Air-Ground Voice Communications

Feature Desk, Aviation Gurukul, GOLN

3 years ago

Air-Ground Voice Communications

Description

Until data link communication comes into widespread use, air traffic control will continue to depend heavily upon voice communications, which are affected by various factors. Any breakdown in communication between the pilot and ATCO can result in a hazardous situation, especially in controlled airspace.

Alternative means of communication do currently exist but they are still very limited in their capability to substitute what RTF is usually employed.

Problems with Air-Ground Communications have been a significant cause or a contributory factor in many aircraft accidents and serious incidents.

Types of Communication Breakdown

Communication breakdown may result from:

Failure to hear or to respond to a message because of:
- Communication equipment problems caused by the malfunction or complete failure of aircraft or ground equipment – becoming less of an issue with improved system redundancy;
- Radio Interference, which makes the message difficult or impossible to read;
- Blocked Transmissions / Undetected Simultaneous Transmissions (USAT);
- Call-sign Confusion – the message was wrongly addressed or was taken by another aircraft;
- Flight crew unintended mismanagement of radiofrequency or box selection – which remains one of the main causes of prolonged loss of communication;
A breakdown in radio discipline resulting in the pilot receiving and acting on an incorrect version of the message passed, due for example to:
- Failure to use standard phraseology;
- Poor language skills;
- Failure of the read-back/hear-back process;

Effects

Communication breakdown may result in:

The pilot failing to fly the required vertical profile which may lead to a level bust, or not following the required horizontal profile:
- Either situation may cause the aircraft to make an unauthorised entry of designated airspace (airspace infringement) which may lead to disruption of air traffic causing risk to other airspace users and increased workload for pilots and controllers, or may put the infringing aircraft at risk from ground hazards such as artillery firing;
- Either situation can lead to loss of separation from other aircraft or airborne objects (Balloons or parachutists for example) which may result in a collision.
- The level bust may also lead to a collision with an obstacle or the ground (CFIT);
- Injury, especially to cabin crew or passengers, may be occasioned by sudden manoeuvres to avoid collision with other aircraft or the ground, or as a result of a wake vortex turbulence encounter;
The pilot changing to an incorrect frequency or not implementing a frequency change, leading to:
- Loss of Situational Awareness;
- Inability to respond to further clearance or to emergency instructions, e.g. avoiding action.
- This is exacerbated if the pilot fails to check in on any frequency having acknowledged a requested change;
Runway Incursion and other hazardous situations while on the ground.
Confusion between, and increased workload for, ATCOs.

Defences

The principal defences against the occurrence of communication breakdown are adherence to relevant SOPs and good radio discipline.

Defence against the effects of communication breakdown includes the following:

Onboard aircraft equipment is designed to warn of a potential collision with other aircraft (ACAS/TCAS).
Ground-based equipment designed to warn of a potential collision with other aircraft: Short Term Conflict Alert (STCA), potential collision with the ground, Minimum Safe Altitude Warning (MSAW), or airspace infringement Area Proximity Warning (APW).

Typical Scenarios

The pilot or ATCO does not use Standard Phraseology resulting in the message being misunderstood.
Part of the message is lost due to radio interference, or because of Blocked Transmission.
The pilot mishears all or part of a clearance, the pilot does not read back the clearance and the ATCO does not challenge the absence of a read-back (read-back/hear-back).
The pilot reads back all or part of the clearance incorrectly but the ATCO does not note the error and does not correct the pilot’s read-back (read-back/hear-back).
The pilot accepts a clearance intended for another aircraft (call-sign confusion).

List of accidents and incidents involving voice communications as a contributing factor

Contributory Factors

Pilot workload.
ATCO workload;
Inadequate language proficiency;
Frequency Congestion;
Non-standard phraseology;
Radio Interference;
Distractions or interruptions;
Fatigue;
Weather;
Emergency Communications.

Solutions

Improved pilot and ATCO training to ensure that pilots and ATCOs understand and follow SOPs, particularly about:
- Radio Discipline;
- Prevention of blocked transmissions
- Emergency Communications.
Recognise and understand respective pilot and ATCO working environments and constraints.
Listen to other communications on the frequency to build situational awareness, avoid talking over transmissions by other users, and be alert to potential call sign confusion.
Promotion of, and training in, Crew Resource Management to ensure that SOPs are applied in the best possible way to ensure:
- The flight clearance is understood. This includes checking to ensure that both pilots agree and understand the flight clearance (cross-checking is a role overseen by the monitoring pilot/crewmember);
- The aircraft follows the flight clearance and does not unintentionally deviate from it. This includes checking the settings made to technical equipment and monitoring the performance of that equipment and the aircraft to detect any error or malfunction.
Action within ATM to improve Team Resource Management, thereby ensuring that:
- The flight crew understand the flight clearance;
- Deviation from an essential element of the clearance is detected and corrected at an early point.
Improved technical equipment.

Air-Ground Voice Communications