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View Full Version : 3.3% PDG and 2.4% One Eng Climb Gradient


extricate
23rd May 2018, 09:55
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, wont this invalidate the 3.3% minimum climb gradient?

Thanks for your time.

AerocatS2A
23rd May 2018, 10:12
Yes it will. Therefore the airline will have an engine out escape route for each runway at each airport it operates to.

His dudeness
23rd May 2018, 10:19
Only if the 3.3% gradient is for terrain clearance.

TOGA Tap
23rd May 2018, 10:52
SID and contingency procedures are two separate things and do not mix them.

CaptainProp
23rd May 2018, 11:22
Correct but the point is, in case of N-1 you may not be covered for terrain if flying the SID.

CP

john_tullamarine
23rd May 2018, 12:34
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.

extricate
23rd May 2018, 13:33
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%?

Banana Joe
23rd May 2018, 16:14
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.

extricate
23rd May 2018, 16:16
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.

Yes, so I look at it differently?

Banana Joe
23rd May 2018, 16:19
Yes, so I look at it differently?

Give another look at my message, I edited it because of course the second segment ends at acceleration altitude/height if it's higher than 400 ft. 400 ft is the absolute minimum.

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.

john_tullamarine
24th May 2018, 00:15
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.

AerocatS2A
24th May 2018, 01:40
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%?
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.

extricate
24th May 2018, 06:04
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.

Thanks for this, agreed

abakxm
28th Aug 2018, 00:20
Hi guys...anyone can tell me where to find this whole thing of GRADIENT in order to finally understand it......Thanks a lot...

FlightDetent
28th Aug 2018, 12:28
Getting to Grips with Aircraft Performance
ICAO Doc 8168 [PANS-OPS], VOL II
ICAO Annex 6, VOL I.

aterpster
28th Aug 2018, 14:46
Hi guys...anyone can tell me where to find this whole thing of GRADIENT in order to finally understand it......Thanks a lot...
Trust the performance engineers. The calculation for each OEI route is their job. It's your job to correctly fly it in the event of an engine failure after V1.

hans brinker
28th Aug 2018, 16:06
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.

The fun starts when you have an engine failure after your SID deviation point. I worked for a while in a place where in mountainous terrain the EO procedure would often be different from the SID starting from the departure end of the runway. If the engine failure happened after V1 you followed the EO procedure. The company maintained that was legal because if you have an engine failure at the most critical point, which is and will always be V1, you have a way out. . My point was, if I have an engine failure after the point where the EO procedure and SID deviate, I will be stuck on the SID, without the required climb performance. To me this made the SID deviation point the most critical point, and not V1. Luckily we operated in non radar, and the controllers were very flexible, so I would always fly the EO procedure until above MSA/MORA, and then pick up the SID again. It took a while for the company to adjust the numbers to guarantee obstacle clearance if the engine failure happened after the SID deviation point.

AerocatS2A
28th Aug 2018, 23:22
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.

hans brinker
29th Aug 2018, 00:31
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.

One of our best was LESO/San Sebastian in Spain. Taking of from rwy22 with engine failure was a right turn towards the bay, no failure left towards the mountains. There is no way you could have turned back safely towards the airport after starting the left turn.

john_tullamarine
29th Aug 2018, 01:06
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 ?

aterpster
29th Aug 2018, 01:53
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 ?

As always, well stated!!

hans brinker
29th Aug 2018, 05:30
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 ?

Absolutely true. This was 2002, when I joined in 1999 there were no TOLD tables at all. It took them a bit of time before they listened to the pilots out there and improved the procedures. Small company, flying contracts away from home, little oversight. Still the best job Ive had!!

Tommy Gavin
29th Aug 2018, 09:54
When the SID provides a climb gradient check your Perf Data in the QRH for Eng OUt. Can make it? You can stay on the SID. Can't make it? Follow the EOSID and inform ATC...

Escape Path
30th Aug 2018, 03:51
We used to have a legend in our AIP charts that said what gradient was for terrain reasons and what gradient for ATS purposes. One read (maybe erroneously) "PDG" and the other one read (dead on) ATS. Nice piece of info. Today's format only says something like "X.X% for obstacles until xxxxft then X.X%". Haven't seen this in the Jepp format charts though.https://cimg0.ibsrv.net/gimg/www.gmforum.com-vbulletin/554x923/scrshot363_8ab36d21a4eed45f648c0a517dcbeb0f49bd9063.jpg
Yellow box reads: "Max 185 KIAS until turn is complete. Minimum PDG due to obstacles 5.7% until 10000, then 3.3%"

EDIT: Ah, turns out they still publish that, but apparently only for Bogota. Bottom part of the chart contains the goodies. There's still a note there, similar to the chart above, that reads "Maintain 8.2% until 9200ft then 6.7 until KORKI". Being 6.7% the gradient for obstacles, looks like it's basically the same as the previous chart, only this one will require a gradient above standard for obstacle clearance and they're telling you these "categorised" PDG's (they're both PDGs, aren't they?)

https://cimg0.ibsrv.net/gimg/www.gmforum.com-vbulletin/588x910/scrshot364_6f204aa5a53886594c380a0413f48379ef937ce8.jpg

aterpster
30th Aug 2018, 14:29
EDIT: Ah, turns out they still publish that, but apparently only for Bogota. Bottom part of the chart contains the goodies. There's still a note there, similar to the chart above, that reads "Maintain 8.2% until 9200ft then 6.7 until KORKI". Being 6.7% the gradient for obstacles, looks like it's basically the same as the previous chart, only this one will require a gradient above standard for obstacle clearance and they're telling you these "categorised" PDG's (they're both PDGs, aren't they?)

Here is the Jepp chart. It doesn't state whether the gradients are for ATC or obstacles. No doubt that obstacles would be a component at Bogota, but the gradient may be steeper than required for obstacles in order to satisfy ATC requirements. With all engines operating, the stated gradients must be complied with. OEI is a different matter. Bogota requires an OEI track that deviates sufficiently from this track that a U.S. operator I am familiar with requires a declaration of emergency.https://cimg6.ibsrv.net/gimg/www.gmforum.com-vbulletin/1500x1171/skbo_dccc3504f74c6267df25f2ac1c18c916adc555f8.jpg

8che
30th Aug 2018, 21:07
PANS OPS clearly states that all its calculations (including PDG) are based on all engines working correctly.
It is solely up to individual operators to develop contingency procedures if engines fail. If your company are not providing correct guidance on eng fail scenarios including on the SID then they are failing to comply with their responsibility. There is no relationship between 2.4 and 3.3%. They are entirely different regulatory requirements.

Escape Path
31st Aug 2018, 02:09
OEI is a different matter. Bogota requires an OEI track that deviates sufficiently from this track that a U.S. operator I am familiar with requires a declaration of emergency.

Almost immediately. This the EO procedure for my company. It basically requires you to keep turning right into the only flat part in the area.

https://cimg1.ibsrv.net/gimg/www.gmforum.com-vbulletin/1404x970/screenshot_20180830_195158_2_77ca4d83953c2197d17aec636b8f91f f7c2f1f26.png

Things are aggravated if you already turned left. Different trajectories to follow depending on your position at the time of failure.

https://cimg2.ibsrv.net/gimg/www.gmforum.com-vbulletin/1409x953/screenshot_20180830_195325_2_863e28b9922783370fbd20afe56d5b4 aed4faebd.png