Ad-astra,
Grateful for any correction but my understanding is that the petal airbrake on the F28/F70/F100 is all or nothing, whereas the 146/ARJ one is variable; a claimed advantage for speed control by the men of Hatfield, although the sticky throttle boxes on the early 146's was probably more relevant. It's also one of the system differences between the 146 & ARJ. On the 146 the lift spoilers were manually activated by pulling the airbrake handle back through a detent released by the WoW system. The Avro introduced an autospoiler function, although SOP was still to crank back the handle for the day the automatic's failed.
Interestingly the same men of Hatfield also claimed genealogy from the Bucc. rather than Fokker (naturally!). Those operating onto the East London aircraft carrier may see the resemblance.