Early Descent to promote engine life.
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those conditions are normally catered for by planning the descent winds
Per Ardua ad Astraeus
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Me too - see post#4. We are getting a bit confused on this thread now - I am merely trying to point out that there is no LOGICAL reason why there should be an 'overspeed' attempt in the case put by esr in post #19 . You will see my distrust for the Boeing VNAV descent in post#4 and I am at the stage where I do not bother to programme descent winds at all now, but use L Chg or v/s if required to correct any profile diversions, having descended at MY chosen point for the prevailing wind profile. As said there, there are anomalies in the 737 pitch/speed algorithms which obviously do not help.
Never thought of beginning an early descent due to engine cooling issues.
Re: post #4 I recall that Mr Boeing issued a bulletin back in about 2004/5 outlining some changes to the VNAV PATH descent profile logic. Cannot remember all the details but the reason for the changes was to address overspeed issues.
IMHO it is still a problem when leaving cruise altitudes above about FL350. I have no particular formula or numbers to hand, but if my cruise speed is "only" about 10kts below the barbers pole, then I initiate an early descent in the hope that that by the time I am at the thrust levers closed portion of the descent I am 20+ Kts below the barbers pole. (CI=30 BTW).
Initiating early descents is not the most efficient way of operating but does ensure you are not called into the office, for a hat on, NO tea and biscuits, type interview!
Re: post #4 I recall that Mr Boeing issued a bulletin back in about 2004/5 outlining some changes to the VNAV PATH descent profile logic. Cannot remember all the details but the reason for the changes was to address overspeed issues.
IMHO it is still a problem when leaving cruise altitudes above about FL350. I have no particular formula or numbers to hand, but if my cruise speed is "only" about 10kts below the barbers pole, then I initiate an early descent in the hope that that by the time I am at the thrust levers closed portion of the descent I am 20+ Kts below the barbers pole. (CI=30 BTW).
Initiating early descents is not the most efficient way of operating but does ensure you are not called into the office, for a hat on, NO tea and biscuits, type interview!
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- I'd go with that, Capt C, except I would take the TOD, watch it like a hawk and at the first sign of naughtiness send VNAV to the 'naughty corner' until it is feeling better. The possibility of overspeed being a 'problem' reduces greatly as the IAS limit separates from mach although I have seen the odd lady 'pick up her skirts' and make a mad totally unexplained and illogical dash for the barber's pole at lower levels. It seems there is a disconnect between the pitch attitude the FMC calls for and the resulting change in speed. Quite often it is 'difficult' to persuade the machine to lift the nose when a lower IAS is demanded, requiring either manual or CWS pitch intervention.
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i find that in the 737-400 sometimes it might overspeed but that is because it is not as smart of a system as the 800 which has never overspeed. i usuall decend at 325kt and a mach equal to cruise. you can always put in forcasted winds in the decent page to help it out as well, but i rarely do that. V/S, IMO should only be used when decending only a 1000 feet or so. other than that vnav all the way then leval change in the terminal area. too many pilots don't trust vnav only because they don't understand how to use it. the box will do exactly what you tell it. nothing more or less.
