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Wolfko

Can somebody please explain this?

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Here is a link to a airliners.net photo on which I have 2 questions. As you can see on the AP altidude window 35400 feet are set. Why this kinda odd number?Further the left altimeter displays 35400 feet as current altidude, whereas the right altimeter shows 35740 feet. Why this difference - as far as I can see the pressure on both altimeters are set to 29.92 (1013)?http://www.airliners.net/open.file/501041/L/Wolfgang

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I would say the altitude was a request from the aircrew either for cruise efficiencey or turbulence.As for the altimeters, the capt's alt. runs off the capt's air data computer (ADC) and the standby is strictly a pitot static instrument. The ADC is a very precise unit and is rarely out by much. The pitot static stdby. alt. suffers from hysteresis, and therefore has a higher error tendencies. They may have been cruising higher and just descended and the altimeter is lagging. Otherwise a 350 ft error is high but not unheard of for a stdby instrument at high altitude.JohnBoeing 727/737 Mechanic

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No idea why they are flying at that altitude. However, the left, right and standby altimeters of these sort of aircraft are fed from three separate pitot-static systems. Each system will usually show slightly different readings and as long as the readings between the three are within specified tolerances, the system is good. The differences between them are magnified as the aircraft flies higher which is why cruise altitudes above FL290 are separated by 2000', unless in RVSM airspace that maintains 1000' separation. But only aircraft with more accurate RVSM qualified altimeters are allowed there.

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It's flying in Chinese airspace, and they use metres there. 35,400 ft = roughly 10,800 m.Martin767 fetishistIt's a lot like life and that's what's appealing

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Thank you for your expertise, guys!Wolfgang

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