Assumed Temp Reduced without analysis?
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Assumed Temp Reduced without analysis?
Boeing aircraft, no runway analysis (tabulated TOFF charts) available for the airport.
Can you legally use reduced TOFF thrust? One might say sure, the runway is long, dry today etc etc, but I am asking about the thin line of legal responsibility here.
If you do and you end up rejecting and ending up on the grass (perhaps for other factors) are you in the deep?
Then of course comes the question of wet runway, very long one, high OAT, low weight. reduced V1. Who is telling me that I am going to stay within ASDA?
Maybe just use CDU derated N1 only?
Until now I have never been at an airport without available tabul. charts myself, but I had this question from a old buddy recently and he got me thinking.
Shouldn't the company have airport analysis for all the approved airports (Part C) to operate before even going there?
All this assumes earlier software or EFB without runway analysis included.
Can you legally use reduced TOFF thrust? One might say sure, the runway is long, dry today etc etc, but I am asking about the thin line of legal responsibility here.
If you do and you end up rejecting and ending up on the grass (perhaps for other factors) are you in the deep?
Then of course comes the question of wet runway, very long one, high OAT, low weight. reduced V1. Who is telling me that I am going to stay within ASDA?
Maybe just use CDU derated N1 only?
Until now I have never been at an airport without available tabul. charts myself, but I had this question from a old buddy recently and he got me thinking.
Shouldn't the company have airport analysis for all the approved airports (Part C) to operate before even going there?
All this assumes earlier software or EFB without runway analysis included.
Last edited by st martin; 16th Jan 2014 at 11:49.
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Supposing that the YES refers to the legality question and not the rest of them, do you mind elaborating on the way you assure it?
It is not a voting thread mate.
It is not a voting thread mate.
Why is there a trend for posts to seek a legal answer?
Technically, a question might be ‘how-to’; or when considering operational aspects, ‘should-we’ (self) be doing this.
Thus, with an appropriate question – thinking before you ask, an answer or a new line of thought might emerge.
Should we be doing this? Not in a commercial operation, because an analysis contributes to the required level of safety.
How to do it – take off without analysis? Assuming that there is no alternative;- very cautiously, identify and minimise the risks. Consult all available information – runway length, met, etc; use the AFM data to check runway and WAT performance. Look out of the window and assess the local terrain. Use full power, optimum configuration.
Consider influencing factors – why would you want to use reduced thrust.
If this is a hypothetical question, perhaps spend more time to consider the scenario; context biases thoughts.
Is the use of reduced thrust unwarranted management pressure – the need to reduce cost? There has to be a balance between safety and economics, and whilst the sharp end operation is best placed to make a final judgement it doesn’t mean that all responsibility for this is placed on the pilot. Know when to say No - politely report the problem to management – give them a solution with the problem – because you have thought about the safety issue from your perspective, in context.
Nothing personal, but are pilots hiding their responsibilities behind a legal cover? Is there a reluctance to think - failing to consider what the situation is, really understand it, always use an SOP?
If you ask the right question then the answer is obvious; so what is the ‘right’ question?
Are regulations more closely aligned to a legal framework (operators need a lawyer to interpret them).
Legalities and operating rules don’t prevent accidents; that responsibility is with the pilot.
Thus the question might be how – in difficult, complex, or ambiguous situations, how might that responsibility be exercised?
Technically, a question might be ‘how-to’; or when considering operational aspects, ‘should-we’ (self) be doing this.
Thus, with an appropriate question – thinking before you ask, an answer or a new line of thought might emerge.
Should we be doing this? Not in a commercial operation, because an analysis contributes to the required level of safety.
How to do it – take off without analysis? Assuming that there is no alternative;- very cautiously, identify and minimise the risks. Consult all available information – runway length, met, etc; use the AFM data to check runway and WAT performance. Look out of the window and assess the local terrain. Use full power, optimum configuration.
Consider influencing factors – why would you want to use reduced thrust.
If this is a hypothetical question, perhaps spend more time to consider the scenario; context biases thoughts.
Is the use of reduced thrust unwarranted management pressure – the need to reduce cost? There has to be a balance between safety and economics, and whilst the sharp end operation is best placed to make a final judgement it doesn’t mean that all responsibility for this is placed on the pilot. Know when to say No - politely report the problem to management – give them a solution with the problem – because you have thought about the safety issue from your perspective, in context.
Nothing personal, but are pilots hiding their responsibilities behind a legal cover? Is there a reluctance to think - failing to consider what the situation is, really understand it, always use an SOP?
