CDA's Liked or Not
 

Apart from the noise, enviromental issues and reported benefits to pilots.

Do you ever seem to find that pilots actually dont like them?

I think a lot depends on what one considers a CDA to be - last time I looked there was no consistently agreed definition and the published procedures that are nominally CDAs varied hugely.

Give the pilot an accurate estimate of track miles and, without putting them ludicrously high on the profile, let them get on with managing the approach.

What's to like or not like? It's not the optimum way for a jet to fly the approach but it's probably the best compromise at the moment when trying to move a lot of traffic.

.....he'll ignore the CDA and stuff the nose down.

It's all very well encouraging our people to use CDAs, but if the smartie tube drivers don't play ball, it's not going to work.

That's his problem not mine as I can't fly the aeroplane for him, or her.

At LHR where CDAs are the norm the compliance rate is very high. The most important thing for ATC to do is give the accurate track distance and update it if necessary then let the flightdeck manage the approach.

If it is obvious that CDAs are not being complied with then that's for someone else to take up with the crews, not me, I've already fulfilled my part of the bargain.

Personally I don't subscribe to the school of thought that says keep them as high as possible to the last second, or beyond, as all that is likely to do is lead to a bit of a rushed or unstable approach.

Good, accurate track miles and let the crew do their job.

But thats one of the issues, We are told that CDA's are a more economical way for the Jet to fly, giving track miles as you say and then intervening with speed control to help enable the compliance of a CDA is it really what crews like? or even variable on a/c type?

As you say sometimes it seems like they just want to stuff the nose down, and fly level for some time, yet ATC can be the ones judged afterwards with how compliant they have been, but as you say even MODE S not given us the ability to fly the a/c yet!

Although no published CDAs where I work, given the range from touchdown and to descend when ready, 2 out of 3 companies pilots will 'glide' the plane down. Whereas another company, given the same information, do indeed 'stuff the nose down'. CDAs have been talked about, although nothing yet, so we live and learn.

CDAs and speed control enable me to stick aeroplanes down the approach 2.5nm apart without too much apparent pain in the cockpit.

At the moment it's probably the best compromise for maximising the landing rate whilst fitting in with environmental and aircraft operational constraints.

Change the emphasis more to suit environmental restrictions or allowing individual aircraft to fly the approach their own most efficient way, all of which will no doubt be slightly different once company SOPs are factored in, then the landing rate will undoubtedly take a hit.

No skin off my nose, I don't mind doing wider sequencing.

Someone, somewhere does have to decide what we're trying to achieve though as you can't, imo, have your cake and eat it in this respect. You can have the greenest of green approach profiles and less traffic, let each flight do their own thing approach profile and less traffic or the slightly less green alternative of CDAs/speed control and maximise the the traffic flow, but not all at the same time.

As long as its safe, I suspect whichever results in the greatest commercial gain will win out irrespective of what individual pilots may or may not like.

Many times I try the CDA but ATC bugger it up!!

Try doing a CDA into London City when you have to be at FL80 by sandy which is a lot more than 24nm from touchdown.

Probably not a great example but going into Luton from the NW, trying to hit the Clippy level spot on only to get an early left and not via the lorel but a descent onto downwind for a tight base.

We need to know early.........and the lack on info often results in a ;

"if we descend early we may get a tight base" or "if we are lower they tend to giver a shortcut" or" this vector is taking us away, let's expedite down and perhaps get a better vector".

One aircraft I fly can not fly clean down the glide at 160 knots. Therefore we hang out eh gear. Unfortunately, the gear provides a little too much drag so we insrease the power.

The lack of aircraft type and poerformance knowledge problem identified over a decade ago has simply gotten worse overall.

Regards,

DFC

Actually it's everyone's problem. As an OJTI, it's hard to teach a trainee about CDAs when he/she sees pilots ignoring them. Similarly, as an LCE, it's just as hard getting the 'old dogs' to learn new tricks when we're the only one's making the effort. Granted, not all flight crews are the same, but it seems a bit daft for our company to go all 'CDA = environmentally friendly = good' if no one's telling the airlines to abide by it as well. Not all crews fly into Eefrow so they're not used to the concept.
Next thing we'll be told to file observations when a flight crew don't follow the CDA and we'll spend ever more time hunched over a computer doing paperwork.

Still, a wee claim for RSI would be nice.:E

Luton DownWind RH
 

'Many times I try the CDA but ATC bugger it up!!'
'Probably not a great example but going into Luton from the NW, trying to hit the Clippy level spot on only to get an early left and not via the lorel but a descent onto downwind for a tight base.'

