Segment 3 performance - 20.7.1b
Thread Starter
Segment 3 performance - 20.7.1b
Did a search and could not find the answer; hoping someone can help.
This relates to the Australian CAOs, in particular 20.7.1.b, which deals with takeoff climb performance.
Firstly, my understanding is that in the third (level) segment, a climb performance capability of 1.2% gross is required and that this capability is available to accelerate the aircraft in that segment to final takeoff climb speed. (I'm paraphrasing 7.3.1 and 7.3.2)
However, I just noticed a sentence in the orders that I don't understand.
7.5 "...Similarly the horizontal distance to accelerate in compliance with paragraph 7.3.1 must be increased due to the acceleration reduction equivalent to the climb gradient reductions specified in this paragraph."
I'm not even sure I understand that sentence at all, but if I interpret it correctly:
1) Firstly, how can the horizontal distance to accelerate in the level segment be determined at all?
and
2) How could that distance (if able to be determined) be reduced by an allowance based on a climb gradient reduction from gross to net -a "reduction equivalent" -if in fact that is what it means...
Confused I am.
This relates to the Australian CAOs, in particular 20.7.1.b, which deals with takeoff climb performance.
Firstly, my understanding is that in the third (level) segment, a climb performance capability of 1.2% gross is required and that this capability is available to accelerate the aircraft in that segment to final takeoff climb speed. (I'm paraphrasing 7.3.1 and 7.3.2)
However, I just noticed a sentence in the orders that I don't understand.
7.5 "...Similarly the horizontal distance to accelerate in compliance with paragraph 7.3.1 must be increased due to the acceleration reduction equivalent to the climb gradient reductions specified in this paragraph."
I'm not even sure I understand that sentence at all, but if I interpret it correctly:
1) Firstly, how can the horizontal distance to accelerate in the level segment be determined at all?
and
2) How could that distance (if able to be determined) be reduced by an allowance based on a climb gradient reduction from gross to net -a "reduction equivalent" -if in fact that is what it means...
Confused I am.
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Yeah - a great example of clear writing 
My understanding (and I am not a pilot, but I have had to calculate net flight paths in my time) would be that you are allowed to make a level flight acceleration at 400 ft or at an obstacle clearance height to get to a speed that allows you to meet the en-route climb gradient requirements.
7.3.2 is not at all clear, but I would read it as requiring that if you went from a level acceleration to a climb at any point you must have at least 1.2% gross gradient available. Since both acceleration and climb gradient are proportional to (T-D)/W this is equivalent to requiring a minimum acceleration capability of 0.012g.
7.5 is a bit easier - when constructing the clearance profile you have to degrade the gross gradients by the gross/net flight path margin. When looking at the bit of the profile that relates to the acceleration segment you must equally add a margin, in this case by adding distance. The bit about "equivalent to the climb gradient reductions" is just saying that the margin to be applied in distance is the same as that which must be applied in the climb segments; that is a reduction of 0.8% in acceleration capability. I think that means you should have an acceleration of at least 0.4% available - and that is a magnificent 0.07 kts per second!!
Hope this helps rather than confuses
My understanding (and I am not a pilot, but I have had to calculate net flight paths in my time) would be that you are allowed to make a level flight acceleration at 400 ft or at an obstacle clearance height to get to a speed that allows you to meet the en-route climb gradient requirements.
7.3.2 is not at all clear, but I would read it as requiring that if you went from a level acceleration to a climb at any point you must have at least 1.2% gross gradient available. Since both acceleration and climb gradient are proportional to (T-D)/W this is equivalent to requiring a minimum acceleration capability of 0.012g.
7.5 is a bit easier - when constructing the clearance profile you have to degrade the gross gradients by the gross/net flight path margin. When looking at the bit of the profile that relates to the acceleration segment you must equally add a margin, in this case by adding distance. The bit about "equivalent to the climb gradient reductions" is just saying that the margin to be applied in distance is the same as that which must be applied in the climb segments; that is a reduction of 0.8% in acceleration capability. I think that means you should have an acceleration of at least 0.4% available - and that is a magnificent 0.07 kts per second!!
Hope this helps rather than confuses
Moderator
If I may amplify the previous post a bit.
