smartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0 Posted (3 years 3 months 3 weeks 6 days 5 hours ago) and read 6151 times:
If Procedure Design gradient is assumed to be 3.3% (2.5% + .8%) unless stated to be higher which will be published, why is it then that for the 2nd segment climb for a two engine aircraft the climb gradient only needs to be 2.4%?
smartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Reply 1, posted (3 years 3 months 3 weeks 6 days ago) and read 6095 times:
Just to try and clarify my original question,
Hoping someone can clarify some info for me that I cannot seem to get my head around.
On a SID unless otherwise stated (which would be higher) we assume the PDG is 3.3% (2.5% + 0.8%). As per Pans Ops which states that the procedures 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 will give you 35ft clearance minimum.
EU OPS 1.495 states that an operator needs to clear all obstacles in the net take off flight patch by 35ft. My understanding is that this relates to the obstacles accountability area which may or may not include the 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/3rd and 4ft segment climbs in the event of an engine failure/loss. This depicts a minimum climb CAPABILITY for the various stages which need to provide a minimum of 35ft above all terrain in the path. In these climb requirements there is mention of a positive of the 1st, 2.4% of the 2nd and 1.2% for the 3rd and 4th. Is this just climb capability or does the aircraft need to actually perform this? For example on the 3rd segment it says a minimum capability of 1.2% which at 164 Knots would equate to 200ft/min, would we need to actually do this in the accel phase or is it ok that 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 is this. On a SID with a PDG of 3.3%. an aircraft with two engines needs to clear all obstacles by a minimum of 35ft.
EU Ops states that an operator needs to able to clear all obstacles in the net take off flight path by 35ft. I presume this is with one engine and would be any obstacle in the Identification area.
How different is the SID going to be in relation to any other path the aircraft can take in that area. The SID is minimum 3.3% and gives you 35ft clearance. For engine out the climb performance, the aircraft gives need to be a minimum of 2.4% BUT is still required to give you 35ft clearance over any obstacle in the ID area.
How do two different requirements with different protocol give you the same thing?. How would the path of a SID which needs 3.3% be all that different from the path followed with an engine out with a max of 2.4% gradient but still give you 35ft clearance, the same as the SID.
Mir From United States of America, joined Jan 2004, 22652 posts, RR: 55
Reply 2, posted (3 years 3 months 3 weeks 5 days 18 hours ago) and read 6063 times:
Quoting smartt1982 (Reply 1): On a SID unless otherwise stated (which would be higher) we assume the PDG is 3.3% (2.5% + 0.8%). As per Pans Ops which states that the procedures are based on all engines operating and that in the event of failure etc. an operator needs to come up with contingency procedures.
There you go. If the procedures are based on all-engines, then engine-inoperative numbers don't enter into it. The 2.4% is an engine-out number. You have to look at the SID, figure out whether you can make the climb gradient, and if not, don't accept the SID in a clearance.
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Actually the 2.4% is a certifcation requirement, the 3.3% is a min assumed operational missed approach gradient. It is up to the operator to check if they can make the required missed gradient of that airport if not an alternative procedure needs to be made in order to comply with terrain clearance requirements.
Not something that will be checked in a normal Sid clearance unless your flying a private pilot etc