Continuous Descent Approaches

[Chilli Monster]

Originally Posted by Rainboe

What are the implications of non compliance?

Possibly dropping out of the bottom of Controlled Airspace.

Are 'league tables' kept?

Yes

Is enough attention being paid to it?

Probably when the chief pilot gets a letter comparing their (lack of) CDA compliance compared with other airlines.

I fly with pilots who appear to be surprised when I insist a CDA is flown at these airports, even at anti-social hours.

I don't understand their thinking - they're more important during anti-social hours.

Unfortunately it seems to be a nicety that is simply ignored, or conveniently forgotten when tired or weather is not ideal.

Not an excuse - if it's detailed in the respective airports AIP entry then you should be flying it (or attempting to fly it) unless instructed otherwise.

Indeed it seems many are simply unaware of the requirement.

I think there are enough people in the industry who are aware of the concept, understand the concept and know where they should be doing it. Non-compliance, in a small group of pilots is possibly down to "bloody mindedness". (I've always done it this way, don't see why I should change for a bunch of tree huggers).

So how strict is the requirement?

In the same way that aircraft that operate to high noise in unsocial hours can attract financial penalties there's no reason why, with the equipment available for monitoring, that fines couldn't be introduced for repeat offenders. We're not at that stage yet however.

Is it felt there is a lot of room for improvement?

I think that people are starting to get the message, albeit slowly. What I'd like to know is - when did pilots stop being able to do simple maths?

CDA's aren't rocket science. 6000ft = 20 miles (18 plus 2 to start the process). ROD = 5 x groundspeed.

I've seen ROD's double what's required. (250Kts = 2500fpm - nice one NOT!). That means you get stopped off (to keep you inside CAS), you burn more fuel, and your compliance goes out the window.

You're going to have to manage it when P-RNAV comes in, so you'd better get with the programme now people.

[fireflybob]

As usual Chilli Monster is 100% correct!

It's like anything, if you practise it everyday it becomes very straightforward.

Just to add a little balance there are, of course, certain occasions where a CDA is not possible - eg aircraft malfunction (engine out).

[Musket90]

CDA's at Stansted are only possible on runway 23. On 05 the approach procedures are too restrictive to manage it.

Regarding displacing landing thresholds on Heathrow's 27s, this would be very costly - new approach lights, new TDZs etc, some of the existing runway exit points may end up in the "wrong" place increasing runway occupancy times and therefore affecting capacity. Probably would need to build extra exits. Other issues are obstacle surfaces, public safety zone contours moving etc.

[pheighdough]

CDAs

I agree with all that has been said on this post so far, but I can update you on where CDAs are either in force, or will be coming soon.
Currently Heathrow, Gatwick, Stansted, Luton, Bristol,Cardiff, Manchester (but only at night, when will they go H24), Birmingham (just starting night time only), Newcastle
Soon to follow are hopefully Edinburgh, Glasgow, Aberdeen, Southampton (albeit may be runway specific), Belfast Aldergrove, Liverpool, Doncaster
For information CDAs should be attempted at all times and the London airports all have monitoring that send reports to ATC for performance reporting amongst the watches.
The Arrivals Code of Practice can be found at: http://www.dft.gov.uk/pgr/aviation/e...odeofpractice/
You may also be interested in this for a European view: http://www.eurocontrol.int/environme...20brochure.pdf

[Chilli Monster]

You missed out East Midlands - CDA's required H24 and have been a normal operating procedure for at least 2 years.

[duece19]

Chili...
There are multiple things that can make life less easy whilst conducting a CDA.
Firstly, the airplane needs slowed down, depending on type this could be quite difficult whilst trying to descend to maintain a proper profile.
If one has got a bit of tailwind and are anticipating a tight turn to final the one more than likely wants to get a tad lower than normal in order to ensure sufficient space for speedreduction and still maintain a proper path. It isnt always that easy to figure out when a turn to base will be given or when you will be given a instruction to reduce speed (trying to catch up a 3 degree path at whilst decelerating to 180 is hard).

Trackmiles to touchdown is given in most cases but that could be at 30 miles out whilst on downwind and keeping a perfect 3 degree glidepath whilst taking in to account where and when you will be given instructions to reduce speed can indeed seem like rocketsience at times.

Sure 6x3 is 18, I think we can do the maths, but there is more to flying a CDA than the 3 times table. If one was given no speedcontrol and speed did not matter then I dare say anyone could end up at 10nm around 3000ft every time.

Having said that, there is no excuse for not trying if the conditions are suitable which they may not always be.
The bunch I work for seem to have a fairly good level of compliance at STN and LTN, close to 95% I´m led to believe so surely it can be done, but it just isnt so easy as you think.

