Take off profile to 1500 ft
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Take off profile to 1500 ft
Can any one tell me the exact phases of the take off profile to 1500 ft?? as none of my ops manuals has it written anywhere?? From distant memory i recall phase 1 V2 to 35ft then ph2 to 400 ft gear up phase 3 acceleration with flap retract then climb tp 1500ft (ph4) is this correct if not can somebody put me straight please. Many thanks . ohh and could you include the gross and net gradients for each phase? Thanks
[ 10 July 2001: Message edited by: lets go nads ]
[ 10 July 2001: Message edited by: lets go nads ]
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1. V2 to Gear up 2.Gear up to min flap retraction alt i.e 400' 3.Accel segment...V2 to final segment clb speed...flaps are retracted. 4.Final segment clb speed...Flaps up...Max cont thrust to 1500' Gross gradient refers to pressure alts for calculation of obstacle clearence and flap retraction alt Net gradient is used for purposes of clearing obstacles by 35' min
[ 10 July 2001: Message edited by: TR3 ]
[ 10 July 2001: Message edited by: TR3 ]
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Second segment gradients:
2 engine, 2.4% gross, 1.6% net.
4 engine, 3.0% gross, 2.0% net.
The gross is what's referred to as the "climb" limit. It is simply a density altitude limiting weight. Has nothing to do with obstacles. The net has to clear all obstacles in the takeoff flight path by at least 35 feet.
2 engine, 2.4% gross, 1.6% net.
4 engine, 3.0% gross, 2.0% net.
The gross is what's referred to as the "climb" limit. It is simply a density altitude limiting weight. Has nothing to do with obstacles. The net has to clear all obstacles in the takeoff flight path by at least 35 feet.
Moderator
A point or two of clarification..
Segments and WAT limits (weight-(for)altitude - (and)temperature airworthiness climb limits) all relate to the OEI case.
It is presumed that the AEO case will be flown in such a manner that the aircraft remains above the OEI profile and, if the escape path is critical, follows the OEI or alternatively nominated AEO (with a fallback to OEI) tracks.
First segment - from the end of TOD (ie 35 feet) to the point where the gear has completed the retraction. This segment is quite variable and may not exist in some aircraft at all and for others in some circumstances - it is a balance between varying climb performance and a constant retraction time.
Second segment - extends to a minimum of 400 feet but, depending on the aircraft, may be driven to a higher level (normally 1500 feet) for obstacle clearance convenience. Some aircraft (eg Dart powered) have systems limits which further restrict this option (for the Dart - 600 feet).
There may be either 4 or 5 segments. If the aircraft requires an acceleration from the fourth segment speed to the final en-route climb speed, that is done at the end of the fourth segment (some British aircraft have this arrangement).
There are similar WAT limits for 3-engined aircraft as well.
The calculations are supposed to be done for geometric heights, not pressure heights - ie including altimeter corrections.
The gross flight path should resemble the aircraft's actual flight path at limiting weights. The net flight path is a calculated fudge for the purpose of obstacle clearance and provides a pad for a range of adverse conditions... but don't expect it to cover you on a bumpy day - I can recall years ago in an F27, wet power, AEO, clawing our way into the sky at around 300-400 fpm in bumpy conditions and this continued for quite some time.
Doesn't even bear thinking about how we might have been placed if one had decided to quit.
The 35 feet clearance net flight path relates to a straight ahead flight path. If the escape is predicated on a turn, this is normally calculated for 15 degrees (or less - depends on the turn radius required) bank with an extra 15 feet clearance to allow for the pod/flap depression (ie we schedule a 50 feet net flight path clearance which should still give you 35 feet clearance from the lowest part of the aircraft). Have a look at the front elevation diagram for the DC8 or B707 and do the sums for 15 degrees bank and you will see where the 15 feet comes from.
The BIG problem is not the sums - you can train a monkey to play with the flight manual - it is getting accurate obstacle data.
Also, keep in mind that with jets, because of the big V2 to VCL speed split, the third segment can go on for quite some distance.
For a twin especially, the total distance to 1500 feet can be VERY MANY MILES ..... all the DC9 drivers - put your hands up and agree ....
[ 11 July 2001: Message edited by: john_tullamarine ]
Segments and WAT limits (weight-(for)altitude - (and)temperature airworthiness climb limits) all relate to the OEI case.
It is presumed that the AEO case will be flown in such a manner that the aircraft remains above the OEI profile and, if the escape path is critical, follows the OEI or alternatively nominated AEO (with a fallback to OEI) tracks.
