why not stabalise engines with brakes on?
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Hello Again,
I guess that we are going to win the award for going totally off topic
Legally we don’t have to account for line-up distances (FARS) and until recently we didn’t have the ability to do so. We did however shorten numerous runways where the crew knew that they couldn’t taxi on and line up at the start of the tarmac. But generally speaking on most runways, it didn’t happen, the distance used in line up was lost. I’m not saying that this is right, but there again neither is pretending that it doesn’t snow! (no contaminated runway regulations in the FAR’s)
You believe that the basis of takeoff calculations is flawed. They have slightly changed over the years with the introduction of VEF 1 second before V1, accounting for the aircraft acceleration during the reaction time and even accounting for worn brakes. If you still don’t agree that this is sufficient, what else would you introduce?
As for our policies on reduced thrust, as 411A has pointed out, these procedures were introduced when I was still a kid. At that time this company was under the control of TWA and basically followed all of their procedures. I don’t believe that they are that different from other operators, so lets start a quick survey. Does your airline use reduced thrust, if so what are the limitations?
John, to quickly answer your questions.
Airbus procedures, which also applies to some Boeing operators, use an optimized V-speed ratio for ALL takeoffs. This means that you are using improved climb in all cases and not just when it’s required. This in turn allows you to have a greater takeoff weight OR an even greater thrust reduction.
You believe that we shouldn’t set a Derate thrust below climb thrust. We don’t, but we do however use Derated climb thrust, but let’s not go into that
As for the 1000 feet pad, why 1000 feet, why not 1500? In other words, where do we draw the line?
Then there is the comment about not flying with us! Don’t worry about it; most of the employees only do it because it’s free!
I totally agree with you that Ops Engs should have flying experience, now if only I could convince our management that I should add a B777 type rating to my ATP.
Night all.
Mutt
[This message has been edited by mutt (edited 29 May 2001).]
I guess that we are going to win the award for going totally off topic
Legally we don’t have to account for line-up distances (FARS) and until recently we didn’t have the ability to do so. We did however shorten numerous runways where the crew knew that they couldn’t taxi on and line up at the start of the tarmac. But generally speaking on most runways, it didn’t happen, the distance used in line up was lost. I’m not saying that this is right, but there again neither is pretending that it doesn’t snow! (no contaminated runway regulations in the FAR’s)
You believe that the basis of takeoff calculations is flawed. They have slightly changed over the years with the introduction of VEF 1 second before V1, accounting for the aircraft acceleration during the reaction time and even accounting for worn brakes. If you still don’t agree that this is sufficient, what else would you introduce?
As for our policies on reduced thrust, as 411A has pointed out, these procedures were introduced when I was still a kid. At that time this company was under the control of TWA and basically followed all of their procedures. I don’t believe that they are that different from other operators, so lets start a quick survey. Does your airline use reduced thrust, if so what are the limitations?
John, to quickly answer your questions.
Airbus procedures, which also applies to some Boeing operators, use an optimized V-speed ratio for ALL takeoffs. This means that you are using improved climb in all cases and not just when it’s required. This in turn allows you to have a greater takeoff weight OR an even greater thrust reduction.
You believe that we shouldn’t set a Derate thrust below climb thrust. We don’t, but we do however use Derated climb thrust, but let’s not go into that
As for the 1000 feet pad, why 1000 feet, why not 1500? In other words, where do we draw the line?
Then there is the comment about not flying with us! Don’t worry about it; most of the employees only do it because it’s free!
I totally agree with you that Ops Engs should have flying experience, now if only I could convince our management that I should add a B777 type rating to my ATP.
Night all.
Mutt
[This message has been edited by mutt (edited 29 May 2001).]
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Mutt,
A few more thoughts and comments on your thoughts ...
(a) "Legally we don’t have to account for line-up distances (FARs) and until recently we didn’t have the ability to do so."
I suggest that prudent corporate governance includes a requirement for the consideration both of
(i) what the FAA might or might not do in respect of AOCs and penalty actions, as well as
(ii) the potential for strict liability after a mishap, Conventions notwithstanding.
How can you suggest that you didn't have the ability to do so ? Australia, for many years now, has adopted a fairly pragmatic approach by doing some simple taxy/lineup tests with reasonable wheel/soft bits clearance margins. I have copies of the original correspondence between the initial operator and the regulatory authority in my patch and it makes for very sensible reading. Even if one didn't go to that extent, it is a very simple exercise to use a CAD add-on to simulate the same thing. Either way, sensible lineup allowances very easily can be derived. You don't need any legal coercion to do so - so long as your procedure is conservative with regard to Parts 25/121, then the System probably isn't going to be too concerned one way or another. But your pilots will be - and we really are only concerned about the accel stop accountability.
(b) "...(no contaminated runway regulations in the FAR’s)"
I don't work for any FAA-approved operators but .... are we confusing airworthiness with operational rules ? The main reason for a dearth of prescriptive rules for contaminant operations lies in the variability of the animal and the practical difficulties associated with making sensible and repeatable measurements for calculation purposes. An operator cannot just ignore the problem - operational requirements impose a responsibility to make some, albeit imperfect, attempt to maintain a reasonable level of operational safety. We all know that some operators chose to ignore some things, but that is beside the point.
.... and, always, one has to keep in mind ... what is your story going to be at the inquiry ?
(c) "You believe that the basis of takeoff calculations is flawed."
This misses the whole point that the AFM is about reference data, not guarantees. It is up to the operator to determine a reasonable balance between operational prudence (ie conservative application of the AFM data) and commercial drive (ie profit). The reality of level playing fields and the like is noted - but - you pays your money and you takes your chances. Leaning too far to the short term profit goal occasionally proves to be expensive after the event.
(d) "Airbus procedures.... use an optimized V-speed ratio for ALL takeoffs."
Thanks for the info. This equates to what we have all been doing all the way along - unbalance the field length (where the data is available) and use V2 overspeed, as appropriate, to maximise the RTOW for each takeoff scheduled. A matter of semantics ...
(e) "..Derate thrust below climb thrust."
In the event of climb derate the same philosophy ought to apply. That is, we don't really want to takeoff and then push the throttles up to go climbing ...
(f) "As for the 1000 feet pad....... where do we draw the line?"
What's a good pad ? Whatever you (corporately, and industrially) consider to be appropriate (for a host of reasons) and able to be defended after a mishap... is exactly where you ought to draw the line.... and, this discussion, naturally could be the subject of a very interesting thread ...
The engineer, to whom my tale related, was very clear in his attitude - 1000 feet was around about the minimum pad which he reckoned he needed to be able to sell this newfangled reduced thrust procedure to his flightcrews - pure and simple.
(g) ".. Ops Engs should have flying experience".
I empathise with you. I had the experience, a long time ago, of putting that sort of proposal to my then boss, who endorsed it wholeheartedly. His boss, in town, who had to make the decision (read "spend money"), then went on leave. You guessed it, my boss then sat in his boss' chair, assessed his own recommendation .. and then knocked it back.
