B777 early descent (Cruise descent) and vnav pth
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B777 early descent (Cruise descent) and vnav pth
Hi there,
Understand if it's within 50nm from TOD, vnav will adjust the descent profile to capture vnav pth. But what about if ATC descends us say 70nm from TOD, the new cleared level will be our cruise level and there will be a new TOD? How do I understand this new TOD and say if ATC clears us down again 60nm from our new TOD? If I set the new cleared level and hit the altitude knob, what can I expect?
Thanks for your time.
Understand if it's within 50nm from TOD, vnav will adjust the descent profile to capture vnav pth. But what about if ATC descends us say 70nm from TOD, the new cleared level will be our cruise level and there will be a new TOD? How do I understand this new TOD and say if ATC clears us down again 60nm from our new TOD? If I set the new cleared level and hit the altitude knob, what can I expect?
Thanks for your time.
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Let say ATC keeps us on a continuous descent whereby every cleared level is >50nm from the new TOD, the aircraft will never get on vnav pth and there won't ever be a vnav pth indicator? I'm not sure if this will ever happen but i'm just exploring options.
Understand I can always revert to basic altitude height crosscheck, but I'm just thinking of my options.
Yep, it’s possible, you could do it in FLCH and adjust the speed, or set a V/S or FPA to match what it tells you on the DES page to make it a little more efficient by taking out the level segments.
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Thanks. Is there ever a need to input a "cruise altitude" in the clb page?
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Let say ATC keeps us on a continuous descent whereby every cleared level is >50nm from the new TOD, the aircraft will never get on vnav pth and there won't ever be a vnav pth indicator? I'm not sure if this will ever happen but i'm just exploring options.
Understand I can always revert to basic altitude height crosscheck, but I'm just thinking of my options.
Understand I can always revert to basic altitude height crosscheck, but I'm just thinking of my options.
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It is quite likely to happen, especially flying into busy terminal areas at peak times, You will get early step descents even 150nm and more from your TOD. Just keep updating regularly Your cruise altitude with every step till You are within 50 NM of Your TOD and from there onwards You will transition from cruise to early descent and have an accurate VNAV path.
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I'm used to the 744, not 777, but...
No, you do not need to update your cruise altitude in the CLB page. In a cruise descent, it will update automatically when you dial down the MCP altitude and push the button to initiate the VNAV descent.
Also, if you think you are going to get a continuous descent from ATC, just use the DESCEND NOW button on the VNAV DESCENT page to force the FMS into descent logic.
No, you do not need to update your cruise altitude in the CLB page. In a cruise descent, it will update automatically when you dial down the MCP altitude and push the button to initiate the VNAV descent.
Also, if you think you are going to get a continuous descent from ATC, just use the DESCEND NOW button on the VNAV DESCENT page to force the FMS into descent logic.