DCA-speak to reflect what the AFM analyses do (ah, fond memories of previous lives) -
(a) gross to net infers a fudge factor reduction in performances for mum and the kids
(b) for climb this is easy - x% gross (nominal actual real world gradient) degrades by y% (per certification Standard) to give you z% (net for the calculations)
(c) does it not make sense, then, to do something similar for the third segment - climb gradient reflects excess thrust from which we can play with a gradient penalty reduction - this can be converted to a similar penalty in the acceleration capability for level flight (rather than climb gradient).
(d) as a result, the gross third segment to accelerate from V2 to the final climb speed, while reconfiguring from takeoff to final climb (x metres) will degrade to a longer distance (y metres) reflecting the lesser acceleration and longer time taken to get from V2 to final climb speed.
how can the horizontal distance to accelerate in the level segment be determined at all?
.. basic (mathematical) mechanics.
Acceleration as a function of time is integrated to give speed (strictly, velocity) as a function of time which, in turn, is integrated to give distance (gone) as a function of time and this ends up in the AFM charts - backroom stuff done by the aerodynamicists using performance models for the Type verified (and tweaked) using real world flight test data.
How could that distance (if able to be determined) be reduced by an allowance based on a climb gradient reduction from gross to net -a "reduction equivalent"
The gross to net reduction in climb gradient can be recalculated as a gross to net equivalent acceleration capability. Plug the revised acceleration capability into the integrating exercise et, voilą, you end up with a degraded (ie longer) distance reflecting the reduced acceleration capability.
if in fact that is what it means
exactly what it means ...
Main thing to recall - in years gone by, the DCA engineers (IT, RF, et al) had to put the local certification stuff in the ANOs (now CAOs). These were the 101 series and, for heavies, we were looking at 101.5 (UK Types) or 101.6 (US Types). The flying operations folk (who were good pilots but not so good at engineering) then recast the certification stuff into operational requirements (20 series) and got lots wrong in the translation.
Main thing - don't sweat it too much - the AFM does it all for you - you just have to apply the AFM requirements.
Confused I am.
That's why we have PPRuNe to sort out the confusion - what could be simpler ?
When looking at the bit of the profile that relates to the acceleration segment you must equally add a margin, in this case by adding distance
Yes and no.
Yes for the certification - it's built into the AFM.
No for the pilot - else you would be double dipping and the accountants would be after your neck. In any case the calculations are not intended for pilots to worry about.
DCA-speak to reflect what the AFM analyses do (ah, fond memories of previous lives) -
(a) gross to net infers a fudge factor reduction in performances for mum and the kids
(b) for climb this is easy - x% gross (nominal actual real world gradient) degrades by y% (per certification Standard) to give you z% (net for the calculations)
(c) does it not make sense, then, to do something similar for the third segment - climb gradient reflects excess thrust from which we can play with a gradient penalty reduction - this can be converted to a similar penalty in the acceleration capability for level flight (rather than climb gradient).
(d) as a result, the gross third segment to accelerate from V2 to the final climb speed, while reconfiguring from takeoff to final climb (x metres) will degrade to a longer distance (y metres) reflecting the lesser acceleration and longer time taken to get from V2 to final climb speed.
how can the horizontal distance to accelerate in the level segment be determined at all?
.. basic (mathematical) mechanics.
Acceleration as a function of time is integrated to give speed (strictly, velocity) as a function of time which, in turn, is integrated to give distance (gone) as a function of time and this ends up in the AFM charts - backroom stuff done by the aerodynamicists using performance models for the Type verified (and tweaked) using real world flight test data.
How could that distance (if able to be determined) be reduced by an allowance based on a climb gradient reduction from gross to net -a "reduction equivalent"
The gross to net reduction in climb gradient can be recalculated as a gross to net equivalent acceleration capability. Plug the revised acceleration capability into the integrating exercise et, voilą, you end up with a degraded (ie longer) distance reflecting the reduced acceleration capability.
if in fact that is what it means
exactly what it means ...
Main thing to recall - in years gone by, the DCA engineers (IT, RF, et al) had to put the local certification stuff in the ANOs (now CAOs). These were the 101 series and, for heavies, we were looking at 101.5 (UK Types) or 101.6 (US Types). The flying operations folk (who were good pilots but not so good at engineering) then recast the certification stuff into operational requirements (20 series) and got lots wrong in the translation.
