Question on turbulent air penetration speed

[nevinch]

I just upgraded to Weather Maker Pro 3 and my first flight with this engine saw me departing Darwin Int'l (YPDN). It makes a HUGE
difference. I knew from the METAR that the weather would be pretty exciting. So, I take off and sure enough I'm dealing with all kinds of
turbulence. The pax fear level rose to 30%...never seen that before with default MS weather.

So, the question then....if you're in that kind of weather below 10,000 ft in a 767-300 is it safe to assume you should lower your climb
speed? I noticed while being bumped around that my Kias wasn't all over the place like it used to be but rather it would slowly climb up
and down...sometimes getting near the 250 mark.

Hope some of this makes sense?

Chuck

[silo]

either that or ask for permission to exceed 250kts below 10000.

[rchwallace]

I am not totally sure what you are asking but your speed in that case may depend on your aircraft weight. If you are heavy ( I assume you
are using the Level D 767) then your clean speed may be close to 250. As a general note these aircraft have sufficient buffet margin at 250kts below 10,000ft for turbulent conditions on departure. You would not wish to reduce your speed below this in turbulence as in a jet you also need the low speed margin.... and at 250kts you are getting pretty close to wanting to go faster for that added comfort and margin.....

As a note I fly the LD767 and have had a few occurances where the aircraft exceeds the 250kts below 10000 in turbulence and have not
been penalized but they dont occur for very long.

Regards



Post Edited ( 08-02-05 04:53 )

[psolk]

I have seen the same thing. As long as you do not exceed 260, I do not seem to get penalized. Sometimes the VNAV on the LVL-D will go a few past 250
before it slows down and catches...
-Paul

[nevinch]

You guys hit the nail on the head for me....thank you very much. That is precisely what happens.....turbulence more notably it happens but
even in clear conditions the a/p system will sometimes exceed 250. If it ever comes close I've gotten in the habit of asking for clearance
which I usually get.

It's on the descent path.....if I come in hot and ask for clearance to exceed 250 they will deny it most often.

Anyways, I've pretty much set my blw 10,000 ft spd to 235 and now it rarely exceed the limit anyhow.

Thanks guys
Chuck

[psolk]

Chuck, What I always do with the LVL-D is set my VNAV alt on descent to 10500 It only takes about a minute to level off, bleed my airspeed and then
continue descent.
Works for me,
-P

[rchwallace]

Hey guys......

I thought I would give you a bit on VNAV. The Level D sim is very realisitic so the VNAV behaviour is well moddeled.... anyhoo. I will keep
it simple but maybe add some stuff that may help you.

If you are in path (VNAV PTH) in the decent the aircraft will maintain the decent "path".... it will keep the aircraft decending at a
programmed path from one constraint to the next. For the 250 and 10000ft area this can be a problem if the winds or path are not
working quite right for the aircraft........ what I mean by this is that when in PATH the aircraft will not protect your speed...... its priority is the
path. It has programed its decent point etc etc lets say for an idle decent but with the different variables it will have to vary your speed
from the programmed speed to maintain the path. Sometimes the winds can be quite strong and will vary your path extensively and as a
result the aircraft will not be able to maintain the speed. This happens quite often and the aircraft may start going slow or fast dependind on what the winds are doing..... To fix this you either need thrust if slow or speedbrakes if fast...... OR

You can open the speed window on the MCP and put the decent mode into VNAV SPD this then changes the priority of VNAV to decend to
your cleared altitudes at the speed in the window..... it will hold the speed and varry the decent path to reach the desired decent altitude.
This can result in a longer decent and if ATC are vectoring you in close you could end up slightly out... but I use this in the A/C when
cleared an ATC speed. VNAV is programmed but I keep the window open as it will decend on speed rather than path. FLCH will do the
same in that it will keep a good speed for you..... initially it will go into IDLE but after will go into HOLD. (For the autothrottle) I use the
precision thrust levers (PFC) and with level D I am able to adjust the thrust setting when the AT mode is in HOLD as in real aircraft.

Dont know if this helps at all with the problems stated but.........

Regards



Post Edited ( 08-02-05 04:56 )