Help: Airbus FMGS Offset Question please

[Melissa_Bettochi]

Hi,

I have a question regarding offset of current track when required by ATC in Airbus 320. It may be a silly question however!

Say I am flying to a point on track of 295 in HDG mode and ATC require me to offset my track by 5 degrees to the right. I enter 5R on the F PLN page of the FMGS. However, I must then turn towards this heading and push Nav to intercept. My question is, how much should I turn towards the right? Do I turn as extreme as 330 degrees. Is there a particular rule of thumb? Am I turning too much or too little??

Any urgent help is much appreciated!

Thanks

[jtr]

Hi there,

The "simple answer" is - Go direct to said waypoint then once in NAV put in a 5nm offset and insert...


Little bit of a unusual question as I have never been asked when on a HDG to offset, they just give you a different heading.

How it usually happens...

On HDG 295... ATC want a further 5 deg right... they say "Turn right HDG 300"

or

In NAV... ATC want an offset.. they say "Offset 5 miles right of track"

Option A - in the offset box put 5R... insert (Most A320 FMGC)
Option B - in the offest box put 5R plus the intercept angle and start/finish point (R1A FMGC upgrade installed)

In a roundabout way related to your question... the box will give a 30 deg intercept angle from memory.

[Slasher]

It may be a silly question however!

Not a silly question at all.

I had a quick look in ICAO Annex but can't find anything on
max dist longitudinally to be fully offset laterally. However if
in HDG and instructed to offset, I fly 60 deg off the route for
2/3 the offset dist, then 30 deg till intercept. TK is useful in
strong XWs (320). The box can also do it but sometimes the
FO might be busy on the typewriter when the call comes in.
In that case while in NAV I just pull HDG and do the above.

[vilas]

The purpose of offset function is to fly the offset track without getting out of NAV mode. In heading mode you need fly or correct the heading as asked by ATC.

[STBYRUD]

Wait - I am a Boeing man, but heading and track should be the same for both! You said you were flying towards a point in HDG (295), if ATC wants you to fly 5 degrees to the right you just twist the heading bug to 300 - what is the issue? That has nothing to do with an offset?! If you are flying an airway and are supposed to fly 5NM (NOT degrees) offset to the right, then you would use the FMS for that surely?!

[Neupielot]

I think he meant offset 5 nm to the right .

[macdo]

If you are using the latest FMGS then you also get the opportunity to define the angle with which you would like to intercept the offset. We only got this function last week and its a big improvement on the standard 30 Deg. which tended to involve a fairly energetic bank angle. FMS2 Rev 1.a has lots of new and handy tricks up its sleeve.
"Rev 1A includes additional options for the lateral offset function. The offset can now be
defined by a Start Waypoint, End Waypoint, Intercept Angle and an Offset distance. "