Constant Descent Approach

[John Smith]

A number of airports in the Uk ask for CDA's but I can't find any ref to what actually is considered as a CDA.

I know your all going to say "keep a descent going" but what level is it below, what is the min ROD and is a decel no power accepable?

Thanks

[Giles Wembley-Hogg]

For operations into Heathrow, the Aerad chart page C3 states, "For monitoring purposes a descent will be deemed to have been continuous provided that no segment of level flight longer than 2.5nm occurs below 6000' and level flight is interpreted as any segment of flight having a height change of not more than 50' over a track distance of 2nm or more, as recorded in the aiport Noise and Track-keeping system."

Big brother is watching!! In fact the results for each quarter (I think) are published in our company newsletter. The results are broken down by fleet for our Big Airline and shown in comparison with our competitors.

Hope this helps.

G W-H

[BOAC]

JS - in the Londom TMA (at least) the min ROD of 500fpm is waived to help.

[Spitoon]

I think the reason for the lack of replies is that there isn't a common definiton. Different States (and sometimes different airports within a State) tend to develop procedures that suit their own operations. I recently heard presentations on the topic and one considered that a CDA started from 18,000ft!

[126.9]

Am I right in thinking (based on your posting) that your "Big Airline" compares CDA's with their competitors? It just sounds a bit hit-and-miss to me...?

:}

[Giles Wembley-Hogg]

126.9

My understanding is that BAA know from their monitoring equipment which flights didn't maintain a CDA and then work that out as a % of each carrier's flights. Since we know which of our flights are flown by which aircraft type, the data can then be broken down by fleet.

For example July 03 figures:

CDAs by competitors

Air France 71%
Cathay 63%
Lufthansa 69%
Virgin 91%
BMI 92%

CDAs by a Big Airline in the UK

319 94%
320 92%
734 93%
744 86%
752 93%
763 93%
772 91%
SSC (retd) 64%

I think Manchester have a similar monitoring programme looking at the accuracy with which the SIDs are flown.

All the best

G W-H

[Flightman]

Giles,

We do indeed know what flights have performed a CDA, and which haven't. We are also advised by NATS when ATC have given the pilot incorrect descent information, and remove those from the stats.

The criteria used at LHR are the ones posted above, below 6000ft, +-50ft, 2.5Nm's etc etc.

Oh, and we also monitor track keeping as well, so can you guys please try to fly 09RCPT properly please? :D It would make my life so much easier! Its currently below 35%! And if anyone can explain why CPT is so difficult to fly, I'd appreciate it!

Ta

[Mike Rosewhich]

Flightman,

I await to be corrected but many departures that were planed as CPT’s end up being amended before departure ie, at LON 2 DME turn left HDG 2XX degrees.

That may explain it.

MR

[Flightman]

Mike,

You may well be right, although that descriptions a bit too techie for me at the moment!

However, that doesnt explain why all our departure routes, except CPT are above 90%, and CPT is 1/3 of that at best? Is it anything to do with airspace issues? ie inbounds from BIGGIN stack?

[HEATHROW DIRECTOR]

<<We are also advised by NATS when ATC have given the pilot incorrect descent information>>

Er... I think that was badly phrased as pilots are never intentionally given "incorrect descent information". I know that controllers are (or were) supposed to report when they "break" noise abatement rules but this is not "wrong information" even though it may be considered as such by Big Brother at BAA. Traffic is handled with several priorities - safety first and noise abatement somewhere behind.. Landing on 2 runways early in the morning CDAs are nigh-on impossible to achieve... if that's what was meant.

CPT SIDs off 09R are released subject to the Heathrow South Director (134.97). It's his task to climb the outbound against the downwind stream for 09L so he issues a radar heading, which is passed by Heathrow Tower immediately before departure. Depending on many factors the Director may do this by climbing up the "inside" (between the downwind stream and the airport) or the "outside"... which can mean going out over Blackbushe. The track on which you end up will be a radar heading and can be many miles off the SID.

[Giles Wembley-Hogg]

Flightman

You may as well forget looking at the track keeping on the CPT SIDs off the 09s, because as HEATHROW DIRECTOR and Mike have already stated - they are simply not flown. In fact I am surprised that 1/3 of the headings dreamt up by LL INT SOUTH actually cause the aircraft to follow the SID path! (Not meant in a bad way - just goes to show that the theory of big numbers works).

When do you stop monitoring departures. Is it after they have passed the SID stop altitude (6000'), after they have passed a particular geographical location on the SID or after they have passed 4000' and noise abatement is no longer required?

G W-H

[Flightman]

HD,
Sorry, your correct, that was badly phrased. What I meant to say was we get a list every week of aircraft that didnt fly.

Eg: "XXXXXX hospital flight, all KPI's busted".

We then remove flight X from the stats. I should say that this is maybe 1 or 2 flights a week.

Giles, track keeping is monitored upto 4000ft. The system overlays the flight track onto the departure swathe, if it crosses the boundary below 4000ft, its offtrack, 4000ft and above, its ontrack.