propagate thru the avionics.
edit. I should have mentioned that this is a tough problem. The brightness I want on a dark night is so low that the screen cannot be seen at that level in the sunshine, so I cannot just set the minimum level brighter (but if you only fly in the day, you could).

[Marc]

I replied to this via the support email, I'll post my reponse here as well.

The HXr is pretty easy to get to dim. If the Left encoder is not on DIM, press the second button from the left and then turn the Dimmer knob. Memorizing the method on both the HXr and the Mini is an option if care is taken to not turn the knobs unless you are 100% sure that you are not in the screen menu which allows the unit to Dim. If you do dim the screen, simply turn the knob back up to full brightness. If somehow you exit the screen menu, simply press the second key from the left and then turn the left knob to turn the brightness back up. It is strongly recommended that you are competent with your displays especially navigating the menus and knowing what the buttons and encoders will do before pressing them prior to flying into IMC.

If you would like to break the link between the HXr and the Mini AP, go to Set Menu > General Setup > Inter-Display Link. Then Scroll down to "Dimmer Link" and switch to off.

Alternatively if you don't fly at night and won't need to fully dim the unit, you can set the minimum dim setting to a bright level. This will prevent the screen from dimming down below the value that you set. To do this go to Set Menu > Display Unit Maintenance > PIC Calibration Data. Then scroll down to "Dimmer Minimum Override" When you select it, the screen will dim to the minimum level. Simply turn the knob until you get the minimum dimmer setting desired. This brighter level will be the new "1" Dim setting and the other values (2-9) will be re-scaled. To regain the full dimming range, change the Dimmer Minimum override back to the Stored Dimmer Minimum value and it will turn off when you set it.

If you only fly during good sunlight, you could set the unit to not dim at all. To get full brightness all the time, you could set an analog input to Dimmer by going to Set Menu> General Setup. Then find an unused Analog Input (1-8), set it to dimmer, and turn the pullup resistor for that analog input to on. This will force the screen to full brightness all the time.

Another alternative is to use an analog input connected to a potentiometer on the panel. This will allow you to use a dedicated knob on your panel for only dimming. Both the HXr and Mini-AP can be set this way through the HXr with the Inter-Display Unit Link turned on. If either unit tries to dim the screen, the Analog Input will override it.

For those that fly at night, an option for full brightness would blind them if it was accidentally triggered. They wouldn't be able to see their panel, or out the window until their eyes adjust. For this reason, we have decided not to add the option to go to full brightness.

-Marc Robertson
GRT Avionics

[GordonTurner]

My thought is that anytime power is removed and reapplied to the efis the screen should come back on at full bright or at least at some reasonably bright setting.

Another idea would be to have a specific button combination, keep it the same throughout the entire line of efis', like simultaneously press the two outermost buttons, returns to full bright.

Trying to navigate blindly through menus to restore brightness that you didn't intentionally reduce sounds far less than ideal. Problematic also if the unit was shut down very dim at night and now you're powering up in the bright sunlight.

Isolating the backup attitude source as much as possible seems like a very good idea too Bob.

Gordon