View Full Version : Landing climb limit and approach climb limit

Pete the Pilot
4th Sep 2001, 17:06
Whats the difference?

App climb is for 1 engine and ldg climb is for 2 but why and how are the limits used operationally?


4th Sep 2001, 21:42
You can thank the FARS for having both of these limitations; you are obliged to follow the most restrictive.

Approach Climb
Allows for a missed approach where the go-around must be flown with the aircraft in the approach configuration. FAR 25.121(d) requires that the climb gradient is calculated where Vs in this approach configuration does not exceed 110% of the Vs for the related landing configuration. The steady gradient may not be less than:

2.1% for 2 engine aircraft
2.4% for 3 engine aircraft
2.7% for 4 engine aircraft.

The approach climb is demonstrated:
[1] with the critical engine inoperative and the remaining engines at takeoff thrust.
[2] at the maximum landing weight
[3] at a climb speed not exceeding 1.5 Vs.
[4] with the landing gear retracted.

Landing Climb

Landing climb gradient charts are calculated for go-around with the aircraft in the landing configuration where all engines are operating and the landing gear is extended. FAR 25.119 requires the steady climb gradient to be not less than 3.2% with:

[1] the engines at the thrust available 8 seconds after the thrust levers are increased from the minimum flight idle to the takeoff thrust position.
[2] a climb speed of not more than 1.3 Vs.

Operationally these weights will allow you to execute a missed approach in most configurations. In some aircraft you will find that one of these limitations is always more restrictive, therefore you will only see one chart.

Mutt http://www.stopstart.fsnet.co.uk/mica/PNTSAce.gif

5th Sep 2001, 15:30
Following on from Mutt's dissertation ... (he does have all the numbers at his fingertips, does he not ? - fine lad that he is) ...

The certification bits are built into the AFM and limit the landing weight to the relevant WAT limit - whether it be approach climb or landing climb is irrelevant. This is to ensure that the aircraft has a likelihood of being able to climb during the initial missed approach.

From the pilot's point of view, some of the things to consider are

(a) make sure that the actual weight does not exceed the WAT limited weight.

(b) in the event of an AEO missed approach, it is a good idea to get back to the approach configuration without too much delay to better allow for a possible engine failure - and the normal aircraft procedural techniques we use do just this. So, for the 737 for example, the missed approach procedure calls for the flap to be retracted to 15 and the gear retracted.

(c) in the event of a OEI approach, we don't normally use more than approach flap and, when the gear is extended, the aircraft performance margins become quite marginal and the missed approach becomes a far more manipulatively critical exercise.

(d) if you were of a mind to do a OEI approach and landing with more than approach flap ... then I think you had better have a pretty good reason... ie a pretty serious sort of runway length problem.

[ 05 September 2001: Message edited by: john_tullamarine ]

6th Sep 2001, 00:52
Excellent bit of gen "MUTT" well done...

Pete the Pilot
6th Sep 2001, 17:43
Gooood stuff thanks..

10th Sep 2001, 06:12

Just to add to mutt and jt's answers, you did ask about the "operational" considerations.

I think it's important to note that AC and LC limits are for *planning the takeoff*. Once airborne, they are no longer limiting. That is to say, you under burn enroute, and upon arrival you are heavier than AC or LC as the case may be, you are legal to shoot the approach.

It's also important to recognize that the AC and LC limits are simply density altitude gradient capability weights, and have nothing
to do with the actual approach or runway in use. Let's say you are landing at a coastal airport with ocean off the end of 27, and mountains off the end of 09. The AC and LC limiting weights would be the same for both runways.

10th Sep 2001, 08:38

I have to say that I dont agree with you. For your situation, can you explain what you are going to do on an engine out approach when the single runway before you gets blocked? Or if you havent become visual at the MAP?

We use the following rules prior to takeoff. Landing weight must be based on:
1: Certificated Structural Landing Weight.
2: Approach Climb/ Landing Climb Limit Weight.
3: Field Length Limit Weight using the 60%/40% rule.

If the crew need to return after landing, they only need to comply with:
1: Approach Climb/ Landing Climb Limit Weight.
2: Field Length Limit weight using 100% of the runway length.

These rules allow for a landing without running off the end of the runway and also allow for a missed approach if needed.

Obviously these rules dont apply to the MUST GET DOWN NOW situation, but in general they work.

Can I ask what others are doing?



