Are performance graphs going out of fashion?
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Are performance graphs going out of fashion?
Hello
I looked at 2010 Boeing 737NG and CL manuals. NG manuals doesn't have any graphs at all. CL still has 1 but very simple graph. I find myself much easier to use tables. I assume it's also safer.
Do they still use those graphs on ATPL exams? It was never possible to say which answer is correct...
I looked at 2010 Boeing 737NG and CL manuals. NG manuals doesn't have any graphs at all. CL still has 1 but very simple graph. I find myself much easier to use tables. I assume it's also safer.
Do they still use those graphs on ATPL exams? It was never possible to say which answer is correct...
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Originally Posted by Turbavykas
I looked at 2010 Boeing 737NG and CL manuals. NG manuals doesn't have any graphs at all. CL still has 1 but very simple graph.
OPS 1.475
...
(b) An operator shall ensure that the approved performance Data contained in the Aeroplane Flight Manual is used to determine
compliance with the requirements of the appropriate Subpart, supplemented as necessary with other data acceptable
to the Authority as prescribed in the relevant Subpart. When applying the factors prescribed in the appropriate
Subpart, account may be taken of any operational factors already incorporated in the Aeroplane Flight Manual performance
data to avoid double application of factors.
...
(b) An operator shall ensure that the approved performance Data contained in the Aeroplane Flight Manual is used to determine
compliance with the requirements of the appropriate Subpart, supplemented as necessary with other data acceptable
to the Authority as prescribed in the relevant Subpart. When applying the factors prescribed in the appropriate
Subpart, account may be taken of any operational factors already incorporated in the Aeroplane Flight Manual performance
data to avoid double application of factors.
Originally Posted by Turbavykas
I find myself much easier to use tables. I assume it's also safer.
The real tables (not that FCOM crap) are usually created by companies, which are specialized in aircraft performance. They take the data from the AFM graphs and convert it into so called airport analysis chart, which give you the PLTOM (performance limited take-off masses) for a given runway and many possible weather (wind, OAT), configuration (bleeds, anti-ice, flaps) conditions - but they are rounded to 1 kg, not 100kg, therefore very precise (not to be believed like they were sent from God himself though).
What does it matter if you are 99kg out on a 63000 aeroplane, it is 0.15%!
Precision is not the same as accuracy. 63149 kg is a precise number, but with standard weights being used for passengers, inaccuracies in fuel gauges and the weighing equipment used to get the basic weight of the aircraft, it is not necessarily an accurate number. Figures rounded to the nearest tenth of a tonne are fine for a large aircraft. If you are doing the rounding yourself then by all means round in the safe direction, but don't lose sleep over a possible discrepancy of 99kg.
Precision is not the same as accuracy. 63149 kg is a precise number, but with standard weights being used for passengers, inaccuracies in fuel gauges and the weighing equipment used to get the basic weight of the aircraft, it is not necessarily an accurate number. Figures rounded to the nearest tenth of a tonne are fine for a large aircraft. If you are doing the rounding yourself then by all means round in the safe direction, but don't lose sleep over a possible discrepancy of 99kg.
Safer? Debatable. For example, if the climb limit weight in the FCOM is 63.1 - how do you know if it's 63050 kg or 63149 kg? 99 kg may be one passenger with luggage you will have to offload, because you're not sure if you can satisfy the certification performance requirements.
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We are now getting into underlying concerns.
(a) practical engineering - the certification work up activities are based on rational accuracies
(b) certification - the final AFM/POH has to declare numbers which are reasonable results determined from the rational certification work up. However, being written down numbers, they are black and white
(c) legal - make sure that the load sheet, etc., does not disclose a weight figure in excess of the black and white figure in the AFM
Does it matter all that much if the actual weight is a few kilos up or down compared to what you might think it was ?
(a) for the flight, of course not (engineering hat on)
(b) at the Inquiry following the mishap, one had better believe in black and white because the legal folks tend to play that game.
(a) practical engineering - the certification work up activities are based on rational accuracies
(b) certification - the final AFM/POH has to declare numbers which are reasonable results determined from the rational certification work up. However, being written down numbers, they are black and white
(c) legal - make sure that the load sheet, etc., does not disclose a weight figure in excess of the black and white figure in the AFM
Does it matter all that much if the actual weight is a few kilos up or down compared to what you might think it was ?
(a) for the flight, of course not (engineering hat on)
(b) at the Inquiry following the mishap, one had better believe in black and white because the legal folks tend to play that game.
Having left behind Mr Lockheed's innumerable charts with military retirement; I miss them in my current steads. As check airmen, we had to be able to explain and run thru take-off and landing problems like the flight engineer. I had a much better "feel" for the cababilities of the plane. Tabular data just isn't a comprehensive and accurate. I don't know refusal speed, actual Vmcg/Vmca for the current conditions. Then again, the current generation only wants to look at the FMS.
John: I hope to see you at Avalon in February. New Global Vision is a hoot!
GF
John: I hope to see you at Avalon in February. New Global Vision is a hoot!
GF
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the current generation only wants to look at the FMS.
I believe one of the reasons why lots of pilots are not aware of some performance and their related graphs is that they are not distributed to the pilots.
A simple flight planning and performance manual would show all relevant graphs to crews and I could ask how many of my colleagues have it...maybe 10%?5%?
I think it is the Airline responsability to distribute all manuals readily available to their crews and not only the usual FCOms..
Last edited by de facto; 30th Nov 2012 at 03:50.
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I hope to see you at Avalon in February
Count on it. When you know the actual dates your team is out here, do let me know and I'll organise a few of the boys for a meal. Pleasant evening was had the other night with Mutt and a few other folks when he was in town.
I think it is the Airline responsability to distribute all manuals
I'm with you. I was brought up as a pilot in such an airline and, in my own ops eng work over the years, have done the same.
Count on it. When you know the actual dates your team is out here, do let me know and I'll organise a few of the boys for a meal. Pleasant evening was had the other night with Mutt and a few other folks when he was in town.
I think it is the Airline responsability to distribute all manuals
I'm with you. I was brought up as a pilot in such an airline and, in my own ops eng work over the years, have done the same.
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Why do you consider tables to be safer?
You just have to look for a number in the table and sometimes do the simple math.
I would say it's like comparing analog and digital...
Theoretically analog can be more precise but for some reason everything went to digital...
Last edited by Turbavykas; 30th Nov 2012 at 07:17.
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Performance graphs are still available in the AFM as said above. However in the real on the line world i haven't seen a graph in the last 15 years or so. It was tables in books, and for the last 7 years its been a performance program on an EFB. Those are extremely precise right at the edge of the possible performance, therefore one needs to be very careful what options to activate and which values to enter. As someone mentioned above standard weights alone will bring quite a big uncertainty factor into the game.
