NECK / DTOP
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HALS / DTOP is a name for a special landing procedure that was tested from 1999 to 2004 at Frankfurt Airport in order to increase the landing capacity on the existing runways (RWY).
HALS is no longer used and all approach procedures are suspended, as this operational procedure has not proven itself in practice. At the end of 2008 and beginning of 2009, all navigational systems as well as the corresponding markings and lighting systems for runway 26L were removed.
The acronym HALS / DTOP means in full:
- HALS - High Approach Landing System - German: high approach landing procedure
- DTOP - Dual Threshold Operation - German: two threshold operation
The High Approach Landing System (HALS) was the first stage and the DTOP landing procedure the second stage of the HALS / DTOP project.
Overview
The initiator and inventor of the process was Deutsche Flugsicherung (DFS) and Fraport - the operating company of Frankfurt Airport. The HALS / DTOP landing procedure was unique worldwide in this form. HALS / DTOP was being tested by air traffic control at Frankfurt am Main Airport and was gradually introduced over the course of several years. A series of research programs ran parallel to the step-by-step introduction of two-threshold operation, including flight simulators . This landing procedure made a closer approach staggering possible without violating the ICAO safety standards due to the risk of wake vortices, since there was sufficient vertical distance (300 feet - around 90 meters) between the approach paths (see landing approach ) of the successive aircraft .
The existing runway (engl. RWY - Runway) RWY 25L in addition to their normal landing threshold (engl. THR - Threshold) a second, far offset threshold obtain (1.500 m) - with the fantasy name RWY 26L .
- Note: This procedure - to provide runways with a number slightly different from their direction - is also used for four parallel runways. At Los Angeles International Airport (LAX), for example, of four strictly parallel lanes (approach course: 249 °), the two on the left are referred to as RWY 25L and RWY 25R and the two on the right as RWY 24L and RWY 24R .
HALS - High Approach Landing System
HALS works with an offset threshold ( RWY 26L ), but only the offset threshold was active with HALS.
It was only in the second phase that the normal RWY 25L threshold was also active at Frankfurt Airport with DTOP in addition to the relocated threshold .
The HALS phase was used to acclimatize the air traffic control and to investigate the reaction of the pilots when approaching a widely offset threshold (1,500 m) and which safety-related problems could arise. The approach to the offset threshold ( RWY 26L ) was the only thing that directly affected the pilots during the new HALS / DTOP landing procedure in Frankfurt. All other procedural changes concerned air traffic control.
The marking of the RWY 25L (the beginning of the southern runway at operating direction 25, also known as operating direction west) was left unchanged. The offset threshold ( RWY 26L ) was also marked as a threshold and fired. During the approach, the pilot sees the normal threshold ( RWY 25L ) and the offset threshold ( RWY 26L ) at the same time . RWY 25L and RWY 26L each have their own glide slope lighting - PAPI - four red or white lights to the left of the touchdown point .
The two parallel runways (“Northern Runway” RWY 25R and “Southern Runway ” RWY 25L ) are 518 m apart and their length is 4,000 m each. In addition, the thresholds of the RWY 25R and RWY 25L are shifted 230 m from each other ( RWY 25R is 230 m further east, based on the approach baseline).
Due to the second threshold of the "southern runway", which has been moved back by 1,500 m, the RWY 26L only has a remaining length of 2,500 m - this is no restriction for the landing of the Airbus A330 (required landing distance: at 170 t landing mass 1,700 m), and is by no means a limiting factor for landings with the A320 Family . Nevertheless, approaches to the offset threshold ( RWY 26L ) with aircraft in the wake vortex category heavy were not planned - this includes the A330, for example.
At many airports there are high approaches to a runway, which then lead to a long landing - long before the HALS / DTOP landing procedure , without any specific operating instructions. Pilots of smaller aircraft that land on very long runways (for example, if the required landing distance of 200 m on a four-kilometer runway) is to obtain approval from air traffic control for a long landing so that they do not have to taxi so far to their parking position. While air traffic control can ask pilots of smaller aircraft to make a long landing in order to accelerate the flow of traffic, for example if this shortens the taxiway on the runway to the next branching taxiway.
Trial stage 1
Stage 1 of the test was the proof of the feasibility of the HALS / DTOP landing procedure in daily flight operations while maintaining the ICAO relay values as well as the pilots and air traffic controllers getting used to the changed situation. Stage 1 of the HALS / DTOP testing was successfully completed in summer 2001. The southern runway was then operated with the normal and offset sleeper active at the same time. In the test phase (1999–2004), 4,000 landings were made on the RWY 26L . The joint project two-threshold operation was funded by the federal government as part of the Aviation Research Program III (LuFo III).
