Avionics Glitches While Enroute

[Mark Hargrove]

After being vectored to intercept V23 southbound while flying the I2 routing to KCRQ on Sunday I realized that VOR1 wasn't correctly reporting my position relative to the radial. I double-checked the NAV1 frequency, verified the VOR ident Morse code, and verified that OCN was showing on my G1000's PFD alongside the frequency. Everything was correct -- but the CDI needle wasn't moving as I flew closer to V23. Even though I was navigating by VOR (since that's the point of the early "I" ratings), I'd "backed up" my course by planning KSNA KRAUZ OCN HOMLY ESCON KCRQ on my GPS so that I'd have a second reference to compare to. When I realized that VOR1 wasn't working correctly, I switched to GPS for my navigation, intercepted V23 and continued south on GPS. Once established on V23, I fiddled around with the NAV1 receiver but no matter what I tried, the CDI needle would not move from a fixed position about a 1 1/2 dots away from center.

For the time being, this wasn't a big deal. NAV2 tracked the radial just fine and my GPS was also working perfectly. I knew though, that I was going to need NAV1 to fly the ILS approach into KCRQ. I didn't know if the problem was with OCN or with my NAV1 receiver (or some weird combination of both). I switched NAV1 to the KCRQ localizer frequency while I was still well north of OCN and got what looked like completely normal behavior from the OBS -- max needle deflection in the correct direction for where I was relative to the approach course.

I elected to press on with the flight, deciding that if the VOR wouldn't track the localizer/glideslope I would just declare a missed approach (I had the missed approach procedure already set on my GPS) , tell the controller about the VOR receiver problem, and then request to circle back around and fly the RNAV RWY 24 approach (or, if the airport was VFR, just cancel IFR and land under visual conditions). As it turned out, VOR1 tracked the localizer and glideslope perfectly and the approach and landing were routine.

While doing post-flight review, though, I decided that I maybe didn't make the right decision while I was enroute to OCN with a potentially problematic NAV1 receiver (or display).

Given the circumstances, what action would you have taken when you realized that your VOR1 wasn't correctly tracking OCN?

-M.

[Orest Skrypuch]

Do you mean if the flight was RW ...

Depends an awful lot on weather, and whether you suspect a creeping set of failures.

But, let us say that it is an isolated CDI #1 failure. You could still fly the enroute segment by RNav or Nav2/CDI2. Reaching your destination, you could fly the RNav (GPS) approach to 24, and there is also a circling VOR A available to you. You do not have to rely on the ILS -- unless the weather demanded it.

If the weather was really socked in, then you'd have to navigate to clear weather.

The other big question while in the air, is the failure really isolated? If there is any suspicion, they you need to land as soon as practicable, in particular if there is IMC ahead.

* Orest