Continuous Descent Approaches
 

More and more airports now expect CDAs.

Given that you have FMS what advice/method do you employ to ensure a CDA on every occasion, flight safety permitting?

Thanks for any suggestions.

Make sure you know how to program YOUR FMS for the best performance! For example, if you know your FMS does not program speeds well during this type of descent, use manual override so the FMS can concentrate on the vertical path. If its VNAV is weak under those conditions, use V/S. If it works well using full VNAV, use it that way!

My trick:

Ensure that the route in the FMC is a good approximation of what you're expecting. Look at the landing time on the FMC. Look at current altitude. Work out appropriate constant rate of descent.

Works every time.;)

Spot on Rainboe....:ok:
I'm amazed that it tends to be the older "wizer" heads that seem to level off first;)

Thanks for the replies, guys.

Personally I enjoy the challenge of flying a CDA, very satisfying when it works out right!

"I'm amazed that it tends to be the older "wizer" heads that seem to level off first;)"

Is that because you are the only one still awake at that time Haughtney?;)

Once in the descent the FMC is for guidance only, theory to be backed up by practical experience of that particular approach, my 2cents, FWIW.

Can work out fine if ATC is interfering with your descent, just leaving it managed works fine and lasts a long time if ATC cooperates.

Perhaps time to remind all that there is NO minimum rate of descent for a CDA. If you need 300fpm, do it.

As soon as I get that base leg or final vector.....I us the V/S I want, as has also been stated, you get better with a bit of practise...as witnessed today by my Capt who remarked how good my effort was:E
(all I need now is to get the right result:p )

...................and a bit less of the older heads if you don't mind :)

I think any 'level' portion lines you up for the guillotine.

Constant Descent approach busted if ATC spot any level segment of>3nm below 6000ft.
[Why we can't fly idle at 330kts to 10nm, level and then close the thrust levers I don't know as that is quieter than -200ft/min just to tick the box :p maybe it's the extra noise generated by the subsequent go-around]

Can anyone point me in the direction of any official documents about CDA?

I find myself under increasing pressure from the company to observe these things as is everyone but for example I never heard it mentioned that you are allowed a 3nm level segment or a descent rate of 300 fpm. Where can I read the rules and regs?

Your company should provide this. There is no 'allowance' for a 3 ml level segment!! That is what will trigger a non-compliant approach. There should be a minimum level segment in the TMA.

Try continuous descent approach in Google - that will fill your day:)

It is now virtually a world-wide procedure.

This may help. I cannot instantly see the reference to 'any rate of descent' but in my experience there is no minimum in the TMA where CDA are 'required'.

League tables are published and we get letters if we don't comply but I have not seen any information on techniques or the rules of the game published. Which is disappointing as one of the big two of operators in STN.

There is in fact a publication in the UK that covers this: "Noise from Arriving Aircraft" published by NATS, BAA and others, which is primarily aimed at LHR, LGW and STN (but not RW05)

It does, on page 8, mention a 2.5NM level segment to decelerate (therefore the assumption is that thrust is at flight idle) before the descent commences. Furthermore there are very good tables on page 15 which give you V/S and FPA versus distance and altitude. These tables also mention the level segment - but assume 20secs of level flight at 210KIAS - one can only assume that the 2.5NM previously stated is a maximum (ICAO requires a minimum of 1.5NM)

I'm with Rainboe on the FMS/FMC/FMGC. On my type, it will schedule the next flap manoeuvring speed before you've wound 'em out which could be a tad embarrasing if you get distracted!

Why so little regard for CDAs? Because for many 'book' pilots, it is too difficult to do, if they cannot programme the FMC to do it for them! Too many have been told not to use VS because it does not include 'speed protection' and therefore will not use it, and the view of central London is better from 3-4000ft than it is from 5500ft!

Well said Rainboe.....its easy enough to muliply your G/S by 5 to get a required ROD for 3%, then the rest is just the 3 in 1 rule plus a bit to slow down:ok:

Doesn't happen all the time obviously because of ATC vectors away from the mental path you may have. The 300ft/mile is a good basic rule but for most aircraft I find this requires a "power on" descent given the majority of jet aircraft can descend around 1000ft every 3 miles on idle power.
I swear by gates. 8000ft/250kts downwind, 1200ft/min gets it slowing down and going down gently without having to use power to arrest descent. Gets a bit twitchy at times (especially in the bus with the well known balloon when selecting flap 2!) But like with majority of companies, ours doesn't offer any advice/practice on CDAs and therefore those gates mentioned above often scare the guy in the left seat. Not sure if this is because they don't have faith in me or prefer to keep it straight forward.

I guess just not the jets I fly:ok: 300ft/mile usually equates to 5 X the groundspeed:}