Climb segments

[Groundbased]

Hi all,

Could somebody give me an explanation of climb segments?,
are they laid down by aircraft type or calculated depending on conditions such as temp, field elevation etc?

Or is it an SOP thing? I assume that flying particular SID's can impact the climb rates you can or have to achieve. I've heard of penalties being applied in the second segment due to certain MEL items for example, but surely the penalty would apply throughout the climb?

Anyway, as you can see I haven't a clue, but would like to understand.

Cheers,

GB

[john_tullamarine]

A heavy, similar to a lightie, has to reconfigure from takeoff to final climb configuration. To make the obstacle calculations reasonably predictable and repeatable, the aircraft is presumed to be flown through several specific reconfiguration segments of the takeoff. The calculations are based on one engine failing just prior to V1 during the takeoff. It is presumed that the AEO case is constrained to remain above the OEI profile so it is not addressed separately for considerations of RTOW.

(a) first segment from the end of TODR until the gear has finished retracting. This segment may, or may not, occur depending on the aircraft and, indeed, if it is present, will generally vary according to ambient conditions and TOW

(b) second segment from either the end of TODR or first segment, as applicable, until a "safe height" (minimum 400ft above the aerodrome height) is achieved. Speed nominally V2, T/O thrust.

(c) third segment, nominally level, during which the aircraft accelerates to the flaps up climb speed. Flaps are retracted according to some predetermined schedule. T/O thrust until the end of the segment when a defined maximum OEI thrust level is set.

(d) fourth segment, climbing at a suitable nil flap speed to 1500 ft.

(e) sometimes a fifth segment to accelerate to a final en-route climb speed.

The minimum climb capability in each segment is defined in the design standards and varies according to the number of engines. References to WAT limits (maximum Weight for Altitude and Temperature) are to these minimum climb capabilities.

RTOW may need to be reduced below the WAT limit to permit an improved climb capability to achieve the minimum clearance required between the net flight path (a reasonably expected OEI flight path less a fudge factor) and known obstacles. Considerations such as OAT, elevation, wind, etc come into play in this.

SIDs are promulgated without regard to engine failure. If you wish to follow a SID, then you need to make sure that you can make good the required gradients OEI.

If an MEL weight penalty is prescribed for, say, the second segment, then you may presume that the prescribed penalty covers all segments, ie it would be the most restrictive of those penalties which might be appropriate for the various segments. As such a penalty would be a weight reduction it, quite clearly, is going to apply for the entire takeoff sequence.