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A better understanding of "Step" please....


Guest cliffie1931

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Guest cliffie1931
Posted

1. I had set my Cruise Altitude in the FMC to 28,000 ft. 2. The VNAV page showed CRZ ALT FL280 Step to 3003. The Legs page showed FL3004. I set the Altitude box to 31,0005. After reaching FL28 the next waypoint on the Legs page showed that we should be at FL300 when arriving at it in 44 miles.6. However as I approached that Waypoint the Legs page showed the target of FL30 constantly reducing until we reached the Waypoint still at FL28.I assume that the FMC calculated that FL30 was the most efficient. If that's so why didn't the aircraft continue to climb to FL30?Cliff

Posted

>I assume that the FMC calculated that FL30 was the most>efficient. If that's so why didn't the aircraft continue to>climb to FL30?Correct. FL300 was calculated to be the optimal altitude. But you pilot must initiate the climb. Step-climbs do not happen automatically - that's how it works on a real 747.Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2http://www.precisionmanuals.com/images/forum/747400.jpghttp://www.hifisim.com/images/asv_beta_member.jpg

Posted

Meaning that you must press the MCP altitude knob after entering the new cruise altitude. The plane won't climb alone! Remember also to select on PERF INIT how big your steps are. ICAO gives you 4000 ft incremets. If you wish for less simply put it in there. For example in single way airways in RVSM you can sometimes climb at 1000 ft increment further nearing your optimal vertical profile. The ideal would be for the aircraft to "cruise climb" at ridiculously low vertical speeds so as to always be in the otpimal flight level. That doesn't happenbecause of ATC spacing and such. Sorry if I wrote for more than you asked for or about things you knew. I got carried away. Best Regards,Victor Limahttp://www.precisionmanuals.com/images/forum/800driver.jpg

Guest cliffie1931
Posted

Michael and Victor Lima.................thanks so much.Now I understand and your explanations make sense to me.That's another "problem" solved thanks to you two. Enjoy your weekends.Regards,Cliff

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