Doesn't necessarily need to be a massive gradient to be significant.

Operationally important for assessment of when and if one ought to take the higher cruise level ...

AB use the term in here :
http://www.airbus.com/fileadmin/medi...APPR-SEQ01.pdf

j.t.:


I admit total defeat. :)

All those years I flew the line the company spoon-fed me optimum routes and altitudes based on winds aloft.

They gave us lotsastuff .. which was all very good ... but, with forecasting which left a bit to be desired and in the GAFA navigational wilderness, we ended up having to make up most of what we did on the fly, as it were ....

I never flew the Diesel 9 but I gather that the boys on that were always interested in fuel remaining and paid much attention to wind gradients and just what level they ought to be re the latter to maximise the former.

High Fly 33.

It seems to me that gradients are used for climb and FPA (degrees) is used mostly in respect of descent. They are two methods of arriving at the same answer. One is rise over run, and the other is opposite over adjacent.

Wind is a red herring, but you understand that part of it anyway. Wind gradient, which of course is an unknown value that aint included in the ATIS, is splitting hairs!

j.t.

I flew the DC-9-10 as my first PIC airplane. The longest leg was probably 1:30 or so, so winds aloft were far less important than Boston to Los Angeles on a 1011.

Winds aloft were a big deal; wind gradients were in the dust of the details.

It's often very easy to notice the effects of wind gradient during the last 50 to 100' of descent in a light plane, sailplane, or ultralight aircraft. The sink rate increases quite dramatically due to the strong wind gradient often found near the ground. It's a very real thing. It's also not unusual to notice a higher-than-normal climb rate immediately after takeoff, for the same reason. Physics are no different in fast jets but you might need a stronger wind to get a noticable effect. On the other hand in a steep fast climb you are obviously moving up through the wind gradient a lot faster than you would in a light plane.

The effects of wind gradient on glide angle, as opposed to sink rate, may be a little more subtle. Still, if you have an autopilot controlling the glide path w/ elevator and airspeed w/ autothrottle, it seems that more power will be applied whenever the a/c is descending through a strong wind headwind gradient, no?

Yes, I'm sure all of us here understand the nature and effect of wind gradients, but in the context of obstacle clearance flight planning or descent profiles it is miniature you can ignore. It has nought to do with the OP's question.

It seems not "all" understood-- read the posts -- but perhaps they do now! Or are motivated to learn more.

I have had more than one working "professional pilot" tell me wrong things about the wind, so I say it's fair game for discussion. Yes it was not the original question.

From Boeings Jet Transport Performance Methods: Chapter 22
EASA regulations
The European Aviation Safety Agency, in its Certification Specifications for Large Aeroplanes CS-25, Book 1 Subpart B, contains precisely the same climb requirements as the FAR25 requirements quoted above. CS 25.121 corresponds to FAR Part 25 Section 25.121.quoted above. Thus the requirements to both FAA and EASA/JAA operators are identical.


wind corrections to required gradients
We said earlier that the gradient requirements quoted above are unrelated to the requirements for obstacle clearance; instead, they’re a means of mandating a minimum acceptable level of surplus energy during a takeoff. Because of this fact, the gradients specified are zero-wind gradients – they are not corrected for the wind expected during the takeoff. The airplane’s surplus energy state is not a function of the wind encountered during the takeoff.


Obviously, however, when we’re concerned with obstacle clearance we must consider the wind since the wind affects the airplane’s path over the ground and hence its ability to clear any obstacles.

Greetings Elcol, Thank you for a solid reference , this is precisely what I was looking for;much appreciated,

I appreciate all contributions to this thread, I have been taken by surprise over how many differences of opinions thoughts and so forth there is on this subject matter.. It is indeed a interesting discussion,

"clear as mud" is a term that comes to mind when speaking about aircraft performance, hopefully by-gaining a deeper understanding , the sediment will settle and clarity will yet again prevail,

Best Regards
HIGHFLY33

Just to clear up a previous post that dismissed the CLTOM/WAT limit as an irrelevance. The purpose of this graph is to ensure that the aircraft complies with the most severe gradient requirement (normally segment 2) of the NTOFP as specified in CS25. There is no wind input into the graph because they are still air gradients.