View Full Version : Take Off and Climb Segments...?
Thoroughly Nice Bloke...
5th Jul 2003, 20:41
I am trying to define where each of the four segments of net flight path start and finish…?
Been through my old Perf A stuff but can’t seem to find the excact definition...
and your attempts to search for any number of possible Tech Log threads has failed to unearth the previous 4000 queries about the same thing????
6th Jul 2003, 10:44
First Segment: begins at lift off and ends when the landing gear is fully retracted. The climb requirement in first segment is a positive gradient, out of ground effect, for two engine aircraft and 0.3% for three engine aircraft. The rotation speed, Vr, must be selected so that V2 is achieved by the time the aircraft reaches 35 feet in the air.
Second Segment: begins at the end of first segment and is continued to not less than 400 feet above the airport elevation. The climb requirement in second segment is 2.4% gradient for two engine aircraft and 2.7% for three engine aircraft. Second segment is usually, but not always the most limiting of the segments within the takeoff flight path.
Third Segment: begins at the end of second segment and ends when the aircraft reaches the speed for final segment. While third segment is usually flown in level flight, the available gradient must be at least equal to that required in final segment. During third segment the high lift devices are retracted.
Final Segment: begins when the aircraft reaches the final segment speed and ends when the aircraft reaches 1500 feet above the airport elevation. The climb requirement in final segment is 1.2% gradient for two engine aircraft and 1.5% for three engine aircraft. At the beginning of final segment, the power is reduced to maximum continuous. Each segment must be flown at a constant power setting and the end of the acceleration segment is often coincident with the end of the five minute limitation on Takeoff thrust.
............but I could be wrong:ok:
Thoroughly Nice Bloke...
7th Jul 2003, 02:42
7th Jul 2003, 21:02
I believe under JAR it is as follows:
Extends from lift off to gear up point. Thrust maintained at T/O thrust setting. From lift off until gear is retracted (end of first segment), the engine out climb gradient must be positive for a twin engined aeroplane and at least 0.5% for a four engined aeroplane.
Begins at gear up point and continues to level off height. During engine out second segment, the thrust is maintained at T/O thrust setting and speed = V2. Engine out climb capability at the start of the 2nd segment is 2.4% fora twin and 3% for a 4 engined aeroplane. This tends to be the most limiting of all the climb gradients.
Begins at initiation of level flight acceleration. This is level off height. Level off height is determined by:
- FAR min of 400ft = min level off height.
- Take off thrust time limits (5 mins in UK) = Max level off height.
- Extended V2 climb.
Climb gradient limits are 1.2% for 2 eng and 1.7% for 4 eng a/c.
This is the flaps up climb segment. Begins when flaps are up and aeroplane has accelerated to final climb speed. Thrust set to Max Continuous. Gradient limits are, 1.2% for 2 eng and 1.7% for 4 eng a/c. This segment is complete when all obstacles are cleared or the a/c has reached a min of 1500ft AAL.
Fokkerjet (and eff oh) have provided detailed and precise explanations.
Their descriptions however are true only for turbojet/turbofan powered aircraft that were certificated under FAR25 or CAR4b.
Turbopropellor and piston powered aircraft that were certificated under CAR4b are a slightly different story. For example, for these aircraft, V2 (takeoff safety speed) was achieved on the runway, prior to liftoff. In addition, the runway length requirements were scheduled with a 50 foot height requirement rather than 35 feet.
8th Jul 2003, 08:08
Everybody agrees about when the 1st segment begins but I am not that sure because it depends on the book you look for: " first segment compromise the interval from the end of the TOD (the point which the aircraft reaches 35 feet) to the point ......"
JAR/FAR 25.115 (a): "The TO flight path begins at 35 ft above the takeoff surface at the end of the takeoff distance".
