Originally Posted by
ZH875
Not all were, IIRC, very few probes were initially bought as they were considered as Role Equipment, so most of the fleet didn't have one fitted for quite some time
Unless it changed very late in the day all 25 were purchased with probes. They became de facto role equipment from the outset in that no spare probes were procured and the servicing & repair margin was within the original 25. In the early days this effectively meant that the Mk5s were fitted with probes (trim) and any gaps in probe availability were held on the Mk4s. Clearly that changed for sure!