When it comes to PRNAV arrival I believe the track from the stack to FAF is published and loaded in to the FMC which indeed makes a CDA simple to fly, so I wouldnt worry about "getting with the programme"
duece

[pheighdough]

Sorry

Chilli
Sorry I missed out East Midlands not intentional. Of course you were the trial airport for the Silent Aircraft Initative.
Your ever humble servant
pheighdough

[Roffa]

Perhaps the ideal world would be as per the Stockholm "Advanced-CDA" concept - information halfway through this presentation. The trials seem to have been very positive:

Interesting, I look forward to seeing the trial of long periods of consistent 2.5nm spacing and advanced CDAs.

[PPRuNeUser0178]

Chilli,
At STN, the only place I fly to on a regular enough basis for comparison, the track miles given by ATC on a fairly common basis do not match what you actually end up flying.
A comparison of achieving a radar vectored CDA and a PRNAV CDA are like comparing apples with oranges. On a PRNAV approach it is flown from OUR database, with OUR programming and in exact compliance with the published procedure.
In contrast rarely are two radar vectored approaches the same and base leg, speed reduction are at the CONTROLLERS behest, something we are constantly trying to guess when we are over 3000ft high on the profile that WOULD achieve a CDA if we were left alone to fly it.
Then there is the odd occassion of being "forgot about", flying a perfect CDA and just waiting for the closing heading to be given when the controller has a laugh with an old buddy or a VFR calls up giving it bla bla bla and you sail straight through the LOC to be eventually brought back on in LEVEL flight from the other side, apology from ATC and a non-compliance stat for me, oh good!
I honestly think more ATC guys need to spend more time on the flight deck, the classic up here from Scottish is reduce your speed now to 250 or 220 kts and be level at FL70 by TARTN, this shows no understanding of how a jet aircraft flies.
Sorry rant over, but sometimes there is two sides to a story!
ED

[Chilli Monster]

ezydriver - there are certain places also where the track miles you get are the track miles you fly.

I do sympathise though - if you don't get the right distance how can you be expected to fly a CDA. Have you thrown this at your base captain for onward transmission to ATC?

[Bearcat]

Re CDA's UK....May I say the ATC authorites do not hammer home enough the importance of CDA's and just send out who's the best who's the worst p/m.

Continuous reminders and maybe fines for those who go way below the profile??? unless they have damn good excuses???

[ebenezer]

Pheighdough - CDAs have been in use at Luton (albeit only on Runway 26 and from 5000 ft) for 10 years. Since the introduction of more recent additional controlled airspace they've been in use for both runways but again, only from 5000 feet owing to complex route interactions with some other London TMA airports.


You mention Southampton as a likely near-term future location - how will this be achieved onto its northerly runway for arrivals from the north, given the current controlled airspace limitations?


More generally, CDA compliance in the UK is monitored, tracked and collated not because "ATC" wishes necessarily to police adherence, but because most airports nowadays are required to submit reports on this issue to their airport consultative committees and/or noise and track-keeping committees on which local councils, amenity groups and environmental activist groups are all heavily represented.

[Flightman]

And there's me thinking CDA's were flown at LHR/LGW/STN etc because its in the AIP.

We report the compliance figures at those groups, but they're not flown because of them. As Pheighdough said earlier, airlines love CDA because it saves money, airports like it because it makes for a quieter approach.

[Right Way Up]

My company are very pro CDAs and have a good record at LGW. I cannot remember the last time I did not achieve one and personally try to fly one at every other airfield I fly to. With experience they tend to become second nature. However there is a huge difference between me flying multi sectors into my home base and the poor so and so flying their one sector transatlantic into an unfamiliar field. To fine them would be unfair. One thing that does need sorting out though is being cleared for the approach. Quite often we get cleared to intercept the localiser at 3000ft with loc capture and glideslope capture being instaneous. We then get the full G-ABCD position report and we have to fly level until we can get further clearance. The situation then requires the slightly ungainly g/s from above capture which if not slickly done can lead to an unstable approach. I understand why the existing system is in place, however if the authority wants CDA compliance they have to start giving us the tools to do it safely. Some controllers will give descend 3000', further with the glide, others will not! Why?

[CAP493]

...is it time for ATC to draw pilots' attention (at quieter times) to non-compliance? Even perhaps advising decibel readings when 'extraordinary'?

