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Almost killed the president of our club today...

nhk750

Aviation Enthusiast
#1
I went to go fly my newly built Great Planes Taylorcraft today (the 5th flight) and I just wasn't feeling all that sharp this morning. So I fired up the T-Craft (electric), taxied out to the runway and went full throttle for takeoff from left to right (that is my weakest flight direction). I promptly lost control of the plane, it veered to the right towards the flight line and directly at a man in a wheelchair and our club president's head at full throttle! Somehow I kept my head, and as I was instructed flying real airplanes "always keep flying the airplane until it isn't flying anymore", and I managed to regain control and save the day and my balsa built airplane. I thought for a second that I was going to have a pile of sticks and two injured or dead guys on my hands... I guess the lesson learned is to evaluate my mental and physical state before getting on the sticks... But, no damage, lesson learned and will fly another day!
 

nhk750

Aviation Enthusiast
#8
I cant imagine drinking and flying, I can barely fly sober...LOL. Yes, Great Plane makes a Taylorcraft clipped wing balsa kit. If you look for my very detailed build thread you will see an electric conversion build. Sorry, no camera on the plane that time, but it would have been a good video for sure!
 
#9
Yikes, Scary. Glad no one was hurt.

Don't really know all the details so will just sort of speak generally here.
There are many best practices for takeoffs that can help prevent drama. Tail draggers in particular are a challenge because with the center of gravity behind the pivot point of the landing gear they are not completely directionally stable and prone to swerves that if not corrected early can lead to full ground loops.

As you said evaluating your own mental and physical state prior to any takeoff is a good idea. Some days we are just better than others. Illness, medications, stress, fatigue, emotional issues, hydration, blood oxygen levels etc etc are just a short list of things that can greatly impact our physical performance.

There are environmental and aircraft issues as well. Wind, temperature, lighting, aircraft maintenance issues can all also play into the degree of success for any given flight.

Procedurally one of the things you mentioned gives me some concern. You mentioned you "went full throttle" for takeoff. That lacks a little definition but I will say I see people at the field every day who use little discretion in their power application for takeoff. They simply slam the left stick home with little thought other than that is the quickest way to get away from the ground where they know they sometimes experience directional difficulties. I call this method the "poke and hope" It often leads to directional control issues. Even worse when the plane is clearly no longer doing the confused pilots bidding he will often add even more power if he doesn't already have full power in and now it becomes a race between gaining enough airspeed to get airborne and back in control before he either takes a trip through the weeds on the far side of the runway or hits the fence at one of the pilot stations. Often times this additional power and trying to get the airplane airborne before it has adequate speed for control leads to an airplane that was out of control on the ground becoming an airplane that is out of control in flight. If you learn one thing from full scale know this regarding takeoffs. When the aircraft is no longer fully under control the ONLY acceptable response is to close the throttle and reduce the kinetic energy that the aircraft is generating. This should make the task of getting directional control back easier especially if you get the tailwheel back on the ground and will minimize the damage to both aircraft and other things it might hit. Taxi back to the end of the runway, think about what went wrong and try again. A takeoff should have a smooth and controlled roll on of power. The maneuver must be continuously evaluated by the pilot throughout for problems that would dictate an abort. A takeoff can be made by slamming the throttle wide open and many pilots do it reasonably safely as long as they understand the physics involved. Doing this for pilots working on their skills will do little to develop them and can potentially lead to very bad habits.

Lets talk about some steps you can take that will help ensure the model remains under pilot control throughout a smooth takeoff and initial climb.

First we must recognize as I said earlier that tail draggers can be challenging beasts. They will swap ends, ground loop, if you let them. So how do we stay in control? By understanding the forces on the aircraft and the strengths and weaknesses of the controls we have to maintain control. Most TD's have a steerable tailwheel that can only function when it is on the ground. We can ensure this happens in the beginning of the takeoff roll by holding back pressure on the elevator as we smoothly bring up power. Those who do not do this see the tailwheel come of the ground early at a low airspeed before the rudder is aerodynamically effective. This allows the props left turning tendencies to have their way with the model and is the cause of many left turn ground loops especially with high powered models. Ensure the tailwheel stays in contact with the ground til you have a bit of forward speed.

The second major control we have for ground directional control is the rudder itself. Rudders have a couple problems though. At low airspeeds as in the beginning of the takeoff and end of the landing roll the rudder lacks effectiveness. This is one of the reasons we rely on the tailwheel steering here. On takeoff the prop blast activates the rudder so the effect is somewhat minimized. This effect varies from airplane to airplane. The second problem with rudders for ground control is that when the tailwheel is on the ground with the nose in the air the fuselage may blanket airflow across the rudder. We generally want to minimize the time we spend in transition from tail on the ground using the tailwheel for control to the tail up nice and high with the aircraft attitude essentially level or in some cases actually a little nose low. This puts the full weight of the aircraft on the mains which allows them to generate the tracking side force we want to maintain a straight ground track. It also puts the rudder fully into the airflow and makes it effective as well. Again do not spend any more time than necessary with the tail low and the tailwheel just above the ground. This is a setup for losing directional control.


We also need to understand that our aircraft have a whole series of tendencies that lead to the aircraft naturally wanting to turn left with the application of power. These left turning tendencies are beyond the scope of what I want to talk about here but suffice to say they are greatest at low speeds and high power settings as we have on takeoff and initial climb. Before adding power for takeoff mentally prepare yourself for the model to go slightly left and be ready to counter this as soon as you see it. How much depends largely on the model and is one of the things a pilot needs to learn as part of getting to know his aircraft when he first starts flying it.

If there is a crosswind present it will attempt to weathervane the model into it as it tracks down the runway. This should be thought about and planned for before takeoff. If I had to choose a crosswind I would take a wind in my face as I look across the runway as opposed to a wind from behind me. The reason is a wind blowing at you will tend to weathervane and rotate the model away from the flight line rather than into it.

A wind from the aircrafts left (port) will exacerbate the models left turning tendencies and a wind from the right (starboard) will tend to mitigate them.

For anyone who has not ever had a ride in a full scale tail dragger that is something I wish we all could experience. As a kid I spent many hours with my dad in J3 cubs and still remember being fascinated by the dance of the rudder pedals as we made our way down the runway. Our models are no different. A pilot must quickly detect and correct directional deviations when the error is still small through a series of small quick deliberate inputs which are much better than big full scale deflections which will often lead to over-controlling and large swerves or ground loops. As the aircraft gains speed the rudder needs less deflection for control and we should see our inputs becoming increasingly smaller as we gain speed.

Many RC and quite a few full scale pilots truth be told have never taken the time to understand or had someone fully explain the many complex goings on during takeoff and landing. The fact that these happen in a small amount of time makes the problem all the more challenging to pilots bewildered that their models are headed somewhere they don't want them to be.

Simple right LOL. I haven't even really touched on control inputs and goals for a crosswind takeoff. Lots of good source material out there. The challenges of Circuits & Bumps are one of the reasons I enjoy them so much. They are a lifetime challenge.
 

nhk750

Aviation Enthusiast
#10
Good dissertation, and I appreciate the information. I only fly tail draggers for now, maybe someday I will build a tricycle gear airplane. I am learning to stay ahead of the aircraft so I don't have to react and instead fly with precision. Being a real world pilot, I am used to rolling on the throttle to full, so I do the same for rc, but I am learning that you don't always need full throttle, especially when I build an airplane that has excess power. I always try to learn from every crash and close call as it is always a learning process every time I fly just like you say.