45TH ANNUAL CONFERENCE, Kaohsiung, Taiwan, 27-31 March 2006WP No. 88Study Land and Hold Short OperationsPresented by EVP Technical |
Introduction
1.1. Two related topics are Simultaneous Intersecting Runway Operations (SIRO) and Land and Hold Short Operations (LAHSO). Other terms, such as Simultaneous Operations on Intersecting/Converging Runways (SIMOPS) and Simultaneous Operations on Intersecting Runways (SOIR) have also been used. All are related to achieving maximum use of runways, whilst maintaining safety.
1.2. It is expected that, in order to minimize the effect of airports being a restriction on the growth of air traffic, SIRO and LAHSO operations will be expanded and extended.
It is therefore appropriate for IFATCA to review its policy on SIRO and study LAHSO.
1.3. At last year’s IFATCA Conference, Germany expressed concern with regard to the safe operation of LAHSO and requested that the Technical and Operations Committee (TOC) study LAHSO.
1.4. TOC did examine simultaneous runway operations including LAHSO however was unable to reach agreement that would enable the paper to be presented from TOC. In order that work on simultaneous runway operations is not lost this paper is presented by EVP Technical as an information paper.
Discussion
2.1 SIRO and LAHSO – Definitions and Differences
2.1.1 SIRO and LAHSO are not the same, although many incorrectly consider SIRO to simply be the old term for LAHSO.
2.1.2 There are no official definitions in ICAO or other documents for SIRO and LAHSO, so the following definitions are proposed.
2.1.3 SIRO is defined as:
“the simultaneous use of intersecting runways for take-off and/or landing”.
Note 1: SIRO means that the runways are used at the same time (simultaneously) and not sequentially.
Note 2: SIRO is about surface intersections and not airborne intersections.
Regarding Note 1: Sequential use of intersecting runways is the “traditional” use of runways when the full length of the runway (or the remaining length of runway for an intersection departure) is available to the first aircraft and that an operation by a second aircraft on an intersecting runway is not available until the first aircraft has ceased using the runway intersection. The first aircraft will finish using the runway intersection when it has passed the intersection, or exited the runway prior to the intersection, or, for a landing aircraft, has stopped short of the intersection.
Regarding Note 2: To use the term SIRO precisely, the runways must intersect. Airborne crossings, that is of departure, arrival and missed approach paths, without runways intersecting are not SIRO operations. If the runways do not intersect (and are not parallel) then the term “converging runway operations” is used.
2.1.4 LAHSO is defined as:
“an operation that has an Air Traffic Control (ATC) requirement for a landing aircraft to stop short of the full length of the runway”.
Note 1:”Stop short” can be to hold short of a crossing runway, a taxiway or any other point.
Note 2: The landing aircraft is still expected to exit at the first available (or nominated) taxiway – or at least come to a stop on the runway prior to the nominated position.
2.1.5 Although SIRO and LAHSO define different operations, there is an overlap. One form of SIRO is to give a landing aircraft a requirement to hold short of the runway intersection (LAHSO) and for another aircraft to be simultaneously cleared to land or take off on an intersecting runway. This has led some to consider LAHSO is just a sub-set of SIRO operations – however this is not correct as this is only a case of overlap between SIRO and LAHSO.
2.1.6 Examples of LAHSO that are not SIRO are a requirement for a landing aircraft to hold short to permit operations to/from non-intersecting runways or to hold short of a taxi way to enable a crossing of the runway by an aircraft or surface vehicle, etc.
2.1.7 An example of SIRO that is not LAHSO is that both aircraft could have the full length available for landing/take-off but with a separation standard at the intersection (that is a standard other than a definite passing of the first aircraft through the intersection as a sequential operation). This cannot be considered a LAHSO operation as there is no requirement for one aircraft to be a landing aircraft and to hold short of a point on the runway.
2.1.8 The lack of definitions for SIRO and LAHSO has resulted in variations in exactly what operations are being referred to. For example, the USA used the term SIRO (or SOIR) initially and then changed to LAHSO.
2.1.9 Although the terms SIRO and LAHSO appear self-explanatory, different implementations have been used which limit the operations to a subset of all possible operations under that term. For example, SIRO tends to be used for two landing aircraft rather than for two departing aircraft and LAHSO is not used to permit surface operations in Australia (but in the USA may be used to allow an aircraft or vehicle to cross a runway beyond the hold short point). Allowed operations may be expanded in future.
