Old 29th May 2020, 16:09
  #28 (permalink)  
oggers
 
Join Date: Nov 2005
Location: Zulu Time Zone
Posts: 717
Originally Posted by AC103 View Post
To be fair I think I very clearly spelt out the operational considerations around descent with comparisons in post #21
Ok, so the quote below is what we are talking about from post 21:

With regards to the problem taking care of its self, this issue is that if an aircraft design increases its MTOW on paper and then artificially reduce their Vno as their structures are not able to comply with the gust penetration requirements this is an indication of a weaker than required air frame which becomes relevant in descent and this is where it gets more interesting.

The Archer III POH specifies a Fuel, Time, Distance to Descend chart based on an engine RPM (2500) and KIAS (122) which puts it an additional 3 knots under Vno, limiting the descent rate to only ~450fpm whilst keeping the engine warm.
This configuration is mentioned again in the Descent subsection of Normal Procedures in reference to carb ice. (The Archer III has a cooler air pick up than previous 4cyl PA-28s) so its descent profiles now start to look limited by the low Vno.
These Fuel, Time, Distance to Descend charts are published for the later Pipers (Seminole, Malibu, Warrior 161s, Archer 181s etc) and not published by the other manufactures singles mentioned above including popular IFR trainers like the DA-40 and DA-42 where these tables would be more expected.
The key point in there is where you say "descent profiles now start to look limited by Vno". Would you prefer the recommended descent speed was higher than Vno or where exactly? The structure does comply with the gust penetration requirements. You are reading too much into this. The recommended descent profile is 'nice to have'. It is not a limitation. It is not even an unduly limiting recommendation because it turns out to be one knot faster than a 75% cruise at 4000' DA (according to Fig 5-21 of the POH).

The majority of other manufactures including Piper for its other aircraft chose to design around the more onerous interpretation that is not in direct conflict with later advice from the FAA and provides a more useful and safer operational envelope.. So this is absolutely not an objective fact
The aircraft is certified. That is the fact. Its flight envelope provides the same safety factor of 1.5 between limit loads and ultimate loads as every other certified aircraft.

The AC is: "not mandatory.....not a regulation.....not the only means of compliance". Other manufacturers have complied with certification by using the other of two alternative and equally valid criteria in the regulations. The reg has since been reduced to something vague by the new FAA part 23, but the original certification basis is still extant in EASA land where:

"(3) VC need not be more than 09 VH at sea level."


This aircraft is fully compliant. There is no "deal with the FAA here to allow increases in gross weight for the Cherokees without complying with the Vno requirements?". because it complies with the pre-existing foreign regs too. You are barking up the wrong tree.
oggers is offline