Standard Departure Procedures Design Gradient (PDG) vs Final Segment Take-Off Climb

[TOGAtogate]

The Standard Procedure Design Gradient (PDG) is 3.3%. The PDG begins at a point 5m (16 feet) above the Departure End of the Runway (DER) and provides an additional clearance of 0.8% of the distance flown from the DER above an Obstacle Identification Surface (OIS). The OIS has a gradient of 2.5%. Where an obstacle penetrates the OIS, a steeper PDG may be promulgated to provide obstacle clearance of 0.8% of the distance flown from the DER.

An aircraft must be able to maintain a specified minimum gradient of climb in still air until end of Final Segment. Final Segment Take-Off Climb requirement is 1.2% for 2 engine aircraft with minus 0.8% for net flight path with 35 feet clearance. Which means 0.4% net flight path.
And for 4 engine aircraft 1.7% and minus 1% for net flight path.

Can anyone of you wiseguys explain the relationship between the two above requirements?

[Smythe]

of course us 'wiseguys' can easily explain this relationship.

[FlyingStone]

SID is meant to be used for AEO (all engines operating). You are never going to be limited by net takeoff flight path gradients with all engines working normally.

In case of OEI (one engine inoperative), the operator is required to provide crew with a procedure, which ensures net takeoff flight path can be achieved.

TLDR: You can't fly SID if your engine fails.

[Airmann]

TLDR: You can't fly SID if your engine fails.

My operator specifies that past the divergence point between the Engine out SID and the normal SID we are to continue on the normal SID. So this isnt technically true. In some cases the divergence point is as low as 500'

[john_tullamarine]

past the divergence point between the Engine out SID and the normal SID

One trusts that that philosophy is based on good science and that the remainder of the SID is achieveable OEI ? Otherwise, the statement might be VERY true.

[oggers]

DP gradients under both TERPs and PANSOPS are not designed to take account of engine failure. But you are still required to ensure that you can avoid all obstacles OEI hence you must have a contingency based on an obstacle analysis and your engine out performance. If you can see the obstacle you can avoid it hence part of the contingency might be cloud and visibility departure minima.

You must be able to do this with a net gradient ie a 0.8% margin to what the aircraft can actually give. That is where your second paragraph comes in. An obstacle clearance chart in the AFM already has the net performance buffer factored in.

[FlyingStone]

My operator specifies that past the divergence point between the Engine out SID and the normal SID we are to continue on the normal SID. So this isnt technically true. In some cases the divergence point is as low as 500'

While there might be a case, where you could fly the SID in OEI (operating an over-powered aircraft in flatland), it's not the case for the large majority of operations.

[aterpster]

past the divergence point between the Engine out SID and the normal SID

One trusts that that philosophy is based on good science and that the remainder of the SID is achieveable OEI ? Otherwise, the statement might be VERY true.
John, your trust is misplaced, at least as to FAA SIDs. The operator is always on the hook to satisfy OEI requirements when an engine fails after takeoff, but still on the SID. Having said that, where obstacles are critical, 121 operators can develop their own OEI-compatible SIDs, subject to approval by the FAA.

[john_tullamarine]

If you can see the obstacle you can avoid it hence part of the contingency might be cloud and visibility departure minima.

Generally, for the very shallow gradients involved, the human eye-brain cognition is just not up to estimating the difference between actual and required ... one really needs to do the sums beforehand.

The operator is always on the hook to satisfy OEI requirements when an engine fails after takeoff, but still on the SID.

That was the point I was trying to make, good sir.

[Smythe]

TLDR: You can't fly SID if your engine fails.


Basically correct! The operator MUST provide its own custom OEI DEP flightpath for EACH DEP or must validate that the AC can use the SID, again per each and every DEP. Luckily, the people doing the load plans figure this out, and limit the loading of the ac using the SID flightpath parameters..or they should be. That is why it is load/temp limited.

My operator specifies that past the divergence point between the Engine out SID and the normal SID we are to continue on the normal SID. So this isnt technically true. In some cases the divergence point is as low as 500'

Blindly following the SID while OEI is lemming talk.

[Centaurus]

But you are still required to ensure that you can avoid all obstacles OEI hence you must have a contingency based on an obstacle analysis and your engine out performance]

Regardless of what operator you work for, you would be wise to talk to the performance engineers who designed the runway analysis chart. In particular find out to what distance from lift off is the chart valid. I once worked for a European charter operator flying 737 Classics.
The runway analysis stated an immediate left turn required after take off due to close in terrain. It was a small Greek island. Acceleration height was 800 ft and the given track was over the sea. To my surprise there was another island dead on track about 12 miles from the departure airport with significant terrain and which we would have hit if IMC while accelerating.
On return to base I told the performance engineers about the presence of this island on the escape path. The reply was that the surveyed path stopped five miles on the escape path because of the terrain ahead. And it was up to the pilot to arrange his own safe flight path after that.

