Fsbuild-2 Flight Planner

I want to make a long flight, around 3 hours, with my A330.
I load my flightplan into the Smiths FMS, prepare everything, take off, climb, cruise at FL350 / mach 0.84 (around 300 IAS)... all ok.

All looks good, LNAV and VNAV ON, the FMS shows me the legs, arrival time, distance to arrival, and T/D at around 900 nm.

..But suddenly, the FMS starts the descent procedure. On my AP, speed is reduced to 280 (IAS), Altitude is set to 400 feet and VS starts to be negative (-200 ft/mn)... the problem is that I am at around 850 nm from destination airport
Little boring isn't it? I try to put manulay altitude back to FL350. It works, but after few minutes, comes back to 400 feet. The FMS gets crazy and in the Descent page, I have no more "TD at xxx".. The FMS has decided by itself to start the descent.
I don't know how to upload and include small printscreens on this post (only via URL, not very easy!), but if needed, I have some of FMS and AP indications to show what happens..

I already noticed such a thing 2 or 3 times ago during other flights, and I thought I made some bad manipulations, but here, FS9 was alone and I did not click anywhere when it happened..

I am using FS9 without any addon, just FSUIPC not registered.. The Aircraft is the CLS A330-200 with CLS panel.

Any suggestion?
Thanks in advance.

_________________
Patrick.

Yes, most of the time, my VNAV begins its descent immediately after it crosses the last highest fix on the route. This means I'll arrive at the next step down altitude some time before I cross the next fix---kind of a 'dive and drive' style of flying. However, sometimes (and I have no idea what determines which method), I've observed that VNAV will delay making its descent so as to cross the next fix right at the proper altitude. This latter method is more in keeping with how real VNAV works in these aircraft.

The other two issues I've discovered with VNAV is that sometimes, the descent will stop somewhere between altitudes for no apparent reason or it won't make a sufficiently vertical speed rate to meet the next altitude.

Lastly, I just finished doing a VNAV supported GPS approach in which the AP flew perfectly until the last fix. However, instead of descending the airplane down to the airport altitude, VNAV arbitrarily changed the field elevation to 35,000 feet (my ISG FMS seems partictularly fond of that altitude for some reason ).
Needless to say, in that situation, you've got to be quick about disconnecting the AP before you go climbing right into a stall while in landing configuration.

I'm glad (!!!) to see that I am not the only one experiencing some troubles with VNAV.

One other thing I noticed is during climb.
After takeoff, I manually climb at VS =+2300. For my aircraft, it is a good VSpeed to maintain the engines in correct operating range and not overload them with full passengers and fuel.
Then, switching ON the AP and VNAV, VS goes down to +1500 until around FL150 and then increases more and more, progressively up to +2900 until the cruise level.
My IAS is set to 290 but at such high VSpeed, at around FL290, the aircraft starts to slow down very dangerously to 230/240 with the engines at full thrust and the nose very up.
Usually, when altitude gets more and more high, the VSpeed must be reduced to +1700 or +1800 to allow the aircraft's speed to be constant and to keep the engines in correct working range.
It seems that VNAV does not do it...

_________________
Patrick.

I've noticed the +1500 fpm gradually increasing. I believe it is because at a constant IAS, your ground speed starts increasing, therefore the vspeed has to be increased to hit the calculated T/C.

Generally, I engage LNAV and VNAV shortly after takeoff unless ATC is shuffling me around, then disengage VNAV as I get over around FL200. I generally start reducing my Vspeed as I climb so the aircraft can maintain airspeed during this phase.

Once at cruise, I'll often turn VNAV back on, mainly so I don't forget to start my descent nearing my destination. However, so long as I am paying attention (which is most of the time), I'll roughly calculate my T/D using the 1:3 rule and descend at 250IAS and -1800fpm.

If ATC is active, I'll of course turn LNAV off as soon as they start vectoring me, otherwise I'll leave it on till I'm close to my last waypoint, or when I need to vector myself to line up for my FAF.

The moral of the story is that I find the LNAV very useful until the last 15 minutes or so of flight, but VNAV is only reliably "handy" in my view for following a STAR; even then it will do some unexpected things at times, but I put that down to my lack of understanding. Of course, at some point VNAV is going to set a very low altitude (like a few hundred feet). Once it does that I'll turn it off and reset the Alt to an appropriate approach altitude, generally something like 3000 AGL give or take.