However, such experience needs to be relevant. In my case, a colleague and I, in similar jobs, had bare commercial licences and we, well-armed with the full ignorance of excessive youth, knew that we knew everything. The heavy aircraft ops engineer needs to have a reasonable amount of line experience for the flying thinking to be of much relevance. Thinking back to my earlier career, I can recall a couple of very wise airline performance engineering managers who went down a somewhat different pathway to overcome the practical difficulties associated with the ops engineer not quite understanding what the real world of line operations is all about. They actively courted flight operations management, established open dialogue, and a reasonable outcome resulted. I still believe that their approach produced some very very practical escape procedures, for example.
[This message has been edited by john_tullamarine (edited 30 May 2001).]
A few more thoughts and comments on your thoughts ...
(a) "Legally we don’t have to account for line-up distances (FARs) and until recently we didn’t have the ability to do so."
I suggest that prudent corporate governance includes a requirement for the consideration both of
(i) what the FAA might or might not do in respect of AOCs and penalty actions, as well as
(ii) the potential for strict liability after a mishap, Conventions notwithstanding.
How can you suggest that you didn't have the ability to do so ? Australia, for many years now, has adopted a fairly pragmatic approach by doing some simple taxy/lineup tests with reasonable wheel/soft bits clearance margins. I have copies of the original correspondence between the initial operator and the regulatory authority in my patch and it makes for very sensible reading. Even if one didn't go to that extent, it is a very simple exercise to use a CAD add-on to simulate the same thing. Either way, sensible lineup allowances very easily can be derived. You don't need any legal coercion to do so - so long as your procedure is conservative with regard to Parts 25/121, then the System probably isn't going to be too concerned one way or another. But your pilots will be - and we really are only concerned about the accel stop accountability.
(b) "...(no contaminated runway regulations in the FAR’s)"
I don't work for any FAA-approved operators but .... are we confusing airworthiness with operational rules ? The main reason for a dearth of prescriptive rules for contaminant operations lies in the variability of the animal and the practical difficulties associated with making sensible and repeatable measurements for calculation purposes. An operator cannot just ignore the problem - operational requirements impose a responsibility to make some, albeit imperfect, attempt to maintain a reasonable level of operational safety. We all know that some operators chose to ignore some things, but that is beside the point.
.... and, always, one has to keep in mind ... what is your story going to be at the inquiry ?
(c) "You believe that the basis of takeoff calculations is flawed."
This misses the whole point that the AFM is about reference data, not guarantees. It is up to the operator to determine a reasonable balance between operational prudence (ie conservative application of the AFM data) and commercial drive (ie profit). The reality of level playing fields and the like is noted - but - you pays your money and you takes your chances. Leaning too far to the short term profit goal occasionally proves to be expensive after the event.
(d) "Airbus procedures.... use an optimized V-speed ratio for ALL takeoffs."
Thanks for the info. This equates to what we have all been doing all the way along - unbalance the field length (where the data is available) and use V2 overspeed, as appropriate, to maximise the RTOW for each takeoff scheduled. A matter of semantics ...
(e) "..Derate thrust below climb thrust."
In the event of climb derate the same philosophy ought to apply. That is, we don't really want to takeoff and then push the throttles up to go climbing ...
(f) "As for the 1000 feet pad....... where do we draw the line?"
What's a good pad ? Whatever you (corporately, and industrially) consider to be appropriate (for a host of reasons) and able to be defended after a mishap... is exactly where you ought to draw the line.... and, this discussion, naturally could be the subject of a very interesting thread ...
The engineer, to whom my tale related, was very clear in his attitude - 1000 feet was around about the minimum pad which he reckoned he needed to be able to sell this newfangled reduced thrust procedure to his flightcrews - pure and simple.
(g) ".. Ops Engs should have flying experience".
I empathise with you. I had the experience, a long time ago, of putting that sort of proposal to my then boss, who endorsed it wholeheartedly. His boss, in town, who had to make the decision (read "spend money"), then went on leave. You guessed it, my boss then sat in his boss' chair, assessed his own recommendation .. and then knocked it back.
However, such experience needs to be relevant. In my case, a colleague and I, in similar jobs, had bare commercial licences and we, well-armed with the full ignorance of excessive youth, knew that we knew everything. The heavy aircraft ops engineer needs to have a reasonable amount of line experience for the flying thinking to be of much relevance. Thinking back to my earlier career, I can recall a couple of very wise airline performance engineering managers who went down a somewhat different pathway to overcome the practical difficulties associated with the ops engineer not quite understanding what the real world of line operations is all about. They actively courted flight operations management, established open dialogue, and a reasonable outcome resulted. I still believe that their approach produced some very very practical escape procedures, for example.
[This message has been edited by john_tullamarine (edited 30 May 2001).]
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Morning Chaps
Here's one line pilot who's not surprised or shocked at Mutt's post.Our company and many others in the UK use Max derate all the time unless there's a sensible reason for not doing so.(eg Field limited at Funchal perhaps )
From memory Handling the Big Jets reckons there's one percent margin for every three degrees the assumed temperature is higher than the actual temperature.(Looked it up just to check).
Many times in the 757/767 the allowable reduced thrust temperature is less than you can wind into the derate anyway.Less powerful a/c are closer to the real limit more often.
Lots of factors to consider and at the end of the day its airmanship again.
Here's one line pilot who's not surprised or shocked at Mutt's post.Our company and many others in the UK use Max derate all the time unless there's a sensible reason for not doing so.(eg Field limited at Funchal perhaps
)From memory Handling the Big Jets reckons there's one percent margin for every three degrees the assumed temperature is higher than the actual temperature.(Looked it up just to check).
Many times in the 757/767 the allowable reduced thrust temperature is less than you can wind into the derate anyway.Less powerful a/c are closer to the real limit more often.
Lots of factors to consider and at the end of the day its airmanship again.
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JT, thanks for the responses, very enlightening stuff.
(A) Aviation is a wonderful world of trade-offs, we didn’t account for line-up distances unless there is a known problem, but to balance this, we don’t use stopways to increase the takeoff weight. Getting a realistic line up distance when you operate 11 different jet aircraft types is pretty interesting, what works for some will not work for others.
(B) Contaminated runways, lets not go there. That needs a topic all to itself. I shouldn’t have used it as an example.
(D) Using optimized V-speeds not only increases your V2, they also increases your V1, therefore you are once again making the takeoff field length limited when it need not be.
(G)What’s the old saying "a little knowledge is dangerous"? I do not have the relevant line experience to consider my licence as a benefit. That’s why I have to come in here and rack the brains of those with the experience.
Your views on litigation are extremely interesting, and I hope that we can continue to discuss them at a later stage, but at this time I have to go. Vacation is calling.
Finally, what is everyone else doing? Give us your comments? Especially those of you who are using ACARS for takeoff performance or any cockpit laptop computer.
