Climb gradient
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Climb gradient
If there is no quoted climb gradient for the SID or missed approach what is the assumed gradient? This may have relevance to a single engine go-around or an engine failure on take- off. I am aware of emergency turn or escape manoeuvres when quoted but what is the procedure if they are not?
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Procedure design is not my area of practice, but the requirements are specified in PANS/OPS (ICAO Doc 8168).. I don't have the book to hand just now but the minimum design gradient (if nothing is specified otherwise) is 3.3 percent gross (2.5 net).
If the terrain requires something higher than this, then the SID will have an appropriate note.
This minimum design gradient means that, in the OEI case at decent (commercial)weights, one ought not to follow the SID in ignorance unless the runway escape procedure so specifies.
Unless the surrounding terrain is reasonably benign and the takeoff can be continued OEI straight ahead, then the company ought to have specified a suitable escape procedure.... otherwise the pilot is between a rock and a hard place.
One needs to keep in mind that the third segment acceleration complicates the analysis somewhat.
[ 01 September 2001: Message edited by: john_tullamarine ]
If the terrain requires something higher than this, then the SID will have an appropriate note.
This minimum design gradient means that, in the OEI case at decent (commercial)weights, one ought not to follow the SID in ignorance unless the runway escape procedure so specifies.
Unless the surrounding terrain is reasonably benign and the takeoff can be continued OEI straight ahead, then the company ought to have specified a suitable escape procedure.... otherwise the pilot is between a rock and a hard place.
One needs to keep in mind that the third segment acceleration complicates the analysis somewhat.
[ 01 September 2001: Message edited by: john_tullamarine ]
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Nothing to do with gross or net - those are certification terms.
The SID or omnidirectional departure - unless otherwise stated, either on plate or in particular countrys AIP - requires 3,3% according to ICAO doc 8168. This consists of 2,5% OIS and 0,8% increasing obstacle clearance (so OK, OK, I know - you could call this gross and net...
)
The missed approach requires 2,5% unless...
The SID or omnidirectional departure - unless otherwise stated, either on plate or in particular countrys AIP - requires 3,3% according to ICAO doc 8168. This consists of 2,5% OIS and 0,8% increasing obstacle clearance (so OK, OK, I know - you could call this gross and net...
)The missed approach requires 2,5% unless...
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JT,
As Ivan sez, it is not "gross vs net", which are aircraft performance related terms. If you were designing SID compliant SDPs, then you would need to add your "net" decrement to the 3.3% or higher published gradient. The procedure design does not cater for OEI or TEI operations: the former is "any aircraft" and the latter is "aircraft specific".
The procedure design consideration of OIS + 0.8% reflects the environmental reality that preservation of an obstacle clearance height requires consideration of the exposure window. The further away the obstacle, the greater the opportunity for the elements to degrade the buffers.
As Ivan sez, it is not "gross vs net", which are aircraft performance related terms. If you were designing SID compliant SDPs, then you would need to add your "net" decrement to the 3.3% or higher published gradient. The procedure design does not cater for OEI or TEI operations: the former is "any aircraft" and the latter is "aircraft specific".
The procedure design consideration of OIS + 0.8% reflects the environmental reality that preservation of an obstacle clearance height requires consideration of the exposure window. The further away the obstacle, the greater the opportunity for the elements to degrade the buffers.
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Chaps,
I have no interest in arguing semantics - a fairly pointless exercise unless you are into editing dictionaries.
As a performance engineer I use and am comfortable with the philosophy of gross/net gradients - if you are more comfortable with something else in the way of descriptors, then that is fine. One of the other correspondents suggested the use of 152 ft/nm in lieu of 2.5 percent - all fine and dandy - one should just use the slant with which one is most comfortable. The main aim is not to go hairing off with no idea of the situational awareness requirements for the particular runway and aerodrome.
I think that we each understand where the other is coming from.
More importantly, I suggest for the discussion, the average pilot has a limited, if much at all, knowledge of the ICAO Doc and Procedure Design but is fairly au fait with the idea of the heavy aircraft segment gradient system.
The point remains, though, that the run of the mill ICAO (Pans Ops) SID, without annotation, involves a 2.5/3.3 gradient profile and this is what the average civil pilot has to content with.
