I am rather familiar with this one as I was the squadron’s engineering officer at the time. The squadron was deployed to Leconfield because Binbrook’s runway was being re-surfaced.
XS937 flew satisfactorily on its first sortie that morning (nothing like a successful sortie for establishing the airworthiness of an aircraft…), had a pilot-staying-in turn-round and flew again. On selecting undercarriage down, Simon Manning got two greens and a red, and after trying the usual rolling and pulling tricks to no avail, flew a number of times past Leconfield’s tower for a close look. The undercarriage leg was swinging half way between up and down, seemingly unconnected to its jack. We couldn’t see why it had become disconnected, but it was probably either a failure of the jack eye end (remember the Lightning’s main jack pulled the gear down and pushed it up), or, more likely, a failure of the jack attachment lugs at the top of the main leg casting.
It is unlikely any manoeuvre would succeed in locking a leg down in this condition – the aerodynamic loads on the wheel as it comes down forwards from the swept wing are in the wrong direction. And you cannot do a hammerhead stall and a tail-slide in a Lightning!
The helicopter was scrambled in good time for the premeditated ejection and Simon was quickly back at the squadron. Someone said in disgust “Simon, how could you eject into the sea and barely get your hair wet!” But it isn’t very pleasant seeing one of your friends heading out to sea to abandon an otherwise serviceable aeroplane, and wondering if the canopy/seat/parachute and all the rest is going to work. Thank you 202 Sqn.
In spite of an intense effort by the Navy, we never found any wreckage and that area of sea off Withernsea silts up rapidly. A few weeks later the RAF lost a Phantom in more worrying circumstances and the Navy effort was diverted to that.
Three years later in 1979, a Lightning F3 was abandoned near Valley (on a Missile Practice Camp) for an identical reason. I have seen the pictures taken of this aircraft from the gun camera of a chase aircraft and the trail angle of the broken undercarriage looks exactly the same. I believe the cause of that was found to be a fatigue failure of the lugs.
Later, when I was back at Binbrook again (1981-83), we had a modification issued for the main undercarriage that involved milling off the area near the main leg lugs to remove fatigue damage, and that mod may have been the fix for the cause of the 1979 accident. This caused a bit of consternation amongst the aircrew, who were curious how shaving metal off could possibly make it stronger! The answer can be seen if you take a strip of paper and cut a small notch in the side. Pull on the strip and the paper will tear with quite a small pull. But cut off a bit of the length of the whole strip, including the notched bit, and a good percentage of the total strength of the original strip will be restored. That’s why older aircraft with such mods in their airframes have “g” restrictions towards the end of their working life. 5g may not be 6g but it’s better than nothing.
Last, XS 937 had an incident the afternoon before it was lost when it had a double tyre burst and trundled off the side of the runway at low speed. The ground was like concrete (remember the hot summer of 1976?). Much was made of that at the time by Rumour Control but the view was that this had had no effect on the serviceability of the undercarriage. This was subsequently confirmed to me informally by the chief stressman at Warton, with whom I worked on a Tornado issue. Someone mentioned retraction tests in a previous post, but all they showed you was that the sequencing was correct of jacks, links, doors etc. You cannot in the hangar reproduce the air-loads on the wheels, nor the dynamic loads of, for example, selecting the gear down while rolling the aircraft. XS 937’s earlier satisfactory sortie on 30 July proved that it was serviceable and that the subsequent failure was something new. The 1979 loss proved what that was.
Hope that helps!