Determining Safe Landing Distance

Air Safety Week,  June 19, 2006  

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In issuing its advance notice on June 7 of a new policy on landing distances, FAA indicated that a review of its own regulations, notices, and guidances revealed the following issues of concern:

* About 50 percent of the operators surveyed do not have policies for assessing whether sufficient landing distance exists at the time of arrival, even when conditions are different and worse than those planned at the time the flight was released.

* Not all operators that perform landing distance assessments at the time of arrival have procedures that account for runway surface conditions or reduced braking action reports.

* Many operators who perform landing distance assessments at the time of arrival do not apply a safety margin to the expected actual landing distance. Those that do are inconsistent in applying an increasing safety margin as the expected actual landing distance increased.

* Some operators have developed their own contaminated runway landing performance data or are using data developed by third party vendors. In some cases, these data are less conservative than the airplane manufacturer's data for the same conditions.

* Credit for the use of thrust reversers in the landing performance data is not uniformly applied and pilots may be unaware of these differences.

* Airplane flight manual landing performance data are determined during flight-testing using flight test and analysis criteria that are not representative of everyday operational practices.

* Wet and contaminated runway landing distance data are usually an analytical computation using the dry, smooth, hard surface runway data collected during certification. Therefore, the wet and contaminated runway data may not represent performance that is achieved in normal operations.

* Manufacturers do not provide advisory landing distance information in a standardized manner, but generally make landing distance performance information available for a range of runway or braking action conditions using various airplane deceleration devices and settings under a variety of meteorological conditions.

* Manufacturer-supplied landing performance data for conditions worse than a dry smooth runway is normally an analytical computation based on the dry runway landing performance data, adjusted for a reduced airplane braking coefficient of friction available for the specific runway surface condition.

Source: FAA

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