Old 23rd May 2020, 22:47
  #23 (permalink)  
AC103
 
Join Date: Jul 2015
Location: NZ
Posts: 45
Originally Posted by djpil View Post
Perhaps Francis Donaldson could fill in the history and perhaps explain why the AC mangles the text of the rule instead of changing the rule…
…The Aviat Husky series is one that I am very familiar with. The current model A-1C has W/S of 12 so 33 √ W/S = 114 kts but Vc used in design and Vno is 103 kts…
…I like the bit in AC 21-19A about "For airplanes where VA>VS√n, the pilot would have to check the maneuver; otherwise the airplane would exceed the limit load factor."... Perhaps the subject of another thread.
Indeed as you say the VLA also provides the updated guidance on Vc. Adding the context.

You are not constrained to use these minimum values. Indeed, if your aircraft has high performance in terms of a high cruising speed, the value of Vc would be much greater than the minimum. Additionally:

It is recommended that Vc should not be less the 0.9 Vh
Forgive me if I am stating the obvious but as I understand it updating a rule is slow, onerous and expensive in comparison to issuing letters of interpretation https://www.faa.gov/about/office_org...terpretations/ or updating ACs. (NPRM, comments, replies to comments etc.) Here is a good example. The wording of Part 43 Appendix A and AC43-12A that conflict with the FAR 1.1 definition of preventative maintenance have still not been updated 11 years (ATOW) after the Coleal Inerpretation from 2009.

43 Appendix A: On the list of 32 preventive maintenance items.
(c) Preventive maintenance. Preventive maintenance is limited to the following work, provided it does not involve complex assembly operations:
AC43-12A:
If a task or maintenance function does not appear in the list, it is not preventive maintenance.
Coleal Interpretation: (David Coleal from Lear asking if crews are allowed to check the ~200psi tire pressures on a Lear 60 required daily under an Airworthiness Limitation)
https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/data/interps/2009/Coleal%20-%20(2009)%20Legal%20Interpretation.pd

Yes, crews can check the tire pressure under Part 91
AND
Even though the introductory text of subparagraph (c) states that "preventive maintenance is limited to the following work....", in view of the broader definition of preventive maintenance in section1.1, we believe that such limitation is not controlling.
AND
we also believe that the… sentence in Advisory Circular 43-12A, Preventive Maintenance … is overly restrictive
AND
the lists are better viewed as examples of the tasks in each category-they cannot be considered all-inclusive
AND
There are, no doubt, many "simple or minor preservation operations [tasks]" and many" replacement of small standard parts not involving complex assembly operations" performed daily, especially on small general aviation aircraft, that the agency would consider to be preventive maintenance, though they are not included in the 32 listed items. It is our understanding that Flight Standards' Aircraft Maintenance Division is planning to clarify this issue in a future revision to the AC.
So owners/operators have more scope to undertake work of comparable ease, complexity and risk as those on the list and make log book entries in accordance with CFR 43.9 with the date, the description of the work performed and signed with their pilot’s certificate number. So long, of course, as they follow the acceptable methods, techniques and practices out lined in CFR 43.13 eg. they have the relevant AMM, IPC, SB’s and tools at hand and the work is performed to a standard at least equal to its original or properly altered condition (with regard to aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness) and ‘should’ (though not required for pilots even though it is required under Part 66 for mechanics) have been supervised for the first time that they perform the task.

Yet the regs and the AC still say they cannot to this day.



Thanks for the Husky

You are totally on the right track with Va. Yes probably for another thread. It may well have already been flogged here due to the AA587 accident.

I sure would love to talk to a Piper engineer to understand which structure they believe would not be able to withstand loads at proper Vc min for its wing loading.

AC103 is offline