Surveillance Radar Approaches

[Pengintai]

I am an A330 driver, please bear with me on these dumb questions. I am interested in the display that ATC uses to conduct an SRA. My interest is that my company specifies that an SRA is conducted with TRACK/FLIGHT PATH ANGLE selected, in this mode we have to allow for drift (a relatively straight forward procedure) to make good an ATC requested heading.

Is it possible for your display to be reset such that you can issue track instructions, rather than heading instructions? Thanks for your patience with this question!

[BDiONU]

When doing SRA's the heading you give is based on the observed track. No point attempting to apply standard headings when you don't know what the winds doing.

[2 sheds]

Pengintai

Not a dumb question at all - so very often the customers do not realise the type of kit with which we are working, just as it is difficult for us to keep up with everything that you have.

It sounds to me as if your company is getting its wires crossed somewhat and making life rather complicated. I should have thought that if you are flying a SRA on autopilot, it should very definitely be in heading mode. If you ask the autopilot to fly a track, presumably that would only be of any use if it were set exactly when on the final approach track? That aside, the radar controller will always give instructions in terms of heading in order to maintain or regain the final approach track specified on the IAP chart, so we could end up working at cross purposes! This will take account not only of the observed drift due to crosswind component but, very often, particularly for an approach with RTR less than 2 nm, the anticipated change in drift in wind shear conditions. The displayed radar information being, by definition, history, and the position being updated only every 4-6 seconds, this really is necessary.

Regards
2 S

[radarman]

We had this problem at my unit a few years back when ZB started flying in A320's. Couldn't work out why their headings on SRA's were always 5-10 degrees different from 737's. Spoke to several crews, and apparently the reason is that Airbus mandate flying 'track' instead of 'heading' when making a non-precision approach. (SRA's count as non precision because there is not an electronic glidepath). It seems most airlines have carried this through to their own company operating procedures. As I understand it, when 'track' is selected the aeroplane's electronic gizmos continually vary the heading, according to the wind at the time, to make good the required track. This actually makes SRA's a piece of doddle if the controller knows you are flying track- all he has to do is get you to the centreline, pass the runway QDM and hey presto, the aeroplane automatically flies itself down to the runway regardless of crosswinds. No more "Turn right 5 degrees/ slightly left of centreline turn left 5 degrees blah blah blah". That's what we do at my unit. Only trouble is I'm not totally sure how SATCO's at different units or the CAA SRG view the legality of your flying 'track' when the controller is saying 'heading'. (We say 'track' here for A320's). SRG haven't queried it here though. The only suggestion I can give is that you inform the controller that you will be flying the SRA using 'track', but whether he will understand the implications is another thing. Especially overseas. Another case of ATC equipment and procedures lagging years behind flight deck developments.