2.1.10 SIRO and LAHSO operations depend on the configuration of the runway and so SIRO and LAHSO operations are limited to particular airports and particular runway configurations. The exact requirements for what are acceptable airport and runway configurations has yet to be defined. Sometimes local operations are misunderstood as generic (or global) operations.
2.2 ICAO Position
2.2.1 The International Civil Aviation Organization (ICAO) does not appear to use the terms SIRO and LAHSO in its Manuals.
2.2.2 ICAO Procedures for Air Navigation Services – Air Traffic Management (PANS-ATM Doc 4444) allows for LAHSO operations. Doc 4444 Landing and roll-out manoeuvres (paragraph 7.9.3) states:
“7.9.3.1 When necessary or desirable to expedite traffic, a landing aircraft may be requested to:
a) hold short of an intersecting runway after landing …”
2.2.3 The ICAO Air Navigation Commission (ANC) has assigned the Operations Panel (OPSP), with the following task:
“OPS-0007 2) Increasing aerodrome capacity. Review operational aspects of existing provisions and proposals aimed at improving aerodrome capacity, including but not limited to: …
b) proposals for independent use of intersecting runways in land and hold short (LAHSO) operations.”
2.2.4 There has already been ICAO work on common lighting and signs required for LAHSO operations.
2.2.5 There is an ICAO manual on Simultaneous Operations on parallel or near-parallel Instrument Runways (SOIR Manual Doc 9643). Note this is not for intersecting runways or converging runways. The similarity of SIRO and SOIR has sometimes resulted in the incorrect term being used in discussion of SIRO. In addition the FAA previously used SOIR for Simultaneous Operations on Intersecting Runways – that is what ICAO uses SIRO for.
2.3 Existing IFATCA Policy
2.3.1 There is IFATCA policy for Simultaneous IFR Operations on Intersecting/Converging Runways. As the policy deals with Converging Runways it covers more than just SIRO. IFATCA policy does not specifically mention LAHSO, but existing policy could be understood to include LAHSO. The policy dates from 1988 and was last amended in 1996.
2.3.2 A summary of the working papers that resulted in the policy follows.
2.3.3 1988 (Rio de Janeiro) Working Paper (WP) 61 “Simultaneous Operations on Intersecting Runways”:
a) Mainly discussed two landing aircraft;
b) Identified two critical positions, the runways crossing and the crossing in the missed approach;
c) Considered that using radar separation would only result in marginal improvements in capacity and that significant improvements in capacity would require visual separation, which would result in higher controller workload and frequency congestion;
d) Listed factors to be considered when developing general conditions and procedures for SIRO; and,
e) Considered it essential for there to be “adequate separation” instead of only traffic information.
2.3.4 1995 (Jerusalem) WP 89 “Review existing policy and develop further policy on simultaneous IFR operations on Intersecting / Converging Runways”:
a) Noted ICAO work on dependent SIRO using hold short procedures;
b) Considered that “dependent” means that special procedures are required for simultaneous operations (that is to hold short, etc). Conflict-free operations (without special procedures) on intersection/converging runways were considered “independent” operations. Considered that LAHSO should always be classified as dependent;
c) Identified three conflict points for departure-and-landing and landing-and-landing situations: at the runway crossing point, in the missed approach and in case of a baulked landing;
d) Discussed Instrument Meteorological Conditions (IMC) operations, including dependent converging instrument approaches and the need for diverging missed approach procedures;
e) Discussed the Converging Runways Display Aid (CRDA), and that in the missed approach the separation is not radar separation but with a minimum protection of 1 NM;
f) Discussed the use of Letters Of Agreements (LOA) before using SIMOPS in Australia;
g) Highlighted the recommendation of the Australian Bureau of Air Safety that “pilots landing on intersecting runways can pass through the intersection without risk of collision should their aircraft fail to stop before the intersection as required”; and,
h) Expressed concern that in order to increase capacity that procedures “are getting closer and closer to acceptable safety limits”.
2.3.5 1996 (Tunis) WP88 Simultaneous Operations on Intersecting Runways:
a) Raised the concern that ICAO Europe had changed its classification regarding SIRO operations, from independent/dependent to Visual Meteorological Conditions (VMC)/IMC.
b) Acknowledged that “the worse the weather is the greater dependency should be”, but still considered that SIRO should always be classified dependent.
c) Concluded that responsibilities of controllers and pilots in VMC must be clearly defined; and,
d) Added policy that when less than required IFR separation, then aircraft and any potential conflict point must be visible to the controller.
