[jhb_airlines] Re: Autopilot APPR HOLD problem

  • From: Gerry Winskill <gwinsk@xxxxxxx>
  • To: jhb_airlines@xxxxxxxxxxxxx
  • Date: Mon, 17 Oct 2005 19:34:14 +0100

Having finally got FS9 to work again, of which more anon, I tried a flight and IOM 26 ILS, with wt shifted forward. As you say, it made little difference to the AOA and I share your view that the C of G is out. I'll leave you to fiddle with that.
On finals, all in APPR, I progressively lowered the set speed to 85 kias. First noticeable fact is its reluctance to let the speed decay that low. At 87, with even higher AOA, it came slightly below the glidepath and remained stable at that displaced position. The outcome was an undershoot of a few hundred yards. Fair play, it did it gracefully. Highest trim readout was 51; considerably lower than the pre tweek situation, where despite that it couldn't remain on the glideslope.

Back to my FS9 bootup refusals. Having re installed the Radeon drivers, which couldn't possibly have been causing the problem, done the usual things like deleting FS9.cfg, I fell back on the mark one eyeball method. Since all failures were accompanied by just one of the GF MCP's lights coming on, I unpluged the Autopilot. FS9 then booted OK. Switched it off and ran GFConfig and all in the garden is lovely again.
Another one to go in my fault box.

Gerry Winskill

Bones wrote:

If you start adding weight to the front of the aircraft you'll be going
round in circles. More weight means more lift required and a greater AoA for
any specific speed. Even if you just shift weight forward without increasing
it, all that happens is that you get a nose down pitch that will rob you of
lift and you will need more aft stick (and trim) to compensate.

Incorrect trim (and it has too much back trim by default) indicates an error
further back in the design process and, in this case, I suspect a problem
with weight and balance - probably an incorrectly set CoG position. It only
has to be a few inches out to make a huge difference to trim.

I have also got the aircraft to fly an approach below 100kts but I haven't
touched the trim or CoG settings (yet). The changes I have made have been
all in the .air file - adding the FS2004 control effectivity tables that
were missing. The engine parameters were also missing and I am playing with
those right now. There is too much residual thrust at idle speeds - it
should be down at 24% N1 similar to the Falcon and not up at 39%.

The trouble with .air file changes is that they don't take effect unless you
reboot FS so it's a messy business.


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill
Sent: 17 October 2005 17:55
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem

Amazed that tweaking the elevator trim effectiveness can have made such a change! Recently landed at EGNS 08, in really claggy weather. Using APPR, it locked ont Localiser an Glideslope, holding the GS with the AP speed down as low as 100 kias. A significant difference was the amount of elevator trim used. Pre tweeking it ran out of trim, at a digital trim readout of 81. Post tweek and the highest trim figure seen was 31. It was also rock steady, as it was after I'd disabled AP, at 5 DME. One thing that hasn't changed is the high AOA. It's quite nose up when flown level at 130. Pre tweek it was reasonably flat on the GS. Now it's a high AOA on the Glideslope. I was about to try a repeat, with a high forward load. Unfortunately I can't. I can't get FS9 to run. Part way through the bootup I get a 98 deg reading displayed in the GF MCP Heading window, followed, shortly, by a phone home and out. I've rebooted the PC and it went almost to the end of bootup, then quit. At that point I got a message saying FS9 was unlikely to run, with my present Raedeon 7000 drivers. Now the Radeon only drives the second monitor, the one that just displays the instrument panel. Just downloaded latest drivers. May be gone for some time.

Gerry Winskill

Bones wrote:

Same as I get and it's too high. That is still quite a bit of thrust
and it could do with being at least 5% lower. I'll have to play with
the .air engine values. I could alter the aircraft.cfg figures but if
the values are also in the .air file it can sometimes reset the
aircraft.cfg figures next time you boot FS up..


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill
Sent: 17 October 2005 15:37
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem

The Fan Speed falls to 39%, with throttles registered as fully closed.

