Originally Posted by
Minos
Ouch, my head spins. So if I understand correctly your answer John, Mokulele and the like to not abide to the 60% rule because their C208 is just 9-seat?
As a result, for those 9-seaters, as long as the POH says that you can land within X feet, then an X+1 ft runway is fine (although not necessarily wise). Am I correct?
Minos
The applicability of the "60% rule" has been spelled out, and as you quoted, that landing rule applies to aircraft with 10 seats or more. The Caravan is limited to 9 passenger seats because of its type certification under 14 CFR Part 23. It is allowed 2 pilot seats with nine passenger seats; if an operator places a passenger in the right front seat, one of the nine passenger seats must remain unoccupied. This applies in the US, based on the type certification of the airplane. Caravans are also certified for up to 14 passengers in certain configurations, but not under Part 135, and a waiver is applicable to the original certification, allowing it to operate with more than 9 passenger seats. This would be more appropriate to a Grand Caravan in a skydiving configuration. Outside the US, countries may apply other limitations, as they are not bound by the US regulation, Part 23, nor the limits it prescribes. (Other countries do look at the certification for the airplane, and generally follow the same standard, but the Caravan manual indicates a waiver to Part 23 chiefly because outside the US it does get operated with more seats.
That said, the same landing and takeoff criteria apply to other single engine small airplanes that are certificated with a seating capacity of less than 10 passenger seats.
Remember that the "60% rule" is a flight planning and dispatch rule, not a performance rule at the time of landing. In other words, for those circumstances in which it does apply (turbine, transport category, large airplane, commuter, 10 passenger or more, etc), the operator must be able to determine prior to dispatching the flight, that the airplane will be at a weight that will allow it to land in 60% of a dry runway (or 1.15x that distance if wet, or 70 or 80% for eligible on-demand operators). That's planning. When the airplane arrives, it doesn't have to be stopped in 60% of the runway...the "60% rule" is a planning and dispatch requirement, not an operational requirement. It may end up taking the whole runway on landing; it's no longer bound by a requirement to actually land in 60% of the runway. The operator need only show that the published performance data shows that it is capable, at the planned arrival weight and conditions.
Part 23 single engine airplanes do not have the same performance data as other categories of airplane; Part 23 certification standards aren't as stringent on what must be provided for performance or planning. FAA Order 8900.1 provides an enlightening note about the difference in performance data and standards:
https://drs.faa.gov/browse/excelExte...230153703.0001
B. Source of Data.
B. Source of Data.
1) When possible, the operational landing distance data used is advisory data based on the recommendations of the current edition of AC 25-32, Landing Performance Data for Time-of-Arrival Landing Performance Assessments. This data may be provided by the manufacturer or developed by a performance data provider.2) If advisory data for a landing distance assessment at time of arrival is not available from the manufacturer, performance provider data may be used. If performance provider data is not available, the Landing Distance Factors (LDF) from Table 4-11, Landing Distance Factors, may be used. To find the LDR, multiply the certificated (AFM, i.e. dry, unfactored) landing distance by the applicable LDF in Table 4-11 for the runway conditions existing at the time of arrival. If the AFM landing distances are presented as factored landing distances, then that data must be adjusted to remove the applicable preflight factors applied to that data. The LDFs given in Table 4-11 include a 15 percent safety margin; an air distance representative of normal operational practices; a reasonable accounting for temperature; the effect of increased approach speed, reduced wheel braking, and thrust usage (reverse or not); and the additional effect of reduced wheel braking capability on altitude and wind distance adjustment.
3) Currently, the Small Airplane Standards Branch (AIR-690) does not plan to provide aircraft manufacturers with advisory information similar to AC 25-32. In the absence of guidance to manufacturers of part 23 aircraft, operational landing distance data may be based on the recommendations of AC 25-32. This data may be provided by the manufacturer or developed by a performance data provider if manufacturer data is not available. In the absence of guidance to part 23 aircraft manufacturers, the manufacturer or data provider may consider the recommendations in AC 25-32 when creating data for a time-of-arrival assessment. Manufacturer-provided guidance on the use of existing data with the runway condition codes (RwyCC) must be used when available
Note that the "60% rule" is actually a weight limitation; a weight that allows the airplane to get stopped, for planning purposes, in 60% of the available landing distance. For a single engine small airplane certificated under Part 23, the weight must also be limited to be a value that allows landing in the available runway.
It's worth noting that while a multi engine airplane has a host of other requirements, such as segmented takeoff and climb performance, accelerate-stop and accelerate-go, and the capability of meeting climb gradient criteria with an engine shut down, obviously this isn't all applicable to light single engine airplanes. Imagine having to calculate the climb gradient with an engine shut down, in a Cessna Caravan or Cessna 207. Obviously that's going to be negative numbers. Further, the performance limits for Part 23 certified aircraft are not as stringent as those applicable to Part 25 airplanes, nor is the performance data as detailed, or in many cases, even available.