PROPOSED HORIZONTAL LAYOUT FILLET DESIGN FOR ENTRANCE/EXIT TAXIWAYS

Transcription

1 PROPOSED HORIZONTAL LAYOUT FILLET DESIGN FOR ENTRANCE/EXIT TAXIWAYS INTRODUCTION The Zelienople Airport Authority (ZAA) has commenced engineering activities for the rehabilitation of Runway to a length and width that is more suitable for actual and projected aviation operations. In rehabilitating Runway 17-35, parallel Taxiway A will have to be modified and extended. The modifications shall involve the use of FAA criteria for Entrance Taxiways and Exit Taxiways (Advisory Circular 150/ A, Sections 408 and 409). The placement of taxiway entrances and exits is a required component of the runway rehabilitation and is discussed in a separate narrative. However, in determining the proper alignment of the affected taxiways, pavement geometrics must also be considered. In the Advisory Circulars, pavement geometrics for taxiway fillets vary drastically depending on design aircraft, length of curve, radius of curve, etc. The purpose of this narrative is to determine and provide rationale for proposed taxiway fillet geometrics of all taxiway segments incidental to the Runway rehabilitation. The reasoning for the proposed designs shall be taken from FAA design criteria in conjunction with current airport data. DETERMINATION OF TAXIWAY DESIGN GROUP (TDG) The first step in determining pavement fillets is to determine the taxiway design group (TDG). In AC 150/ A, Section 401, pavement fillets are determined by the undercarriage dimensions of an aircraft, most commonly by the Main Gear Width (MGW) and the Cockpit to Main Gear Distance (CMG). These two critical dimensions help define the aircraft s taxiing method and steering angles. The FAA has provided various tools to assist in determining the proper TDG ( and recommends using the following alternatives (in order of priority): 1. Use Appendix 1 of AC 150/ A to access the FAA Aircraft Characteristic Database, locate your design aircraft and simply read the associated TDG. 2. Determine the CMG and MGW of the design aircraft from aircraft manual or other source, then use Table 4-11 and Figure 4-16 in AC 150/ A. 3. Utilize the design tool spreadsheet located on the FAA s website to determine the TDG by inputting various known dimensions of the critical aircraft. Since Option 1 is most recommended, it was used to determine the TDG as follows: 1. The design aircraft was taken from Table 1 below, from the Final Runway Feasibility Study prepared for Zelienople Airport Authority by others. According to this chart, the Cessna Citation CJ3 is the highest demand of the jet aircrafts utilizing the Zelienople airport. However, airport management has determined that the Cesna Excel/XLS is the preferred design aircraft.

2 Table 1 - Critical Design Airplanes 2. The FAA Aircraft Characteristic Database was then accessed, the Cessna Excel/XLS and the Cessna Citation CJ3 were located, and the associated TDG found to be TDG-2 for both cases. TAXIWAY FILLETS SELECTION Once the Taxiway Design Group was determined to be TDG-2, the pavement fillets could be designed. Since the proposed alignment only contains right-angled turns, only 90 degree fillets were explored for design. AC 150/ A provides Table 4-5 for TDG-2 fillet dimensions with accompanying Figure 4-13 for a right angled turn. These pages have been provided as attachments to this narrative for the reader s reference. It is important to note here that Table 4-5 is considered applicable to standard intersections. However, exit and entrance taxiways are commonly referenced as non-standard intersections. AC 150/ A, Appendix 8 Taxiway Fillet Design, Section A8-3, states that, where taxiway turns are close together such that the L-1 tapers overlap, this is an indication that the design airplane would not fully straighten before the second turn. This type of turn is referred to as nonstandard and requires alternate dimensions. Since the L-1 tapers will indeed overlap in the taxiway entrances and exits for Runway 17-35, non-standard dimensions were required. These nonstandard dimensions can be found in Table 4-12 of the AC and accompany Figure 4-17 and Figure 4-19 (all attached to this narrative for reference). Therefore, using non-standard dimensions from Table 4-12 for TDG-2 fillets and following Figures 4-17 and 4-19 for reference, standard details were created for the Runway entrance and exit taxiways. These details have been attached to this narrative as Exhibit A. CONCLUSION After thorough review of Advisory Circular design criteria and existing data for the airport, the proper and optimal taxiway fillets for Runway can be determined. By following the recommended FAA procedure, the airport s taxiway design group can be stated as TDG-2. From there, non-standard fillet dimensions were used to create the proper geometrics for the taxiway entrances and exits to Runway

