Loss of ASI in Pilatus B-4
Aerotow launch from Ringmer. On becoming airborne, realise that the ASI is not working. Stay with the launch to 2,000 ft. On clearing the tug, carry out gentle check stall to calibrate my ears with the slipstream noise. Carried out the rest of the flight using Mk. 1 lugholes as ASI.
On landing back at Ringmer, verified that the reason was due to disconnected pitot plastic plumbing. Never told anyone about this before - put it down to experience, but always included a more thorough check in my pre-flight inspections and on rigging the beast.