Gerry Winskill

Bones wrote:

When you say you turned the IAS to zero on the AP and saw the throttle
close can you be more explicit? The throttle levers may well go down
to zero but what N1, N2 and EPR values do you get? The throttle lever
position isn't a guarantee that the engines have completely spooled


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill
Sent: 17 October 2005 15:07
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem

Thanks for the data. I've not tried since increasing the flap drag. I wonder if the throttoe problem is associated with the AP, in the panel you are using. I've just turned the AP's IAS down to zero and the throttle definitely closed on this one. Confirmed because I made a throttle % open gauge and that goes to zero. Iput it in so that I can pick the correct throttle opening, on final, after disengaginp AP and slowing to landing speed. The panel I'm using is for the 550 but is quite similar to that shown on your website. I can't recall the file name but it should be reachable via the into to the panel.cfg file:

// This Panel.cfg file created by FS Panel Studio -
http://www.fspanelstudio.com // Built Saturday, December 27, 2003 at
18:26 FSPS Build:8294

Gerry Winskill

Bones wrote:

I don't have any values for the CJ2 here and it could easily have
different flap settings to the CJ1. The existing aircraft.cfg values
are 0, 15 and 45 as you note and would seem to follow the current
trend on some aircraft of absolute minimum flap settings (up, take
off and land).

The CJ1 I've had the pleasure to fly in is different and it has flap
values of 0, 15, 35 and 50. Here are the book figures:

T/0 Weight    15 deg Flap Setting   0 deg Flap Setting
             V1  Vr  V2            V1  Vr  V2
10600           107 107 111           113 113 119
10000           102 103 108           109 109 115
9500             98 100 105           105 105 113
9000             97  97 103           102 102 110
8500             97  97 103            98  98 107
8000             97  97 104            98  98 107
7000             97  98 106            98  98 109

Stall Speeds

Zero Angle of Bank, Landing Gear UP or Down, KCAS
          Flap Position
Weight     Land   15deg    UP
10600       86      91     98
10000       83      89     95
9500        81      87     93
9000        79      85     91
8500        77      82     88
8000        75      80     86
7500        73      78     83
7000        70      75     80

Take-Off 0 and 15 degs flaps
Landing Approach 15 degrees
Full Flaps Land 35 degrees
On Landing Flaps 50 degrees...used to help braking

Note that 50 flap is only used as an after landing speed brake so we
really only need 0, 15 and 35 in FS. However that is for the CJ1 and
as there are so many versions of the Citation out now (which I have
totally lost track
of) it could well be that other versions have different flap
settings. The Citation X is quite a different beast to the little

Also note that in the CJ1 figures above the Max Landing Weight is
just 10600lb whilst the CJ2 is up at 15200lb. I would therefore
expect the speeds to be a touch higher. For the CJ1 a rotate speed of
about 105/115kts seems average and an approach speed of 106kts at max
weight looks good (as Va = Vs x 1.23). I'll hunt around and see if I
can find the CJ2 figures but expect them to be a touch higher than

You can easily alter the aircraft.cfg values if you wish. As a
reminder put the original values in the comment section so you
remember them - they can go anywhere after the // symbols. Just out
of interest did it say which variant of Citation the panel was for?


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Lucas
Sent: 17 October 2005 12:29
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem


I was trying to find out what flap settings exist on the real-world
Citation.  If there are 4 (0, 5, 15, 35), as the panel I am now using
would seem to suggest, can I modify the current entry in aircraft.cfg

type             = 1          // 1 - tail, 2 - lead
span-outboard    = 0.8        // 0.0 .. 1.0
extending-time   = 5          // seconds
system_type      = 0
flaps-position.0 = 0          // degrees
flaps-position.1 = 15          // degrees
flaps-position.2 = 45         // degrees
damaging-speed   = 250        // KIAS
blowout-speed    = 300        // KIAS

by inserting an additional line for flaps 5, and amending flaps 45 to
flaps 35?  Or is such tinkering another minefield .... ?

