Basic aerobatic mods

All-

I'm slowly pulling harder and harder on my 4 while doing some basic aerobatics. Is anyone doing any mods to their -4 that I should be doing during "Sportsman" style aerobatics? My 4 is extremely well built, but didn't know if any of you were reinforcing anything.

O-320
968lb empty weight

Thanks!
JN

nah no mods required. I trust you are flying within the aerobatic W&B limits, and as such there is ample history to show no specific problems with the -4. Of course monitor the elevator spar per the SB, but I think history dictates that to be more of a manufacturing issue. Aerobatics will wear out any aircraft faster than if flown at 1g always.

Absolutely staying within the envelope. Also staying WELL within the G envelope, too. Are you saying that I should do the spar SB? I know knew that was an issue for the 7-8-9, but I didn't realize that was the -4 as well.

JasonNoll said:

Absolutely staying within the envelope. Also staying WELL within the G envelope, too. Are you saying that I should do the spar SB? I know knew that was an issue for the 7-8-9, but I didn't realize that was the -4 as well.

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What spar SB?

I just checked the Van's site and found this SB about missing bolts, is that what you are talking about? If so, the -4 (and -6) spar is completely different. However, it would be a good thing to check all your spar bolts with a torque wrench every condition inspection.

CATPart said:

nah no mods required. I trust you are flying within the aerobatic W&B limits, and as such there is ample history to show no specific problems with the -4. Of course monitor the elevator spar per the SB, but I think history dictates that to be more of a manufacturing issue. Aerobatics will wear out any aircraft faster than if flown at 1g always.

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I wasn't aware of one either, but then I read the above. I'll absolutely check the bolts tomorrow in fact.

Thanks for the input guys. Great stuff

Never mind. I found the one that includes the the 4 regarding the hinge points. Is there anything referencing the stab root spar doubler?

JasonNoll said:

Never mind. I found the one that includes the the 4 regarding the hinge points. Is there anything referencing the stab root spar doubler?

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You can check for yourself by looking here.

Every year, you should check the Van's site for any relevant service bulletins.

Yes, the hinge points which are in the spar web

SB14-02-05

SERVICE BULLETIN 14-02-05
Date Released: February 5, 2014
Date Effective: February 5, 2014
Subject: Cracking in elevator spar web near elevator attach points.
Affected Models: All RV-3, 4, 6/6A, 7/7A, 8/8A Flying aircraft
Required Action: Inspect for cracks as described in this document. Stop-Drill cracks (if present) then apply E-00001A and E-00001B Hinge Doubler fix as required to cracked elevator hinge positions. RV-3,4 and 6/6A customers will need to fabricate their own doublers using E-00001A and E-00001B as a guideline.

My - 6 is 10 months / 60 hours from brand new - about 10 of which were aerobatics. I decided to to the 1st annual at 10 months just to fully check it all sooner rather than later.

Without looking my inspector told me to check the 2 x AN3's on the fin post about 1/3 of the way above the tail wheel ...... sure enough I got another full turn onto both nuts .

The 2 lower centre bolts on the engine mount went another 1/2 turn and the exhaust hangers needed to be adjusted (for about the 3rd time).

My thought is that if the aircraft is regularly used for aeros it is prudent to accelerate all the regular inspections and checks, At the moment I'm removing cowls every 10 hours and checking things like battery security, ignition timing, prop torque, canopy latching and crankshaft flange every 20 hours. I'll be happy to slow this down slightly as I build up a record of trouble free operation.

Oh, one more thing I've found - I "use" brake fluid up during aeros (it leaks slowly through the sintered metal vented cap) check regularly !

"G" whiz...

JasonNoll said:

All-

I'm slowly pulling harder and harder on my 4 while doing some basic aerobatics. Is anyone doing any mods to their -4 that I should be doing during "Sportsman" style aerobatics? My 4 is extremely well built, but didn't know if any of you were reinforcing anything.

O-320
968lb empty weight

Thanks!
JN

Click to expand...

Jason,
I performed sport aerobatics in my similarly equipped RV4 for 10 years, 1000 hours. I built it light, very basic with the .016 control surface skins (standard then) air oil separator, carb, wood prop but no structural mods. My HR2 had the RV4 empennage with .020 skins.
In my sportsman routine in the RV4 and HR2 I never saw more than 3.5 G's positive and only exceeded 5G once in my 4. No cracks were found on the Vans recommended inspection on either airplane (experimental airplanes don't have SB's). I did follow several personal guidelines for loading during acro.
1. 1/4 fuel in both tanks or less.
2. Solo only.
3. Smooth G onset above 120 knots.

Moderation is crucial...

V/R
Smokey

Some builders used .020 skins on elevators and rudder