Main thing - don't sweat it too much - the AFM does it all for you - you just have to apply the AFM requirements.
Confused I am.
That's why we have PPRuNe to sort out the confusion - what could be simpler ?
When looking at the bit of the profile that relates to the acceleration segment you must equally add a margin, in this case by adding distance
Yes and no.
Yes for the certification - it's built into the AFM.
No for the pilot - else you would be double dipping and the accountants would be after your neck. In any case the calculations are not intended for pilots to worry about.
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Yes and no.
Yes for the certification - it's built into the AFM.
No for the pilot - else you would be double dipping and the accountants would be after your neck. In any case the calculations are not intended for pilots to worry about.
Yes for the certification - it's built into the AFM.
No for the pilot - else you would be double dipping and the accountants would be after your neck. In any case the calculations are not intended for pilots to worry about.
Well I DID say I am not a pilot
Thread Starter
CliveL and JohnT - thanks both for your answers.
(JohnT - I was rather hoping you were lurking as I knew this one of your specialties!)
But could I pose a follow up question?
It is straightforward mathematics to determine the time and distance required to traverse both the 2nd and 4th segments, at a given weight - say at MTOW.
But for my own operations; (DHC8 300) with a typical 15km surveyed obstacle clear area, are my RTOW charts ensuring, based on the backroom aerodynamicists work that you mentioned, that I'll reach final takeoff speed/config (to commence the 4th segment) by the end of the 15km? Or by any particular point?
(JohnT - I was rather hoping you were lurking as I knew this one of your specialties!)
But could I pose a follow up question?
It is straightforward mathematics to determine the time and distance required to traverse both the 2nd and 4th segments, at a given weight - say at MTOW.
But for my own operations; (DHC8 300) with a typical 15km surveyed obstacle clear area, are my RTOW charts ensuring, based on the backroom aerodynamicists work that you mentioned, that I'll reach final takeoff speed/config (to commence the 4th segment) by the end of the 15km? Or by any particular point?
Moderator
with a typical 15km surveyed obstacle clear area
First, the AFM charts give the operations engineers (or the pilot) the data to do the sums and match performance capability (actually certification or net performance so you have a bit up your sleeve) to the runway environs. The AFM data is vetted fairly heavily by the Regulatory Authority (FAA etc) so it is likely that that data is reasonably OK.
When it comes to applying the AFM data to the real world, there are all sorts of folk out there doing the work - some well, some not quite so well, and some quite dreadfully. I guess you are with one of the QF entities (?) so, presumably, QF ops eng looks after your performance - in which case it probably is done with a reasonable degree of rigour.
are my RTOW charts ensuring .. that I'll reach final takeoff speed/config (to commence the 4th segment) by the end of the 15km?
I can't offer any comment on that question without having a bunch of data to do some check analyses myself. The question needs to be addressed to your company operations engineers. If they tell you that the net takeoff flight path analysis doesn't take care of you right up to LSA/MSA .. then I'd be having a talk with the union for starters ... albeit the pilot unions in Australia have been somewhat on the back foot for quite some time now ..
I can't recall doing any ops eng work with -300 so I can only speak generally. Fortunately for turboprops, the third segment is comparatively short so the problems further out (usually) are somewhat less than might apply to, say, the twin jets. As I recall, the DC9, for instance, with a significant speed delta between V2 and final climb speed took forever to get through the net third segment - not hard to see upwards of 50nm OEI to get to 1500ft. I never did incline to the airlines which figured that it was a pilot problem to worry about post 50,000 ft (or 15km, if you prefer) in the Type A chart ...
First, the AFM charts give the operations engineers (or the pilot) the data to do the sums and match performance capability (actually certification or net performance so you have a bit up your sleeve) to the runway environs. The AFM data is vetted fairly heavily by the Regulatory Authority (FAA etc) so it is likely that that data is reasonably OK.