First segment - from the end of TOD (ie 35 feet) to the point where the gear has completed the retraction. This segment is quite variable and may not exist in some aircraft at all and for others in some circumstances - it is a balance between varying climb performance and a constant retraction time.
Second segment - extends to a minimum of 400 feet but, depending on the aircraft, may be driven to a higher level (normally 1500 feet) for obstacle clearance convenience. Some aircraft (eg Dart powered) have systems limits which further restrict this option (for the Dart - 600 feet).
There may be either 4 or 5 segments. If the aircraft requires an acceleration from the fourth segment speed to the final en-route climb speed, that is done at the end of the fourth segment (some British aircraft have this arrangement).
There are similar WAT limits for 3-engined aircraft as well.
The calculations are supposed to be done for geometric heights, not pressure heights - ie including altimeter corrections.
The gross flight path should resemble the aircraft's actual flight path at limiting weights. The net flight path is a calculated fudge for the purpose of obstacle clearance and provides a pad for a range of adverse conditions... but don't expect it to cover you on a bumpy day - I can recall years ago in an F27, wet power, AEO, clawing our way into the sky at around 300-400 fpm in bumpy conditions and this continued for quite some time.
Doesn't even bear thinking about how we might have been placed if one had decided to quit.
The 35 feet clearance net flight path relates to a straight ahead flight path. If the escape is predicated on a turn, this is normally calculated for 15 degrees (or less - depends on the turn radius required) bank with an extra 15 feet clearance to allow for the pod/flap depression (ie we schedule a 50 feet net flight path clearance which should still give you 35 feet clearance from the lowest part of the aircraft). Have a look at the front elevation diagram for the DC8 or B707 and do the sums for 15 degrees bank and you will see where the 15 feet comes from.
The BIG problem is not the sums - you can train a monkey to play with the flight manual - it is getting accurate obstacle data.
Also, keep in mind that with jets, because of the big V2 to VCL speed split, the third segment can go on for quite some distance.
For a twin especially, the total distance to 1500 feet can be VERY MANY MILES ..... all the DC9 drivers - put your hands up and agree ....
[ 11 July 2001: Message edited by: john_tullamarine ]
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I guess that I fall in the monkey category 
Just to substantiate John_Tullamarines final point
For a twin especially, the total distance to 1500 feet can be VERY MANY MILES .....
Taken from the B777 AFM for a Max Weight Takeoff @ ISA.
Note: Heights and distances are referenced from Brake Release End of Runway.
Gross /Gross
Distance / Height
FEET / FEET
10215 /35 Screen Height
14120 /146 Gear-Up
22616 /400 Level-Off
55224 /400 Start Final Climb
Gross / Speed
Grad. / KIAS
2.8/ 171.5 Screen Height
3.0/ 171.5 Gear-Up
3.0/ 171.5 Level-Off
3.6/ 242.2 Start Final Climb
That’s quite a distance to be touring the countryside at 400 feet. You can almost double it for the 1500 ft distance.
Mutt.
Just to substantiate John_Tullamarines final point
For a twin especially, the total distance to 1500 feet can be VERY MANY MILES .....
Taken from the B777 AFM for a Max Weight Takeoff @ ISA.
Note: Heights and distances are referenced from Brake Release End of Runway.
Gross /Gross
Distance / Height
FEET / FEET
10215 /35 Screen Height
14120 /146 Gear-Up
22616 /400 Level-Off
55224 /400 Start Final Climb
Gross / Speed
Grad. / KIAS
2.8/ 171.5 Screen Height
3.0/ 171.5 Gear-Up
3.0/ 171.5 Level-Off
3.6/ 242.2 Start Final Climb
That’s quite a distance to be touring the countryside at 400 feet. You can almost double it for the 1500 ft distance.
Mutt.
Moderator
Aaahhh, Mutt, mate !! - don't be like that !! .... or are you trying to shame me into pulling out a Flight Manual from time to time to quantify my waffly qualitative statements ?
Actually, the monkey comment does bring up some valid points -
(a) the easy bit IS punching out the numbers - very easy with a Jesus Box and a tad slower using the 4000 pages of the Flight Manual. Those (many) of you who have sweated and slogged through Performance A will know just what the latter comment signifies. However, the "easy bit" statement still stands.
(b) the hard yakka bit is acquiring and verifying obstacle data, escape route flight paths, and so on - an absolute pain in the neck slog type exercise. If you don't do this (or someone else doesn't do it to the required standard on your behalf) then (a) results in "garbage in - garbage out".
