"Why do I need to suspend navigation on my GPS in a hold? I have a Garmin 430 and find this confusing." - Justin M.
“When we’re holding, we have to suspend the navigation of the GPS. A GPS wants to navigate very much like a flight management system; sequentially, from fix to fix to fix. We don’t really navigate from anywhere. We’re always navigating to somewhere.
And as it reaches a fix, a way point, it sequences on to the next one. But obviously, when we hold, we have to suspend that sequencing, and different units do it different ways. We have to be aware of that and we have to be aware of some of the gotchas within it.
Even an example with a Garmin, which will give you a hold if it’s published, and tell you how to do it. We have to understand perhaps the hold is a procedure turn. Perhaps, as the initial fix for an approach, we have a hold. So the GPS, as you fly across the fix outbound, will suspend because it isn’t going to sequence on up to the next, perhaps, the final fix. Say there are just two fixes – the initial fix and a final fix – and at the initial fix, we’re going to have to do a procedure turn depicted as a hold. So as we cross that fix, the GPS suspends.
Now, as we turn inbound, it automatically – this is a Garmin 430, 530, G1000 – it automatically will cancel that suspension so when we cross the initial fix now, it sequences on to the final fix. Not a problem.
But what if ATC says, Cardinal 88Q, we’ve got another guy on the approach and he’s been there a while but he hasn’t cancelled, so expect a hold at the initial fix, 4,000 and expect further clearance tomorrow.
Now we’re up there and we’re going to have to hold at this fix. We have to understand it has suspended as we go outbound; as we turn inbound, it has cancelled the suspension. We have to re-suspend, and if we don’t, as we cross that fix it will sequence on to the final fix, and if it does that how are you going to get back? We need to know how to do that if we’ve made that mistake.
So these are some of the gotchas in holds with GPS.”