I use the Boeing ND display, and prefer to utilize the BOD arc myself to make adjustments for crossing altitudes and such. I feel I have better control of the aircraft this way, as I know what it is going to do. I'm not even certain the VNAV is meant to be all that useful in the final 15 or 20 minutes of flight - at least, it doesn't seem so to me.

_________________
The glass is twice as big as it needs to be.

Hi all,

Apologies for not being arund much lately. I'm sorta in the middle of fulfiling a contract for another product, so that has taken a little priority for the past couple of weeks.

There are some points I wish to make about the VNAV function.

1) The VNAV function is probably my least favorite function to work on. The reason is it is terribly time consuming to test and debug. You don't really see what its doing until you are actually flying it. It can take several flights to re-create and issue, then a few more to verify it is indeed fixed
and we didn't create any new problems.

One of the reasons its time consuming is because the reports of issues with it aren't really specific enough for myself to go in and re-create it easily. I could fly 10 different flights and not re-create the scenario Patrick is referring to.

I really need to be doing the almost 'exact' same things you are doing. That's not possible unless I have the same .cfg settings you have, flying the same flight plan route, and setting the same cruise altitudes, flying the same speeds, making the same route amendments, altitude changes,
crossing restrictions you are doing etc.

2) There are many different settings and .cfg's. Unlike the other FMS's which only have to worry about one set of parameters for one aircraft's performance. The .cfg settings affect the VNAV behavior differently.

3) I only occasionally use VNAV during my normal flying. I just prefer to set my altitudes and speeds manually on most of my flights, its just my style of flight-simming. I use LNAV all the time, but VNAV only occasionally. Generally I haven't experienced these reported VNAV issues, I suspect that is in part because I don't use VNAV often, and also I likely do not perform some of the steps or sequence of steps some of you are doing in your normal flying activities.

4) Some aircraft have partially or fully custom autopilots. And in some cases these autopilots don't properly accept the VNAV input from the ISG gauges.

Some things I have seen that has caused confusion..

A) Being at a different cruise altitude than is set in the FMS. The FMS calculates/sets a certain cruise altitude. If you do not meet that cruise altitude the descent may be triggered prematurely. Example if the cruise altitude is set in the FMS for FL350, and you only climb to FL280. The TOD position was calculated from the FL350 position which would be premature for a descent from FL280. Regardless when it hits that TOD position it will begin the descent.

B) Flying a significantly different climb or descent speed than calculated by the FMS. This is in the ballpark of what Dan alluded to. The FMS is using TAS to calculate the descent path. But of course we normally tend to fly mach or IAS speeds.

In ver 1.0 Beta we orginally only had a ClimbTas, and DescentTas, setting. But it soon became clear that the Beta testers were entering an IAS value as they knew what IAS speed they'd be flying but not what TAS they'd be flying. So prior to the ver 1.0 release we replaced it added ClimbIas, and DescentIas (we put ClimbTas= etc back in ver 1.4). This meant the FMS had to do a conversion from Ias to TAS which is a problem as TAS changes at a constant IAS while climbing/descening. So the compromise was to average it out and and calculate what the average IAS/TAS would be for the entire descent.

In the case of what Patrick reported, manual climb first, then turn on VNAV. If you manually climb 'above' the calculated climb path, when you engage VNAV it will likely fly a lower vertical speed as you are above the point it calculated. It will just calculated a vertical speed to meet the crossing from whatever altitude and distance you are currently from
the TOD. If you maintain a constant IAS in the climb, your TAS will increase, as the TAS increases the climb rate will increase to try and stay on the calculated climb path (to max 3000 fpm).

Basically its going to fly what it calculated from the .cfg settings. So if you tend to fly much differently then the .cfg settings, you need to adjust them to more closely match what you want VNAV to do. The VNAV default settings are fairly light as those default settings have to work with slow as well as fast aircraft.

At mimimum the information I need is...

1) The isg.cfg file, and the (AircraftId).cfg file you are using.
2) The Flight Plan route you flew (ie the .rte or .pln file)
3) The cruise altitude set in the FMS (and any changes to the crz alt en route).
4) Any manual FMS clb, crz, or des tgt spd settings.
5) Any crossing altitude/speed restrictions inserted into the FMS.
6) What point was VNAV turned on (ie on departure, reaching cruise, or just prior to TOD, during descent ???)

IOW I want to as much as possible re-create the flight you observing the reported behavior with.

This hopefully will allow me to re-create the problem/issue/behvaior in 1 or 2 flights, instead of having to try out all sorts of different scenerios in the faint hope I might get lucky in re-creating the problem.

