Who could expand upon
John_T's superlative summary, just about the best precis I've seen on this topic!
Mutt speaks the truth, as always, even if the thrust is constant throughout 2nd segment, increasing TAS will steadily reduce the Climb Gradient. The technique that I use is to apply the mid Pressure Height between end of 1st Segment and Minimum Acceleration Altitude, thus, Initial Instantaneous Gradient will slightly exceed that required, Final Instantaneous Gradient will be slightly less, but the Mean Gradient should equal that required. It introduces a little conservatism between beginning and end of 2nd Segment.
To give a short answer to a question which
Mutt has asked of other P/E's techniques in applying nominal higher Acceleration Altitudes (e.g. 1000 ft) than the MAA,
REQUIRED Gradient is assured until MAA, and a lesser gradient accepted for further climb to the increased 'nominal' Acceleration Altitude (because it's not needed), but ensuring significantly improved vertical obstacle clearance in the 3rd segment. No significant performance penalty should result, excepting the possibility of hitting the 5 minute Takeoff thrust time limit. Most modern aircraft now have a 10 minute limit, so even this is not a real problem.
MarkerInbound, what you say is true, but the reality is significantly better than the minimum certification requirement. Typical Deltas betweem 1st and 2nd Segment Gradients are rarely in excess of 1% (0.9% is the worst that I've worked with), thus, if the aircraft can achieve a 2.4% Gross Gradient in the 2nd Segment (minimum requirement), it's reasonable to assume that 1.4% should be achievable in the 1st Segment. Even if you degrade this by the arbitrary 0.8% Gross Vs Net, we should see no worse than 0.6% in 1st Segment. Hardly rocket performance, but a darned sight better than the nominal "positive" climb gradient. I think that
Galaxyflyer once stated a worse than 1% delta, but this is the exception rather than the rule.
Regards,
Old Smokey