When it comes to applying the AFM data to the real world, there are all sorts of folk out there doing the work - some well, some not quite so well, and some quite dreadfully. I guess you are with one of the QF entities (?) so, presumably, QF ops eng looks after your performance - in which case it probably is done with a reasonable degree of rigour.
are my RTOW charts ensuring .. that I'll reach final takeoff speed/config (to commence the 4th segment) by the end of the 15km?
I can't offer any comment on that question without having a bunch of data to do some check analyses myself. The question needs to be addressed to your company operations engineers. If they tell you that the net takeoff flight path analysis doesn't take care of you right up to LSA/MSA .. then I'd be having a talk with the union for starters ... albeit the pilot unions in Australia have been somewhat on the back foot for quite some time now ..
I can't recall doing any ops eng work with -300 so I can only speak generally. Fortunately for turboprops, the third segment is comparatively short so the problems further out (usually) are somewhat less than might apply to, say, the twin jets. As I recall, the DC9, for instance, with a significant speed delta between V2 and final climb speed took forever to get through the net third segment - not hard to see upwards of 50nm OEI to get to 1500ft. I never did incline to the airlines which figured that it was a pilot problem to worry about post 50,000 ft (or 15km, if you prefer) in the Type A chart ...
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J.T. and other performance gurus. I'd like you comments please on the following:
Does the author refer in the quote to the acceleration segment during missed approach, if so, what consequences does it have? I have my own ideas but would like to get your view on that.
Thanx.
PANS-OPS 4 further indicates that the acceleration segment criteria have been deleted, as formerly published in ICAO Document 8168, Volume II, First, Second and Third Editions.
NOTE: Acceleration Segment criteria published in previous editions of Document 8168 are contained in Appendix 1.
NOTE: Acceleration Segment criteria published in previous editions of Document 8168 are contained in Appendix 1.
Thanx.
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9.G, I would have thought that PANS OPS 4 and Part 25 certification are two completely different animals...
DraggingAir...... it really depends on how the AFM was constructed, the person that you really need to answer the question for the DHC8 is Mad (Flt) Scientist. Generally speaking, most of our (non Bombardier) AFM's go to a maximum distance of 12 nms, if you have obstacles further than that, you have to scale them back within the chart. You should be able to use the charts to determine the distance where you will complete the acceleration portion.
Mutt
DraggingAir...... it really depends on how the AFM was constructed, the person that you really need to answer the question for the DHC8 is Mad (Flt) Scientist. Generally speaking, most of our (non Bombardier) AFM's go to a maximum distance of 12 nms, if you have obstacles further than that, you have to scale them back within the chart. You should be able to use the charts to determine the distance where you will complete the acceleration portion.
Mutt
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....not hard to see upwards of 50nm OEI to get to 1500ft.
Folks would never believe it if they hadn't flown one, and noticed it personally.
Even with all four turning, 400 ft/min at V2+10 after an 11,500 foot ground run was not uncommon, for a takeoff at max weight...317,000 pounds.
Of course, this was a CAR4b type, so not much margin left for performance.
Moderator
You should be able to use the charts to determine the distance where you will complete the acceleration portion.
Doing the basic sums for a given weight, runway and ambients is the easy part - the AFM provides the necessary data.
Matching that analysis to the obstacles is another story.
Getting the obstacle data once you are much outside the published splays is plain old detective work and, often, done very poorly.
Doing the basic sums for a given weight, runway and ambients is the easy part - the AFM provides the necessary data.
Matching that analysis to the obstacles is another story.
Getting the obstacle data once you are much outside the published splays is plain old detective work and, often, done very poorly.
Thread Starter
To summarise..
It seems that determining how my company RTOW charts have been devised is one matter, as is the identification of any other obstacles beyond the surveyed area.
And that the 1.2% gross climb capability required in the 3rd segment (normally used to accelerate) is factored by the regs to equate to an increased distance allowed/required for acceleration to final climb speed.
And...this equates to an acceleration of .07 knots per second (CliveL above).
Given all that, I can extrapolate the certification performance required in terms of distance and time, in all 4 segments. For the sake of the exercise, for fellow geeks, and to confirm that I have got it right, here we go.
I am assuming a V2 of 122 knots and final takeoff climb speed of 132 knots, based on a DHC8-300 at MTOW (although I don't have the book figures with me at the moment).