VNAV seems to be a feature that issues arise sometimes only when the right conditions and settings exist. VNAV is probably the feature that makes the most use of the .cfg settings.

So although its 'somewhat' helpfull to report that in some instances you experienced a premature VNAV descent. Or that its doing something 'occasionally' or intermittendly. Because there are so many possible .cfg settings etc, its not really enough information for me to go diving into that feature again without more specific details.

Keep in mind this sort of VNAV feature that can be applied to different aircraft types really has never been done before for MSFS. Usually VNAV is available for one FMS linked to one aircraft model. The idea of using .cfg files to create a VNAV feature on the fly is still fairly new. Its something that over time I think we can get closer to perfection, but its not there yet.

Regards.
Ernie.

Hi Ernie!
Many thanks for this so long explanation! I understand that it is not so easy with VNAV to fit every aircraft.. If I can be helpful for you, it will be a pleasure to test some adjustments!

I reply to your request:
1) The isg.cfg file, and the (AircraftId).cfg file you are using.

I tried to attach the .cfg files, but forum says: "The Extension cfg is not allowed".

2) The Flight Plan route you flew (ie the .rte or .pln file)

Exactly the same for the .pln files "The Extension pln is not allowed"

So, I will put all the text of these files at the end of this message..

3) The cruise altitude set in the FMS (and any changes to the crz alt en route).

The Cruise altitude FL350 was set at departure, no change during flight

4) Any manual FMS clb, crz, or des tgt spd settings.

No change from my A330_pa.cfg file:

// ---------- CLIMB --------
ClimbIas=290
ClimbIasMax=300
ClimbIasMin=270
ClimbRate=2200
MaxVnavClimbRate=2300
// ---------- CRUISE ---------
CruiseIas=302 //Cruise Indicated Airspeed (kts)
CruiseIasMax=310 //Maximum cruise speed (Ias) used in Smiths fms only.
CruiseIasMin=290 //Minimum cruise speed (Ias) used in Smiths fms only.
// ---------- DESCENT ----------
DescentIas=290 //Descent Indicated Airspeed (kts)
DescentIasMax=305 //Maximum descent speed (Ias) used in Smiths fms only.
DescentIasMin=270 //Minimum descent speed (Ias) used in Smiths fms only.
DescentRate=2300 //Descent Rate (fpm)
MaxVnavDescRate=2400


5) Any crossing altitude/speed restrictions inserted into the FMS.

Parameters coming from my A330_pa.cfg : automatically put into the FMS (they really appear in the climb and descent pages and are effective during flight)
ClbAltRest=10000
ClbSpdRest=250
DescAltRest=10000 //Default descent altitude restriction, combines with the 'DescspdRest' parameter.
DescSpdRest=250 //Default descent speed restriction.

6) What point was VNAV turned on (ie on departure, reaching cruise, or just prior to TOD, during descent ???)

VNAV was turned ON during beginning of climb at around 2000 feet (Radio Alt)

I hope this helps!!

PS: did you read my previous post about local panel variables for Range and Mode buttons for the ND? (Title: Third party EFIS Control variables?) ?

