Originally Posted by
Zeke
To share the same TCDS, they must have the same fundamental airframe and systems, they share the same fundamental design philosophy, otherwise certification authorities would demand full recertification.
To suggest that this is not the case on the 737 and 747 is false. The fundamental systems and airframe philosophy has changed little for those types, the fundamentals remain the same, e.g. the overhead panel on the 737 has not changed since the 1960s, people are still turning off the hydraulics in flight when they mean the anti-ice 40 years later. The 737-300 retains 80% airframe spares commonality with the 737-200.
The report does not say that at all, it just splits them up when they were introduced in service, it does not give a rational for doing so.
Even with this statement the grouping was skewed to suit Boeing, as the 747-300 entered service after the 757 and 767, and at about the same time as the A310. The 737-300, 757, 767, A300-600, A310 all entered service within a year or two of the 747-300.
To say that the groupings are based only on EIS is patently false.
The 757 and 767 introduced two crew operation with much more flight deck automation even though they entered service about the same time as the 747-300. The 747-300 flight deck was still a three crew operation and is essentially the same as the 747-100/200. The 747-400 flight deck introduced new levels of automation and allowed the airplane to go to a two crew flight deck. Note that this happened without requiring a new TCDS for the 747.
Note that the same distinction was made for the A300 versus the A300-600. The fundamental technical changes that went in to the revisions of this airplane that allowed it to go from a three crew to a two crew flight deck are recognized by the groupings.
In addition to airplane technical level, the groupings account for the operational environment changes that have taken place over time. Things like pilot skill sets and attributes and airway/airport infrastructure were far different in the mid-60's compared to the mid-80's and they have continued to advance to the present day.
The groupings are a fair attempt to represent the total environment present during the design and operation of the airplanes shown. While no set of groupings can be perfect, I doubt that Airbus would disagree with these or the statistical story they tell.