The effects of torque...

[PRB]

Ever since I purchased a set of rudder pedals for FS and turned the realism settings to “full right”, I’ve noticed something interesting about the “torque beasties” that I can’t explain. It happens with just about every tail dragger fighter, both in FS9 and FSX, so I’m speculating the effect is real.
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With the US fighters, you need to apply almost full right rudder during the take off roll, but, when the plane first begins to move, she tends to veer to the right, requiring left rudder input. This phase of the take off roll only lasts a second or two, before the well-known massive right rudder input is required.
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What is going on here? Is this effect seen in the real ones?”

[mike_cyul]

I can only speak for the Messerschmitt Bf-109 (later models), but I have read that in order to help counter the torque and allow full throttle faster, mechanics would have different air pressures put in the tires, which would result in the aircraft moving right for a second when first getting underway, and then back to the legendary 109 torque pull to the left after that - albeit a little less due to rolling resistance.

That said, somehow I don't think that was deliberately done in the sim by Microsoft for that reason - but it does benefit any 109s! :)

Mike

[fliger747]

My experience as a fairly high time taildragger pilot and developer is that this one factor that MS got wrong in the sim engine.

Mike, Like the WIP....

Cheers: T.

[warchild]

I have to agree with Fliger. This is a problem that plagues every tail dragger in FS, and there's even worse. Royal Airforce props turn opposite to american props so,they should be pulling to the right all the way down the runway, but they dont.. It's ( in my opinion ) a decided shortcoming of FS..

[SolarEagle]

Never flown a real plane, but front wheel drive cars with upward of 350ft-lb and an automatic tranny can have some pretty wicked torque steer. Gotta hold the wheel tight and steer into it a bit.

[PRB]

Mike, interesting about the German fighters. I didn't know that!

Fliger-Tom, also interesting. Given it's an FS "anomoly", I wonder what's going on in the sim to produce this effect.

Pam, I have a couple RAF fighters in my hangar that require the expected "opposite" rudder input from the US ships during take off, so this, at least, is not an FS flaw...

[warchild]

Pam, I have a couple RAF fighters in my hangar that require the expected "opposite" rudder input from the US ships during take off, so this, at least, is not an FS flaw...

WHOA! cool! thanks Paul.. I appreciate that correction.. My bad.

[Dimus]

I wonder if tailwheel lock has something to do with this. If it is not locked then the position might not be centered when you start rolling. It might be causing the craft to turn right instead of the expected left. Then once you start rolling faster it centers and the torque effect takes over. I will do some checks with the Real Air Spit and come back to you.

[gajit]

Remember "Careless Torque costs lives"

[fliger747]

The t-draggers will exhibit this charcteristic without regard to the t-wheel lock, though it tends to dampen the effect. Indeed a properly done Brit fighter turning the 'wrong" way will indeed pull the "wrong" way. One needs to remember to use "wrong way" rudder trim.....

To clarify a bit, what we are actually discussing here is P-factor. The spiraling propwash circles back and hits the rudder with a degree of side vector. There may be some assumption in the way that FS calculates this effect that does not fully match the situation . Torque is an opposite and equal reaction effect to the rotation of the prop and it's rotational resistance to the atmosphere. Essentially the same foce that helicopters us a tail rotor to counteract. A well done prop fighter FM with a good power/weight ratio will exhibit this at low speed. An uncontrollable departure in a torque roll can result with low speed sudden application of full power. Corsairs and Mustangs were famous for this.

Cheers: t.

[mike_cyul]

Mike, Like the WIP....

Cheers: T.


Thanks, Tom. :engel016:


Mike

[fliger747]

FWD cars.... The torque of the engine/drive train causes a lateral deflection of the suspension, which changes the steering geometry and requires a steering correction. Stiffer suspension, better dampening and anti roll bars help here.

One side effect of torque in aircraft is any aileron correction to "lift the wing" on takeoff will generally require a bit more rudder to compensate for the adverse yaw effect.

Cheers: t.

[Major_Spittle]

FWD cars.... The torque of the engine/drive train causes a lateral deflection of the suspension, which changes the steering geometry and requires a steering correction. Stiffer suspension, better dampening and anti roll bars help here.

One side effect of torque in aircraft is any aileron correction to "lift the wing" on takeoff will generally require a bit more rudder to compensate for the adverse yaw effect.

