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Problem with primary instruments

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Hi everybody,I just encountered a funny problem I never had before.Flying from NFFN to NSTU, after about 30 minutes I had an instrument failure of PFD, HSI, VOR and VSI. FMC was ok, no electrical or other failures. Repair malfunctions did not work. It told me everything was alright.I started up FS 2002 with the default 737 - just in case...I also switched the dead battery option in FSUIPC 2.85 to zero - I have no idea what happened.It was the very first time I had such a problem, after a few hundred hours with PIC. Therefore I'm a bit helpless.If it helps:P4 1.5 GHz, 512MB RAM, GForce3Any ideas?Regards -Stefan

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Guest Martin

A more detailed explanation would (or at least could) help here. Did the displays just go black or did they display some kind of warning/failure flags? In the latter case it could be that you accidentally switched off one of the IRUs. That doesn't account for the VSI and VOR failures though. Exactly what do you mean by VOR - is the the RDMI or the actual radios? Was the EICAS still working?MartinIt's a lot like life and that's what's appealing

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Hi Martin,the displays showed the warning flags as if I switched off the electrical supply. But I didn't. Same was with RDMI and VSI. They just showed "off". The EICAS was working normally, IRUs were on. Everything on the overhead panel was normal for a routine flight.I didn't switch anything for about 4 or 5 minutes and all of a sudden the mentioned displays went out. Strange.

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Guest Ian_Riddell

"That doesn't account for the VSI and VOR failures though."Actually, it does, Martin. The IVSI requires the IRS's for vertical acceleration (short term vertical speed) and the VOR displays require IRS magnetic heading reference data.It does sound like the IRS's self destructed.A lot of unexplained events on real aircraft can be put down to Neutron Single Event Upsets and other events related to high speed particles from outer space smashing into the componentry inside the aircraft's computers (in Stefan's case though, it may have been for other reasons... unless he was living on top of a mountain... or next door to a particle accelerator). The FMC and the Flight Control Computers (autopilot computers) seem to be the most susceptible, but instead of generating erratic commands, the error detection circuits in these computers pick up the faults and either try to resync the data with the other FMC (in the case of the FMC's) or simply trip the A/P offline (in the case of the A/P computers). I believe there is work in progress which will help protect computers from this kind of damage.I mention high altitudes (mountains) because the air is thinner and there is less protection from these high speed particles. One of the risks of being a pilot/spaceman is that your body is also at risk from these particles. The body, of course, is auto repairing..... up to a point. Too many meetings with these particles may damage your health permanently.Hope this helps.Cheers.Ian.

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Next time I am looking for an excuse for being late for work, I will say I encountered a "Neutron Single Event Upset"...that should keep 'em guessing for a while ;-)Very interesting post!Rob.

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Guest Martin

>Actually, it does, Martin. The IVSI requires the IRS's for >vertical acceleration (short term vertical speed) and the >VOR displays require IRS magnetic heading reference data. Aw crap! :~P:-lolBut the question is: Is this modeled in PIC? Not as far as I know. For the VSI to fail you have to use the FS system failures menu (but I might be wrong - after all I fly most flights with everything running like it should).You mention "short term vertical speed". Does that mean there is also a "long term vertical speed"? If so, can the VSI somehow use that for reference instead? If not, do you have to resort to the standby altimeter for vertical speed information if the IRS fails?MartinIt's a lot like life and that's what's appealing

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Guest Ian_Riddell

>But the question is: Is this modeled in PIC? Not as far as I >know.I just checked, Martin and it appears to be to some extent (If you mean the IRS input to the VOR/compass and VSI, just look for the appearance of the flags when you switch off the IRS's.Note that the VOR/compass displays on the Captain's EHSI are driven by the Left IRS... and the F/O's EHSI displays (which we can't see) are driven by the Right IRS. However, the Captain's RDMI compass/VOR is driven by Right IRS, and the F/O's RDMI VOR/Compass is driven by the Left IRS. This doesn't appear to be the case in PIC. The reason for this mixture is that it makes compass errors easier to see (you don't even have to look at the other pilot's instruments to be aware that there is a discrepancy).Note that the Source Select/ Instrument switching switches to the left of the Captain's RDMI in PIC (if they were all operative) would allow you to use a different IRS source for your displays, should one fail. From memory, though, the single operative switch in PIC allows you to do more than you can on the real aircraft, so you may be able to recover some of your instrumentation by using this switch.Re the VSI, the OFF flag appears when you switch off the Left IRS (this is modelled in PIC)>You mention "short term vertical speed". Does that mean >there is also a "long term vertical speed"? If so, can the >VSI somehow use that for reference instead? If not, do you >have to resort to the standby altimeter for vertical speed >information if the IRS fails? As I understand it, the ADC's (Air Data Computers) provide long term vertical speed (The IRS's have to measure thousands of up and down movements throughout a flight (minor ones at least) and may slowly build up errors to the point where the IVSI may show a constant climb or descent, even though you are flying level (The ADC's provide a long term correction to sort of "zero" the instrument). BTW, the ADC's use simple air pressure sensing to compute Vertical Speed... not unlike your average Cessna. From what I recall seeing on the real 767, a flag will appear if either IRS or ADC data is invalid/missing (but I'll have to confirm this).Anyway, that's much too much "brainstorming" for one day (at least before my breakfast time ;-)).Cheers.Ian.

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Guest Martin

>Anyway, that's much too much "brainstorming" for one day (at >least before my breakfast time ;-)). It's now past my substitute-breakfast, lunch, caffeine, caffeine, dinner, dessert, and caffeine time. ;-)So, is it not possible to have a working VSI if the IRS is totally inoperative? Is there a way to "by-pass" the IRS and get the information directly to the VSI? (Standby instrument source or something - didn't find anything on it with a quick look in the manual.)Martin767 fetishistIt's a lot like life and that's what's appealing

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Guest Ian_Riddell

>So, is it not possible to have a working VSI if the IRS is >totally inoperative? Is there a way to "by-pass" the IRS and >get the information directly to the VSI?I'm not 100% sure about this, Martin, but even so, if a flag popped into view on my IVSI because of an IRS failure, I would be very hesitant to put a lot of trust in it. From memory (poor as it is), the new combined TCAS/IVSI digital displays, I think, don't even show a pointer in the absence of IRS data (I'll double check on this when I get back to work).http://www.ozemail.com.au/~iriddell/767/Tcasivsi.jpgI guess because there are two instruments, and three IRS's, there is enough redundancy built in to not worry Boeing's designers. I do find it odd, however, that there is not a standby IVSI. Still, I suppose the pilots can always figure out their vertical speed from their altimeters and chronometers. E.g. 500' in 15 seconds = 2000fpm ;-)Cheers.Ian.

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