Mutts..
[This message has been edited by mutt (edited 30 May 2001).]
Further edited here at the Towers to get the image to work - thirsty job......
[This message has been edited by PPRuNe Towers (edited 30 May 2001).]
(A) Aviation is a wonderful world of trade-offs, we didn’t account for line-up distances unless there is a known problem, but to balance this, we don’t use stopways to increase the takeoff weight. Getting a realistic line up distance when you operate 11 different jet aircraft types is pretty interesting, what works for some will not work for others.
(B) Contaminated runways, lets not go there. That needs a topic all to itself. I shouldn’t have used it as an example.
(D) Using optimized V-speeds not only increases your V2, they also increases your V1, therefore you are once again making the takeoff field length limited when it need not be.
(G)What’s the old saying "a little knowledge is dangerous"? I do not have the relevant line experience to consider my licence as a benefit. That’s why I have to come in here and rack the brains of those with the experience.
Your views on litigation are extremely interesting, and I hope that we can continue to discuss them at a later stage, but at this time I have to go. Vacation is calling.
Finally, what is everyone else doing? Give us your comments? Especially those of you who are using ACARS for takeoff performance or any cockpit laptop computer.
Mutts..
[This message has been edited by mutt (edited 30 May 2001).]
Further edited here at the Towers to get the image to work - thirsty job......
[This message has been edited by PPRuNe Towers (edited 30 May 2001).]
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Hi Mutt,
Busy couple of days on the keyboard huh?? Enjoy the leave mate.
For UK operations I can't offhand think of anyone who doesn't derate as far as possible unless prevented by individual runway, weight (really must remember to say mass....), obstacle, MEL or contamination problems.
Crews understand the reasons for it and take it seriously. Most outfits use tables to completely fine tune the power setting chosen rather than just taking fixed stages of derate.
As yet no-one is using laptop devices for calculations in the UK a la Southwest or Fedex but the CAA are keen to see it come about. It's one of the main projects I've beeen working on for the past year. The technical issues are zero but data, its processing and it's validation to UK and JAR standards rather than FAA has been problematic, especially regarding your favourite topic of contamination (Mutt has been trying for 18 months that I know of to get some decent guidance on slush/snow/ice) Luckily, colleagues at Braathens have led the way and very kindly allowed me to hang on to their coat-tails while they do it - including the writing of acceptable contaminated performance software.
Meanwhile, the tabular formats are the system generally in use and familiar to most of us. They vary in terms of how far they go up in assumed temperatures. Some operators go as high as the top end you mention while others stop at the aircraft ambient temp. limit. Where I work they only go up to 48 degrees. An entirely arbitrary but pragmatic limit to fit comfortably on the page and be transmitted usably by the lowest common denominator downroute - fax
General rule for UK ops is a fixed maximum derate of any given engine type. The derate chosen on the day can never be less than this or the climb power selected. This includes derated climb settings.
Just to keep it crystal clear: I derate at every possible opportunity. I take the time to talk to the engineers regarding their trend monitoring work (full QAR fit) and have a great deal of faith in their efforts and experience.
However, it was seeing examples of performance calculations using every inch of runway soley for maximum derating and no other reason that prompted me to write. There is very clear evidence of the benefits when derating operational engines - it's not theory. In my experience though, powerplant experts seem to shuffle and shrug a lot when discussing the availability of data supporting the advantages of really deep derating.
I'd honestly suggest you consider talking this over with a QA person. Risk analysis is something they can give you guidelines on. Changes in performance rules are glacial but change they do - regretably the final push is usually induced by serious accidents.
The one second Vef rule you mention is entirely due to this. Also, the part worn brakes item was fought for over many years but only came about after the total loss of a wide body aircraft. I know it must seem like ancient history to you but all performance calculations for the first 20+ years of jet transports were based on new brakes, tyres and a scrubbed runway. It seems laughable and illogical now but I promise that what you're working with today will seem just as daft and dangerous when you look back in a few years - holding a pint and your active ATPL.....
Yes, a pad is entirely arbitrary but, as John T so lucidly points out, in a litigious world even the most elementary models of risk analysis will point to the inclusion of a buffer, whether fixed or percentage based, rather than a few degrees more aggressive derate.
I think this exchange of views across disciplines is incredibly valuable - makes the aggro associated with running this place seem worthwhile. My sincere thanks to all the tech log regulars.
Regards from the Towers
Rob Lloyd
[email protected]
Busy couple of days on the keyboard huh?? Enjoy the leave mate.
For UK operations I can't offhand think of anyone who doesn't derate as far as possible unless prevented by individual runway, weight (really must remember to say mass....), obstacle, MEL or contamination problems.
Crews understand the reasons for it and take it seriously. Most outfits use tables to completely fine tune the power setting chosen rather than just taking fixed stages of derate.
As yet no-one is using laptop devices for calculations in the UK a la Southwest or Fedex but the CAA are keen to see it come about. It's one of the main projects I've beeen working on for the past year. The technical issues are zero but data, its processing and it's validation to UK and JAR standards rather than FAA has been problematic, especially regarding your favourite topic of contamination
(Mutt has been trying for 18 months that I know of to get some decent guidance on slush/snow/ice) Luckily, colleagues at Braathens have led the way and very kindly allowed me to hang on to their coat-tails while they do it - including the writing of acceptable contaminated performance software.Meanwhile, the tabular formats are the system generally in use and familiar to most of us. They vary in terms of how far they go up in assumed temperatures. Some operators go as high as the top end you mention while others stop at the aircraft ambient temp. limit. Where I work they only go up to 48 degrees. An entirely arbitrary but pragmatic limit to fit comfortably on the page and be transmitted usably by the lowest common denominator downroute - fax
General rule for UK ops is a fixed maximum derate of any given engine type. The derate chosen on the day can never be less than this or the climb power selected. This includes derated climb settings.
Just to keep it crystal clear: I derate at every possible opportunity. I take the time to talk to the engineers regarding their trend monitoring work (full QAR fit) and have a great deal of faith in their efforts and experience.
However, it was seeing examples of performance calculations using every inch of runway soley for maximum derating and no other reason that prompted me to write. There is very clear evidence of the benefits when derating operational engines - it's not theory. In my experience though, powerplant experts seem to shuffle and shrug a lot when discussing the availability of data supporting the advantages of really deep derating.
I'd honestly suggest you consider talking this over with a QA person. Risk analysis is something they can give you guidelines on. Changes in performance rules are glacial but change they do - regretably the final push is usually induced by serious accidents.
The one second Vef rule you mention is entirely due to this. Also, the part worn brakes item was fought for over many years but only came about after the total loss of a wide body aircraft. I know it must seem like ancient history to you but all performance calculations for the first 20+ years of jet transports were based on new brakes, tyres and a scrubbed runway. It seems laughable and illogical now but I promise that what you're working with today will seem just as daft and dangerous when you look back in a few years - holding a pint and your active ATPL.....
