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CDA/OPD issues

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CDA/OPD issues


Old 24th Sep 2012, 15:38
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CDA/OPD issues

I found this report on CDA and the FAA. I am curious about the reference to the "safety and noise risks discovered overseas".

"The FAA wanted to implement Continuous Descent Approach (CDA) at La Guardia as part of the Regional Airspace Redesign to reduce the noise impact when they terminalized a much larger area. In the Draft Environmental Impact Study (DEIS) CDA was included however CDA failed the safety field test in the summer of 2007 and was not included in the Final Impact Study(FEIS).

Nonetheless the Port Authority, commercial airlines and certain members of congress continued to push CDA as the preferred solution to jet engine noise to make use of the associated efficinecies. Due to this pressure by congress and the industry the FAA chose to include CDA in the latest implementation schedule for all the New York New Jersey airports even though it failed the safety test.
The FAA decided to rebrand CDA due to the safety and noise risks discovered oversease and in litigation so they changed the name of the procedure from “Continuous Descent Approach” to “Optimized Profile Descent” (OPD)."

OurAirspace: CDA or OPD

I have not heard of any issues with CDA overseas that would determine a failed safety case, noise, or litigation issues.
Can someone help out with this, or point me in a direction to look into this?

Last edited by FlightPathOBN; 24th Sep 2012 at 18:42.
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Old 25th Sep 2012, 05:10
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Hi Flightpath,

I saw your post yesterday but didn't comment because it really boggles me as to why the FAA finds a CDA unsafe and had nothing to answer to that.

I guess that's the reason why there aren't any replies to this thread yet!

But thanks for the info anyway
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Old 25th Sep 2012, 05:28
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I'd be interested in knowing more about how the "safety field test" was conducted and what specific problems were noted. I wouldn't be too surprised if any problems found were related to airspace and potential traffic conflicts with the other NYC area airports. Other high traffic count airports within a few minutes flying time of LGA include JFK, EWR, TEB and FMG. Finding a way to incorporate CDAs into this airspace must be challenging to say the least. However, simply stating that the idea failed a field safety test back in '07 is a rather lame explanation!


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Old 25th Sep 2012, 13:50
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I don't see the issue at LGA. Three of the runways have ILS, the fourth has a LOC. But, visuals are typically flown to that runway (31).
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Old 25th Sep 2012, 14:42
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Gatwick expects CDAs from arriving aircraft but this info does not appear in the Jepps.
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Old 25th Sep 2012, 15:49
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I can see there are potential for issues with all of the crossing paths from different airports at LGA, but that is a design issue, not a safety case issue.

There was a reference to stall, but I dont know who dreamed that up as an issue with CDA.

I cannot find any references regarding safety or incident with CDA overseas....especially enough to warrant changing the name from CDA to OPD.

Thanks for all of the replies...
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Old 26th Sep 2012, 16:48
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I did note the article as having many incorrect assumption, OPD/CDA will keep the ac higher longer, and ideally, will use a 3 degree GPA from TOD, keeping the ac higher than the step downs.

My question was regarding the validity of the failed safety case, and issues overseas....

You seem to be saying that there is a difference between CDA and OPD....

Isnt OPD just the newer nomenclature under NextGen?

Last edited by FlightPathOBN; 26th Sep 2012 at 16:52.
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Old 26th Sep 2012, 18:46
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Nice reply, thanks for that.

Idle descent to threshold has been oversold to save fuel, and now lower noise, but it just doesnt work in a multi, or even single variant queue.
I am much more in favor of a controlled descent, especially below 5000 feet. This allows ATC to manage the queue, and tighten up the spacing, if everyone is one the same page. At 3 degree GPA, it is not a whole lot of throttle to go 160 kts.
With a waypoint a speed restriction at 10,000 feet, this provides an adequate 'target' for the box to identify, and pull TOD accordingly. If we need to fix TOD, then idle down to FL10 is still workable, and saves the most fuel.
Other target waypoints at 5000 and 3000 provide the ability to optimize the queue in a multi-variant environment. (the checkride 240 at FL 10 that Boeing has coded in is certainly annoying)

I will be watching the trials of this RNP procedure very closely....
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