3 ATTACHMENT 1 EXCERPTS FROM AC 150/ A

4 9/28/2012 AC 150/ A R-FILLET R-CL R-OUTER W-0 W-1 W-2 L-1 NOTE: RADII SHOWN ARE NOT CONCENTRIC. L-2 L-3 LEGEND: TAXIWAY TURN C L : MAIN GEAR OFFSET: NOSE GEAR OFFSET: Note: Offsets are shown in one direction, but offsets, and therefore fillets, are symmetrical. Figure Taxiway turn - 90 degree delta 133

5 9/28/2012 AC 150/ A FAA web site at are available in DXF format on the FAA web site at: W-0 W-3 RUNWAY TO TAXIWAY SEPARATION LINE OF SYMMETRY CENTERED BETWEEN RUNWAY AND TAXIWAY CENTERLINES R-OUTER R-CL W-0 W-1 W-2 L-1 L-2 L-3 Figure Entrance taxiway 141

6 9/28/2012 AC 150/ A RUNWAY TAXIWAY Figure Right-angled exit taxiway (2) High Speed Exits. Figure 4-18 illustrates a standard high-speed exit taxiway with a 30-degree angle of intersection. This figure and other drawings in DXF format showing common combinations of ADG, TDG, and runway to taxiway separation distance are available on the FAA web site at: The radius of the exit from the runway should always be 1500 feet (457 m), as a pilot would not be able to discern the difference between a smaller radius and that of a standard high-speed exit, possibly resulting in excessive speed in the turn. Use Table 3-6 for an efficient high speed exit taxiway when it is necessary to include a curve for operations where the aircraft must taxi in the direction opposite from landing. In such a case, use the greater dimension based on ADG or TDG. If a back turn is necessary when the runway to taxiway separation is less than shown in Table 3-6, it is necessary to decrease the initial exit angle and/or use a radius that will require a nose gear steering angle of more than 50 degrees for longer aircraft and to increase pavement fillets. (See paragraph 406.b(1) for guidance on fillet design.) Such sharp turns may require locked wheel turns and/or differential engine thrust and result in excessive tire wear. Note that in all cases the fillet for the reverse turn is designed considering that the exit taxiway is one way. When runway capacity needs justify the additional cost, high visibility taxiway centerline lights can be added and the exit taxiway widened by doubling the TESM for the entire exit taxiway or by tapering the TESM from double at the intersection with the runway to normal at the intersection with the parallel taxiway. These design enhancements will increase pilot acceptance of an exit. They will require modeling all the critical combinations of CMG, MGW, and TESM for the TDG. Do not co-locate opposite direction high speed exit taxiways as shown 145

7 AC 150/ A 9/28/2012 Table 4-5. Standard intersection details for TDG 2 TDG 2 Dimension (See Figure 4-13, Figure 4-14, and Figure 4-15) Δ (degrees) W-0 (ft) W-1 (ft) W-2 (ft) L-1 (ft) L-2 (ft) L-3 (ft) R-Fillet (ft) R-CL (ft) R-Outer (ft) Note: Values in the table are rounded to the nearest foot. 1 foot = meters. Table 4-6. Standard intersection details for TDG 3 TDG 3 Dimension (See Figure 4-13, Figure 4-14, and Figure 4-15) Δ (degrees) W-0 (ft) W-1 (ft) W-2 (ft) L-1 (ft) L-2 (ft) L-3 (ft) R-Fillet (ft) R-CL (ft) R-Outer (ft) Note: Values in the table are rounded to the nearest foot. 1 foot = meters. 136

