Landing without ATC Clearance

Article Information

Category:

Runway Incursion

Content source:

EUROCONTROL

Content control:

EUROCONTROL

Description

Landing without clearance occurs when the pilot/flight crew of an arriving to land aircraft fails to obtain clearance to land from air traffic control (ATC) before landing their aircraft at a controlled aerodrome.

This article gives an in-depth description of the most common factors which may lead to landing without ATC clearance occurrences in line with identified patterns. It also provides an overview the most effective barriers against such occurrences and describes good practices that could be used by pilots/crews and air traffic controllers to prevent landing without clearance occurrences.

Hazards and Effects

The hazard(s) associated with and the possible effects of landing an aircraft on a runway without clearance are essentially the same as for a runway incursion. Increased risk of collision for one or more aircraft on the ground (landing surface) is the predominant concern. The aircraft landing without clearance also can be at extreme risk of colliding with one or more vehicles travelling along the runway or crossing the runway, or striking people or objects. Similar to other occurrences (e.g. loss of separation), the safety impact is also determined by the traffic situation. There are three main scenarios for landing without ATC clearance:

The runway was not occupied and no runway clearance was granted to other traffic (safest scenario);
The runway was not occupied (yet) but a clearance had been issued to other traffic to either enter or cross the runway and the controller or the person in the other aircraft or vehicle had a chance to prevent the conflict;
The runway was occupied by another aircraft or a vehicle.

Investigations of accidents and serious incidents also reveal secondary risk factors for the flight crew or pilot of the landing aircraft. In the moments after realising the lack of landing clearance, some have aborted the landing (including after touchdown) and initiated a go-around manoeuvre. These and other unbriefed/unexpected actions in some cases exacerbated risk factors or caused consequences such as a tail strike, loss of separation with another aircraft in the aerodrome traffic circuit. Moreover, the startle factor produced by the pilot’s or flight crew’s sudden recognition of the error (landing without clearance) can contribute to loss of control in flight. Hesitation to respond, inappropriate flight control inputs or unsafe over-compensation for the error have occurred — potentially leading to a runway excursion or to controlled flight into terrain (CFIT).

Contributing factors

The factors listed below, either combined or on their own could "assist" the build-up of a situation where an aircraft (almost) lands without receiving an ATC clearance to do so:

Failure to call as instructed - sometimes aircraft are transferred too early or too late (after landing) to the Tower frequency. At busy aerodromes, it is customary to instruct pilots to call again later (e.g. at 4 miles from touchdown, when overflying the outer marker or other radio aid, etc.) in order to obtain a landing clearance. The period of time may be long enough for the pilots to forget they had to make a call, especially given the higher workload situation. Another common failure scenario is the pilot/flight crew remaining on the approach frequency instead of switching to the Tower.
Loss of Communication ;– e.g. due to equipment failure, mistuning the next (TWR) frequency. In some cases, e.g.VFR flights, the tower controller might not even be aware that an aircraft is approaching and is intending to land.
Runway confusion – e.g. at aerodromes with more than one runway or if two separate aerodromes are close to each other.
Communications misunderstanding – e.g. an instruction to continue the approach and/or to expect landing clearance might be interpreted by the crew as a clearance to land.
Expectation bias - it is a part of human nature to believe something expected has already happened. Pilots, especially under high workload, may easily assume that, among the other things said and done, the landing clearance has been received. The final approach is one of the busiest phases of flight. With so many things to do (especially in adverse weather conditions), it is possible that pilots forget to obtain a landing clearance. The Tower controller, on the other hand, may also be too busy (or may be waiting for a call from the aircraft being unable to see it) and fail to issue the clearance timely (or a go-around instruction, as appropriate).
Absence of clearance – a landing clearance was not received but for various reasons the crew believed that they had or discovered too late that they had none (e.g. they were used to receiving it several minutes before landing).
Deliberate – the crew were aware that they had not received a landing clearance but after assessing the circumstances decided that the best (safest) course of action was to land.

Prevention Barriers

Prevention barriers are intended to avert the event which in this context is to reduce or eliminate the risk forof landing without clearance occurrences. The advice and guidance provided hereafter are derived from common sense, best practices and lessons learned from relevant studies and initiatives such as the Global Action Plan for the Prevention of Runway Incursions (GAPPRI). It is not intended to supersede or replace regulatory requirements, local instructions and procedures.