Yes, a pad is entirely arbitrary but, as John T so lucidly points out, in a litigious world even the most elementary models of risk analysis will point to the inclusion of a buffer, whether fixed or percentage based, rather than a few degrees more aggressive derate.
I think this exchange of views across disciplines is incredibly valuable - makes the aggro associated with running this place seem worthwhile. My sincere thanks to all the tech log regulars.
Regards from the Towers
Rob Lloyd
[email protected]
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Mutt,
I was really pleased to see your comment about racking the brains of others and learning - not that I think that you are behind the eight ball, but for the comment's general applicability.
For that is what this professional game is, or should be, all about. We all start off full bottle, brimming over with the impetuous stupidity of youth, frighten ourselves witless from time to time ... and then, hopefully, we become somewhat humbled and contrite, eager to learn as opposed to just grandstanding and point scoring.
This is a great forum, as there exists within a melting pot of conflicting views and philosophies.
And please don't think that anyone has a monopoly on knowledge - we all can learn a great deal by listening to the accumulated wisdom of others whose experience differs from our own. For myself, my notebook jottings increase as I peruse the posts herein. Like I said - meaty stuff.
Do have a great holiday and we look forward to further jousting upon your return ....
I was really pleased to see your comment about racking the brains of others and learning - not that I think that you are behind the eight ball, but for the comment's general applicability.
For that is what this professional game is, or should be, all about. We all start off full bottle, brimming over with the impetuous stupidity of youth, frighten ourselves witless from time to time ... and then, hopefully, we become somewhat humbled and contrite, eager to learn as opposed to just grandstanding and point scoring.
This is a great forum, as there exists within a melting pot of conflicting views and philosophies.
And please don't think that anyone has a monopoly on knowledge - we all can learn a great deal by listening to the accumulated wisdom of others whose experience differs from our own. For myself, my notebook jottings increase as I peruse the posts herein. Like I said - meaty stuff.
Do have a great holiday and we look forward to further jousting upon your return ....
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Hi PPRuNe Towers
Er...um...please sir...(puts hand up)...do we count sir?
Haven't done a derated take off in years!
We may get there. We have company issue palmtops with, amongst other programs, all our T/O Data loaded in. They work very well, and are extremely useful, but currently (!) are only approved for use as a cross check, after all manual calculations have been completed.
The primary T/O data source is still the T/O performance manual.
The load sheet and trim program is approved for use (though we are still required to produce printed or written copies) and is a godsend!
Regards
Bellerophon
<font face="Verdana, Arial, Helvetica" size="2">For UK operations I can't offhand think of anyone who doesn't derate as far as possible</font>
Haven't done a derated take off in years!
<font face="Verdana, Arial, Helvetica" size="2">As yet no-one is using laptop devices for calculations in the UK</font>
The primary T/O data source is still the T/O performance manual.
The load sheet and trim program is approved for use (though we are still required to produce printed or written copies) and is a godsend!
Regards
Bellerophon
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I drive a Falcon 2000, which has FADEC. No provision for derated TOs. It's quite nice never seeing the departure end of the runway before rotation.
But.
If Boeing and my employer (notwithstanding the compromised nature of every rulemaking enterprise) tell me that a de-rate is OK with them, it's OK with me--provided that the assumptions and conditions match.
Seems to me that all of the risk in a de-rate TO is in the accelerate-go scenario. I presume that if an engine fails etc. you shove the levers to max (or it does so automatically) and you make your OEI climb gradient.
Have I got it wrong?
But.
If Boeing and my employer (notwithstanding the compromised nature of every rulemaking enterprise) tell me that a de-rate is OK with them, it's OK with me--provided that the assumptions and conditions match.
Seems to me that all of the risk in a de-rate TO is in the accelerate-go scenario. I presume that if an engine fails etc. you shove the levers to max (or it does so automatically) and you make your OEI climb gradient.
Have I got it wrong?
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Hi there Bellerophon,
Had a wry smile on my face as I was typing that little bit of my missive out. I kept quiet regarding your normal steed as you were performing a gentle windup elsewhere on the site regarding it - too much of a giveaway!
I steered clear of the PDA/Palmtop business at your company as I've had no recent briefing on the state of play other than the weight and balance mode. That said, the most important point I'd like to make regarding these devices is the total sea change at the UK CAA.
Six or seven months ago it became clear that an entirely new policy and attitude had come into being and was actively being communicated as far as new technology in all flight decks was concerned. Not only determined to avoid being left behind they're very actively encouraging experimentation and adoption of new and supplementary equipment on the flight deck.
bizjet pilot - not my place to speak for anyone else writing on this thread. My reasons for entering the discussing reflect my concern over the accelerate-stop case and what I perceive as flawed fundametals in the figures. Bear in mind though the differing perspectives brought to this thread - pilots seeing things differently to perf. engineers or mindsets attuned to FAA balanced field versus those of us operating with other national authorities' favoured methods.
------------------
Regards from the Towers
[email protected]
Had a wry smile on my face as I was typing that little bit of my missive out. I kept quiet regarding your normal steed as you were performing a gentle windup elsewhere on the site regarding it - too much of a giveaway!
I steered clear of the PDA/Palmtop business at your company as I've had no recent briefing on the state of play other than the weight and balance mode. That said, the most important point I'd like to make regarding these devices is the total sea change at the UK CAA.
Six or seven months ago it became clear that an entirely new policy and attitude had come into being and was actively being communicated as far as new technology in all flight decks was concerned. Not only determined to avoid being left behind they're very actively encouraging experimentation and adoption of new and supplementary equipment on the flight deck.
bizjet pilot - not my place to speak for anyone else writing on this thread. My reasons for entering the discussing reflect my concern over the accelerate-stop case and what I perceive as flawed fundametals in the figures. Bear in mind though the differing perspectives brought to this thread - pilots seeing things differently to perf. engineers or mindsets attuned to FAA balanced field versus those of us operating with other national authorities' favoured methods.
------------------
Regards from the Towers
[email protected]
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Bizjet pilot, While I agree it must be nice not seeing the departure end of a runway, it is normal for an aircraft with a MTOW of 394,625KG (B747-400). As for the risk of a derate take-off, an engine failure at V1 is designed into the formula for all take-off data. If you were to increase thrust you stand the chance of loosing directional control (some take-offs are VMCG limited).
I found a couple of interesting lines in our manuals. I stated earlier that we refrain from using 20% derate but I find that we can use the 20% derate when operating with low weight and aft CofG take-off's. Also, we have a line in the books that states the Maximum thrust reduction authorised by the FAA is 25% below any certified rating.
I found a couple of interesting lines in our manuals. I stated earlier that we refrain from using 20% derate but I find that we can use the 20% derate when operating with low weight and aft CofG take-off's. Also, we have a line in the books that states the Maximum thrust reduction authorised by the FAA is 25% below any certified rating.
