PPRuNe Forums approach climb 2.1% vs MACG 2.5% or greater

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 10th Mar 2011, 11:58 #1 (permalink) Join Date: Jan 2008 Location: home Age: 31 Posts: 82 approach climb 2.1% vs MACG 2.5% or greater Can someone explain to me the difference between 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. So which one do we use? Using FUERTEVENTURA ILS 01R as an example OAT 40 degrees and airport elevation 50 feet Approach climb limited weight = 74300kg (based on 2.1%) 4.0% MACG limited weight = 61700kg Obviously Im gonna use the lowest value, but I'd like to know why there are two types. What are the differences. Thanks in advance. Its been bugging me all morning trying to figure out the differences
 10th Mar 2011, 21:13 #2 (permalink) Join Date: Oct 2009 Location: UK Posts: 1,073 Hi aslan, I believe one of the conditions to be met for Max Landing Weight is the ability to make a (missed) Approach Climb Gradient of minimum 2.1%. Steeper Approach Climb gradients may be met by reducing the Landing weight, or by using a different Approach Flap setting (giving a less draggy GA Flap selection).
 10th Mar 2011, 22:53 #3 (permalink) Moderator   Join Date: Apr 2001 Location: various places ..... Posts: 4,956 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.
 10th Mar 2011, 23:10 #4 (permalink) Join Date: Jan 2008 Location: home Age: 31 Posts: 82 Thanks for the answers So John, from what I understand by what you wrote certification climb requirements are to do with approach climb gradient(2.1%) operational climb limits are to do with MACG(2.5% and upwards) In the tables i Have the MACG are much more restrictive as you say but they also are based on temperature and airfield altitude So I understand what you are saying but am I taking it up wrong?
 11th Mar 2011, 10:52 #5 (permalink) Join Date: Oct 2006 Location: USA Posts: 151 What it means Hello Aslan 1982, 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?
 11th Mar 2011, 12:00 #6 (permalink) Moderator   Join Date: Apr 2001 Location: various places ..... Posts: 4,956 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
 11th Mar 2011, 13:53 #7 (permalink) Join Date: Jan 2008 Location: home Age: 31 Posts: 82 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 So I have ELW = 60T Approach Climb limit = 69.4T MACG limit = 55.7t So obviously Im going to have to reduce my ELW to below 55.7 by some means, be it PAX, BAGS, fuel etc.....to be safe/legal to depart 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? If so why would I check both? Is the 2.1% just a figure for certification reasons and the 2.5% for actual operations? .. 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 John, would you mind explaining the different climb requirements or the differences between what WAT and MACG look at. Thank you all for ur time and help
 11th Mar 2011, 20:37 #9 (permalink) Join Date: Mar 2011 Location: engineer at large Posts: 1,339 Aslan...you are mixing and matching.....the 4.2% is the min all engine, not EO. The obstacle clearance surface is based on 2.5%, with a 1.52% NET... You must be able to meet these variables to use the procedure and the associated decision altitude. As an example, even though the 737-700 is, by criteria, Class C, your configuration may push you into Class D, and therefore you must use the proper Class on the chart.
11th Mar 2011, 20:52   #10 (permalink)

Join Date: Oct 2009
Location: UK
Posts: 1,073
Quote:
 the 4.2% is the min all engine, not EO.
Er ... no.

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.

 12th Mar 2011, 03:41 #12 (permalink) Join Date: Oct 2006 Location: USA Posts: 151 John No problem John, This forum is a nice place to address these issues. It is only a pity that these things are not properly addressed during ground school when preparing for the ATPL. Cheers PUA
 12th Mar 2011, 07:30 #13 (permalink) Join Date: Dec 2007 Location: paradise Posts: 554 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.
 12th Mar 2011, 08:06 #14 (permalink) Join Date: Jul 2009 Location: France - mostly Age: 73 Posts: 1,322 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. Regards, HN39
 12th Mar 2011, 08:35 #15 (permalink) Moderator   Join Date: Apr 2001 Location: various places ..... Posts: 4,956 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. .. enough reminiscing.
12th Mar 2011, 10:05   #17 (permalink)

Join Date: Jul 2009
Location: France - mostly
Age: 73
Posts: 1,322
Quote:
 Originally Posted by PUA 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.
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.

Regards,
HN39

 12th Mar 2011, 11:17 #18 (permalink) Join Date: May 2004 Location: prime meridian Posts: 31 a case in point - Chek Lap Kok Dear asian '82, You might like to look at these charts (from AIP HongKong - VHHH): http://www.hkatc.gov.hk/HK_AIP/AIP/AD/HK_AD2-92A.pdf http://www.hkatc.gov.hk/HK_AIP/AIP/AD/HK_AD2-91A.pdf see the statement in bold lettering just before the missed approach description. 'pinsan
 12th Mar 2011, 11:39 #20 (permalink) Join Date: Jan 2008 Location: home Age: 31 Posts: 82 Thanks 'pinsan for your input At FUE the is a similar option MACG 4.0% = DA:270 MACG 2.5% = DA:303 This is an extract from my OPS Manual 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%.

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