One of my primary tasks in performance engineering is the design of Specific Runway Procedures for OEI operations, call them escape routes if you will, they go by many names. A vitally important follow-up of this procedure design is the advice to pilots, through operational policy stated in the Operations Manuals, of how they are to be executed, and when circumstances may permit 'breaking off' as posed in the original post. And YES, for each one I have designed and implemented, I have personally visited the relevant ATC unit to advise of our requirements in the event of engine failure. They have been very receptive to this, I have not had to deal with the Iranians Mutt.
Before any discussion on appropriate circumstances to break off from an OEI procedure, it is appropriate to briefly detail the considerations that I make in creating a procedure.
(1) The procedure must be such that the maximum possible weight for takeoff may be obtained after considering all obstacles UNTIL SUCH TIME as the aircraft reaches an area where normal (PANS-OPS) obstacle clearance exists. This is usually the MSA.
(2) Even though 3rd segment altitude will almost always be below MSA, obstacle clearance must be assured AT the 3rd segment altitude for the remainder of the procedure, thus avoiding obstacle assessment during the 4th segment. This will require tracking procedures, normally directed to a holding pattern, where further climb to MSA may take place. (The holding pattern may not be a published one, but one created to meet FAR25 requirements for the continued climb). The published procedure MUST continue until MSA is achieved, the pilot does not have the facility to assess obstacles.
(3) The entire procedure will be contained within the MSA coverage, normally 25 nm, and within the control zone of the departure airport.
(4) All procedures must avoid areas of known high traffic density, such as secondary airports, VFR operations areas, and the approach and departure paths from the originating airport.
(5) Where a SID requires a turn BEFORE a turning point specified in the OEI Specific Procedure, a second RTOW is created for OEI compliance with the SID. If the Actual TOW exceeds this 'SID compliant' weight, ATC must be advised and the alternative procedure used.
These are the basics of the criteria that I use, in my opinion any performance engineer providing a lesser degree of protection IS SIMPLY NOT DOING THEIR JOB.
All engine failures do not occur at night and/or in IMC, and in the Operations Manual write-up, the following is specified as acceptable circumstances for the pilot to 'break-off' from a Specific Runway Procedure -
(1) The procedure may not be terminated under any circumstances before Acceleration Altitude is reached, the aircraft is in the en-route configuration, and thrust reduced to Maximum Continuous, and either
(2) In VMC conditions by DAY, normal obstacle clearance to comply with the VFR rules is assured, or
(3) At night or in IMC, the aircraft has achieved sufficient altitude and within the required tracking tolerances to comply with a published Holding or Instrument Approach procedure, or
(4) At night or in IMC, the aircraft is at such an altitude to comply with the ATC Radar Safe Altitude and is receiving Radar vectors.
A bit lengthy, I'm sorry, but I sleep easier at night knowing that the crews using my procedures have full obstacle assurance all of the way to where they can resume normal operations with PANS-OPS protection, and have a clearly defined flight path offering the best foreseeable traffic avoidance.
A final word to pilots using visual obstacle assessment, it's not usually the obvious big obstacles that are 'gonna getcha', it's the little subtle ones.
Old Smokey