In our airline we use assumed temperature derate and unbalanced field V speeds for each take-off, calculated for each runway (and each runway intersection) using individual charts prepared by our performance ops department.
bizjet pilot, pholosphies about whether or not to increase power on the operating engine folowing an engine failure vary widely. On the BAe 146 fleet my airline's philosophy was to increse thrust to rated folowing a failure, but on the 737 fleet we keep the operating engine at the derated thrust.
The thrust derate process allows for all performance after an engine failure, including the single engine climb, so it isn't necessary to increase the thrust (with the increased flying complications involved in the increased yaw). If you do increase the thrust, though you get a performance buffer - six of one half dozen of the other perhaps?
bizjet pilot, pholosphies about whether or not to increase power on the operating engine folowing an engine failure vary widely. On the BAe 146 fleet my airline's philosophy was to increse thrust to rated folowing a failure, but on the 737 fleet we keep the operating engine at the derated thrust.
The thrust derate process allows for all performance after an engine failure, including the single engine climb, so it isn't necessary to increase the thrust (with the increased flying complications involved in the increased yaw). If you do increase the thrust, though you get a performance buffer - six of one half dozen of the other perhaps?
Guest
Posts: n/a
People,
Some interesting thoughts in the last few posts - some additional observations.
(a) Never using derate ?
This would be fine on a Type for which the engine installation is heavily derated to begin with (or if all your aerodromes were nasty ones) - otherwise, a very expensive way to operate (if there be no prohibition on derate, and that would be a little unusual). Perhaps there are operators out there for whom cost is not a burden ?
In any case, I can see no immediate reason why an operator ought not to take advantage of the usual assumed temperature procedure - you get some benefits without any angst at all..... and the data is there anyway ....
I am not familiar with the Falcon 2000 - I presume, on the basis of bp's post, that the crew can't input a false, higher OAT to command the FADEC to derate on the assumed temperature style of model ?
As to the risk ? Depends on the circumstances of the takeoff and how the numbers are crunched. It is still quite easy to schedule a derate takeoff and remain accel stop limited if the runway numbers are suitable - which is what generated some wide-eyed comment following Mutt's posts on the subject.
In practical risk terms, the continued takeoff is not really a common worry due to the gross to net margin - unless the ambient is very bumpy and the obstacle profile onerous .. and, if that is the case, why would you be even considering not using all the available grunt ?
As an example, I recall many years ago, an F27 takeoff, rated wet power, turbulent ambient, nowhere near the WAT limit, and seeing the VSI pegged at around 200 FPM (AEO) for about the first 2000 feet - and, on that occasion, I did a quick altimeter vs clock check on the VSI. A bit unusual, perhaps, but emphasises the point that derate is for those occasions when everything is going for you - the real danger here, as in any area of line operation, is the uncritical and unthinking use of a procedure - sometimes the captain has to earn his money and make a decision contrary to a normally recommended or accepted practice. Every now and again not doing so gets people into more strife than Speed Gordon.
(b) Increasing thrust in the OEI case ?
The basis of certification is that the power/thrust is set and left. While this doesn't prevent or preclude the crew's pushing the remaining throttles up for whatever reason, manual adjustment is not permitted to be scheduled for certification purposes. It is for this reason that some installations incorporate auto power reserve (by whatever name), which does the same thing without pilot intervention, and may permit an increased RTOW to be scheduled, depending on the circumstances.
The suggestion that increasing thrust in the OEI case would compromise Vmcg considerations in the case of a min V1 scheduled takeoff probably is not a major concern. While there are some provisions for scheduling thrust level versus control variations, I would not imagine that a manufacturer has considered scheduling such variation just to accommodate lower min V1 speeds, unless this is done incidentally as part of a fixed derate recertification program in which the Vmcg is revisited. Cpdude's comment re the 20 percent derate for low RTOW/aft cg takeoffs on the big bird well may involve such a consideration. It follows that, in such a case, inappropriate throttle movement within an unfortunate speed band and at an inappropriate rate, could present a problem.
Now there is one other proviso to this line of argument and, unfortunately, the example I would love to give would be too easily recognisable in some circles, regardless of sanitisation.
In the event that
(i) a particular aircraft's engines are pretty good, maybe considerably well above book, and
(ii) the engine is not a full throttle takeoff setting animal,
then there is a very real risk that a ham-fisted or panicking pilot might inadvertently overthrust the engines to such a degree, and at such a rate, that the published Vmcg or Vmca figures might be compromised significantly.
(c) Use of electronic gadgets to figure ops eng data ?
(i) Load calc checks ...
We are obliged to leave a Load Sheet so there must be some sort of paperwork involved. From a practical point of view, it is very much easier and quicker to do a quasi-independent crosscheck manually.
One operator with which I was involved over many years adopted a procedure where the paperwork was done by the relevant ground staff and then presented to the crew in the usual manner. We had run up some prayer wheel style trimsheets for the FO to use for checking purposes. So the captain would, in the conventional monotone drawl, call the data line by line, while the FO worked the prayer wheel to figure the final weight/cg intersection which could then be compared to the figure derived by the despatch people.
I defy anyone to do that sort of check using a laptop in anything like the few seconds that it took in the referenced operation. In addition, I have a jaundiced view of computers (in spite of having spent my life in a succession of mainframes, minis, and PCs) if they be used in a quick and dirty manner. In that sort of environment, the risk of data entry error has to be protected against, very rigorously, in the relevant prescribed procedure.
Me ? I started out a bit anti toward the prayer wheel option (which was being pushed by the chief pilot and the senior load controller) due to trimsheet accuracy/error considerations but went along with the idea. It took only a very short time for me to become a convert to the procedure.
(ii) RTOW figures ..
I have little concern with on-the-fly calculations where the procedure is a simple, straight flightpath with no surprises. However, and this is one of my hobbyhorses, the normal declared data (Type A and B, or inclino) is very limited when looking at the needs of the modern jet - with its comparatively very long third segment. The AFM calculation is the easy bit, which the computer makes even easier, far quicker, and a little more accurate.
The real problem, and where most of the work ends up going into (or ought to), is obtaining the profile data in the case of extended takeoffs and, very particularly, takeoffs which incorporate a turn. This is a major task for an operator's ops engineering personnel, or its subcontracted organisation and which, I am sad to observe, often is done very poorly, and sometimes, not at all. If the crew tries to figure a weight (in such circumstances) from a combination of the declared data and eyeballing the surrounds (which is about all the pilots can do in the field), then the laptop will give only a much more accurately calculated wrong answer than could be much more easily obtained by guesswork. Either answer would be equally suspect.
(iii) Use of computer in lieu of AFM ?
If we go back a way, AFM charts were derived laboriously by a bunch of people doing lots of sums, crossplots, and the like - can anyone remember using a sliderule (apart from the back of the nav computer) ? The end graphical or tabular result was workable, but often not very tidy - as anyone who has had to computerise AFM data from these older aircraft can attest.
