The Question is: can you disable IRU updates on your Glass Boeing or y. Glass Airbus?
Iceman50 raised a bullshat flag. Good. Since I have never flown a Glass Boeing I wasn't aware that 757/767 had 18 mile map shifts on the procedure turn.
But I stlll need the questioned answered: on Glass Boeings can you disable automatic nav updates after you I.D. the primary navaid and commence approach? Of course in the developed world, maybe the navaid maintenance is good enough that you don't need to do this.
I have already explained that the first airbuses were not really designed for disabling auto updates; and initially, with many carriers, this precaution was not taken.
Although map shifts are increasingly rare in the Western world, they are not unknown in the developing world. I keep citing the first Airbus because that is where Toulouse cut it's teeth on Glass. IIRC, the honeywell FMC box would take a polling of all three IRU's and then average their position for the new center IRU position. Then it would skew the map with updates based on a complex algorithm. If one IRU update position was skewed 50 miles the wrong way because it decided to update itself off a VOR in a war torn country which was overheating, the whole moving map central position might get moved 5 to 10 miles the wrong way (depending on geometry and other logic).
Right?
Yes, you're supposed to keep the runway in sight. but if your moving map says you are close, it is a prelude for overconfidence. It was well documented in July, and August 1995, I believe, AW&ST that Airbuses where designed to reduce crew workload but instead, vastly increased it.
Last minute runway changes are the devil for a green First Officer to deal with. A new F/O will be damn lucky to get all his crap done before base turn. His head is now down pushing buttons and nobody is watching if his Airworthiness is even still alive over there. With that cursed sidestick he's already slumped down on the armrest like a patient donating blood at the Red Cross. How would the pre-occupied F/O even know if he was having a stroke? Who's watching him?
Only ATC is watching him, and one poster said they tried to save him.
Who's listening to the morse code?
Nobody.
Who's looking at the raw DME to see if it jives with the Moving Map?
Nobody.
Who's looking out the front windscreen while the old boy is looking over his shoulder behind him trying to reacquire the threshold?
Nobody
Crunch
Note: All my posts are just my opinion only.
Last edited by Captain-Crunch; 29th Jul 2010 at 03:56.
Reason: disclaimers