DTOP - Dual Threshold Operation
The DTOP landing procedure (the second stage of HALS / DTOP) was the operation of two landing bumps on one runway. DTOP was introduced in addition to HALS - this meant that the staggering advantages of HALS were retained and the flexibility of conventional flight operations should also be added.
DTOP is an instrument landing procedure for increasing the capacity of an airport by reducing the wake vortex stagger distances with a new system of runway lighting. DTOP is an operating procedure on runways with two simultaneously active or fired landing bumps.
By shifting the runway threshold along the runway, the approach routes can be separated from each other more clearly, which means that the number of landings per hour can be significantly increased without extensive construction work.
The lighting of the runways, especially the thresholds, deviates from the ICAO standard.
- Note the name of the runways: The southern of the two tracks - RWY 25L / 07R - is at hints from west to east (operating direction 07, also known as Operation East because takeoffs and landings to the east done) as RWY 07R called , while it is referred to as RWY 25L for approaches from east to west (operating direction 25) . Only operating direction 25 - approaches to the RWY 25L - is of interest for two-threshold operations . As westerly winds prevail in Western Europe, most railways have an east-west orientation. The landings are mostly made to the west (against the wind). In Frankfurt there is around 80% operating direction 25 and 20% operating direction 07.
The RWY 25L / 07R has a double-fired runway 25L / 26L for approaches from the east . In total there are three sleepers on this track. Two landing bumps for approaches from the east, one for approaches from the west. The additional sleeper was only installed on the southern of the two parallel runways , but not on the northern parallel runway ( RWY 25R / 07L ).
Aircraft of the wake vortex category heavy land on the northern runway ( RWY 25R - only one sleeper at the beginning of the runway) , while aircraft up to the wake vortex category medium (and 290 ft) approach the offset sleeper of the southern runway ( RWY 26L ). Lighter aircraft approaching the south runway thus remain above the glide path and the wake vortices generated by the heavier aircraft approaching the north runway.
Due to the offset threshold, the sliding paths of the RWY 25R and RWY 26L have a vertical distance of 300 ft (approx. 90 m).
advantages
This landing procedure was expected to increase capacity on the existing runways at Frankfurt Airport. Because of the staggered spacing, the landing capacity of an airport is generally less than its take-off capacity. The higher approach path on RWY 26L should also reduce noise .
According to the regulations of ICAO Annex 14 , it is not permitted to use the two parallel runways independently of each other for flight operations. The parallel runways, which are 518 meters apart, can only be approached in stages so that the wake vortices generated during landing do not endanger each other.
The HALS / DTOP landing procedure makes the simultaneous operation on both runways - depending on the wind direction - much more flexible, which leads to an increase in the flight operations capacity of Frankfurt Airport without major expansion measures.
For independent operation and the simultaneous implementation of landings on two parallel runways, these must be at least 1,035 m apart according to the ICAO.
In normal operation, according to ICAO regulations, 5 nautical miles (NM) distance ( graduation ) between an aircraft of the wake vortex category medium and an aircraft flying ahead of the wake vortex category heavy must be maintained due to the wake vortices .
Due to the operation of the HALS / DTOP landing procedure, a wake vortex staggering of 5 NM remains. However, as the planes approach at different altitudes, this wake vortex staggering is no longer a limiting factor. Then only the radar graduation (because of the radar tracking - diagonal graduation) of the approaching aircraft has to be observed, which is only 2.5 NM.
safety
Despite the theoretical possibility, the "new" RWY 26L was only approved for landing approaches of aircraft with a maximum take-off weight (MTOW - Maximum Take-Off Weight) of up to 136 t (wake vortex category medium or light ). As an additional safety measure, the RWY 26L (the one with the offset threshold) was not operated when the runway was wet . Landings on the RWY 26L were possible up to CAT I. The weather minima for the HALS operation were (2000):
- Ground visibility : 8 km or more
- Cloud ceiling at least. Ft in 1600 to the line of sight from the outer marker to the threshold RWY 26L to ensure
- maximum tail wind 3 kt
During the testing phase, these requirements for the minimums were gradually relaxed.
The weather minima for the HALS / DTOP operation were:
- Runway Visual Range (RVR, ground view) at least 2400 m
- Main cloud base at least 600 ft above sea level Size
- maximum tail wind 3 kt
Only one landing threshold per runway was allowed to be used (i.e. either RWY 25L or RWY 26L ).