10th Sep 2001, 13:58
One further operational factor to take into account when considering all this is that the approach/climb gradient required when undertaking Cat2/3 in a 2 engined ac is increased from 2.5% to 3.0%. This comes into play at places like SZG in the winter. Sorry if this muddies the water even further!!

10th Sep 2001, 19:23
"Once airborne, they are no longer limiting"

I suggest this is not the case. WAT limits, which include the approach and landing climb cases are just that - airworthiness climb limits. Under emergency conditions fine to land overweight if that be appropriate. For other than an emergency all the normal rules apply - or you might find yourself in difficulty at the enquiry.

11th Sep 2001, 04:47
Ahh, disagreements. That's what makes a venue such as PPRuNe so valuable, so we may explore our differences.


I fully agree with the Part 25 numbers you quoted. No problem there. It's the APPLICATION of those numbers we seem to disagree on. Takeoffs and landings are not governed by Part. 25. They fall under the Part 121 rules.

121.195 determines your max TAKEOFF weight, even though it's heading is "Landing Limitations: Destination Airports."

Part 121.195 (a) and (b) state that "No person operating a turbine-engine-powered airplane MAY TAKE OFF THAT AIRPLANE at such a weight that", etc. It does NOT say that no person may LAND an airplane at a heavier weight.

121.195 (a) governs AC and LC limits, while 121.195 (b) governs the factored runway. I recently won an issue with the FAA on the operational application of 121.195 (b). They (from Nick Lacey's office) agreed that Landing Field Length as required under 121.195 (b) is NOT required once airborne.

Can we agree that AC and LC limits are NOT runway specific? If not runway specific, how can they address any obstacles for a specific runway? The weights would be the same making an approach towards the mountains, or making an approach away from the mountains. Simply being lighter than your AC/LC weight will NOT guarantee obstacle clearance on a missed approach! It will only guarantee a gradient, and that gradient may not be steep enough to miss the obstacles. It is up to the operator to publish engine-out procedures for obstacle clearance for engine-out takeoffs, and they can be used for an escape path in case of an engine-out missed approach.

It's important in this context to point out that you are not dispatched to specific RUNWAYS. You are dispatched to AIRPORTS. It is not necessary to obtain an ammended release if the planned runway changes while you are enroute.

[ 10 September 2001: Message edited by: quid ]

12th Sep 2001, 01:15

Two points, I suggest, to consider.

(a) does one not consider the case of RLW + planned burn to constitute one of the TOW limits to be considered for a particular sector ? The approach and landing WAT limits are part of the RLW calculations. FAR 121.195(a) seems to say just that sort of thing. I can only take the view that your philosophy might be a little adventuresome. A chap in your position might find it wise to take competent legal advice on his interpretation of the rules, I should think.

(b) the WAT limits have nothing at all to do with obstacles. They are airworthiness limits and only seek to provide a modest climb capability regardless of any other considerations. If there be obstacles then they are considered separately and usually cause a reduction in weight to suit the required obstacle clearance.

Regardless, the AFM imposes the WAT limits as TC limits. The pilot abuses such limits in other than emergency situations at his/her legal risk.

23rd Sep 2001, 10:03

Just drifted past and thought that one unresolved element was worth discussing.

That element is the tendency of PPRuNe discussions to cross the world without adequate recognition that each jurisdiction has subtle differences in both its rule sets and their application.

There is a previous discusion herein on the application by the FAA of despatch vs inflight landing distance factors, as well as identification of the significant differences that apply in Oz. Some of our newer readers need to note the limitations inherent in our discussions, lest they misapply some other country's rule in their own backyard.

Having noted that, a crucial bit of the original discussion is to identify the difference between certification requirements and operational requirements.

The certification requirements are all "flat earth" rules to ensure that the bluddy thing will fly with a modicum of ease. Approach climb limits ensure that there is some OEI climb capability at the other end and and the landing climb is there to stop the manufacturer from achieving the world's shortest landing distance by using flaps that render the aeroplane incapable of going around.

The operational limits are simply how we attempt to meld those "flat earth" capabilities into an environment full of lumps and bumps. We do a lot of planning for take-off and generally nothing for landing - one significant reason is an absence of agreed data on the geography of a missed approach. Think about the complexity of trying to work out the distance from the decision point to achieving a stable climb after reconfiguring for go-around from an ILS, runway-aligned NPA or a circling approach. Do the planning templates in TERPS or PANS-OPS really reflect real life?

Best of luck...

