But...if a portable GPS would REALLY cause a problem, then how can it be allowed as navigational equipment?
Admittedly it wouldn't be used in airline flying, but what if you owned a fancy airplane and a Garmin 295? Does this mean that you can't turn it on in case everything else stops working?
What if you were in a 172 and #2 for takeoff behind a 737? or worse you were taxiing out as the 737 was on the roll?
Phones I can see because they were made for a different purpose, but a handheld aviation GPS is made for flying, so how could it cause any problems? Doesn't really make sense to me.