Here we go again; PERFORMANCE !! Our favorite topic!
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Here we go again; PERFORMANCE !! Our favorite topic!
This is an on going question in which I can not find a difinitive answer any where in print. I get lots of feed back on people who think they know the answer, but when I ask for something that I can read in PRINT to get a definative answer.....I'm back to square one.
Here's the question: (Keep in mind I operate Part 91; so 135 or 121 answers I'm not really concerned with.)
Part 25 certifies all aircraft to be able to meet a minimum climb gradiet of 2.4 percent for certification purposes. Now... Let's say I'm taking off out of Bangkok on a hot day of 43 degrees C. I am taking off at a weight in which my FMS gives me a performance alert in yellow; runway requirement is met; however, I can not meet my climb gradient of 2.4 percent. Where does it say anywhere I have to be able to meet that 2.4 percent climb gradiet for takeoff??? I'm not on a SID, so I don't have to make the 3.3 percent (minimum) climb; I'm not on an ODP...absolutely no obstacles out there to worry about. Keep in mind....the AFM does not say you HAVE to meet 2.4 climb gradient (Gulfstream G200).
So do I have to make a minimum 2.4 percent?....or no??. Can I possibly takeoff with a climb gradient ...0f lets say ...2.3 percet and still be legal?? ---If not...Pleas point out to me in Print where I can get that information. Any help would be most appreciated.
Here's the question: (Keep in mind I operate Part 91; so 135 or 121 answers I'm not really concerned with.)
Part 25 certifies all aircraft to be able to meet a minimum climb gradiet of 2.4 percent for certification purposes. Now... Let's say I'm taking off out of Bangkok on a hot day of 43 degrees C. I am taking off at a weight in which my FMS gives me a performance alert in yellow; runway requirement is met; however, I can not meet my climb gradient of 2.4 percent. Where does it say anywhere I have to be able to meet that 2.4 percent climb gradiet for takeoff??? I'm not on a SID, so I don't have to make the 3.3 percent (minimum) climb; I'm not on an ODP...absolutely no obstacles out there to worry about. Keep in mind....the AFM does not say you HAVE to meet 2.4 climb gradient (Gulfstream G200).
So do I have to make a minimum 2.4 percent?....or no??. Can I possibly takeoff with a climb gradient ...0f lets say ...2.3 percet and still be legal?? ---If not...Pleas point out to me in Print where I can get that information. Any help would be most appreciated.
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Interesting question, as per 91, there is nothing stopping you from taking off, level off at 50 feet and continue the takeoff path with zero climb gradient. But you are also operating an aircraft certified under FAR25 that stipulates the required gradients for aircraft certification, these are published in your AFM. So if you make the mistake of thinking that Bangkok has zero takeoff obstacles when in fact it has obstacles on 3 of the 4 runways, you might get caught by this from FAR 91.
Combined with the fact you didn't comply with the AFM limitations for the required profiles.
(3) Except as provided in paragraph (f)(4) of this section, no pilot may takeoff under IFR from a civil airport having published obstacle departure procedures (ODPs) under part 97 of this chapter for the takeoff runway to be used, unless the pilot uses such ODPs or an alternative procedure or route assigned by air traffic control.
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FAR 25 Subpart G - Operating Limitations and Information
Operating Limitations - 25.1533 Additional Operating Limitations
Airplane Flight Manual - 25.1583 Operating limitations
Have you read the chapter LIMITATIONS of your AFM? What does it say about performance limitations?
Operating Limitations - 25.1533 Additional Operating Limitations
Airplane Flight Manual - 25.1583 Operating limitations
Have you read the chapter LIMITATIONS of your AFM? What does it say about performance limitations?
Last edited by HazelNuts39; 7th Aug 2013 at 08:06. Reason: formating
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HazelNuts39, for the purpose of discussion, the quoted references to FAR25 apply for aircraft certification and not operations.
Remember that he is talking about operating under FAR91, and that doesn't have any performance requirements related to takeoff flight path, unlike FAR121/135.
As for having less than 2.4% gradient, this happens a lot on the B777, Boeing consider the requirement as an instantaneous gradient and not continuous.
Remember that he is talking about operating under FAR91, and that doesn't have any performance requirements related to takeoff flight path, unlike FAR121/135.
As for having less than 2.4% gradient, this happens a lot on the B777, Boeing consider the requirement as an instantaneous gradient and not continuous.
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Originally Posted by mutt
the quoted references to FAR25 apply for aircraft certification and not operations.
mutt, for the purpose of discussion, I am not talking about the takeoff flight path or obstacle clearance requirements. The WAT limits are a limitation of the certificate of airworthiness. It is illegal to operate an airplane outside the limitations stated in its CofA.
Last edited by HazelNuts39; 7th Aug 2013 at 15:10. Reason: shorter
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1jz,
Boeing is correct in stating that the WAT limit gradients are instantaneous. No need to go looking for a Boeing document because it is clearly stated in the applicable regulations. FAR 25.121(a), (b) and (c) require instantaneous gradients. The sole purpose of those requirements is to define the Operating Limitation stated in 25.1533(a)(1), which is also the operating envelope of weight-altitude-temperature conditions that need to be considered for takeoff performance data. Takeoff distance information, for example, is only valid within that envelope.