With later aircraft, the performance is software modelled from the start of the project, and the fudge factors refined as the tunnel and flight test data come in. In respect of such aircraft, the paper data in the AFM is more for traditional nicety and, in some cases, doesn't even exist. If I recall correctly, the introduction in Australia a number of years ago of a fancy new narrow bodied twin jet caused some heart palpitations for just this reason - but the regulator and the operator apparently survived the experience.
[This message has been edited by john_tullamarine (edited 31 May 2001).]
[This message has been edited by john_tullamarine (edited 31 May 2001).]
[This message has been edited by john_tullamarine (edited 31 May 2001).]
Some interesting thoughts in the last few posts - some additional observations.
(a) Never using derate ?
This would be fine on a Type for which the engine installation is heavily derated to begin with (or if all your aerodromes were nasty ones) - otherwise, a very expensive way to operate (if there be no prohibition on derate, and that would be a little unusual). Perhaps there are operators out there for whom cost is not a burden ?
In any case, I can see no immediate reason why an operator ought not to take advantage of the usual assumed temperature procedure - you get some benefits without any angst at all..... and the data is there anyway ....
I am not familiar with the Falcon 2000 - I presume, on the basis of bp's post, that the crew can't input a false, higher OAT to command the FADEC to derate on the assumed temperature style of model ?
As to the risk ? Depends on the circumstances of the takeoff and how the numbers are crunched. It is still quite easy to schedule a derate takeoff and remain accel stop limited if the runway numbers are suitable - which is what generated some wide-eyed comment following Mutt's posts on the subject.
In practical risk terms, the continued takeoff is not really a common worry due to the gross to net margin - unless the ambient is very bumpy and the obstacle profile onerous .. and, if that is the case, why would you be even considering not using all the available grunt ?
As an example, I recall many years ago, an F27 takeoff, rated wet power, turbulent ambient, nowhere near the WAT limit, and seeing the VSI pegged at around 200 FPM (AEO) for about the first 2000 feet - and, on that occasion, I did a quick altimeter vs clock check on the VSI. A bit unusual, perhaps, but emphasises the point that derate is for those occasions when everything is going for you - the real danger here, as in any area of line operation, is the uncritical and unthinking use of a procedure - sometimes the captain has to earn his money and make a decision contrary to a normally recommended or accepted practice. Every now and again not doing so gets people into more strife than Speed Gordon.
(b) Increasing thrust in the OEI case ?
The basis of certification is that the power/thrust is set and left. While this doesn't prevent or preclude the crew's pushing the remaining throttles up for whatever reason, manual adjustment is not permitted to be scheduled for certification purposes. It is for this reason that some installations incorporate auto power reserve (by whatever name), which does the same thing without pilot intervention, and may permit an increased RTOW to be scheduled, depending on the circumstances.
The suggestion that increasing thrust in the OEI case would compromise Vmcg considerations in the case of a min V1 scheduled takeoff probably is not a major concern. While there are some provisions for scheduling thrust level versus control variations, I would not imagine that a manufacturer has considered scheduling such variation just to accommodate lower min V1 speeds, unless this is done incidentally as part of a fixed derate recertification program in which the Vmcg is revisited. Cpdude's comment re the 20 percent derate for low RTOW/aft cg takeoffs on the big bird well may involve such a consideration. It follows that, in such a case, inappropriate throttle movement within an unfortunate speed band and at an inappropriate rate, could present a problem.
Now there is one other proviso to this line of argument and, unfortunately, the example I would love to give would be too easily recognisable in some circles, regardless of sanitisation.
In the event that
(i) a particular aircraft's engines are pretty good, maybe considerably well above book, and
(ii) the engine is not a full throttle takeoff setting animal,
then there is a very real risk that a ham-fisted or panicking pilot might inadvertently overthrust the engines to such a degree, and at such a rate, that the published Vmcg or Vmca figures might be compromised significantly.
(c) Use of electronic gadgets to figure ops eng data ?
(i) Load calc checks ...
We are obliged to leave a Load Sheet so there must be some sort of paperwork involved. From a practical point of view, it is very much easier and quicker to do a quasi-independent crosscheck manually.
One operator with which I was involved over many years adopted a procedure where the paperwork was done by the relevant ground staff and then presented to the crew in the usual manner. We had run up some prayer wheel style trimsheets for the FO to use for checking purposes. So the captain would, in the conventional monotone drawl, call the data line by line, while the FO worked the prayer wheel to figure the final weight/cg intersection which could then be compared to the figure derived by the despatch people.
I defy anyone to do that sort of check using a laptop in anything like the few seconds that it took in the referenced operation. In addition, I have a jaundiced view of computers (in spite of having spent my life in a succession of mainframes, minis, and PCs) if they be used in a quick and dirty manner. In that sort of environment, the risk of data entry error has to be protected against, very rigorously, in the relevant prescribed procedure.
Me ? I started out a bit anti toward the prayer wheel option (which was being pushed by the chief pilot and the senior load controller) due to trimsheet accuracy/error considerations but went along with the idea. It took only a very short time for me to become a convert to the procedure.
(ii) RTOW figures ..
I have little concern with on-the-fly calculations where the procedure is a simple, straight flightpath with no surprises. However, and this is one of my hobbyhorses, the normal declared data (Type A and B, or inclino) is very limited when looking at the needs of the modern jet - with its comparatively very long third segment. The AFM calculation is the easy bit, which the computer makes even easier, far quicker, and a little more accurate.
The real problem, and where most of the work ends up going into (or ought to), is obtaining the profile data in the case of extended takeoffs and, very particularly, takeoffs which incorporate a turn. This is a major task for an operator's ops engineering personnel, or its subcontracted organisation and which, I am sad to observe, often is done very poorly, and sometimes, not at all. If the crew tries to figure a weight (in such circumstances) from a combination of the declared data and eyeballing the surrounds (which is about all the pilots can do in the field), then the laptop will give only a much more accurately calculated wrong answer than could be much more easily obtained by guesswork. Either answer would be equally suspect.
(iii) Use of computer in lieu of AFM ?
If we go back a way, AFM charts were derived laboriously by a bunch of people doing lots of sums, crossplots, and the like - can anyone remember using a sliderule (apart from the back of the nav computer) ? The end graphical or tabular result was workable, but often not very tidy - as anyone who has had to computerise AFM data from these older aircraft can attest.
With later aircraft, the performance is software modelled from the start of the project, and the fudge factors refined as the tunnel and flight test data come in. In respect of such aircraft, the paper data in the AFM is more for traditional nicety and, in some cases, doesn't even exist. If I recall correctly, the introduction in Australia a number of years ago of a fancy new narrow bodied twin jet caused some heart palpitations for just this reason - but the regulator and the operator apparently survived the experience.
[This message has been edited by john_tullamarine (edited 31 May 2001).]
[This message has been edited by john_tullamarine (edited 31 May 2001).]
[This message has been edited by john_tullamarine (edited 31 May 2001).]
