[jhb_airlines] Re: Autopilot APPR HOLD problem

  • From: Gerry Winskill <gwinsk@xxxxxxx>
  • To: jhb_airlines@xxxxxxxxxxxxx
  • Date: Mon, 17 Oct 2005 17:54:37 +0100

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..

bones

-----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
down.

bones

-----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 CJ1!

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 these.

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?

bones

-----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


Bones

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
-

[Flaps.0]
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 visually..

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.

bones

-----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 ELEV
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.

bones

-----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.

bones

-----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


bones

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 not.

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 gauge.

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.

bones


-----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


bones

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
function.

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


doesn't








activate the IAS/Mach hold (yes, I have designated the correct
function in GF config).  I can only get IAS/Mach hold to work
using
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)
max_indicated_speed=350.453125
max_mach=0.75

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

Confused.

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 available.

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.

bones

-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Mike
Lucas
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 .... <g>)

Mike L





































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