Cheers: t.

Strangely it almost feels like all the power went to just one of the front wheels. :kilroy:

[robrealair]

Hi Guys,

There is a certain logic to this phenomenon in FS and FSX. P-factor tends to have a yaw effect whereas torque tends to revolve the aircraft around its own engine, and on the ground this means (for conventional turning props) that extreme torque will dip the left wing, or if you like place more weight on the left main undercarriage than the right.

In FS, putting weight on one side, or slightly banking the aircraft on the ground, produces a moment that turns the aircraft to the right. There is a rational reason for this: Tipping the weight so it rests on the outside of a tyre will create a swing to the opposite direction.

However, once forward motion is established, the p-factor effect will overcome the torque effect. At the "break" point between the two forces, the p-factor tendency to swing to the left is equal to the weight-related swing to the right.

Once around 15-20 knots forward speed is established the p-factor wins and thereafter the aircraft will begin to swing left.

When not influenced by ground friction or weight of wheels on the tarmac, torque carries on doing what it did on the ground, creating a roll moment to the left, which now works in tandem with p-factor also turning the aircraft to the left. Thus in the air torque and p-factor work together to create a left roll and yaw moment.

Best Wishes,

Rob Young - RealAir Simulations

[fliger747]

Having flown a lot of real taildraggers, some with some fairly good power to weight ratios, I have never had one want to go the other way first. Actually P-factor is mostly a product of the swirling slipstream and is pretty effective at low speed. However at low speed the tailwheel has good weight and resistance charcteristics. There IS (Clintonian emphisas) a gyroscopic effect as the tail is raised, one wants to do this with some awareness.

It is true some of the tippy planes, ie. ones with a narrow track, such as the Bf109 and Spitz this migh have some effect. However I have noticed this adverse swing in such stable behemoths as Gnoppy Kohler's B-29 series. Perhaps it has something to do with the way the sim integrates rudder trim into the ground handling. However it is still noticable with castoring tailwheels and also nose draggers! One reason the swing occurs with a lean is that the CG is displaced to the side. My estimation is that the CG for a nose dragger being in front of mains, the tendency would be to turn the other way.

Still thinking it is a (minor) hole in the sim as I have not (yet) experienced this in a real aircraft or (yet) seen it described in any aircraft notes.

Cheers: T.

[fliger747]

Thinking about this a bit, it may be a reaction to prop inertia, causing a precession. One could test this by measuring the effect with different Prop MOI values.

Cheers T

[beana51]

Once read ,The only purpose of the rudder is to cover up the mistakes of the designers"

Chapter 8,"That Thing Called Torque" in what has to be the bible, "Stick and Rudder" about the Art of Flying,by "Wolfgang Langewiesch".Here "TORQUE" is explaind in great detail.I'm sure most know ,or have this book.if not,highly recommended!..Worth it to get it straight and correct! <label for="rb_iconid_3">http://www.sim-outhouse.com/sohforums/images/icons/icon3.png</label>

[jetstreamsky]

I'm sure it's not so much Royal Air Force props turning opposite to US props as such, I doubt P-51 Mustangs modified the Merlins to reverse the direction; although when the Spitfires moved on to Griffon versions the direction was opposite to the Merlin which could catch out the unwary.

The most annoying thing in FSX is when the P-factor is left in when flying a jet.

[fliger747]

Yep, Stick and rudder is a good book, I learned in when I got my first liscense cirica 1973.

Amazingly Langwische flew something like a thousand different Corsairs during WWII, as a Vought production test pilot.

The Packard Merlin, and the Rolls version both turned clockwise as seen from the cockpit though I have some dim and not precise memory of a "Handed" Version. Not sure of the ins and outs of having an opposite handed engine, except it might give one an advantage if you were to controll a turning fight in the direction you had an advantage.

Cheers: T

[fliger747]

You shouldn't get any P-factor in FSX jets if they are setup correctly. The controls in the .cfg and .air files are there to eliminate it completely.

Cheers: t

[SkippyBing]

I have some dim and not precise memory of a "Handed" Version

I think handed versions were mainly used for twin engine installations such as the de Havilland Hornet where it made the single engine characteristics more benign.

[fliger747]

Exactly so! Not the favorite of the parts guys!

T