1. Emergency Descent Procedures
B.5.4
WP 88
Emergency Descent Procedures
Presented by:
Bill Holtzman
Member of TOC
Hi I’m Bill Holtzman from USA. I re-joined TOC in November when Mark O’Neil retired. I had been our TOC Rep from I’ve been an en route controller in the Washington, DC area for 25 years. I am a TOC Committee member and am are here to present our paper reviewing the PANS-ATM emergency descent procedures.

2. Emergency Descent Procedures, B.5.4 WP 88
You: Clear the Area!
Imagine you are working some of the traffic shown in the graphic. One of your pilots suddenly informs you that pressurization is lost, they are declaring an emergency and have started their descent. Can you ever imagine using the phrase <click> “Clear the area!”? Can you imagine what would happen if the pilots were told to clear a certain area and were left to their own as to exactly what maneuvers to conduct? The result would be chaos. Few controllers would ever even consider such a method.
Emergency Descent Procedures, B.5.4 WP 88

3. Emergency Descent Procedures, B.5.4 WP 88
PANS-ATM: Broadcast
GENERAL
Upon receipt of advice that an aircraft is making an emergency descent through other traffic, all possible action shall be taken immediately to safeguard all aircraft concerned. When deemed necessary, air traffic control units shall immediately broadcast by means of the appropriate radio aids, or if not possible, request the appropriate communications stations immediately to broadcast an emergency message.
Yet this method is written in the PANS-ATM. Section says that, “When deemed necessary, air traffic control units shall immediately broadcast an emergency message.” Is the emergency message to be advisory or for control purposes? If advisory, why is it necessary when the most urgent priority is clearing the descent path?
Emergency Descent Procedures, B.5.4 WP 88

4. PANS-ATM: Phraseology
ATTENTION ALL AIRCRAFT IN THE VICINITY OF [or AT] (significant point or location) EMERGENCY DESCENT IN PROGRESS FROM (level) (followed as necessary by specific instructions, clearances, traffic information, etc.).
Section provides the phraseology and indicates that this message could be advisory or for control purposes.
Emergency Descent Procedures, B.5.4 WP 88

5. PANS-ATM: Response 15.1.4.2 ACTION BY THE PILOT-IN-COMMAND
It is expected that aircraft receiving such a broadcast will clear the specified areas and stand by on the appropriate radio frequency for further clearances from the air traffic control unit.
Section advises the pilot to clear the specified area when in receipt of such a message. Obviously, the phrase “clear the specified area” is wide open to interpretation, and is giving the pilot discretion to conduct any maneuver deemed necessary. If you have weather in your sector, would you ever say anything like, “Attention all aircraft. You are all cleared to deviate as necessary to avoid weather.”? Controllers control at the individual aircraft level – they don’t cede control authority to groups! This method and phraseology are leftover from another era.
Experienced controllers understand these issues well and know better, but people new to our business could be confused and misled by these procedures.
Emergency Descent Procedures, B.5.4 WP 88

6. Emergency Descent Procedures, B.5.4 WP 88
Eurocontrol
“…unless the emergency broadcast is appropriately targeted and contains unambiguous instructions, there is the possibility of aircraft unexpectedly deviating from their track to ‘clear the specified area’ which, in areas of high traffic density, has the potential to create additional hazardous situations.”
This issue has been the subject of attention for years. In July 2010, Eurocontrol published a Safety Message essentially cautioning against making this emergency broadcast, explaining that it might cause aircraft to deviate from their track. The last thing you need during an emergency is an unexpected conflict or another emergency.
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IFALPA
IFALPA believes that the provisions do not appear to reflect fully the realities of the present day operational environment. There is no direction as to how aircraft are to achieve the aim to "clear the specified areas", i.e. which kind of turn, or other action, is expected from them.
IFALPA also weighed in on this debate, questioning how a pilot could possibly determine how to clear a specified area in today’s environment. Pilots like very specific clearances too. If the pilot has to interpret a clearance and perform some calculations or other processing, it becomes both a workload and a liability burden.
Emergency Descent Procedures, B.5.4 WP 88

