[jhb_airlines] Re: Autopilot APPR HOLD problem

  • From: Gerry Winskill <gwinsk@xxxxxxx>
  • To: jhb_airlines@xxxxxxxxxxxxx
  • Date: Tue, 18 Oct 2005 15:05:59 +0100

I wasn't really interested in climbing at that speed, rather looking at the throttle / power setup. Although the FS9 a/c clearly has the power to climb at the higher speed, it doesn't attempt to go for full power, to try to achieve it. It opens only to 65% thrust and doesn't fully open the throttles either. This despite my fiddling the Aircraft.cfg to accept 108% for Autoothrottle.
Is there a max limited climb speed built into one of the two files? Intriguing.

Gerry Winskill

Bones wrote:

The normal climb speed for this aircraft is only 150kts IAS - it's Max
Operating Speed is only 262kts IAS so you are trying to push it beyond it's

Don't forget that Cessna originally designed it as a sort of jet engined
version of the King Air - a not very fast aircraft with the short field
capabilities of a turboprop. They thought that owners would prefer a jet
rather than a turboprop and that the Citation might eat into the King Air
market - which it did beyond their expectations. Think of it more as a jet
with turboprop performance.

I've sorted the roll and speed problems - no need to touch speedbrakes
unless you want higher than a 1500fpm descent.


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill
Sent: 18 October 2005 10:11
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem

I'm beginning to suspect there is something odd about this aircraft. Another FS9 lockup, over Turnberry, en route Glasgow. FS9 then refused to reboot, from the saved situation. Starting from a situation with a different aircraft was OK.

Back to your thrust problem. I tried climbing, on AP, at 280 kias. It
wouldn't go above 265 kias, even though only using about 65% thrust. On
another check, it was rock solid on the GS, at 105 kias. It's quite
reluctant to slow down to that speed and probably needs airbrakes deployed.
At these speeds, with balanced fuel load, it's roll rate is
disappointingly slow.

Gerry Winskill

Bones wrote:

At 85kts you are probably pushing into the stall envelope. The CJ1
table give a stall between 70 and 86 so that means minimum approach of
87kts to 107kts. Add maybe 5kts for the CJ2 which is about 35% heavier.

I've now got the thrust and balance working to a reasonable level and
100kts approaches are fine. The CG was indeed well out and once brought
back towards the wing the aircraft started to behave properly.
Unfortunately, as I warned Mike, it's opened up a few more cans of
worms because the rest of the aircraft's values are written around the
bad CG position.

Problem one cropped up after I decided to try a full weight landing
instead of the half empty weights I had been testing it with. At half
weight trim was nicely set up around 0.8 with this rising to about 1.7
at the lowest speeds. As soon as I put in 55% fuel (it can't go much
higher than this or you get an overweight landing) the pitch trim
jumped to a silly figure of about -4.2. This means the fuel tanks also
need shifting relative to the new CG - they should have minimal effect
on trim.

The second problem is more obtuse but it's down to the same thing. On
touchdown the aircraft now slams the nosewheel hard onto the surface
and it either breaks or starts a severe oscillation. I guess moving the
fuel tanks may cure this but I dread to find out what other secondary
problems will result from this..

I'm temped to go back to the original and just fly coupled approaches
at 120kts.. Or maybe buy the Eaglesoft version..


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill
Sent: 17 October 2005 19:34
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Autopilot APPR HOLD problem

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

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