Mike L

Bones wrote:

The problem with designing a flap gauge is that you have to specify
the number of indents. No problem if it matches the aircraft's cfg
file but it produces oddities when the aircraft has different
settings. What I think happens is that the aircraft.cfg values are
read by FS. In this case you will have one redundant flap position
which you might reasonably assume comes at the end of flap
selection. This sometimes isn't the case so it may be best to check

I had this situation on another aircraft when trying to adapt a non
standard panel. Flaps 1 worked OK, Flaps 2 did nothing, Flaps 3 and
4 worked fine. I just had to remember that I had to press the button
twice for second stage flaps.

When a mismatch like this happens you can easily change the
aircraft.cfg to get flap selection to match the lever but this is
usually incorrect. It's better to get the flap lever to match the
aircraft but this is not an option on old GAU files and a tad messy
with XML.


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Lucas
Sent: 16 October 2005 21:51
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem

I have installed a different panel for the Citation (2k4citxp.zip from Avsim) which looks a bit less of a jumble and seems to work OK with FS2002. No problems with APPR_HOLD or autothrottle. It does appear a tad blurry mind you ... not just my eyesight either.

I notice that it shows 4 flap settings (0, 5, 15, 35), although
aircraft.cfg has only 3 settings (0, 15, 45).  What should it be?

Mike L

Bones wrote:

What a strange panel.

I remember it now, one of many I've tried and dumped in the past.
This one proves that if you have a very good panel for an aircraft
you think the aircraft itself flies nicely and if you have a bad
panel the aircraft is rubbish. I had no problems with the Citation
at all until I attached this panel to it. I've flown it around for
a couple of hours now and didn't enjoy much of it at all.

The panel itself is a strange mixture of good and bad. It's got a
lot of GAU files but there are several XML's in there too. What I
don't understand is that one of the XML CAB files it uses has 84
switches in it (including all the autopilot functions) but he's
only borrowing two switches from this file and ignoring the rest.
The autopilot switches he has chosen are separate GAU files and are
not quite standard - they do slightly odd things.

The APPR button worked for me, both on the GF unit and selecting it
on the aircraft panel. The Speed button seems OK'ish too but it's a
cobbled thing - it acts as both AP_AUTOTHROTTLE engage and
AP_IAS_HOLD in one unit. No separate Autothrottle arming switch.
Bad news is that it sometimes doesn't disengage when you deselect
it and it's usually too late when you find this out.

Other oddities are the GPU/APU as the aircraft is BAT start or GPU
only. In fact you can start this aircraft without using the APU at
all so it's only there for show. Bottom left switches work OK but
the labels are very poor on the bottom row.

It's a very messy layout which leaves you hunting all over the
place for familiar switches and dials. Some dials (like RAD ALT and
TRIM) are huge whilst other essential instruments are far too small
to be read easily. Some dials are quite sophisticated, like the
standby horizon and other border on the crude - the ALT SEL thing on
the panel looks like a rubber grommet to me.

Flying tests proved something of a trial as I was trying to
understand aircraft responses as well as hunt around this panel for
data. I found faults with both the aircraft and the panel though.
Aircraft first...

This isn't a jumbo - it's a very nippy little jet - so you have to
revise your thinking about climbout procedures. Set about +60 trim
and apply full throttle. When you hit 100kts pull the nose up to 25
degrees on the horizon (I can tell you this doesn't feel natural as
you think you will stall but PULL THAT STICK BACK!). Get the gear
up (don't use flaps) and trim for 25 degrees. At this pitch the
aircraft will settle into an 1800fpm climb at around 150kts. Keep
checking the nose and don't let it drop until you have the AP set
up and on. Don't forget that the C550 doesn't have any slats or
other fancy lift devices that add both lift AND drag to the bigger
jets so it is going to take off like a scalded cat. You have to
contain this.

