Vnav Descent Again.....

Hi,

first i want to thank you, i was not remembing this section in ini file for
:[VNAV], DescentSpeedControl=On

So i entered "On", value and i made a very nice test flight from LGTS
Makedonia to LGKR Kerkira airport with "bad" weather!!


But i had a problem : Even if in T/D i dialed a lower altitude, from 28000
to 12000 and i was with VLAN & LNAV modes, after the T/D announced from
PmSounds, the aircraft didn't start the descent and i had to push the
descent now command in FMC/Descent page.
In Eicas screen i had the CRZ indication and i could not command the
throttles of course, as i was in FMC Speed.

No errors in widefs log files.

I will retry a second flight, but i just post it, in case enyone can
imagine
a possible reason for this, or if anyone has the same problems.



regards


Eddie

> first i want to thank you, i was not remembing this section in ini file
> for
> :[VNAV], DescentSpeedControl=On

Good.

> But i had a problem : Even if in T/D i dialed a lower altitude, from
28000
> to 12000 and i was with VLAN & LNAV modes, after the T/D announced from
> PmSounds, the aircraft didn't start the descent and i had to push the
> descent now command in FMC/Descent page.

How much did it display in NM to the Top Of Descent on the CRZ page when
that happened?

Ciao

Enrico

Enrico,

> :[VNAV], DescentSpeedControl=On
> Good

Scratching my head here, but you must be aware that the setting does NOT
change anything.
When DescentSpeedControl=Off is set the pilot should control the descent
speed with throttle and the A/T should not be interfering. But it DOES
interfere and MCP SPD is getting clearly annunciated...

regards
Andras.

Hello Andras,

> interfere and MCP SPD is getting clearly annunciated...

What do you mean by anunciated... you do not want it to be anunciated?

I will check whatever comes my way with the MCP when I come back, I am
currently doing something completely unrelated to that.

The DescentSpeedControl=Off is the one that should make the difference, i.e.

once you set the thrust lever to IDLE and the thrust has gone back you
should be able to compensate for thrust yourself.

Also, please note that this does *not* apply when making an early descent
and the vertical speed is locked at 1000 ft/min (or 1250 ft/min on the
747).

Ciao

Enrico

"Andras Kozma" wrote in message
news:269222.53400@wb.onvix.com...
> Enrico,
>
>> :[VNAV], DescentSpeedControl=On
>> Good
>
> Scratching my head here, but you must be aware that the setting does NOT
> change anything.
> When DescentSpeedControl=Off is set the pilot should control the descent
> speed with throttle and the A/T should not be interfering. But it DOES
> interfere and MCP SPD is getting clearly annunciated...
>
> regards
> Andras.
>

Hi Enrico,

> What do you mean by annunciated... you do not want it to be annunciated?

During the path-descend the MA shows the ARM annunciation (talking about
737 here, might be different with others), and it doe it initially. But
after some time it reverts back to FMC SPD, that I tried to say, perhaps it
wasn't clear, sorry.

> I will check whatever comes my way with the MCP when I come back, I am
> currently doing something completely unrelated to that.

Great, please have a look when got the time, this is the a most disturbing
thing when trying to fly on the 'realistic' side...

> The DescentSpeedControl=Off is the one that should make the difference,
> i.e.
> once you set the thrust lever to IDLE and the thrust has gone back you
> should be able to compensate for thrust yourself.

In theory, yes. That's what I was trying to explain. But the switch is not
working. The behavior remains the exact same regardless of this ini switch.

> Also, please note that this does *not* apply when making an early descent
> and the vertical speed is locked at 1000 ft/min (or 1250 ft/min on the
> 747).

