azure
Final Approach
At my fuel stop today, about two minutes after starting back up, my Sandel HSI display went completely dark. The control buttons were still illuminated (hard to see this in daylight, but after dark it is obvious), but the display was completely dark, and therefore I had lost not only a nav instrument but also my DG. I had intended on picking up an IFR back home but obviously that would not be legal now, so I limped home VFR.
At first I thought it was a simple projector bulb failure - the bulb is supposed to be replaced every 200 hours or one year, but mine had run about 100 hours in the last year and a half. The reason I'm concerned it may be something worse than that is that when the unit is powered up in flight, the SUSP annunciator comes on on my 480, and goes off when the Sandel is powered down. I'd never power cycled the unit in flight before and wasn't sure that was abnormal, but after landing I tried letting all the avionics boot normally, and the SUSP annunciator was still there even after WAAS was in use and a valid flight plan from the current airport was EXEC'd. In this last instance, the annunciator flashed on and off at irregular intervals, even after pressing the SUSP button.
However heading info is still being output to the autopilot, since with the A/P in heading mode, the heading bug will still command turns. I didn't think to try either the SYNC button or to check if the OBS control still works in conjunction with the HSI view on the 480 map page, but will do that next.
Any suggestions of other things to try would be welcome. I also considered that engine vibration might have caused the Sandel to unseat partially, but that seems unlikely as it hasn't happened before, because my avionics tech a couple of years ago fashioned a fix to prevent that from happening, and because the plane is over 20 hours out of its last maintenance (annual) where something might have been disturbed.
At first I thought it was a simple projector bulb failure - the bulb is supposed to be replaced every 200 hours or one year, but mine had run about 100 hours in the last year and a half. The reason I'm concerned it may be something worse than that is that when the unit is powered up in flight, the SUSP annunciator comes on on my 480, and goes off when the Sandel is powered down. I'd never power cycled the unit in flight before and wasn't sure that was abnormal, but after landing I tried letting all the avionics boot normally, and the SUSP annunciator was still there even after WAAS was in use and a valid flight plan from the current airport was EXEC'd. In this last instance, the annunciator flashed on and off at irregular intervals, even after pressing the SUSP button.
However heading info is still being output to the autopilot, since with the A/P in heading mode, the heading bug will still command turns. I didn't think to try either the SYNC button or to check if the OBS control still works in conjunction with the HSI view on the 480 map page, but will do that next.
Any suggestions of other things to try would be welcome. I also considered that engine vibration might have caused the Sandel to unseat partially, but that seems unlikely as it hasn't happened before, because my avionics tech a couple of years ago fashioned a fix to prevent that from happening, and because the plane is over 20 hours out of its last maintenance (annual) where something might have been disturbed.
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