2.3.6 It is not proposed to delete or amend existing IFATCA policy. However additional policy will need to be considered in the future. The existing IFATCA policy statements can be seen as general requirements, and should apply to all aerodrome operations, not just SIRO or LAHSO. If policy is required for LAHSO then it should be explicitly stated.
2.4 Dependent, Independent and Segregated
2.4.1 When discussing parallel runway operations, ICAO uses three terms – dependent, independent and segregated. The terms however are not defined in relation to SIRO nor LAHSO and so the following definitions are proposed.
2.4.2 A dependent runway operation is when a clearance or instruction to a landing or departing aircraft is conditional (dependent) on the position or actions of another landing or departing aircraft.
2.4.3 A independent runway operation is when a clearance or instruction to a landing or departing aircraft is not constrained by consideration of the position or cleared route of any other landing or departing aircraft.
Note: Independence requires that if a rejected landing, missed approach, etc is executed by one or more aircraft then there is still no constraint on the aircraft receiving the clearance or instruction.
Independence does not have to take into account emergencies and non-compliance with clearances – which will be managed as required. This management includes safety management that takes into account possibilities of emergencies and non- compliance with clearances in regard to total system safety.
2.4.4 A segregated procedure is to prevent aircraft collision but does not necessarily use an air traffic control (ATC) separation standard.
Note: The segregated procedure must demonstrate the required safety established by safety analysis and then be formally approved for use.
2.4.5 An example of a segregated parallel runway operation on staggered runways is that runway centre-lines are spaced at least 730m apart and that the missed approach path of a landing aircraft diverges by at least 30 degrees from the departure track of the aircraft taking off. Something similar may be used in relation to converging runway missed approaches.
2.5 SIRO and CRDA
2.5.1 Before discussing LAHSO, an example of using SIRO without LAHSO is provided in order to understand the differences and the terms.
2.5.2 Converging Runways Display Aid (CRDA) is a radar tool to assist controllers staggering approaches to converging runways. CRDA uses the radar returns from aircraft on final for the primary runway to provide clearly identifiable “ghost tracks” on the final for the secondary runway, based on distance from the intersection of the runways. This makes it easier for the controller to ensure a radar separation standard between the real and ghost targets on final for the secondary runway, and therefore a radar standard measured from the intersection for the converging aircraft. CRDA is used at many airports in the United States of America (USA). The Visual Aircraft Spacing Tool (VAST) has been developed in Canada. It used CRDA and expanded its functions and applications. CRDA is being considered at Schiphol (Amsterdam).
2.5.3 The procedures are SIRO and not LAHSO as there is no requirement for a landing aircraft to hold short.
2.5.4 The procedure is dependent, as speed control etc is given to aircraft to ensure radar standard spacing between aircraft on final for primary and secondary runways.
2.5.5 The radar separation standard is established on final, but there may not be a radar separation at the intersection, just segregation. The 1995 IFATCA working paper discussed segregation of 1 NM.
2.6 LAHSO – General
2.6.1 LAHSO has been used in various forms for at least 37 years (for example, LAHSO started in 1968 in the USA). The USA Federal Aviation Administration (FAA) estimates that LAHSO increases throughput by 10%. In 2000, LAHSO was used at more than 220 airports in the USA with almost 850 intersecting runway configurations. LAHSO is used today in Australia, Canada and the USA. LAHSO has been investigated in Europe (for example for operations at Schiphol).
2.6.2 LAHSO depends on airport configuration and runway layout. Just because LAHSO is used at an airport does not imply that it is used in all runway configurations.
2.6.3 There are currently no global LAHSO standards (apart from airport signs and lighting). For example the USA use 9 categories of landing aircraft (based on landing distance required) and Australia has three categories (based on approach performance).
2.6.4 LAHSO has evolved over time and changed on the basis of experience. For example, USA Air Line Pilots Association and Air Transport Association had major concerns about LAHSO operations in the USA but in February 1999 reached a new agreement with the FAA covering weather and runway surfaces, training, visual aids (including improved lighting for LAHSO), greater landing distances and handling rejected landings.
2.6.5 For this paper, LAHSO is considered in its widest meaning, that is “an operation that has an ATC requirement for a landing aircraft to stop short of the full length of the runway”“. The reason for holding short is currently mainly used in relation to take-off or landing on intersecting/converging runways, however the points raised in this paper are not limited to these cases.
