High Speed Taxiways..

[air.surfer]

Voi che tutto potete.. mi trovate la definizione (ufficiale) di HiSpd Taxiway e la massima velocita' di utilizzo?
Possibilmente sulle EuOps...

Thanks.

[AlphaSierra]

a memoria 60kts


Accession Number : ADA098178

Title : High Speed Exit Taxiways.

Descriptive Note : Final rept.

Corporate Author : FEDERAL AVIATION ADMINISTRATION WASHINGTON DC SYSTEMS RESEARCH AND DEVELOPMENT SERVICE

Report Date : FEB 1981

Pagination or Media Count : 48

Abstract : The 'high speed' runway exit, also known as angled exit, is an airport/airside design feature which can make an important contribution to increasing capacity of the national air transportation system. The present standard angle exit offers a safe and clear reduction in landing time on the runway. However, except in a very few instances, this potential is not realized. Low utilization of high speed exits, although not conclusively shown, appears to be the results of operational use only where and when need exists to expedite runway clearance. Underutilization also appears to be motivated by desire to avoid any unnecessary risk or passenger discomfort. Realization of the capacity improvement potential of high speed exits is controlled by the character of the approach control system and the oeprating procedures currently used by pilots and controllers. Both the average and scatter of current interarrival intervals are sufficiently large to prevent any further benefits from reduced runway time. (Author)

Descriptors : *TAXIWAYS, GROUND LEVEL, HIGH VELOCITY, MANEUVERS, TRANSPORT AIRCRAFT, RUNWAYS, EXITS.

Subject Categories : MILITARY AIRCRAFT OPERATIONS
TERMINAL FLIGHT FACILITIES

Distribution Statement : APPROVED FOR PUBLIC RELEASE

[AlphaSierra]

