Jump to content

Practicing FBW


Tim Capps

Recommended Posts

For all its flaws, I still find myself coming back to this airplane. One thing I've noticed is that I just don't know how FBW works. The more I practice, the better I am getting at it. Automatic flight still needs to be slower on the descent, and I hope they address that, but despite my frustrations I'm still flying it.

Link to comment
Share on other sites

For all its flaws, I still find myself coming back to this airplane. One thing I've noticed is that I just don't know how FBW works. The more I practice, the better I am getting at it. Automatic flight still needs to be slower on the descent, and I hope they address that, but despite my frustrations I'm still flying it.

What I find kind of funny is that in one thread here somebody linked a youtube video of an Airbus take-off. I think it was one of those threads moaning that it can't be flown or something silly like that. Anyway, the video very, very clearly demonstrated the vast amounts of control inputs used from rotating, climb out, clean up and joining the SID and then finally after all that hand flying, actually activating the AP.

The point being that a lot of small inputs are used to fly an Airbus it seems.

As for FBW; I think the main features would be the protections provided i.e. the computer will not allow excessive pitch or roll, will apply power when speed is too low, will ignore pitch inputs that are excessive and could lead to say a stall. It gets really pissed at anyone slamming that stick around. Small inputs and lots of them.

Aside from the somewhat annoying pitch change on AP disconnect, I don't really see what all the fuss is about (not addressed to you Tim). I'm using a X-52 with all default settings, no FSUIPC and no problems with take-off, approach or landings. So, if anyone has that big an issue, I can only assume something is different, but that difference isn't the Airbus X. As for the AP off/pitch issue, this is actually caused by the way that FS has always (yes, always) controlled an aircraft with the AP; it uses trim and of course when you couple that with the way FBW works i.e. with zero trim.....well there's always going to be a problem, but it lasts for what, a second or two? If you know it'll do it, surely it's just a case of being ready to give a small pitch input to counter it?

The product basically does what it was always intended to do and does it whilst looking very nice too.

Hopefully, a more advanced version will come along that uses C++/GDI/Vector gauges etc and that will allow a lot more to be done.

Oh, and the main question Tim, "how does FBW work"; in the way that MS implemented it........I don't think anyone does know!

Link to comment
Share on other sites

What I find kind of funny is that in one thread here somebody linked a youtube video of an Airbus take-off. I think it was one of those threads moaning that it can't be flown or something silly like that. Anyway, the video very, very clearly demonstrated the vast amounts of control inputs used from rotating, climb out, clean up and joining the SID and then finally after all that hand flying, actually activating the AP.

The point being that a lot of small inputs are used to fly an Airbus it seems.

As for FBW; I think the main features would be the protections provided i.e. the computer will not allow excessive pitch or roll, will apply power when speed is too low, will ignore pitch inputs that are excessive and could lead to say a stall. It gets really pissed at anyone slamming that stick around. Small inputs and lots of them.

Aside from the somewhat annoying pitch change on AP disconnect, I don't really see what all the fuss is about (not addressed to you Tim). I'm using a X-52 with all default settings, no FSUIPC and no problems with take-off, approach or landings. So, if anyone has that big an issue, I can only assume something is different, but that difference isn't the Airbus X. As for the AP off/pitch issue, this is actually caused by the way that FS has always (yes, always) controlled an aircraft with the AP; it uses trim and of course when you couple that with the way FBW works i.e. with zero trim.....well there's always going to be a problem, but it lasts for what, a second or two? If you know it'll do it, surely it's just a case of being ready to give a small pitch input to counter it?

The product basically does what it was always intended to do and does it whilst looking very nice too.

Hopefully, a more advanced version will come along that uses C++/GDI/Vector gauges etc and that will allow a lot more to be done.

Oh, and the main question Tim, "how does FBW work"; in the way that MS implemented it........I don't think anyone does know!

Sounds really cool! I guess my FBW computer just really gets pissed off from my hand flying and decides to just nose dive to shame me for even thinking about not engaging the AP... When my bus nosedives no control input adjusts anything. No small inputs, no full deflection... Nothing gets that nose back up except for time. Disabling the FBW SEC1 system makes it fly pretty well, though. Go figure.

Link to comment
Share on other sites

Sounds really cool! I guess my FBW computer just really gets pissed off from my hand flying and decides to just nose dive to shame me for even thinking about not engaging the AP... When my bus nosedives no control input adjusts anything. No small inputs, no full deflection... Nothing gets that nose back up except for time. Disabling the FBW SEC1 system makes it fly pretty well, though. Go figure.

As I said, I'm using the same install as everyone else (1.21) and have no idea what this "nose dive" is all about.

Forget turning the FBW off, forget the AP. Set the load to 50%, fuel 20%. Enter the runway heading and ILS freq for whatever airport you're at and on the PERF page check your VAPP speed. Put a speed of 180 in the AP and flaps 1, get on the runway and give it TOGA.

