SID Climb Gradient : "Minimum or Average"
Originally Posted by GF
I'm trying to understand your post-facetious or insulting?
Last edited by Capn Bloggs; 10th Feb 2017 at 06:54. Reason: spelin`
Yeah, in many cases, but, like all planes, being at the limit was always a challenge. A Global at the limit isn't much better than any other FAR 25 plane. I just looked about 5% to 4,000' at 20, S.L airport, the limit weight for obstacle is about 83,000#. MTOW is 99,500.
Thanks for the clarification.
Thanks for the clarification.
Last edited by galaxy flyer; 10th Feb 2017 at 00:04.
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president:
True, but irrelevant to performance and engineering. The starting point for computation of the takeoff flight path is an engine failure just above decision speed.
Also, good planning requires a contingency if the engine fails airborne and early into a SID. How do you switch to the preplanned OEI track? Sometimes, that path quickly disappears in mountainous areas. Thus, the reason the U.S. carriers got the FAA to permit the carriers to use a pre-approved carrier-developed departure path instead of using the canned SID. This option is generally limited to airports with challenging terrain.
That depends where the engine fails. If you have an engine failure airborne on a normal SID with a 3.3 % requirement you might have the safe choice to stay on the SID and still comply with the required gradient.
Also, good planning requires a contingency if the engine fails airborne and early into a SID. How do you switch to the preplanned OEI track? Sometimes, that path quickly disappears in mountainous areas. Thus, the reason the U.S. carriers got the FAA to permit the carriers to use a pre-approved carrier-developed departure path instead of using the canned SID. This option is generally limited to airports with challenging terrain.
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with a 3.3 % requirement you might have the safe choice
A big ask. Unless the sums have been done beforehand, or the weights are very light, the gradient capability mismatch OEI/AEO might put the aircraft in harm's way.
All this should emphasise the need for adequate OEI escape planning ... this stuff usually is quite incompatible with winging it on the fly.
A big ask. Unless the sums have been done beforehand, or the weights are very light, the gradient capability mismatch OEI/AEO might put the aircraft in harm's way.
All this should emphasise the need for adequate OEI escape planning ... this stuff usually is quite incompatible with winging it on the fly.
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president:
True, but irrelevant to performance and engineering. The starting point for computation of the takeoff flight path is an engine failure just above decision speed.
Also, good planning requires a contingency if the engine fails airborne and early into a SID. How do you switch to the preplanned OEI track? Sometimes, that path quickly disappears in mountainous areas. Thus, the reason the U.S. carriers got the FAA to permit the carriers to use a pre-approved carrier-developed departure path instead of using the canned SID. This option is generally limited to airports with challenging terrain.
True, but irrelevant to performance and engineering. The starting point for computation of the takeoff flight path is an engine failure just above decision speed.
Also, good planning requires a contingency if the engine fails airborne and early into a SID. How do you switch to the preplanned OEI track? Sometimes, that path quickly disappears in mountainous areas. Thus, the reason the U.S. carriers got the FAA to permit the carriers to use a pre-approved carrier-developed departure path instead of using the canned SID. This option is generally limited to airports with challenging terrain.
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I agree. It's an option and that was my only point. I started the sentence by saying you should be on an EFP, so I don't see what the fuzz is about. It's also an option to manoeuvre visually around the objects in VMC. Or fly straight out over the sea and deviate from both the EFP and SID. Or stay at home. I didn't comment on what is clever or easy to do. There are many valid options, and it's our job to choose the best.
In some cases with a late engine failure you would be a fool not to continue the SID. Before you all start... in SOME cases.
In some cases with a late engine failure you would be a fool not to continue the SID. Before you all start... in SOME cases.
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I wrote MIGHT.
Noted. My comment was not intended to criticise you at all, rather, I am always cognisant of posts being read by newchums, hence the clarification.
make decision based upon the sum of your experience
.. but why waste effort and all that experience when it would be far simpler, and a whole sight more valid and useful, to do (or have your operator do) the escape sums before hand ?
What I did say was that with OEI you should be on an approved EFP
Generally, that covers the V1 case. The big problem is no V1 failure, continue SID, noise stops well into the SID but well prior to a safe area height ...
In some cases, the operator will require all departures to be via the escape where the SID is too limiting. In all (ie most occasions) of the remaining cases, the ops engineers SHOULD have done the sums to get you out of trouble with a failure ANYWHERE along the SID flightpath. Unfortunately, this is not the case so often and the Commander is left holding the baby ..
and I'm obviously without doubt above the min gradient well maybe yes just hold at the end of it or pick up vectors
Maybe yes, maybe no ... and maybe the paragraph above is a better way to go ?