Segment Two
Gradient - 1.6% net required
Speed - 122 knots
Rate of Climb - 195 fpm
Time to reach 400' - 2.05 minutes
Distance to reach 400' - 4.16nm
Segment Three
Gradient - 1.2% gross
Start speed - 122 knots
Finish speed - 132 knots
Avg speed - 127 knots
Acceleration - .07 knots/sec
Time to accelerate - 2.4 minutes
Distance covered - 5.04nm
So, to reach the start of the 4th segment, time required is a total of 4.43 minutes (within the 5 minutes available at max power/MTOP) and the distance covered is 9.21nm (at 17.06km this is 2km beyond the normal 15km surveyed area).
And to complete the numbers:
Segment Four
Gradient 0.4% net
Rate of Climb - 53 fpm
Time to climb another 1100' (to 1500' AGL) - 20.8 minutes
Distance covered in that time - 45.8nm
Grand Total to end of 4th segment
Time - 25.2 minutes
Distance - 55.04nm / 102 km
What I find interesting is that, to consider just one aerodrome that we visit, there is an MSA of 3,000' and we use an acceleration altitude of 1,700' (which is 400 and something feet AGL in this case).
Based on the numbers above there is no way we will reach 3,000' within the 25nm of the MSA.
Which raises another question: upon the loss of one engine at V1, at this airport, based on these numbers, if the pilot was continuing and not returning to the departure aerodrome (for whatever reasons), then he/she would presumably need to manoeuvre within the MSA until either the MSA or LSALT was reached. Which would entail very small bank angles to preserve any of that 53 fpm available.
And that seems to me a case for not departing that aeordrome unless I intended to return to it (in the case of a failure at V1), and not proceed.
Is that how I should look at it?
It seems that determining how my company RTOW charts have been devised is one matter, as is the identification of any other obstacles beyond the surveyed area.
And that the 1.2% gross climb capability required in the 3rd segment (normally used to accelerate) is factored by the regs to equate to an increased distance allowed/required for acceleration to final climb speed.
And...this equates to an acceleration of .07 knots per second (CliveL above).
Given all that, I can extrapolate the certification performance required in terms of distance and time, in all 4 segments. For the sake of the exercise, for fellow geeks, and to confirm that I have got it right, here we go.
I am assuming a V2 of 122 knots and final takeoff climb speed of 132 knots, based on a DHC8-300 at MTOW (although I don't have the book figures with me at the moment).
Segment Two
Gradient - 1.6% net required
Speed - 122 knots
Rate of Climb - 195 fpm
Time to reach 400' - 2.05 minutes
Distance to reach 400' - 4.16nm
Segment Three
Gradient - 1.2% gross
Start speed - 122 knots
Finish speed - 132 knots
Avg speed - 127 knots
Acceleration - .07 knots/sec
Time to accelerate - 2.4 minutes
Distance covered - 5.04nm
So, to reach the start of the 4th segment, time required is a total of 4.43 minutes (within the 5 minutes available at max power/MTOP) and the distance covered is 9.21nm (at 17.06km this is 2km beyond the normal 15km surveyed area).
And to complete the numbers:
Segment Four
Gradient 0.4% net
Rate of Climb - 53 fpm
Time to climb another 1100' (to 1500' AGL) - 20.8 minutes
Distance covered in that time - 45.8nm
Grand Total to end of 4th segment
Time - 25.2 minutes
Distance - 55.04nm / 102 km
What I find interesting is that, to consider just one aerodrome that we visit, there is an MSA of 3,000' and we use an acceleration altitude of 1,700' (which is 400 and something feet AGL in this case).
Based on the numbers above there is no way we will reach 3,000' within the 25nm of the MSA.
Which raises another question: upon the loss of one engine at V1, at this airport, based on these numbers, if the pilot was continuing and not returning to the departure aerodrome (for whatever reasons), then he/she would presumably need to manoeuvre within the MSA until either the MSA or LSALT was reached. Which would entail very small bank angles to preserve any of that 53 fpm available.
And that seems to me a case for not departing that aeordrome unless I intended to return to it (in the case of a failure at V1), and not proceed.
Is that how I should look at it?
