twotter side slip or crab technique...need advices!

[GroovyMotion]

I tried many times to make the twotter to fall pretty quickly and I always failed! I tried in the Skymaster as well, have no idea if the real aircraft is capable of doing so. My issue is that when I bank and use the counter-rudder there is too much bank, I don't know if it's doable with a joystick?!

I would really like to master this technique instead of "diving" and overstressing the airframe!

[paddler]

First let me state that I have no real fying experience so what I am about to recommend may be impossible in the real plane.

 

I have seen one video of a twin otter from a skydiving school that uses an unauthorised technique to get back to the ground at the same time as the skydivers do. I beleive the technique is to apply flaps, reverse engines and then spiral the plane in a deep dive. This appears to keep airspeed below critcal levels yet achieve a steep descent. I have used this technique on steep straight approaches and in the sim at least it works.

 

I expect that real pilots here will can tell us if this would in fact be successful in the real world, or even better identify for us a real technique. I look forward to finding out.

[GroovyMotion]

First let me state that I have no real fying experience so what I am about to recommend may be impossible in the real plane.

 

I have seen one video of a twin otter from a skydiving school that uses an unauthorised technique to get back to the ground at the same time as the skydivers do. I beleive the technique is to apply flaps, reverse engines and then spiral the plane in a deep dive. This appears to keep airspeed below critcal levels yet achieve a steep descent. I have used this technique on steep straight approaches and in the sim at least it works.

 

I expect that real pilots here will can tell us if this would in fact be successful in the real world, or even better identify for us a real technique. I look forward to finding out.

I don't know if it's the same video I saw, maybe I didn't pay attention to the actual manoever. I will try it to see if it works, thanks

[Maurice_King]

This WILL work for ALL aircraft in the real world BUT if you have Auto rudder turned on in FSX then it will not !!

 

When you want to side slip an Otter say to the left, you should throtte back to reduce your speed to about the normal approach speed with the nose pitched down slightly apply rudder right rudder to yaw to the right, now as the wing attempts to roll right you counter this at the same time as the rudder is applied to holdthe wing down at least 5 to 10 degrees to the left and gradually apply more rudder until you reach a stable point at which you aiming point have moved left some 10 or more degrees this exposes the left side of the aircraft to the Airflow and if you apply a little power at the same time you will now continue on your flight path but at a greatly accelerated decent rate.

Remember the primary effect of Rudder input is Yawing the Aircraft the secondary effect of rudder input is Roll in the direction of the rudder input.
Side slipping requires you to counteract this Roll with Aileron input holding the lead wind down below the horizontal. 

 

As for decending in an Otter ultra fast Full Fine minimum thrust ,  and essentially spin the aircraft 

I SERIOUSLY doubt ANY Otter Pilot would apply reverse thrust in the Air, Full fine with the prop spinning at nominal PM is more effective and far less dangerous to the Aircraft and the Prop drive gearbox. 

[Brito]

Well done, Maurice_King. Well explained and technically compliant with the manual. I would add, if I may, and answering the asker colleague, a joystick that allows normally fly the FS, it allows sufficient control for this maneuver, also although the use of a pair of pedals would be ideal.

Cheers,

Sinesio

[paddler]

Maurice,

 

Thanks for the explanation. When you move into Beta range does this also give you some fine pitch? 

[GroovyMotion]

This WILL work for ALL aircraft in the real world BUT if you have Auto rudder turned on in FSX then it will not !!

 

When you want to side slip an Otter say to the left, you should throtte back to reduce your speed to about the normal approach speed with the nose pitched down slightly apply rudder right rudder to yaw to the right, now as the wing attempts to roll right you counter this at the same time as the rudder is applied to holdthe wing down at least 5 to 10 degrees to the left and gradually apply more rudder until you reach a stable point at which you aiming point have moved left some 10 or more degrees this exposes the left side of the aircraft to the Airflow and if you apply a little power at the same time you will now continue on your flight path but at a greatly accelerated decent rate.

Remember the primary effect of Rudder input is Yawing the Aircraft the secondary effect of rudder input is Roll in the direction of the rudder input.

Side slipping requires you to counteract this Roll with Aileron input holding the lead wind down below the horizontal. 

 

As for decending in an Otter ultra fast Full Fine minimum thrust ,  and essentially spin the aircraft 

I SERIOUSLY doubt ANY Otter Pilot would apply reverse thrust in the Air, Full fine with the prop spinning at nominal PM is more effective and far less dangerous to the Aircraft and the Prop drive gearbox. 

Thanks that's a good explanation! No auto-rudder is OFF but with my Logitech ailerons are left/right and rudder is twist left/right which makes it a little harder. I will practice some more

[Maurice_King]

Used to use a Joystick with rotation for rudder and it would allow side slipping rather well. Remember the whole point of sideslipping is to expose the side of the Aircraft to the rearward moving airflow greatly increasing the drag and thus the rate of decent. 

 

@paddler , Not sure what you mean here as the pitch for an Otter is about -5 Deg to + 60 Deg I believe but I am not sure of the exact angles,  remember that applying reverse thrust on the ground roll is in effect like deploying 2 drogue chutes the size of the Props and greatly increases the ability to stop on short fields.

[vanderlay]

Maurice,

 

Thanks for the explanation. When you move into Beta range does this also give you some fine pitch? 

 

 

G'day Mr Paddler,

 

There may be a little confusion in this post about some differences in operation of piston engines and turboprop engines.

 

People certainly do sideslip aircraft to increase the rate of descent for a given airspeed (piston or gas turbine).

 

For those that don't know, Beta range is a feature only used in turboprops and does indeed give you fine pitch. In a piston engined aeroplane, we obviously taxi with a fully fine pitch and we control the speed of our taxi by increasing or decreasing the throttle setting as required.

 

Beta range is used in a turboprop mainly because of the lag time that exists when a gas turbine engine spools up or down. It makes it much harder to judge when you want to increase or decrease the throttle. Therefore, when you taxi a turboprop, you taxi in "beta mode" which controls pitch rather than RPM and so the engine in spinning at a given RPM and the propeller is changing pitch to provide thrust, nil thrust or even negative pitch angles.

 

Hope this helps.

[paddler]

G'day Mr Paddler,

 

There may be a little confusion in this post about some differences in operation of piston engines and turboprop engines.

 

People certainly do sideslip aircraft to increase the rate of descent for a given airspeed (piston or gas turbine).

 

For those that don't know, Beta range is a feature only used in turboprops and does indeed give you fine pitch. In a piston engined aeroplane, we obviously taxi with a fully fine pitch and we control the speed of our taxi by increasing or decreasing the throttle setting as required.

 

Beta range is used in a turboprop mainly because of the lag time that exists when a gas turbine engine spools up or down. It makes it much harder to judge when you want to increase or decrease the throttle. Therefore, when you taxi a turboprop, you taxi in "beta mode" which controls pitch rather than RPM and so the engine in spinning at a given RPM and the propeller is changing pitch to provide thrust, nil thrust or even negative pitch angles.

 

Hope this helps.

 

Thanks for this. What prompted me to ask about the Beta Mode was that perhaps in the video they were only using Beta Mode instead of full reverse thrust in the rapid descent.

[Maurice_King]

How'd get on "groovy" 

[GroovyMotion]

How'd get on "groovy" 

Sorry, I didn't try it out yet, too busy having fun in my mil planes.

I will definitely try it out soon though!