1 Rapid Exit Taxiways
1.1 Design
ICAO define a high speed exit (or RET) as ‘a taxiway connected at an acute angle and designed to allow a landing aeroplane to turn off at higher speeds than are achieved on other exit taxiways’.
ICAO also recognises that the establishment of a single world-wide standard for the design of RETs has many advantages through pilots becoming familiar with their configuration.
Although there are a number of different designs throughout the world today (for example the FAA standard and other site-specific designs such as those to be found at Paris CDG), the most widely accepted and utilised designs that of ICAO. This design is widely implemented in Europe.
If the space between the runway and parallel taxiway is insufficient to accommodate the ICAO design RET, with its straight portion for deceleration before joining the taxiway system, then there is evidence to support the use of the FAA modified design. This design is widely used in the USA and compensates for the lack of a straight portion through a design which enables the aircraft to decelerate whist turning off the runway and joining the taxiway system. It is also wider than the ICAO exit, giving the aircraft more space to deviate from the taxiway centreline whilst turning off the runway and during deceleration. The use of exit angles smaller than the ICAO recommended minimum of 25° may also help in this situation, but aircraft may take longer to vacate the runway strip (particularly heavy aircraft).
Accepting that a consistent performance throughout Europe is the objective, then current best practice may be as follows.
1.1.1 Best practice
 With the exception of the final ‘stop end’ exit, all exits to be used by landing traffic should be RETs;
 Perpendicular exits may be retained for use by crossing traffic (e.g. Madrid, Paris CDG, Frankfurt);
 RETs should be designed in accordance with the provisions of ICAO Annex 14 (e.g. Madrid, Vienna, Munich, Frankfurt, Manchester), except that:
 where the distance between the runway and taxiway is insufficient to accommodate a straight section of sufficient length then:
- the exit angle could be reduced to less than 25° to a minimum of 20° (e.g. Paris CDG), or;
- the FAA ‘modified’ standard could be used (e.g. Miami, Orlando, Baltimore).
1.1.2 Rationale
The adoption of an already widely accepted and implemented design will result in the consistency of performance required to reduce the average ROT. Consistency of operation, which in turn promotes confidence in pilots and controllers, is vital in calculating and achieving a runway's potential (unconstrained) capacity.
Although there may be deficiencies in the ICAO standard RET, these are outweighed by the improvements in performance which come from familiarity with its design (e.g. low average ROTs are achieved at London Heathrow, despite known deficiencies in exit design).
If pilots are to be encouraged to exit at relatively high speeds, then it is important that the exit design is such to allow safe deceleration, preferably through the provision of a straight portion (as per ICAO) between exiting the runway and joining the main taxiway system.
1.2 Number and position of RETs
In order for benefit to be derived from the design of an RET, the runway has to equipped with a series of such exits, correctly positioned with respect to the performance characteristics of the expected or ‘design’ traffic mix. It has been estimated by the FAA that a 30m reduction in the distance between threshold and exit reduces ROT by 0.75 seconds. Conversely, the ROT of an aircraft which overruns an exit increases by 0.75 seconds for each 30m it has to travel to the next exit.
Guidance on the positioning and number of exits is given by ICAO (Annex 14 and the Aerodrome Design Manual). In particular, the Aerodrome Design Manual gives guidance on the positioning of exits on the basis of an extensive survey of the observed performance of traffic at 72 airports. These data do not, however, differentiate between dry and wet runways, and date back to 1980. Similar guidance on the positioning of exits is also given by the FAA in Advisory Circular 150/5300-13 (Airport Design), which appears to be based on more recent performance data and addresses both wet and dry runways.
In their methodologies, both ICAO and the FAA have separated aircraft into four performance bands, ICAO’s based on threshold speeds and the FAA’s on aircraft weight. However, these categories may not be suitable, and an airport may prefer to categorise traffic according to the performance of the ‘design’ traffic mix.
A better assessment of the correct position and number of exits could perhaps be obtained through a detailed examination of the performance characteristics of the actual fleet mix expected to use a runway. This examination should be done in cooperation with the (major) operators which will be using the runway. These operators would be in a position to provide detailed performance data based on the aircraft type, routes flown (and hence landing weights), operating procedures (e.g. brakes/reverse thrust) appropriate to the local conditions (e.g. weather, wind and runway gradient). Design and actual exit speeds also need to be considered (e.g. RETs designed in accordance with ICAO guidelines could theoretically be used at exit speeds of up to 50 kts, but in reality speeds are probably lower).
A third methodology for determining the optimum position and number of RETs is a computer simulation and optimisation model which has been developed in the USA by Virginia Technical University on behalf of the FAA. This tool is able to estimate the optimum position of RETs based on detailed aircraft performance data and the RET design. Results from this model indicate that:
 a 15% reduction in ROT is possible by reducing the exit angle from 30° to 20°;
 such ‘super acute’ exits could enable exit speeds of up to 68 knots (35m/s), enabling;
 ROTs in the order of 36-40 seconds.
However, the status of this tool (and the above results) is not known and an evaluation of its applicability in the European context would be necessary.
The overall aim would be to have a minimum number of exits, positioned so as to ‘capture’ the largest percentage of traffic, with the lowest average ROT for each category and for the overall runway.
Experience indicates that the number of RETs should be limited to a maximum of three (plus a standard exit at the runway end).
1.2.1 Best practice
 RETs should be positioned according to the predicted actual performance of the ‘design’ fleet mix, taking into account any achievable improvement in exit speed (e.g. Madrid, Paris CDG, Paris Orly, Manchester, Vienna);
 Such an assessment should be made in conjunction with the (major) aircraft operators, who should provide actual performance data relating to aircraft types, landing weights, operating practices and ambient conditions;
 The number of RETs should be limited to three, plus a standard exit at the runway end (e.g. Madrid, Barcelona, Munich, Athens/Spata).
1.2.2 Rationale
Performance of the design fleet mix in local ambient conditions is the critical factor in assessing the optimum position and number of RETs. This information can only be obtained locally, through a collaborative process involving the airport and aircraft operators.