Moderator
It seems that determining how my company RTOW charts have been devised is one matter, as is the identification of any other obstacles beyond the surveyed area.
You should have some guidance as to how things are done etc in whatever general information is included in your Ops Manual performance section ? Otherwise, why not just ask the ops eng boss for the answers ? If he/she doesn't want to talk then I'd be concerned.
The rest of your post presumes that the aircraft is WAT limited in all segments regardless and this doesn't apply usually. While your calculations might give you a feel for the conservative side of things, it probably doesn't provide much useful data. You really need to plug real numbers into the AFM. I presume that you have access to an AFM ? - that doesn't necessarily follow as your fleet may carry the ops manual in lieu of the AFM per regulatory concession which is typical for airline operators.
First segment may also come into the calculation for your Model ?
there is an MSA of 3,000' and we use an acceleration altitude of 1,700' (which is 400 and something feet AGL in this case).
Generally MSA is a bit of a crude sledgehammer when looking at takeoff flight paths. What is required is to match the AFM profile to the obstacle splay profile
there is no way we will reach 3,000' within the 25nm of the MSA.
Nor is there a necessary requirement to do so .. providing that the takeoff net obstacle clearances are being met.
need to manoeuvre within the MSA until either the MSA or LSALT was reached. Which would entail very small bank angles to preserve any of that 53 fpm available.
Again, the pilot would need to know the detailed obstacle environment. This is something that the ops eng folk should be providing for you in the case of a critical aerodrome.
Having said that, there have been more than a few cases in the past where I have upset the locals by climbing in the circuit to get an appropriate height prior to setting course, especially at night, if I haven't got the obstacle data to my satisfaction.
Is that how I should look at it?
Sounds like you are a pragmatic and conservative chap - what now counts is for you to find out what the operator is giving you in the way of information and, if you aren't happy with it, pursue it with the ops eng folk.
You should have some guidance as to how things are done etc in whatever general information is included in your Ops Manual performance section ? Otherwise, why not just ask the ops eng boss for the answers ? If he/she doesn't want to talk then I'd be concerned.
The rest of your post presumes that the aircraft is WAT limited in all segments regardless and this doesn't apply usually. While your calculations might give you a feel for the conservative side of things, it probably doesn't provide much useful data. You really need to plug real numbers into the AFM. I presume that you have access to an AFM ? - that doesn't necessarily follow as your fleet may carry the ops manual in lieu of the AFM per regulatory concession which is typical for airline operators.
First segment may also come into the calculation for your Model ?
there is an MSA of 3,000' and we use an acceleration altitude of 1,700' (which is 400 and something feet AGL in this case).
Generally MSA is a bit of a crude sledgehammer when looking at takeoff flight paths. What is required is to match the AFM profile to the obstacle splay profile
there is no way we will reach 3,000' within the 25nm of the MSA.
Nor is there a necessary requirement to do so .. providing that the takeoff net obstacle clearances are being met.
need to manoeuvre within the MSA until either the MSA or LSALT was reached. Which would entail very small bank angles to preserve any of that 53 fpm available.
Again, the pilot would need to know the detailed obstacle environment. This is something that the ops eng folk should be providing for you in the case of a critical aerodrome.
Having said that, there have been more than a few cases in the past where I have upset the locals by climbing in the circuit to get an appropriate height prior to setting course, especially at night, if I haven't got the obstacle data to my satisfaction.
Is that how I should look at it?
Sounds like you are a pragmatic and conservative chap - what now counts is for you to find out what the operator is giving you in the way of information and, if you aren't happy with it, pursue it with the ops eng folk.
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3rd segment confusion
hi all
about the clarity on 3rd seg.... is a level segment but for net gradient req -0.8%, this negative dip in height getting compensated by equivalent increase in horizontal dist et al
my understanding of this has been..
when i reduce level segment by 0.8% , i go below the level segment height to a certain point. from this point i climb at the stipulated climb gradient and where this again meets the level segment height gives me the required level segment.
this has incorporated the equivalent distance increase.
am i too off the mark ???
about the clarity on 3rd seg.... is a level segment but for net gradient req -0.8%, this negative dip in height getting compensated by equivalent increase in horizontal dist et al
my understanding of this has been..
when i reduce level segment by 0.8% , i go below the level segment height to a certain point. from this point i climb at the stipulated climb gradient and where this again meets the level segment height gives me the required level segment.
this has incorporated the equivalent distance increase.
am i too off the mark ???
