CR1 Hesh Correction Add/Drop fault

Discussion in 'RAC' started by ECE-Tech, Jun 2, 2011.

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  1. Was the fault ever located?

    Symptoms were after a HESH shot fell short, an add correction was entered and the next shot fell shorter still, as if a drop correction had been entered. It affected a lot of the CR1 fleet but not all. I would suggest a substantial minority of the fleet was affected.
    I got posted from LAD to REME Bn whilst it was still being investigated and by the time I got back to First Line, CR2 was in service.
    I never thought to ask at the time if it was ever solved and it only springs to mind now four years after finishing my 22years.
    I do know that REME Artificer students at Arborfield were assigned to investigate it as a research project and were assigned range time and muniton.
    Was it ever solved?
    Before somebody pipes up why have I posted it here and not in the REME forum.
    I want to know if the tank crews ever received a satisfactory explanation for the problem and got it sorted.
  2. CR1? If this is keeping you up at night may I suggest you need to get out a bit more!
  3. My post at 18:24 Hrs, your reply at 18:30 Hrs. 6 Minutes
    Still early hours and not stopping me from sleeping.
    Have you anything sensible to add to to the thread?
    Or do you insist on being a complete throbber?
  4. The second! :)
  5. Sorry been away awhile and just spotted your thread.

    The problem was deemed to be linked to loss of gun - sight relationship ?? why? never did get an answer, interestingly a similar problem occurred with at least three of our chieftain "heaps of shit" taking part in CAT 81, zeroed in three rounds, drove 300 mtrs onto bound 1 for our turn in the competition, rounds falling 100mtrs short, only after two engagements did the penny drop, added 100 to every lased range.

    Barr and stroud, marconi and every buggers uncle ripped the c/s involved to bits but came up with sweet FA...loss of gun-sight relationship!! Not an excuse, but it had a serious effect on the teams overall performance and the points scored, ce la vie.
  6. Loss of gun-sight relationship is not an explanation for the problem but a description of the symptoms.
    A classic example of someone stating the bleeding obvious.

    We seem to be talking about two different problems here. In your case all further rounds were falling short which points to free-play within one of the linkages.
    With the Add-Drop fault it only affected Hesh engagements where a second shot was required. When the next engagement was with DST then it could hit the target.
    The drop-short was not carried over from one engagement to the next.
  7. If it was that ferking obvious then i am pretty sure that the linkage would have been sussed straight away by the miriad of schools instructors, civvie contractors etc, in fact no official reason was ever given, the REME/ATDU/GUNNERY school report simply stated that a loss of gun-sight relationship had occurred in each instance.

    My own c/s was taken straight away onto an adjoining range and we fired 6 DST only 2 of which dropped short 100m?
    faulty bag charges? ammo? or a computer problem?????
  8. The original post was about a possible "problem" with the HESH Add/Drop correction routine. ie engagements using HESH or SH-PRAC rounds and not DST.
    There were also linkages within the sight itself where freeplay could have contributed to the fault you experienced. The on-tank checks would not neccessarily have found this. Weren´t the gunner´s drills to finish the elevation lay by elevating and not depressing onto the target to try to eliminate freeplay?

    Faulty bag charges or ammo is a possibility. Computer problem less so.
    More likely IMHO (for the HESH corrections) would have been an EPS slipping very slightly under recoil conditions.
  9. I had a similar problem with the commisioning of my first CR1, it was with firing Fin, two of the six rounds went off target. Never did find out what caused it, my tank ended up plugged into the tower for the rest of the ranges.
  10. With the first pre- service version of IFCS this occurred on a couple of occasions with HESH. The boffins thought it to be a software issue and did some work on it. After a couple of weeks we had it back and never had the problem again. When the first service level equipment was installed Chieftain the next problem that occurred was another software problem was intermittent laser which sorted out the gunners from the pointers....That was resolved with another software re-load.......what happened next I do not know as got posted elswhere......

    Perhaps the issue with C1 was a similar hiccup!

    "No Laze"...Hesh 2600 fire!
  11. I can understand a software "fault" causing intermittent laser. If the gunner presses and releases the button before the input is polled then the laser will not be fired because the software hasn´t seen that is has to do so. When it checked to see if the button was pressed, it had already been released so no input registered. Solution would then be to poll the input more often.

    I cannot however understand a software fault causing the Add/Drop correction fault which only affected specific vehicles although all tanks in the squadron had the same software. In the squadron I was attached to, the commander had to monitor the display on the CCMU to check the Add correction had been accepted before allowing the gunner to continue with the engagement, so it wasn´t a case of an Add not being registered by the computer.
  12. Unfortunately I was not a boffin so sadly I am unable to offer any further information other describe an incident...which may be short of a couple of process as its been some 40+ years now since I last indulged.
    Normal: "Aquire target, select ammo and centre elipse equally around target.....Lase, autolay...elipse moves off and gun follows...ready

    Error: Aquire target, select ammo and centre elipse equally around target.....Lase, autolay...elipse moves off but elipse drops below and right....the gun does not follow...
    start procedure again...sometimes it would not happen again for the remainder of the firing period.

    This happened a few times both static and mobile

    Thats the best i can do, hope it helps.
  13. Sticky relay occasionally not making contact on change-over, software fault or loose cable connection causing intermittent open-circuit.

    Relevant to the last of the causes I just mentioned, on my CR2 course I was supposed to find an unspecified fault.
    After dropping down into the turret checking and tightening cables on the way (standard procedure from 1st Line) I then ran through all the tests I could think of twice without finding a single fault.
    After 45 minutes I had to report to the staff that I couldn´t even find any failure symptoms. Apart from two cable connections being loose (presumed undone by by previous student on this fault during fault-finding and not afterwards tightened properly) and rectified before starting any checks, I couldn´t detect anything wrong.
    Turned out only one of the loose connections was left over from the previous student, the other was the intended fault and would have caused the GPS to misbehave.
  14. I have had a similar problem with the PTT's for CR2 but not on a wagon. Was it always the same correction to be applied that went wrong? could be an error in crew drill in not ending in elevation? I admire your (delete as applicable) Persistence/tenacity/geekery/delayed mental-ism.
  15. Do we still end the lay in elevation? I thought that went out with CR2, and it only ever applied to engagements using rev modes (Hand Controls) due to elevation backlash on a gun to sight slaved system. Surely with sight to gun slaved system with a full systems engagement there would be no need to do that? The add/drop correction routine was for full systems use, in rev modes that correction would have been carried out by the gunner. Not being fully CR2 trained I'm happy to be shouted down, out of interest if nothing else but does the FCS always end the final displacement of aiming mark in elevation as a default?
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