It's also an option to manoeuvre visually around the objects in VMC
If you have a couple of big rocky bits well to one side or the other, fine .. if you plan to eyeball it over the obstacles ... good luck and rather you than me. Generally, just not feasible due to the shallow climb gradients OEI.
Or fly straight out over the sea
Not much good if you are in tiger country and need to get past some nasty terrain before you see blue underneath ..
There are many valid options
I am a bit of a conservative .. but, I suggest, there is only one valid OEI option (unless you any departing in a flat desert area with nil rocky bits as far as the eye can see) and that is to do the OEI escape sums before departure. Generally, this is not feasible for the line pilot so it falls (rightly) on operator management.
Noted. My comment was not intended to criticise you at all, rather, I am always cognisant of posts being read by newchums, hence the clarification.
make decision based upon the sum of your experience
.. but why waste effort and all that experience when it would be far simpler, and a whole sight more valid and useful, to do (or have your operator do) the escape sums before hand ?
What I did say was that with OEI you should be on an approved EFP
Generally, that covers the V1 case. The big problem is no V1 failure, continue SID, noise stops well into the SID but well prior to a safe area height ...
In some cases, the operator will require all departures to be via the escape where the SID is too limiting. In all (ie most occasions) of the remaining cases, the ops engineers SHOULD have done the sums to get you out of trouble with a failure ANYWHERE along the SID flightpath. Unfortunately, this is not the case so often and the Commander is left holding the baby ..
and I'm obviously without doubt above the min gradient well maybe yes just hold at the end of it or pick up vectors
Maybe yes, maybe no ... and maybe the paragraph above is a better way to go ?
It's also an option to manoeuvre visually around the objects in VMC
If you have a couple of big rocky bits well to one side or the other, fine .. if you plan to eyeball it over the obstacles ... good luck and rather you than me. Generally, just not feasible due to the shallow climb gradients OEI.
Or fly straight out over the sea
Not much good if you are in tiger country and need to get past some nasty terrain before you see blue underneath ..
There are many valid options
I am a bit of a conservative .. but, I suggest, there is only one valid OEI option (unless you any departing in a flat desert area with nil rocky bits as far as the eye can see) and that is to do the OEI escape sums before departure. Generally, this is not feasible for the line pilot so it falls (rightly) on operator management.
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TangoAlphaD:
At some terrain-laden airports vectors won't do you much good if you're below the controller's minimum vectoring altitude. The industry was recently reminded about that last December with EVA coming very close to a CFIT on Mt. Wilson northeast of KLAX. And, KLAX isn't what I would call terrain-laden.
If the SID ends at 6000' and I'm at 5000 when the donkey dies and early on in the SID and I'm obviously without doubt above the min gradient well maybe yes just hold at the end of it or pick up vectors.
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There will always be the guys saying "yes but NOT if there is a giraf on the runway". True dat! We all agree that there are plenty of options, but not every single time. On a V1 cut in low vis there is one option. And everyone knows that. The discussion was interesting until it started with some OEI stuff nobody asked about.
Back to the original question, what isn't clearly specified is whether the gradient is required by ATC or national authority for some reason (noise, president's palace) OR is it an obstacle. Charting doesn't always make thus clear. Going back to prior life, US DOD charts would specify "minimum" for obstacle or "ATC required" for all else. Two very different problems. Average will work if it is purely an airspace issue and as long as you get to 4,000' by the required point. If it is an terrain generated minimum really means MINIMUM. That maybe how we got down into OEI problems here.
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They don't at LAX either. The controller turned them in the wrong direction towards high terrain then leveled them off at 5,000 into an area of 7,700 MVA. We had a big thread about it last December.
That near-disaster illustrates that requesting vectors when dropping below the floor of a SID with OEI may not be a wise course of action if well below MVA. The area below MVA, especially in the vicinity of rising terrain, is mostly a void for the controller. In the U.S. they do have emergency obstruction video maps (EOVMs) but they have neither the fidelity nor obstacle clearance to do much good.
That near-disaster illustrates that requesting vectors when dropping below the floor of a SID with OEI may not be a wise course of action if well below MVA. The area below MVA, especially in the vicinity of rising terrain, is mostly a void for the controller. In the U.S. they do have emergency obstruction video maps (EOVMs) but they have neither the fidelity nor obstacle clearance to do much good.