An ops engineer is not going to use the SID track inferred obstacle profile without checking the discrete obstacle data. This is due to the fact that procedures designers generally work their obstruction profiles a little more conservatively (due to the terrain data with which they often have to work) than the ops engineer can tolerate.
However, for the pilot left to his own devices, the SID figures at least give some information and this was, I suspect, the intent of the original question.
Most importantly, at commercial weights, it is potentially suicidal to head off along the SID following an early failure.
Further, if the operator doesn't consider the failure following V1 set of cases (and I believe that many don't) then the only reasonable way to address the failure case for the conservative pilot is to follow the nominated V1 failure escape path (if provided) for all takeoffs.
If a specific escape is not provided, then that may permit an inference that the straight ahead path is OK ... but for how far out ? ... best ask the guys who did the analysis.
[ 02 September 2001: Message edited by: john_tullamarine ]
I have no interest in arguing semantics - a fairly pointless exercise unless you are into editing dictionaries.
As a performance engineer I use and am comfortable with the philosophy of gross/net gradients - if you are more comfortable with something else in the way of descriptors, then that is fine. One of the other correspondents suggested the use of 152 ft/nm in lieu of 2.5 percent - all fine and dandy - one should just use the slant with which one is most comfortable. The main aim is not to go hairing off with no idea of the situational awareness requirements for the particular runway and aerodrome.
I think that we each understand where the other is coming from.
More importantly, I suggest for the discussion, the average pilot has a limited, if much at all, knowledge of the ICAO Doc and Procedure Design but is fairly au fait with the idea of the heavy aircraft segment gradient system.
The point remains, though, that the run of the mill ICAO (Pans Ops) SID, without annotation, involves a 2.5/3.3 gradient profile and this is what the average civil pilot has to content with.
An ops engineer is not going to use the SID track inferred obstacle profile without checking the discrete obstacle data. This is due to the fact that procedures designers generally work their obstruction profiles a little more conservatively (due to the terrain data with which they often have to work) than the ops engineer can tolerate.
However, for the pilot left to his own devices, the SID figures at least give some information and this was, I suspect, the intent of the original question.
Most importantly, at commercial weights, it is potentially suicidal to head off along the SID following an early failure.
Further, if the operator doesn't consider the failure following V1 set of cases (and I believe that many don't) then the only reasonable way to address the failure case for the conservative pilot is to follow the nominated V1 failure escape path (if provided) for all takeoffs.
If a specific escape is not provided, then that may permit an inference that the straight ahead path is OK ... but for how far out ? ... best ask the guys who did the analysis.
[ 02 September 2001: Message edited by: john_tullamarine ]
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EMB145,
Further to your email, I note that we only answered part of your question. The second half was really asking what to do if your employer does not provide you with adequate OEI escape data, n'est ce pas?
A note of caution about SIDs - they can have gradients driven by airspace and noise abatement considerations as well as terrain. Thus they may be excessively conservative.
If we restrict the discussion to EMB 145 class aeroplanes, it makes it a little easier, simply because the runway requirements mean that there most likely will be a bunch of runway related surveys done. The following link is useful background - note that Oz has some variations from ICAO:
Australian Aerodrome Rules
Most countries publish the obstacle clear take-off gradient with an indication of the survey length. Note that for Code 1 and 2 runways, the survey may only be very short and thus may stop short of significant obstacles. If the runway is an instrument runway, then you will invariably be given circling minima and LSALTs for 25 miles and occasionally 10 miles.
If you have ICAO circling minima, then regardless of your actual aircraft category, you can build up a picture of the effect of close-in obstacles. With your particular aircraft in mind, look at what height you should achieve at each relevant distance presuming Vef failure (worst case). If you cannot achieve any of the minimum circling altitudes (in your case, Cat E is probably the earliest) then you are committed to keep climbing straight ahead if you have no other path of confirmed lower gradient. Straight ahead at most aerodromes is OK for obstacles because they try to build aerodromes aligned with the best approach and departure paths, local prevailing winds permitting. Most final instrument approach tracks follow the lowest gradients, but remember that you rarely have the climb performance to match the approach gradients!!
As soon as you are able to achieve one of the myriad of LSALTs then you can manoeuvre safely while achieving your next required altitude or recovery to the aerodrome.
Once you have that picture clear, your departures should be planned to achieve the various LSALTs while the engines are all still working - then if one of them fails, you have the flexibility to manoeuvre without the same degree of "sphincter clench"!