2.6.6 The challenge is therefore to determine what criteria must be met for safe LAHSO operations.
2.7 Establishment of LAHSO
2.7.1 Before LAHSO is introduced or expanded at any location, there are a number of requirements that should be met. There are ICAO requirements for lighting and signs, etc but there are additional requirements, which are discussed below.
2.7.2 There must be an operational need for LAHSO. LAHSO is a procedure to increase airport capacity safely. The result is that aircraft will be operating in closer proximity to other aircraft etc, which reduces the number of options of dealing with emergencies and other unexpected occurrences. This can be referred to as reducing safety margins. This reduction of safety margins should only be done when there is a significant operational need (and of course the required level of safety must still be met). For example, in the USA Document FAAO 7210.3 states:
“10-3-7. LAHSO. The Air Traffic manager must determine a valid operational need exists before conducting simultaneous takeoff and landing or simultaneous landing operations. This need may be considered evident if:
1. Present airport capacity/acceptance rate will be increased; and
2. Arrival/departure delays will be reduced; and
3. A reasonable saving in fuel consumption will result.”
Note that all these requirements must be simultaneously met. LAHSO should not continue when a significant need no longer exists (for example at periods of the day with reduced traffic levels).
2.7.3 There must be individual certification for each airport and runway, and the certification must specify the operations permitted (landing, take-off, etc). The safety and acceptability of LAHSO depends on the airport and runway configuration and type of operation. There is currently no global standard of what requirements must be met, so it is essential that each airport and runway to be used for LAHSO be individually certified for LAHSO. This will require a complete safety assessment, including determination of landing distance available and rejected landing/missed approach procedures.
2.7.4 There must be sufficient lead time before introduction to ensure training, database updates, etc will be safely completed prior to introduction. This would also include sufficient time for Letters of Agreement with local operators, as required under existing IFATCA policy when there is not a global standard.
2.8 LAHSO Requirements
2.8.1 After the establishment of LAHSO (need, approvals, training etc) have been completed, there are a number of considerations that apply to the operation of LAHSO.
2.8.2 Both the pilot and the controller need to be able to plan in advance of the operation. The approach and landing phase is a very high workload for the pilot, as are busy arrival and departure operations for the controllers. This would require that Landing Distance Available and rejected landing/missed approach procedures are published for controller and pilot reference. The controller also needs to know which aircraft will participate in LAHSO. Whether LAHSO is in progress is part of the Automated Terminal Information Service (ATIS). In Australia, a pilot normally able to conduct LAHSO who cannot accept LAHSO for this particular flight has to advise ATC as soon as possible (when within 200 NM) if unable to accept LAHSO.
2.8.3 It is assumed that constant factors affecting landing distance required, such as a downhill sloping runway, will be taken into account when certifying LAHSO. Some other conditions for varying factors affecting landing distance required (such as no tailwind, wind shear reports, braking conditions other than good) should also be specified when approval for LAHSO is given. This still leaves factors such as amount of headwind/crosswind, air temperature that affect the landing distance required to be promptly updated. It is expected that this will still be done via the ATIS and voice updates as is currently done.
2.8.4 Pilots are required to read back the requirement to hold short. LAHSO is an ATC requirement. Like other ATC requirements a simple acknowledgment is not sufficient and a full read back of the requirement is needed.
2.8.5 LAHSO is not considered suitable for all operations. For example, in the USA student pilots are not permitted to participate in LAHSO.
2.8.6 Procedures must be in place to safely change from LAHSO operations to no LAHSO operations (for example a wind change to a tail wind component without a runway change). For example, if LAHSO is being used for landing pairs of aircraft, then there may be multiple missed approaches until sequencing for reduced capacity is achieved.
2.9 Consequences of rejected landing/missed approach
2.9.1 This handling of rejected landings and missed approaches should be considered as part of normal operations of LAHSO.
2.9.2 There are varying definitions for rejected landings. For example the Flight Safety Foundation defines:
“a rejected landing (also called an aborted landing) is a go-around maneuver initiated after touchdown of the main landing gear”
(also referred to as a “bounce”) whereas others consider, such as in the USA, rejected landings mean an airborne decision to not land, usually at low level, and is pilot initiated. In the USA, LAHSO procedures include a rejected landing procedure to ensure segregation. The USA defines the rejected landing procedure as:
“a published, predetermined heading to be used in the event of a rejected landing. Unless alternative instructions are given by the controller, pilots are expected to execute the procedure as published and remain clear of clouds” (FAA 7110.118 paragraph 8.)
