Drifting on the runway when taking off

[Stanley777]

Hi everyone,

 

I find that, as I am rolling down the runway to take off, my aircraft starts drifting left or right before I attain lift. This happens no matter what the weather is (so it happens even when I set weather to clear skies) and with almost any aircraft that I use. The only plane in which this phenomenon seems not to occur is the default Microsoft FSX Boeing 747.

 

As the aircraft starts drifting, I need to try to keep it straight by use of the rudder, and keeping it straight is very difficult.

 

Am I doing something wrong? Or does this happen in an actual takeoff, and the flight simulator is correctly modeling reality? Is there something I can do to mitigate the situation?

 

Thank you.

 

Stanley

[Talon90]

Hi Stanley,

 

In propeller driven aircraft (most notably single engine aircraft) the effect you are experience is very real. As the propeller rotates it causes a flow of air towards the rear of the aircraft all while swirling around the fuselage. This air, as it spirals around the fuselage will strike the side of the tail (empennage) and cause the aircraft to yaw to the left under power. This yaw motion must be counteracted with right rudder. Very real.

[mallcott]

Hi Stanley,

 

In propeller driven aircraft (most notably single engine aircraft) the effect you are experience is very real. As the propeller rotates it causes a flow of air towards the rear of the aircraft all while swirling around the fuselage. This air, as it spirals around the fuselage will strike the side of the tail (empennage) and cause the aircraft to yaw to the left under power. This yaw motion must be counteracted with right rudder. Very real.

 

Sort of. Not all props rotate in the same direction and the cause can also be torque effect at low speed where the rudder lacks sufficient authority to counteract the torque steer.

[Stanley777]

Hi Talon90,

 

Thank you for your reply.

 

OK. So that explains propeller aircraft.

 

But I am seeing the same phenomenon with jet aircraft as well -- the Airbus A321, the Boeing 737, the Bombardier CRJ, and the Learjet. Any thoughts on that, please?

 

Stanley

[PhantomTweak]

If it's happening with a jet, there are 2 possibilities I can think of. First, your controller isn't properly calibrated, causing one side's engine(s) to produce more power than the other's, thus causing the drift.

Second, you rudder is either trimmed off to one side, or is stuck slightly off center. Make sure your rudder trim is zeroed, AND "wipe" the controls before you start your roll. Move your controller all the way around, full up, full down, full roll left and right, and waggle the rudders. A good take off always includes a good rudder-waggle! :D

One thing you can do to see what's happening is to go to chase plane view and look at your rudder(s) from directly abaft (behind, in Navy-ese :D ), and see if it's centered up before you start your roll. If it's not, make sure the yaw damper on the AP is off, ctrl+D iirc, and that it's centered up. If not, either trim it, or adjust your controller's calibration to make sure that when your rudder control is centered, your rudder is.

Hope something in all that babbling helps a little...

Pat☺

[johnost]

As Pat says take a rear view of your rudder prior to, and during takeoff. I have experienced similar problems to yours on several occasions over the years, and in each case I found a malfunctioning rudder controller - pedals or joystick twist. Symptoms varied from slow drift to the left to erratic behavior or only full left or full right rudder. Over the years I have gone through 2 sets of CH pedals and 3 joysticks all with rudder function failure.

[Stanley777]

Hi everyone,

 

Thank you for your replies.

 

Is there a simple command to center the rudder and thus remove rudder trim.

 

I know the buttons to use on my joystick to adjust elevator trim, but I don't know the button to adjust rudder trim.

 

Stanley

[okbob]

Also check for crosswinds.

[Talon90]

Sort of. Not all props rotate in the same direction and the cause can also be torque effect at low speed where the rudder lacks sufficient authority to counteract the torque steer.

 

Since this is a flight simulator forum and not a flight forum and since the OP made it clear that they weren't even aware that such a force of flight dynamics existed, I tried as best I could to give a simplified, plain English explanation for one possible cause of the phenomenon he was experiencing without getting in to all the possibilities like counter-rotating propellers, gyroscopic precession, P-factor, variable pitch propeller dynamics, vortices and torque that could contribute. Not to mention asymmetric thrust, differential break loading, crosswinds, etc. I should have also mentioned all of the various simulated control input issues as mentioned above in the subsequent posts but I didn't. I too am a former real world pilot but try to find ways to help new people out with out intimidating them or trying to come across as superior. I'm new here but not to the hobby or the world of aviation by a long shot. I was simming with the first Bruce Artwick Organization simulator and It's been 32 years since I logged my first PIC hour.

