Beyond the PPL: Aerobatics
- Credit: Archant
Aerobatics are a great way to improve your all-round flying and almost as old as aviation
In Those Magnificent Men in their Flying Machines an untrained pilot climbs into an aeroplane declaring, ‘There is nothing a Prussian officer can’t do’. He is clutching a book of instructions. In rather the same spirit back in the Eighties, I set off to learn aerobatics in my Skybolt armed only with Neil William’s textbook ‘Aerobatics…’ though I didn’t actually consult it whilst flying. Without any dual instruction I worked my way up to Unlimited competitions, winning several at lower levels on my way, (my best result at an Unlimited was third place).
In those days there were few aerobatic training facilities, and none at all near me, so I had no choice. However today there are dozens all over the UK. Learning with an instructor isn’t just a lot safer; it’s a lot quicker. Furthermore, self instruction is soon to be illegal in EASA aircraft, as from 8 April 2015, you will need to have an aerobatic rating in order to fly aerobatics in one. My homebuilt Carrie Super Wot is not an EASA aircraft, so presumably someone could still teach themselves aerobatics in that and other homebuilts (including 120 Vans RVs), at least for the time being.
I think most aerobatic pilots now in their sixties learned as I did – alone in the cockpit but with the help of textbooks and the occasional critique (the posh word for someone watching on the ground). Obviously, if you do teach yourself, you should go cautiously. You must have an aeroplane cleared for aerobatics, fitted with a G-meter and suitable for beginners. An Extra 300 or Pitts Special will be too high-powered; something like a Tipsy Nipper, a Cessna Aerobat or Stampe would be better (and I would still advise dual training). Having sufficient altitude to recover if something goes wrong is good insurance. If the aeroplane doesn’t have an on-board starter, practise over terrain suitable for forced landings.
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I have a book listing every Tipsy Nipper and its fate; sadly quite a few were written off in crashes. Most were botched forced landings following a stopped prop caused by aerobatics, the pilot unable to re-start the VW engine since it needs to be swung by hand. Finally, don’t exceed the maximum allowable rpm, which might mean throttling back at higher airspeeds. Having said that, it was commonplace for aerobatic competitors in my day to overspeed the propeller and while this increases engine wear, it is unlikely to bring much damage if done occasionally.
Looping the loop Formal training, which emphasises safety, usually begins with recovery from unusual attitudes and how to stop a spin. However, the time-honoured first manoeuvre for most people who teach themselves is a loop. Here is the procedure I used to ‘teach’ nonaerobatic pilots in the Stampe. (It works on just about any aerobatic aeroplane.) Dive to ten knots above cruise speed, and pull back on the stick at 3.5 G. As you pull back, glance at the G-meter but keep your eyes on the horizon, which you must keep level. Beginners flying with their right hand on the stick nearly always introduce some right aileron at this point. As the horizon disappears, relax the pull slightly, but keep the loop going. Tilt your head back and wait for the horizon to re-appear. When it does, it will probably be on a slant, but be wary of correcting with aileron as you will be disorientated and may make things worse. As the aeroplane completes the loop in a dive, you will be back on familiar territory. Pull at 3.5 G to come out of the dive, again glancing at the G-meter but keeping your eyes outside the cockpit. (This is where you might need to throttle back to avoid overspeeding the prop.)
The loop has a long tradition. A Frenchman called Pégoud drew massive crowds in Edwardian times flying successive loops in an specially strengthened Blériot monoplane. It’s an easy manoeuvre to fly if you use common sense. It needn’t apply much more strain to the structure than bad turbulence. Sadly, the loop also has a long tradition of bringing pilots to grief. In the years between the wars, the salesman for the delightful 35hp Aeronca C3 enjoyed performing loops to show off the aeroplane’s strength. It was observed that he was clumsy, pulling the nose up in a sharp curve. One especially heavy pull-up finally broke the Aeronca’s ultra-light airframe, and he died in the crash. At an aerobatics contest in Belgium I met an Extra 300 pilot who gave aerobatic displays in his country in the Middle East. He expected to win, but scored badly and was humiliated. At his next display, perhaps determined to show everyone how good he was, he looped too low and hit the ground. He was pointed at the crowd and took several spectators with him.
The stall turn Once you’ve mastered the loop, you can try a stall turn. This begins in the same way, but when the aeroplane has pitched through ninety degrees and is pointing straight up, you ease the stick forward to hold the aircraft vertical. Looking over the nose at this point will give you a view of nothing except empty sky, so the trick is to turn your head as the horizon disappears below at the start of the loop, and look at the wingtip instead. When that is vertical, so is the aeroplane. If you introduced some aileron during your pull on the stick, you will be leaning to one side (usually centred at this point. A vertical climb can’t continue indefinitely; at some point the aeroplane’s weight will win out over the engine’s thrust. When that happens, the aircraft can slide backwards in a manoeuvre called a tailslide. This is to be avoided, although the tailslide is actually a competition manoeuvre in advanced competitions. The French call the tailslide ‘the bell’ because the aeroplane swings like the clapper in a bell after the nose plummets down. You control the direction of fall, incidentally, with elevator, and since the aeroplane is going backwards, the elevator works in the opposite sense – forward stick for a ‘canopydown’ tailslide.