JAR/FAR 25.121: " The takeoff flight path can be divided into several segments"
JAR/FAR 25.113 "takeoff distance: distance covered from brake release to a point at wich the aircraft is at 35 feet above the takeoff surface"
Can the distance between lift off and 35 belongs simultaneously to the takeoff distance and the take off flight path?
9th Jul 2003, 20:07
TOD finishes at the screen height (35ft). If the gear is
(a) up by this point, then there is no first segment.
(b) not up by this point, then the first segment is the distance taken during the remaining part of the retraction sequence
12th Aug 2005, 17:48
I'm confused folks. After all that has been espoused in this thread I'm still not sure.
When exactly does the beginning of the first segment actually start; at lift off e.g. VLo or 35 ft?
I have pre JAR ATPL notes which refer to the 1st segment beginning at VLo which seems to be based on FAR Part 25 (2-1-65) presumably (US FAR)
I also have the Cathay/Emirates/Ace the tech interview... all indicating the beginning of the 1st segment as 'From 35 ft height....'
Which is correct? Is it the case of JAR/FAA vs UK CAR??
12th Aug 2005, 22:00
EASA CS 25.115 Take-off flight path
(a)The take-off flight path must be considered to begin 11m (35ft) above the take-off surface at the end of the take-off distance determined in accordance with CS 25.113 (a) or (b) as appropriate for the runway surface condition.
Hope that helps.
Don't have the old JAR regs with me as my jet was certified with EASA.
12th Aug 2005, 23:25
Another comment one of us probably should have made before was that the 5 minute limitation for TO thrust is general but not wholly applicable. Some aircraft are certificated for alternative periods, typically 10 minutes. One I can recall was for some DC9 models (KLM ?) to get considerable improvements in the obstacle analysis by permitting the third segment to be pushed higher. IPEC, in Australia, used this O/S basis to get an airworthiness concession to use the 10 minute rating in an emergency without spending the big dollars necessary to get the performance data.
typically 10 minutes
J_T, the 10 minute takeoff limitation is an airline option for most new Boeings. We will also have it on the Embraer170.
Dont forget, 35 feet is for dry ruways, 15 feet for wet...
Are there any aircraft still operating under CAR4b?
13th Aug 2005, 08:34
kanger, the way i see it segment one starts from 35 feet (35 feet above the end of reference 0)
13th Aug 2005, 09:46
No_Speed_Restriction & Co,
I'll have to store away these pre JAR ATPL notes. They are just confusing... :D
A few that come to mind, Mutt are...
DC-6A/B freighters, and F-27's.
In addition, regarding aircraft performance (not screen height), with some varients of the Lockheed TriStar, the V2 speed is normally obtained while the aircraft is still in the rotation, on the runway, as the V1/Vr speeds are very close to V2, IE: within four knots or so.
The -100 that I am flying now, is a perfect example, at heavy weights.
The -200's, -250's and -500's are different however, as these aircraft have a lot more thrust available.
I have had the distinct pleasure of flying the 1649A, L188 and the L1011, and the performance of each was unsurpassed...for its day.
14th Aug 2005, 13:41
A new set of words on the same subject, primarily aimed at Kanger's confusion.
There are 4 clearly defined segments following the Takeoff, 1st, 2nd, 3rd, and 4th.
The Takeoff Distance (TOD) ends at a 35 ft 'screen height' above the runway (15ft for Wet runway, 50 ft if a turning manoeuvre is involved), and at V2 speed. At the end of the TOD, the Gear is assumed to be DOWN.
The 1st Segment begins at the end of the TOD, and ends when the Gear is UP. Speed remains at V2.
The 2nd Segment begins at the end of the 1st Segment with the Gear UP, Power / Thrust at Takeoff, and the aircraft in the Takeoff configuration. The 2nd segment ends at 400 ft above Aerodrome Elevation, or higher if required for obstacle clearance. The 2nd segment is flown at V2, or limited to V2 plus an allowed margin.
