Foggy weather

[kenparry]

Dumb question from SLF: does GPS play any part in auto-land nowadays?

Not a dumb question, but no it does not. The guidance to the required accuracy comes from the ILS both in azimuth and vertically, with some input from the radio altimeter for the flare, and autothrottle for speed control.

[victor tango]

This discussion about Trident landing system reminds me of a delightful pipe smoking regular in my local back in the 90s.
He was on the team that designed and made it but always kept a low profile and shrugged it off as a sort of just another job ! Never bragged.

I asked him one night after work where I was having an AOG prob during that day. I said to him I couldn't understand why the MEL said AOG for a galley fan !
I thought is was a misprint.
He took a puff on his pipe, then said "I think you'll find that the same fan cools the radio rack" and this was a 747-SP ! I doubt if he'd ever seen one !
I bought him a pint.

[ExXB]

Originally Posted by kenparry

Not a dumb question, but no it does not. The guidance to the required accuracy comes from the ILS both in azimuth and vertically, with some input from the radio altimeter for the flare, and autothrottle for speed control.

Augmented GPS is being used at some airports ... Juneau, Alaska for example. Aircraft and airport both need to be equipped but it has reduced the number of diversions significantly.

From http://www.aiaa.org/uploadedFiles/Ab...Nomination.pdf

The trend today in the Next Generation Air Traffic Management System is toward an Area Navigation concept known as RNAV, with an even greater role for GPS. Area Navigation allows aircraft to fly user- preferred routes from waypoint to waypoint, where waypoints do not depend on ground infrastructure. The accuracy provided by space-based navigation systems increase safety in flight and on the ground. Terrain Awareness and Warning System performance is enhanced; GNSS-enabled ADS-B (Automatic Dependent Surveillance-Broadcast) significantly improves in-flight aircraft avoidance and ground operations (especially runway incursions). RNAV implementation at Juneau, Alaska has enabled 75% lower arrival minimums compared to Standard. In many cases, aircraft flying over data-sparse areas such as oceans have been able to safely reduce their separation between one another, allowing more aircraft to fly more favorable and efficient routes, saving time, fuel, and increasing cargo revenue. GPS also serves as an essential component for many other aviation systems, such as the Enhanced Ground Proximity Warning System that has proven successful in reducing the risk of Controlled Flight into Terrain, a major cause of many aircraft accidents in the past.

We could see this technology expand to other airports, but the airlines would need to agree to spend the money equipping their aircraft.