Round for the first ILS and the APPR mode captured the ILS first
time. The approach seemed normal until about 4nm out and then the
aircraft just dropped off the glideslope and started a rapid sink
earthwards. This was at 120kts so it was well above stall so I
climbed away for some handling. In manual flight it would happily
fly round at 100kts flaps up without batting an eyelid and a little
bit slower with flaps down. Get below these speeds though and the
drag rises rapidly - if you check a slight loss of height by
pulling the stick back even very slightly the speed winds off very
fast indeed. I flew 100kt circuits without any problem at all so I
tried a second ILS. Again the thing was fine at more than 120kts
but as soon as I brought it even one knot lower it quit the
glideslope capture. I've seen other aircraft do this too so I'm not
sure what is going on. I'll try the ILS on the normal panel I use
and see if it is any different. I could be panel related or it may
be a drag/autothrottle mismatch.

Just after that it locked up my GF_MCP readouts totally - although
the dials still worked.

Differential roll I have sorted out. The aircraft still has an
FS2002 .air file and it's missing quite few entries for FS2004. As
soon as I entered values for tables 342 and 518 it started to
behave properly. I'll do the same for elevator and rudder next.

Actually I won't go on any more as I'll just rip the panel to
pieces and it doesn't really deserve it. Some bits are very good
but they are spoiled by tacky, mickey mouse dials alongside. The
engine gauges are good (a pity you can see the sky behind them as
he hasn't quite got the fit right) as are the annunciator lights
above. The main EHSI is too small, too cluttered and very bad to
read. The autopilot switches are all over the place (the original
isn't too good either but it's not THAT bad). A good rebuild might
see it much improved but that would be a reasonably long job.

I just tried an ILS with a second panel and the same drop below the
ILS happened when speed got below 121 kts so it must be an
automatic decouple for some reason. It's usual for this to happen
near the stall but this is excessive for this aircraft. Daft thing
is that you can switch off the autopilot and fly quite happily
manually for the rest of the approach..

Must investigate further.


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Lucas
Sent: 15 October 2005 16:57
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem

Thanks for the offer, John. Remember that I use FS2002 so it could be that the panel (cessna_citation_ii_v2.zip from Avsim) - which is listed for FS2004 - won't work properly with FS2002. Having said that, the aircraft itself is listed as FS2004 but it seems fine in FS2002.

Mike L

Bones wrote:

Give me the name of this panel and I'll download it and have a
hunt around. If the autopilot is an XML file I should be able to
track down why the APPR button isn't working. OTOH if it's and old
GAU file then that's beyond my abilities as I have no C++ skills.

I've built an autopilot for the Aztec and the code is very simple.
An APPR button isn't very hard to do so I could probably add this
to the Citation if the original is faulty.


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Lucas
Sent: 15 October 2005 12:48
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem


Thanks for this info, and your other reply on gauge design.  I
have no desire to enter a minefield ....

I may try a different panel with the Citation and see if I can get
APPR_HOLD to work.

Think I've got the AP autothrottle and IAS hold sussed now ... <g>

Mike L

Bones wrote:

You are walking into a minefield here Mike so it may be best to
leave well alone. I don't know anything about the panel you got
for the C550 but it would need a much closer look at the gauges
supplied to see what was included in the package and what was

The gauge line you quote doesn't mean a lot to me as I don't have
a fsd_generic.ap.appr.gau (it could be a CAB file too). It
becomes tricky because just because the line is in the panel.cfg
file it doesn't automatically mean the gauge itself is in your
gauges folder. Although likely I can't even say this is an APPR
hold function either. It's unusual if it is because ALL the
autopilot functions are normally contained in a single autopilot

The FS command AP_IAS_HOLD is a different beast to
AP_AUTOTHROTTLE. If you set a P8 button for the latter then
(assuming the aircraft is fitted with an AP and AT in the
aircraft.cfg file) you have access to speed control - it is,
effectively, the Autothrottle Arm function.