Now after a few hundred feet of climb, gear up, throttle to CLB, pull the speed knob and pretend it's a fast Cessna and hand fly to 2,000ft, do a left 180 to downwind etc, etc. (leave the flaps at 1 and speed at 180)

Once back on the localizer (call it 10 miles out to get some space), as the Glideslope comes alive, dial in the VAPP speed, gear down and flaps as required during the descent.

Now, at what point did your nose dive with you having no control?

Link to comment
Share on other sites

As I said, I'm using the same install as everyone else (1.21) and have no idea what this "nose dive" is all about.

Forget turning the FBW off, forget the AP. Set the load to 50%, fuel 20%. Enter the runway heading and ILS freq for whatever airport you're at and on the PERF page check your VAPP speed. Put a speed of 180 in the AP and flaps 1, get on the runway and give it TOGA.

Now after a few hundred feet of climb, gear up, throttle to CLB, pull the speed knob and pretend it's a fast Cessna and hand fly to 2,000ft, do a left 180 to downwind etc, etc. (leave the flaps at 1 and speed at 180)

Once back on the localizer (call it 10 miles out to get some space), as the Glideslope comes alive, dial in the VAPP speed, gear down and flaps as required during the descent.

Now, at what point did your nose dive with you having no control?

Thanks Paul for the post. I have been keeping up with the forum waiting for the Box/Cd edition to arrive in my mailbox. I made the mis-step of pre-ordering and got stuck in the long line of those of us that have to wait it out. But, I hear a rumble that it is actually shipping with v 1.21.

I did a screen capture of this post and now I have a ready made, simple tutorial to try out immediately after loading. Thanks for the details.

Ray

Link to comment
Share on other sites

As I said, I'm using the same install as everyone else (1.21) and have no idea what this "nose dive" is all about.

Forget turning the FBW off, forget the AP. Set the load to 50%, fuel 20%. Enter the runway heading and ILS freq for whatever airport you're at and on the PERF page check your VAPP speed. Put a speed of 180 in the AP and flaps 1, get on the runway and give it TOGA.

Now after a few hundred feet of climb, gear up, throttle to CLB, pull the speed knob and pretend it's a fast Cessna and hand fly to 2,000ft, do a left 180 to downwind etc, etc. (leave the flaps at 1 and speed at 180)

Once back on the localizer (call it 10 miles out to get some space), as the Glideslope comes alive, dial in the VAPP speed, gear down and flaps as required during the descent.

Now, at what point did your nose dive with you having no control?

Hi Paul,

I am at work now (blush), and I cant go make a new testflight right now, but I will share with you what I experienced the first few flights:

Aircraft is in it's standard config (engines running, pneumatics and hydraulics set, lights etc). I use the connector to set loads and fuel. I set approx 20% fuel and medium load. I program the FMC with cruise alt, TL, flaps 2 takeoff, calculate V1, VR, V2, set the speed dial on the MCP to V2 +5, set the init climb to my cruise (because no online atc available), input the flightplan inlcuding SID and expected arrival. Set the NAVRAD to GWS (111.30) for the ILS 01L for ENGM (my arrival airport at Oslo, Norway). The FBW systems are set untouched. They are in their standard ON config. Flaps 2. Anti ice on as required (getting cold here in Norway). Taxi to the runway, line up. Full throttle and rotate by pulling back on the stick. The aircraft feels heavy. Very heavy. Pull back by an unusual large amount to get any effect. Positive rate of climb, gear up. The SID calls for a right turn at 800 ft. I give gentle inputs to the right on my stick. Hardly any reaction. I have to give it full deflection to the right to get any proper response from the aircraft. Flaps 1. If I remember correctly the aircraft made a large nose up or nose down at this point. No matter how hard I pull or push the stick, nothing seems to make any slightest difference in pitch. Finally, she starts to react after a few seconds. Continue my climb. Flaps up, clean up the aircraft. Having a real hard time getting proper pitch and roll control. She either does way too little or way too much in relation to what I intend. I set the AP on, and she follows the Lnav path correctly. Btw, the FD on the PFD does not indicate the proper roll input. It's direction is seemingly uncorrelated with the programmed path in the MCDU - untill you engage the AP. Then the FD will harmonize with the AP.

Descent: Disconnect the AP when leaving the final point in the STAR heading towards the FAF to intercept the ILS. Altitude is about 5000 ft and descending with approx 1800 ft at this point (seems like its the standard descentrate for the Airbusx). Approach mode is initialized and confirmed, meaning the AT will automatically decrease airspeed as the flaps go down, and set VAPP with full flaps gear down. As I approach 4000 ft wich is my alt select altitude and the LLZ intercept altitude, the nose dives again. Uncontrollable. I loose around 1000 ft or more. I cant remember if I had set flaps 1 at this point. This happens at least one more time, and I have the darndest time trying to manually capture an altitude. When she approaches a set altitude, she starts to nose dive when coming from above going down. Coming from below she starts to nose up when nearing the alt select. I manage to save her, and intercept the ILS. Get on the glidepath. Flaps 2, gear down. Flaps 3, flaps full. Speedbreaks armed. She is nearly impossible to keep stabile on the final. Inputs are increadibly slow, and she starts to do things I havent given any inputs in that direction (mostly nose up or down). As I get very close to the ground (like a couple of hundret feet) she starts to react much more smoothly. Im thinking maybe its the ground effect. I make a pretty ok landing with her, but I would think most of my passengers are dead from fright already.