In this paper, “rejected landing procedure” refers to all cases where a landing is not completed, and so refers also to when ATC instruct the aircraft to “go-around”, though it may be better to use a new phrase for such LAHSO cases.
2.9.3 Consider the example of a pilot on final who, for whatever reason, is no longer able to accept LAHSO. If frequency congestion prevents advising ATC, then the pilot should be able to execute a predefined rejected landing procedure safely and advise ATC as soon as possible. Likewise if ATC become aware that LAHSO is no longer permitted (due downwind, wind-shear, etc) or there is another problem that prevents landing (such as runway obstructed) then ATC should be able to instruct the aircraft to follow the LAHSO rejected landing procedure, and know that this is a safe solution.
2.9.4 There is not always a need to execute the rejected landing procedure if LAHSO is no longer possible. If time permits and the frequency is not congested, then the pilot first advises ATC that they are no longer able to accept LAHSO. Alternatively the ATC may become aware that LAHSO no longer applies, for example due wind shear.
The reason for LAHSO requirement may have been for a departure off an intersecting runway and the take off clearance has not yet been issued. In this case the controller may decide that the best option is to delay the take-off clearance and cancel the LAHSO requirement for the landing aircraft, and so allow the landing to continue.
2.9.5 The suitability or otherwise of rejected landing procedures is one of the main reasons for acceptance or rejection of LAHSO operations by controllers and pilots. There has been, and will continue to be, considerable debate on what is acceptable.
2.9.6 The ultimate objective is for independent operations, that is that other aerodrome traffic is not a consideration even if rejected landings procedures are followed. This is what ICAO has tasked OPSP to investigate. Independent operations would likely need larger safety buffers (both for available landing distance and rejected landing procedures) than dependent operations. The number of airports and runway configurations that support independent operations would be smaller than the number that would support dependent operations, and so it is likely that even when independent LAHSO operations are achieved, there will still be a demand for dependent LAHSO operations.
2.9.7 The other factor that affects rejected landing procedures is visibility – both for the tower controller and pilot. It is easier to have independent procedures when the pilot can see the other aircraft. Consider the example today for parallel runways. Depending on the spacing between runways, in VMC simultaneous independent approaches are permitted but not for the same runways in IMC.
2.9.8 The example in the previous paragraph highlights the problem of “independent” if “can see”. The question raised is that if it is an independent approach, why is there a requirement to see the other aircraft? The answer is that the routes of the aircraft, including rejected landings, are segregated and so the procedure is independent – however if one or both aircraft stray from cleared route then due to the close proximity of the aircraft there is only a small reaction time available to avoid collision and so a see-and-avoid requirement exists in the case of straying from cleared route if there is to be an acceptable level of safety.
2.9.9 Dependent operations do require consideration of other traffic by the controller (and often the pilot). The Australian use of LAHSO is dependent operations. Australia defines two types of LAHSO aircraft participation, they are active and passive. The active participant is an aircraft who can be instructed to hold short. The passive aircraft is the other aircraft, for example the landing aircraft on a crossing runway which is allowed to use the full length of the landing runway. Traffic information is given to both active and passive aircraft. The reason for defining passive participation is to ensure both active and passive participation pilots are familiar with Australian procedures for LAHSO. For example, in Australia foreign airlines cannot be passive (nor active) participants in LAHSO.
2.9.10 Unlike the USA, Australia does not define rejected landing procedures and so the controller is responsible for separation of rejected landing aircraft, using visual separation by the controller or delegation to the pilot. The only instruction to the pilot in Australian Aeronautical Information Publication (AIP) regarding LAHSO rejected landings states:
“The manoeuvre that may be required in the event of a go-around must also be considered.” (Australian AIP ENR 54.3).
2.10 Consequence of not holding short
2.10.1 Another area of debate is the Available Landing Distance (ALD) and the consequences of not holding short. The USA defines the ALD as:
“that portion of the runway available for landing and roll-out for aircraft cleared for LAHSO” (FAA 7110.118 paragraph 8)
2.10.2 The pilot has the final authority to say whether a runway is suitable for landing. The various factors that determine whether the runway length is suitable (altitude, slope, braking action, wind, temperature, etc) are the same for whether the full length of the runways is available or a reduced length (LAHSO ALD).