The AP_IAS_HOLD function is the same as the IAS button on the
autopilot panel on most aircraft. This is an engage/disengage
button but it has no effect if the Autothrottle isn't armed in
the first place. You don't need to allocate this button to a P8
switch because it should already be programmed into the HOLD
button below the IAS/Mach rotary switch on your MCP. It's the
same as the NAV and HDG hold buttons alongside - press to engage
or disengage.

So, what you should really have is the AP_IAS_HOLD command set to
the HOLD button below the IAS/Mach panel on the MCP. On the P8
you allocate a button for the AP_AUTOTHROTTLE function. When
flying the aircraft you hit the P8 to arm the autothrottle, dial
in a speed you want and then press the HOLD button to engage.

You can mostly ignore the reference speeds in the aircraft.cfg as
they are only used in one of the FS menus - I think Weight and
Balance. They have absolutely no effect on the sim itself. The
speeds are actually the wrong way round but they are correct -
the Citation has a very low stall speed. It was intentionally
designed for slow flight as it gave the aircraft the ability to
operate out of very short strips - something no other jet is
capable of. It was an impressive feat by Cessna as the aircraft
doesn't have any complex wing devices at all, but there again it
is quite a light aircraft.

What is good about the Citation is that at 100kts the aircraft
still has excellent roll rate. It is a very nice aircraft indeed
for a pilot and doesn't really deserve its "toy jet" title from
the Lear/Falcon brigade.


-----Original Message----- From: jhb_airlines-bounce@xxxxxxxxxxxxx [mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Lucas Sent: 14 October 2005 19:29 To: jhb_airlines@xxxxxxxxxxxxx Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem


I'm afraid I don't know what it is I'm looking for in the panel
and aircraft.cfg files ...

Panel.cfg contains the line -

gauge37=fsd_generic.ap.appr,  213,517,20,23

which suggests to me that there should be a working APPR_HOLD

As regards the GoFlight autothrottle, I have disabled the "arm
when CMD is activated" option.  But I cannot get the IAS/Mach
hold to work

from a P8 button. The appropriate P8 light comes on but it


activate the IAS/Mach hold (yes, I have designated the correct
function in GF config).  I can only get IAS/Mach hold to work
Ctrl+R.  Any ideas??

Going back to the Cessna Citation specifically, I found the
following in aircraft.cfg -

[Reference Speeds]
flaps_up_stall_speed=77.0      //Knots True (KTAS)
full_flaps_stall_speed=80.0    //Knots True (KTAS)
cruise_speed=262.0              //Knots True (KTAS)

Surely flaps up stall speed should be higher than full flaps
stall speed?? - and I would have expected both to be 100+ kts.


Mike L

Bones wrote:

First thing to suspect is the panel because it suggests the
autopilot gauge it uses may not be working properly. If it works
in other aircraft but not the C550 then it may be the
interaction between the panel and the aircraft.cfg file. In my
copy both the autopilot and autothrottle are flagged as

Check the MCP options in the GF Module. You should have two
radio buttons which enable/disable autothrottle with AP
activation. I don't actually use this myself as there are times
when I want to keep AT active when flying manually and so I have
one of the T8 switches set for AT engage/disengage. This works
perfectly well. The command you want is called AP_AUTOTHROTTLE.


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Mike
Sent: 14 October 2005 16:09
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Autopilot APPR HOLD problem

For one sector of my FPI session on Wed evening I flew the Cessna Citation by VENEAVIONES in JHB livery, with panel by Brian Williams. Unfortunately, I discovered that APPR HOLD didn't work (at EGTE). Can someone with more expertise than me in this area tell me if this is a problem somewhere in one of the config files (aircraft.cfg or panel.cfg?) that can be easily fixed?

Still coming to terms with the new GoFlight autopilot module, in
particular the apparent lack of an autothrottle arm switch.
Only an IAS/Mach Hold and although I have configured one of my
P8 buttons as A/Thr Arm it doesn't seem to activate and I have
to resort to Ctr+R
- which rather defeats the purpose of this all-singing,
all-dancing autopilot module (I can even get BBC2 on it ....

Mike L

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