Approach climb limited weights (2.1%) and Missed approach climb Gradient weights (2.5% or greater)
Here is what I know
- For Approach climb limited weights
-the aircraft climb capability in go around climb config with 1 engine inop, gear retracted and F15 must meet or exceed 2.1% climb gradient
- For CatII/III MACG limited weights at 2.5% climb gradient must be met(one engine out)
- Also for example at FUERTEVENTURA ILS 01R the MACG = 4.0%, so we must ensure that the landing weight does not exceed the MACG weight at the current conditions i.e Temperature and pressure Altitude . So for this we would use the tables for MACG limited weights for grad 4.0% (one engine out)
-The nominal climb gradient of a missed approach based on ICAO PANS-OPS is 2.5%
- Basically for both, if the weight is limiting i.e. less than max landing weight then this should be put in on the load sheet to determine allowed traffic load.
Simple once you put things into the right paddocks ..
(a) certification climb requirements
These relate to Design Standards requirements (eg FAR25) and impose MINIMUM climb capability to give the pilot some chance of going up when he/she desires - ie a limit on gross weight to make sure the aircraft can climb a little under specified circumstances.
These climb limits usually are referred to as WAT (maximum gross Weight for Altitude and Temperature) limits and ensure (at certification) that the aircraft has a modest climb capability in the takeoff, en-route, approach, and landing configurations.
WAT limits are across the board and have no interest in specific aerodromes or obstacles - they are still air line in the sand limits for the AFM.
(b) operational climb limits
There is a variety of these animals and the SID and missed approach requirements fit in here. Absolutely nothing to do with WAT limits and, near invariably, more restrictive.
I fully understand your worries and have had the same. Lucky that JAR-OPS came with an answer.
Approach climb and Landing climb are capability criteria only; they have nothing but absolutely nothing to do with the go-around. A bit the same as the take off second segment. (Still air anyway).
The go-around starts from a configuration and speed that is completely different then the one used for approach climb or landing climb, hence the data of these gradients cannot be used. Before JAR-OPS was implemented we used (for a twin) to refer to the WAT curve for the second segment that was 2,4 % and close to the 2,5 %. All this just to have an idea since nothing else was available.
JAR-OPS recognised this and imposed that, data that actually correspond to reality (configuration andspeed) be used.
I used to work for Emirates Airlines in the 90's and nobody in the training department understood what was really going on they probably still don't. So you are not the only one who raises a legitimate question.
Now the issue is basically not very important unless you consider situations at high and hot airports and the context of a CAT III approach with one engine inoperative. Or situations where an overweight landing has to be considered.
Now the question really is, until what altitude the gradient applies. Is it an average value or not?
In the tables i Have the MACG are much more restrictive as you say but they also are based on temperature and airfield altitude
.. for the same sort of reason that WAT charts are based on weights, altitudes and OATs - these are the principal things determining climb capability
However, WAT and missed approach climb are two different animals looking at different things .. while being similar in that they are looking at (different) climb requirements
The go-around starts from a configuration and speed that is completely different then the one used for approach climb or landing climb, hence the data of these gradients cannot be used.
I wouldn't go along with that statement - in what way is the missed approach configuration different to the WAT considerations ? The only reason we don't use WAT data for obstacle considerations is that the WAT limiting weight gives a low gradient. There is no reason why one can't use the WAT chart data for a LOWER calculated weight to achieve the obstacle clearance requirement ...
Before JAR-OPS was implemented we used (for a twin) to refer to the WAT curve for the second segment that was 2,4 % and close to the 2,5 %. All this just to have an idea since nothing else was available.
Again, I don't think so. The AFM gives plenty of climb data suitable for massaging into obstacle clearance numbers. An operator has, and always had, the ability to go out and do some flight test data to confirm analysis for whatever might have been desired. JAR-OPS might have codified some extra stuff but there is nothing terribly new in the world ...
I used to work for Emirates Airlines in the 90's and nobody in the training department understood what was really going on they probably still don't.
.. which is why the training folk should have referred the matters to the ops engineering specialists .. just like any other airline. I don't know the folk who do Emirates' work but they surely have an ops engineering section ?
Now the issue is basically not very important
.. and ANY place which has obstacle problems. If you don't get someone to do the sums .. how do you have any idea of whether you might be able to miss the rocky bits ?
Now the question really is, until what altitude the gradient applies. Is it an average value or not?