Procedures and best practice for pilots/crews:

Use of triggers to check or acknowledge the receipt of a landing clearance:
- An SOP to select the landing/taxi lights on only when a landing clearance is received (see GAPPRI AO25, AO26);
- If feasible, the inclusion of an item in the landing check-list;
- An SOP to do so at an existing fixed point in an approach such as at a height-defined stabilisation gate.
Introducing an SOP which requires that two-way contact is established on each new frequency before the pre-select frequency is changed;
Ensure potential for early or late landing clearance as well as late handover from approach to tower frequency is included as part of the TEM Briefing. Consider effective mitigation strategies, e.g. early configuration and optimum sequencing of cockpit tasks during approach to relief the Pilot Monitoring (PM) from high workload and possible task saturation (see GAPPRI AO27). Consider nudging ATC for handover or issuance of landing clearance, if required.
Making sure that the correct runway and/or approach procedure are entered into aircraft on-board systems and that the information is displayed to both pilots;
Ensure pilot/crew positive visual identification of the correct runway;
Ensure pilot/crews are always mentally prepared for a go-around, rejected or baulked landing.

Procedures and best practice for controllers:

Visual runway inspection before issuing a clearance for runway entery or crossing – this may reveal a (possibly unknown or forgotten) aircraft that is about to land without a clearance.
Visual observation of all traffic to confirm all clearances are properly complied with. The probability that an aircraft (with a valid landing clearance) may attempt to land on a wrong runway or taxiway should always be considered.
Maintenance of situational awareness is critical. Forgetting about an aircraft being on the final is a common reason for landing without clearance. Establishing and following procedures for strip handling (e.g. placing marks or moving the paper strips) can be a simple and effective solution;
Coordination with adjacent units (especially approach units) is essential. If the situation permits, the Tower should be advised that an aircraft is about to call. If this is not possible due to congested traffic a procedure for electronic handover/takeover may be considered.
Relying only on pilot reports in congested traffic situations is sometimes not advisable. The pilots may forget that they need to make a position report or they may not be able to do it due to the high frequency occupancy. In some cases, assistance from the approach could be helpful if the situation permits (e.g. the approach controller advises the Tower via hotline when an aircraft is over a specified position). Surveillance systems such as ASMGCS might also be a viable option;
Timely aircraft handover to the tTower (e.g., not later than FAF/FAP) as workload and possible task saturation for the PM might lead to forgetting frequency switching or check-in with Ttower (see GAPPRI Annex 3 data findings).
Strict adherence to standard phraseology and readback/hearback procedures is essential for preventing misunderstandings and detecting expectation bias. This is especially true for “expect landing clearance” instructions.
The overall use of the phrase “expect landing clearance” might need to be considered. Generally, a pilot approaching an aerodrome is expecting a landing clearance anyway and will continue to expect it regardless of whether a specific instruction for this is received. It may be a good idea to use the phrase on special occasions only (e.g. if a training or an isual runway inspection before issuing a clearance for runway entery or crossing – this may reveal a (possibly unknown or forgotten) aircraft that is about to land without a clearance. Visual observation of all traffic to confirm all clearances are properly complied with. The probability that an aircraft (with a valid landing clearance) may attempt to land on a wrong runway or taxiway should always be considered. Maintenance of situational awareness is critical. Forgetting about an aircraft being on the final is a common reason for landing without clearance. Establishing and following procedures for strip handling (e.g. placing marks or moving the paper strips) can be a simple and effective solution; Coordination with adjacent units (especially approach units) is essential. If the situation permits, the Tower should be advised that an aircraft is about to call. If this is not possible due to congested traffic a procedure for electronic handover/takeover may be considered. Relying only on pilot reports in congested traffic situations is sometimes not advisable. The pilots may forget that they need to make a position report or they may not be able to do it due to the high frequency occupancy. In some cases, assistance from the approach could be helpful if the situation permits (e.g. the approach controller advises the Ttower via hotline when an aircraft is over a specified position). Surveillance systems such as ASMGCS might also be a viable option; Timely aircraft handover to the tTower (e.g., not later than FAF/FAP) as workload and possible task saturation for the PM might lead to forgetting frequency switching or check-in with Ttower (see GAPPRI Annex 3 data findings). Strict adherence to standard phraseology and readback/hearback procedures is essential for preventing misunderstandings and detecting expectation bias. This is especially true for “expect landing clearance” instructions. The overall use of the phrase “expect landing clearance” might need to be considered. Generally, a pilot approaching an aerodrome is expecting a landing clearance anyway and will continue to expect it regardless of whether a specific instruction for this is received. It may be a good idea to use the phrase on special occasions only (e.g. if a training or an airworthiness flight is intending to perform a go-around or a touch-and-go). Avoid issuance of late landing clearance. Busy frequency and high workload may contribute to controller being unable or forgetting to issue the landing clearance. Criteria should be decided locally (e.g., not below 1,000ft above ground level).

