The report raises a number of important elements, and is, in my opinion, adequately objective in the discussion of the cam lobe wear issue, and the lack of understanding of the actual effect of that wear on engine performance. I cannot assert the affect of this amount of cam lobe wear, but I've seen engines in service (which certainly should not have been) with more! Checking performance is not a good measure of this, checking for metal in the oil filter or screen is. There is a reference to metal resulting from this wear being detected, an that's where to hang your hat on this issue.
However:
The report completely overlooks an important characteristic of the PA28 series of aircraft, which I'm certain would have been a major contributing factor in this accident...
PA28's have a stabilator rather than the conventional stabilizer/elevator combination. In "normal" operations this is a completely benign difference. Where it does show up, however, is in very low speed, nose high operations. Here's what happens: Pilot commands more nose up at low speed, takeoff being the most likely occasion. Where the conventional stab/elev combination would have a greater deflection of the elevator, the camber of the horizontal tail as a single flying surface is increased (as well as a change in effective pitch angle). As such, it's capacity to create more "down" lift before stalling, or experiencing a large drag increase is better. (okay purist aerodynamicists, have at me, I've got experience with the result, not the theory). On the other hand, the stabilator, has only the opportunity to change angle of attack to create more "down" lift. Like any flying surface, it will reach an angle of attack, where the Cl max has been passed, and the increase in drag is no longer proportionate to the increase in (down) lift. Yes, I'm sure that Piper gave this a lot of thought and test all those years ago, and their engineers know more than I do about this, but...
I was the right seat check pilot to a junior pilot in an Arrow PA28R-200 many years ago. He rotated prematurely out of a 1000 meter runway. It was a hot day, but we were quite light, and it was a 200HP version of the aircraft, so power was not a problem. The plane was stuck in ground effect, with the pilot holding the controls 'way back. The stall warning was sounding. The aircraft would not accelerate, or climb away. Landing back might have worked, other than the runway end was approaching, and he (well I suppose "we") had allowed the aircraft to drift off the side, so there was not a runway under us any more. I was shocked at the "poor performance" I was experiencing in this aircraft I thought I knew so well. We were nearing the obstacles. We did not wreck the plane simply because I "locked off" and retracted the gear. The resultant reduction in drag was all that was needed to allow the plane to slowly climb away.
Shocked by what had just happened, I went to experiment. I flew a PA28-140, which I believed to be in good condition, off a very long frozen lake (runway and width length no longer a concern). Sure enough, I could get the plane very nose high, with lots of aft control, and it would not accelerate or climb out of ground effect. My only option was to land back (fixed gear). I repeated this configuration enough to satisfy myself that this is a configuration to be avoided in PA28's (and probably Cessna 177's as well) So I do! The thick wing has great lift, and resists stalling well. The stabilator tail is not ideally matched in this attribute.
It is my opinion that a stabilator on a PA28 can be taken to an angle of attack which is just enough to stall it, not perhaps to the point where it looses all lift, but to the point where it's being stalled just creates so much drag, that the power of the aircraft cannot overcome it, so as to accelerate and climb away.
A pilot, particularly with only a hundred plus hours on type, who was rapidly becoming concerned about running out of runway, would be likely to over rotate the aircraft at low speed, and enter this phase of flight. This would explain how the aircraft, at the same (or heavier weight) had taken off with no problem earlier in the day. This phase of flight is very stable, and not in itself alarming, until the pilot realizes that there is nothing left, and more is needed. The lower power PA28's are the most vulnerable. You don't hear of this with the higher powered variants, or the Aztec's, simply because they have the power to mask this characteristic.
So, it is my opinion that the AAIB report has overlooked this characteristic of these aircraft, and it's potential to create huge drag, and loss of performance during takeoff. That said, gathering data on this characteristic has great potential to be dangerous, if not conducted with ample runway. Perhaps analysis (which is well beyond my capabilities) would be a help, but I am not the one to say...
As to the original question, it is my opinion that performance testing as a routine element of maintenance activity, in the realm of this type of aircraft, is probably not adequately repeatable, so as to produce meaningful results. There is too much opportunity for variation in condition, and pilot technique. These aircraft and engines have a half century of operation, and their strengths and weaknesses are well understood. The accumulated maintenance procedures for these engines, when undertaken correctly, produce consistently airworthy engines. Changing the requirements of maintenance on them now will have little effect on aviation safety. The other airframe related defects which could affect performance should also be easily spotted during a proper inspection.
I'm not saying that a flight test is a bad idea following maintenance, and I've certainly found my fair share of defects during such flights, but they were not often performance related, more things which just did not work the way they were supposed to. Perhaps pilot awareness of characteristics affecting takeoff performance in PA28's would be a more worthwhile objective. (Uh oh, I'm backhandedly suggesting a type endorsement, for one of the world's most common aircrat types! I'd better not do that!)
My thoughts for the evening...
Pilot DAR