The continuous takeoff flight path, on the other hand, is defined in FAR 25.111 and 25.115. The net takeoff flight path is provided in the AFM as Performance Information (ref. 25.1587(b)) to permit compliance with operating regulations that require obstacle clearance.
FAR 25.121(b) requires a "steady gradient of climb (of not less than) 2.4 percent for two-engine airplanes (...), at V2 with the critical engine inoperative, the remaining engine at the takeoff power or thrust available at the time the landing gear is fully retracted".
Consequently, at the maximum takeoff weight limited by the climb requirements of 25.121(a) through (c), the gradient of the takeoff flight path will be not less than 2.4 % at the time the landing gear is fully retracted. After that point the gradient will gradually reduce due to the normal reduction of thrust with increasing altitude.
Boeing is correct in stating that the WAT limit gradients are instantaneous. No need to go looking for a Boeing document because it is clearly stated in the applicable regulations. FAR 25.121(a), (b) and (c) require instantaneous gradients. The sole purpose of those requirements is to define the Operating Limitation stated in 25.1533(a)(1), which is also the operating envelope of weight-altitude-temperature conditions that need to be considered for takeoff performance data. Takeoff distance information, for example, is only valid within that envelope.
The continuous takeoff flight path, on the other hand, is defined in FAR 25.111 and 25.115. The net takeoff flight path is provided in the AFM as Performance Information (ref. 25.1587(b)) to permit compliance with operating regulations that require obstacle clearance.
FAR 25.121(b) requires a "steady gradient of climb (of not less than) 2.4 percent for two-engine airplanes (...), at V2 with the critical engine inoperative, the remaining engine at the takeoff power or thrust available at the time the landing gear is fully retracted".
Consequently, at the maximum takeoff weight limited by the climb requirements of 25.121(a) through (c), the gradient of the takeoff flight path will be not less than 2.4 % at the time the landing gear is fully retracted. After that point the gradient will gradually reduce due to the normal reduction of thrust with increasing altitude.
Last edited by HazelNuts39; 9th Aug 2013 at 21:03. Reason: additional text, grammar
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Keep in mind I operate Part 91......Gulfstream G200
For whatever it's worth, here's how I see it:
Taking off at a WAT which would not result in at least a 2.4% 2nd segment climb as per the AFM perf charts would be in contravention of AFM limitations. As such, this action would be in violation of FAR 91.9 and arguably, 91.13 as well.
westhawk
Taking off at a WAT which would not result in at least a 2.4% 2nd segment climb as per the AFM perf charts would be in contravention of AFM limitations. As such, this action would be in violation of FAR 91.9 and arguably, 91.13 as well.
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Reverse Thrust VS Reverse Pitch
Slightly off topic but whilst performance minded people are on this thread I would like to ask a question regarding European Public Transport and the use of reverse...
The aircraft that I currently fly (turboprop) has landing distances published in the AFM for landing WITH reverse and landing WITHOUT reverse.
When calculating the regulatory factors for public transport I have always used the landing WITHOUT reverse as it was my understanding that reverse could not be used in these calculations.
Recently however I have heard it said that this only applies to jets and not to turboprops. The reason stated - the turboprop reverse pitch is a function of the engine and that if the engine is running then the reverse will work! (unlike a separate system on a jet) This seems a bold statement to me. Any ideas???
What then happens with an engine inop? You would have to use the WITHOUT reverse figures. Perhaps you could plan to use the WITH reverse figures for destination and WITHOUT reverse for the alternate but this all seems plucked out of thin air to me.
The aircraft that I currently fly (turboprop) has landing distances published in the AFM for landing WITH reverse and landing WITHOUT reverse.
When calculating the regulatory factors for public transport I have always used the landing WITHOUT reverse as it was my understanding that reverse could not be used in these calculations.
Recently however I have heard it said that this only applies to jets and not to turboprops. The reason stated - the turboprop reverse pitch is a function of the engine and that if the engine is running then the reverse will work! (unlike a separate system on a jet) This seems a bold statement to me. Any ideas???
What then happens with an engine inop? You would have to use the WITHOUT reverse figures. Perhaps you could plan to use the WITH reverse figures for destination and WITHOUT reverse for the alternate but this all seems plucked out of thin air to me.
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Quote from FAR 25.125 Landing:
Are you sure your information is from the approved AFM, or if the AFM has unapproved sections, from a section of the AFM that is marked as APPROVED?
(g) If any device is used that depends on the operation of any engine, and if the landing distance would be noticeably increased when a landing is made with that engine inoperative, the landing distance must be determined with that engine inoperative unless the use of compensating means will result in a landing distance not more than that with each engine operating.
Last edited by HazelNuts39; 10th Aug 2013 at 13:20.
