Skycatcher Down in KS

FAA didn't come up with the 1320 pound limit. That's defined in the ASTM Standards, around which the FAA Sport Pilot Rule was written.

No. The consensus standards for the design standards of the aircraft were assembled by an ASTM committee, but the basic definition of an LSA (including weight limit) is from the FAA itself. See the writeup starting on page 66 of....

http://www.wanttaja.com/LSA_final.pdf

Ron Wanttaja
 
No. The consensus standards for the design standards of the aircraft were assembled by an ASTM committee, but the basic definition of an LSA (including weight limit) is from the FAA itself. See the writeup starting on page 66 of....

http://www.wanttaja.com/LSA_final.pdf

Ron Wanttaja

Ah, okay. I stand corrected.

Rich
 
Interesting that you mention the C140. Right when the LSA rules were developed, the Cessna 120/140 association got an STC created to REDUCE the gross of those aircraft from 1450 to 1320. After getting the STC, the Association tried to get the FAA to recognize the newly STC'd aircraft as an LSA. Not only did the FAA reject that request, but (partially because of this attempt) they then specificlly inserted into the final LSA rule the clause that prevents modifying an non-LSA qualified aircraft to conform to the LSA rules.:mad2:

The FAA: Never let logic get in the way of a decree.
 
Interestingly, the C140 is comparable to the Skycatcher in many respects, but has much larger tail surfaces, and notably, delightful spin (recovery) characteristics.

I'm not an industry insider nor aerodynamicist, but last year around OSH time, I had a conversation with a credible expert on the tail of the Skycatcher. Considering the similarities in overall size and performance of the aircraft, I noticed that the area of the vertical fin of the Skycatcher is (or was) much smaller than the 150 and 140, and I was curious about it. I learned that tail feathers are fairly "expensive" in engineering terms. As the size and weight of the empennage increase, stability benefits, but W&B, drag, and other attributes (culminating in useful load) are compromised, especially since the moment arm is so large. At the end of the day, the ideal tail is "just big enough".

Cessna has stiff competition in achieving a well-defined set of performance goals, but they're at a disadvantage in using a heavier engine and expecting Part 23 performance from their design. Not an easy set of expectations to live up to in such a weight-constrained category. It's no surprise that they have to find the edges of the design envelope to meet the objectives. The same expert commented that development work on the jets was probably easier work than the Skycatcher program.

Certainly the fin area is only one of many design attributes that have influenced the performance of the airplane, but nonetheless I thought it was an interesting conversation.

M
 
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