[mallcott]

Since this is a flight simulator forum and not a flight forum and since the OP made it clear that they weren't even aware that such a force of flight dynamics existed, I tried as best I could to give a simplified, plain English explanation for one possible cause of the phenomenon he was experiencing without getting in to all the possibilities like counter-rotating propellers, gyroscopic precession, P-factor, variable pitch propeller dynamics, vortices and torque that could contribute. Not to mention asymmetric thrust, differential break loading, crosswinds, etc. I should have also mentioned all of the various simulated control input issues as mentioned above in the subsequent posts but I didn't. I too am a former real world pilot but try to find ways to help new people out with out intimidating them or trying to come across as superior. I'm new here but not to the hobby or the world of aviation by a long shot. I was simming with the first Bruce Artwick Organization simulator and It's been 32 years since I logged my first PIC hour.

 

Not interested in the bragging rights. Only in the factual nature of the assistance. Yours was partial and, as we are now discovering, wrong. As was mine.

Perhaps the OP should state his issue in a far clearer manner? There's a reason we ask for full disclosure.

[mallcott]

Hi everyone,

 

Thank you for your replies.

 

Is there a simple command to center the rudder and thus remove rudder trim.

 

I know the buttons to use on my joystick to adjust elevator trim, but I don't know the button to adjust rudder trim.

 

Stanley

 

Yes, numpad `5` (with numlock OFF) centres everything.

Rudder trim can be set to any keys you like - suggest using the left/right arrows.

 

Also, LIST your hardware so we know whether we're talking abut rudder pedals, twistgrip joystick, yoke or just keyboard controls.

 

You can't expect a definitive answer without putting some effort into explaining the problem and the background to it.

 

For example: okbob has mentioned weather. What weather engine are you using? Crosswinds and gusts could easily explain what you are seeing. Especially if an aftermarket weather engine is in use...

[mrzippy]

Hi everyone,

 

Thank you for your replies.

 

Is there a simple command to center the rudder and thus remove rudder trim.

 

I know the buttons to use on my joystick to adjust elevator trim, but I don't know the button to adjust rudder trim.

 

Stanley

 

Numpad 5 will center all controls.

[BobSeaman]

All of the suggestions in this thread are good. :pilot:

 

In particular, did the drift effect just start to happen recently?

Its very possible its caused by the rudder calibration going wonky.

This can happen for several reasons:

 

Physical wear on the rudder's position sensor(s) or a sensor becoming loose is the usual cause, in my experience. In most cases you can fix it but you'll need to take your rudder apart and re-assemble it.

 

Large (and sometimes not-so-large) changes in hard drive/ssd free space (ie, virtual RAM) or RAM usage. This shouldn't matter, I know, but I've seen it happen several times on different versions of Windows. Win just seems to hit a "tipping point" or "point of no return" after a while and it throws off some settings.

 

This can also happen if you've recently made changes in video settings or changed out a GPU card.

 

As stated earlier, go to your outside view and really zoom in on your plane's rudder.

Move the rudder left and right, using slight-to-full throws. Really pay attention to the rudder's movement in the outside view. Are full throws the same for both sides? Does the rudder re-center when you leave it alone? Does the rudder drift left or right with no pressure on it?

 

Try doing a calibration in the sim (and outside the sim if your rudder's software has that available). You should be able to see if the calibration settings have changed a lot. Does the re-cal fix the problem or not? Does the rudder drift come back over time?

[Stanley777]

Hi BobSeaman,

 

When you say that I may need to take my rudder apart and reassemble it, do you mean take apart my joystick?

 

Stanley

[BobSeaman]

I don't know, you haven't mentioned what you're using yet and I've mis-placed my Miss Cleo hat. :p

 

:)

 

Just keep it simple at first. Trouble shoot the easy stuff first before you commit to taking anything apart.

The first question you should ask yourself is what's changed since you noticed the problem? Have you updated any hardware on your PC? How full is your hard drive or SSD? Have you made any large changes in stuff like sound files or display settings?

 

Better yet, start by doing a calibration on your joy stick/yoke/rudder set up. That may fix it directly, in which case you're done. It might fix it for a while. Or it might not fix it at all.

The results of doing the calibration will tell you what to look at next.

[ScatterbrainKid]

Is there a simple command to center the rudder and thus remove rudder trim.

I know the buttons to use on my joystick to adjust elevator trim, but I don't know the button to adjust rudder trim.