The 3rd Segment begins at the end of the 2nd Segment climb with the Gear UP, Power / Thrust at Takeoff, and the aircraft in the Takeoff configuration. The 3rd segment is a level accelerating segment, where Flaps / Slats are retracted, and the aircraft accelerated to the Final Takeoff (Clean) speed, and Power / Thrust then reduced to Maximum Continuous.
The 4th Segment begins at the end of the 3rd Segment level acceleration segment with the aircraft in the Clean configuration, and Maximum Continuous Power / Thrust set. The 4th segment ends at 1500 ft, or higher if required for obstacle clearance.
Variation (1) - It is possible that the gear is retracted by the time that the aircraft has reached 'screen height' at the end of the Takeoff, in which case no 1st segment exists. This is not a typical case, but does exist.
Variation (2) - It is possible that the time limit for Takeoff thrust may be reached before the 3rd segment is complete, although this is becoming rare with increasing availability of a 10 minute limit. It is then necessary to re-evaluate whether the aircraft has the performance capability to accomplish the acceleration with MCT, and re-assess the length of the 3rd segment . Manufacturer's data is rarely available for this, necessitating an alternative steeper 2nd segment climb, higher than dictated by obstacles, to reach the 3rd segment in a shorter time, leaving sufficient Takeoff Power / Thrust availability to accomplish the 3rd segment.
All of this has been said, I hope that words from a different slant may be of use to Kanger.
Sec. 25.121 Climb: One-engine-inoperative.
(a) Takeoff; landing gear extended. In the critical takeoff configuration existing along the flight path (between the points at which the airplane reaches VLOF and at which the landing gear is fully retracted) and in the configuration used in Sec. 25.111 but without ground effect, the steady gradient of climb must be positive for two-engine airplanes, and not less than 0.3 percent for three-engine airplanes or 0.5 percent for four-engine airplanes, at VLOF and with--
(1) The critical engine inoperative and the remaining engines at the power or thrust available when retraction of the landing gear is begun in accordance with Sec. 25.111 unless there is a more critical power operating condition existing later along the flight path but before the point at which the landing gear is fully retracted; and
(2) The weight equal to the weight existing when retraction of the landing gear is begun, determined under Sec. 25.111.
(b) Takeoff; landing gear retracted. In the takeoff configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in Sec. 25.111 but without ground effect, the steady gradient of climb may not be less than 2.4 percent for two-engine airplanes, 2.7 percent for three-engine airplanes, and 3.0 percent for four engine airplanes, at V2 and with--
(1) The critical engine inoperative, the remaining engines at the takeoff power or thrust available at the time the landing gear is fully retracted, determined under Sec. 25.111, unless there is a more critical power operating condition existing later along the flight path but before the point where the airplane reaches a height of 400 feet above the takeoff surface; and
(2) The weight equal to the weight existing when the airplane's landing gear is fully retracted, determined under Sec. 25.111.
(c) Final takeoff. In the en route configuration at the end of the takeoff path determined in accordance with Sec. 25.111, the steady gradient of climb may not be less than 1.2 percent for two-engine airplanes, 1.5 percent for three-engine airplanes, and 1.7 percent for four-engine airplanes, at not less than 1.25 VS and with--
(1) The critical engine inoperative and the remaining engines at the available maximum continuous power or thrust; and
(2) The weight equal to the weight existing at the end of the takeoff path, determined under Sec. 25.111.
(d) Approach. In the approach configuration corresponding to the normal all-engines-operating procedure in which VS for this configuration does not exceed 110 percent of the VS for the related landing configuration, the steady gradient of climb may not be less than 2.1 percent for two-engine airplanes, 2.4 percent for three-engine airplanes, and 2.7 percent for four engine airplanes, with--
(1) The critical engine inoperative, the remaining engines at the go-around power or thrust setting;
(2) The maximum landing weight; and
(3) A climb speed established in connection with normal landing procedures, but not exceeding 1.5 VS.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-84, 60 FR 30749, June 9, 1995$