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craigt47

FD and VS on JS41 Problem

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Hi guys,

 

First off, you have got me as a customer for life this product is my first and is just simply amazing. However, an odd problem has developed that i have no seen before and i cannot shack it (even after a full install).

 

After take off 150 Vr get to about 500ft when we are 170knots set IAS and the autopilot does not seem to want to follow the FD. The FD rises and the plane just stays at the same high. During turns on SID's you will loss alt durning the turn not gain any. Really odd becuase i never seem to have this problem before.

 

Just so you know, autopilot is on, VS selected, Alt arm, alt wheel set to right alt and the VS set to aroundd 1700.

 

Oh should add that FD does not follow in IAS or VS - little confusing above. The example i gave was VS dep = same problem

 

And rven now when writing VS set at 700 climb and we are climbing at 10ft vs!

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Just to ask the obvious, is your autopilot green rectangular lights in the center console actually on? Also, is your power sufficient to achieve the climb...e.g. after you engage, does it attempt to climb and then airspeed fall off or is the airspeed still accelerating?

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On initial climb, I will set V/S to 1000 to 1200 fpm and let speed build to 170 then change mode to SPD hold. Trying to hold 1700 fpm climb is basically unrealistic.

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A screenshot would really help. If it's persistent after a full reinstall, it sounds more like a human factors issue.

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I guess you switched the A/P on while descending.

Correct the vario value to a possitive value with the A/P finally on.

Or manage to switch the A/P on while really climbing.

 

Also I miss a possitive feedback without looking down to the pedestral that the A/P is really on.

In some attitudes (see also 737NGX) the A/P does not become active.

 

Edit: Have you retracted the flap shortly before?

 

Quote from the Tutorial:

 

First, flaps 9 produces a significant increase in lift produced by the wing. If you are flying along in stable flight and select FLAPS 9, the airplane will balloon dramatically. You can counter this quite easily by anticipating the balloon and putting forward pressure on the controls, but you will need to trim out the control forces to maintain level flight. The opposite is true when retracting from FLAPS 9 to FLAPS UP- you will notice a strong pitch-down tendency so be prepared and retrim the airplane as needed.'

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Sorry guys, but this is not a pilot error as i never had this problem before. It started on a re install. Any idea?

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Craig,

no re-install!

Make sure after take-off that after flaps-up you still climb, switch the A/P only with a possitive climb (ie. no descend) rate.

Release the yoke and see whether the A/P is really on.

If you caught a negative value (descend), correct it with the little pitch wheel left of the A/P button.

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Andreas,

 

Thanks for you help. However, this will no work as the plane will not follow the fd in the climb or desent. I think it is a trim & ap problem. I am going to email pmdg support and see what they say. Thx guys

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Fixed! Installed the service pack, even thought it said it was upto date and it has fixed the problem.

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Hmmm...I never installed that since it said mine was up to date...

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Craig,

 

fine, however, IMU the J41 has *no* full VNAV mode, has it?

I think the FD will show you to climb more or less to hit a given (programmed)I altitude at a given waypoint,

but the A/P won't do it by itself.

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Sorry but i am unsure how i can make this clearer. IN V/S mode you set a climb of say 1500ft. The FD will be at that pitch so the plane can meet that request untill this is changed. The problem, i am still having after the update (so not fixed) is that the AP will not follow the FD (as per the title). It is not pilot error, i understand that this is not a 737 "push button" and off you go, I understand the JS41 does is not ment to climb at 1700ft as the 737 and other jets and yes the green light is on! LOL. Sorry guys, i thank you for your suggestions and help. But, i do know how to fly the plane i have been for some time very well. This just started the other day after a re install due to another system error.

 

So just to explaine i am climbing at 194konts, FL140 on V/S 700 set with the green light (autopilot) on and the V/S intercator is 500 ! Eh why!

 

Any suggestions please do reply.

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Wait. Why does your V/S on the EADI have a down arrow (indicating descent)?? Lower right corner. It should have an UP arrow. Turn the dial the other way.KXtcx.jpg

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Because that was a pic from another time at the top of the forum. However, it does not explain why 700 is set and 1000 and inreasing down is showing

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OK. Getting confused between the description of the problem and the pic.

 

I just ran some experiments on my own sim and it did what yours is not doing. (I habitually press AltSel so I had to confirm how it would behave the way you do it.) I didn't touch the trim, used both IAS and V/S and the FD followed perfectly. The only thing I would suggest at this point is another reinstall.

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Folks,

 

again, the J41 does *not* provide a VNAV mode as eg. the 737NGX.

It will climb as set, IAS or V/S.

If you descend while switching on the A/P, it will capture your actual descend rate.

 

So, what is the problem here? As Gregg I am confused.

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This is more simple then you think! LOL. The plane will not hold the requested VS via the AP. I understand there is no VNAV. As you can see from the pic above i have requested a 700 down VS with autopilot on. However, the plane is decending at 1000 VS down. Basically the plane will not hold or follow the VS when on AP. The FD shows the correct VS attitude. But, the plane just will not follow the requested command. I have rasied a ticket and will report back.

 

Thanks again

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G'day Craig. In your screen shot, I don't see the ALTSEL enabled. Is that correct?

 

The format for any vertical change with the AP is: First select your desired altitude, then press the ALTSEL button, then select either V/S or IAS as your prefered mode, then use the AP trim wheel to select the desired rate of V/S or IAS.

 

I made this mistake (again) this afternoon and my PAX complained all the way down ;-)

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The format for any vertical change with the AP is: First press the ALTSEL button, then select either V/S or IAS as your prefered mode, then use the AP trim wheel to select the desired rate of V/S or IAS.

 

Yeah, that's the format in the tutorial but I tried out what he was doing on my system and it worked well. I think there's just something up with his system.

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Same here, I did not need to have ALT SEL to enter and hold a V/S - I have never used this method before. If using the A/P, I rather climb on IAS (instead of V/S); I use V/S on descent.

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Gregg and Frank - that method would make sense if you did not want to capture an altitude. I will try that out for myself.

 

So, maybe this AP is like the one on the C337, where the AP captures the current climb/decent rate when you select the AP to "ON" and only changes when you use the thumb wheel ???

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Yeah, that's the format in the tutorial but I tried out what he was doing on my system and it worked well. I think there's just something up with his system.

 

I can confirm that my J41 works like you said Gregg (and Frank). I had never tried it that way before. To me, that makes it much easier when using the AP to climb/descend as you can take a little longer to select the required altitude before pressing ALTSEL.

 

So the OP must surely have a local problem with his setup ... unless we're missing something :Nerd:

 

Hope you get it sorted Craig.

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The V/S hold is a great feature, but watch it during your climb as you may find yourself with an uncomfortably low airspeed, or a stick shaker, demanding your best pilot stuff and making some unhappy paxs hihihi!!!

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TUT TUT! Human factor! LOL. I will get a screen for you in 20mins.

 

Work in either the aviation or training field for a day and you wouldn't be laughing so hard.

 

Every day, it's the same:

"IT'S NOT WORKING AND I'M DOING IT EXACTLY THE WAY IT SAYS TO DO IT!!!"

[*Walk over*]

Show me how you're doing it.

[*Observes them skipping steps*]

Ah, that's why. Make sure to click here and here before trying the next step.

"Oh..."

 

 

 

Your screenshot shows that you have the right buttons pressed, but it seems that something is messing around behind the scenes. Do you have any trim axes assigned on your joystick?

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