bruce@bruceair.com
Seattle, WA
Every seat's a window seat on BruceAir
bruce@bruceair.com
Seattle, WA
Every seat's a window seat on BruceAir
According to the FAA (FAR §91.303), aerobatic flight is defined as “an intentional maneuver involving an abrupt change in an aircraft’s attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight.” A more general, but equally accurate description, might be “sky dancing.”
Regardless of whether they’re flying for fun, competing, or performing at air shows, aerobatic pilots use precise descriptions of specific maneuvers, some of which are explained on this page.
BruceAir doesn’t do “stunts”—“stunts” and “tricks” are for the movies. Aerobatics (sometimes called “acrobatics”—the terms are essentially interchangeable) is precision flying. Like an element in gymnastics or figure skating, each aerobatic maneuver is carefully planned and executed, and it follows a specific profile (i.e., entry and exit altitude, speed, and path through the sky in three dimensions). Although it may look like it from the ground, aerobatic pilots aren’t just flinging airplanes around the sky.
You can find videos of many common aerobatic maneuvers, like the sample below, at BruceAir's channel on YouTube.
Unlike normal and utility category
aircraft (FAR
§1.1 and
§23.3 define aircraft categories), aerobatic airplanes also must undergo
rigorous testing to ensure that they remain controllable throughout
a wide range of maneuvers, including
spins. To see pictures of and learn about of a variety of aerobatic
airplanes, visit Aerobatic
Airplanes here at BruceAir.
Airplanes approved (“certificated” in FAA-speak) for aerobatics are designed to withstand the stresses imposed by aerobatic maneuvers. But aerobatic aircraft are much more than stronger versions of normal airplanes. They have many other special features, such as quick-escape canopies or doors, modified fuel and oil systems to allow sustained inverted flight, and extra-strong seat and shoulder harnesses to hold you firmly in place.
The
Extra 300L that I fly is the premiere
aerobatic airplane certificated in the Normal, Utility, and Acrobatic categories.
Most aerobatic airplanes you see at air shows are licensed in the Experimental
or Exhibition categories, which place limits on carrying passengers and
instruction.
The Extra 300L is capable of unlimited-class aerobatics (it can withstand up to +10 /–10G), yet it is a comfortable, fun airplane to fly (or ride in). To learn all about the German-built Extra 300L, see the Extra 300L page here at BruceAir.
Unless a pilot
is operating under a waiver, as at an air show, the FAA places general restrictions
on where and how aerobatics may be flown. The sidebar at right lays out
the basic rules.
In plain language, they require that pilots remain at a safe altitude away from concentrations of people on the ground and that aerobatics be performed only in good weather well away from en route air traffic.
For more information about aerobatics from the FAA, see Advisory Circular (AC) 91-48, Acrobatics – Precision Flying With a Purpose and www.FAASafety.gov.
One of the keys to enjoying aerobatics is
staying oriented during the maneuvers. Even a basic
aileron roll can tumble your gyros if you
don’t know what to expect.The good news is that no matter how dramatic a specific maneuver may look from the ground (or feel in the air), all maneuvers are combinations of just a few basic figures—viz., lines, looping segments (arcs), and rolls.
The key to orientation is knowing where to look when. Each maneuver follows a specific profile, and if you keep your eyes moving, you’ll understand more about what’s going on and be less likely to feel “discomfort.”
Most people do just fine during an aerobatic ride. Here are a few helpful tips to make the experience more enjoyable:
Don’t stress about getting sick.
Nearly everyone returns from an aerobatic flight with a huge smile.
Very few people experience more than mild discomfort, and I usually
get us back to the airport well before that discomfort escalates.
Aerobatics
look graceful from the ground, but when you fly or ride through the maneuvers,
you experience positive and negative Gs—multiples of the force of gravity.
If you’ve ridden a roller-coaster or been pressed back in your seat during
a rapid acceleration in a car, you’ve experienced Gs, albeit relatively
mild, mostly positive Gs.
During a typical aerobatic ride, you’ll experience a maximum of 3–4 positive Gs (i.e., 3–4 times the normal force of gravity) and a minimum of about –1G.
Unlike jet fighter pilots, who have the engine power to sustain high G for extended periods, those of us who fly small piston-engine aerobatic airplanes can’t maintain high-G loads for more than a few seconds. The airplane runs out of energy when it is highly loaded.
By the way, that’s one reason we don’t wear G-suits. The other is that those suits require complicated sensors, air compressors, and other gizmos that aren’t practical in the types of aircraft we fly. Aerobatic pilots must stay in reasonably good physical condition and gradually develop (and then fly regularly to maintain) G tolerance.
To learn more about Gs while flying aerobatics, see the following Advisory Circulars from the FAA:
When you see a BruceAir Video link on this page, you can watch a video captured with the Extra 300L’s on-board video system.
All
of the videos below are in
Windows Media Player format. They are stored in one of my
SkyDrive folders. For more information about the videos, see the
BruceAir Videos page here at BruceAir.
You can find additional videos of many common aerobatic maneuvers at BruceAir's channel on YouTube.
The following sections comprise a quick
guide to the basic maneuvers you’ll encounter on a typical aerobatic ride
or lesson at BruceAir.
Note that my descriptions and the accompanying videos do not necessarily show the competition versions of these maneuvers. When I demonstrate aerobatics during rides or training, I modify the maneuvers to make them easier for folks to enjoy.
You can find videos of many common aerobatic maneuvers at BruceAir's channel on YouTube.
The International Aerobatic Club (IAC) publishes detailed descriptions of aerobatic figures on its website. You can also find much more information about aerobatics online at the rec.aviation.aerobatics FAQ.
