Two Hooked on the line
I'm sure that Mutt will be along anytime soon, now ...
Two separate obstacles may well have caused these two gradients
OS' point about hidden/multiple obstacles is very important.. especially when it comes to fitting in the third segment.
For the simplifying calculations referred to, if the intersection of more than two slopes suggests that we have identified an obstacle, that makes life a tad easier (but it doesn't guarantee that the lowest slope is not simultaneously limited by another, more distant, obstacle). If not, there is no way we can infer obstacle triplets without relevant charts or, as sometimes is done, going out to the aerodrome and having a looksee.
The polygon, to which OS refers, has to be treated as a series of rock hard intersecting surfaces above which we need to keep our puny aeroplane .. lest we be smitten and not see retirement.
Is this complex ? .. not really, but you do need to be reasonably tidy with housework and detail.
Sorry..I have to ask..why do you need this stuff?????
Ah .. absolutely the most important question !
Background ...
(a) If your wing falls off - you die - mostly.
As pilots we understand a little about a bunch of limit speeds and g-loads. Generally, most of us respect these (and all the other important things) and get to retire and go sailing.
(b) etc... etc...
(c) If you manage a CFIT (which includes combining OEI with wrong takeoff calculations) - you die - mostly.
As pilots, most of us know a lot less about performance than the stick and rudder stuff (and some would opine that the new breed know precious little about the latter as well).
It appears reasonable to me that we should know (at least) the basics about all the various things which are hiding out there ... just waiting to kill us off ?
I mean..if it is really important why is it not provided to you
Is it important ? .. see (c), above. By my simple life standards, if it is reasonably likely to kill me, I consider it important.
Is it provided ? .. certainly by the reputable operators (although, for some, only for a restricted scenario).
However, many operations give, at best, only lip service to proper takeoff calculations and, for others, the pilot is where it is all at.
The old Perf A studies gave the student a reasonable basic grounding in the discipline .. but that only covered a smallish subset of the pilot fraternity.
...or is my 30 years out of GA protectected by a major airline showing
I think so ....