2.10.3 There are on-going discussions in various aviation fora about over-run protection, and this also applies to the full length of a runway. The accident in Toronto last year was not a LAHSO operation but an overrun of the full runway length.
2.10.4 The hold short point has to be clearly identifiable by the pilot and there are ICAO requirements for lighting and signs to indicate clearly to the pilot the hold short point.
2.10.5 The problem is one then of calculating what buffer to apply to the required landing distance to ensure safe operations. The buffer is likely to be smaller for dependent operations and larger for independent operations. The Australian use of LAHSO requires that:
“The pilot must ensure that aircraft manufacturer’s landing distance figures (the demonstrated landing distance) are multiplied by 1.67 for dry conditions, or 1.92 for wet or downwind conditions. In practice, doubling of the manufacturer’s demonstrated minimum runway length requirements is recommended to cover all contingencies.” (Australian AIP ENR 54.3.)
The original distances used in the USA for LAHSO groups was increased in 1999 and there are no reports of a need to increase the distances further, but the discussion on overrun protection may in time affect these distances.
2.10.6 There is the report in the 1995 IFATCA paper that the Australian Bureau of Air Safety Investigation recommended “pilots landing on intersecting runways can pass through the intersection without risk of collision should their aircraft fail to stop before the intersection as required”. The reason for such a statement is understandable, and the intent is for there never to be a situation where two aircraft are simultaneously at the intersection. It is difficult to judge the time at the intersection given that even on short final the speed can vary from landing and slowing, to a “bounce” and late landing, to go-around power and then a change to landing. Some sort of standard for segregation or separation that could be measured in advance would be required in order for this to be reliably complied with. Note: It is unusual to state that non- compliance with an ATC requirement should mean that there is no risk of collision, for ATC should be able to base decisions on expected compliance with a valid ATC requirement.
2.10.7 The issue then returns to the amount of buffer that should be applied. First consider the landing distance available. Consider a landing light aircraft subject to LAHSO with the ALD three times the manufacturer’s required landing distance. Even landing with no braking, the light aircraft would roll to a stop before the runway intersection, and so would have to apply power to reach the intersection. If the separate issue of rejected landing procedure was correctly addressed, then this should provide an independent LAHSO, as even with an allowance for overrun, the aircraft should stop before the intersection and the problem of being simultaneously at the intersection would not apply.
2.10.8 As the manufacturer’s landing distance required gets closer to the ALD, then the question of how much buffer to use applies. In addition, the potential for being simultaneously at the intersection increases, and a standard for staggering traffic may also be required so that segregation or separation is deemed to exist at the intersection.
2.11 Safety
2.11.1 Measurement of safety is still something that cannot always be achieved. For example, some argue that using less than the full length of the runway (for landing or taking off) is less safe than using the full length. However to establish the difference as a numerical measure is not yet reliably possible.
2.11.2 Often the safety objective is to maintain the current level of safety, or of improving the level of safety. If using less than the full length of the runway is considered less safe, by however small a margin, even if not provable numerically, then intersection departures and land and hold short are not possible.
2.11.3 However another way to assess the safety is that aircraft operate from and to varying lengths of runway at every airport. There are well established procedures that allow for calculation of a safe length for take off and for landing.
2.11.4 The difference with intersecting or converging runways operations are the consequences of failing to hold short and the handling of rejected landings. Each of these must be addressed to ensure an acceptable level of safety is achieved.
2.11.5 The long experience of using LAHSO in the USA has created well established procedures for implementing LAHSO. No references have been found for any accident relating to LAHSO operations in the USA. In the period 2002 to 2005 only two incidents were recorded as LAHSO related.
2.11.6 In Australia there were a number of incidents with SIMOPS, a precursor to LAHSO. Australian LAHSO procedures have been modified accordingly. However important issues, such as rejected landing procedures, need further work.
2.12 Pilot and Controller Responsibilities in respect to LAHSO
2.12.1 It is clearly established that the Pilot-in-Command has final authority in relation to the safety of the flight. It also is recognized that the pilot is the authority on the performance of their aircraft. In general, if a pilot advises that he is “unable to comply” with an ATC instruction or “operationally requires” then this is accepted by the controller and an alternative instruction given. This information from the pilot should be given as soon as possible.