..depends on what the specific Reg you are looking at says and how one might interpret the words if they are not written reasonably clearly
Basically the reasons behind my questions is mainly for pre flight planning in the crew room and also because I like to know the reasoning behind it, instead of just agreeing/accepting it. Id like to be able to explain to someone why it is the way it is rather than just telling them, thats the way it is
So for another example...
lets say I'm flying to Salzburg
So in the crew room I get the weather, expected TOW, Landing weights etc...
So lets say (just for argument sake) the weather in Salzburg is +40 Degrees and wind 160/10 1013 hPA and CAVOK with no change through out the day Airport Elevation = 1411 My ELW is 60T
So i get some Plates and pick the ILS/DME 16 as most likely approach to be flown
So for RWY 16 it states that
CAT 1 MISSED APCH CLIMB ILS DME RWY 16 GRAD MIM 4.2%
CAT11 MISSED APCH CLIMB GRAD MIM 5.9%
So its CAVOK so I choose the CAT1
Now for dispatch planning I check my Approach Climb Limited Weight chart and it says (based on B737-800 26k 2.1% One engine out F15)
@40 deg Press Alt 2000 = limiting weight = 69400kg
Then I check my MACG charts (based on B737-800 26k 2.1% One engine out F15)
So for 4.5% (nearest/more limiting to 4.2%)
@40 deg Press alt 2000 - Limiting weight = 55700kg
From the top of my head, it has been a while since I went into the details of this matter. As such a closer look to the definitions may change my answer slightly but the philosophy will remain the same.
All performance issues are WAT related nothing special there.
Approach climb: While making the AFM Approach climb tables the constructer is allowed to use speeds up to 1, 4 Vs. This is close to min drag and will give the highest figures. These results are just to show a certain capability and have NO practical use. Dont ask me why a second segment is 2,4; 2,7 or 3,0% it is just the way it is and so in a similar way I do not know why they allowed 1,4 Vs to be used. I refer to Joop Wagemakers for more info.
Go around: If you make a go-around, you start from your approach speed using landing flaps and then retract the flaps to a go-around setting at the same speed. This is not 1, 4 Vs and as such the approach climb tables cannot be used even if they provide the possibility to select another gradient. Unless they also allow the use of different speeds. Some of them do.
But the problem of obstacle clearance remains and the 2,5 % gradient is no guarantee since it is referenced to still air.
I am not aware of any operator that makes an analysis similar to the one for Take Off for the Go-Around. That is to say who publishes max landing weights as function of temp, press altitude and wind to meet obstacle clearance. And if you really want to precise, does also take into account the effect of temperature on errors in the altimeter.
As I said before it is JAR-OPS that introduced the requirement to publish WAT curves that were based on realistic Go-Around speeds and configuration. In the same way, was it JAR-OPS that required accounting for loss of climb gradient during turns at 15 bank (Above this the requirement was already in place). Some things change over time. In the same way that the provision for acceleration segments were removed from the Go-Around segments. Nobody really knows why they did that.
So the speed you are using during the go-around is far from 1,4 Vs, hence the performance data are different. To reduce the gap, some connection was made between the approach flaps and landing flap setting that may be used based on the stall speeds (Factor 1,1) in both configurations. This led for example to the use of flaps 2 and flaps 10 on the 737-200. These settings are normally skipped in normal operation and were only used for certification reasons.
Emirates Airlines: EK had a GMFO that refused to listen to the performance engineer who resigned for that reason and joined Boeing as a performance engineer. Of course did the GMFO not allow the PE to resign, he fired him after he resigned, question of keeping his Ego in the right place. Both of us informed Boeing about their practices in order to get some feedback from them so we could use that to force the GMFO to listen. He refused and was fired himself. That Mr John Tullamarine is a reality and I do not think that has changed a bit. At a certain level in management CRM goes out of the window.
Practical use: Depending on aircraft type, temp and press altitude your app or landing climb limiting weight may be lower that the 2,5 % (go-around limiting weight) relative to the ground (wind included).
It is a bit the same as if you would take off from an extremely long runway facing the sea. You might be able to take off with a very high take off weight and no limitations as far as obstacles are concerned. However the second segment gradient will impose a limit although there is no real practical use obstacle wise. It will however imply that when you convert this gradient into level acceleration you will have a certain performance as a consequence of that gradient. Of course you must use the NETT and not the Gross acceleration.