8 AC 150/ A 9/28/2012 Table Dimensions for runway entrance/exit taxiways (where the two 90-degree turns are nonstandard) Dimension (see Figure 4-17) Runway Centerline to Taxiway Centerline Distance TDG W-0 (ft) W-1 (ft) W-2 (ft) W-3 (ft) L-1 (ft) L-2 (ft) L-3 (ft) R-Fillet R-CL (ft) R-Outer b. Configuration. The standard design of a runway entrance taxiway is at a right angle to the runway at the end of a runway where the threshold and beginning of takeoff coincide. Intersection angles of other than 90 degrees do not provide the best view of the runway and approach for a pilot at the holding position. A displaced threshold may require the holding position to be located along the parallel taxiway due to a need to keep aircraft out of the Precision Obstacle Free Zone (POFZ) and approach surfaces. This can lead to runway incursions when pilots do not expect to encounter the holding position away from its traditional location. The centerline radius and minimum fillet dimensions should comply with Table 4-3 and the subsequent seven tables for TDG 1A, 1B, etc., respectively. The outer edge of an entrance taxiway must be curved. When multiple parallel taxiways extend to the end of the runway, the outer edge of the outer parallel taxiway must be curved. c. Design. Do not design entrance taxiways to provide direct access from an apron, as shown in Figure 4-2. Instead, configure taxiways as shown in Figure 4-3. Design the entrance taxiway width based on Table 4-2. The curved outer common edge, as discussed in paragraph 408.b above, provides a visual clue to help pilots avoid landing on a parallel taxiway. Each entrance taxiway should have its own taxiway designator, markings and elevated signage. Existing entrance taxiways with non-standard design elements are to be corrected in accordance with this standard during the next capital project opportunity at that location. Designated hotspot locations should receive priority attention. Ideally, the length of the entrance taxiway should allow the longest fuselage of a TDG, at the hold line, to fully line-up perpendicular to the 142

9 ATTACHMENT 2 - EXHIBIT A: RUNWAY REHABILITATION ENTRANCE/EXIT TAXIWAY DETAILS

10 PAVEMENT TO BE REMOVED 50' 75' 190' 190' 75' 50' 50' PAVEMENT TO BE REMOVED ' 27' 17.5' 17.5' 27' 50' R-OUTER = 82' 17.5' R-OUTER = 82' 120' 120' R-OUTER = 82' 28' (MODIFIED FOR EXIT FUNCTION) 17.5'(MIN. 110' 28' RUNWAY ' 75' 100' 100'75' 240' REQUIRED FOR ENTRANCE) 28' RUNWAY ' REVISIONS DATE TYPE BY CHK mdbiagio 10:46:38 AM 3/26/2019 G:\(2017)\ Zelienople Municipal Airport - Shift and Rehabilitate Runway\PROJPLT\DETAILS.dgn PAVEMENT TO BE REMOVED MTEN MODIFIED TAXIWAY ENTRANCE DETAIL TEN TAXIWAY ENTRANCE DETAIL ' 17.5' 27' 120' 110' 240' 28' RUNWAY TEX TAXIWAY EXIT DETAIL -- 50' 75' 190' 150' R = 55' 75' 100' 12.5' R-TURN = 65' RUNWAY ' TAR TAXIWAY TURNAROUND DETAIL -- 55' 100' EXHIBIT A - RUNW AY REHABILITATION: TAXIW AY DETAILS PREPARED BY: PREPARED FOR DRAWN: CHECKED: DATE: SCALE: ZELIENOPLE AIRPORT AUTHORITY 1859 ROUTE 588 ZELIENOPLE, PA PROJECT #: FIELD BOOK #: KLH SFZ APRIL 2018 AS NOTED 1 OF 1 SITUATE IN: FRANKLIN TOW NSHIP INC. BEAVER COUNTY, PENNSYLVANIA 806 LINCOLN PLACE, BEAVER FALLS, PA Z. AIRPORT SHEET NUMBER