2.12.2 The controller is responsible for separation during the approach and on the runway (this is true for both LAHSO and SIRO). The controller has a responsibility to ensure that the pilot is kept informed of operationally significant changes, such as wind, braking conditions, etc. The controller, in order to safely and efficiently manage the traffic, expects compliance with reasonable instructions.
2.12.3 If a pilot of aircraft normally able to participate in LAHSO is aware that LAHSO is in operation and had not advised ATC that they cannot participate then the controller should be able to assume that a reasonable instruction regarding active LAHSO will be accepted and complied with. Once accepted the controller expects compliance, unless an alternative is requested and agreed, or, an exceptional event occurs (for example a failure of an aircraft component that affects braking).
2.12.4 Both the pilot and the controller should be able to expect predefined rejected landing procedures that ensure segregated paths, even in the case of multiple rejected landings.
2.12.5 It is not acceptable as a replacement for rejected landing procedures that traffic information for traffic on the conflicting runway has been given to one or both pilots. The aerodrome environment is one in which aircraft operate in close proximity to other aircraft and hazards, it is a high workload environment for both pilots and controllers, and, there is not sufficient time (including time available on the frequency) to consider alternatives or unplanned actions. Provision of traffic does not clearly identify who is responsible for separation.
2.12.6 Those who publish the rejected landing procedures should in fact be responsible for segregation or separation, not the pilot nor the controller. Consider the descent on an instrument approach regarding terrain. It is not the pilot nor the controller that are responsible for the path and altitudes published on the instrument approach chart reference separation from terrain. The pilot is required to follow the procedure (unless executing command authority for the safety of the flight). The controller takes action to warn the pilot if a significant deviation from the approach procedure is observed, but is not using a radar standard, etc for separation from terrain.
2.12.7 The rejected landing procedure is not designed to permanently ensure segregation or separation. The rejected landing procedure is to allow the aircraft to safely maneuver to a position where the controller can resume responsibility for separation of the aircraft.
2.12.8 The objective of achieving independent rejected landing procedures is still being investigated. There will be a continuing need for dependent rejected landing procedures. This may impose certain responsibilities on the pilots or controllers. However this responsibility must be reasonable.
2.12.9 It is not reasonable for pilots or controllers simply to observe the rejected landing (for example the pilots being given mutual traffic.) The best example found is a quote from an FAA Air Traffic Bulletin article on visual separation dated Summer 2000:
“Visual separation is not watching one aircraft miss another, or issuing traffic and watching the result and hoping it works … this is visual observation” and “visual separation is where you place aircraft on a certain path where you can monitor their progress and assure that they are in no danger of colliding, and maintaining this vigilance until lateral, vertical or pilot separation is in place.”
In the case of dependent rejected landings procedures, whether it is the pilot or controller who applies visual separation, it is not to be an exercise in visual observation but one where the rejected landing procedure has predetermined the path and the pilot and/or controller monitor compliance visually.
2.12.10 Just as the pilot has command authority for the safety of flight, the controller should be able to modify the rejected landing procedure if there is an operational need. However it is expected that the controller will provide sufficient notice to the pilot to permit preparation for the manoeuvres. It is likely the controller would be responsible for separation if such a change is made.
2.13 Existing Policy and LAHSO
2.13.1 Existing IFATCA policy is for Simultaneous Operations on Intersecting/Converging Runways. The inclusion of converging runways (as well as intersecting runways) in the title means that all LAHSO is included under this title, even though LAHSO is not specifically mentioned.
2.13.2 The main safety concerns with LAHSO, that is the consequences of not holding short and the consequences of a rejected landing, are covered under existing policy paragraph d:
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“that specific procedures are introduced that will ensure that the approach sequence to each runway can be managed in such a way that each aircraft will be able to continue its approach, landing and possible missed approach safely”. |
However this paragraph is so generic that it could be used for any approach operations at an airport, including parallel runways.
2.13.3 If LAHSO has any special requirements or is not to be included under this policy then LAHSO policy must be explicitly stated.
2.13.4 The study of LAHSO has identified the USA requirement that LAHSO not be implemented unless there is an operational need. This approach seems applicable to LAHSO, SIRO and other operations designed to increase capacity safely but do so by reducing safety margins. For example, sequential operations can never meet at the intersection/overrun – only simultaneous operations can potentially meet.
2.13.5 The study of LAHSO has identified the USA use of rejected landing procedures. Rejected landing procedures have only been briefly introduced in this paper, and there are additional requirements for the USA rejected landing procedures, for example the point from which the rejected landing is initiated.