The most common reasons for landing without clearance are:

The EUROCONTROL report on landing without clearance cites contributory factors from a relevant 1994 report by researchers at the U.S.National Aeronautics and Space Administration (NASA). Causal factors from 37 events reported to NASA’s Aviation Safety Reporting System (ASRS) included cases of pilots who attempted to communicate with ATC on the wrong frequency; pilots who did not realize they lacked the clearance to land until the aircraft was on the runway (or turning off the runway and changing to the ground control frequency; pilots who said high workload had contributed to failure to obtain landing clearance; and pilots more likely to forget to contact the tower controller for landing clearance if ATC instructed them to do so at a relatively long distance from the runway (i.e., at the outer marker or as far as 20 nm [27 km] from the threshold).

Mitigation Barriers

The barriers that may mitigate the consequences of landing without clearance can be combined in two groups:

Conflict detection (the risk of conflict was identified early enough and proper action was taken):
- Visually by the controller;
- With a system support tool by the controller;
- Visually or while monitoring the audio channel by the flight crew/vehicle driver.
Conflict resolution (the conflict could not be prevented but was detected and properly resolved):
- By the controller after visual detection;
- By the controller with the help of a surveillance system;
- By the controller after detecting the risk with a safety net (e.g. RIMCAS);
- By the flight crew/vehicle driver after visual detection;
- By the flight crew/vehicle driver after detecting it while monitoring the frequency;
- By the flight crew/ground crew after detecting it with system support.

Factors that May Affect Barrier Effectiveness

Each aerodrome has its own specific set of features that may affect the prevention and mitigation barriers (some of these may also vary with time):

Radar guided approaches (affect the possibility of communication loss being detected when transponder code 7600 is used);
Meteorological conditions (in-flight/ground visibility affect the pilots’/controllers’ ability to detect potential threats in good time);
Runway status (active, inactive, closed);
Clearance conditions (multiple clearances, conditional clearances, procedures for issuing landing clearances);
Physical visibility (control tower position, aerodrome layout, temporary obstacles).

Safety Nets

Final Approach Runway Occupancy Signal (FAROS) is an FAA-sponsored concept, which is now being deployed for operational evaluation in the USA. The concept is to inform the approaching aircraft (using PAPI or VASIS) that the runway is occupied.
Runway Status Lights (RWSL) is developed and deployed at major airports in the USA. It is a fully automatic advisory safety system which provides direct alerts to both vehicles and pilots independently of the normal traffic control system operated by ATC. When RWSL indications contradict clearances, pilots and vehicle drivers are expected to prioritize response to the status lights. The absence of RWSL indications however does not equate to an ATC clearance to proceed.
Advanced Surface Movement Guidance and Control System (A-SMGCS) is a modular system consisting of different functionalities to support the safe, orderly and expeditious movement of aircraft and vehicles on aerodromes under all circumstances. Higher levels of implementation deliver safety nets, conflict detection and resolution as well as planning and guidance information for pilots and controllers.
Runway Awareness and Advisory System (RAAS) is designed to improve flight crew situational awareness, thereby reducing the risks of runway incursion, runway confusion and runway excursions. It uses airport data stored in the EGPWS database, coupled with GPS and other on-board sensors, to monitor the movement of an aircraft around the airport. It also provides audio or visual advisories and warnings depending on the aircraft position.
Enhanced Vision System (EVS) is a technology which incorporates information from aircraft based sensors (e.g., near-infrared cameras, millimetre wave radar) to provide vision in limited visibility environments. Safety is enhanced, especially during approach and landing in limited visibility. Obstacles such as terrain, structures, and vehicles or other aircraft on the runway that might not otherwise be seen are clearly visible on the IR image.

Landing without ATC Clearance

Landing without ATC Clearance

Description

Hazards and Effects

Contributing factors

Prevention Barriers

Mitigation Barriers

Factors that May Affect Barrier Effectiveness

Safety Nets

Further Reading