Standard Instrument Departures (SIDs) are designed in accordance with TERPS or Pans Ops and are designed for normal all-engine operations. These departure procedures at different places have different climb gradient requirements and are made keeping in view:
- Noise abatement
- Clearance from ground/terrain etc
Due to high terrain or elevation or performance or any combination of said factors it may not be possible for aircraft to always meet climb gradient requirement after engine failure. In such cases EOSIDs (Engine Out Standard Instrument Departures) are required to be followed.
SIDs provides the minimum performance considerations to meet the departure requirements assuming all engine operative whereas EOSIDs are based on aircraft performance in case of engine out.
Wondering Who Designs EO SIDs?
It is the responsibility of operator to develop Engine Out Takeoff procedure when and where required. This procedure is generally available in header of RTOW (Regulated Take-off Weight) Charts.
Engine Out SIDs design Considerations
- engine failure may occur at any point on departure
- maximum take off weight
- two or more engine out tracks may also be required depending on the area surrounding field
- aircraft performance
- path of EOSID should lead to a place where aircraft can plan landing or continue as to destination or alternation
Same like designing of normal SID there are various tolerances given in designing of EOSIDs also. Course guidance is as per the navigation system available and receivers stored on board. Consideration is given to GPS, DME/DME, VOR/DME and Inertial Navigation.
Other Considerations and Tolerances
- Ground Based Navaid Tolerances
- GNSS Tolerance
- Obstacle Considerations
- Obstacle Clearance during straight takeoff and turn
- Wind effect upon turns
- Loss of climb gradient during turn etc.
Engine out Missed Approach Procedure
In case of one engine failure generally all multi-engine aircraft should be able to meet the climb gradient requirements of published missed approach procedure but if they are unable to comply operators should develop engine out missed approach guidance for instrument approach procedure.
Following methods can be considered if Engine-out Missed Approach Procedure is not published:
- limit approach climb weight and thus the landing weight
- select higher altitude to initiate missed approach
Also Read : Minimum and Maximum Acceleration Altitude
Hope this article was useful. Feel free to comment your questions below.