Using a Car GPS for Flight Navigation

[dov_elyada]

I fly an ultralight. Typical altitudes are 500' AGL and navigation is by landmarks. Where I can't recognize the landmarks, or where distinct landmarks do not exist or are far-between, I switch to using uncorrected compass bearings -- good enough, considering the relatively short legs and the mild-wind days I select for flying.

Recently I installed in my plane a car GPS device (QUE NQ-503) running a cross-country land navigation software. (After all, the difference between 500' AGL and an SUV's 5' AGL is not all that big.) The software is basically a moving 1:50,000 topographic map on which one can add routes and labeled waypoints. To navigate, all one has to do is keep the GPS position marker on the prepared route. Can't ask for anything more.

For about 10 flight hrs this device performed just fine. Then hardware problems set in which gradually made it useless. I suspect the reason lies in the harsh acoustic and vibrational environment (unbearable without a headset on) that exists on the dashboard where the device has been installed. Indeed, when I moved it back to my car the problems went away.

My questions:

1. Anyone out there with a similar experience?
2. Any suggestions as to how to protect the device from the environment?
3. Are aviation GPS devices guaranteed to withstand an ultralight cockpit
acoustic and vibrational environment?
4. What kind of backup people use in case the GPS malfunctions (apart from
radio homing)?
5. Anything else that might be helpful in this respect.

Thanks for the advice