So in general the Approach and Landing climb gradients are a bit the reverse of the second segment requirements for take off. You could approach an airport with an extremely long runway in an aircraft with powerful brakes imposing no problems for landing, even when landing in overweight. In these instances the approach and landing climb need to be complied with. If the temperature at your destination is below a certain value and you have used anti-ice or encountered icing conditions some big corrections on the limit weight lure around the corner.
Parallel with this, an analysis based on obstacle clearance for the Go-Around needs to be made. The question to be answered here is: do I apply the gradient till the end of the Go-Around or do I use an average value? Again this is very unpractical.
These gradients may prevent you to make an premeditated (N-1) CAT III approach at max landing weight at a high and hot airport even when you have a long runway ahead and a strong headwind.
Regulations: Regulations require an analysis to be made for N-1 during all phases of flight, except for an engine failure during Go-Around or on final. Now since Go-Around flap setting all engines is often the same as the one used for take off, and since the speeds used are close to each other you are a bit in the same situation.
This is the story of an engine failure during an approach where the all engine flap setting is maintained. A real challenge, and a lot of fun for those in the OPS management who have to take the decision.
The recommendation of Boeing was to get out of there, definitely if it was a severe damage. The recommendation of EK was to continue although they did not know why and so they used the approach climb gradient as a reference.
Last edited by Pitch Up Authority; 12th Mar 2011 at 19:02.
Reason: Post updated in Blue Print
It's the gradient you need to make in order to clear the obstacles from that approach at Salzburg, either with all engines running or engine out. We must consider an engine failure at "the most critical phase of the flight", so it needs to be taken into account.
(I'm not able to comment on the numbers as I don't have your paperwork.)
So is there a legal requirement to check Approach climb gradient limiting weights when I know that all charts are based on 2.5% MACG or greater, which are more limiting?
Again, one needs to keep in mind what the various checks set out to achieve -
(a) the approach climb WAT limit has to be checked as part of figuring the maximum permissible landing weight for the day. This is a basic part of the aircraft certification and is built into the AFM performance information.
If you don't have any other local constraints - obstacles, runway length, etc., then you finish up with a landing weight which looked only at the basic certification requirements and may well be limited by, say, approach climb WAT limits.
(b) now, in the same sort of way you worked your way down from the structural MLW to the (perhaps lesser) LW limited by approach or landing climb requirements, if there are other local considerations, then you need to continue the iteration until you have examined ALL the relevant possible restrictions on LW. The restriction which gives the LOWEST LW becomes the limiting case for the day and determines the MLW for the day.
In effect, you consider the WAT limiting elements every time as part of the AFM process and you also consider all the other stuff as you work your way through the exercise to tick all the boxes. That which limits you at aerodrome A yesterday need not be that which does so today at aerodrome B.
Is the 2.1% just a figure for certification reasons and the 2.5% for actual operations?
that's probably a reasonable comment. Main thing is that you MUST consider the WAT limit EVERY time but sums relating to obstacle clearance only are relevant if you have obstacles to consider. So, for instance, if you are approaching a runway on the coast with the miss over the sea from near the water's edge, then you probably aren't going to be harassed by obstacles (other than the normal transient considerations built into the aerodrome runway numbers - in this case, ships' masts)
.. the different climb requirements or the differences between what WAT and MACG look at.
The Design Standards (say, FAR 25) requires that the aircraft has a set of capabilities, including climb gradient. In the same way as you run through the runway limit charts to check on TODR, ASDR, etc., to make sure you have a reasonable chance of getting off, up and away close in, you need to check on the climb requirements to make sure you can keep doing the away bit and so on through the flight.
Certification looks at the various phases of flight and requires a climb capability to ensure that the aircraft can stay up (go up ?) rather than necessarily have to come down. For instance, refer to FAR 25.111 and subsequent which talk about climb matters (amongst other things)
The aircraft, as certificated, is deemed to be OK to go fly. However, in the real world, there are other things (obstacles, for instance) which might cause the basic certificated aircraft some grief so we have Operational Standards which consider such additional matters.
So, if you look at FAR 121.189 and subsequent you can get a feel for the operational rules. I am not an FAR specialist so others may chip in with further references appropriate to the discussion. However, this is a suitable place for you to start some reading, I suggest.
Main thing to keep in mind is that the airworthiness (Design Standards) and operational rules are there to give you a reasonable chance of getting from A to B without coming to grief somewhere along the way ...
Rather than have me just rabbit on, perhaps you can put further specific questions and we can have a go at answering them specifically ?