Your first suggestion isn't a good idea because if this became SOP, then you can bet that if ATC forgot and the flight crew failed to comply, your airline employer would blame ATC's failure to inform the flight crew. As for your second suggestion, ATC doesn't have this information ~ it's monitored by the airport authority and is an issue that is taken up by them with the operator concerned. However, including a reminder on the ATIS sounds like something that's definitely worth considering. As regards night-time 'straight-ins' - from an environmental perspective, reducing track mileage and thus fuel burn shouldn't be an excuse to 'bin' CDAs at night. Of course, therein lies the environmentalists' dilemma...

[CAP493]

By allowing lower altitudes, the aeroplane can stay cleaner longer, flying faster but slightly lower and at idle power, and slow up at about 4000' to extend flap all the way quickly for final descent. I believe this is quicker and quieter.

That's most interesting, Rainboe...

Altitude 6000ft at 20nm would - depending the airfield elevation - be considered by ATC as being precisely 'in the groove' (obviously, for FL80 at range 25nm it depends on the QNH as to whether this is above or below the optimum altitude 7500ft).

Thus, if one takes your argument as being valid (and I've no reson to suppose it isn't as you're the one who drives the aeroplane!) then the logic that's been long advanced for the CDA concept becomes really rather questionable.

Are you also implying that 'free speed' is necessary to achieve what you've described? Clearly, at busier times this wouldn't be possible - at least not in a TMA environment.

[duece19]

CAP...

as rainboe states, being kept on the 3 degree path whilst maintaining free speed makes it hard to keep a cda without throwing out extra drag...

At about 25nm the altitude window in which u need to be to perform a CDA without dangerous manouvers is quite big, one has some more time to use the drag avail or even stay at a higher speed if approved. The window shrinks with decreasing trackmiles and it makes the "job" more exact and requires more attention.

By no means free speed is neccesary to maintain a CDA however one could argue wich method thats actually quietest and most environmentally friendly. I am with Rainboe here that being able to maintain a higher descentspeed with thrust idle ofcourse until about 18-12 nm and then reduce in a shallow descent would be most desirable but ofcourse this is not possible when other traffic is around.

Even a short levelsegment with thrustidle does not increase noise or fuelburn and unfortunatley this is needed sometimes when one gets the descentplanning wrong.

I think most guys prefer to get just a tad below the optimum 3 degree profile whilst manouvering out with flaps up since depending on type a good few nm is required to slow the airplane down. Once you are being slowed down to say 180kts and have flaps extended provided you are on profile, it is not a problem being kept slightly "high" since you have already got rid of alot of energy.

There is a lot to it especially when I try to put it in writing like this, but famflights is the way forward (and visits to approach units ofcourse)

cheerio

duece

[CAP493]

There is a lot to it especially when I try to put it in writing like this...

Thanks duece19, although I leave the flying to my wife (probably safer that way...) I certainly get your drift. What's interesting is that CDAs are being "sold" by the DfT, CAA, Eurocontrol et al to the politicians and to the general public as the panacea for reducing noise from inbound aircraft, and the ATC world has no option but to sign up (as does the flight deck fraternity). From what you and Rainboe appear to be saying, CDAs whilst useful, can actually cause more noise than is necessary, and that a slight tweaking of the descent profile can actually ease this even though you're not actually following a three deg descent all the way from the intermediate descent point.


Makes one wonder just why pilots/operators are monitored for adherence to, and controllers are trained to provide and are criticised when they don't provide, CDAs...

[pheighdough]

This thread appears to be coming to the end, so I thought I'd add my bits to it too. The "theorectical" profile is 3 degrees, but looking at the definition in the UK CoP as well as the recently published Eurocontrol Guidance, aircraft can descend at a shallower angle, provided they do not exceed the level flight limitations.

A330-200s are descending at a shallower rate, at their request, as they have a problem losing speed and height. 20nm at 6000ft is spot on for ATC to facilitate CDAs, the A330-200s prefer 24nm at 6000ft.

As for the noise, the ERCD guidance points to an aircaft in a continual descent 'dirty' is quiter than an aircraft in level flight bleeding the speed off, albe it in a cleaner configuration. I'm still not convinced...

[Doversole]

What is really required is low noise approaches, using low power and low drag. Unfortunately it is very difficult to monitor whether an aircraft is at flight idle with the minimum of drag. Consequently CDAs which are easier to define and monitor are a good second best, so that’s what we’re stuck with. To make them work requires a partnership between controller and pilot. Sometimes that works really well, sometimes not so well, but at least they are both trying. With practice and experience, CDA performance gets better. The problem is that there are operators and pilots who haven’t latched on yet, for whatever reason, that the world is changing. They are the enemy because when we are accused of doing nothing to reduce noise or emissions, they are not. We, as an industry must try harder and when everyone flies CDAs as a habit, it might even be possible to introduce low noise approaches.