As I said, you should avoid a tailslide. You do this by yawing the aeroplane so that it falls sideways before it loses the last few knots of forward airspeed and starts going backwards. Timing is critical, because if you wait too long before ruddering over, you risk a tailslide. Apply rudder too soon, when the aeroplane still has lots of airspeed, and two things happen: firstly, it yaws over painfully slowly, flying for an interval on its side. The other problem is rudder-induced roll, so that the aeroplane rolls onto its back as well as yawing. The latter can be countered with opposite aileron, but the manoeuvre will look untidy.
So when should you rudder over in a stall turn? Most instructors suggest an airspeed. My own rule of thumb is when I’ve reached quarter deflection on rudder counteracting spiral airflow. The direction in which you rudder over, by the way, is always opposite to the corrective rudder you used when climbing after take off. That way spiral airflow helps the yaw rather than working against it. In a Lycoming or Continental-engined aircraft, yaw left; in a Renault Stampe, yaw right. A third way of telling when to rudder over is by counting seconds. Three seconds after hitting the vertical is about right for low-powered draggy aeroplanes like the Currie Wot or Cessna Aerobat, six second for immediate trainers such as the Slingsby or Extra 200. Contemporary accounts suggest that pilots were flying stall turns in the Great War, but only when stationary engines were introduced. Trying to fly one in a rotary-engined Camel would have been nearly impossible with that engine torque.
The aileron roll
The next manouveure, the roll, was actually performed by Pégoud before the Great War and pilots flew rolls all the time during the conflict. One variant was even named after a German ace, the Immelman Turn, although historians are uncertain about how it was done. The Fokker Eindecker with wing warping certainly couldn’t have flown the half-loop, half-roll that is its present day equivalent. Contemporary accounts of Sopwith Camel talk about ‘revolving the stick like stirring a pudding’, but with the entire egine rotating at about 1,000 rpm, Camel pilots had problems and opportunities present day aviators can only imagine. They likely flew a cross between a barrel roll and a flick roll.
The roll that I’m going to suggest you begin with is the aileron roll. This is the simplest one, using just aileron, without rudder or elevator. There is one risk and it’s this: centring the ailerons when the aircraft is upside-down, so that it stops rolling. A few pilots, (very few), do this the first time. The next thing that happens is that the nose drops and the aircraft falls into a full-power inverted dive. If the pilot then pulls back on the stick, the aeroplane will lose a lot of height and V and its G-limits before recovering. There is also a risk of the pilot blacking out. However, I’ve spoken to people to whom this happened and survived. It needn’t be disastrous: a full-power half roll pull through is an accepted intermediate-level aerobatic manoeuvre and shouldn’t lose more than 800 ft.
However it’s not something a beginner would want to experience, so keep the stick over until the aeroplane comes upright. Don’t centre it just because you are upside down. If you just shove the stick over in a cruise, most aeroplanes will end up hopelessly nose-down. So before you begin the roll, dive to ten knots above cruise speed. Then raise the nose by five to ten degrees and immediately shove the stick all the way over (to the left in Lycoming-engined aircraft). If you hesitate after raising the nose, the aircraft will begin to slow down. By the time the roll is completed the nose will have dropped, hopefully by the same amount you raised it by, and you will be in a shallow dive.
You can then gently raise the nose back to level flight. In fast, high-powered machines with powerful ailerons, like the Extra 200 or Slingsby T67, you barely need to raise the nose to begin with and the dive at the end will hardly be noticeable. However, to roll a more draggy, lower-powered aeroplane with relatively feeble ailerons like the Auster Aiglet or Tiger Moth you need to use rudder and elevator as well as aileron. This produces the true roll, one which is axial in which the nose stays centred on the horizon. In a left-hand roll, you apply right rudder in the first quarter, forward stick while inverted and gradually reverse the rudder in the third quarter, ending with left rudder and rather less aileron. This is tricky to teach yourself, but very rewarding to master.
Cubans and Immelmans
Next come three manoeuvres which combine the loop and a half roll. The half-Cuban positions the half-roll in the final third of the loop (from an inverted dive to upright). The half-reverse-Cuban positions the half roll in the first third of the loop (from a 45-degree upright climb to one that is upside-down). Finally, the Immelman Turn or half-loop, half-roll, positions the half roll at the top of the loop. All three, like the stall turn, are turn-around manoeuvres, which is useful if you’re giving a display and want to stay in front of the audience.
The barrel roll
Finally, there is another variant on the roll; the barrel roll. It’s about the only aerobatic manoeuvre some draggy underpowered aeroplanes can manage, so it’s sometimes seen flown in vintage types at airshows. The barrel roll uses rudder and elevator to keep the nose up and assist in rolling the aeroplane. As you shove the stick over, you also pull back on it and push on rudder in the same direction as aileron. Like the slow, or axial roll, this is a tricky coordination manoeuvre, but it’s potentially rather more dangerous. In an axial roll you can see the horizon, but in a barrel roll, because you begin by pulling back on the stick, there’s nothing to sight on. By the time the ground re-appears, you can find yourself in a high-speed dive. In theory, it’s a basic manoeuvre that doesn’t lose height, so history is full of novice aerobats (and some quite experienced ones) barrel rolling at low altitude and hitting the ground. Practise this one with plenty of height in reserve and be wary of using it low-down.
Did you enjoy this article? Then there is advice on performing an Overhead Join here.