AMC 25.143(b)(4) Go-around Manoeuvres

• ED Decision 2020/024/R found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

AMC 25.143(b)(4) Go-around Manoeuvres ED Decision 2020/024/R 1. Background When full thrust or power is applied during a go-around, an excessive level of performance (rate of climb, accelerations) may be reached very quickly, and make it difficult for the flight crew to undertake all the actions required during a go-around, especially in an environment that is constrained (due to Air Traffic Control instructions, operational procedures, etc) and rapidly changing. This level of performance can also generate acceleration levels (in particular, forward linear accelerations) that could lead to spatial disorientation of the flight crew (e.g. a somatogravic illusion), in particular when combined with reduced visibility conditions and a lack of monitoring of primary flight parameters, such as pitch attitude. Accidents and incidents have occurred during or after go-arounds where somatogravic illusions have led flight crews to make inappropriate nose-down inputs, leading to an aircraft upset, a loss of control or a deviation from the normal go-around flight path, and in some cases, controlled flight into terrain with catastrophic consequences. Other accidents resulting in loss of control were due to excessive pitch attitudes combined with the flight crew’s inadequate awareness of the situation. The risk is higher on aeroplanes that have a large operational range of thrust to weight ratios, in particular for twin-engine aeroplanes and those with long-range capabilities. 2. Criteria for assessing the go-around manoeuvre risk with respect to somatogravic illusions and the flight crew workload 2.1 Somatogravic illusions It is considered that the risk of a somatogravic illusion is high when encountering high longitudinal acceleration or combined high values of pitch attitude (nose-up), pitch rate and longitudinal acceleration, associated with a loss of outside visual references. 2.2 Workload In order to provide sufficient time to the flight crew to manage its tasks, and therefore keep their workload at a reasonable level, longitudinal acceleration and vertical speed may need to be constrained. The assessment of the workload should be performed considering the basic workload functions described in [Appendix D](#_DxCrossRefBm1709820808) of CS-25. 2.3 Risk assessment and mitigation means There are no scientifically demonstrated aeroplane performance limits to ensure that the risks of somatogravic illusions and excessive workloads remain at acceptable levels. However, the following criteria should not be exceeded during a recommended go‑around manoeuvre: — a pitch rate value of 4 degrees per second, — a pitch attitude of 20 degrees nose-up, — an energy level corresponding to either: — a vertical speed of 3 000 ft/min at constant calibrated airspeed, — a climb gradient of 22 % at constant calibrated airspeed, or — a level flight longitudinal acceleration capability of 7.8 km/h (4.2 kt) per second. Note 1: these boundaries should not affect operational performance, as they are considered to be beyond the operational needs for a go-around. Note 2: the numbers above should not be considered as hard limits, but as a reference only. Design mitigation means should be put in place in order to avoid exceeding these criteria and reduce the risk at an acceptable level. These means should: — provide a robust method to reduce the risk identified, and — be used during recommended go-around procedures. A reduced go-around (RGA) thrust or power function is considered to be an acceptable means of mitigation (refer to Chapter 4 below). Alternatively, exceeding any one of the above criteria should be duly justified by the applicant and accepted by EASA. 3. Go-around evaluation Go-around manoeuvres should be performed during flight testing in order to verify, in addition to the controllability and manoeuvrability aspects, that the flight crew workload and the risk of a somatogravic illusion are maintained at an acceptable level (for an acceptable level of risk of a somatogravic illusion, refer to Chapter 2.3 of this AMC). The go-around manoeuvres should be performed with all engines operating (AEO) and for each approved landing configuration as per the recommended AFM go-around procedure: — with the most unfavourable, and practicable, combination of centre of gravity position and weight approved for landing, — with any practicable combination of flight guidance/autothrust-throttle/autopilot to be approved, including manual, — with a level-off altitude 1 000 ft above the go-around initiation altitude. 4. Implementation of a reduced go-around (RGA) thrust or power function The applicant may provide an RGA thrust or power function for use when the flight crew initiates a go‑around. The function should operate with any practicable combination of the flight guidance/autothrust‑throttle/autopilot modes to be approved for operation, including manual modes. This function should limit the engine thrust or power applied and maintain the performance of the aeroplane (in particular, its rate of climb) at a level that: — is not less than the minimum required performance compatible with the operational needs and the flight crew workload during this phase; and — reduces the flight crew’s risk of suffering a somatogravic illusion. This thrust or power reduction function may be available either through aircraft system automation or manually. In any case, acceptable procedure(s) should be available in the aeroplane flight manual (AFM), and the recommended go-around procedure should be based on the RGA thrust or power function. Note: When a reduced go-around thrust or power function is provided, the applicant should still use the most critical thrust or power within the range of available go-around thrust or power when showing compliance with the CS-25 specifications. 4.1 Design target RGA functions with a design target of a 2 000 ft/min rate of climb capability have been accepted by EASA. 4.2 Cockpit indications and information to the flight crew In automatic mode, information that thrust or power is reduced in the RGA mode should be indicated to the flight crew. In manual mode, the thrust level tables should be made available to the flight crew. 4.3 Evaluation An evaluation of the go-around manoeuvre with the RGA thrust or power function should be conducted following the recommendations of Chapter 3 above. 4.4 Thrust or power mode command It should be possible for the flight crew, at any time and without any delay, to select and apply the full go‑around thrust or power. The applicant should provide specific procedures for which full thrust or power may be required, such as wind shear alert procedures, TCAS alert procedures, etc. 4.5 Engine failure during go-around with RGA thrust or power When an engine failure occurs during a go-around performed with active RGA thrust or power, if the required thrust or power from the remaining engine(s) to achieve an adequate performance level cannot be applied automatically, a warning alert to the flight crew is required to prompt them to take the necessary thrust or power recovery action. For non-moving autothrust-throttle lever designs or designs relying on manual thrust or power setting procedures, compelling flight deck alerts may be acceptable in lieu of automatic thrust or power recovery of the operating engine(s) to permit the use of maximum go-around thrust or power for compliance with [CS 25.121 (d)](#_DxCrossRefBm1709820672). The procedure for the recovery of the engine thrust or power setting must be demonstrated to be acceptable in terms of the detection of the situation by the pilot and the required actions in a high-workload environment. The following items should be evaluated: — the timeliness of achieving the minimum required performance; — flight crew awareness (indications, alerting…); — flight crew actions (commands); — the flight crew workload in general. 4.6 Performance published in the AFM for RGA thrust or power The climb performance required by [CS 25.119](#_DxCrossRefBm1709820701) (in a landing climb, i.e. with all engines operating) should be based on the actual RGA thrust or power available (applied by following the recommended AFM procedure). The climb performance required by [CS 25.121](#_DxCrossRefBm1709820672) (in an approach climb, i.e. with one engine inoperative) should be based on: — either the RGA thrust or power available, if no thrust or power recovery is implemented, — or the go-around thrust or power available after the application of the thrust or power recovery action (either automatically, or manually after an alert is triggered). For non-moving autothrust‑throttle lever designs or manual thrust or power setting procedures, compelling flight deck alerts may be acceptable in lieu of automatic thrust or power recovery of the operating engine to permit the use of maximum go-around thrust or power for compliance with [CS 25.121(d)](#_DxCrossRefBm1709820672). [Amdt 25/21] [Amdt 25/26]