Can I accept a clearance containing a Standard Instrument Departure (SID) with a climb gradient that I can easily make on all my engines but can't make the required gradient on one engine inoperative?

If I can and I lose an engine on departure what should I do so I don't hit anything?

  • 5
    $\begingroup$ It depends, what regulations are you operating under? 91, 121, 135, etc.? $\endgroup$
    – Lnafziger
    Oct 25, 2015 at 3:06
  • $\begingroup$ Part 91. Are there regulations stating differently for 121/135? $\endgroup$
    – wbeard52
    Oct 26, 2015 at 3:25
  • $\begingroup$ They are indeed! Obstacle clearance requirements are different.... $\endgroup$
    – Lnafziger
    Oct 26, 2015 at 3:44

2 Answers 2


In Europe and I suspect the FAA has a similar rule, if you are flying commercially, you're allowed to fly the SID...but you need to have performance documentation on the specific airport with the specific A/C, engines and runway which will give you your climb gradient single engine and an escape route to follow in case of Engine failure. Most major company have a in house doc, others will use Flygprestanda, flightGuru etc... which will compile those calculations for you. The short answer then is :Yes you can, provided you can demonstrate that you know which path you'll followed on SE and what will be your performance.

Hope this helps ;-)


Depending on certain factors, you can accept a SID clearance knowing that you cannot make the required climb gradient with one engine inoperative (OEI).

The FAA Aeronautical Information Manual (AIM) 5-2-8 ODP and SIDs states this:

ODPs and SIDs assume normal aircraft performance, and that all engines are operating (AEO). Development of contingency procedures, required to cover the case of an engine failure or other emergency in flight that may occur after liftoff, is the responsibility of the operator.

This answer begs another question and what are some contingency procedures you can consider when accepting a SID when the required climb gradient is not possible with OEI procedures?

The FAA lists two possible places for this information:

  1. AC 120-91 - Airport Obstacle Analysis
  2. Instrument Procedures Handbook (FAA-H-8261-1) Chapter 1.

AC 120-91 talks about how runway analysis is used to comply with Part 121 / 135 obstacle climb requirement.

Instrument Procedures Handbook provides additional information on how OEI takeoff obstacle clearance requirements are different than TERPS requirements. Besides using runway analysis, there isn't a lot of additional information on contingency procedures.

Here are my contingency procedures in the preferred order

  1. Runway Analysis - Let an engineer figure out the maximum weight to takeoff and be able to climb above the obstacles
  2. Radar vectors - Once ATC issues the words "Turn left / right heading xxx°" they are equally responsible for terrain clearance
  3. See and avoid the terrain (VMC only) - If we can see the obstacles... hopefully we can miss them. Of course, mountains don't care if you can see them or not. They don't move.
  4. Obstacle Departure Procedures (ODP) using OEI calculations.
  5. SID using OEI calculations.

It would be great if others come up with a different set. I would love to see them. I will typically work through this listing and if I am taking off from an airport without radar services in IMC where I do not have runway analysis, I need to be able to make the ODP or the SID on OEI performance.


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