This is a bit vague, only because I cannot imagine any regular operation in the presence of terrain without proper obstacle analysis. Any time you cannot achieve a safe flight path straight ahead because you lack data, somebody has to get proper data or you are failing in your duty of care.
Further to your email, I note that we only answered part of your question. The second half was really asking what to do if your employer does not provide you with adequate OEI escape data, n'est ce pas?
A note of caution about SIDs - they can have gradients driven by airspace and noise abatement considerations as well as terrain. Thus they may be excessively conservative.
If we restrict the discussion to EMB 145 class aeroplanes, it makes it a little easier, simply because the runway requirements mean that there most likely will be a bunch of runway related surveys done. The following link is useful background - note that Oz has some variations from ICAO:
Australian Aerodrome Rules
Most countries publish the obstacle clear take-off gradient with an indication of the survey length. Note that for Code 1 and 2 runways, the survey may only be very short and thus may stop short of significant obstacles. If the runway is an instrument runway, then you will invariably be given circling minima and LSALTs for 25 miles and occasionally 10 miles.
If you have ICAO circling minima, then regardless of your actual aircraft category, you can build up a picture of the effect of close-in obstacles. With your particular aircraft in mind, look at what height you should achieve at each relevant distance presuming Vef failure (worst case). If you cannot achieve any of the minimum circling altitudes (in your case, Cat E is probably the earliest) then you are committed to keep climbing straight ahead if you have no other path of confirmed lower gradient. Straight ahead at most aerodromes is OK for obstacles because they try to build aerodromes aligned with the best approach and departure paths, local prevailing winds permitting. Most final instrument approach tracks follow the lowest gradients, but remember that you rarely have the climb performance to match the approach gradients!!
As soon as you are able to achieve one of the myriad of LSALTs then you can manoeuvre safely while achieving your next required altitude or recovery to the aerodrome.
Once you have that picture clear, your departures should be planned to achieve the various LSALTs while the engines are all still working - then if one of them fails, you have the flexibility to manoeuvre without the same degree of "sphincter clench"!
This is a bit vague, only because I cannot imagine any regular operation in the presence of terrain without proper obstacle analysis. Any time you cannot achieve a safe flight path straight ahead because you lack data, somebody has to get proper data or you are failing in your duty of care.
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Take it easy on me guys -- I'm new.
Unfortunately, I know way too much about this particular topic. To answer EMB145's questions simply, in the United States, the minimum assumed climb gradient for BOTH departures and missed approach procedures is 200 ft/NM or 3.3%.
The missed approach gradient was, until recently, thought by most to be 152 ft/NM or 2.5%; however, the FAA has changed its policy in this area.
As far as PANS-OPS goes, the departure criteria is the same, and I do not know if they've followed suit on the change to missed approach procedures or not.
Unfortunately, I know way too much about this particular topic. To answer EMB145's questions simply, in the United States, the minimum assumed climb gradient for BOTH departures and missed approach procedures is 200 ft/NM or 3.3%.
The missed approach gradient was, until recently, thought by most to be 152 ft/NM or 2.5%; however, the FAA has changed its policy in this area.
As far as PANS-OPS goes, the departure criteria is the same, and I do not know if they've followed suit on the change to missed approach procedures or not.
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OldRed
Welcome to Pprune Tech Forum, we always love new faces to keep John_Tullamarine on his toes
The change that you are talking about is shown in the 2001 AIM, 5-4-19, A-301 with a change bar right beside it. Have you got a TERPS reference for this change?
One thing that I would like to point out to you is that we are an international forum, J_T and 4-Dogs are operating under the Australian regulations which are a lot more strict/sensible than the FAR's which i get to use.
Mutt
Welcome to Pprune Tech Forum, we always love new faces to keep John_Tullamarine on his toes
The change that you are talking about is shown in the 2001 AIM, 5-4-19, A-301 with a change bar right beside it. Have you got a TERPS reference for this change?
One thing that I would like to point out to you is that we are an international forum, J_T and 4-Dogs are operating under the Australian regulations which are a lot more strict/sensible than the FAR's which i get to use.
Mutt
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Welcome Old Red,
Great handle, particularly as both JT and myself are publicly exposed as oenologically equivalent to French Oak barrels - that is, we perform best when filled with Old Red!