Here are the files contents:
FlightPlan (.PLN file):
[flightplan]
title=LFBI to UKOO
description=LFBI, UKOO
type=IFR
routetype=1
cruising_altitude=35000
departure_id=LFBI, N46* 35.25', E0* 18.40', +000423.23
departure_position=3
destination_id=UKOO, N46* 25.62', E30* 40.68', +000170.60
departure_name=Biard
destination_name=Odesa
waypoint.0=LFBI, A, N46* 35.25', E0* 18.40', +000423.23,
waypoint.1=MN21, I, N46* 36.49', E0* 19.46', +000000.00,
waypoint.2=Fix01, I, N46* 39.36', E0* 22.00', +000000.00,
waypoint.3=Fix02, I, N46* 33.94', E0* 28.23', +000000.00,
waypoint.4=BALAN, I, N46* 30.97', E1* 2.00', +000000.00,
waypoint.5=MC, N, N46* 22.36', E2* 29.56', +000000.00,
waypoint.6=RISUN, I, N46* 21.93', E2* 36.20', +000000.00,
waypoint.7=LEMIN, I, N46* 30.50', E3* 2.90', +000000.00,
waypoint.8=KUKOR, I, N46* 32.50', E3* 7.75', +000000.00,
waypoint.9=MOU, V, N46* 42.41', E3* 37.90', +000000.00,
waypoint.10=ATN, V, N46* 48.36', E4* 15.55', +000000.00,
waypoint.11=LUSAR, I, N46* 40.13', E5* 10.77', +000000.00,
waypoint.12=SAUNI, I, N46* 37.42', E5* 28.67', +000000.00,
waypoint.13=LIRKO, I, N46* 34.25', E5* 48.85', +000000.00,
waypoint.14=MOLUS, I, N46* 26.63', E6* 40.77', +000000.00,
waypoint.15=SOSAL, I, N46* 33.48', E6* 53.08', +000000.00,
waypoint.16=TELNO, I, N46* 46.32', E7* 16.25', +000000.00,
waypoint.17=KORED, I, N46* 51.03', E7* 24.85', +000000.00,
waypoint.18=KONOL, I, N46* 59.72', E7* 40.85', +000000.00,
waypoint.19=BERSU, I, N47* 8.13', E7* 56.48', +000000.00,
waypoint.20=SUREP, I, N47* 9.92', E8* 0.65', +000000.00,
waypoint.21=DITON, I, N47* 18.13', E8* 20.00', +000000.00,
waypoint.22=KUDES, I, N47* 31.25', E8* 51.43', +000000.00,
waypoint.23=BAMUR, I, N47* 32.68', E9* 32.62', +000000.00,
waypoint.24=ALGOI, I, N47* 26.85', E10* 29.32', +000000.00,
waypoint.25=KOGOL, I, N47* 37.28', E11* 22.08', +000000.00,
waypoint.26=TULSI, I, N47* 42.10', E11* 47.33', +000000.00,
waypoint.27=CHIEM, I, N47* 49.52', E12* 27.35', +000000.00,
waypoint.28=INSOL, I, N47* 50.44', E12* 37.18', +000000.00,
waypoint.29=MORED, I, N47* 52.58', E13* 0.93', +000000.00,
waypoint.30=NEMAL, I, N47* 55.08', E13* 29.90', +000000.00,
waypoint.31=LIMRA, I, N47* 54.66', E14* 26.87', +000000.00,
waypoint.32=GAMLI, I, N47* 54.40', E14* 46.73', +000000.00,
waypoint.33=BARUV, I, N47* 53.66', E15* 28.85', +000000.00,
waypoint.34=SNU, V, N47* 52.49', E16* 17.31', +000000.00,
waypoint.35=ABLOM, I, N48* 4.05', E17* 5.26', +000000.00,
waypoint.36=LEDRI, I, N48* 5.45', E17* 10.97', +000000.00,
waypoint.37=XENAK, I, N48* 7.17', E17* 17.98', +000000.00,
waypoint.38=JAN, V, N48* 10.72', E17* 32.68', +000000.00,
waypoint.39=NIT, V, N48* 17.43', E18* 3.04', +000000.00,
waypoint.40=ABITU, I, N48* 20.00', E18* 19.48', +000000.00,
waypoint.41=SLC, V, N48* 27.19', E19* 6.95', +000000.00,
waypoint.42=TAGOD, I, N48* 30.65', E19* 36.95', +000000.00,
waypoint.43=TAKOS, I, N48* 34.95', E20* 16.00', +000000.00,
waypoint.44=KSC, V, N48* 40.99', E21* 14.89', +000000.00,
waypoint.45=MALBE, I, N48* 49.43', E22* 22.50', +000000.00,
waypoint.46=BUKOV, I, N47* 57.10', E25* 57.50', +000000.00,
waypoint.47=SCV, V, N47* 40.34', E26* 21.65', +000000.00,
waypoint.48=IAS, N, N47* 14.06', E27* 34.78', +000000.00,
waypoint.49=UNIRA, I, N47* 10.10', E27* 51.10', +000000.00,
waypoint.50=CHN, I, N46* 55.63', E28* 53.98', +000000.00,
waypoint.51=ANEDO, I, N46* 21.80', E29* 41.52', +000000.00,
waypoint.52=KIWOK, I, N46* 29.00', E29* 49.00', +000000.00,
waypoint.53=Fix03, I, N46* 27.12', E30* 17.74', +000000.00,
waypoint.54=D188G, I, N46* 6.19', E30* 44.18', +000000.00,
waypoint.55=D179G, I, N46* 8.66', E30* 47.80', +000000.00,
waypoint.56=D167F, I, N46* 13.04', E30* 46.04', +000000.00,
waypoint.57=Fix04, I, N46* 19.55', E30* 43.17', +000000.00,
waypoint.58=UKOO, A, N46* 25.62', E30* 40.68', +000170.60,

