smartt1982
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SID PDG And 2nd Segment Climb

Thu Oct 11, 2012 5:34 pm

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%?

Am I reading that wrong?
 
smartt1982
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Posts: 226
Joined: Sat Nov 24, 2007 11:17 pm

RE: SID PDG And 2nd Segment Climb

Thu Oct 11, 2012 10:16 pm

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.







I am confused







Any info would be greatly appreciated
 
Mir
Posts: 19107
Joined: Mon Jan 05, 2004 3:55 am

RE: SID PDG And 2nd Segment Climb

Fri Oct 12, 2012 4:33 am

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.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
smartt1982
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RE: SID PDG And 2nd Segment Climb

Mon Nov 05, 2012 10:50 pm

Quoting Mir (Reply 2):



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

[Edited 2012-11-05 15:11:11]
 
Mir
Posts: 19107
Joined: Mon Jan 05, 2004 3:55 am

RE: SID PDG And 2nd Segment Climb

Tue Nov 06, 2012 4:24 am

Quoting smartt1982 (Reply 3):
Not something that will be checked in a normal Sid clearance

It should be, if there's a published climb gradient for the SID in question. If not, then your performance tables will probably tell you whether you can make the standard gradient or not.

Unless you're using a weight-based performance calculation program, in which case you don't have to worry about climb gradients so long as you're below the listed weight for the conditions.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
smartt1982
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Posts: 226
Joined: Sat Nov 24, 2007 11:17 pm

RE: SID PDG And 2nd Segment Climb

Tue Nov 06, 2012 6:11 am

Quoting Mir (Reply 4):

Apologies that's I was referring to cheers

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