Caveat - the current specific rules may not apply in detail to a specific older certification Type
While making the Approach climb tables
The AFM and associated OEM documents will provide guidance relating to the operational techniques for missed approach. It is reasonable to presume that there will be some degree of consistency in such advice. I didn't think it necessary to belabour the point that the operator is perfectly free to go do some more sums and flight tests to satisfy the operator on any point of concern. The AFM, being concerned with airworthiness issues, will not necessarily be easy for the pilot to use without some competent and relevant PE skills. That's the way things are, I'm afraid ...
I am not aware of any operator that makes an analysis
Many don't, some do. I suggest that any for whom I, Old Smokey, and Mutt have worked .. and others I can bring to mind from the past will have had such considerations looked at. It is not a case of running such analyses for EACH runway .. but, certainly, it is good corporate governance for risk management of the nasty ones ...
was it JAR-OPS that required to account for loss of climb gradient during turns.
I suggest that turn loss accounting predates the EASA folk by many decades. It has been a requirement for as long as I can recall to address gradient loss for other than insignificant heading changes. The usual AFM, for takeoff, will contain a chart providing such decrement data. The same sort of philosophy is just as relevant to missed approach escape matters.
One needs to keep in mind that the Rulebook sets a minimum standard only. Sensible corporate risk management, in many cases, ought to dictate additional conservatism in various areas ....
That Mr John Tullamarine is a reality
I can't speak to your specific operator and experience but, certainly, I have observed some in the past which have done things I wouldn't condone. Also, if I have got up your nose a tad, that wasn't my intention and, for that, my apologies ... ?
aslan, 4.2. Go-Around Requirements 4.2.1. Normal Approach During dispatch, only the approach climb gradient needs to be checked, as this is the limiting one. The minimum required gradient is the one defined during aircraft certification (Approach Climb). Operators have a choice of go-around speed (from 1.23 VS1g to 1.41 VS1g), and configuration (3 or 2) to determine the Maximum weight limited by go-around gradient. In the rare case of a go-around limitation during dispatch, operators can select CONF 2 and 1.4 VS1g for go-around calculation, and should no longer be limited. Nevertheless, even if the regulation authorizes such assumptions, it is important to warn pilots about the speed and configuration retained, as soon as they are not standard (CONF 3 and 1.23 VS1g). In a normal approach, the required climb gradient is 2.1% for twin and 2.7% for four engine aircraft, independently of airport configuration and obstacles. During dispatch, operators can account for the gradient published in the airport approach chart.
Is the 2.1% just a figure for certification reasons and the 2.5% for actual operations?
For an airplane certificated under European airworthiness rules (JAR-AWO), 2.5 % is a certification WAT limit that applies regardless of obstacles for dispatch to an airport with a forecast of CAT II conditions. It is more restrictive than the 2.1 % that applies for CAT I because of the increased probability of go-around in CAT II conditions.
It is only a pity that these things are not properly addressed during ground school when preparing for the ATPL.
Ain't that the truth ...
I have seen the endorsement programmes vary from excellent to abysmal.
As a pilot, I was fortunate to have been exposed to the old AN (TAA and QF) systems in an earlier life and the folks running those shows were motivated to provide pilots with a lot of nice to know data. Wal Stack's QF notes, especially, are still quite highly prized for their reference value. John Walsh, Roger G and their successors at AN, and Peter T and his folk at TAA produced lots of equally useful material. I really think that a lot of the 60s-80s Australian airline pilot folks didn't quite understand just how lucky they were to have such folk as their instructors in the ground schools and their ops eng sections in the day to day stuff.
As an engineer, FT and ops eng happen to be the main interest thrust over my career .. although I ended up spending time in many and varied areas .. just the way things go, I guess.
The long time sorry state of ATPL training needs little comment ... at least, when I was involved actively in a long ago previous life, my theory students were dragged through much of the basics of the nitty gritty .. the exams being a sideline which most managed to pass without too much trouble. Likewise as a sim instructor .. many a student ended up with far more OEI knowledge than the customer may have thought necessary ...
In the PPRuNe environment, I am getting a little out of date with the specifics of the present regulatory operational requirements as I have been out of routine ops eng work in the day job for some years now. However, the basics haven't changed to any extent and, I suggest, the same considerations apply looking at the Regulatory and the sensible Corporate needs.
The imposed 2,5% gradient is there for obstacle clearance and so wind has its role to play.
