I have seen some stupid stuff at a college flight school, but I have never seen or heard of CFIs or students routinely doing aerobatic maneuvers in an Arrow. Aerobatics are actually difficult to do in a trainer, so most of the pilots dumb enough to do that wouldn't have the skill to perform any maneuver more complicated than an 80 degree bank.

Overload fractures due to excess G's in an Arrow happen further out the wingspan. If you snap a wing on an Arrow (According to Piper, it happens at 163.7% of design limit load which is around 7G) it fails at approx. 40% span.
If this damage was caused by heavy loads that were within the design envelope, that's a serious design flaw in itself.
So I'd imagine if the fatigue crack was caused by constant abuse, it would have been in a different location (assuming that the failure point is where the highest stress also is during excessive G maneuvering).

You said what I was thinking.

It’s not that difficult to roll or loop in a trainer. Depending on the airplane and the proficiency of the pilot the proper execution and if not the recovery may be very difficult.
No airplane I know off came apart during a spin. They do come apart in a botched recovery.
Considering a plane used for CPL Training does a lot of landings that plane may have had 25000+ landings including its share of unreported hard landings.

That would be a positive G overload you have described. I wonder where the failure would be if after a zillion student pilot smack-it-into-the-ground landings would be. In those sorts of landings, from the wing's perspective, they are negative G events.

The problem is when the maneuver is not done correctly normal category airplanes are not stressed to the G-loading necessary to sustain such maneuvers. And since such maneuvers are not authorized the offenders rarely, if ever, fess up.
This was not a very old airplane by any stretch of the imagination and, according to the preliminary report, no sign of corrosion.

I've been around aviation long enough (32 years), that I've seen some pretty dumb stuff. Don't sell pilots short- they will try aerobatics in just about anything, often with spectacular (in a bad way), results.

My emphasis.


https://app.ntsb.gov/pdfgenerator/Re...relim&IType=FA


" Preliminary examination of the left wing main spar revealed that more than 80% of the lower spar cap and portions of the forward and aft spar web doublers exhibited fracture features consistent with metal fatigue (see figure 1).The remainder of the lower spar cap, spar web doublers, and upper spar cap displayed fracture features consistent with overstress fracture. The fatigue features originated at or near the outboard forward wing spar attachment bolt hole (see figure 2). None of the surfaces exhibited visible evidence of corrosion or other preexisting damage. The right wing also exhibited fatigue cracks in the lower spar cap at the same hole location extending up to 0.047-inch deep."

Would a couple of high speed ( > Vne) dives (low passes) sufficiently weaken the wing.
I was glad when the owner of the flightschool I worked for switched to a whole new fleet.
I knew and flew every airplane from zero hours, hired the CFI’s that flew them and was very friendly with our Head of MX.
I knew what was wrong with each airplane and how it was repaired.
We at one point considered data loggers ( altitude & airspeed).

If I were a flight school owner today I would have data recorders in all airplanes that could give me FOQA type data. I understand ERAU has this but doubt they were in this airplane from day 1.