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cuirassier

Altitude Difference Problem.

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Just about run out of paths to investigate. Starting from C & Dark, the Captains altimeter reads lower than FO and Standby. I have checked the options to adjust all together to 29.92 etc., but cannot bring Capt. up to norm on ANY 737NGX. If the baro or radio are set the same the Captns. is still low. I've read what I feel is relevant documentation but I'm stumped. Any pointers would be gratefully taken on board and stored. By the way, the problem increases in leaps and bounds the higher the altitude.

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You you have the altimeter set to standard? What do you mean by setting the radio altimeter the same? That is for minimums, have you tried pressing B?Dan.

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Dan. I meant that I set all parameters the same on the instruments. I have just pressed B and Capt. reads 80 and FO and Stby read 200 at 30.02 in.

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Dan.I meant that I set all parameters the same on the instruments. I have just pressed B and Capt. reads 80 and FO and Stby read 200 at 30.02 Sorry about pressing wrong button Pete

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Are the pitot covers on? This could give erroneous readings in real life! Don't know if it is simulated though.So the altimeters are all at 30.02? In green underneath the altitude tape? Also none are set to standard? Pitot covers off? What electrical power do you have? I'll have to check but that could be an issue.Dan.

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Pitot covers are off. Power is coming from engines with all appropriate switches closed as far as I can tell. Barometric of 30.09 ( My mistake first time ) gives readings of 70, 230 and 230 for FO. If STD is selected, readings of 20,70 and 70 are given.. The 30.09 in green and STD in yellow. DC amps - 0DC volts - 28AC amps - 30AC volts - 115 at 400c/s The pressure is rising as I'm writing. It's gone from figures above at 30.09 to 80, 270 and 270. Pete

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It looks like one of your altimeters is set to standard ( the yellow one ) this would give an altitude difference of about 150ft ( roughly what you are seeing.Press the standard button and then adjust baro setting, the White 30.09 is a pre selected value only.

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Could this be a subtle equipment failure? Have you tried performing maintenance on the aircraft? Martin Boehme

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Dan I set all instruments to EITHER 30.09 (green) OR STD (yellow). I set standard and adusted baro setting individually and in unison, but it made no difference to the readings. The readings set at 30.03 ( button B ) are now 100, 320 and 320 left to right. I think the problem is deeper than I thought, but I'm extremely grateful for the help you've given. I'm going to get some fuel for myself now, but again many thanks anyway. If you think of anything else while I'm gone I'd be all ears. Thanks, PeteMartinI haven't tried that, I'll give it a go and post the outcome. Thanks, Pete

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Dan and Martin I found the answer on the LH panel of the Overhead. The altitude reading came back to normal on Captains side if I changed control switch on DISPLAYS CONTROL PANEL to BOTH ON 2. I'd of thought it should be in normal. Anyway, at least I can fly normal again. Many Thanks for the responses, Pete.

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They should be set to normal. The airplane has 2 ADIRUs (air data innercial reference units). Plainly speaking they are your pitots, static ports, and inercial reference units... on steroids. If one Air Data Module reads 200ft above the other ADC, then there's a problem. And setting all instruments to be fed by ADIRU1 is only the solution when you are safely on the ground. Anyone's got a MMEL?

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With the display control panel set to both on 2, all you are doing is using a single EFIS control panel for both displays. That will not fix the fault, just hide it. Glad you can go flying anyway, have you read the tutorial?Dan.

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Dan and Flexman I've flown the tutorial and many more over the last decade, but I haven't come across this problem before. I can't fly according to minimum equipment but at least I can do everything else. I covered and uncovered pitots, but it didn't make any difference to the reading, no headwind maybe? I'm assumming it's a bug because I've checked for faults and carried out maintenance on the appropriate sections. I don't think they'll let me pull the fuses to check them. Many thanks anyway. Pete.

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In an actual aircraft, when the "odd man out" altimeter reads significantly lower than the other two, this would indicate either a malfunctioning ADIRU, or a blockage in the associated static system. (A blocked pitot tube would affect primarily airspeed). If it happens only when the aircraft is pressurized, it would indicate that there is a leak in the static line at some point within the pressurized part of the fuselage. (In either case the associated airspeed indicator would read low too). Either PMDG has implemented a blockage/leakage failure mode for the pitot-static system, (or ADIRU which has lost its calibration), or there is something corrupted in your installation. If you've tried clearing all failures without success, then it's probably the latter...

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Is your settings on FSX set to "US metric systems"? If not, try that and make sure your Display Control Panel is "NORMAL".

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Pete, Sorry about the "read the manual" advice, just can't tell somebody's experience easily (especially when using an iphone!). Sounds like most option have been covered, maybe a fresh install or a support ticket is in order? I take it that you switched off service based failures in an attempt to localize the problem? Also did you go through all the failure /maint options, including FSX? You probably have, I can't think what it is...... Dan.

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Which of the altimeters is closest to field elevation when set to QNH? I forgot to ask, because you might actually be within limitations, at which phase of a flight are you when you find the difference?The allowed inflight difference for RVSM between CAPT and FO is 200ft.

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According to the OP the difference was between 50 and 220ft. This varied with the pressure.

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As already mentioned I think this is the altimeter settings in FSX. There are 3 options, check them out. Happened to me already. If it is a simulated fault, you can go into the PMDG menu and see which faults are current. But I dont think there will be any..

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x3, as mentioned...Is your settings on FSX set to "US metric systems"? If not, try that and make sure your Display Control Panel is "NORMAL".

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Brayton and Ian Just checked the settings in FSX and you're absolutely on the money. As soon as I changed to Hybrid or US ft and inches it came back to 'normal' supply across the board.Must admit I don't know how it came to be in metric but it sure as heck aint now. Many thanks to all contributors,and as my first time on ANY forum I am really impressed with the help offered. Pete

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