Well I feel this is a little unfair to say... Luton Down wind RH are a courtesy, not a right! The STAR is via Lorel, adding at least 25-30 miles to your journey. The ATC sector you receive the vectors from for DWRH is one of the busiest, if not the busiest, in the London TMA. They give you the routing at or before clipy, this is, what, 40-45 miles notice that you will be getting a more expeditious route, and not doing the clipy, bombo, bky. busta, lorel gate route... DFC, would you prefer the standard route so you can perform your CDA, or would you rather travel 30 miles less?? Trust me, the STAR is a lot less work for ATC. To perform a downwind right, ATC must get you through LL wobuns, LC BPKs, Luton Olneys, SS Cpts, SS Buzads, basically every TMA departure to the North, as well as all the inbounds so we can get you to 5A/6A downwind the field.

Oh and in my humble opinion, a pilot that is briefed for this procedure is very often more capable, being a little bit lower at clipy, knowing this helps atc. Especially on 08, where the level restriction at Clipy is often too high to try and achieve FL60 at WCO, for a left base. This shortcut saves at least 50 miles, but if you ever watch it on radar, you get awfully close to the BNN hold. I've gotta say, easy pilots are very aware of this, and it is most appreciated, passing clipy well below FL150, which is the restriction.. Ryan's however... :rolleyes: CDA's are all well and good, but sometimes, you just gotta get your butts down becuase of the traffic situation :ugh:

Is there any truth that O'Leary's pilots are getting prizes for doing CDA's throughout the year??

Did you mean that? Speed control is absolutely essential to 2.5nm spacing, but why is CDA?

CDA is about the vertical profile of the arrival stream; spacing is about the relative lateral positions in the arrival stream - the latter is not dependent on the former. In fact, when aiming for tight spacing it is safer to suspend the CDA, establish vertical separation, turn in, and then resume descent. Having spent a number of months reviewing the Heathrow final approach incidents of the last 18 months, it is clear to me that if separation was given priority over CDA the serious encounters on final approach would be largly eradicated.

.4

DFC:

As far as I am aware, CDA's are not used inbound to London City due to the many altitude restrictions - That's why you can never get one ;)

(Someone please correct me if I am wrong...)

Defruiter you are correct, there are no CDAs in to LCY which is probably why DFC never gets the opportunity to fly one there.

.4 yes, I did mean what I said. CDAs and 2.5nm separation/spacing are quite compatible 90 plus percent of the time.

When I start TEAMing or otherwise using both runways then CDAs for the most part go out the window for at least some of the time as that's when vertical separation comes much more in to play.

Unfortunately crews in to LHR are so good at and used to doing CDAs that when you want good rates of descent for separation or otherwise want to manage the vertical profile it can be rather difficult to get the message across.

Agreed Roffa

And this is of course why the notion of doing mixed mode, turning in towards each other without vertical separation, using a single FIN (working his butt off on a saturated frequency) just so that the government can claim it is maintaining an environmentally sound policy is folly. The only safe way of doing it (under ICAO rules) removes CDA for one side of the approach.

.4

It seems also that the airspace, both amount, layout and vertical constraints of it play a big part in the ability to do CDA's, somewhere like EGLL and please dont take this the wrong way are probably easier to achieve than at somewhere else. In some ways having a continuous flow of traffic resulting in near permanent speed control make the application of CDA's easier, a quiter unit probably makes it harder, a single or largely spaced group of inbounds being vectored downwind, seems madness to suddenly give an a/c speedcontrol to make it slow its rate of descent just in order to achieve a CDA, yet actually make the flight longer.

Speed control is used purely for sequencing, it's not an intrinsic part of flying a CDA from an ATC point of view (imo). I don't reduce the speed of traffic in the hope of affecting its rate of descent, it's up to the pilot how he flies or configures to achieve the requested speed.

If there's one a/c inbound, or a group widely spaced, let them manage their own speed and just give them an accurate distance to go to allow them to manage the vertical profile for as far as is practicable to achieve a CDA.

I'd have to agree with radar rambler, to achieve a CDA the aircraft have to be reduced to 220kts. (isn't that in the definition somewhere?)
I've tried to get pilots to do a CDA at high speed and they almost always make a mess of it. It's all very well to say that's the pilot's problem but when it came to night time KPIs that excuse didn't wasn't accepted and the edict was reduce them to 220kts first, even if they're number 1.

DP, which airport says you have to reduce traffic to 220kts to achieve a CDA?

I don't recall seeing such an edict for LHR. Given that the night time KPI for LHR with reference to descent starts at 6,000ft, most a/c are likely to be 220kts or less by then anyway without any intervention from me. Keep traffic high as they approach 18 to 20nm from touchdown and all you get is requests on the r/t for descent...

We need to accept that we are not flying the aircraft, the pilot is. We can supply all the information the pilot requires to manage the approach and it's then up to the flight deck to do said managing. If I want I can slow an a/c up to 220kts, 180kts or even less spuriously thinking it will help a CDA be achieved but if they want to they can still dive down and fly level for miles.

a minor airfield to the south of you. i remember seeing it in a BAA leaflet explaining CDAs to pilots and ATCOs but we were verbally told to comply to help the KPIs.