Conquer the Three-turn Negative Spin

Sep 30, 2013 1 Comment by
 

In the early days of aviation,  spins were often fatal because most pilots did not understand how to properly recover from a spin. While in an upright spin, the pilot would pull back on the elevator stick in an effort to save the airplane (and their life!) and only make the situation worse. Since the spin occurs when the aircraft is in a stalled state, adding elevator just keeps the airplane stalled. If you are new to the aerobatic world, you may be unfamiliar with the term “stall” when it comes to various aerobatic moves, as most student pilots are only aware of the consequences that stalling an airplane can have on a landing. However, some maneuvers are to be performed while the aircraft has stalled, like the stall turn, the tail slide, and the spin, to name a few.

Let’s examine the key control inputs in executing the three-turn negative spin. A proper negative spin entry begins from inverted horizontal flight at a fairly high altitude while flying parallel to the runway. Then you must decrease throttle and feed in enough down-elevator to maintain altitude. Eventually, elevator authority will not be effective and the airplane will stall. At that instant, the nose will fall and a wingtip will drop in the direction that the spin rotation should be flown. If the left wingtip drops, the pilot should perform the spin to the left, which will require left aileron, right rudder and down-elevator. Similarly, if the right wing tip drops, the pilot should apply right aileron, left rudder, and down-elevator.

Let’s start by taking a look at how your aircraft has been set up. Then, we will go over all vital inputs needed to execute this maneuver, as well as a few key flight techniques. After all, the goal is to make you a better pilot!

First things first
I like to use flight modes. In the simplest form, this means that all dual and/or triple rates can be found on one switch. If you want to perform a maneuver like the spin, you don’t need to remember which independent switch setting you used for the rudder, elevator and ailerons. Instead, you can apply all of these deflection and exponential amounts to one switch position and simplify your life.

If your transmitter does not have the ability to use a flight mode, or something to the same extent, I recommend that you make your low-rate settings applicable to the spin. Then you can make your high-rate settings apply to only extreme 3D maneuvers. I think it is critical to minimize the amount of time you spend searching for rate switches so you can concentrate on flying the aircraft!

The amount of control throw that’s required to spin the aircraft will differ between airframes. To start, I recommend 15 degrees of aileron deflection with 20% exponential, 20 degrees of elevator deflection with 35% exponential, and 35 degrees of rudder deflection with 50% exponential for the low rate setting.

Please remember that exponential (expo) should be used with care. Expo “softens” the feel of the aircraft around center stick on a given control surface to make the aircraft less erratic. A lot of exponential should only be used with a lot of control throw; otherwise, the aircraft may be extremely sluggish. Start with small increments and increase the percentage until you are content with how your aircraft feels.

The three-turn negative spin
Begin by climbing to a safe altitude, which for a typical park flyer that has a wingspan between 48 and 52 inches, is between 500 and 600 feet. Your entry altitude needs to allow us enough space to establish a brief vertical downline after the spin rotations have been completed. Once the airplane is at altitude, fly it inverted and parallel to the runway at about 25% throttle. When the airplane is about 100 feet away, decrease throttle slowly to the idle position. Feed in enough down-elevator to hold altitude. At some point, you will run out of down-elevator and the airplane will stall. This should occur while the aircraft is directly in front of you. At this point, both the nose of the aircraft and a wingtip will drop. Now, let’s say that the left wing drops first. This means that the direction of the spin should be to the left. Use left aileron, right rudder, and down-elevator to complete three rotations. Then, neutralize all inputs to establish a vertical downline. Push 90 degrees and increase throttle to exit the maneuver in inverted, level flight.

 

 Four steps to success
Now that you have a brief overview of the general control inputs that are required, let’s explore this maneuver as well as a few key flight tips by breaking this stunt into four steps:

  • STEP 1. Align the aircraft parallel to the runway and inverted. If the airplane is travelling with some airspeed, pull the throttle back to idle and slow the aircraft down as it approaches you. Now, if applicable, activate your “spin” flight mode. While the aircraft is slowing down, you’ll need to feed in down-elevator to sustain altitude. It is important to time this portion of the entry so the airplane stalls directly in front of you. When the airplane stalls, one wing will drop to determine the direction of the spin. In this example, we are spinning to the left, which requires left aileron, right rudder, and down-elevator.
  • STEP 2. Most aerobatic airplanes will spin using only a touch of aileron input. Using too much aileron may accelerate the spin rotation at times, which is not the desired result. Rather, we want to obtain a constant rate of rotation. At most, use about 10 degrees or so of aileron deflection, but hold in full down-elevator and full rudder input.
  • STEP 3. With your throttle still in the idle position, keep track of the amount of rotations the airplane has performed and maintain the same control inputs.
  • STEP 4. As the last rotation nears completion, you’ll need to neutralize all control inputs and establish a vertical downline. Then, after a brief line segment is shown, perform a gentle 90-degree push to exit inverted in horizontal flight. It is important to realize that heavier airplanes take longer to exit a maneuver like the spin. Once you neutralize control inputs, the aircraft may complete another portion of a spin rotation. When you know the tendencies of your plane, you will be able to compensate for this by timing your inputs properly so the rotation stops at exactly three rotations.

Flight advice
When watching various pilots performing the spin, I have seen a few problematic areas arise. One major issue I’ve encountered is having the airplane’s engine quit during the maneuver. This often happens as the pilot has a relatively low idle when using a glow or gas-powered model. When flying an airplane with an internal combustion engine, set a safe idle before you take to the skies. If you are using an electric aircraft, I prefer to have an idle where the prop is spinning at a very low rpm. I know that some pilots prefer to have the motor stop completely in the idle position, but I do not like the delay that it sometimes takes for the motor to activate. After all, it’s better to be safe than sorry!

Before entering into the spin, the airplane must stall. As I mentioned, this is shown by having the wingtip and nose of the aircraft drop before you enter the spin rotations. If this doesn’t happen, it means that you had too much airspeed going into the maneuver and a forced entry is applied.

Now that you have learned the basic fundamentals in performing the three-turn negative spin, go out and practice! The cliché practice makes perfect is true! If you have trouble performing this maneuver, break it down into steps, examine the setup of your aircraft and use the tips in this column to serve as a guide.  BY JOHN GLEZELLIS

Fixed-Wing Flight School, John Glezellis

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One Response to “Conquer the Three-turn Negative Spin”

  1. Mark Huntley says:

    its a bit confusing the say right or left wing, as the left and right wings are reversed in inverted flight. This is not mentioned in the article.

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