By Gordon Penner, FAA Gold Seal CFI, NAFI Master CFI-Aerobatics
The hammerhead maneuver is one of my favorites. It’s a maneuver that always invites a lot of discussion. It’s also one of the harder ones to teach. The conversations about the hammerhead always center on the rotation, so let’s tackle that aspect. I’ll be talking about the lead-in to the rotation, then the two halves of the actual rotation. For the purposes of this discussion, let’s assume that we are hammering to the left. Aircraft with the clockwise-turning engines (as viewed from the pilot’s seat) hammer easier to the left. Those with the Russian engines hammer better to the right.
Just as a good landing is more likely to occur following a good stabilized approach, a good rotation begins with a good upline. A lot of mistakes during the rotation come from beginning that rotation when the aircraft isn’t completely vertical. Using the correct visual reference, whether using a reference on the aircraft structure or a sight gauge, will not only ensure that the aircraft is vertical in pitch, it will ensure that the aircraft doesn’t have a low wing (which is a rudder input) on the upline.
The stick must not be frozen in position, in pitch, after the pull up to vertical is initially made. This is a common mistake. As the aircraft continues on the upline and slows down, it will creep either negative (slightly on its back) or positive (nose not fully 90 degrees up from level). The pilot must look at the reference guide on the airplane and the horizon and move the pitch control as necessary to maintain the correct vertical attitude for the whole length of the upline.
When to kick the rudder is the next item. By the way, the rudder input isn’t actually a kick, but a smooth, fast, feed in. Most people kick too early. This causes what we call a “fly-over.” By this definition, a fly-over is when the airplane flies up and over in an arc instead of rotating about a point close to or within the dimensions of the aircraft. In this case, the aircraft still has some energy left over when the rudder input is initiated. It also doesn’t feel good.
Each airplane is different, but kicking at the proper time will cause the aircraft to pirouette around a point without much fuss. Kicking too early or too late, however, will cause the aircraft to buck and snort, and it will look like a partially unfolded lawn chair thrown out of the back of a moving pickup. In the case of the Decathlon,there’s a gentle shudder that the aircraft gets when the time is right. Also, as I’m looking to the horizon at my sight reference, it seems that when the time is right I haven’t stopped moving upward, but that I am still creeping uphill very slowly. Although I perceive a slight upward movement, a ground observer will see that the aircraft appears to stop. Here is where some ground coaching can help.
But don’t wait so long to kick that you get into a tailslide. If the airplane appears stopped in its upward motion to the pilot, a ground observer will see that the aircraft is traveling backwards. The flight controls of many airplanes can’t take the stress from the reversed airflow. Most people tie some yarn on the aircraft structure in the pilot’s sight line but out of the prop wash. This yarn normally trails behind the aircraft. Never let this bit of yarn point forward!
The control inputs at the kick are left rudder, then opposite aileron, then forward stick. There should be a slight delay between each of these inputs—they shouldn’t be simultaneous. Put in enough aileron to keep from rolling. The key here is how much forward stick to put in. Too much forward stick could set up the conditions for an inverted spin.
I use a trick that was taught to me by instructor Rich Stowell. On the upline, you are watching the wing tip or your sight gauge, holding your vertical line when the time comes for the kick. As you put in the rudder and aileron inputs, don’t let your eye follow the wing tip as it drops. Keep your eye on the horizon and put in just enough forward stick to put the nose through that same spot on horizon that the wingtip just vacated. This technique should keep you from using too much forward stick.
From nose on the horizon to straight down, don’t just hang on to the controls. At this point you already have full rudder in. Maintain that. Keep working the ailerons to keep the wings in the plane of rotation. However, you may already be close to full aileron input in some airplanes. The forward stick input will be your most powerful friend right now. Air show pilot Brett Hunter teaches that, once the nose is at or below the horizon, pumping the stick forward and back continuously as necessary will keep the nose yawing around, and that it will also help keep the airplane in the plane of rotation.
I mentioned before that the control inputs for beginning the hammerhead rotation could also inadvertently cause an inverted spin. Kicking at the right time and using the Rich Stowell method with the forward stick as outlined above will usually prevent an inverted spin entry. However, as soon as you find the airplane doing something unpredictable, discontinue the maneuver immediately. As they say in Top Gun, “don’t push a bad position.” Center the rudder, aileron, and elevator controls, and pull the throttle to idle. The heavy end of the aircraft will seek the center of the earth, and it will begin flying again. If you stop using the offending inputs as soon as things start getting ugly, the aircraft should never fully enter the spin. If a spin does result, using the Power Aileron Rudder Elevator (PARE) spin recovery procedure works whether upright or inverted.
I am assuming, of course, that when practicing this maneuver that you have obtained sufficient altitude, have loaded the aircraft within the aerobatic center of gravity, and that you have already had spin training. You can also see that you should not teach yourself this or any other aerobatic maneuver. Get the proper training first.
I love flying the hammerhead and I love teaching it. It’s one of the most satisfying maneuvers when done well—whether competing or not. It definitely has a “sweet spot” to it. Learn it safely and enjoy!