Continuous descent approaches

[bullshot]

Hope that you guys won't mind me asking a question re the above..

We pilots (well most of us anyway) always try to accomplish CDA's having been given good info from yourselves. Naturally we don't always get it right but on those occasions when we do manage to make it fit perfectly it adds to job satisfaction.

I gather that there is an 'table' emerging of those Airlines who have the most success at accomplishing them. This would mean that you folks must score them in some way - if so, how do you do it? Is recourse to level flight at all written down as a 'failure'? - even if it is only for 1 mile with the thrust levers closed whilst slowing down? Or what about the times when, realizing you are a little low on the descent, the vs is reduced to, say , as little as 300ft/min when approaching the cleared alt?

Just wondered how you do it. By the way, a 15min stoppage to expose those executive director 'gentlemen' who abuse their positions of power is a great idea and I am sure would not be taken the wrong way by your customers.

Best regards- talk to you later!

[HEATHROW DIRECTOR]

It's not us - if you're referring to ATC. It's the airport authority! The same system they use to determine how many of you guys are flying CDAs they use to bollock us for turning you on at 9.999 miles from touchdown when it should be 10 miles from touchdown during the night hours. We don't mind if you make the CDA or not but the loonies who live for noise abatement take it all far, far too seriously and get terribly excited if you don't!

[Duke of Burgundy]

bullshot - you seem to be under a misapprehension about what counts as a successful CDA. Perhaps a definition might help.

An arrival is classified as a CDA if it contains at and below an altitude of 6000ft no level flight, or, one phase of level flight not longer than 2.5nm.

Level flight is interpreted as any segment of flight having a height change of not more than 50ft over a track distance of 2nm or more as measured by the airport`s Noise and Track Keeping monitoring system.

Also, when below the Transition Altitude there is no requirement to inform ATC if your descent rate either is or will be less than 500 fpm.

Hope this helps.

DoB

[HEATHROW DIRECTOR]

Hi Duke.. you said: "Also, when below the Transition Altitude there is no requirement to inform ATC if your descent rate either is or will be less than 500 fpm."

I've seen you write this elsewhere and I'm curious to know what sort of bee there is in your bonnet about this? Personally I would be very, very grateful if pilots would tell me about dramatic changes to their descent rate below the TA as I have had more than one very serious fright caused by crews levelling off at intermediate altitudes for totally inexplicable reasons. Typically, I was descending an inbound onto one of Heathrow's westerly approaches from LAM and at the same time descending a Northolt inbound heading north off Biggin. I desperately needed levels so asked the Heathrow guy to report passing 5000 ft, which he did. I then cleared the Northolt traffic down to 5000 ft... but the Heathrow guy stopped his descent at around 4700 ft, causing a lot of laundry for me later. If he had told me that he was going to reduce his descent rate it would have prevented a nasty incident. Remember that old and long forgotten word "Airmanship"?

[bullshot]

Thanks chaps - I had no idea of the exact definition of a CDA or indeed what constituted level flight in this context. This info may be buried away in the UK AIP but as far as I am aware is not contained in my company's flight guide (jeppesen).

Ideally, a CDA should be flown at a reasonably constant descent rate, although this will reduce as aircraft groundspeed reduces. Descent from initial CDA altitude is started at a time the pilot judges best with that in mind. In practise, at my home A/F (LGW) the controllers do this for us by giving the clearance to descend at the point for a 3deg (300ft/nm) descent angle. I should say that I always took it that descent rate (in this context) having been cleared, was up to me - even if it involved less than 500ft/min. An intermediate level-off should not be necessary, the most likely cause for this would probably be when a pilot, having initiated the descent, then engaged a profile or VNAV pitch mode. If then the A/C was significantly below the FMC computed descent profile it might level off in an attempt to regain it. Using FMC generated descent paths for CDA's is not normally a sensible option in a radar environment because the FMC may not have the accurate horizontal tracks required to calculate the descent. Good old fashioned mental arithmetic usually works better! Alternatively, and I find this to sometimes be the case, the controller 'finds' some extra track miles during the descent - so 25 miles from FL80 becomes, say, 29. This might require a reduction in vertical speed when the pilot cottons on, but I would not imagine a level-off. Interesting that you feel it is Airmanship to inform the controller in such a case though, and I will take this on board.

Just out of interest, can you guys 'sense' a competent (incompetent?!) pilot simply from his/her 'radar ' behaviour and from what you hear? I am not sure if you will know what I am getting at, but I reckon I can 'sense' a competent controller (as, I know you all are!). Over to you.

Best Regards

[Duke of Burgundy]

Hello HD - I don`t have a particular bee in my bonnet, but the reason I have mentioned it several times is that it was slipped into the AIP just over a year ago in terms which did not make obvious the implications and I feel the need to inform anybody who is interested.

I`m sorry you had a fright but whether you like it or not this is what a pilot is permitted do now and it is clearly a trap into which we all could fall.

Kindest regards

DoB