First Segment Climb

[Richie]

I've been going nuts trying to get a good definition for First Segment Climb. Here's what I've come up with so far.
Any comments or help would be greatly appreciated.

FIRST SEGMENT Definition Variations: (23.59, 25.111, 25.115, 25.121, AC 25-7A)

1. First segment ENDS when the gear is fully retracted, at some altitude higher than 35 feet at a speed of V2.

2. The aircraft is only required to demonstrate a positive rate of climb after liftoff and during this segment.

3. First Segment Definition Variations:
a. Some Aircraft Flight Manuals show first segment BEGINNING at brake release and ENDING at a point after takeoff (more than 35 feet AGL) where the gear has fully retracted at V2 speed.
b. Other Aircraft Flight Manuals show 35 feet AGL as the START of the first segment climb calling this “REFERENCE ZERO”. In this case, first segment climb BEGINS at 35 feet above the runway with the gear still down (or in transition), the flaps still set for takeoff, and the remaining engine(s) at max takeoff power. Positive rate of climb is established and the gear handle is raised. Using this criteria, first segment is the time it takes for the gear to fully retract and the gear doors to close. First segment ENDS when the gear is fully retracted at V2 speed.
c. AC 25-7A — “Flight Test Guide for Certification of Transport Category Airplanes” illustrates first segment BEGINNING at liftoff and ENDING when gear retraction is complete. In this case the ground roll is called “GROUND ROLL” (what an interesting concept!).

4. So… apparently you can START calling it FIRST segment pretty much anywhere you like, as long as it ENDS with the gear fully retracted at some point more than 35 feet AGL and the speed is at V2 (start of SECOND segment).

Thanks for any comments.

 

[avbug]

First segment climb begins liftoff, and continues until the landing gear is retraced. The climb performance for this period is stricly positive rate, with no value or gradient established.

EXCEPT...the aircraft must meet the threshold value of 35' above the takeoff elevation prior to reaching the end of the runway. Therefore, rate and gradient is dependent upon available runway and ambient conditions.

First segment responsibility is stricly positive rate of climb, measured from liftoff following engine failure at Vef. (Applicable to two engine airplanes: not less than 0.3 percent for three engine airplanes or 0.5 percent for four engine airplanes). For test purposes, the aircraft is rotated at Vr at the rate of 3.5 degrees/second to the 10 degree pitch up (command bars). The airplane comes off the ground at Vlof, a positive rateof climb is established, and gear retraced.

First segment ends when the gear is in the wells, and second segment climb performance begins at this point.

V2 speed must be achieved prior to or by 35' above the runway surface, but this does not impact climb requirements (which are positive rate, only). V2 is maintained to at least 400' above runway elevation for 2nd segment climb measurements.

You may be confusing takeoff path, with climb segments. A climb segment doesn't begin until the airplane is climbing. The parts of 14 CFR 25 you identified (25.111, 25.115) apply to path and provide only part of the information you require. You identified 25.121: 25.121(a) provides first segment climb details.

Takeoff flight path is measured starting at 35' above runway elevation. However, first segment climb begins before that, starting at liftoff, and continuing until the gear retraction is complete.