February 12

Landing RC Model Airplanes

Those of you who have followed my website programme at www.rookiercflyer.com model landing approachwill have learned that an aeroplane has four forces acting on it: Lift, Drag, Gravity and Weight.

A model plane, just as a full size aircraft, in straight and level flight has all of these forces in balance. Thrust is equal to drag and lift is equal to weight. Opening and closing the throttle upsets this balance and causes the model to either climb due to increased speed or to descend when the speed is reduced.

Both of these changes are brought about by use of the throttle alone. This is the way climb and descent is achieved in a full size plane. The application of up elevator has the effect of increasing both lift and drag which overall slows the plane down.

Using both throttle and elevator together is an important aspect of the practical application required when landing rc model airplanes.

Dead Stick Landing

 Imagine the scenario where your model is on final approach and short of the landing strip the engine dies. Many pilots will immediately apply Up Elevator to try and stretch the glide. Unfortunately the opposite will happen and the model will fall short of the landing strip.

From my previous post outlining the use of Throttle and the following post about use of Elevator, you will know that by increasing the Angle of Attack (AoA), not only will you increase lift but you will also increase drag. This causes the model to slow down‎, sink faster and as a result arrive short of the intended landing point.

The other scenario is that the engine dies just over the landing threshold when the plane is too high to land but does not have enough height to go round again. The pilot’s instinct may be to apply Down Elevator to effect a quick landing. The outcome of this is for the model to speed up and as elevator is released, the model zooms upward and carries on off the end of the runway! (Verification that Speed is controlled with Elevator).

Correct Action

In situation one above the best option is to let the model settle into its own preferred glide path. It may land a bit short but it will be considerably closer to the threshold than if up elevator had been applied. It may even by helpful, if you have enough height, to apply the slightest amount of Down Elevator to increase the speed. The height lost will be regained when the elevator is released.

In the second case it may pay to apply a little up elevator to increase AoA and slow the model down with the extra drag this creates. This should result in the model sinking to earth quicker. Unfortunately too much elevator could cause the model to stall which at low altitude could result in partial or complete re-kitting of the model so care needs to be taken with this elevator input.

The safest way to reduce the landing distance would be to make a series of ‘S’ turns. each turn will increase drag and, at the same time, make the approach path longer.

Landing RC Model Airplanes Under Power

Landing Circuit

The diagram above shows a typical landing approach circuit. Prior to commencing this circuit most experienced pilots will overfly the runway before making a turn into the crosswind leg downwind of the landing area.

Unfortunately, when the wind is blowing in the opposite direction many flyers who have not been taught correctly will find it difficult to make the final approach to the landing area from a right hand turn. Their recourse is to fly an approach that takes them to the right behind the strip and turn left handed into the landing phase.

If you are learning to fly for goodness sake don’t get into this bad habit. A good pilot should be capable of approaching the landing from either the left or right. A right handed approach is just the opposite of that shown in the diagram and carries no greater risk so there is no reason to fear it.

Let us take the circuit above one stage at a time.

Having decided to make a landing approach the first action is to bring the model into position at the start of the crosswind leg, downwind of the landing strip. A suitable altitude for this would be around 100 to 150ft ( 30 to 45M).

A learner will usually have his model trimmed so that straight and level flight is maintained at around 60-65% throttle. this should be maintained until the plane has negotiated the next turn into the final downwind leg and is approximately level with the pilot.

At this point reduce the throttle to about 45 – 50% so that speed will start to bleed off and the plane will commence a descent towards the final crosswind leg. As the model negotiates the penultimate turn and settles into the crosswind leg it should have descended to around 45ft (15M) heading towards the final turn to the landing approach.

Once this final turn has been made, reduce the throttle to about 20% setting and line your model up with the landing strip centre line. If you find the model is sinking too quickly, increase the throttle slightly to create more lift and extend the approach.

Just before you cross the runway threshold reduce the throttle to idle. As the model drops toward the landing strip very gentle elevator is required to raise the nose a little and commence a ‘flare out’ at about 3 to 4ft (1M) above the strip. The model should settle gently on the ground without bouncing back into the air.

If there is any evidence of a crosswind you will need to apply a little rudder in the direction of this wind to keep the model’s nose pointing down the centre line of the runway.

Any tendency for the wings to drop one way or another should be controlled using ailerons. Don’t forget that as the model is approaching you, your aileron transmitter stick will need to be moved toward the dropped wing to correct the horizontal alignment.

I have found that most learners benefit from making numerous approaches without actually landing to perfect their approach pattern. The old adage ‘practice makes perfect’ comes into its own in this instance. Commence these sessions by practicing everything above without closing the throttle completely to idle. . Open the throttle again and gain height, overshooting the strip, until you can make another turn into a crosswind leg.

Repeat the routine until the control inputs become second nature to you. This is the time to practice descending to the idle position at which point, open up the throttle again and complete the overshoots from a lower altitude.

Eventually, you will be ready to go to idle and ‘flare out’ into a neat landing.

Aborted Approaches

An ‘aborted’ or ‘missed approach’ is when, having set yourself up for a landing, everything seems to be progressing well but suddenly, at the last minute, you lose your nerve or something goes wrong, and so you open up the motor to full power to climb out so that you can make a new attempt.

Both veteran and display rc pilots still need to do them now and again so there’s absolutely no shame in performing aborted approaches.  Five aborted approaches are preferable to  rushed panic landings so that you eventually land your airplane safely in one piece. rather than in several pieces! When flying an electric powered rc plane don’t lose track of the time you have been flying and your battery pack voltage! Always plan your flying time to allow a margin for extra go-rounds if required.

Landing your rc airplane is the hardest part of radio control flying, and the part that needs the most practice when you’re learning.  Persevere and learn to land well,. Never accept a bad landing without trying to improve on it the next time. Watch those competent pilots at your field who land rc model airplanes time and time again without so much as a bounce.

You can do it too!

In Conclusion

Once again, I hope you have learned something from this post that will encourage you to continue your progress in rc model airplane flight. Learning to do things right is the most rewarding aspect of our hobby and will help your enjoyment in the long term.

I hope you will aspire to achieve the standards of flying demonstrated by the pilots in this video:-

RC Plane Only Best Landings Compilation 

Don’t forget to follow my website tutorials if you are new to the hobby: www.rookiercflyer.com, and discover everything you need to know about getting started.

Colin

 

 

 

 

 

 

 



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Posted February 12, 2016 by Colin Bedson in category "Modelling Skills

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