Multiple line-ups is a technique employed at some busy airports to expedite the departure of aircraft from the runway. It concerns departing aircraft being instructed to line-up on the same runway at different positions using different access taxiways. Multiple line-up is a significant capacity enabler when implemented in line with the ICAO recommendations and phraseology.
The procedures for application of multiple line-ups are described in ICAO Doc 7030, Part 3 - European Regional Supplementary Procedures, Section 3.1.1:
Line-up instructions may be issued to more than one aircraft at different points on the same runway taking into account that intersection take-off criteria shall be complied with, provided that:
a) minimum visibility is established by the appropriate authority. Those minima shall permit the controller and the pilot to continuously observe the position of the relevant aircraft on the manoeuvring area by visual reference;
b) local considerations, such as the airport layout, available radar equipment and local weather phenomena, are defined. The effect of jet blast/prop wash shall be taken into consideration;
c) air traffic service for aircraft involved in multiple line-ups on the same runway is provided on the same radio frequency;
d) pilots shall be advised of the position of any essential traffic on the same runway;
e) the slope of the runway does not render preceding aircraft in the departure sequence invisible to succeeding aircraft on the same runway;
f) pilot readback of line-up instructions is required and contains the runway designator, the name of the intersection (if applicable) and the number in the departure sequence; and
g) wake turbulence separation is applied.
The European Action Plan for the Prevention of Runway Incursions (EAPPRI), includes the following advice:
- When using multiple line-ups, do not use oblique or angled taxiways that limit the ability of the flight crew to see the runway threshold or the final approach area.
- In order to avoid an aircraft entering the runway while another is taking off, multiple line-ups are inadvisable in cases when the taxiway intersects the runway at an acute angle, thus preventing the pilots from having a good view down the runway. Such a situation classically applies if a Rapid Exit Taxiway (RET) (intended for landing aircraft use when the opposite direction of runway use applies) is used to clear departing aircraft onto the runway.
- Ensure a clear and robust procedure is in place, and where practicable, appropriate technology is used to show that a runway is occupied, obstructed or unavailable.
- Ensure that Air Traffic Control communication messages are not over long or complex.
- Avoid infringing sight lines from the tower and assess visibility restrictions from the tower, which have a potential impact on the ability to see the runway, and disseminate this information as appropriate. Recommend improvement when possible and develop appropriate procedures.
- Identify any potential hazards of runway capacity enhancing procedures when used individually or in combination and, if necessary, develop appropriate mitigation strategies. (Intersection departures, multiple line-up, conditional clearances etc.)
- Do not issue a line up clearance if the aircraft will be expected to wait on the runway for more than 90 seconds beyond the time it will normally be expected to depart.
- Ensure that Aerodrome Operators and Air Navigation Service Providers regularly review the operational use of aeronautical ground lighting e.g. stop bars, to ensure a robust policy to protect the runway from the incorrect presence of traffic.
In addition to the standard phraseology provided in Chapter 12 of PANS ATM (Doc. 4444), instructions for multiple line-up shall be issued in accordance with the criteria contained in ICAO Doc7030:
ATC: LINE UP AND WAIT RUNWAY (number), INTERSECTION (name of intersection), (essential traffic information)
ATC: ABC123 LINE UP AND WAIT RUNWAY 22, INTERSECTION BRAVO, NUMBER 2 FOR DEPARTURE, NUMBER ONE IS BLU JET B737 DEPARTING FROM ALPHA ONE.
A/C: LINE UP AND WAIT RUNWAY 22, INTERSECTION BRAVO, NUMBER 2, ABC123
Clear policy and robust procedures should be implemented by ATC. The use of full call signs for aircraft and vehicles, and the use of separate frequencies for each runway, will improve situational awareness and reduce the likelihood of confusion.
Multiple Line-Ups from Different Intersections
Air traffic controllers should pay attention when issuing clearances for multiple line-ups as the presence of more than one departing aircraft on the runway will normally lead to prolonged runway occupancy time, this is especially valid when the runway is used for mixed operations (departures and landings).
There are two main cases with respect to the visibility from the ATC Tower:
A) The Intersections are visible to the Controller
The controller should:
- maintain visual observation of the positions of the aircraft involved and verify the reported position by the flight crew, in particular when line-up is requested; and
- subject to the information provided by available sources, such as visual observation, procedural, or radar surveillance display of conflicting traffic, issue, delay or deny ATC clearance to enter the runway;
- when transmitting the line-up clearance, advise all concerned flight crews of the respective position of other traffic sequenced in multiple line-ups;
- maintain strong awareness of the flight crew read-back.
B) An Intersection is not visible to the controller
- Multiple line-ups should NOT be used when an intersection (used for line-up) is not visible to the controller. (see Doc 7030 Part 3, para. 3.1.1.a)
Multiple Line-Ups from the Same Intersection
This procedure is not considered as application of multiple line-ups on the same runway as defined by Doc 7030,Part 3, paragraph 3.1.1 which reads that “Line-ups instructions may be issued to more than one aircraft at different points on the same runway …”.
ANSPs which are using multiple line-ups from the same runway access point shall consider this procedure as an application of a conditional ATC clearance for sequencing of departing traffic.
Multiple line-ups, intersection departures and conditional clearances may increase runway throughput.
An advanced ATC tool for optimizing runway throughput thus increasing runway and airport capacity is the DMAN (Departure Manager) developed by EUROCONTROL and included in the SESAR Concept of Operations. DMAN is implemented at some aerodromes (such as Frankfurt) and tested and validated for other major European aerodromes.
Multiple line-up procedure can be considered safe if implemented in compliance with ICAO provisions and following a safety assessment that will help identify appropriate risk mitigation measures. Two types of mitigation strategies have been identified by the "Safety Assessment of Airside Capacity Enhancement" carried out by EURCONTROL (see Further Reading):
Main Current Mitigations
- EAPPRI – restriction on use of oblique angled taxiways.
- Compliance with ICAO published phraseology and other conditions (ICAO Doc 7030, Part 3, Section 3.1 Conditions for application).
- Flight progress strip management to show occupied runway and sequence (not universally used).
- Provision of training and assessment for Pilots regarding Aerodrome signage, markings and lighting.
Additional Potential Local Mitigations
- Implementation of A-SMGCS Level 2.
- Restrictions during hours of darkness (UK and others).
- Local safety assessment including looking at combination of conditional clearances and multiple line-ups and setting visibility criteria.
- Constraints on immediate take-offs.
Accidents and Incidents
Flight Safety Foundation
Air Services Australia