Beta 6 is out

[Humpty 751]

Maybe tyre friction is too low for that (wrong ?)  RPM ? you know bald tyres

[bonchie 2,305]

When I tried earlier versions of AirfoilLabs 172 that worked in XP11B3 it was taxing about right. I did had problem with right pull on take off with LE DC-3 but the issue were resolved.

I didn't try stock planes in PB6. However, I noticed  add-on Cherokee 140 had an excessive left pull during taxi as well even thought I tried to keep directional control with my CH rudder. I also felt excessive thrust in beta 5. Right now I'm fooling around with ixeg 737. It seems taxi just fine

 

Jets work fine. No issues. That's another reason to probably assume it's a prop modelling issue.

 

 

P.S.By the way I used to own 182 F, loved it.

 

It's slow compared to the Mooney's I've flown, but it's great to be able to load 4 people and bags up and basically have no worries. The long range tanks are great as well.

[Murmur 3,944]

Maybe I can answer that or at least give you another variable.

 

In my first video, at the end of the first run I pull the throttle and the plane immediately stops pulling left and tracks straight in it's roll. Only when the RPM settles back at idle does the left turning start again.

 

So to me, I'd think that says it's prop related.

 

I see your reasoning, but when the propeller is slowing down, I assume the calculates propwash is about zero (roughly no torque on the prop, hence roughly no helical propwash, also according to the explanation given by Austin on the dev blog).

 

So that explains why the C172 tracks straight when the propeller is slowing down: no helical propwash so no yawing moment. But as soon as the engine goes to idle, it's applying some torque again (albeit small) and hence there's some helical propwash again, and hence left turn again.

 

Now, that does not exclude whether the culprit is too much force applied by vertical stabilizer (by the propwash), or too little tire friction, or both.

 

If we can demonstrate roughly equal amounts of excessive weathervaning in either direction -- left or right as in my example above by simply by changing the wind direction, then doesn't that rule out propwash effects? Anything related to the prop/engine should favor one direction only.

 

I'm almost sure that the weathervaning due to vertical stabilizer is excessive. The problem is if the tire friction is also too small.

[bonchie 2,305]

Maybe tyre friction is too low for that (wrong ?)  RPM ? you know bald tyres

 

Note that jets and twins do not have this issue, which again points to it being an issue with the single engine prop modelling interacting with the surfaces of the airplane. .

I see your reasoning, but when the propeller is slowing down, I assume the calculates propwash is about zero (roughly no torque on the prop, hence roughly no helical propwash, also according to the explanation given by Austin on the dev blog).

 

So that explains why the C172 tracks straight when the propeller is slowing down: no helical propwash so no yawing moment. But as soon as the engine goes to idle, it's applying some torque again (albeit small) and hence there's some helical propwash again, and hence left turn again.

 

Now, that does not exclude whether the culprit is too much force applied by vertical stabilizer (by the propwash), or too little tire friction, or both.

 

So can the propwash effect simply be tempered at lower RPMs to stop the issue? Prop wash shouldn't be much of a factor at taxi RPM settings.

[soaring_penguin 428]

Actually, could be the roll resistance is to little, and not compensating. Remember people are complaining about the plane living with to little throttle too.

[Humpty 751]

Hmm i don't know but would it be same with contra rotating props ? like I think the C90 ? Guess i will take a ride in the C90 and the 109.  Maybe 1st in XP10 and then later in XP11

[sd_flyer 6,047]

Jets work fine. No issues. That's another reason to probably assume it's a prop modelling issue.

 

 

It's slow compared to the Mooney's I've flown, but it's great to be able to load 4 people and bags up and basically have no worries. The long range tanks are great as well.

 It's off topic, but Mooney doesn't fit in my choice of comfort definition. I'd rather go with Bonanza, but it can't beat 182 in short field performance. So 182 is perfect compromise comfort/room/speed 

[Paraffin 2,197]

Note that jets and twins do not have this issue, which again points to it being an issue with the single engine prop modelling interacting with the surfaces of the airplane. .

 

Jets and twins are also heavier than a C172, with more weight on the tires. I did notice in a test just now, that the default Cirrus jet doesn't weathervane like the default Cessna. But then it's almost twice as heavy, with less "sail" area to the rear for wind effects.

 

Somebody should take the default C172 and replace the stock engine with a small jet engine on the roof in PlaneMaker, so we can compare.  :smile:  If I knew enough about PlaneMaker I'd try it, but I don't.

[Jimm 437]

I just finished a short hop from KBUR to KPSP and this weathervaning effect that everyone speaks of, is acting rather odd on my end.  For this flight, I used real world weather (though I missed what the actual groundspeed of the wind was) .

 

I do experience the immediate push to the left at idle rpm and brakes off, and when I apply throttle, the aircraft then starts to move from left to right.  I get control of the tiller and try my best to keep her straight.  Once I drop the throttle to idle and apply a little brake, the aircraft starts to behave a little better.  In creasing the throttle through the taxi phase will give me varying results of a left or right pull so I just continue to counter the forces as best I can.  Once at the end of the runway, I'll apply brakes, throttle up to 50%, let off the brakes and the aircraft starts to behave a little better, but after full throttle is engaged, it's a stampeding bull out of the gate until I get lift.

 

Unfortunately, I've been getting used to the way this aircraft behaves now, but I'm not saying it's correct.  Who knows, maybe these counter forces we're experiencing just helps us become better pilots. lol

[bonchie 2,305]

Jets and twins are also heavier than a C172, with more weight on the tires. I did notice in a test just now, that the default Cirrus jet doesn't weathervane like the default Cessna. But then it's almost twice as heavy, with less "sail" area to the rear for wind effects.

 

Somebody should take the default C172 and replace the stock engine with a small jet engine on the roof in PlaneMaker, so we can compare.  :smile:  If I knew enough about PlaneMaker I'd try it, but I don't.

 

IF the tire friction is off on the lighter piston singles (I get the same issue with the V35 + Simcoders), then the prop-wash could be causing the push sideways while technically being correct simply because the plane isn't firmly attached the ground. Or, the prop wash itself could be too strong at lower RPM levels and causing it and weight has nothing to do with it.

 

Chicken or the egg issue. Someone might try experimenting with a bigger single engine prop plane. Like a Meridian or PC12 if someone has an addon for one.

[Paraffin 2,197]

Chicken or the egg issue. Someone might try experimenting with a bigger single engine prop plane. Like a Meridian or PC12 if someone has an addon for one.

 

I tried it just now with the Carenado PC-12. With a 5 kt. crosswind from the left, it turns to the left after brakes are released. With a 5 kt. crosswind from the right, it turns to the right after brakes are released.

[Humpty 751]

To me it looks like the tire friction and prop modeling issue. But as Murmur said the vertical stab also maybe playing a role. I guess a 172 would need much more than 15 kts to turn into the wind on the ground. 

[Murmur 3,944]

Can you try this  modified vertical stabilizer airfoil? You must put that inside the "airfoil" subfolder of the "Cessna 172SP" folder (NOT inside the "airfoil" folder in the main X-Plane folder).

 

https://drive.google.com/open?id=0B5fyJwRhjar5OHJJQVdESi1HeWs

 

With that, the left turning tendency during taxi and take off roll should be reduced. Also, I can takeoff, land and taxi with 25kts direct crosswind (although the tires screech a lot).

[bonchie 2,305]

Yeah, I'll try it tonight and see how it feels.

[hjsmuc 393]

Hey, that is making a BIG difference. Many thanks. Could you do this also for the Carenado 206 and PC12 and the Kodiak?