8. Emergency Considerations
level of surveillance
equipage (ACAS)
aircraft performance characteristics
traffic density
meteorological
communications
nature of the emergency
condition of the pilots
many others…
The procedures need to be changed, but how? Let’s consider the situation of the pilot of the emergency descent aircraft. In the few seconds available to determine a course of action, what factors affect the controller’s handling of the situation?
Level of surveillance – obviously, with no surveillance the controller has fewer options to intervene tactically. In that case, the pilot’s ACAS is the best tool for tactical separation.
Equipage – if the aircraft does not have ACAS, the controller might use more aggressive turns to clear the descent path
Performance – the controller needs to project the descent path and this is a function of the aircraft’s performance
(Traffic density) Obviously, the more dense the traffic in the projected descent path, the more treacherous the descent. The controller in some cases might suggest the emergency aircraft turn.
(Meteorological) The controller might advise the emergency aircraft to avoid weather
Communications with the aircraft may be difficult and the controller may need more aggressive turns since the descent path is unknown.
Depending on the emergency, the controller may offer additional guidance such as headings for an airport or towards lower terrain.
If the pilots are partially incapacitated by depressurization or other reasons, the controller may need to make allowances for this.
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9. Emergency Descent Procedures, B.5.4 WP 88
Doc 7030, NAT Supplement
An aircraft compelled to make a descent through MNPS airspace, whether continuing to destination or turning back, should, if its descent will conflict with an organized track:
plan to descend to a level below FL 280;
prior to passing FL 410, proceed to a point midway between a convenient pair of organized tracks prior to entering that track system from above;
while descending between FL 410 and FL 280, maintain a track that is midway between and parallel with the organized tracks; and
contact ATC as soon as practicable and request a revised ATC clearance.
To determine appropriate controller procedures, let’s review other guidance for pilots. In the North Atlantic Regional Supplement (Doc 7030), pilots are advised to maneuver midway between tracks and descend between the tracks.
MNPS is Minimum Navigation Performance Specification, older version of RNP.
Emergency Descent Procedures, B.5.4 WP 88

10. Doc 7030, Euro Supplement
When an aircraft operated as a controlled flight experiences sudden decompression or a malfunction requiring an emergency descent, the aircraft shall, if able:
initiate a turn away from the assigned route or track before commencing the emergency descent;
advise the appropriate air traffic control unit as soon as possible of the emergency descent;
set transponder to Code 7700 and select the Emergency Mode on the automatic dependent surveillance/controller-pilot data link communications (ADS/CPDLC) system, if applicable;
- continues with (d) through (f)
The European Supplement of Doc 7030 includes this instruction to turn away from the track before starting the descent.
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11. Emergency Descent Procedures, B.5.4 WP 88
No turns
So let’s look at some graphical illustrations of these situations. In this case, the aircraft simply descends along the route. If there is traffic below, it could certainly be a problem. Modern avionics could actually reduced safety in this case, since the aircraft fly airways more precisely than they did years ago. This supports the idea of the emergency aircraft turning.
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Right offset
Here is an aircraft turning off course to the right to avoid the airway.
Emergency Descent Procedures, B.5.4 WP 88

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Left offset
But what if there is traffic right, whether a close parallel airway, an aircraft on a vector or even a VFR? Australia is currently building parallel, opposite-direction airways to take advantage of ADS-B, since their airways no longer need to be tied to navigational aids.
The pilot may see this traffic on ACAS or the controller may advise the pilot of it, and the pilot may then turn left. Most major carriers call for 30 deg turns to get well clear of the airway but in congested airspace this could be too much.
Emergency Descent Procedures, B.5.4 WP 88

14. Micro offset environment
Meanwhile, ICAO will be publishing changes to the PANS-ATM in November to encourage the use of micro-offsets of nm. In this emerging micro-offset environment, descending exactly on airway might be the best method. Clearly, the decision for the pilot and/or the controller is highly situational. There’s no “one size fits all”.
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State Letter 15 Apr
ACTION BY THE ATS UNIT
Immediately upon recognition that an aircraft is making an emergency descent, all possible action shall be taken immediately to safeguard all aircraft concerned.
Appropriate actions may include:
broadcasting an emergency message;
issuing traffic information and/or instructions to aircraft affected by the descent;
advising the minimum flight altitude for the area of operation; and
inform any other ATS units which may be affected by the emergency descent.
The task of updating aircraft emergency descent provisions in PANS ATM (Doc. 4444) was assigned to the ICAO Ops Panel in September IFALPA and IFATCA agreed to take on the co-rapporteurship. The Panel was productive, as Raimund has already discussed, and the Panel forwarded a proposal to the ANC.
Here is the proposed new text for the ATS procedures as distributed in a State Letter dated 15 April. The option to make an emergency broadcast is still included, but only as one of many options.
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16. Emergency Descent Procedures, B.5.4 WP 88
State Letter 15 Apr
ACTION BY THE PILOT OF THE AIRCRAFT IN AN EMERGENCY DESCENT
The pilot shall take the following steps as soon as practicable in the order appropriate for the circumstance:
navigate as deemed appropriate by the pilot;
advise the appropriate ATS unit of the emergency descent and if able intentions;
set transponder to Code 7700 and, if applicable, select the appropriate emergency mode on ADS-B
and/or ADS-C;
turn on aircraft exterior lights (commensurate with appropriate operating limitations);
watch for conflicting traffic both visually and by reference to ACAS (if equipped);
Here are the proposed procedures for the pilot of the emergency aircraft. Note there is no specific navigation guidance and the second bullet is to advise ATC. There is also an item to use ACAS to avoid traffic.
Emergency Descent Procedures, B.5.4 WP 88