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mutt, I concur with
That's why I don't understand when folks refer to certification when talking about PANS OPS instrument procedures. However from the pilot point of view certification is secondary whereas compliance with the given instrument procedures is primary target. In my understanding the acceleration segment has been deleted outta GO AROUND procedure meaning that the required missed approach gradient must be achieved till the final phase. In practical terms I have no idea when the min of obstacle clearance of 164 ft is achieved except when I'm at the MSA or final level off ALT, whichever is lower. Meaning that the required MA climb gradient must be achieved and maintained till MSA or published level off ALT. Let's SE come into play for GA, now in case the published MA is followed, knowing that there's no level acceleration segment unlike in EO SID, a level flight must not be initiated before the MSA or the published level OFF ALT. The question is how was the GA performance calculated to follow published SID SE? I suppose since the company gives me the choice it's all been taken care of unless I misunderstood the implication of the acceleration segment elimination. I'd appreciate the comments from the performance gurus as well.
I would have thought that PANS OPS 4 and Part 25 certification are two completely different animals...
Moderator
I think that you are trying to read too much into things and, as a consequence, making it harder to understand than it is ...
when i reduce level segment by 0.8%
you don't have to worry about any reduction - it's built into the AFM calculations.
So,
(a) you climb (with real world OEI performance) in the second segment to, say, somewhere around 400 ft. However, the AFM takes you (at net performance) to a lower height something less than 300 ft. This lower height is relevant to the obstacles, not your altimeter height.
(b) then, at the gross altimeter height you accelerate, nominally level, clean up and eventually achieve final climb speed. However, the NFP acceleration is done (for obstacles) at the lower NFP height and, being a degraded acceleration, takes a longer distance. End result is that, at the end of the NFP third segment, the real aircraft is well on the way into the fourth segment. When you end up at 1500 ft in the aircraft, the NFP is still way, way underneath you and the NFP doesn't achieve 1500 ft until a considerable distance further on .. and you base obstacle clearance on this lower profile.
(c) for the pilot not wanting to die on the surface of the obstacle, the main place to worry, and fly really accurately, is in the early second segment .. the further away you get from the runway, the higher the aircraft gets above the obstacles.
(d) a lot of folk have this idea about the aircraft OEI being 35 ft above obstacles miles out from the runway. Not so - the NFP might be in that predicament down there ... you are progressively and considerably above.
I go below the level segment height to a certain point.
No.
You will be flying level or, in the higher performing aircraft, a shallow climb. There is no intent that either the aircraft or the NFP calculations see a descent.
However from the pilot point of view certification is secondary whereas compliance with the given instrument procedures is primary target.
The certification (Design Standards) aren't overly interested in the missed approach - that being an operational concern. Caveat relates to the landing and missed approach WAT requirements but that's about the extent of it. Once you observe the WAT limits in determining the TOW, you have addressed the certification bits.
PANS OPS looks at how one might go about designing procedures and such like.
The silly situation is to let the aircraft head off down into the letdown WITHOUT having had a looksee at what you might be able to do IF one quits (or has already quit). The AFM doesn't give you much in the way of an easy way to calculate a missed approach climb but, with a bit of engineering pushing and pulling, the available information can be reworked to give you something equivalent to a takeoff analysis. Might even need a bit of simple flight testing to get some quantitative data to fill in the gaps.
meaning that the required missed approach gradient must be achieved till the final phase.
.. or you do something more rational which suits the aircraft and keeps you above the rocky bits.
In practical terms I have no idea when the min of obstacle clearance of 164 ft is achieved except when I'm at the MSA or final level off ALT, whichever is lower.
Which is the problem with the operational side of things - unless you do a rational analysis you are playing Russian Roulette, pure and simple.
The question is how was the GA performance calculated to follow published SID SE?
.. it wasn't .. that's a problem belonga the pilot and operator. Feasibly, the operator OUGHT to make sure that any critical approaches have been run through a rational ops eng analysis to come up with a specific procedure to get you out of there if it all goes pear shaped ...
