AMC 25.1587(c) Landing distances in abnormal configurations

ED Decision 2018/005/R

1.       Purpose

This AMC provides guidance and recommendations on how to determine and present in the aeroplane flight manual (AFM) landing distance information appropriate to abnormal configurations or following the loss of normal services, and guidelines on which failure cases should be considered.

2.       Related certification specifications

CS 25.125 Landing

CS 25.1585 Operating procedures

CS 25.1587 Performance information

3.       Background

When a failure occurs in flight, the flight crew has to analyse the consequences of this failure on the landing. Some failures cause an increase in the landing distance, which must be evaluated. A diversion may be necessary if the destination aerodrome runway is no longer appropriate due to the increased landing distance.

For the production of AFM data, the applicant considers all failures and assesses their probability of occurrence. In addition, the question of the best presentation of the relevant data should be addressed.

This AMC does not consider configuration deviation list (CDL) items or any unserviceabilities identified in the master minimum equipment list (MMEL) that are known prior to dispatch.

4.       Performance information

The applicant should determine information on the landing distance that is likely to be needed for landings in abnormal configurations, and following the loss of normal services. This information should consist of the horizontal distance from the point at which the main gear of the aeroplane is 50 ft above the landing surface to the point where the aeroplane comes to a complete stop for standard temperatures at each weight, altitude and wind within the operational limits established by the applicant for landing on a dry runway. This information should be established in accordance with CS 25.125(b)(4) and (5), CS 25.125(c)(1) and (2), CS 25.125(f) and with the following conditions:

(a)      The aeroplane is in the landing configuration appropriate to the failure case being considered;

(b)     A steady approach is maintained down to the 50-ft height, at not less than the recommended approach speed, and using the recommended approach procedure, appropriate to the failure case being considered. (See paragraph 5 below);

(c)      Changes to configuration, power or thrust, and speed are made in accordance with the recommended procedure appropriate to the failure case being considered; and

(d)     All deceleration devices with which the aeroplane is fitted, including reverse thrust, may be used during the on-ground part of the landing, to an extent dependent both on the characteristics of the aeroplane and on the recommended use of deceleration devices, provided that:

(1)     a practical procedure for their use has been established;

(2)     the controllability of the aeroplane during their use has been shown to be satisfactory (see paragraph 8 below); and

(3)     they would be available, and their use is recommended, for the failure case being considered.

5.       Operating procedures

It is intended that in deriving the landing distance of paragraph 4 above, which is required by CS 25.1585(a) to be included in the AFM, the applicant should use procedures that are generally based on the application of conventional stall and controllability margins. However, it is acknowledged that for failure cases, this is not always practical. Where the procedure uses less than the normal margin, this should be based on flight evaluation and stated in the AFM, along with advice on how this might affect the way the approach is conducted (e.g. reduced pitch manoeuvre capability and the ability to counteract wind shear). Nevertheless, for some configurations that cannot be easily flight-tested, a combination of simulation and analysis may be acceptable.

6.       Effect of failures on landing distance

The applicant should determine information on landing distances in abnormal configurations in accordance with the procedures appropriate to the abnormal configuration for single failures and combinations of failures provided in the AFM that:

(a)      have a probability of occurrence greater than approximately 10^-7; and

(b)     result in more than a 10 % increase in landing distance.

          If a procedure is included in the AFM for a failure case that:

(a)      has a probability of occurrence less than 10^-7; and

(b)     results in an increase in the landing distance of more than 10 %,

then information about the increase in landing distance should also be included in the AFM.

7.       Effect of overspeed and wet runway

The applicant should provide information on the separate effects of a 10-kt overspeed and of a wet runway.

Note: overspeed in the above context refers to speed in excess of the approach speed recommended for the abnormal condition, which itself may be greater than the normal approach speed.

8.       Deceleration devices

The applicant may include the use of deceleration devices during the on-ground part of the landing to the extent that directional control can be readily maintained during their use on a wet runway, with a crosswind component of not less than 10 kt from the adverse side.

9.       Data derivation and AFM presentation

The applicant may derive the performance information described in paragraph 4 from calculations that are conservatively based on the best available information, on simulation or flight test, or any combination of these. The recommended operating procedures discussed in paragraph 5 should be presented in a simple manner (e.g. as increments in the landing distance, or approach speeds). The effects of overspeed and a wet runway may be presented as generalised information that covers a variety of abnormal configurations.

[Amdt 25/21]