Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Landing Climb Limit Weight

Tech Log The very best in practical technical discussion on the web

Landing Climb Limit Weight

Old 2nd May 2014, 22:15
  #21 (permalink)  
 
Join Date: Jul 2009
Location: France - mostly
Age: 80
Posts: 1,689
Originally Posted by latetonite
You ever heard about performance requirements with the gear remaining down, if it is retractable? Anywhere?
See FAR 25.121(a) Takeoff, landing gear extended
HazelNuts39 is offline  
Old 3rd May 2014, 00:31
  #22 (permalink)  
 
Join Date: Aug 2007
Location: N/A
Posts: 157
Hazelnut. You really are confusing things with your approach climb theories.


Lets just clear this up. There is no misnomer. Boeing clearly define two distinct and non interchangeable limits. They are called 1) Landing climb weight limit and 2) Approach climb limit weight. They are so clearly different that the limits are even separately shown and separately labelled on the landing details page of the OPT section (dispatch) of the electronic flight bag whenever you do a calculation. So again no misnomer.


Only the landing climb weight limit is displayed in the FCOM/QRH because only the landing climb weight is used when performing the overweight landing cx list. If you are ever landing over this limit or overweight on one engine the cx list tells you to configure the approach with a reduced flap setting (very similar to approach climb limit config ). Clearly inferring that on this aircraft landing climb weight limit is always a greater consideration than approach climb limit.


To suggest that somehow the entire FAR flight test schedule for demonstrating approach climb limits can be substituted for gear locked down performance is an interesting theory.
8che is offline  
Old 3rd May 2014, 04:21
  #23 (permalink)  
 
Join Date: May 2001
Location: A few degrees South
Posts: 813
Haroon, a possible indication for the different given weights you found is the following:

In some manuals the 'landing climb limited weight', is the lower of the approach climb limit and the landing climb perfo limit.

As the approach climb is more limiting, they will quote this number.

Just my 2 cts.

As I now read through other replies, Hazelnuts seems to have given the same, correct answer.

Last edited by latetonite; 3rd May 2014 at 04:42. Reason: Not seeing other replies
latetonite is offline  
Old 3rd May 2014, 10:20
  #24 (permalink)  
 
Join Date: Jul 2009
Location: France - mostly
Age: 80
Posts: 1,689
8che,

I don't know how Boeing presents this information and the OP has not identified his source.

The Airplane Flight Manual (AFM) is the final authority on performance operating limitations and is required per FAR 25.1533(a)(2) to provide only the most limiting weight complying with the landing climb requirement of FAR 25.119 and the approach climb requirement of FAR 25.121(d).

So far your replies have failed to answer the OP's question.

I would be much obliged if you can provide the approach climb limited weight and the landing climb limited weight for the non-normal gear locked-down dispatch configuration.

P.S.
For some mysterious reason the PPRuNe site refuses acces to page 2 of this thread to the Firefox browser on my PC. Someone on another thread recommended to delete all cookies, but that didn't cure the problem. Ideas welcome.
HazelNuts39 is offline  
Old 3rd May 2014, 11:30
  #25 (permalink)  
Moderator
 
Join Date: Apr 2001
Location: various places .....
Posts: 6,520
Appears to be some confusion in this thread.

First, I have no specific 777 knowledge so can only talk generics .. however, the thread subject will only differ between Types by virtue of weights in the AFM .. the rules are the same

Second, I would recommend heeding HN39's counsel.

The certification (design) requirements include, amongst the various WAT limits ...

(a) approach climb WAT. Addresses the missed approach starting OEI, gear up, approach flap, etc.

(b) landing climb WAT. Addresses the missed approach starting AEO, gear down, landing flap, etc.

Both of these limits must be observed (ie whichever might be the more restrictive is critical). Note that the required gradients are not the same. As to why the OP's weights differ would require access to the source documentation ...

Looking through the thread, the pertinent concerns appear to be ..

