To summarise..
It seems that determining how my company RTOW charts have been devised is one matter, as is the identification of any other obstacles beyond the surveyed area.
And that the 1.2% gross climb capability required in the 3rd segment (normally used to accelerate) is factored by the regs to equate to an increased distance allowed/required for acceleration to final climb speed.
And...this equates to an acceleration of .07 knots per second (CliveL above).
Given all that, I can extrapolate the certification performance required in terms of distance and time, in all 4 segments. For the sake of the exercise, for fellow geeks, and to confirm that I have got it right, here we go.
I am assuming a V2 of 122 knots and final takeoff climb speed of 132 knots, based on a DHC8-300 at MTOW (although I don't have the book figures with me at the moment).
Segment Two
Gradient - 1.6% net required
Speed - 122 knots
Rate of Climb - 195 fpm
Time to reach 400' - 2.05 minutes
Distance to reach 400' - 4.16nm
Segment Three
Gradient - 1.2% gross
Start speed - 122 knots
Finish speed - 132 knots
Avg speed - 127 knots
Acceleration - .07 knots/sec
Time to accelerate - 2.4 minutes
Distance covered - 5.04nm
So, to reach the start of the 4th segment, time required is a total of 4.43 minutes (within the 5 minutes available at max power/MTOP) and the distance covered is 9.21nm (at 17.06km this is 2km beyond the normal 15km surveyed area).
And to complete the numbers:
Segment Four
Gradient 0.4% net
Rate of Climb - 53 fpm
Time to climb another 1100' (to 1500' AGL) - 20.8 minutes
Distance covered in that time - 45.8nm
Grand Total to end of 4th segment
Time - 25.2 minutes
Distance - 55.04nm / 102 km
What I find interesting is that, to consider just one aerodrome that we visit, there is an MSA of 3,000' and we use an acceleration altitude of 1,700' (which is 400 and something feet AGL in this case).
Based on the numbers above there is no way we will reach 3,000' within the 25nm of the MSA.
Which raises another question: upon the loss of one engine at V1, at this airport, based on these numbers, if the pilot was continuing and not returning to the departure aerodrome (for whatever reasons), then he/she would presumably need to manoeuvre within the MSA until either the MSA or LSALT was reached. Which would entail very small bank angles to preserve any of that 53 fpm available.
And that seems to me a case for not departing that aeordrome unless I intended to return to it (in the case of a failure at V1), and not proceed.
Is that how I should look at it?