17. Emergency Descent Procedures, B.5.4 WP 88
State Letter 15 Apr
f) coordinate further intentions with the appropriate ATS unit;
g) as applicable, set ACAS to “TA only” mode; and
h) when emergency descent is complete, and as soon as practicable, set ACAS to “TA/RA” mode.
Note 1.— Procedures for the use of ACAS are contained in PANS-OPS, Volume I, Part III, Section 3, Chapter 3.
Note 2.— Selecting “TA only” does not stop the generation of resolution advisories by the ACAS in other aircraft; rather, it signifies to the ACAS of other aircraft that a co-ordinated resolution advisory is not possible.
Item (g) refers to a setting of ACAS.
When a commercial airliner loses an engine, the pilot is usually instructed to change ACAS to TA mode, because the aircraft is not capable of responding to an RA.
The thinking here is that if the aircraft is descending at 10,000 feet per minute in an emergency, the ability of the pilot to respond to an RA is limited. By setting the ACAS in “TA mode”, the collision avoidance algorithm will force any evasive maneuvers onto the pilot of the other aircraft. This is something of a controversial issue. It is argued by the International Coordinating Council of Aerospace Industries Associations (ICCAIA) that:
If the descent rate is above 10,000 fpm, the ACAS automatically switches itself to standby mode. The ACAS of other aircraft will not generate an RA or TA in this case.
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18. Emergency Descent Procedures, B.5.4 WP 88
Use of ACAS TA Mode
If the descent rate is below 10,000 fpm, ICCAIA argues that when the RA first alerts the other aircraft, the emergency aircraft may still be increasing its descent rate. A descent RA by the traffic would then actually increase the chance of collision.
Bottom line is we are IFATCA, we are controllers. What the pilot decides to do with his during an emergency descent is no different from any navigation choice – it’s the prerogative of the pilot…hence the term, “as applicable”.
The TOC itself is not in full agreement on our position on this, but the State Letter is already out.
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19. Emergency Descent Procedures, B.5.4 WP 88
State Letter 15 Apr
ACTION BY THE PILOT OF AIRCRAFT RECEIVING EMERGENCY DESCENT BROADCAST
Unless specifically instructed by the ATS unit to clear the area or threatened by immediate danger, the pilot shall take the following actions:
continue according to current clearance and maintain listening watch on the frequency in use for any further instructions from the ATS unit; and
watch for conflicting traffic both visually and by reference to ACAS (if equipped).
The new procedures now specifically discourage the deviation of any non-emergency aircraft off-route, and encourage the use of ACAS by those aircraft to avoid the emergency aircraft.
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20. Comments by 31 July 2014 Publication 10 November 2016
State Letter 15 Apr
Comments by 31 July 2014
Publication 10 November 2016
Here is the time frame for the publication of these changes.
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21. Emergency Descent Procedures, B.5.4 WP 88
Conclusions 1
Emergency descent situations are analogous to Resolution Advisories in that they may introduce a second decision-maker within the ATC environment - the pilot of the aircraft executing an emergency descent. Depending on circumstances, the pilot may or may not be able to coordinate the trajectory of the aircraft with the controller.
ICAO provides guidance regarding emergency descent for pilots in Doc 8168 and for both pilots and controllers in Doc 7030 and PANS-ATM sections and
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22. Emergency Descent Procedures, B.5.4 WP 88
Conclusions 2
The guidance in the PANS-ATM is outdated in today’s congested environments, and can actually cause more conflicts than it seeks to prevent. The PANS-ATM uses the term “clear the specified area” ( ), which directly implies pilots should navigate off their assigned routes at their own discretion, in conflict with core principles of air traffic control.
The guidance in the PANS-ATM does not establish clarity in “the decider” role in the event of an emergency descent and in fact encourages a situation in which all of the affected pilots may be navigating independently. This is likely the worst possible scenario for a controller.
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Conclusions 3
In an emergency descent, both the pilot and the controller must consider multiple factors and instantly determine the best course of action. The pilot may be able to transmit intentions, but if not the controller must attempt to extrapolate the aircraft trajectory. In that case, the pilot must consider the potential for a traffic conflict with aircraft below and take appropriate action, because no other system participant has full knowledge of the future trajectory of the emergency aircraft.
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Conclusions 4
Optimal usage of radio frequency transmission time is critical in any emergency situation.
An aircraft executing an emergency descent cannot be expected to respond to a resolution advisory.
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Questions?
Emergency Descent Procedures, B.5.4 WP 88

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Recommendations
IFATCA policy is:
IFATCA supports the modernization of emergency descent procedures.
and is included in the IFATCA Technical and Professional Manual.
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27. Emergency Descent Procedures, B.5.4 WP 88
SL AN 13/2.5-13/32
3.4 Where the lateral separation minima or route spacing is 11.1 km (6 NM) or more, but less than 30 NM, it is now also proposed to allow offsets to the right of the centre line in increments of tenths of a mile up to a maximum of 0.5 NM (0.9 km).
Effective November 2014
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28. Emergency Descent Procedures, B.5.4 WP 88
ICCAIA
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