(a) Dispatch performance and Inflight performance usually have different factors

Think, perhaps, in terms that despatch requires full adherence to whatever the rules might be. Inflight we are looking at abnormals and emergencies and the priority is getting the bird back safely. Same approach with MEL. 8che, I think, made a similar observation.

(b) This is to of course help dispatch and fly with the gear locked down for technical reasons etc.

Pertinent MEL point. If you are INTENDING to commence a flight you must observe all the usual rules ergo, if the gear is down, you will need weight penalties to meet those requirements normally related to gear up.

(c) but the landing climb limit weight is also calculated with gear down

.. however, the approach climb is gear up. Therefore, for an INTENTIONAL despatch, the operator will need to meet the OEI approach climb requirement with gear DOWN.

(d) Gear down performance means gear cannot be retracted

Suggest no .. the landing climb requirement is to ensure that the missed approach can be initiated in the landing configuration until such time as the aircraft can be reconfigured to the (approach climb) normal missed approach configuration. I presume the 777 missed approach procedure from late final is something like .. thrust up, pitch up, flap approach, positive climb, gear up ... like other aircraft ? Thus, if you can't retract, you need to achieve appropriate gear up performance with gear down.

(e) a landing climb assumes you retract the gear while going around..

Common pilot misunderstanding .. the certification rules and the routine operating rules don't always see eye to eye .. similar case is stall recovery protocols.

(f) Approach climb is not an issue here

.. but it is .. the operation must meet both limits to provide for the OEI case.

(g) why don't they just say that in the landing gear non-normal procedure?

There's no real need to do so .. the weight is the lower of approach climb and landing climb ..

(h) because only the landing climb weight is used when performing the overweight landing cx list

That would make no sense at all as it ONLY addresses the AEO case.

(i) inferring that on this aircraft landing climb weight limit is always a greater consideration than approach climb limit.

That may be true .. would take an AFM to research.
john_tullamarine is offline  
Old 3rd May 2014, 12:35
  #26 (permalink)  
 
Join Date: Apr 2010
Location: Home soon
Posts: 1,969
The approach/climb limit weight in perf dispatch is the most restrictive of the two.
If the required go around gradient is above 2.1%,the go around climb gradient must be checked in EASA land.config is flaps 15 on engine TOGA,gear up.
de facto is offline  
Old 3rd May 2014, 18:49
  #27 (permalink)  
Thread Starter
 
Join Date: Nov 2009
Location: PK
Posts: 187
The term "Landing Climb Limit Weight" is a misnomer. The correct term would be "Maximum Landing Weight Limited by Climb Requirements", or in short "climb-limited landing weight".
Thanks Hazel This was definitely causing some confusion here as we were so obsessed with the term "Landing Climb" thinking that "Approach Climb Limit Weight" will be given in another table/section.

Boeing's FCOM just presents one table with the name "Landing Climb Limit Weight" which covers both Landing Climb and Approach Climb.

Secondly, the weight difference is not because of dispatch or in-flight performance methods. It is due to gear remaining permanently extended in one condition and temporarily extended in the other.

I would recommend heeding HN39's counsel
Thanks JT

Less and less info seems to be making its way into the FCOMs these days
Yes OK465, the "Text" section explains just the method of determining the value from the table in two lines. Nothing about the table itself.
Haroon is offline  
Old 4th May 2014, 09:22
  #28 (permalink)  
Moderator
 
Join Date: Apr 2001
Location: various places .....
Posts: 6,520
This lower dispatch weight presented by the OP is NOT technically the 'approach climb limit weight'

Can't comment on 777 specific weights as I have no data to hand upon which to base any comment. However, the point is that BOTH limits have to be satisfied for any planned operation. Whichever happens to be more limiting becomes the limiting weight on the specific occasion. I wouldn't sweat too much on the terminology .. the AFM gives the WAT limit and the pilot is obliged not to operate above it. Different strategies may apply if a technical problem occurs mid flight.

The presented weight evidently includes an additional penalty for the gear drag over and above the 'approach climb limit weight' as defined in the regs

Again, I don't have the AFM so I can't talk numbers.

