Hammerhead / Stall Turn
History of Stall Fighting
The stall turn is an evasive maneuver dating back to WWI. It was called renversement or reversing but the Air show announcers call it a Hammerhead as the smoke of the figure draws in the sky is resemble to this. In WWII Japanese Zero pilots did a lot and marveled in this maneuver.
It was method to get behind the enemy or used to escape the pursuit. Practically the Japanese pilots enter the stall turn at full speed from level flight or from long shallow dive to gain more speed. Following the moment they pull straight up and climb vertically long until the plane lost or nearly ended up the speed. The pilots give rudder a yaw trying to rotate 180 degree on one wing side and dropping straight down returning to normal altitude. The turn looks best if it is done in place slowly.
In the early WWII when Zero was in service it was faster and lighter than other enemy plane so it was a clever idea to use Stall Turn as a tactic in hot pursuit. When the enemy plane was pursuing behind Zero it might aim to climb straight up facing the sun thus reduced the chanced of being hit by the machine gun. From the vertical pursuit, as the Zero speed is greater than the enemy plane so the US fighter would be first to stall and automatically veered the nose down while Zero would take this opportunity to make stall turn, dodging behind the enemy plane and opened fire.
Here is how to do it.
Enter at full power and maximum airspeed. Pull the aircraft up through a quarter loop into a vertical climb. The speed will decay but before upward motion stops firmly apply full rudder to yaw the aircraft through a cartwheel of 180° until the nose is straight down. Dive vertically to the same altitude as the maneuver started, then pull out, exiting in the opposite direction.
The timing of applying full rudder is critical. If instigated too soon it results in a wingover. If instigated too late the plane will fall into a sideslip or else enter a tail-slide which most aircraft are restricted from doing. A common mistake is to not lose flying speed at the top, but to fly a 180 degree U-turn instead of rotating in place. In such case this is not a stall turn. It is called bad wingover.
When performing the traditional stall turn, you must ensure that the aircraft is tracking in a manner that is parallel to the runway and that the model’s wings are level to the horizon. If the wings are not perfectly level and you pull the stick back to perform the quarter loop to establish a vertical up-line, the model will be tilted. You’ll then need to apply rudder input to correct the model’s flight path. If this were a competition, points would be lost. All in all, make sure the wings of the model are level before attempting this maneuvers.
Another note for the pilot who wants to execute the stall turn is to determining the wing direction. RC flyer should yaw the model plane with rudder to the side that hit by the wind. This will make stall turn in corresponding to the nature force. Wind speed is also one crucial factor to perform stall turn. Airspeed actually increases as the plane fly into stronger wind which will then increases the lift and kicks the plane even higher. For this reason stall turn is more fun on the windy day.
EXECUTING THE STALL TURN ON YOUR RC PLANE
Having aerobatic plane such as F3A, Extra, Edge, Katana, for example will be an ideal plane to start with. However the low-wing trainer plane is fine for this maneuver as well so don’t be scare to start since most plane can make this thing right. If you never try Hammerhead before I would suggest you to perform at higher altitude until you are comfortable with this move. Getting start with take off and fly your plane parallel to the runway the performance will be in accordance with these procedures.
Step 1: While the plane is leveling parallel to the runway increases the throttle to the max and gently makes a 90 degree straight climb. You must determine yourself the appropriate altitude that will execute the Hammerhead maneuver but keep it high at first. Remember that you have to exit this maneuver at the same altitude where you start which means the starting point and exiting point must relatively be at the same level.
Step 2: As the plane climb straight up vertically it is entirely up to you for the height you want to snap in to the Hammerhead, remember that too long vertical line may drift the airplane, which will require some corrections along the path. While too short a climb will look “impetuous.” In general the vertical up-line should be at least 3 to 4 seconds before execute the turn. At certain point of climb cut the engine power and apply full rudder in one direction. It is helpful to respect the wind as you can get turn stall or Hammerhead into the wind direction to avoid any flopping tendency at such point.
Step 3: Once your plane is about to stop climbing on the vertical posture apply full rudder deflection until the model pivots to almost 180 degree. At this mean you can release the rudder input and keep the plane head plummets 90 degree to the ground. The length of the down-line dropping should be the same as it was on the vertical up-line. Please remember that the head dropping speed should remain idle until you recover the exit point where the model has been started. Exit the Hammerhead with the same altitude in which it was entered the maneuver.
After finishing this performance the model will be travelling in the opposite detection. A perfect maneuver for Hammerhead should be completed with the same loop as you performed in the first step. Practice this skill over the Flight simulator or on the real model until the maneuver looks smooth and equal in altitude for both entering and exiting the Hammerhead.