I don't have easy access to the AIM but I would like to know whether this change to 3.3% in TERPS is similarly constructed to minimum SID gradient, that is the universal 2.5% obstacle clearance plane/surface plus 0.8% or is it an attempt to get lower approach minima?
Does the change have any following in ICAO or is it a unilateral issue?
Great handle, particularly as both JT and myself are publicly exposed as oenologically equivalent to French Oak barrels - that is, we perform best when filled with Old Red!
I don't have easy access to the AIM but I would like to know whether this change to 3.3% in TERPS is similarly constructed to minimum SID gradient, that is the universal 2.5% obstacle clearance plane/surface plus 0.8% or is it an attempt to get lower approach minima?
Does the change have any following in ICAO or is it a unilateral issue?
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Thanks for your kind replies.
As far as I know, the "new" 3.3% gradient for missed approaches has not made it into US TERPs criteria yet. According to the FAA, the "change" wasn't really a change; rather, it was a clarification to something which had been agreed to in the late 1960s! I would expect to see further clarification within a year.
The change is simply to provide an increasing amount of required obstacle clearance (ROC) rather than a fixed amound of ROC determined by the height at MDA. The surface is constructed just like a departure procedure: a 2.5% obstacle identification surface with 0.8% of ROC on top.
This change was not intended as a method to decrease minimums; it was intended to increase ROC.
As I mentioned earlier, I know of no plans by the ICAO to follow suit.
As far as I know, the "new" 3.3% gradient for missed approaches has not made it into US TERPs criteria yet. According to the FAA, the "change" wasn't really a change; rather, it was a clarification to something which had been agreed to in the late 1960s! I would expect to see further clarification within a year.
The change is simply to provide an increasing amount of required obstacle clearance (ROC) rather than a fixed amound of ROC determined by the height at MDA. The surface is constructed just like a departure procedure: a 2.5% obstacle identification surface with 0.8% of ROC on top.
This change was not intended as a method to decrease minimums; it was intended to increase ROC.
As I mentioned earlier, I know of no plans by the ICAO to follow suit.
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Give me a break, Mutt .. I'm just a boring old engineer who likes to stir the pot a little ... and, indeed, a very warm welcome to Old Red - we need a procedures specialist to keep the rest of us honest in respect of that discipline ...
Actually, the question of Australian things has become a bit hazy in recent years. First, I've been away for sufficient time now that I am almost a stranger there. Second, due to the active involvement of various Industry interests over the past however many years, Australia largely has thrown out the baby with the bathwater. Much of what was uniquely useful is now gone and, to an increasing extent, the Australian requirements substantially mirror those of the US.
It follows that Richard and I have more than a passing interest in the US rule scene. JAR-OPS, with which I am trying to come to grips at the moment, appear to confuse things with even more skill than the Americans....
Richard, being an oenological enthusiast in the company of like-minded people (although most of us claim skill only in respect of post manufacture quality assurance testing programs), is, without any possible doubt, a fine fellow ...
So far as this forum is concerned, there is, of course, a need for quantitative discussion when appropriate. I take the more general view, however, that it is equally if not more important, to talk in pertinent qualitative terms with which the line pilot often can be more comfortable - while still being challenged by the intellectual stimulation so important to engender constructive thought about the set of problems with which pilots are bedevilled.
Actually, the question of Australian things has become a bit hazy in recent years. First, I've been away for sufficient time now that I am almost a stranger there. Second, due to the active involvement of various Industry interests over the past however many years, Australia largely has thrown out the baby with the bathwater. Much of what was uniquely useful is now gone and, to an increasing extent, the Australian requirements substantially mirror those of the US.
It follows that Richard and I have more than a passing interest in the US rule scene. JAR-OPS, with which I am trying to come to grips at the moment, appear to confuse things with even more skill than the Americans....
Richard, being an oenological enthusiast in the company of like-minded people (although most of us claim skill only in respect of post manufacture quality assurance testing programs), is, without any possible doubt, a fine fellow ...
So far as this forum is concerned, there is, of course, a need for quantitative discussion when appropriate. I take the more general view, however, that it is equally if not more important, to talk in pertinent qualitative terms with which the line pilot often can be more comfortable - while still being challenged by the intellectual stimulation so important to engender constructive thought about the set of problems with which pilots are bedevilled.
