CDA Requirements - UK

[LOWI]

Many UK airports, especially in and around the London area (including LONDON... Luton).
They require CDA below a certain altitude.

Let's say 5000ft.
What conditions must be met for the CDA?
Minimum V/S? Is there a certain nm or time limit in level flight before busting the CDA?
Stupidly, does the CDA end at G/S capture or until touchdown?

[Gonzo]

Originally Posted by LOWI

Many UK airports, especially in and around the London area (including LONDON... Luton).
They require CDA below a certain altitude.

Let's say 5000ft.
What conditions must be met for the CDA?
Minimum V/S? Is there a certain nm or time limit in level flight before busting the CDA?
Stupidly, does the CDA end at G/S capture or until touchdown?

From Heathrow's noise website...

METRIC: When an aircraft arrives, it shall not fly a segment of
level flight longer than 2.5nm below 6800ft.
COMMENTS: YTD 24hr CDA Average for 2025 is 89.90%.

Ends at touchdown.

I believe the 2.5nm leg maximum level flight is standard across the London airports, but different airports measure from different altitudes.

[DaveReidUK]

In other words, you can level off for (roughly) 45 seconds at a time, but no longer, and still call it a CDA.

[Doug E Style]

Originally Posted by LOWI

Many UK airports, especially in and around the London area (including LONDON... Luton).
They require CDA below a certain altitude. Let's say 5000ft.

In practice it’ll be from the point at which they give you the distance to touchdown. It’s a bit tricky to gauge your required v/s for a CDA if you don’t know how far you are from touchdown.

[DaveReidUK]

Figures for CDA compliance from the performance stats for Heathrow's 50 busiest airlines in Oct-Dec 2025:

18 out of 50 airlines: >90% compliance (Green)
27 out of 50 airlines: 70-90% compliance (Amber)
5 out of 50 airlines: <70% compliance (Red)

Best performer for CDAs was Aegean Airlines, bottom placed (of the 50) was Air France.

No stats available for the other 30-40 airlines using LHR.