However, IF we are talking about despatch with a gear problem (ie MEL exercise) then the approach climb has to be met for OEI, gear down so one would expect a significantly reduced limit. This has naught to do with the landing limit case (AEO, gear down) but BOTH have to be considered and the more limiting is the one which rules.

So the limit is non-normal specific

Absolutely . .but, if we are talking despatch per MEL then we are doing the approach climb thing with gear DOWN rather than UP.

Less and less info seems to be making its way into the FCOMs these days

ah .. that started in the olden days when the bean counters and legal eagles started to outnumber the operational folks at board level.

You land overweight because you have to, possibly even short of your intended destination (where all the dispatch fuel figures actually apply)....regardless of the number of operative engines

Only if you don't have an alternative option .. eg holding. The point is .. it is silly just to consider AEO for inflight replanning and, for despatch you must consider both (or, rather, the MEL should be doing that for you either explicitly or by directed instruction). Not all that different to having an abnormal/emergency diversion .. one doesn't use an inadequate length runway if there is a reasonable, acceptable length alternative.

we were so obsessed with the term "Landing Climb" thinking that "Approach Climb Limit Weight" will be given in another table/section.

Think WAT limit and perhaps that will make it easier to follow for the logic ?

Boeing's FCOM just presents one table with the name "Landing Climb Limit Weight" which covers both Landing Climb and Approach Climb.

Which is all that is required. Whether the climb limit is the approach or the landing WAT case doesn't really matter .. you MUST comply with both other than in an emergency situation.
john_tullamarine is offline  
Old 4th May 2014, 10:11
  #29 (permalink)  
 
Join Date: Jul 2009
Location: France - mostly
Age: 80
Posts: 1,689
Still confused?

Just to clarify in case there is still some confusion:

(1) When dispatching a two-engined transport airplane for a flight with the landing gear locked down -

The takeoff weight may not exceed the weight at which the airplane achieves the 2nd-segment OEI climb gradient of 2.4 % with the gear down.

The landing weight may not exceed the weight at which the airplane achieves the OEI approach climb gradient of 2.1 % with the gear down.

Similar considerations apply for other safety-related performance aspects, such as takeoff distance, final segment climb requirement, obstacle clearance, landing distance, etc.

(2) The title "Landing Climb Limit Weight" should be read as:
LANDING: "Climb-limited weight"
Not as: "Landing climb" Limit Weight

(3) As said before, the climb-limited landing weight is the weight that complies with the OEI approach climb and the AEO landing climb gradient reqirements. The approach climb flap setting is related to the landing flap setting because the stall speed may not exceed 110% of the stall speed in the related landing configuration.

When the landing weight exceeds the climb-limited landing weight in the normal landing configuration, an alternative set of reduced landing and approach flap settings must be used. Again, the the stall speed in the alternative approach-climb configuration may not exceed 110% of the stall speed in the alternative landing configuration. The option to schedule the reduced flap settings exists at dispatch as well as in-flight. The available length of runway must accommodate the increase of required landing distance at the reduced flapsetting.

Last edited by HazelNuts39; 4th May 2014 at 10:41.
HazelNuts39 is offline  
Old 4th May 2014, 16:19
  #30 (permalink)  
 
Join Date: Jul 2009
Location: France - mostly
Age: 80
Posts: 1,689
Hi OK465,

The point I was trying to make is that the landing configuration and the approach climb configuration are a 'pair' linked by the stall speeds. But you are correct, there is indeed a 'waiver'. FAA AC 25-7C "Flight Test Guide" describes it as follows:

Section 25.121(d) requires that the reference stall speed for the approach configuration not exceed 110 percent of the reference stall speed for the related landing configuration. This stall speed ratio requirement is to ensure that an adequate margin above the stall speed in the selected approach configuration is maintained during flap retraction in a go-around. An alternative means of providing an adequate operating speed margin during flap retraction in a go-around would be to increase VREF for the landing configuration to provide an equivalent operating speed margin. That is, VREF could be increased such that the reference stall speed for the approach configuration does not exceed 110 percent of VREF/1.23. An equivalent level of safety finding should be used to document the use of this alternative versus direct compliance with 25.121(d). To maintain equivalent safety, the increase in VREF should not be excessive (for example, greater than 5 knots) to minimize the effect on safety of longer landing distances, higher brake energy demands, and reduced margins between VREF and VFE.

