Torque reaction

[Rich Griff]

Please remind me...

 

Torque reaction due to engine and propellor torque ( an anticlockwise prop rotation looking at the engines front ) with the prop rotating in a clockwise direction as viewed from the engines rear, results in a tendancy for the aeroplane to want to rotate to the left ?

 

To port ?

 

Yes I know of engine offset to counteract the torque reaction etc...

 

So, which is the safest direction to turn the aeroplane after take off and sufficient hieght gained please ?

 

Again, yes I know, a pilot should be capable of turning his aeroplane in either direction safely, he may have to at some point for collision avoidance.

Edited February 7, 2022 by Rich Griff

[Andy Stephenson]

Torque reaction has very little effect on moving plane, vis the torque-roll in a prop hang only starts to take effect once the plane has stopped climbing.

The main reason for building in right thrust is because of the prop vortex swirling around the fuselage which is pushing asymmetrically on the fin.

Providing the plane is "flying" it won't make much difference which way you turn.

[J D 8]

What you say is correct, however for most models this force is not that much and most models will hardly notice the effect. The problem comes with high power types, more so if the stick is slapped open and certain aircraft like WW1 types with narrow UC and short fuselage causing problems on take off. Once flying they are fine and like others it will not matter which way you turn.

[Martin Harris - Moderator]

3 hours ago, Andy Stephenson said:

Torque reaction has very little effect on moving plane,

Tell that to a Sopwith Camel pilot! 

 

But yes, our models have relatively small torque reaction effects - I wonder if this relates to Reynolds number considerations or if it's mainly the lower rotational mass of the engine and propeller?  Although our power to weight ratios are usually greater than scale, I've never experienced - or seen - a model torque roll from the careless application of power at low airspeed which has caused the loss of many WW2 fighters.

[Don Fry]

We don’t use rotary engines. Huge flywheels, gyroscopic effects. 
I assume you ride big bikes. If you want the thing to go right, you push with the right hand, and the gyroscope that is the front wheel, twists the machine over to the right, and round you go.

I used to have a Panic biplane (broke it again), stupid overpower. So open the motor, steady open, off the ground in a meter, and off we go, vertical, still opening it out steadily. Heading was 40 degrees out from direction of travel.

But to answer Rich Griffs question, once it’s going, and it up to speed, so the prop is in line with the direction of travel, the prop had not much gyroscopic effect.

It always turns easier (readier) to port, but that’s a trimming issue.

[Martin Harris - Moderator]

8 minutes ago, Don Fry said:

We don’t use rotary engines. Huge flywheels, gyroscopic effects.

True - but neither do Mustangs nor Bearcats.

[Don Fry]

But the Bearcat does a couple of thousand horse, 3 tons? It has to have some torque.

open the thing up with the prop not going in the same direction, you will have a problem. 
But I don’t think Bearcat pilots had 10 or 15 hours in a cockpit. 

 

[Chris Walby]

Just chipping in as it might be relevant.

 

1/ Eric "Winkle" Brown in his recount of preparation for landing a DH Mosquito on an aircraft carrier had one of the "boffins" with him at altitude in landing configuration when he powered off one engine (simulated loss of engine on landing approach) at which point the mossie abruptly rolled onto its back. His point was that if this occurred on a carrier approach then it would be unrecoverable.

2/ I heard somewhere that due to a high number of aborted P47 landings and fatalities, new pilots to the type were instructed to fly at high altitude, set the aircraft into it landing approach (gear down, flaps landing position and landing airspeed) then slam the throttle open. At which point the aircraft  would roll inverted, hence the important lesson learnt that the P47 would easily regain airspeed without the use of full throttle.

 

From personal experience hand launching fun fighter type models with high KV motors (on near or full throttle) seems to produce a lot of roll before the model gains airspeed, this is all a bit exciting as then normally only need very small control throws in flight. 

 

The Focke Stick (1800KV motors) with both motors rotating in the same direction will roll to near inverted before the ailerons become effective, but with counterrotating props just wants to head skyward when the helper can hold on to it no longer!

 

IMO, its not just an issue with rotating mass...its how fast you accelerate the mass that gives the torque reaction (as the Focke Stick only accelerates the motor can and prop up to approx. 25,000 rpm

 

In answer to the OP, in extreme cases roll left and gentle climb out, for everything else apart from the Focke Stick be gentle on the throttle, use a rudder and turn into wind  with a gentle climb out especially if it does not have enough power to pull the skin off a rice pudding.  

 

[J D 8]

 Tell that to a Sopwith Camel pilot.

The Camel was very much subjected to the force of " gyroscopic precession  " due to the mass of its rotary engine spinning around. Should you want to feel this force take a 9 inch angle grinder with heavy grinding disc, hold it out in front and turn it on, then swivel your whole body 90 degrees. CAREFUL and hold tight it will try and twist itself out of your hands.

[David perry 1]

Other answers notwithstanding, it depends on your model.  I have an eglider with a large folding prop and the roll against torque is a very leisurely affair but the roll with torque is most snappy!  So it depends how fast you want to turn.  I suspect that there is no "safer" way to turn unless youre perilously close to the stall.  To which Id ask "why are you?"