This information was not in the company route manual. I found this situation to be most disturbing as I am sure pilots of that airline had no idea that beyond five miles on the company published escape path the pilot was on his own. In VFR conditions that might be OK but not in IMC or night.
Many operators outsource their takeoff performance information to a third party provider. That being so, it is vital from the flight safety point of view to be aware how far the surveyed chart is valid for. You could be left in the lurch if you assume all runway analysis give you safe terrain clearance until MSA in IMC

[aterpster]

But you are still required to ensure that you can avoid all obstacles OEI hence you must have a contingency based on an obstacle analysis and your engine out performance]

Regardless of what operator you work for, you would be wise to talk to the performance engineers who designed the runway analysis chart. In particular find out to what distance from lift off is the chart valid. I once worked for a European charter operator flying 737 Classics.
The runway analysis stated an immediate left turn required after take off due to close in terrain. It was a small Greek island. Acceleration height was 800 ft and the given track was over the sea. To my surprise there was another island dead on track about 12 miles from the departure airport with significant terrain and which we would have hit if IMC while accelerating.
On return to base I told the performance engineers about the presence of this island on the escape path. The reply was that the surveyed path stopped five miles on the escape path because of the terrain ahead. And it was up to the pilot to arrange his own safe flight path after that.

This information was not in the company route manual. I found this situation to be most disturbing as I am sure pilots of that airline had no idea that beyond five miles on the company published escape path the pilot was on his own. In VFR conditions that might be OK but not in IMC or night.
Many operators outsource their takeoff performance information to a third party provider. That being so, it is vital from the flight safety point of view to be aware how far the surveyed chart is valid for. You could be left in the lurch if you assume all runway analysis give you safe terrain clearance until MSA in IMC

That is awful. A performance department applying FAR 121.189 and 121.191 can't pull that cr*p.

[oggers]

If you can see the obstacle you can avoid it hence part of the contingency might be cloud and visibility departure minima.

Generally, for the very shallow gradients involved, the human eye-brain cognition is just not up to estimating the difference between actual and required ... one really needs to do the sums beforehand.

I am talking about lateral clearance and visual course guidance. If the OEI procedure has visual course guidance you will have some predetermined wx minima to go with it.

[oggers]

Many operators outsource their takeoff performance information to a third party provider. That being so, it is vital from the flight safety point of view to be aware how far the surveyed chart is valid for. You could be left in the lurch if you assume all runway analysis give you safe terrain clearance until MSA in IMC

Well, that is certainly true. It must go to the point where you can either clear en route obstacles or return/divert. Knowing which is essential knowledge for sure.

[TOGA Tap]

Is it possible to have point on which SID and OEI diverge set at much higher altitude say 6000 ft above departure end runway due to very high obstacles very close to airport ?
Then SID and OEI contingency procedure would have the same track until 6000 ft. I understand that SIDs are general procedures good for all and OEI ones are tailored to specific aircraft type and operator. Are there any conflicting regulations which make this situation not legal or not practicable?

My question is not just academic and it relates a specific airport.

[TOGAtogate]

Thank you, guys, for really helpful answers.

From our OM-A, I would like to add regarding Vertical Obstacle Clearance:
"In addition to considering flight path after engine failure at Vef, as described above, engine failure at any point along the all engine flight path must also be considered. In mountainous terrain, this may call for multiple Engine Failure procedures valid for different sections of the all-engine climb-out procedure."

[Adrian De Villiers]

Hi,


Can you please give me an appropriate take off gradient for 125-180 seat single-aisle 2-eng jet Boeing to reach 12 000 to 13 000 feet after take off as quickly as possible.

Will help me a great deal, I'm in South Africa, and need to ask my local CAA to enforce an appropriate take off gradient, so the boeings get to 13 000 as quickly as possible after take off, to ensure noise pollution for us residents is minimised as quickly as possible after their west take off, as they turn right over PE residential areas after the west facing take off, in Newton Park Port Elizabeth, Soutth Afrian

[FlightDetent]

6,2 per cent.

[Adrian De Villiers]

how many feet per minute after take off at 6.2% ?

[FlightDetent]

All they can get. The A/C being above the desired profile would only benefit your cause, right?

Oh ... wait. I forgot to ask, would you prefer to have the aircraft flying at
- full thrust or reduced thurst (down to 40% power);
- lower or higher ?

The first one of each pair is obviously more noisy than the other. Can you see the dilemma emerging? Another large issue to solve is the speed, which defines the exposure over the trajectory footprint.

Why not expand a bit what made you come here, and share some ideas about your citizen complaint claim strategy?