Last edited by HazelNuts39; 4th May 2014 at 16:26. Reason: Formating problem in the quote
HazelNuts39 is offline  
Old 4th May 2014, 17:20
  #31 (permalink)  
Thread Starter
 
Join Date: Nov 2009
Location: PK
Posts: 187
I suspect the Flaps 1 stall speed is more than 110% of the Flaps 15 stall speed. When you compare the maneuvering speeds at a nominal landing weight, i.e. ~150ish for Flaps 15 and ~180ish for Flaps 1, you're looking at about 120%.
Some aircraft just have slats extended on Flaps 1 setting and no flaps, not sure if this can be the reason.
Haroon is offline  
Old 4th May 2014, 18:45
  #32 (permalink)  
 
Join Date: Jul 2009
Location: France - mostly
Age: 80
Posts: 1,689
OK465,

The stall speed ratio applies to the configuration used for compliance with the approach climb minimum gradient requirement. The AFM or equivalent should state the approach climb flap settings used for determining the climb-limited landing weights in the normal and alternative landing configurations, respectively.

I also vaguely remember a provision (but cannot find it now) that the flap select lever should not pass through a 'gated' position when going from the landing setting to the related approach climb position.
HazelNuts39 is offline  
Old 4th May 2014, 20:08
  #33 (permalink)  
 
Join Date: May 2001
Location: A few degrees South
Posts: 813
The gated positions 1 and 15 are the go-around positions, for single engine and normal operations.
The go around procedure and speeds depend on this positions, so hence there is a reason not to bypass them and fly with a lower flap setting.
latetonite is offline  
Old 5th May 2014, 03:55
  #34 (permalink)  
 
Join Date: May 2001
Location: A few degrees South
Posts: 813
Not that I am aware of.
latetonite is offline  
Old 8th May 2014, 19:09
  #35 (permalink)  
 
Join Date: Jun 2011
Location: france
Posts: 756
Very. Interesting thread showing how returning to "Basics" is useful:

Being allowed to ask wrong questions,
Asking the good questions,
Coming back to exact definitions,
Keeping it simple but without missing the global overview,
Writing books with words and plain language,
Reading books in manner to understand operations,
Being motivated to our professions and enjoy doing them well,
FE are still missing, math, FBW. and SOPs are not enough,
Finding a friendly community of Gentlemen with diverse skills.
What did I miss ?
roulishollandais is offline  
Old 8th May 2014, 20:56
  #36 (permalink)  
Moderator
 
Join Date: Apr 2001
Location: various places .....
Posts: 6,520
I think it reasonable to opine that none of us knows all the answers ie we are all learning until we depart controlled life. If nothing else be achieved, emphasising that educational value is the principal aim of this Forum.

I have no knowledge of HN39's being banned along the way so can't comment ... but certainly suggest that his engineering background makes his counsel well worth heeding.
john_tullamarine is offline  
Old 11th May 2014, 16:40
  #37 (permalink)  
 
Join Date: Jun 2011
Location: france
Posts: 756
Devil

Originally Posted by John Tullamarine
I have no knowledge of HN39's Being banned along the way so can not comment ... Certainly goal Suggest That His engineering background Makes His counsel well worth heeding
We must wonder at such primitive practices ostracizing by a computer governement in an irresponsible and playful world where IT has developed since the advent of personal computers around 1980.
Thus Hazelnuts39,Engineer highly appreciated by all suffered gross injustice and humiliation. Instead aviation paid blood money to defend the homeland, freedom and honor.
Other such situations like massive delete of posts from our best members - PJ2, Machinbird, le- happened.

The arrival of the systems introduced in the same way into the aircraft design some inacceptable schyzophreny, theory of 'the' game facing volounteer air safety.

We know John, that it is not you who should do that.
roulishollandais is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.