Looking at the idea of using the OEI take-off procedure to permit operations at such weights that it is not possible to meet the MAP required obstacle clearance;
The OEI procedure starts at the end of the TODA and only considders obtsacles 60m + (wingspan/2) each side of track initially - not very far for a bizjet!. This area expands with increasing distance from the end of the TODA however, it is based on the idea that the pilot will be on or very close to the runway centerline at the end of the TODR.
The whole procedure is based on having the aircraft very accurately positioned and only 35ft above obstacles!
How can you acheive the same level of positional accuracy using the guidance provided (if any) during the MAP?
Basically I expect that you will have to re-survey the area each side of the OEI area and that will probably result in the obstacles that affect the MAP procedure being involved..........thus you may gain very little because I expect the procedure designer would have done their best to design the MAP that permits the lowest possible MAP gradients within the constraints of the MAP procedure.
Even if you do come up with your own single engine MAP procedure that has an advantage, ATC may object because the last thing they want is an aircraft with an emergency heading directly out of their protected airspace or directly at other traffic.........they will probably say - use lower weights so that you can meet the MAP requirements!
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ICAO 8168 says;
It is emphasised that a missed approach procedure which is based on the normal climb gradient of 2.5% cannot be used by all aeroplanes when operating at or close to maximum certified gross mass and engine out conditions. The operation of such aeroplanes needs special considderation at aerodromes which are critical due to obstacles in the missed approach area and may result in a special procedure being established with a possible increase in the DA(DH) or MDA(MDH).
That seems to indicate that the "special procedure" is permitted but I bet that the authorities would require such procedures to be approved and see above for obstacle clearance.
Regards,
DFC