Stanley

 

1- I think the default "centralise trim" key is numpad 5, but flights should already be starting with the rudder centralised. Go to external view and see if the rudder is offset to one side. If it is, just waggle and twist your joystick to "free up" the rudder and let it return to centre.

2- Un-tick the 'Autorudder' box because it could cause conflicts between the rudder and ailerons that might prevent you turning on the ground.

3- Kill all wind so you won't have a crosswind pushing your tail to one side.

[napamule2]

SBKid : 'Un-tick the 'Autorudder' box..' +1

 

After you calibrate your controllers, you need to go un-check the 'Auto Rudder' as this will tie your rudder to the aerlions and this will make using the rudder very difficult. That's all that is 'wrong'. And to use the Numpad 5 for centering your numpad Num Lock has to be OFF. And using differential braking will also help control the drift. Tap the brakes when rudder is deflected to invoke Differential Braking. TAP the brakes but don't hold.

Chuck B

Napamule

[PhantomTweak]

Another thought struck me, and it hurt, too! :D

Is you default flight the native default, or did you save another flight as default? I'm thinking perhaps, maybe, the default flight's plane had the AP on and set for a different heading than you new T/O runway's. If it's not, try setting your default flight to default C-172, for example, just sitting on the runway idling.

OR, you can get into your FSX.cfg file and make it change to the default, default flight, if you see what I mean. Just open it with a text editor, NOT a word processor. They add symbols and characters that make a file useless to the sim. Search through for the heading [uSERINTERFACE], and under it the line SITUATION=. Delete any and everything after the "=" sign, save it, and when you fire up the sim it will select the original default flight that the sim comes with. This will ensure all the controls are neutral, and the switchology is correct, including having the AP off.

 

Of course, if you already use this default flight, the hang-glider over Friday Harbour, then ignore all this :D :p

Pat☺

[REDDAIR]

I read this thread and then had another rudder incident this week with takeoff in the A-320. The rudder was full left. My problem is a known one with the Extreme 3D Pro Stick. It has been reported and shown on You-Tube, etc.. and you have to jiggle (Exercise) the stick to lessen the problem. Sometimes it goes away itself.

 

I compare this to the automobile world. How many of us (In the US anyway) have seen hot rodders rev up a large auto engine and see the vehicle heave up on one side? Obviously the dude driving the vehicle has one bad engine mount (Or He modified it for reason of show). Kind of the same principle discussed here. What makes it different is, if you rev the auto engine up slowly, you will not see or feel anything or it is slight. So goes the idea if you throttle up an aircraft suddenly, the torque effect is more pronounced on takeoff and the aircraft will begin turning before you manage several yards?

[PhantomTweak]

and you have to jiggle (Exercise) the stick to lessen the problem.

Another vote for the famous "rudder waggle" :D

Just imagine a duck. You've seen them waggle their tails. Same thing. Waggle that tushie! :D

Pat☺

[BobSeaman]

My problem is a known one with the Extreme 3D Pro Stick. It has been reported and shown on You-Tube, etc.. and you have to jiggle (Exercise) the stick to lessen the problem. Sometimes it goes away itself.

 

One thing I noticed about the Extreme 3D Pro, sometimes you need to make sure it was assembled correctly (this is especially true with the rudder position sensor).

My 3D Pro had minor drift issues for years which I figured were more the fault of Win and FS. It finally got bad enough that I figured I'd try to fix it before heaving it in the trash and what I found was that the rudder sensor was not installed correctly. The little arm that was obviously meant to fit in the handle's channel was instead stuck between one channel and the hand grip case and the position sensor itself was not fully pushed into place on the main support rod. Once I noodled out how the sensor was supposed to fit, it was an easy matter to re-assemble it and its worked great since then.

 

You might want to check into how to take the hand grip apart and how to re-assemble it. :cool:

 

There's a trick to re-assembly*, but from what I can see the sensor itself doesn't wear out.

 

 

*- Taking the 3D Pro apart is a little tricky. You need to push down slightly on the hand grip after you remove all the screws (and be sure you removed ALL the screws!) to get the hand grip sides apart.

 

On re-assembly, it helps to tape the number 2 (thumb) button to the outside of the hand grip. Just use regular scotch tape across the handle outside and the top of the button then remove the tape once you're finished. :pilot:

The whole grip should also be pushed down towards the base slightly during re-assemlby. When you get it right and properly aligned, it literally falls back together. :D