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3.3% PDG and 2.4% One Eng Climb Gradient
Hi there,
Normal design gradient for SID has a minimum of 3.3% climb gradient, in the event of one engine out climb, a minimum of 2.4% gradient has to be maintained, won’t this invalidate the 3.3% minimum climb gradient? Thanks for your time. |
Yes it will. Therefore the airline will have an engine out escape route for each runway at each airport it operates to. |
Only if the 3.3% gradient is for terrain clearance.
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SID and contingency procedures are two separate things and do not mix them.
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Correct but the point is, in case of N-1 you may not be covered for terrain if flying the SID. CP |
a minimum of 2.4% gradient has to be maintained
We need to keep in mind that this is the second segment gross WAT limit for twins and that, in general, the aircraft probably won't be WAT limited .. so will do somewhat better. WAT requirements vary with number of engines, and segment .. which, I sometimes think, is overlooked in some of these discussions. Any takeoff must be predicated on the more restrictive of AEO and OEI situations .. ie if one quits, it shouldn't be an earth-shattering surprise to the crew. |
Thanks. But how do I understand this? 2.4% is a must. Does it mean I can disregard 3.3%? What if the SID has no EO procedure? Can I say that in the event of one engine after takeoff, most likely I will disregard the SID and maintain runway track, thus I can disregard the 3.3%? |
2.4% is the gross gradient requirement for a twin engine with one engine out in the second segment. It's 2.7% for a three-engined aircraft and 3% for a four-engined aircraft. The second segment lasts from the end of gear retraction to the higher of 400 ft AAL or acceleration height. The 3.3% is the nominal gradient for SIDs. If it is higher than that due to airspace requirements or obstacle clearance, the required gradient will be on the map.
2.4% is a certification requirement, 3.3 is the gradient used for procedure design. |
Originally Posted by Banana Joe
(Post 10154834)
2.4% is the gross gradient requirement for a twin engine with one engine out in the second segment. It's 2.7% for a three-engined aircraft and 3% for a four-engined aircraft. The second segment lasts from the end of gear retraction until up 400 ft AAL. The 3.3% is the nominal gradient for SIDs. If it is higher than that due to airspace requirements or obstacle clearance, the required gradient will be on the map.
2.4% is a certification requirement, 3.3 is the gradient used for procedure design. |
Originally Posted by extricate
(Post 10154835)
Yes, so I look at it differently?
And yes. Also Missed Approach procedures are designed with a nominal gradient of 2.5% (it can be lower in some cases), but if the required gradient is higher than 2.5% it will be written in bold on your approach plate. I started a thread about this a week or so ago asking for clarification and if you scroll down you might find it. |
Try not to talk about SIDs and OEI escape paths in the one sentence .. two different considerations. Generally, if one quits, the SID will not be achievable and you follow whatever is your OEI procedure for the runway. SID is for day to day AEO, OEI escape is for the off day when one quits.
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Originally Posted by extricate
(Post 10154725)
Thanks. But how do I understand this? 2.4% is a must. Does it mean I can disregard 3.3%? What if the SID has no EO procedure? Can I say that in the event of one engine after takeoff, most likely I will disregard the SID and maintain runway track, thus I can disregard the 3.3%? An EO procedure is not something a SID has, it is something your company has worked out, or paid someone to work out, for your departure runway. |
Originally Posted by AerocatS2A
(Post 10155223)
When all engines are operating you follow the SID and must comply with the SID climb gradient. If you lose an engine then the SID no longer applies, you follow the engine out procedure and don't have to comply with the SID climb requirements because you aren't following the SID anymore.
An EO procedure is not something a SID has, it is something your company has worked out, or paid someone to work out, for your departure runway. |
Hi guys...anyone can tell me where to find this whole thing of GRADIENT in order to finally understand it......Thanks a lot...
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Getting to Grips with Aircraft Performance
ICAO Doc 8168 [PANS-OPS], VOL II ICAO Annex 6, VOL I. |
Originally Posted by abakxm
(Post 10234851)
Hi guys...anyone can tell me where to find this whole thing of GRADIENT in order to finally understand it......Thanks a lot...
|
Originally Posted by AerocatS2A
(Post 10155223)
When all engines are operating you follow the SID and must comply with the SID climb gradient. If you lose an engine then the SID no longer applies, you follow the engine out procedure and don't have to comply with the SID climb requirements because you aren't following the SID anymore.
An EO procedure is not something a SID has, it is something your company has worked out, or paid someone to work out, for your departure runway. |
I can see how that can be a problem with truly difficult terrain (places like Queenstown, NZ, and I'm sure there are worse) but normally if you are on the SID and off the EO procedure you would be able to turn back toward the runway and then follow the EO procedure or just fly a safety heading from there.
We have one where the SID takes us towards rising terrain and I just brief if we've commenced the SID turn and suffer a failure, we will continue turning back over the airfield and fly the EO heading from there. We have another one where the EO procedure caters for failures at various points along the SID. |
Originally Posted by AerocatS2A
(Post 10235793)
I can see how that can be a problem with truly difficult terrain (places like Queenstown, NZ, and I'm sure there are worse) but normally if you are on the SID and off the EO procedure you would be able to turn back toward the runway and then follow the EO procedure or just fly a safety heading from there.
We have one where the SID takes us towards rising terrain and I just brief if we've commenced the SID turn and suffer a failure, we will continue turning back over the airfield and fly the EO heading from there. We have another one where the EO procedure caters for failures at various points along the SID. |
The fun starts when you have an engine failure after your SID deviation point.
Simple matter if the backroom guys are doing their job properly. Suggest you ask your flight standards folk (or ops engineers if they are in house) if the engine failure case has been examined for the entire SID track. Our procedure always was to make sure that a failure, anywhere along the departure track, was accommodated by the OEI procedure. If your folk don't do so, perhaps you should ask them to come along for a ride on the relevant departures on a regular basis ? |
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