DE727UPS
Well-Known Member
I don't have access to this full article. Anyone with an IFR subscription care to post it?
I bring this up because I've always been trained that following the FMC or GPS derived vertical path will keep you safe to 50 feet above the touchdown zone. Not long ago I was doing a day VMC visual backed up with the localizer into an airport I can't remember. I've gotten used to using the path indication as a substitute for an electronic glide slope in the rare occasion we don't have a full ILS. I tend to crosscheck the outside runway environment picture with the inside VNAV path and VSI descent rate, especially between 500 feet AGL until and I start looking solely outside to begin the flare. So, there I was on path, at about 200 AGL, and my F/O calls out "red over red, a little low". I looked out and sure enough, I was red over red on the VASI and I needed to make a correction. I looked back inside for a flash to confirm my VNAV path and it showed me dead on the proper path while the VASI showed me low. I was a surprised by this but just passed it off to me being an idiot who needs to get out more.
Then, we lost an A300 in BHM on a night non-precision, and it kind of got me doing some research. I clarified what our training guide says, which paraphrased is "use the VNAV path as a reference but outside visual contact with the runway must be maintained". I'm starting to wonder, though, if the VNAV path will keep you out of the trees on runways with high terrain on final approach. I'm thinking that the VASI or PAPI will be all that's keeping you safe and perhaps the path should be ignored, or certainly considered a secondary indication, once you are below the MDA.
Just wondering what others have experienced.
I bring this up because I've always been trained that following the FMC or GPS derived vertical path will keep you safe to 50 feet above the touchdown zone. Not long ago I was doing a day VMC visual backed up with the localizer into an airport I can't remember. I've gotten used to using the path indication as a substitute for an electronic glide slope in the rare occasion we don't have a full ILS. I tend to crosscheck the outside runway environment picture with the inside VNAV path and VSI descent rate, especially between 500 feet AGL until and I start looking solely outside to begin the flare. So, there I was on path, at about 200 AGL, and my F/O calls out "red over red, a little low". I looked out and sure enough, I was red over red on the VASI and I needed to make a correction. I looked back inside for a flash to confirm my VNAV path and it showed me dead on the proper path while the VASI showed me low. I was a surprised by this but just passed it off to me being an idiot who needs to get out more.
Then, we lost an A300 in BHM on a night non-precision, and it kind of got me doing some research. I clarified what our training guide says, which paraphrased is "use the VNAV path as a reference but outside visual contact with the runway must be maintained". I'm starting to wonder, though, if the VNAV path will keep you out of the trees on runways with high terrain on final approach. I'm thinking that the VASI or PAPI will be all that's keeping you safe and perhaps the path should be ignored, or certainly considered a secondary indication, once you are below the MDA.
Just wondering what others have experienced.