I Introduction
Generally any multi-engine aircraft IFR capable, flying under IMC conditions with all engine performance can meet gradient capabilities published in missed approaches. Missed approach procedures are generally divided into the initial, intermediate and the final phase. Obstacle clearance requirements begin in the intermediate phase with a 30 metre (98 feet) clearance requirement. In the final phase, the obstacle clearance requirement becomes 50 metres (164 feet). The nominal climb gradient of a missed approach surface is 2.5%, however higher gradients may be required where obstacle clearance dictates. For older aircraft, particularly piston engined, aircraft compliance with the published missed approach may not be achievable when operating at or near the maximum certificated weight, high altitudes, high temperatures and engine out conditions.
Note: It is the responsibility of the operator to ensure that the aircraft does not conduct an approach at a weight and/or temperature that would not permit the aircraft to comply with the published missed approach procedure under normal “all engine” operational conditions. However under “engine out” emergency conditions compliance with the published missed approach procedures are not required.
II Regulatory Requirements
For aircraft operating above 5700 kg and in accordance with CASA CAO 20.7.1B, operators must comply with paragraph 14 of the order for the development of takeoff performance data and procedures. Sub-paragraph 14.2, states:
“ Procedures to be followed consistent with this Order, including procedures anticipating engine failure at any time between the commencement of take-off and completion of landing, must be specified in the Operator’s Operation Manual. The procedures so specified must be such that they can be consistently executed in service by flight crews of average skill and they must also be such that the take-off flight path with all engines operating is above the one-engine inoperative take-off flight path.”
As stated above, procedures anticipating engine failure at any time between the commencement of takeoff and completion of landing must be specified. This includes missed approaches with an engine out.
More specifically CAO 20.7.1B Paragraph 5.1(b) specifies that the landing weight of the aircraft must be reduced to meet amongst other things, the approach climb requirements in Paragraph 9. The approach climb performance requirements in Paragraph 9 stipulates that a gross gradient of 2.1% for twin-engine aircraft, 2.3% for three engine aircraft and 2.4% for four engine aircraft must be available for engine out performance. This is obviously the minimum climb certification requirement and is not related to any published missed approach procedures. Paragraph 12 makes reference to obstacle clearance however, it is limited to the context of takeoff and enroute.
III Guidance
Operators should develop engine out missed approach guidance for all instrument approach procedures where the aircraft would not be able to comply with the climb gradient performance requirements of the normal published missed approach procedures with an engine out.
It is the responsibility of the operator to ensure that, for any engine out missed approach procedures developed for use within their operation, sufficient aircraft performance studies have been developed to verify that the procedure provides adequate obstacle clearance throughout the flight path. When developing engine out missed approach procedures, operators may be limited to flight paths that would only allow for obstacle avoidance until sufficient altitude is achieved to land at the airport or fly to an alternate airport as required by the type of emergency.
The intent is to identify the best option or options for a safe lateral ground track and flight path to follow in the event that a missed approach or balked landing go-around is necessary with an engine out. To accomplish this, the operator may develop the methods and criteria for the analysis of engine-out procedures which best reflect that operator's operational procedures.
Specific Engine Out Missed Approach Procedures may be designed when compliance with the published missed approach procedure cannot be achieved during engine out operations. An alternative option to designing an engine out missed approach procedure may be, to use an existing EOSID for the nominated runway.
Note: If an operator chooses to use an EOSID in lieu of a published missed approach path, they must first demonstrate that the aircraft has the navigational capability to overfly the landing threshold, track runway centreline and overfly the runway end within the initial splay tolerance. Depending upon the operation type, the splay width can vary between 90 and 150 metres. Furthermore, the aircraft system and navigational capability needs to be assessed to ensure that the aircraft can be flown to the required tolerance in IMC and crew procedures must be in place to adequately address this manoeuvre.
In the absence of an Engine Out Missed Approach Procedure, the following provides sample methods of ensuring that obstacle clearance is maintained during an engine out missed approach.
1. Limit the approach climb weight and thus the landing weight such that the aircraft can comply with the published gradient (2.5% and above) at the operating minima with an engine out.
2. Limit the operating minima to a height where the missed approach equivalent gradient capability is assured at the typical mission landing weight.
3. In the diagram above, if the aircraft cannot comply with a 7.0% climb gradient engine out, the operator may choose a higher minima to enable a lower and compliable climb gradient. Some published procedures frequently provide alternate minima to accommodate different aircraft performance.
IV Missed Approach Procedure Assessment Considerations
Operators may accomplish such assessments generically for a particular runway, procedure, aircraft type, and expected performance, and need not perform this assessment for each specific flight. Operators may use simplifying assumptions to account for the transition, reconfiguration and acceleration distances following go-around (e.g., use expected landing weights, anticipated landing flap settings).
The operator should use the best available information or methods from applicable aircraft manuals or supplementary information from aircraft or engine manufacturers. If performance or flight path data are not otherwise available to support the necessary analysis from the above sources, the operator may develop, compute, demonstrate or determine such information to the extent necessary to provide for safe obstacle clearance.
The operational considerations should include:
1. Go-around configuration transitions from approach to missed approach configuration including expected flap settings and flap retraction procedures.
2. Expected speed changes.
3. Appropriate engine failure and shutdown (feathering if applicable) provisions, if the approach was assumed to be initiated with all engines operative.
4. Any lateral differences of the missed approach flight path from the corresponding takeoff flight path.
5. Suitable balked landing obstacle clearance, until reaching instrument approach missed approach or
enroute procedurally protected airspace.
6. Any performance or gradient loss during turning flight
7. Methods used for takeoff analysis, engine-out maximum angle climb, or other such techniques.
8. Operators may make obstacle clearance assumptions similar to those applied to corresponding takeoff flight paths in the determination of net vertical flight path clearance or lateral track obstacle clearance.
Source: CAAP 235-4(0), Guidelines for the Consideration and Design of: Engine Out SID (EOSID)
and Engine Out Missed Approach Procedures, Australian CASA, November 2006.
