[SquawkVFR]

I recently purchased an RV-7A that has an airworthiness certificate which includes the usual charachteristics, such as Vso, Vx, Vy, weight, and CG. The builder did not certify it for aerobatic manuevers. I didn't build the plane, but it's been flying for several years and been through a decade of condition inspections and pre-buys. However, that doesn't tell me anything about its aerobatic manuever capability. At some point, I'd like to get training and eventually be able to fly appropriately-rated aerobatics this airplane.

I understand I can contact a FSDO to arrange a test flight to demonstrate aerobatic manuevers, but I'm a little hesitant to do so without doing some ground load testing of the structure first.

I haven't seen this mentioned anywhere before, so please let me know if this exists somewhere that I've not yet seen. But what I would like to do is conduct some ground load testing on relevant surfaces and structures prior to testing in the air. The last place I want to learn about an insufficient load capability of an aircraft structure is in-flight.

With all that being said, is there a way to test structural loading on the ground prior to an aerobatic flight test?

I'm thinking if you're a structural engineer, you ought to be able to determine the rated loads based on G-rating and then apply a static load to those structures to verify the rating. Shooting from the hip, I'm envisioning anchoring the gears to the ground and applying a uniformly distributed load to the underside of the wings and the top side of the horizontal stabilizers simultaneously to whatever the equivalent of 6Gs would be. Then to confirm 3G negative loading, apply a uniform load to the top side of the wings and bottom of the horizontal stabilizier.

I'm just spitballing here to start a conversation. Let's discuss...

 

[BobTurner]

As you noted, you’ll need to go back into phase 1 (contact fsdo) and demonstrate each maneuver. Not required but I’d suggest a parachute.
I believe Vans has done exactly what you’ve suggested, e.g., turned the airplane upside down and loaded the wings, with a calculated distribution of sandbags, to simulate the positive g loading. Perhaps they would share details with you.

 

[Jonnyb]

I recently purchased an RV-7A that has an airworthiness certificate which includes the usual charachteristics, such as Vso, Vx, Vy, weight, and CG. The builder did not certify it for aerobatic manuevers. I didn't build the plane, but it's been flying for several years and been through a decade of condition inspections and pre-buys. However, that doesn't tell me anything about its aerobatic manuever capability. At some point, I'd like to get training and eventually be able to fly appropriately-rated aerobatics this airplane.

I understand I can contact a FSDO to arrange a test flight to demonstrate aerobatic manuevers, but I'm a little hesitant to do so without doing some ground load testing of the structure first.

I haven't seen this mentioned anywhere before, so please let me know if this exists somewhere that I've not yet seen. But what I would like to do is conduct some ground load testing on relevant surfaces and structures prior to testing in the air. The last place I want to learn about an insufficient load capability of an aircraft structure is in-flight.

With all that being said, is there a way to test structural loading on the ground prior to an aerobatic flight test?

I'm thinking if you're a structural engineer, you ought to be able to determine the rated loads based on G-rating and then apply a static load to those structures to verify the rating. Shooting from the hip, I'm envisioning anchoring the gears to the ground and applying a uniformly distributed load to the underside of the wings and the top side of the horizontal stabilizers simultaneously to whatever the equivalent of 6Gs would be. Then to confirm 3G negative loading, apply a uniform load to the top side of the wings and bottom of the horizontal stabilizier.

I'm just spitballing here to start a conversation. Let's discuss...

I think you have that the wrong way round. A 6G load test would have a load applied to the top of the wing, bags of sand or cement. A negative G load test would mean flipping the aircraft and placing a load on the underside of the wing. Also the load isn't uniformly distributed along the wing. The wing root takes much more of the load than the tip. On your RV-7 the wing tip itself is part of the lift producing structure, but its unable to carry much loading. If you start applying loads to this area then you will likely break something.

As said above this has already been done for you by Vans. So I'm wondering what it is that you want to achieve by doing this to your aircraft? I think your time would be much better spent ensuring that the aircraft was built to plans in the main load bearing areas. Center section to wing spar join, and making sure the horizontal stabiliser is attached to the main upper longerons with the correct edge distance.

Kit Planes did a series of articles on testing aircraft structure, worth a read.

Testing, Testing! - KITPLANES

Part 1: Wing Static Load Test

www.kitplanes.com

 

[SquawkVFR]

I think you have that the wrong way round. A 6G load test would have a load applied to the top of the wing, bags of sand or cement. A negative G load test would mean flipping the aircraft and placing a load on the underside of the wing. Also the load isn't uniformly distributed along the wing. The wing root takes much more of the load than the tip. On your RV-7 the wing tip itself is part of the lift producing structure, but its unable to carry much loading. If you start applying loads to this area then you will likely break something.

As said above this has already been done for you by Vans. So I'm wondering what it is that you want to achieve by doing this to your aircraft? I think your time would be much better spent ensuring that the aircraft was built to plans in the main load bearing areas. Center section to wing spar join, and making sure the horizontal stabiliser is attached to the main upper longerons with the correct edge distance.

Kit Planes did a series of articles on testing aircraft structure, worth a read.

Testing, Testing! - KITPLANES

Part 1: Wing Static Load Test

www.kitplanes.com

I'm not a super seasoned pilot, so I aplogize if I got things backward. I'm just trying to think through this... If the aircraft is straight and level, and you pulled back on the stick, I'm assumig that would be a positive G manuever, causing the plane to pitch up. For the plane to pitch up, I'd imagine the underside of the wings would see increased loading in order to produce more lift. If we assume, as you suggested, that the top side of the wings would get more load in a positive-G scenario, wouldn't that cause the plane to pitch downward, producing negative G loading?

The reason for wanting to do this test is explained in my OP.