23rd Sep 2001, 11:58

Just found the previous discussion:

FAA Landing Distance (http://www.pprune.org/cgibin/ultimatebb.cgi?ubb=get_topic&f=3&t=001543&p=2)

:cool: :cool:

24th Sep 2001, 03:01
Richard is, of course, quite correct in observing that the rules and applications/interpretations will vary between States and Regulatory Offices - a problem with which we all are beset.

However, I would contend that the real concern is not what the Regulator says (that might lose you your licence), but what the Judge determines at the end of the court case, Coronial or whatever (that might bankrupt you or worse). I can bring to mind a number of people who most certainly do have this sort of view following unfortunate brushes with their relevant legal systems. If one inclines to such a philosophy, then a reasonable and sensible level of flight management conservatism is to be encouraged.

I would be very interested in the views of members regarding my usual approach to this problem, specifically in respect of landing distance factors and approach/landing WAT limits which appear to be the main thrust of this thread. I note that this is the approach I adopt in training programs with my students. All training discussions are, of course, predicated on compliance, to the extent reasonably practicable, with company requirements and recommended procedures.

My philosophical view is that operations fall into two categories -

(a) that preflight and inflight phase during which the pilot has the reasonable option of complying with the various certification and operational requirements as published both in regulatory documents (eg AFM) and regulator approved or accepted company documents (eg company AOM).

(b) that inflight phase where, due to circumstances which the commander has not been reasonably able to avoid, the available options may or may not reasonably permit the sensible application of the normal requirements.

My view is that, unless there be an emergency of some sort, then it may (from my point of view, read "will") be very difficult to justify the discretionary adoption of standards inferior to those published - in the face of a concerted effort by opposing counsel to demonstrate that one is an incompetent and reckless idiot - such effort having the goal of obtaining access to the operator's deep pockets or insurance. I further contend that the commander has an obligation, amongst all the other decision making considerations, to consider personal and company liability.

In respect of the landing case, consider the following scenario for discussion.

During an ETOPS sector, the aircraft

(a) has yet to reach the 60 minute radius of action and some problem occurs. My contention is that, if it be reasonably possible, the aircraft should be operated in a manner which does not involve intentional disregard of published requirements.

(b) is now beyond the 60 minute radius and operating under ETOPS approval provisions. Planning prior to this point has been predicated on meeting all the relevant requirements as published in company procedures. Now a problem occurs which prompts the commander to seek an aerodrome without undue delay.

(i) If there be only one runway physically available (which would have been considered in the planning process) then the decision process is programmed.

(ii) If there be a number of physically available aerodromes, some of which might not have been available during the pre-ETOPS planning phase due to, for instance, distance considerations, then I contend that all now become options for the commander's consideration.

Consider the situation now, where the commander has determined that, other things being reasonably equal, there may be, say, three runways physically available for the subsequent aircraft recovery. These runways may involve varying considerations of WAT limits, distance factors, and flight distance.

Suppose that

(a) runway (i) has more than normal AFM-required distance available (say, 1.67 plus), the weather is desirable but the WAT limits would be compromised unless the aircraft held for some time. Furthermore, the aerodrome is located beyond the permitted ETOPS planned radius.

(b) runway (ii) has between the normal planned (1.67) and alternate (1.43) margins, is very much closer, but has extremely marginal weather or some significantly adverse facilities problem.

(c) runway (iii) has something only slightly in excess of available published unfactored distance, is quite close and is CAVOK.

My contention is that the decision process ought to rank these available options on a wide ranging consideration of risk and the preferred option is that which, in the opinion of the commander, offers the lowest overall risk. What are your thoughts ?

I have a particular concern with views which suggest that the average pilot can achieve unfactored landing distances in the real world. I reject the view that one should intentionally undershoot with a view to picking up some ground distance fat - the risk of an approach accident then becomes unacceptably high in a large aircraft. My view is that unfactored distances should be viewed only as reference information and have little to do with what the line pilot might be able to achieve in the heat of the moment. Certainly, from such flight tests involving performance landings as I have been involved with, I have the view that they are amongst the most hazardous and alarming of flight operations.

Richard and I have similarly jaundiced views of the idealised world of certification and the problems associated with its application to the nasty real world.

My attitude to missed approach considerations, especially OEI, is that the operator's ops eng people ought to do appropriate calculations, not all that dissimilar to RTOW calculations, for the miss. Such analyses are not at all difficult. The consideration of consequent liability might, however, be a little muddy.

[ 23 September 2001: Message edited by: john_tullamarine ]