Aircraft Performance   


08.05.2014 | Post by Dan Boedigheimer

Declared Runway Distances

You have a scheduled flight from Waterbury-Oxford, CT (KOXC) to Palm Beach, FL (KPBI) with 4 passengers. It is warm day with a low stratus cloud layer producing rain at the airport.

Based on the flight plan you want to depart at or near gross weight to have sufficient fuel reserves for any possible delays into KPBI with the forecast convective activity in south Florida. The current METAR [METAR KOXC 281952Z 18011KT ½SM R OVC009 28/23 A3007] gives you the pertinent weather data to begin your aircraft performance calculations.

You are initially concerned you may be runway limited with a reflective wet runway. Making corrections to your numbers for a 10 knot headwind, 0.8% down slope, and wet runway you calculate takeoff field length of 5650 feet. A quick glance at the Terminal Procedure Publication (TPP) airport diagram shows you have 5800 feet of runway available.

You ask your fellow crewmember Jack that considering his technique of using a rolling takeoff does he feel comfortable with a takeoff field length within 150 feet of the published available runway. He says he is more concerned about the published 5300 foot Accelerate Stop Distance Available (ASDA) on Runway 18. This catches you off-guard and you silently wonder what he is talking about. If you limit your takeoff weight to meet a 5300 foot runway limitation you will not be able to make the trip non-stop.

You double check the TPP chart and see that there is a displaced threshold on runway 18, leaving only 5000 feet available for landing, but no notation for a limited runway length for takeoff.

Similarly, the Jeppesen chart shows 5800 feet available on the plan view with the TAKE-OFF usable length cell blank. You triple check your flight management computer database which also shows 5800 feet available for runway 18.
With all this information you go back to Jack and ask him where he got the information that runway 18 has a published 5300 foot ASDA. He shows you on his iPad the Airport Facility Directory that Runway 18 has a published Takeoff Run Available (TORA) of 5800, Takeoff Distance Available (TODA) of 5800, and an ASDA of 5300 feet.

A review of the Aeronautical Information Manual (AIM) 4-3-6 Use of Runways/Declared Distances shows that Jack just may be on to something.

“Declared distances for a runway represent the maximum distances available and suitable for meeting takeoff and landing distance performance requirements. These distances are determined in accordance with FAA runway design standards by…subtracting from that sum any lengths necessary to obtain the standard runway safety areas, runway object free areas, or runway protection zones. As a result of these…subtractions, the declared distances for a runway maybe…less than the physical length of the runway as depicted on aeronautical charts and related publications, or available in electronic navigation databases provided by either the U.S. Government or commercial companies.”

The AIM section continues to go into detail that the ASDA would be limiting factor when flight planning. “The minimum distances required for takeoff and landing obtained either in planning prior to takeoff or in performance assessments conducted at the time of landing must fall within the applicable declared distances before the pilot can accept that runway for takeoff or landing.”

Although not convenient, the Airport Facility Directory, or other publication that publishes TORA, TODA, and ASDA, needs to be referenced during your preflight planning. As we noted neither government TPP or Jeppesen publishes TORA, TODA, and ASDA on their airport diagrams. Similarly, your flight management computer database most likely does not include that information either. Commercial runway analysis products like the one produced by the Aircraft Performance Group (APG) does include TORA, TODA, and ASDA information and the software considers that data when calculating maximum weights.

CONTACT

Dr. Dan Boedigheimer
Director of Instructional Design
Advanced Aircrew Academy
Email: dboedigheimer@aircrewacademy.com
Web: www.aircrewacademy.com
Twitter: @AircrewAcademy

For more information about Dan Boedigheimer visit our Experts page

 


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