Max Weight for Aerobatics

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Trifit65

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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
 
I do what I call "soft" aerobatics. Inverted flight, slow rolls - the most violent maneuver is an occasional immelman. None even approach 3 G's. I figure I stay under the airframe forces of a 60 degree banked turn. I am as safe as during a cross-country, and radar watches me for traffic (usually). I gave up on parachutes over ten years ago.
 
The old adage is correct. The POH reflects the TCDS and manufacturers guidance.
Of course you know all that...
The limits are put there to keep the airframe from fatiguing due to repeated stressing over the life of the airframe. The 1.5 service factor is where the manufacturer expects the airframe to buckle, bend, break or deform.
Can you fly it overweight (acro or not)? Sure. But screwing up or falling out of a maneuver doing acro can have you recovering overspeed or pulling too hard to recover and all the sudden you're overloading the wings, struts, tailfeathers, etc.

JMPO

Chris
 
I agree with that - when I was trying to learn aerobatics, I took a single seat Taylorcraft to red line in a messed-up recovery. Then I decided to get some instruction. Since then I have not had an aircraft out of what I think is a very safe envelope. And I am inverted once a week, year in and year out ( always well inside the weight limit for aero).
 
Hiperbiper said:
The old adage is correct. The POH reflects the TCDS and manufacturers guidance.
Of course you know all that...
The limits are put there to keep the airframe from fatiguing due to repeated stressing over the life of the airframe. The 1.5 service factor is where the manufacturer expects the airframe to buckle, bend, break or deform.
Can you fly it overweight (acro or not)? Sure. But screwing up or falling out of a maneuver doing acro can have you recovering overspeed or pulling too hard to recover and all the sudden you're overloading the wings, struts, tailfeathers, etc.

JMPO

Chris
Click to expand...

Thanks for saying that Chris. :TU:
 
Try flying with 1/4 tanks of fuel....you’re below the weight andCG limits...hack the clock on takeoff....go fly 30-45 minutes and don’t worry about it!

These planes don’t recover well when they are overweight and out of CG....

IMHO...YMMV
 
Well, an aircraft with an 1800 max gross limit and a 6G limit would have to be engineered to withstand a load of not less than 10,800 pounds. An aircraft weighing 1900 pounds would exceed 10,800 pounds at 5.7G. Hypothetically an aircraft that that did not exceed 5G could be flown 360 pounds over gross without exceeding the design load limit, while an aircraft that did not exceed 4.5G could be flown 600 pounds over gross.

None of the approved figures in the POH need more than 4G to fly well. In my experience the difference between 4G and 4.5G is huge, and 4.5G is quite hard to exceed in a Decathlon.

Nobody will say this officially, but 20 or 30 pounds of excess weight is not going to pluck your wings off. Plenty of Decathlons fly acro with 2 full grown men and half tanks on a regular basis. Google some images of Greg Koontz; the guy is a hoss. He gives dual acro in a Decathlon all the time, and there ain't nothing on his website about size limits for students.
 
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Trifit65 read this accident report. Like I said these airplanes don’t recover very well outside the aerobatic envelope. It’s not the “g’s” it’s the forces required to recover from an upset.

www.flyingmag.com

Unrecoverable Spins - FLYING Magazine

In December 2000 a tower controller in southern Florida received a single radio transmission: “Mayday mayday mayday Pitts 260DB in an unrecoverable flat spin at 3,500 feet.” The airplane crashed in the Everglades, coming to rest partially inverted and nearly vertical in several feet of water...
www.flyingmag.com www.flyingmag.com
 
I am pretty widely shouted down when I suggest that a Citabria or Decathlon can get into a difficult-to-recover spin. I still think that there are ways to get in trouble in these fine airplanes during prolonged spins.
 
A Pitts is a MUCH different aircraft. During the 70's and 80's, there were dozens of fatal accidents involving unrecoverable spins in Pitts.

A Pitts is very short-coupled, and as a result has an extremely high rotation rate of about 540 degrees per second (try to visualize that). Pitts also have large control surfaces with lots of authority. That combination of characteristics led to two fatal accident modes.

First, it was possible to enter an accelerated flat spin that was unrecoverable using conventional anti-spin inputs. Second, when recovering from an upright spin, the recovery inputs could transition the spin into an inverted spin in the opposite direction. That sometimes resulted in the pilot holding pro-spin inputs all the way to the ground and wondering why it would not stop.

The Pitts community eventually reached consensus that new Pitts pilots required 5-10 hours of type-specific transition training focused on landing and advanced spin recovery. The advanced spin training focused on getting into and out of accelerated, flat, and inverted spins. There are several well-known instructors such as Bud Davidson and Bill Finagin who specialize in Pitts-specific training. That has for the most part stopped the steady stream of fatalities.

There is nothing remotely comparable for the Citabria and Decathlon. Review the NTSB reports and decide for yourself. Citabria and Decathlon spin recovery characteristics are benign.

Any aircraft can be unrecoverable from stalls and spins if the CG is too far aft. However, being over gross and being out of CG are not the same thing. Draw the envelope and you will see that added weight over gross at the front and back seat stations will not result in an aft CG condition. In fact, excess weight in the front seat pushes the CG towards the forward limit.
 
I asked for that.

How about the lowly J3 ? I have it on good authority that at least one J3 got stuk in a spin that was extremely difficult to recover from.
 
Bob Turner said:
I asked for that.

How about the lowly J3 ? I have it on good authority that at least one J3 got stuk in a spin that was extremely difficult to recover from.
Click to expand...
Never flown a J3 and have zero knowledge of spin characteristics or CG range. I totally defer to your experience in that area.

For the Citabria and Decathlon, I have gotten advanced spin training from several reputable instructors, including Adam Cope, the current IAC test pilot for Sportsman sequences. My training, backed up by information in the POH which reflects the results of certification flight testing, is that conventional anti-spin inputs will recover a Citabria/Decathlon and no special recovery techniques are required.

Load your plane aft of CG and all bets are off.
 
+6 -5 G’s said:
Trifit65 read this accident report. Like I said these airplanes don’t recover very well outside the aerobatic envelope. It’s not the “g’s” it’s the forces required to recover from an upset.

www.flyingmag.com

Unrecoverable Spins - FLYING Magazine

In December 2000 a tower controller in southern Florida received a single radio transmission: “Mayday mayday mayday Pitts 260DB in an unrecoverable flat spin at 3,500 feet.” The airplane crashed in the Everglades, coming to rest partially inverted and nearly vertical in several feet of water...
www.flyingmag.com www.flyingmag.com
Click to expand...
Great article! I appreciate the detail. I too had been instructed on using the PARE method for spin recovery. What I don't understand though is why the 1980's decathlon POH says says forward stick (first) and then opposite rudder (second)? Maybe back in those days, they didn't know better?
 
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