capturing glideslope before localiser

[ashun 8]

IN PMDG 777 capturing glideslope before localiser is off in default setting. 

Does anyone know in real life, is this option available for pilots or do they always have to capture localiser before glide slope?

 

Thanks

[skelsey 765]

From a technical point of view it is an airline option as to whether GS capture is possible before LOC green is annunciated - some aircraft are programmed to allow it, others are not.

However, from an airmanship point of view it is a big no-no to be locked on to the glideslope before localiser capture and at least one big airline I know of has a specific SOP (at least on the Jumbo - don't know about the 777 as I don't know what pin programming option they have in this regard on that fleet) to not press APP until LOC green is annunciated in order to prevent this.

[ashun 8]

ok, thanks a lot.

 

[downscc 1,327]

6 hours ago, ashun said:

is this option available for pilots or do they always have to capture localiser before glide slope?

What Simon says... he is a very well informed regular here.  Also, there is an issue with the glideslope beam where secondary beams at much higher angles than the primary beam, which is usually 3 deg.  To ensure you are on the primary GS beam you should be on localizer then intercept glide slope at a predictable altitude.  Some published procedures have a mandatory altitude from which you then intercept glideslope...,. most will have may IF fixes beyond the FAF (intermediate and final approach fix) and ATC might vector you to final near any on of those.  Regardless.... you know that 3 deg is 318 ft/nm so you can predict where that glideslope is based on your distance from the runway.  Rough rule of thumb is glideslope changes 1000 feet for every 3 miles.

[BlueStar 323]

16 hours ago, skelsey said:

From a technical point of view

Simon,

For me it's RNAV to the LOC.  This new magic makes my life much easier. 🤣

Grace and Peace,