[jhb_airlines] Re: Autopilot APPR HOLD problem

  • From: "Bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Sun, 16 Oct 2005 19:45:26 +0100

That's quite easy to do in XML and can be found on any proper DME kit which
is fitted to an aircraft. Designers tend only to show DME distance on their
gauges but a proper DME unit will give distance, TTS (time to station) and
groundspeed as alternatives. I have built these into the Aztec panel already
and it works whether you have an ILS or VOR selected.


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill
Sent: 16 October 2005 17:07
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem

The panel I'm using has a very interesting gauge;
ID_222_DME_PNL!ID_222_DME_PNL. Not only does it read DME BUT, with
aircraft on ILS, it gives Time To Landing, in minutes. Unfortunately it's
not an .xml gauge, so I can't learn from it.

Gerry Winskill

Gerry Winskill wrote:

> Back on the first panel, for a series of checks.
> Firstly, the difference in aileron performance are definitely caused
> by fuel tank levels. With both tanks the same the roll rate in each
> direction seems to be the same. Reduce the level in one tank and it is
> reluctant to roll in that direction. It's very sensitive to fuel
> weight imbalance, so the panel definitely needs a tank selector
> switch. The panel I'm using, which looks reasonably like your
> screenshot, has decent tank level gauges.
> Autopilot Alt is very speed sensitive. In landing configuration, if
> speed falls below 120 kias then it cannot maintan the set altitude.
> The Autothrottle doesn't seem to react adequately to this. with AP
> disabled then it's possible to hold a required altitude, using manual
> throttle and trim.
> With APPR selected, it captures the Localiser OK but immediately
> disables the Alt Hold and sinks rapidly. If the Alt button is
> re-selected, the descent can be arrested and altitude regained. It
> didn't automatically capture the GS, when approached, until ALT and
> APPR both disengaged and APPR re enabled.
> Descent with GS ok until speed reduced to 115, at which point it
> atarted to descend too rapidly. It was easy to fly the ILS manually,
> after this point but the Autothrottle couldn't hold speed down to 115
> kias, whereas manual throttle control made this possible.
> The descent / speed scenario may be weight related; I'll try lower
> weights later, since these checks were carried out with full tanks and
> I haven't yet looked up the real life Max Landing Weight.
> I'll also try the effect of substituting the Falcon's Autopilot,
> though two of us have had basically similar results, using different
> panels.
> Meanwhile it seems the trick may be to fly the ILS at about 130 kias,
> until something like 3 DME, reducing to the correct landing speed only
> after disengaging AP.
> Gerry Winskill
> Gerry Winskill wrote:
>> And here was I, about to start trying this panel....
>> I'm off to try another idea, to correct the difference in roll rates.
>> It suddenly struck me that I uploaded the Citation after using a
>> light single. Now one of FS9's foibles is that if you take that
>> route, it often draws only from one fuel tank. In FS2002 it was
>> possible to select both tanks on, from the Aircraft, Refuel menu. In
>> FS9 that option is no longer there. I normally get round the problem
>> by fitting, if not already there, a fuel tank selector switch,
>> incorporating "both". I hadn't done this with the Citation. If it's
>> sensitive to weight distribution, then that might account for odd
>> roll behaviour.
>> Gerry Winskill
>> 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
>>>>> 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
>>>>>     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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