[Martin Harris - Moderator]

I did say that models (in general, I'd forgotten about Chris W's ridiculously powered Frankenstein jobby) were relatively unaffected by torque reaction - the observation was on the statement that "planes" aren't affected much by torque once at flying speed - but gyroscopic precession exerts torque force on an airframe...although if we're talking about roll reaction to engine torque (as per the OP's question) then we can ignore gyroscopic effects anyway.  A Camel reacts to gyroscopic precession when turning right by dropping its nose and the opposite in a left turn. It appears well known that the roll rate was very much faster when rolling with torque than against it - to the extent that it was often considered better to do a 270 degree right turn to change direction to the left if you were in a hurry!

[Doug Moss]

In answer to the original question, never mind torque, turn into the wind.

[Brian Cooper]

Most sports-type models can happily bumble around the sky seemingly oblivious to the effects of the torque reaction from the propeller.  

Takeoff:  As with all aeroplanes, resist the temptation to lift off too early. . . . and learn how to use a rudder. 

 

It becomes more noticeable when trimming - or fine tuning an airframe - on a model which requires a higher degree of precision; notably pattern ships, etc., with a (much) better than 1:1 power-to-weight ratio. 

 

Pull vertical and observe if the model tracks in a dead straight line.

Without a touch of right thrust, most will veer off to the left. 

 

[Allan Bennett]

Hand-launched models, especially light foamies, often seem to suffer from torque roll simply because the natural tendency is to bang the throttle wide open when releasing it.  
 

As has been mentioned, most models when up to flying speed will not be affected so much, which is why I much prefer sedate ROG take-offs with the throttle opened slowly and the model allowed to fly off the ground, rather than being yanked off too early by application of up elevator.

[Martin Harris - Moderator]

2 hours ago, Doug Moss said:

In answer to the original question, never mind torque, turn into the wind.

Why would that be?  Won’t it depend on the circuit direction?

[J D 8]

     One property of electric motors is their ability to produce their full amount of torque from just about the moment they start where as with an IC max torque will be at a certain speed in the rev range.  Not slapping the power on or opening the throttle quick is a good habit to get into whatever type you are flying.

[Rich Griff]

All important stuff to be aware of in a "collision avoidance" situation, low, slow, change in conditions of the aeroplane to avoid something...

 

Take off and landing is into wind, unless on take off you are fighting the undercarriage, swing or other deviation from "into wind"...

 

Landing approach, lowering height and speed, "avoidance" called for, Increase in power, increase in hieght ( power controls hieght ? ) turn away to avoid....

 

Low speed, power applied and turn to port, bad things "adding up" and it rolls in ?

 

Does gyroscopic effect add to these " bad things" or subtract from these bad things ?

 

I like to hold a good airspeed on landing rather than have the model stall 6 inches from touch down.

 

I used to fly from a smooth large beach, so am somewhat spoilt I suppose.  As soon as touch down is made I would close the throttle completely and left the model roll to a stop.

 

Eventually I learned to hold a little on throttle via trim and taxy back to "pits" area for model check over, refuel, preflight check and take off again. I used to enjoy 5 to 6 full tank flights if a good 12 mins, fuel reserve for landing/go round)taxy etc.. rather than dead stick.

 

I had no option but to turn to port else I would be flying into "prohibited zoom ", safer zone being over the water.

 

When wind from South, turn to starboard, over the sea.

 

Off shore wind was a NO FLY day from the beach.

[J D 8]

  Gyroscopic precession is not something to bother a model unless powered by a scale rotary engine.

[Andy Stephenson]

Gyroscopic precession can cause some undesirable effects when pulling a tight loop or bunt. With a 2 bladed prop because the mass is not distributed equally around the prop circle, the effects of precession not only cause a force at right-angles to the axis of the manoeuvre but also come in pulses at twice the rotational speed of the prop. This was the reason for fatigue breaks in crankshafts on some large 3d models and the complete destruction of the flimsy ply motor mount on an electric model I witnessed.

[Geoff S]

I have seen an electrically powered model being test flown by an experienced, though perhaps out of practice, pilot suffer greatly by torque reaction on take off.  The effect was so marked, the model ground looped, and appeared to have reversed ailerons (which it didn't).  The model was very well, or even over, powered which took the test pilot (it wasn't his model) somewhat by surprise.  It just goes to show that the best method is to open the throttle very gently until the model's characteristics are known.

[Martin Harris - Moderator]

I’d go a little further, Geoff:

 

It just goes to show that the best method is to open the throttle very gently. 

[Simon Chaddock]

Try whacking open the throttle, particularly electric, when close to the stall. You will definitely see the effect of motor torque reaction but only do it when 3 mistake high! ? 

Don't forget most, if not all, RC planes, and foamies in particular, have a higher power to weight ratio than full size so the effect of motor torque can be rather more significant.

 

As Martin says be careful how and when you open the throttle, unless you have a counter rotating twin or better still a counter rotating inline twin.?  

[Doug Moss]

21 hours ago, Martin Harris - Moderator said:

Why would that be?  Won’t it depend on the circuit direction?

Rich asked which is the safest direction to turn, suggesting an emergency. If you're marginal on power or airspeed, then convert your momentum into airspeed by turning gently into wind.

[Rich Griff]

Is the collision avoidance related to "people etc. " on the landing strip ?

 

If it is then landing would be into wind.

 

Due to the nature of the flying site I have had to land ( and take off ) cross wind from time to time.

 

But yes, landing approach, low and slow, "collision avoidance" called, real or other wise, which is the safest direction to turn, assuming you had a choice ?

[EarlyBird]

22 minutes ago, Rich Griff said:

which is the safest direction to turn,

Away from people and away from the flight line if possible.