Emergency Descent: Guidance for Controllers

From SKYbrary Wiki

Article Information
Category:	General
Content source:	SKYbrary
Content control:	EUROCONTROL

There is no set of ready out-of-the-box rules to be followed universally. As with any unusual or emergency situation, controllers should exercise their best judgment and expertise when dealing with emergency descent situations. A generic checklist for handling unusual situations is readily available from EUROCONTROL but it is not intended to be exhaustive and is best used in conjunction with local ATC procedures.

Contents 1 Description 2 Useful to Know 3 Anticipated Impact on Crew 4 What to Expect 5 What to Provide 6 Defences 7 Related Articles 8 NATS Flight Deck Procedures Video 9 Further Reading

Description

This article provides guidance for controllers on what to expect and how to act when dealing with emergency descent which takes place in controlled airspace. There are some considerations which will enable the controller, not only to provide as much support as possible to the aircraft concerned, but also maintain the safety of other aircraft in the vicinity and of the ATC service provision in general.

Useful to Know

There are various reasons for the flight crew to initiate an emergency descent. They could vary from events such as of loss of pressurization and in-flight fire to any other situations where it is critical for the airplane to descend to safe altitude and/or to seek the shortest route to an alternate aerodrome.

The emergency descent could be initiated without warning. Depending on the circumstances, the flight crew could begin a high vertical speed descent without warning if the safety of the aircraft is at risk which is in line with the cockpit tasks prioritisation principle: Aviate, Navigate, Communicate.

When an aircraft operated as a controlled flight experiences a malfunction requiring an emergency descent, the crew shall, if able:

• Initiate a turn away from the assigned route or track before commencing the emergency descent (ICAO Doc 7030, para 9.1.1.1 of the European SUPPs). There are no strict rules regarding to which direction the turn should be initiated when beginning an emergency descent. Some military style training, advises that when beginning a not communicated descent, the crew should initiate a left hand side turn in order for the Captain to have a reasonable line of sight, but once again, this is not a generally established practice.
• 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 ADS/CPDLC system, if applicable
• Turn on aircraft exterior lights
• Watch for conflicting traffic both visually and by reference to ACAS (if equipped)
• Coordinate its further intentions with the appropriate ATC unit

Anticipated Impact on Crew

A wide range of practical problems could arise in the cockpit following the decision to initiate an emergency descent:

• Increased workload in the cockpit - During the initiation of an emergency descent, the workload becomes intense as the crew try to resolve the problem with the aircraft, fly the aircraft safely, and plan for the descent.
• Emergency descent procedure - Descent is initiated in accordance with the operator's emergency procedures and associated training.
• Situational awareness issues - The crew may struggle to maintain full situational awareness.
• Communication problems - Several problems connected with air-ground communications could arise including late communication, poor message quality due to donning of oxygen masks, and non-standard phraseology.

What to Expect

• Descent without warning - Pilots are trained to advise ATC as soon as practicable and inform of their intentions. However, during the initiation for an emergency descent, the workload becomes very intense and ATCOs should not expect immediate information about the situation.
• No emergency squawk - workload and surprise often introduce delay in response in squawiking 7700.
• Poor or no RTF - no communication or poor communication quality due to changes in the sound of speech including a distorted sound spectrum because of the oxygen masks.

What to Provide

Best practice embedded in the ASSIST principle could be followed (A - Acknowledge; S - Separate, S - Silence; I - Inform, S - Support, T - Time) :

A - acknowledge the descend (the declared malfunction and emergency if applicable), ask for the crews’ intentions when the situation permits

S- separate the aircraft from other traffic and issue essential traffic information about the emergency descend

S - silence the non-urgent calls (as required) and use separate frequency where possible;

I - inform the adjacent ATC units if the aircraft is approaching or it is near their areas of responsibility; inform your supervisor and relay the flight crew’s intentions

S - support the flight with any information requested and deemed necessary. If necessary inform the crew of the minimum safe altitude.

T - provide time for the crew to assess the situation, don’t press with non urgent matters.

The controller should be prepared to:

• Acknowledge emergency on RTF
• Take all necessary action to safeguard all aircraft concerned
• Suggest a heading, if so required
• Provide separation or issue essential traffic information, as appropriate
• State the minimum altitude, if necessary (REMEMBER: The aircraft shall not descend below the lowest published minimum altitude which will provide a minimum vertical clearance of 300m (1000 ft) or in designated mountainous terrain 600m (2000 ft) above all obstacles located in the area specified.)
• Emergency broadcast if necessary
• After emergency descent and when the situation permits, ask for pilot’s intentions and other important information, such as :
  • Diversion
  • Injuries
  • ACFT damage
• Consider ACFT still to be in an emergency situation - The aircraft could be ready to continue flight without any further complications after the emergency descent, if no structural damage was inflicted or there is no system malfunctions. However, often the crew is not able to assess during flight neither the exact type, nor the extent of the damage.

Defences

• Personal Awareness - ATCOs should always be monitoring the course and altitude of traffic in his/her sector. Being constantly aware of any ongoing deviations should provide precious time for vectoring of nearby traffic.

• Adequate Reaction - Some of the possible actions: transfer all other aircraft to another frequency (possible message to all stations to increase awareness); leave the emergency traffic on the current frequency; increase the volume of the receiver; have a colleague (a separate pair of ears) to also listen to all transmissions from the aircraft.

• Technological Limitations - Try to keep aircraft within radar cover. Have in mind the features of the existing radar system.

• Organisational Awareness - The fast provision of ATCOs during emergency situations should be an objective at administrative level. Periodic training and drills are likely to improve intra-organisational coordination.

Related Articles

• Explosive Depressurisation
• Pressurisation Problems: Guidance for Controllers
• In-Flight Fire: Guidance for Controllers
• Emergency Depressurisation: Guidance for Flight Crews
• Unexpected Events Training (OGHFA BN)
• Safety Warning Reminder Message, 20100722, Emergency Descent in High Traffic Density Situations

NATS Flight Deck Procedures Video

There will be times when controllers will have to cope with unusual situations such as weather avoidance or aircraft emergencies. It is important for controllers to have knowledge of the flight deck procedures that will be used by aircrew in such situations. The following video describes the generic procedures followed by aircrew in certain unusual situations:

Abnormal and Emergency Operations [19:47 mins]

Further Reading

• Guidelines for Controller Training in the Handling of Unusual/Emergency Situations, EUROCONTROL