PPRuNe Forums - View Single Post - Few questions regarding a320 flying (general)
Old 27th Dec 2011, 19:58
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CAT3C AUTOLAND
 
Join Date: Jun 1999
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When activating the approach phase and descending on managed speed, and managed altitude, will the aircraft descent at thrust IDLE? Will it go at it's own pace to maintain a good rate of decent and be at an appropriate speed, allow you to slow down nicely to configure?
For this one take this example. Aircraft is flying a STAR followed by an approach. ATC clear you down to the platform altitude of say 3000ft. Lets say the aircraft is descending through FL120. The aircraft at this stage is in NAV and Descent mode. The managed speed target is the ECON speed computed by the FMGC. The ATHR mode will depend on where the aircraft is with regard the vertical profile. Typically the aircraft will be in Thrust Idle to maintain the descent, using speed changes in pitch to control it (you will see this speed band on the PFD). However if the aircraft should descend below the profile, the ATHR will go into speed mode and use thrust to maintain the ECON speed, and will descend at 1000 ft/min until the descent profile is regained.

As the aircraft goes through FL100 the speed will then come back to 250kts, unless deleted by the pilot. As the aircraft approaches 3000ft, there is usually a level flight segment computed by the FMGC. On the ND you will see the magenta D in a circle, which is the deceleration point, where the approach phase is automatically activated. The speed then comes back to green dot. In managed speed the speed is now controlled by the flap lever. Of course the pilot could activate the approach phase through the FMGC, however it is not necessary in managed NAV. If flying in HDG mode, the aircraft will not fly over the deceleration point therefore the pilot has to remember to activate the approach phase in the FMGC.

If ATC has not given you any specific speed, is it up to you what speed to slow down to?
It is up to the pilot, however, managed speed is recommended. However, this really depends on the circumstances. For example, if there is no speed control and say ATC have left you high, then I would use a selected speed increase to lose the altitude. But on saying that, there are many ways to skin a cat.

There are also guide lines on the speed and configuration in the airbus SOP's flying approaches.

Also, if the ATC gives you a heading to fly outside your flight plan (selected heading), how do you get back into following your flight plan exactly?
If ATC give you a heading to fly for a short time for separation, it will usually be followed by clearance to a point on the STAR. This can be achieved by using the DIR TO button on the FMGC. There are other ways too, by arming NAV mode (pushing the HDG knob) and using the radial in and out function.

When flying a STAR, and having it set up on the MCDU, the ATC now gives you radar vectors to intercept the Localizer.
While flying selected headings now, how exactly do you set the MCDU for this approach and cancel the STAR?
There are a number of ways to do this. Simply you can individually delete each way point on the STAR using the CLR key on the FMGC. Or, you could line select the centre fix of the runway on L2 this will then sequence the flight plan and automatically delete all the way points on the STAR. The other way you can do it, when you are in HDG, you could do a DIR TO the centre fix of the runway (NAV mode engages), then immediately pull HDG again, so then HDG is back on the FMA. This will in turn sequence the flight plan. It must be noted it is important to keep the flight plan sequenced, not only for accurate predictions, but when flying the approach to make sure the GA mode will be available.

Some of this stuff can be hard to understand without the simulator to play with. Of course it all comes with experience.

Hope this helps.
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