Infrequent:
Appreciate your knowledge on turbine blades, do you know how many there are on a Piper, or a microlight, or a glider ? Those folks running the regulator probably don't - in fact some are on record as stating "‘I know nothing about aeroplanes".
But you know, don't you ? So you must know what the other unspoken risk of VA is that grounded all these aircraft along with the jets ?
"measured" ? "proportionate" ? More like knee-jerk, incompetent, a**e covering. (unless you can enlighten us as to the VA risk to gliders ?).
You may have a point about piston engined aircraft and gliders. Last time I looked, the Piper I fly had an airfilter, but hey! the aircraft is hired so what do I care anyway? A little ash exposure might help the rings seal and save me a honing job.
When I studied risk management as an engineer and later when I had to apply it in an airline engineering department, we worked on
facts. In the absence of facts regarding the likelihood of exposure to some quantity of ash by large numbers of aircraft, the regulator acted promptly and grounded the fleet until the available facts could be marshalled and discussed by people with the relevant expertise and experience. They did this promptly, efficiently and responsibly in a matter of weeks.
The fact that the regulators response didn't suit some of you is irrelevant.
As for comments about "commercial considerations" and individual airline decision making those are also way off the mark. Aircraft Insurance contracts and lease agreements would most definitely preclude doing anything not approved by a regulator, which is probably why Ryanair so promptly grounded its fleet in my opinion.
To put it another way: You would all be screaming about why the regulator
didn't ground aircraft if half the fleet was now ash damaged and out of action for months.