Max Weight for Aerobatics

Chuck Schweiss

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Hello All

I understand that the decathlon 1800 Lb max weight for aerobatics protects for 6 G’s. And someone on this forum said earlier, that if a plane was approved for 6 G’s, then it must have been designed to handle 9 G’s.

Question: Since many of us might not want to pull 5 or 6 G’s when we fly, how much extra weight do most people feel is okay to fly aerobatics?

The old adage is, if you fly just a pound over max weight, then you become a test pilot.

But technically speaking, since Normal Category is 1950 lbs max, and normal category allows up to 3.8 G’s, then, technically speaking, you could fly aerobatics at 1950 lbs if you maintained less than 3.8 G’s. I am not advocating or recommending this ... It is more of an academic consideration.

But as I am pushing 215 pounds in my late 50’s, it’s becoming harder to find a decathlon I can fly without finding a 100 pound jockey instructor.

Is there any unofficial guidance that suggests we can fly aerobatics 10, 20, or 30 pounds overweight if we fly lower G’s. What is the community thought? At what weight do folks think there is a safety issue?

Thanks very much
Easy answer...
 

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towpilot

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So...this post is going to start with I watched some YouTube videos...

Regarding limits for aerobatic (or non-aerobatic) flight at various weights, I have often wondered why no V-G diagram is provided for the Super Decathlons to help us pilots understand operating limits in the flight envelope. I found videos on YouTube that walk viewers through how to make their own. I ended up doing just that. (Disclaimer about trusting these attached graphs as truth: I may not be a smart man).

If what I came up with is correct, then it helps to see what the flight envelope looks like.

One reference video:

I hope that helps with this interesting discussion.
 

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djpacro

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towpilot

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@djpacro Thanks for posting that feedback. That is interesting insight that I had not considered. It made me start to wonder, so to the books I went, including the link you provided. I found a note in the Super Decathlon POH stating that the load factor limits of +6 and -5 G's are applicable within the yellow arc of the accelerometer in the aerobatic category (1800 lbs max), but there is no mention that the limits are reduced above Vno. The POH reads:

"Maximum load factors for Normal operations are shown by the ends of the green arc on the accelerometer. Load factors within the yellow arc up to the red radial lines are permitted only in the Acrobatic Category."

For context, the Normal Category is +5/-3G, which are both in the green arc on the accelerometer. Acrobatic is +6/-5G on the accelerometer, which are both red lines. Yellow is in between. No mention of speed is noted. Based on that, I would read that I can safely fly below 1800 pounds (not comfortably on my head or practically speaking) to -4G at 190 mph in smooth air.

With what American Champion has provided, I don't see a reduced negative G limit above Vno up to Vne. I did look at FAR 23.333 and it does appear that there may be a reduced negative limit in the Normal category, which is interesting since Amerian Champion makes no mention of reduced G limits above Vno in the Normal Category. Perhaps those limits take that reduced area into account for simplicity.

I would appreciate any further insight on this since the more I study the V-G diagram, the more I find it to be useful for understanding the flight envelope. At least I am learning, which is great.
 
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djpacro

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FAR 23.333 specifies a reduced negative G limit for both normal and aerobatic categories " (3) Factors varying linearly with speed from the specified value at V Cto 0.0 at V Dfor the normal and commuter category, and −1.0 at V Dfor the acrobatic and utility categories."

Of course, the designer may have chosen not to apply the reduced limit.

Then there is Appendix A - Simplified Design Load Criteria for small airplanes which they designer may have used in lieu of FAR 23.333. Appenndix A does not provide for reduced limits at all. https://www.risingup.com/fars/info/part23-A-APPX.shtml