I would exaggerate if I said I understand what you mean...
In PATH mode the A/T should be in armed mode, hence the pilot is able to
adjust the throttle manually. The problem is that it reverts to FMC SPD, so
no manual input is possible.

regards
Andras

Hi Enrico,

Sorry, I'm back to this nasty problem again...
I tested the entire scenario this afternoon. At least I was able to nail it
down.
Yes, the routine (or whatever it is in this case) doesn't work. In
VNAV-PATH
mode the pilot doesn't get the throttle control back. It momentarily stays
in ARM mode, but then reverts to the unwanted MCP SPD mode and no manual
control possible anymore. Needless to say that it shouldn't be like this,
and frankly (in the 737 at least) it makes a normal VNAV-PATH descent
almost
impossible.

I tried out all PMmcp versions back to the beginning of this year, and
found
that the last version it worked PERFECTLY with, was mcp379, the exe dated
2.29.2004.
It just works as it should, in both path and speed modes. So something got
broken in one of the early-spring 2004 versions and it stayed the same.

Frankly, I wonder, how it was possible, that many of our fellow Boeing
flyers didn't notice it for almost a year...
Please have a look whenever possible, this is a very important thing for
reality...
Oh yes and I understand what you have said, that it does *not* apply when
making an early descent and the vertical speed is locked at 1000 ft/min,
yes
true, but that is a special case. What I'm talking about is the plain old
general vnav-path descent.

regards
Andras

Hi Andras,

> mode the pilot doesn't get the throttle control back. It momentarily
stays
> in ARM mode, but then reverts to the unwanted MCP SPD mode and no manual
> control possible anymore. Needless to say that it shouldn't be like this,
> and frankly (in the 737 at least) it makes a normal VNAV-PATH descent
> almost
> impossible.

Just for you info. The principal in the B744 is the same. There are just
other annuctions in the PFD thrust box.
Instead of ARM, IDLE should come up during the time the trottles are coming

to idle and then HOLD must be annunciated, which means that the servos are
now disconnected from the trottles and that the pilot can intervain
manually. Of course A/T stays on. (At present stage this is not yet
implimented in PM, but I suppose now that we are come more and more to type

specific things in PMSystems, this important AFDS annuciations will follow
too).

But also for the B744 the VNAV logic doeqn't seems working (Sorry I didn't
test it for a long time as my B744 project was underconstruction).

Ciao

Michel
--
Michel VANDAELE
Member of the board FSCB
EBOS2002 Designteam
My B744 simulator project
http://users.pandora.be/michel.vandaele/sim1.htm







> I tried out all PMmcp versions back to the beginning of this year, and
> found
> that the last version it worked PERFECTLY with, was mcp379, the exe dated
> 2.29.2004.
> It just works as it should, in both path and speed modes. So something
got
> broken in one of the early-spring 2004 versions and it stayed the same.
>
> Frankly, I wonder, how it was possible, that many of our fellow Boeing
> flyers didn't notice it for almost a year...
> Please have a look whenever possible, this is a very important thing for
> reality...
> Oh yes and I understand what you have said, that it does *not* apply when
> making an early descent and the vertical speed is locked at 1000 ft/min,
> yes
> true, but that is a special case. What I'm talking about is the plain old
> general vnav-path descent.
>
> regards
> Andras
>

Hi Michel,

> Instead of ARM, IDLE should come up during the time the throttles are
> coming to idle and then HOLD must be annunciated, which means that the
> servos are
> now disconnected from the throttles and that the pilot can intervain
> manually. Of course A/T stays on. (At present stage this is not yet
> implemented in PM, but I suppose now that we are come more and more to
> type specific things in PMSystems, this important AFDS annunciations will

> follow
> too).

In the 737 when a 'normal' VNAV PTH descent is done the first (and short)
annunciation is RETARD and very soon it reverts to ARM. What I understand
from your description, the 747 is the same just the annunciations are
different. But those can easily be changed in the aircraft file, so in case
the 'normal' routine worked again (and I truly hope Enrico will just need a
short look to make it work again - as it WAS working once) the very same
logic stands for the 747 as well.

regards
Andras