Emergency Descent and 7700

[je.f]

I teach A320 Type rating . Up until now , I have suggested that during an Emergency Descent Pilots might think about setting squawk 7700 pdq if for no other reason than to alert ATC in lower sectors that an aircraft is about to plummet into their airspace (Altitude filter otherwise active ) . Someone has now suggested to me that this is unnecessary as ( in the UK , at least ) (i) ATC Software notices the rapid change in Altitude and alerts everyone accordingly and/or (ii) Upper level controllers can Flag a radar return with an Emergency code , which then makes the aircraft visible to all .
So : some questions for you controllers
1. Has what I have been suggesting ever been the case ( squawk A7700 for lower level conspicuity , or was this a figment of my imagination ?
2. If it ever was a good idea , is it now ( over UK) ?
3. Would the same answer to 2 apply over Maastrict; Rome ;Turkey ? (etc etc)

[Turn It Off]

I would suggest that 7700 would be a good idea.

At the unit I work, we work a bit of Londons Airspace and we wouldn't get any of their emergency flags transferred onto our system, and, if they are busy moving things out of the way, we might not get too fast a phone call!

I would suggest setting the A7700 then we will have you flashing (ooo errrr) on our screen, a message on our screen saying special code and our attention would be drawn to you giving us as much notice as possible, if both things happen, then its even better IMO.

Maybe as emergency descents are so rapid they could warrant their own SSR code?

TIO

[MancBoy]

Certainly on NATS systems the computer doesn't recognise a rapid rate of descent as an emergency, so I would also suggest slapping on 7700 quick as

[anotherthing]

je.f

If at all possible, then squawk 7700. An emergency descent is probably one of the very minute number of emergencies though whose 'Immediate Actions' makes setting the squawk immediately fairly difficult.

I personally would like to see 7700 for every emergency, even medical PANS etc, because it does alert other people to the fact that there is something going on.... and if nothing else, it may prevent the controller concerned being called on the telephone for something less important thus taking away their attention momentarily.

I can't think of any radar system that interperets a fast descent as an emergency..... if that was the case, the military jets that are in abundance all over the place would be forever triggering it!!

[Radar]

je.f
Just for unanimity's sake, we (Maastricht) will always appreciate 7700 ASAP under those circumstances. There's no faster way of getting the controller's attention, the correlation is maintained (ie. we still have your data block, CS, FL etc.), your track symbol is forced for display regardless of layer settings in all sectors and our colleagues in Amsterdam, Bremen, Langen etc. have a visual as well. Cuts down on the time required for the required co-ordination.
All in all an excellent idea. So, je.f. keep doing it like you've always done it!

[begbie]

I think that squawking 7700 during a rapid descent is an excellent idea. It alerts all surrounding sectors in the quickest way possible, and in the case of the sectors below, allows them to move any conflicting traffic asap..
Bear in mind that the sector you are talking to and the sector you are dropping into may be 70 miles apart at different units..

[je.f]

Thanks for the responses : the consensus seems to be that 7700 to alert lower airspace is a good idea . ( Although more opinion is always welcome )
So here is a supplementary .
I have also suggested that in a radar environment - everyone on Headings or Direct To's rather than on airway centrelines - an automatic turn away from present heading might do more harm than good : who knows where anyone else is . On the other hand an immediate "MAYDAY MAYDAY MAYDAY <callsign> Emergecy Descent , Request Heading" might be a useful aid to avoid smacking into someone else .
( Also , TCAS to TA only - and BELOW - might assist , although pilots should all be aware of the dangers of basing Collision Avoidance Heading changes on TCAS returns , as explained in a recent Eurocontrol ACAS Bulletin : http://www.eurocontrol.int/msa/galle...n_6_Mar-05.pdf
Are these useful too , or do they make it worse

[anotherthing]

My tuppence worth in response to your last post - only turn off current heading if on a runway centreline, it's an established procedure, any other supplements to that may cause us poor ATCOs confusion.

I would not bother with the "request heading" in the mayday call.... if you manage to squawk 7700, other sectors will see it and will coupled with the fact that they will see you descending rapidly, they will move their A/C out of the way if needs be.... on top of that, the controller you are in contact with should automatically be looking for some clear airspace as soon as they hear the words "emergency descent".

In the first few seconds of the emergency, the ATCO will get a bit of an adrenaline rush (though not as much as you!), and the 'request heading' may confuse them into thinking that you want directions to a specific point etc etc and may cause them to question you - the last thing you need!!

In busy airspace with a huge rate of descent,I would be very wary of TCAS - it is there, as always, as a last resort. TCAS can be extremely unreliable in azimuth and should never be used by pilots in this way, apart from when trying to acquire visual contact when you get a TA. Even then, caution must be used - you may become 'visual' with the wrong A/C!!

Pilots have, in the past, caused losses of separation because they did not believe the ATCO, whose traffic info seemed at odds with the TCAS display. The pilots subsequently caused erosions of separation, when in fact, the azimuth interpretation was wrong!!

[055166k]

je.f

At London ACC Swanwick your mode C height readout disappears completely from the SSR label during high rates of descent. I might not see the rapid descent rate, and I would be left with a callsign label and no visual cue to any problem. I think a "fix" is under way after years of asking. A 7700 will draw my attention....and everyone elses. It stops other units and sectors calling me because they know I'm busy.
As a side note it is worth mentioning that the labels of military aircraft with a high rate of climb and descent, and which operate in close vertical proximity to civil traffic, are likewise affected.
I'm only a controller, so I assume the iron brain thinks "gosh! that can't be right.....I'll switch that off"
Imagine you are over southern England at high level; below you may be several layers of airspace with each level banding group controlled by a different sector or agency......select 7700 and everyone is alerted simultaneously. Official "book" answers may differ.....I only know what works best in real life.