If you ask the right question then the answer is obvious; so what is the ‘right’ question?
Are regulations more closely aligned to a legal framework (operators need a lawyer to interpret them).
Legalities and operating rules don’t prevent accidents; that responsibility is with the pilot.
Thus the question might be how – in difficult, complex, or ambiguous situations, how might that responsibility be exercised?
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WizofOz you know you can do it with Full Thrust because QRH gives you the info on max weight allowed for specific lengths and temperatures.
The question is if you can go for less than full and assure TODA=ASDA, as well as climb segment limitations etc.
alf, this is not a question for 1st class operators obviously. But when someone calls you from halfway around the world and tells you that he found himself at an airport, ready to depart and his FO informed him that they don't have tabulated charts but they usually do reduced takeoff with assumed temperature, kinda surprises you.
Never had to deal with it, but started thinking if it is even possible or legal first of all.
You see LeftCoaster answered "Clearly Yes" actually "YES!" so seems that I am not the only one thrown out of balance here.
Thanks for the answers gentlemen, keep it coming.
The question is if you can go for less than full and assure TODA=ASDA, as well as climb segment limitations etc.
alf, this is not a question for 1st class operators obviously. But when someone calls you from halfway around the world and tells you that he found himself at an airport, ready to depart and his FO informed him that they don't have tabulated charts but they usually do reduced takeoff with assumed temperature, kinda surprises you.
Never had to deal with it, but started thinking if it is even possible or legal first of all.
You see LeftCoaster answered "Clearly Yes" actually "YES!" so seems that I am not the only one thrown out of balance here.
Thanks for the answers gentlemen, keep it coming.
Does falling off the chair, laughing, counts as being thrown out of balance?
Generic RWC take care of runway requirements and if there are no obstacles, you are legally kosher. If they didn't come with your NG for FSX, tough luck.
Generic RWC take care of runway requirements and if there are no obstacles, you are legally kosher. If they didn't come with your NG for FSX, tough luck.
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Two points:
1) If this is a commercial operation you should not do it. If it is 'private', you "pays your money etc etc"
2) If you actually have any management get them to authorise your take-off IN DETAIL - in writing ie flap, power etc.
In private flying pilots many many times eyeball a strip and decide to go. Some crash and burn.
1) If this is a commercial operation you should not do it. If it is 'private', you "pays your money etc etc"
2) If you actually have any management get them to authorise your take-off IN DETAIL - in writing ie flap, power etc.
In private flying pilots many many times eyeball a strip and decide to go. Some crash and burn.
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Clandestino, you are trying to be sarcastic but you are not providing any answer for help.
"Generic RCW"? "if you have no obstacles"? FSX?
Why you assume NG?
Its a generic question, goes for all runways, short-long, obstacles or not. You can do reduced N! on all with approved runway analysis data.
Can you do it without?
Personal opinions and not supported reasoning does not help.
Keep the jokes for your FSX buddies and RTFQ. Its not about actually taking off or not.
"Generic RCW"? "if you have no obstacles"? FSX?
Why you assume NG?
Its a generic question, goes for all runways, short-long, obstacles or not. You can do reduced N! on all with approved runway analysis data.
Can you do it without?
Personal opinions and not supported reasoning does not help.
Keep the jokes for your FSX buddies and RTFQ. Its not about actually taking off or not.
Why you assume NG?
Its a generic question
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i am afraid there will always be a smartass coming up with an inadequate answer and boasting super confidence to his believes.
But if i had to decide without time to look in the books etc, I wouldn't do it. Normal N1, period.
Maybe there is a note somewhere but I definitely don't remember it. I think the ATM for reduced N1 is only allowed along with using an approved data tool for runway analysis.
It has been a while since I used a Boeing QRH but I think it only provides for weight you can accommodate for the specific runway that day. I do not recall a chart that you can use to derive the ASDA with a different N1, let alone doing wet V1 reductions for the specific runway length.
By all means, runway analysis is required by the operator (for all his types used) in order to be authorized to operate at a specific airport. Someone referred to it earlier, all approved airports in an OM Part C. Correct me if I am wrong.
Just my 2c.
But if i had to decide without time to look in the books etc, I wouldn't do it. Normal N1, period.
Maybe there is a note somewhere but I definitely don't remember it. I think the ATM for reduced N1 is only allowed along with using an approved data tool for runway analysis.
It has been a while since I used a Boeing QRH but I think it only provides for weight you can accommodate for the specific runway that day. I do not recall a chart that you can use to derive the ASDA with a different N1, let alone doing wet V1 reductions for the specific runway length.