2,5 % is used for all approaches NP till CAT III C if you want.
Does the Approach climb need to be respected at all times? The answer is Yes. Does the Landing climb need to be respected at all times? The answer is Yes. Does the Go-Around climb gradient need to be respected? The answer is Yes.
Do you need 2,5 % gradient in still air? The answer is No as long as you make the 2,5 % relative to the ground. Landing Climb gradient and Approach climb gradient will help you to get on the way.
As far as CAT III versus CAT II and CAT I are concerned. During a CAT III with a DH (let's say 50 ft) the aircraft is already changing it's pitch.
In case of a CAT II that is not the case so at 50 ft, the differences are minor.
And last but not least. Not everything is covered by regulations.
The real issue is however that NOT the safety of the passengers is important but yours. If you are fine they will be also.
Time to go to bed, I have a 12 hr flight ahead of me.
Do you need 2,5 % gradient in still air? The answer is No as long as you make the 2,5 % relative to the ground.
CS–AWO 243 Go-around climb gradient The aeroplane Flight Manual must contain either a WAT (Weight, Altitude, Temperature) limit corresponding to a gross climb gradient of 2·5%, with the critical engine failed and with the speed and configuration used for go-around, or the information necessary to construct a goaround gross flight path with an engine failure at the start of the go-around from the decision height.
Aircrafts are certified to conduct a missed approach and satisfy a Gradient of 2.1% - GROSS The configuration is: One Engine Inoperative Gear Up Go Around Flaps (15 on 737) G/A Thrust Speed must be <= 1.4 VSR
(Strictly speaking, the Flap Setting must be an intermediate flap setting corresponding to normal procedures whose stalling speed is not more than 110% of the final flap stalling speed)
Aircrafts are certified to conduct a missed approach and satisfy a Gradient of 3.2% - GROSS The configuration is: All Engines Operating Gear Down Landing Flaps (30 or 40 on 737) G/A Thrust The speed must be >= 1.13 VSR and VMCL It is also a requirement that full G/A thrust must be available within 8 seconds of the thrust levers forward from idle
JAA Low Visibility Climb
An Aircraft must be certified to conduct a missed approach and satisfy a Gradient of 2.5% - GROSS or the published Missed Approach Gradient The configuration is: One Engine Inoperative Gear Up Go Around Flap (15 on a 737) G/A Thrust This is only applicable if Low Visibility Procedures will be conducted with a DH of below 200 Ft or No DH
Max landing weight
The maximum landing weight for dispatch is the least of the:
Some specific procedures require a Net gradient of more than 2.5%. This will be indicated on the Chart i.e 4.2% at FUERTEVENTURA
So from the charts/info/tables available to me at dispatch, I have
1) Go around Climb 'approach Climb' Limited weights (2.1%) 2) Go around Cat II/III 2.5 % Missed Approach Climb Gradient limited weights - Cat2/3 approaches only 3)Missed Approach Climb Gradient limited weights (3.0%, 3.5%, 4.0%, 4.5% and 5.0%) - valid for NPA, ILS CAT I and CAT II/III 4)Max certified landing weight 5)Field limited landing weight based on current weather
So if the weather is above CAT I, the only chart I would be consulting is the Approach Climb 2.1% assuming no special MACG procedure at airport
If the weather is below CAT 1 and no special MACG procedure, I would refer to both the Approach climb(2.1%) and CAT II/III MACG (2.5%) and take the most limiting
If the weather is above CAT I and there is a special MACG procedure then I would refer to the Approach climb (2.1%) and the appropriate MACG table, lets say 4.5% for FEU and take the most limiting one
Obviously still considering the MLW and the Field limiting landing weight for all.
So after all that - I think Ive got a fair understanding of it all.
The nominal climb gradient of a missed approach based on ICAO PANS-OPS is 2.5%. At any airport where Jeppesen offers a choice of minima based on any other climb gradient, those associated with a 2.5% missed approach climb gradient must be used unless the airfield brief contains performance information enabling the use of a higher climb gradient.
So unless the airfield brief allows us to use the 4.0%, we must choose the higher 2.5% DA
Ive just checked the airfield brief for FUE and all it mentions is that there are two DA's based on 2.5% and 4.0%, nothing else Also the last time I flew there, I remember the captain saying in the cruise, can you check the MACG table for 4.0% against our est LW and OAT at FUE. I did and we were below the Limiting weight so we selected the lower DA. I.e. The 4.0%.