Guest
Posts: n/a
Checkers,
Regarding the risks of setting rated/reference thrust in the BAe 146 folowing a failure, it may be useful to add that procedurally the increase in thrust came after the gear was up because that was about the earliest point that the PF's hand was returned after the deliberate removal at V1. The manufacturer recommended increasing the thrust to improve the performance margin, particularly in the second segment.
From memory, now rapidly failing, there was also a 6 degree "pad" included in the flex thrust figures, purely for the reasons set out by the Towers. It was removed around 96 I think.
------------------
Stay Alive,
[email protected]
Regarding the risks of setting rated/reference thrust in the BAe 146 folowing a failure, it may be useful to add that procedurally the increase in thrust came after the gear was up because that was about the earliest point that the PF's hand was returned after the deliberate removal at V1. The manufacturer recommended increasing the thrust to improve the performance margin, particularly in the second segment.
From memory, now rapidly failing, there was also a 6 degree "pad" included in the flex thrust figures, purely for the reasons set out by the Towers. It was removed around 96 I think.
------------------
Stay Alive,
[email protected]
Guest
Posts: n/a
Hello J_T
I was actually referring to producing the original load sheet, not cross checking one prepared by someone else, but either way it makes little difference. I can confidently say that on my aircraft type you won't find anyone who would agree with you. The palmtop wins hands down, both for accuracy, and especially speed, every time - obviously I wouldn't presume to speak for your aircraft type or company practices.
Why have the Captain read out the figures from the load sheet? It seems to be introducing scope for error. If they have misread a figure, chances are they may make the same mistake again when reading the figures to you. Better practice is surely to have the Captain hand over the load sheet and extract the figures yourself?
As you say data entry error is a problem, and one way of trying to minimise the problem is to have two people extract the data independently from the data source. We try to carry this philosophy further, and, for instance, hand over manuals closed, not open at the correct page - surprising how often the correct page isn't! We have learned (the hard way) that the more independent a cross check is, the more valuable it is.
Absolutely agree - wouldn't dream of it. However the ability, perhaps during taxy out say, of being able quickly to factor in a change in wind, pressure or temperature to see if you are still below RTOW is very useful. If you are not, the reverse calculations, such as “at this weight what must the tailwind or temperature drop to before we can take off?”, are very much faster and easier on a computer.
No, we never derate. It is prohibited (there are reasons) and it may be unusual, but it sure is good fun! It was just jovial banter, aimed at PPRuNe Towers who gallantly refused to say anything so as not to spoil some bait I was dangling on another forum.
Regards,
Bellerophon
<font face="Verdana, Arial, Helvetica" size="2">We are obliged to leave a Load Sheet so there must be some sort of paperwork involved. From a practical point of view, it is very much easier and quicker to do a quasi-independent crosscheck manually.</font>
Why have the Captain read out the figures from the load sheet? It seems to be introducing scope for error. If they have misread a figure, chances are they may make the same mistake again when reading the figures to you. Better practice is surely to have the Captain hand over the load sheet and extract the figures yourself?
As you say data entry error is a problem, and one way of trying to minimise the problem is to have two people extract the data independently from the data source. We try to carry this philosophy further, and, for instance, hand over manuals closed, not open at the correct page - surprising how often the correct page isn't! We have learned (the hard way) that the more independent a cross check is, the more valuable it is.
<font face="Verdana, Arial, Helvetica" size="2">If the crew tries to figure a weight..from a combination of the declared data and eyeballing the surrounds...then the laptop will give only a much more accurately calculated wrong answer</font>
<font face="Verdana, Arial, Helvetica" size="2">Never using derate ?...if there be no prohibition on derate, and that would be a little unusual</font>
Regards,
Bellerophon
Guest
Posts: n/a
Greetings, Friend of Pegasus,
(a) I was actually referring to producing the original load sheet ....
Next time I will try to read/interpret the post correctly.
(b) The palmtop wins hands down ....
So long as a given system is well tested, acceptably accurate, repeatable, and reasonably idiot proof, it matters little which approach we individually prefer. I was a bit antipathetic to the system I described until I saw it working real well in practice and became a very rapid convert.
As you infer, the aim is to do a similar task in two different ways with the reasonable expectation that the same mistake is not likely to be made twice - not strictly independent, but approximately so - if the end answer agrees, then the confidence is high.
There are many ways to achieve a quasi-independent procedure - none is perfect and, indeed, perfection is not the aim - rather an acceptably high level of accuracy, reliability and repeatability - perfect is too expensive in most cases, one way or another.
(b) However the ability ....
Fine, if the takeoff is runway limited. In the case of an obstacle limited situation, the flightdeck use of a computed solution (whether electronic or manual) will be flawed unless the obstruction data are programmed in as well in some appropriate manner - which is what I presume you have done. If the usual RTOW schedule (OAT by WV) and a suitable Hp correction is there, then the problem goes away.
(c) No, we never derate. It is prohibited (there are reasons) ...
I figured that there was an underlying discussion there. If you are willing to do so, I would very much appreciate some details on this one by email for my own benefit.
And, good fun ? .... indeed. Well do I remember takeoffs very late at night in sub-zero ambient with negligible payload in the Electra .. did someone say "rocket powered" ?
regards ....
(a) I was actually referring to producing the original load sheet ....
Next time I will try to read/interpret the post correctly.
(b) The palmtop wins hands down ....
So long as a given system is well tested, acceptably accurate, repeatable, and reasonably idiot proof, it matters little which approach we individually prefer. I was a bit antipathetic to the system I described until I saw it working real well in practice and became a very rapid convert.
As you infer, the aim is to do a similar task in two different ways with the reasonable expectation that the same mistake is not likely to be made twice - not strictly independent, but approximately so - if the end answer agrees, then the confidence is high.
There are many ways to achieve a quasi-independent procedure - none is perfect and, indeed, perfection is not the aim - rather an acceptably high level of accuracy, reliability and repeatability - perfect is too expensive in most cases, one way or another.
(b) However the ability ....
Fine, if the takeoff is runway limited. In the case of an obstacle limited situation, the flightdeck use of a computed solution (whether electronic or manual) will be flawed unless the obstruction data are programmed in as well in some appropriate manner - which is what I presume you have done. If the usual RTOW schedule (OAT by WV) and a suitable Hp correction is there, then the problem goes away.
(c) No, we never derate. It is prohibited (there are reasons) ...
I figured that there was an underlying discussion there. If you are willing to do so, I would very much appreciate some details on this one by email for my own benefit.
And, good fun ? .... indeed. Well do I remember takeoffs very late at night in sub-zero ambient with negligible payload in the Electra .. did someone say "rocket powered" ?
regards ....
Guest
Posts: n/a
Top of the Morning to ya all.......
I'm trying to work out if Balerphon flies the space shuttle or a Cessna 150?
Considering that I shocked a number of pilots, I'm surprised at how few have actually come out and told me that our procedures are any different to those in use with other airlines???
