Two from me - both on Lynx and in NI.
Just after establishing in the near cruise near Omagh with a full load in the back and as a newish pilot, Captain asked if I would like to fly in balance. On attempting to put the ball in the middle, I found that the pedals were jammed and announced this to the Captain. Having found they were jammed on his side too. Having found that 40kts gave us fairly straight, we set ourselves up for a long slow approach to a sports field at the barracks. The point where we touched down was fairly firm but quite wet following recent rain which led to a 50 metere-ish run on. Feeling rather pleased with ourselves we called for tech assistance and waited for it to arrive. First to arrive though was the Garrison Quartermaster - who was also the Garrison Cricket Officer - and somewhat un-amused by the ploughed furrow across all 3 of his wickets. The cause of the jam was that, on the lynx, the left seat controls were removeable duals. The "Pip Pin" that secured one of the pedals had a retaining wire which had formed into a loop. The point in the loop where the 2 wires crossed had jammed between the stalk of the pedal and a bracket that held the "Brush strip" designed to keep FOD out of the control run.
Second one, about 5 years later, was doing some parachute drops over Ballykelly. On a run in at about 5000ft and 60kts when the pedals jammed solid. Tried all sorts to free them but nothing worked. Held the run in heading until over the DZ and got the jumpers away. Collective seemed a bit stiff but cyclic was okay. Found a "comfortable" speed and flew an approach back to the airfield. Suddenly, with about 100ft to go, everything freed off. Landed and shut down and awaited tech support. System tested by techs, no fault found, full hydraulic check - all serviceable. This check can be done on the Lynx as it has an Accessory drive system on the gear box that allows both hydrualics to be powered up without the blades turning - (in answer to Uplinkers post and Ascend Charlies reply). Hover check. all okay, short airtest, all okay, flew back to base. REME all over it through the night but nothing found. Next day, another crew due to take the aircraft when, during pre-flight "Full and free" control checks, everything locked up again. Aircraft returned to hangar where, deep in the control runs a small burr was noticed on the collective/yaw interlink which only affected it when the cyclic/collective interlink was in a certain position.