One more head bang against the cultural brick wall; or an alternative view for the undecided, or just a personal view?
Approach procedure design, to a certain extent, considers the inaccuracies and variables of a range of pilot skills when flying NPAs; very little in our industry is precise and many operations are based on probabilities. A skilled crew should be able to calculate the required vertical rate and timing with sufficient accuracy to arrive at, or close enough to the visual descent point (VDP) when using a constant descent angle stabilized approach. The risks due to any position error at MDA, whether continuing to land or go around, should be less than the risks involved with attempting a late descent from level flight or ducking under before VDP: - and for those who think otherwise, there is no requirement to fly level until MAP. The majority of these risks are due to human inadequacies or failings, notably the failure to follow procedures by attempting a steep approach after VDP, or accepting a high landing airspeed or unstable approach due to a late configuration change.
For those crews who think dive and drive (D&D) is easier; is easier an alternative description for lazy or lacking in those airmanship skills required for NPAs? If you are not very good at something (time / vertical speed) then practice should improve it.
Just because a national authority (or their representative) reportedly requires level flight does not mean that it is the best option. Our industry is still evolving; we still have to incorporate many of the hard learnt lessons from other’s accidents.
I prefer to have the lowest workload when flying a NPA. With D&D or ‘stepping down’ there is additional workload with altitude selection, power adjustment, and aircraft trim (trim changes due to changes in power, configuration, and airspeed) and, although use of autos can reduce this workload, the monitoring tasks in a dynamic situation are more complex. Alternatively CANPA gives a stable and consistent basis for monitoring during all NPAs. The aircraft should be stable in airspeed, vertical speed, pitch, and configuration. You can check that the flight path is at or is above each step-down altitude during the descent. There is reduction in the number of altitude captures; for every altitude change there is the risk of an alt bust, for every selection of the MCP there is opportunity for error, hence avoid the step downs and level off at MDA.
Alternative landing configurations, procedures, or approach speeds lead to inconsistencies, each with opportunity for error or requiring higher mental workload. The process of choosing which landing option to use, which configuration, speed, etc requires knowledge and experience. Not all crews have the opportunity to gain these attributes, and even less time to practice them. Thus the industry needs to look for simplicity through consistency and familiarity.
Approach timing is important, but timing or the available time is important in assessing the visual situation leading to a decision. Flight with an intermediate configuration often requires a higher approach speed which decreases assessment time. A level flight path gives a higher nose attitude than when descending, this reduces the available visual segment that could be seen on which a decision is to be made. Although the decision to land may ultimately be judged on what is seen at the far point of the visual segment (lights / runway), the ability to decide also depends on how long something has been seen. In low visibility the first point of contact is at the ‘near point’, a function of the cockpit cutoff angle and pitch attitude, the earlier the first point of contact the longer time there is to assess the aircraft position and flight path with respect to terrain etc. Thus use of the optimum landing configuration and a continuous descent improves the likelihood of seeing sufficient visual reference and maximizes the time for a quality decision.
There may not be a clear cut solution to the problems represented by the differences in culture seen throughout this thread, but here are some thoughts:
Avoid NPAs: National authorities / Airports take action. Operators use FMS if capable.
Use charts with range altitude checks; if the procedure has none then operators supply a crib sheet with details or at least tables for calculating timing / vertical speed. (The more astute may decline to operate to a runway in those circumstances).
Minimize the opportunity for error; publish and use consistent procedures, avoid configuration and speed changes. Report all ambiguities, both to your organisation and to the authority.
Strengthen error detection procedures; publish the required crew calls (and the limits of deviation) for non stabilized approaches.
Practice the error recovery techniques: go around.
Do not rush; maximize the time available for monitoring, checking, and deciding.
Report the violators; CFIT accidents are not Captain’s accidents, they are crew accidents, you are all in the same aircraft.