I suppose since the company gives me the choice it's all been taken care of
.. now, that's a BIG assumption on your part ... I would incline to the view that the company which prescribes step A, step B, step C ... puts the pilot in the better situation .. presuming that those steps are based on a rational engineering analysis.
when i reduce level segment by 0.8%
you don't have to worry about any reduction - it's built into the AFM calculations.
So,
(a) you climb (with real world OEI performance) in the second segment to, say, somewhere around 400 ft. However, the AFM takes you (at net performance) to a lower height something less than 300 ft. This lower height is relevant to the obstacles, not your altimeter height.
(b) then, at the gross altimeter height you accelerate, nominally level, clean up and eventually achieve final climb speed. However, the NFP acceleration is done (for obstacles) at the lower NFP height and, being a degraded acceleration, takes a longer distance. End result is that, at the end of the NFP third segment, the real aircraft is well on the way into the fourth segment. When you end up at 1500 ft in the aircraft, the NFP is still way, way underneath you and the NFP doesn't achieve 1500 ft until a considerable distance further on .. and you base obstacle clearance on this lower profile.
(c) for the pilot not wanting to die on the surface of the obstacle, the main place to worry, and fly really accurately, is in the early second segment .. the further away you get from the runway, the higher the aircraft gets above the obstacles.
(d) a lot of folk have this idea about the aircraft OEI being 35 ft above obstacles miles out from the runway. Not so - the NFP might be in that predicament down there ... you are progressively and considerably above.
I go below the level segment height to a certain point.
No.
You will be flying level or, in the higher performing aircraft, a shallow climb. There is no intent that either the aircraft or the NFP calculations see a descent.
However from the pilot point of view certification is secondary whereas compliance with the given instrument procedures is primary target.
The certification (Design Standards) aren't overly interested in the missed approach - that being an operational concern. Caveat relates to the landing and missed approach WAT requirements but that's about the extent of it. Once you observe the WAT limits in determining the TOW, you have addressed the certification bits.
PANS OPS looks at how one might go about designing procedures and such like.
The silly situation is to let the aircraft head off down into the letdown WITHOUT having had a looksee at what you might be able to do IF one quits (or has already quit). The AFM doesn't give you much in the way of an easy way to calculate a missed approach climb but, with a bit of engineering pushing and pulling, the available information can be reworked to give you something equivalent to a takeoff analysis. Might even need a bit of simple flight testing to get some quantitative data to fill in the gaps.
meaning that the required missed approach gradient must be achieved till the final phase.
.. or you do something more rational which suits the aircraft and keeps you above the rocky bits.
In practical terms I have no idea when the min of obstacle clearance of 164 ft is achieved except when I'm at the MSA or final level off ALT, whichever is lower.
Which is the problem with the operational side of things - unless you do a rational analysis you are playing Russian Roulette, pure and simple.
The question is how was the GA performance calculated to follow published SID SE?
.. it wasn't .. that's a problem belonga the pilot and operator. Feasibly, the operator OUGHT to make sure that any critical approaches have been run through a rational ops eng analysis to come up with a specific procedure to get you out of there if it all goes pear shaped ...
I suppose since the company gives me the choice it's all been taken care of
.. now, that's a BIG assumption on your part ... I would incline to the view that the company which prescribes step A, step B, step C ... puts the pilot in the better situation .. presuming that those steps are based on a rational engineering analysis.
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J.T the company publishes on 10/20-7 special EO SID with the analysis for the GA when to follow the published MA and when the EO SID for each RWY and aircraft type. Let's take a practical example LEMD RWY 33L for 772/3 the table says to follow the published MA without restrictions on temperature. Analysis has been made using MLW. RTH is 2000 ft and the final level off is 5000 ft MSA is 4300 this is where I'm gonna level off SE following the MA and the company's policy. The description says that following the published MA is the preferred procedure and level OFF ALT should be the final ALT on the MA. It's a clear cut statement to me. In any case I can always revert to the EO SID in case of doubt. I was gonna compare to the way the others do it and there's no better way to it but to ask for alternative opinion here. Anyways thanx for respons J.T.
Last edited by 9.G; 1st Mar 2011 at 00:17.