Did the same trip with SEC1 disabled, and she flies like a charm. She responds correctly to all inputs. I can make minute corrections, and she flies them well. A lovely girl to land! The ground effect seems to make it easy to grease the landings. Love it!

My equipment:

CH yoke

CH pedals

Registered FSUIPC

ASE (latest version)

EFB from Aivlasoft

REX

+++

Link to comment
Share on other sites

I was practicing at Aerosoft's Funchal with the Airbus X and this is what I observed. Small slow inputs are rewarded by steady flight. You don't have to keep after the stick. Once the airplane is doing what you want it to do, e.g. climbing, turning, you can take your hand off and it will continue. In other words, it doesn't fly like the non-FBW airplanes you have. Not at all.

Most of the time I was able to land just fine, but a couple of times I experienced the nose dive, which took me right into the bank just before the threshold. About 300-400 feet the nose goes down and nothing will bring it back up. Imagine if the trim were rolled all the way nose down. That's the way it is.

It seems to me that if I am set up properly, I don't get the nosedive. But if I am coming in too high and have pushed over to capture the glideslope, that "carries over" somehow. Has anyone noticed if the trim becomes active after the nosedive happens? I'm wondering if FBW doesn't have something to do with the trim and it is not necessarily reset to neutral when you reach the altitude that triggers the FBW to do whatever the crazy thing it is doing at very low altitude.

The lighting effects and beauty of this airplane keep drawing me back despite the issues. It does seem the more I fly it, the better I am able to enjoy it.

As for difficulty taking off, I don't experience that heaviness at all. It rolls up smoothly for me and climbs perfectly. Likewise banking. I wonder if it is a joystick setup issue?

Link to comment
Share on other sites

Ok made a new testflight. This time I decided to leave SEC1 online. Long story short - she performed well except for 2 things:

1. Approaching ALT SELECT the control inputs just did not work predictable. About 200 ft from intercept she became nearly uncontrollable. The plane got a signficant nose down tendency. Instead of pulling hard on the yoke this time, I decided to rapidly bring the yoke all the way back, and releasing, and all the way back again. Can describe it as "pumping" the yoke to the full back position and relaxing - in rapid succession. This kept the aircraft from decending too much, and I think I only lost a couple of hundred feet. However, I decided to disengage SEC1 for a while to get her back under control. So from this experience I gather that the real problem arises when intercepting an ALT SELECT. Otherwise, the FLB is (almost) fine.

2. After re-engaging the SEC1 during decent, and having the ALT SEL to 1000 ft BELOW my target altitude, I didnt have big problems flying her straight and level at 4000 ft (alt sel = 3000 ft). On the glidepath I noticed that even though pitch was somewhat maintained during a slight right bank, the aircraft had a very noticable tendency to pitch down AFTER a slight left bank. Tried to trim to no avail. This meant keeping a decent profile got pretty hard. And when I say slight bank, I mean S L I G H T! The bank to the left was hardly noticable, but the pitch down afterwards did occour 100% of the time. It was, however, very predictable and pretty straight forward to compensate for.

Sat her down nice and comfy, and the FBW testflight was far more successful this time around. But its far from perfect, and I do feel I am flying a beta product.

  • Upvote 1
Link to comment
Share on other sites

Did the same trip with SEC1 disabled, and she flies like a charm. She responds correctly to all inputs. I can make minute corrections, and she flies them well. A lovely girl to land! The ground effect seems to make it easy to grease the landings. Love it!

and what is SEC1 ???

Ray

Link to comment
Share on other sites

@Ray: It's one of three fly-by-wire buttons at the overhead panel on the left side. Normaly all three FBW computers should be set to on, but SEC1 does not really do what it should. With SEC1 disabled the Airbus X is flyable by hand but it's as far away from real FBW as with enabled SEC1.

Link to comment
Share on other sites

@Ray: It's one of three fly-by-wire buttons at the overhead panel on the left side. Normaly all three FBW computers should be set to on, but SEC1 does not really do what it should. With SEC1 disabled the Airbus X is flyable by hand but it's as far away from real FBW as with enabled SEC1.

Thanks, HopeFly.

Link to comment
Share on other sites

I've been practicing at Funchal. No autopilot, just taking off, circling around, and landing. I'm sorry to report that about the point the announcement "400" is made the bottom drops out, the plane sinks and becomes completely unresponsive to control input. Pull the joystick all the way back -- doesn't matter; might as well be pushing it all the way forward. Crash is inevitable. Whatever fly-by-wire is, it can't be that. I've concluded the attempt to implement fly-by-wire in this airplane is a failure and further efforts at practice would be a waste of time. I'll try disabling it and see what happens, but I wanted something different.

  • Upvote 1
Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. Privacy Policy & Terms of Use