I can recall a colleague telling me some years ago of a particular airline which routinely departed with far greater payloads than its competitors (he flew for the airline at the time). Turns out that they didn't bother at all with the obstacles, got the manufacturer to do the number crunching based on the runway length data only. So long as an engine didn't quit - no problems.
(c) where the operations engineer comes into his own is in the sensible and efficient matching of (a) to (b)
Mutt's example with the big bird is quite illustrative - but don't panic too much straight away. During the 400 feet (above runway level) cook's tour of the surrounding countryside, keep in mind that the altimeter approximates the gross flight path while the obstacle profile relates to the net flight path. As a result, critical third segment obstacles are in the vicinity of 150 feet below a twin engined aircraft in a minimum level off height WAT-limited situation.
Hence my oft espoused view that pilots need to know about these things so that they can make informed operational decisions - but you are far better off using a good ops engineer to give you the base data upon which to make your informed operational decisions.
Am I forgiven, Mutt ?
[ 11 July 2001: Message edited by: john_tullamarine ]
Actually, the monkey comment does bring up some valid points -
(a) the easy bit IS punching out the numbers - very easy with a Jesus Box and a tad slower using the 4000 pages of the Flight Manual. Those (many) of you who have sweated and slogged through Performance A will know just what the latter comment signifies. However, the "easy bit" statement still stands.
(b) the hard yakka bit is acquiring and verifying obstacle data, escape route flight paths, and so on - an absolute pain in the neck slog type exercise. If you don't do this (or someone else doesn't do it to the required standard on your behalf) then (a) results in "garbage in - garbage out".
I can recall a colleague telling me some years ago of a particular airline which routinely departed with far greater payloads than its competitors (he flew for the airline at the time). Turns out that they didn't bother at all with the obstacles, got the manufacturer to do the number crunching based on the runway length data only. So long as an engine didn't quit - no problems.
(c) where the operations engineer comes into his own is in the sensible and efficient matching of (a) to (b)
Mutt's example with the big bird is quite illustrative - but don't panic too much straight away. During the 400 feet (above runway level) cook's tour of the surrounding countryside, keep in mind that the altimeter approximates the gross flight path while the obstacle profile relates to the net flight path. As a result, critical third segment obstacles are in the vicinity of 150 feet below a twin engined aircraft in a minimum level off height WAT-limited situation.
Hence my oft espoused view that pilots need to know about these things so that they can make informed operational decisions - but you are far better off using a good ops engineer to give you the base data upon which to make your informed operational decisions.
Am I forgiven, Mutt ?
[ 11 July 2001: Message edited by: john_tullamarine ]
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Before Mutt has a chance to do that, it is worth reflecting that, for many aircraft, the worst case lies somewhere near the thrust break temperature ....
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JT, Of course I forgive you
4-Dogs, as requested.
As you can see the tour of the countryside gets quite interesting at 40C and even more so if you use a MFRH of 800 feet like we do.
This is where obtaining realistic obstacle data becomes fun.
Brake Release Gross Weight = 286897 KG
Actual Temp = 40.0 DEG C
Pressure Altitude = 0 FEET
Takeoff Thrust Break Temperature = 30.0 DEG C
Gross Track Gross
Distance Height
FEET FEET
-------- --------
12113 / 35 Screen Height
15895 / 109 Gear-Up
30688 / 400 Level-Off (51507 / 800)
80394 / 400 Start Final Climb (102526 / 800)
Gross Speed
Grad. KIAS
------ -----
2.0 / 171.0 Screen Height
2.0 / 171.0 Gear-Up
1.9 / 171.0 Level-Off
2.3 / 242.2 Start Final Climb
Mutt
4-Dogs, as requested.
As you can see the tour of the countryside gets quite interesting at 40C and even more so if you use a MFRH of 800 feet like we do.
This is where obtaining realistic obstacle data becomes fun.
Brake Release Gross Weight = 286897 KG
Actual Temp = 40.0 DEG C
Pressure Altitude = 0 FEET
Takeoff Thrust Break Temperature = 30.0 DEG C
Gross Track Gross
Distance Height
FEET FEET
-------- --------
12113 / 35 Screen Height
15895 / 109 Gear-Up
30688 / 400 Level-Off (51507 / 800)
80394 / 400 Start Final Climb (102526 / 800)
Gross Speed
Grad. KIAS
------ -----
2.0 / 171.0 Screen Height
2.0 / 171.0 Gear-Up
1.9 / 171.0 Level-Off
2.3 / 242.2 Start Final Climb
Mutt
