SID Gradient Vs Engine Out

[pi3lot_1982]

Hoping someone can clarify some info for me that Icannot seem to get my head around.

On a SID unless otherwise stated (which would be higher) weassume the PDG is 3.3% (2.5% + 0.8%). As per Pans Ops which states that theprocedures are based on all engines operating and that in the event of failure etc.an operator needs to come up with contingency procedures. Normally a SID willgive you 35ft clearance minimum.

EU OPS 1.495 states that an operator needs to clear allobstacles in the net take off flight patch by 35ft. My understanding is thatthis relates to the obstacles accountability area which may or may not includethe SID but equates to an area presribed by EU/FAA ops.

Performance wise, in this case I am referring to the 737,there are certain criteria relating to requirements for 1st/2nd/3rdand 4ft segment climbs in the event of an engine failure/loss. This depicts aminimum climb CAPABILITY for the various stages which need to provide a minimumof 35ft above all terrain in the path. In these climb requirements there ismention of a positive of the 1st, 2.4% of the 2nd and 1.2%for the 3rd and 4th. Is this just climb capability ordoes the aircraft need to actually perform this? For example on the 3rdsegment it says a minimum capability of 1.2% which at 164 Knots would equate to200ft/min, would we need to actually do this in the accel phase or is it okthat the aircraft Is just capable? ie at my company we just accel and do not climb.

What confuses me and what I hope someone can help me with isthis. On a SID with a PDG of 3.3%. an aircraft with two engines needs to clear all obstaclesby a minimum of 35ft.

EU Ops states that an operator needs to able to clear all obstaclesin the net take off flight path by 35ft. I presume this is with one engine andwould be any obstacle in the Identification area.

How different is the SID going to be in relation to anyother path the aircraft can take in that area. The SID is minimum 3.3% andgives you 35ft clearance. For engine out the climb performance, the aircraftgives need to be a minimum of 2.4% BUT is still required to give you 35ft clearanceover any obstacle in the ID area.


How do two different requirements with different protocolgive you the same thing?. How would the path of a SID which needs 3.3% be all that differentfrom the path followed with an engine out with a max of 2.4% gradient but stillgive you 35ft clearance, the same as the SID.



I am confused



Any info would be greatly appreciated

[reynoldsno1]

Normally a SID willgive you 35ft clearance minimum.

Not so - the SID procedure design assumes a minimum 5m above the departure end of the runway and the minimum obstacle clearance is then essentially 0.8% of the track distance flown i.e. it is increasing all the time. The 35ft clearance is an aircraft performance requirement ISTR, not a procedure design requirement.

[paulsalem]

I can't speak to EU regulations, but I imagine the FAA is the same.

121 and 135 (airline and charter) are required to clear all obstacles by 35' in the event of an engine failure.

Since it's an emergency situation you do not need to follow an ATC clearance. The operator pays a company like APG who has obstacle data at each airport, and they construct a departure path (for emergency use only) that is the least onerous (allowing the highest possible takeoff weights). Most of the time the path is runway track, or even to follow a SID to a certain fix then climb in a hold.

This is known at Runway Analysis. Here are a couple videos on the subject, I hope that helps.