By all means, runway analysis is required by the operator (for all his types used) in order to be authorized to operate at a specific airport. Someone referred to it earlier, all approved airports in an OM Part C. Correct me if I am wrong.
Just my 2c.
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While the rule books might vary a little in the specific detail, for heavies, one needs to ensure a number of requirements are met - runway, climb, obstacle, etc., etc.
Several ways to approach this, given that the work, itself, is pretty straightforward, albeit that the detail can provide for head scratching at times -
(a) the operator provides individual runway charts addressing all requirements and providing a limiting RTOW
(b) the operator provides general takeoff charts which the pilot can use to generate an RTOW using the input data prescribed by the operator. Generally, this will produce a weight somewhat less than (a), which is why commercial operators use (a) with (b) as the get out of jail backup.
(c) the pilot pulls out the AFM, gets all the necessary input data - that's the hard bit, usually, and does the sums. Time taken could vary from 10-15 minutes to a day or so. Generally, not a practical option, especially for commercial operations
(d) any variety of not so sensible ways to do it ...
Whether the aim is to use full thrust or a reduced thrust just adds another iteration to the process to end up with the limiting RTOW case.
Main thing is .. winging it on the day (ie "she'll be all right") is not a good idea and, sooner or later, is going to end in tears.
Several ways to approach this, given that the work, itself, is pretty straightforward, albeit that the detail can provide for head scratching at times -
(a) the operator provides individual runway charts addressing all requirements and providing a limiting RTOW
(b) the operator provides general takeoff charts which the pilot can use to generate an RTOW using the input data prescribed by the operator. Generally, this will produce a weight somewhat less than (a), which is why commercial operators use (a) with (b) as the get out of jail backup.
(c) the pilot pulls out the AFM, gets all the necessary input data - that's the hard bit, usually, and does the sums. Time taken could vary from 10-15 minutes to a day or so. Generally, not a practical option, especially for commercial operations
(d) any variety of not so sensible ways to do it ...
Whether the aim is to use full thrust or a reduced thrust just adds another iteration to the process to end up with the limiting RTOW case.
Main thing is .. winging it on the day (ie "she'll be all right") is not a good idea and, sooner or later, is going to end in tears.
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No runway analysis no reduced Takeoff N1.
There is no legal safety net if you end up in the fields.
Your manuals will cover you for the ZFW and the TOGW you decided-accepted, but if you end up with an overrun after a RTO using less than full N1, they will ask you how you ensured the balance field requirements. I do not think there is a manufacturer's page anywhere that will save your neck.
There is no legal safety net if you end up in the fields.
Your manuals will cover you for the ZFW and the TOGW you decided-accepted, but if you end up with an overrun after a RTO using less than full N1, they will ask you how you ensured the balance field requirements. I do not think there is a manufacturer's page anywhere that will save your neck.
In the days when we used to use paper charts, we were permitted, in my company, to use the data for another runway provided that that runway was shorter, higher elevation and not obstacle limited (ie conservative). That got me out of trouble a few times. Perfectly legal as per our manuals.
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YES…in response to the original question, YES, it is seriously risky to simply assume that you may reduce thrust (by any method) if there are no charts, electronic or otherwise, which would provide the correct numbers. Even full N1 (or EPR) without the same information is risky, despite all your experience. So my answer again…YES…btw, I flew at a private Op (heavy jet) once with a guy who thought the numbers provided from the FMC were perfectly adequate and the reductions in thrust were arbitrarily applied at every airport we flew out of despite the requirement to have proper performance charts. I left…he got fired! End of career…for him!
The OP asked two questions.
(with no runway analysis (tabulated TOFF charts) available for the airport.)
And
If the answer to the first is YES then the answer to the second should be NO.
I think that Left Coaster's "YES" was in answer the second question.
Can you legally use reduced TOFF thrust?
And
Shouldn't the company have airport analysis for all the approved airports (Part C) to operate before even going there?
I think that Left Coaster's "YES" was in answer the second question.
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Tangential, but important
alf5071h:
Knowing/formulating the right question is important in a multitude of arenas. I'm not always the sharpest knife in the drawer, but if I take my time and compose the right question, I can make the reigning genius stop and rethink his position!
If you ask the right question then the answer is obvious; so what is the ‘right’ question?
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OK ok ok…not a flight deck lawyer (or a real one actually) but the original question had a question about the thin legal line…you guys want to use assumed temp to reduce thrust without proper charts? That's at your own risk as far as I am concerned. My opinion? Not legal. So YES, it is risky, you do so at your peril as far as I am concerned. LC…OUT!