John_Tullamarine
(b) Increasing thrust in the OEI case ? (posted 31 May 2001 06:35)
Although the takeoff calculation is based on the assumed temperature without the crew having to increase the takeoff thrust, the VMCG is based on the actual temperature for the rating in use in order to allow the crew the option of increasing the thrust.
(iii) Use of computer in lieu of AFM ?
Yep, this is the way to go, the digital version of the B744 AFM allows 4,000 - 6,000 kgs increase in takeoff weight from some hot/high airports (For exactly the same conditions). Yep thats right, 4-6,000 kgs for basically using a sharper pencil.
(b) The palmtop wins hands down ....(posted 01 June 2001 02:28)
We started looking at cockpit computer devices over 6 years ago, but I haven’t seen anything smaller than a laptop. Some of the devices that i have seen are in use with SAS, Fedex and BBJ operators. I have the BLT (Boeing Laptop Tool for BBJ's) loaded on this PC, so I will only pass comments on that.
The program gives you the option to calculate the takeoff weight at the actual temperature and the max assumed temperature. Depending on the aircraft/runway, this max assumed calculation may once again make you field length limited. This logic is also used for ACARS calculated takeoff performance, you get the option of actual or max.
SO while you may be shocked at the fact that our assumed temperature calculations create a field length limited situation, you are willing to accept portable computers that do exactly the same thing!
These devices do include obstacle data which is commercially available from companies such as Jeppesen and SITA.
Flanker used the word "Airmanship", well by using paper charts, crews have the ability to see the maximum reduced temperature (which may have made them field length limited), they can then decide to use a lower assumed temperature to increase their stopping buffer. I've spoken to IP's who say that they try to drop 3-5C off the max. Their ability and desire to do this creates a problem for our future plans to produce ACARS takeoff data.
Now its time for my Guinness factory tour, I wonder if they have intravenous packs.....
Mutt
I'm trying to work out if Balerphon flies the space shuttle or a Cessna 150?
Considering that I shocked a number of pilots, I'm surprised at how few have actually come out and told me that our procedures are any different to those in use with other airlines???
John_Tullamarine
(b) Increasing thrust in the OEI case ? (posted 31 May 2001 06:35)
Although the takeoff calculation is based on the assumed temperature without the crew having to increase the takeoff thrust, the VMCG is based on the actual temperature for the rating in use in order to allow the crew the option of increasing the thrust.
(iii) Use of computer in lieu of AFM ?
Yep, this is the way to go, the digital version of the B744 AFM allows 4,000 - 6,000 kgs increase in takeoff weight from some hot/high airports (For exactly the same conditions). Yep thats right, 4-6,000 kgs for basically using a sharper pencil.
(b) The palmtop wins hands down ....(posted 01 June 2001 02:28)
We started looking at cockpit computer devices over 6 years ago, but I haven’t seen anything smaller than a laptop. Some of the devices that i have seen are in use with SAS, Fedex and BBJ operators. I have the BLT (Boeing Laptop Tool for BBJ's) loaded on this PC, so I will only pass comments on that.
The program gives you the option to calculate the takeoff weight at the actual temperature and the max assumed temperature. Depending on the aircraft/runway, this max assumed calculation may once again make you field length limited. This logic is also used for ACARS calculated takeoff performance, you get the option of actual or max.
SO while you may be shocked at the fact that our assumed temperature calculations create a field length limited situation, you are willing to accept portable computers that do exactly the same thing!
These devices do include obstacle data which is commercially available from companies such as Jeppesen and SITA.
Flanker used the word "Airmanship", well by using paper charts, crews have the ability to see the maximum reduced temperature (which may have made them field length limited), they can then decide to use a lower assumed temperature to increase their stopping buffer. I've spoken to IP's who say that they try to drop 3-5C off the max. Their ability and desire to do this creates a problem for our future plans to produce ACARS takeoff data.
Now its time for my Guinness factory tour, I wonder if they have intravenous packs.....
Mutt
Guest
Posts: n/a
Does this mean that I can retire my pencil sharpener now ? - and, of course the computer can do it much more accurately (as in closer to the "legal" limit bit).
Re obstacles, and this is an area in which I have had a long and detailed interest, the situation is still a bit difficult. The increasing availability of sat imaging data will progressively make the majority of the difficulty go away ........provided that operators at the nasty end take an interest.
I have no a priori difficulty with the use of flight deck gadgets. However, their uncritical acceptance in line operations does raise difficulties with some airports in some conditions. Likewise making the takeoff accel stop limiting. Unless there is a significant dollar benefit, why accept a situation where you are just about guaranteeing an overrun with a critical refusal ? It really comes down to a dollar risk assessment. Is it better to save a few dollars regularly, considering the diminishing returns aspects of hotend benefits when viewed against the high dollar cost of the occasional prang ? And this, of course, doesn't consider the stress wear and tear on the guys in the pointy end.
I would still love to sit in on the three-holer max grunt min weight blast off ....
[This message has been edited by john_tullamarine (edited 01 June 2001).]
Re obstacles, and this is an area in which I have had a long and detailed interest, the situation is still a bit difficult. The increasing availability of sat imaging data will progressively make the majority of the difficulty go away ........provided that operators at the nasty end take an interest.
I have no a priori difficulty with the use of flight deck gadgets. However, their uncritical acceptance in line operations does raise difficulties with some airports in some conditions. Likewise making the takeoff accel stop limiting. Unless there is a significant dollar benefit, why accept a situation where you are just about guaranteeing an overrun with a critical refusal ? It really comes down to a dollar risk assessment. Is it better to save a few dollars regularly, considering the diminishing returns aspects of hotend benefits when viewed against the high dollar cost of the occasional prang ? And this, of course, doesn't consider the stress wear and tear on the guys in the pointy end.
I would still love to sit in on the three-holer max grunt min weight blast off ....
[This message has been edited by john_tullamarine (edited 01 June 2001).]
Guest
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.. then amend my previous post about 3 holers - getting my conversations mixed up ...
I see now about no derate .... delete the request for the email ....
We don't see the likes of the machine on the bottom of the world so my recollection would be passe to those of you elsewhere .. but I still can recall as an undergraduate my first watching of its takeoff (at SYD on the demo tour). The mach diamonds and the adominal viscera excitation remain quite vividly with me .... we were at the time standing adjacent to the runway ..... with our hands clasped tightly to our ears ... wonderful stuff ....
[This message has been edited by john_tullamarine (edited 02 June 2001).]
I see now about no derate .... delete the request for the email ....
We don't see the likes of the machine on the bottom of the world so my recollection would be passe to those of you elsewhere .. but I still can recall as an undergraduate my first watching of its takeoff (at SYD on the demo tour). The mach diamonds and the adominal viscera excitation remain quite vividly with me .... we were at the time standing adjacent to the runway ..... with our hands clasped tightly to our ears ... wonderful stuff ....
[This message has been edited by john_tullamarine (edited 02 June 2001).]