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 ]