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I have a question about a document published by the Association of European Airliners. The name of the document is “Long Range Aircraft - AEA Requirements.” In the Appendix titled "Definitions and Inputs for Range and DOC Calculation," paragraph 1.1 (“Flight Profile for DOC and Range Calculation”) at Note c) we can read the following recommendation:

Cruise, and completion of step, shall be at that altitude at which the potential rate of climb, at initial cruise weight-climb speed, is 500 ft./min or more

I don't understand the meaning of that sentence. What’s the definition of “weight-climb speed?”

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  • $\begingroup$ It seems to me that you are misreading the note, which surely refers to "initial cruise weight and initial climb speed," but I'll move your question over to our site for aircraft pilots, mechanics, and enthusiasts who will be better able to confirm if this is the case. $\endgroup$
    – Air
    Commented Feb 10, 2016 at 16:54
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    $\begingroup$ DeltaLima gave you a precise, well worded answer to your question. If you are further interested in the subject, I would invite you to ask a follow on question, something like, why is it not a good idea to climb higher than a level at which you would have a cruise weight-climb speed less than 500 ft/min $\endgroup$
    – Terry
    Commented Feb 10, 2016 at 18:53

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A cruise weight-climb is a climb segment during the cruise phase of the flight to achieve a higher flight level that was previously not reachable due the weight of the aircraft.

Long range aircraft cannot climb as high initially because of the weight of the fuel they carry. Their operating ceiling is power limited. As the aircraft burns off weight during the flight, the drag decreases and gradually excess power becomes available for climbing.

This recommendation is not to start climbing to the next level until a vertical climb speed of 500ft can be maintained at the new level, at the initial cruise speed after that weight-climb.

For example, if the the cruise starts at FL270, and one wants to climb to FL290 for a cruise at Mach 0.80, the weight-climb should not start before the aircraft can maintain a 500 ft/min climb at Mach 0.80 at FL290.

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