2.13.6 The issue of dependent segregation has also been discussed, and highlighted a need for policy. It is important that there be segregation or separation (not just traffic information) and responsibilities must be defined.
2.13.7 Existing generic policy on simultaneous runway operations would benefit from adding policy on only when needed, rejected landing procedures and dependent segregation.
2.14 Acceptability of LAHSO
2.14.1 During the discussion considering the operation of LAHSO, strong opinions were expressed in the Technical and Operations Committee (TOC) that due to the uncertainty regarding failure to hold short, and the problems in handling rejected landings that LAHSO should not be considered acceptable to IFATCA. Further details as described below.
2.14.2 A range of opinions were expressed. Some considered that LAHSO is in principle unsafe and should not be permitted at all. Others acknowledged that it might be possible to find conditions under which LAHSO is acceptable, however were concerned that any acknowledgment that LAHSO might be safe in some cases would result in inappropriate implementations of LAHSO. Others considered that safe LAHSO operations can be designed.
2.14.3 There was concern expressed that LAHSO is a procedure solely for expedition, and that expedition might be given priority over safety and orderliness. Related to this was a concern that need justified the expedition, rather than a concept that a procedure was either safe or not safe at all times irrespective of need.
2.14.4 There was concern about the lack of international standards including separation standards, and that ATC procedures should be based on separation and not segregation. Segregation, like other procedures, can be inappropriately applied and so concern was raised that any acceptance of segregation would increase the possibility of inappropriate segregation procedures.
2.14.5 Concern was raised over responsibilities for separation ( the controller, pilot or designer) in the case of rejected landings, and if the application of a separation standard is even possible in cases such as dual rejected landings.
2.14.6 Evidence was quoted about serious problems with initial implementations of LAHSO, including incidents from the USA, Australia and Europe. For example, LAHSO was used at Zürich, Switzerland until a serious incident caused the procedures to be stopped on regulatory orders. The UK regulator authority has a similar position against LAHSO (except for some helicopter operations) and has not approved any UK carrier to participate in LAHSO, even passively. Significant changes in procedures have occurred in USA and Australia in response to the incident history nevertheless a significant number of international organizations still oppose LAHSO.
2.14.7 Concern was expressed that LAHSO does not “fail safe” – that is when procedures fail they fail in an unsafe state. That is, two aircraft are essentially pointed at each other and that a simple failure results in very serious consequences.
2.14.8 The opinion was expressed that IFATCA should recommend that airport designers should implement acceptable runway layouts, for example parallel runways instead of converging runways.
2.14.9 Given the range of opinions, it was not possible for TOC to formulate policy.
2.14.10 In order to not lose information and so to progress work on simultaneous runway operations, this paper is presented by EVP Technical as an information paper.
Conclusions
3.1 Definitions for SIRO, LAHSO, and dependent and independent runway operations should be included in the IFATCA manual and be used in future to assist in discussion of this subject. Further discussion is needed on the appropriateness of segregation.
3.2 IFATCA policy on SIRO and converging runway operations remains applicable, however additional generic policy on SIRO and converging runways operations should be considered:
a) There must be a demonstrated operational need for simultaneous operations. Simultaneous, instead of sequential operations, reduce the safety margins and so should not be used unless there are demonstrated operational benefits. The USA LAHSO procedures give an example of meeting an operational need.
b) Airports must be individually authorised for simultaneous operations. The safety of simultaneous airport operations depends on the airport environment, the runway configuration in use and the types of operations. The use of simultaneous operations therefore must be approved for each airport and result in publication of approved runway configurations, operations and procedures.
c) Rejected landing procedures must be published before using simultaneous runway operations. Rejected landing procedures must provide segregation or separation from obstructions and all other operations permitted simultaneously. Provision of traffic information alone at controlled aerodromes is not sufficient.
d) If the rejected landing procedure is dependent, then pilot and/or controller responsibilities for separation must be specified in the procedure. It is not acceptable to have any ambiguity as to who is responsible for separation in dependent operations. It is not acceptable to expect visual observation to replace visual separation.
3.3 IFATCA should make explicit reference in policy regarding LAHSO, however further discussion is required before an IFATCA position on LAHSO can be stated.
Recommendations
4.1 It is recommended that this paper be accepted as information material.
Last Update: September 29, 2020