isg.cfg:
LoadFuelonFlightPlanLoad=1 // Load Fuel automatically when Flight Plan is loaded into FMC or MCU
SetDestLoadTowerViewDist=20 // The distance from the destination airport when the tower view is changed to the destination (FS9 only)
SetMCUToPageOnFPlanLoad=1 // Set the active page on the MCU to the 'TO:' page when a flight plan is loaded.
DispAppPtrnAlts=1 // Display Approach and traffic pattern alts
ShowTodBodIndicators=1 // Show TOD/BOD indicators
DispPrevWpt=0 // Display Previous flight plan waypoint (MFD,EHSI).
//ParkingFile=isg_parking.txt // Parking positions file
WptProcChgDist=2.3 // Waypoint change distance for procedures (Sid,Star, etc)
ClimbRate=2200
MinVNavRadioAlt=500
MFDTextAntiAlias=1
FlightPlansFolder=C:\Documents and Settings\Administrateur\Mes documents\Fichiers Flight Simulator
SetWptBaro=1

Aircraft' isg .cfg file (A330_pa.cfg):
; A330-200
ModelId=A330-200
FPA=3.5
MaxCruise=38000
MinVnavIas=135
MinVNavRadioAlt=500
VnavSetSpdDist=30 //Distance from speed restriction wpt the restriction speed is applied (default is 25 nm)

SetUTCTimeOnFPLoad=1 // Sets sim clock to current GMT time based on PC clock's time when a stored flight plan is loaded into the MCU

// ----------------

MFDTextAntiAlias=1
WptChgDist=4 //The distance (in Lnav mode) the autopilot changes to tracking the next waypoint (default is 4.0 nm)
HoldLegMins=4

ApprFlapsMin=14
ApprFlapsMid=22
ApprFlapsMax=32
LdgFlaps=32 //Default Landing flaps value displayed in the smiths fms approach page

BestHoldIas=260

SetWptBaro=1
ShowTodBodIndicators=1
LoadFuelonFlightPlanLoad=1

ToFlapsRange=8,14,22,32
ToFlaps=14
V1=115
VR=120
V2=130

// ---------- CLIMB --------
ClimbIas=290
ClimbIasMax=300
ClimbIasMin=270

ClimbRate=2200
MaxVnavClimbRate=2300
ClbAltRest=10000
ClbSpdRest=250

CostIndex=150 //Default Cost Index value for smiths fms , range is between 0 and 200.

// ---------- CRUISE ---------
CruiseIas=302 //Cruise Indicated Airspeed (kts)
CruiseIasMax=310 //Maximum cruise speed (Ias) used in Smiths fms only.
CruiseIasMin=290 //Minimum cruise speed (Ias) used in Smiths fms only.

// ---------- DESCENT ----------
DescentIas=290 //Descent Indicated Airspeed (kts)
DescentIasMax=305 //Maximum descent speed (Ias) used in Smiths fms only.
DescentIasMin=270 //Minimum descent speed (Ias) used in Smiths fms only.

DescentRate=2300 //Descent Rate (fpm)
MaxVnavDescRate=2400
DescAltRest=10000 //Default descent altitude restriction, combines with the 'DescspdRest' parameter.
DescSpdRest=250 //Default descent speed restriction.

EngThrust=72000

_________________
Patrick.

Thanks Patrick,

Put the .cfg file in a zip file, and it will accept it.

I'd still like the file in the format you are using it in rather than copying text off the forum. as sometimes the issue could be something as subtle as an extra blank space or hideen character in the .cfg that may not show or transfer when I copy and paste from the forum.

Thanks.

Regards.
Ernie.

Ok no problem..

I don't use Winzip, only Winrar. Hope .rar file is ok for you?

Here is the file attached.

_________________
Patrick.

WinRAR is fine (thanks), I try it out this weekend and see if I can re-create the behavior you have reported.

Regards.
Ernie.

Here are 2 screenshots of what happens. Destination is at 928 nm, Track is OK (062 in FMS and 064 real), The LEGS page says that I should stay at FL350 during a long time before descent (it remains more than 2 hours of flight)..., but the PROGRESS page shows that I am already descending... with SUREP at FL348... destination altitude is 400 feet and VS -200.

_________________
Patrick.

What does the DESC page show as the distance to TOD before reaching the point you're showing, and then after the aircraft starts descending?

_________________
Patrick.