[78deg]

Special Procedures for In-Flight Contingencies Europe
Special Procedures for In-Flight Contingencies Europe
Ref ICAO DOC 7030 - Proposal EUR/NAT-S 01/29 - EUR RAC/11 approved T13/4.E - RQ - L03-0104.ATM
EMERGENCY DESCENT PROCEDURES
ACTION BY PILOT-IN-COMMAND
1.When an aircraft operated as a controlled flight experiences sudden decompression or a (similar) malfunction requiring an emergency descent, the aircraft shall, if able:
a.Initiate a turn away from the assigned route or track before commencing the emergency descent;
b.advise the appropriate air traffic control unit as soon as possible of the emergency descent;
c.Set transponder Code to 7700 and select the Emergency Mode on the automatic dependent surveillance/controller-pilot data link communications (ADS/CPDLC) system, if applicable;
d.turn on exterior lights;
e.watch for conflicting traffic both visually and by reference to ACAS (if equipped), and
f.coordinate its further intentions with the appropriate ATC unit.
2.The aircraft shall not descend below the lowest published minimum altitude which will provide a minimum vertical clearance of 300m (1000ft) or in designated mountainous terrain 600m (2000ft) above all obstacles located in the area specified.

[Hold West]

From the US perspective, I pretty much agree with everything stated above.

Squawk 7700, don't turn off heading, direct, or whatever airway you are on. I teach folks to NOT mess with the emergency, but crank other aircraft who are not so... er, distracted, out of the way.

[yarrayarra]

78deg

78 deg pretty well covers what we would expect here in Oz too.
Another reason given to me by pilots for the turn 90 degrees to the airway was that it's quicker and more comfortable to get the nose down and maintain positive 'G' while in the turn than a straight pushover.

[BDiONU]

Originally Posted by 055166k

At London ACC Swanwick your mode C height readout disappears completely from the SSR label during high rates of descent. I might not see the rapid descent rate, and I would be left with a callsign label and no visual cue to any problem. I think a "fix" is under way after years of asking.

NATS’ radars are optimised to record changes of height of up to 1,000ft/scan. Any ROC/D above this rate will be marked as invalid and will not be displayed by any RDP system. Scan rates vary between 10 seconds per scan for a 6 RPM radar and 4 seconds per scan for a 15 RPM radar. This equates to an ability to track a climb/descent of between 6,000 and 15,000 fpm.
NATS’ radars turn at different rates so in order to prevent the application of different rates in different parts of UK airspace, an average scan rate has been adopted. The average scan rate of 7.5 secs/scan therefore equates to a ROC/D of 8,000ft/min.
The design parameters of STCA include the ability to track ROC/D up to 11,000ft/min. However STCA is dependant on the data rates received from the sensors and so the 8,000ft/min average becomes the limiting factor in STCA performance.
As a consequence of these limitations until such time as changes are made to both ground RDP systems and ground/airborne safety nets, all aircraft operating within UK controlled airspace will be restricted to a maximum ROC/D of 8,000ft/min. The restriction is effective AIRAC 7/2007 on 5 July 2007. It will be promulgated by AIC, with a subsequent AIP amendment in ENR 1-1-3-1 Para 2.2.1.

BD

[je.f]

Again , thanks for the responses

anotherthing

I appreciate that a 'request heading' call might be misinterpreted . However , I would imagine that at this stage of the event , 'where to go' might not necessarily be the top priority to the Pilots : once the descent is well under way , however , some information gathering and analysis might be required ; and from this will come a decision as to whether to an immediate landing is actually needed or not . For Air supply or Pressurisation Control problems - or for damage confirmed to be minor - a crew may elect to continue to destination ( fuel , MSA permitting etc etc ).

( Many years ago we had a suddenly crazed windscreen at FL370 on the way somewhere . Once the ED was complete at FL100 , we got the books out and discovered that the layer that had failed was not , apparently , critical to strength and that there was no restiction on Pressurisation load . We rather sheepishly climbed back up to FL370 for the rest of the Flight )

However , I can see how 'Request Heading' might be taken as a request for a vector to an Enroute . How about 'Request Heading for Separation' instead . If nothing else , it tells the Controller that the descending aircraft is able to take a vector if this is the simplest solution to ( multiple) Collision Avoidance .


78deg :

The extract from ICAO 7030 - which I must admit I am not familiar with - has the word 'proposal' in it as well as 'approved' : could you fill me in on the context of what this document is and what its regulatory status is .

I notice that point e) recommends using 'ACAS' to help collision avoidance . This unqualified advice is a bit at odds with the Eurocontrol 'ACAS Bulettin' linked on a previous post

Finally , yarrayarra , I have heard this before . While some pilots might elect to do this , IMHO it is all a bit unnecessary and overly dramatic . You have , after all , about 12-13 mins to get down to FL100 ( Pax O2 endurance) so even from FL410 you don't need an overall RoD of not much over 2500 fpm . Any delay in getting the descent going with a moderate - I would prefer the word 'controlled' - entry will result in a speed loss which will then allow a very high RoD while re-accelerting back to Target Speed , so it all works out about the same in the end . I agree that there is no time to hang around , but aggressivly banking to maintain positive g while initiating the descent is a bit OTT , in my view ( plus means taking the Autopilot out)