As the lawyers say, for you pilots out there, none of the following is intended as instruction. It’s just a guide to help you understand what’s going when you fly at BruceAir and to help you enjoy your flight. If you want to learn how to do aerobatics, get competent instruction in an appropriate aircraft.
Aerobatic competitors and airshow pilots choreograph their flights with the Aresti System, named after Don Jose Luis Aresti Aguirre, the Spanish pilot who invented the “Aresti Aerocriptographic System.” The beginning of each maneuver is designated by the black circle. Solid lines show the airplane’s ideal path during a maneuver. Dashed lines indicate inverted portions of a maneuver, and arrows mark rolls. The vertical bar denotes the end of the maneuver.
You can learn more about aerobatic figures on the IAC website. For a detailed discussion of Aresti notation, see the article “Aresti Made Simple” (pdf).
During
an aileron
roll, the airplane rotates 360 degrees around its longitudinal axis
while the nose remains pointed at a specific reference straight ahead. In
other words, the airplane “twirls” around a line drawn from the tip of the
nose to the tail, as if you held your outstretched arm straight and rotated
your wrist and elbow.
Throughout this maneuver, look straight ahead at a cloud, mountain peak, or other reference that I point out.
As the aileron roll begins, I pull the nose up 20–30 degrees above the horizon. I then stop the pitch-up and move the stick to the left or right, depending on the direction of the roll. As the wings bank, I keep the nose pointed at the reference and let the airplane fly through a smooth arc. The roll ends with the wings level and the nose still pointed at the reference, but about 20 degrees below the horizon; finally, I smoothly pull the nose up to level level flight.
We start with half-stick-deflection rolls and then, if you’re up for it, we’ll do faster rolls (the Extra can roll at about 400 degrees/second—i.e., a complete rotation in less than a second) later in the ride.
The
loop is the
classic barnstormer maneuver of yore. We start this maneuver from level
flight, pull the nose up, and while keeping the wings level, fly through
a complete circle. A properly flown loop begins and ends at the same
altitude and on the same heading.
During a loop you experience 3–4G during the initial pull-up. At the top of the maneuver, I relax the pull to allow the airplane to fly a constant arc as our speed decreases; at that point you feel a little light in your seat while we experience about 0.5G. As the airplane flies down the back side of the loop, I smoothly increase the pull and you feel the G build back to 3–4G.
During the loop, look around to stay oriented. As the maneuver begins, look straight ahead, but as soon as the horizon disappears, glance left and right to watch to wings tracing an arc through the sky. As we approach the vertical, stretch your neck and look straight back at the tail so that you can see the horizon appear as we reach the top (inverted) point of the loop. Then smoothly tilt your head forward and look straight ahead as we fly down the back side of the maneuver and return to our original altitude and heading.
If you are comfortable with basic loops, we can add variations such as a loop with an aileron roll on top. The Cuban 8 maneuvers described below also combine looping and rolling elements.
A barrel roll is a combination of a loop and a roll (often confused with the aileron roll, the barrel roll is a different animal). There are several ways to fly a barrel roll, but during an aerobatic ride, we’ll use the following procedure:
From level flight, I pull the nose up smoothly but quickly to 45 degrees above the horizon. As the nose reaches the 45-degree point, I start a smooth coordinated roll (usually to the left) while gradually increasing the pull to start a loop. I continue the maneuver by using aileron, elevator, and rudder inputs to maintain a constant, smooth rate of change in both pitch and roll. As we reach the inverted position at the top of the “loop,” the wings should be level and the nose should be on the horizon, with our heading 90 degrees from our original direction. The maneuver continues with the nose falling through the horizon as the airplane rolls back toward wings level. The barrel roll ends, like a loop, with the airplane returning to level flight on its original altitude and heading.
You should look around during a barrel roll, which ideally is a smooth, graceful maneuver. Enjoy the view as the world goes upside down, but make sure you look straight ahead as we fly through the top (inverted) portion of the maneuver. It’s always cool to see “the earth above and the sky below.”
The
half Cuban 8 is a classic reversal maneuver you’ve probably seen at
air shows. It allows the pilot to convert speed into altitude and then back
into speed while reversing direction within a small area. Fighter pilots
have used variations on the half Cuban 8 since the early days of dogfighting.
Legend has it that the full Cuban 8 got its name after a pilot named Len
Povey invented it on the fly during an air show in Cuba in 1936. In a full
Cuban 8 (see below), the airplane traces the path of a figure 8 lying on
its side. It looks like two loops with half-rolls as the airplane flies
down the back side of each loop.
A half Cuban 8 (a little easier on the stomach for an inexperienced flier) is, as the name implies, one-half of the complete maneuver. We begin from level flight and pull up exactly as if flying a loop. As the airplane starts down the back side of the loop, I push the stick forward to establish a 45-degree inverted descent (i.e., a 45-degree down line). I maintain that line for a moment, roll the airplane upright, hold the 45-degree down line again briefly, and then pull the airplane back up to level flight. A variation on the same maneuver uses one-and-half-rolls to return to upright from the inverted 45-degree down line.
We end up heading 180 degrees from our original direction, but back at our original altitude and airspeed. During the beginning of a half Cuban 8, look around as you do during a loop. When I establish the inverted 45-degree down line, glance left or right to take in the unusual view, and then look straight ahead when I call the start of the roll to upright.
The half Cuban 8 is often a highlight of a ride. It combines positive G, looping, hanging-from-the-harness negative G, and rolling. You’ll probably find it confusing at first, but if you’re up for more than one, it will quickly start to make sense.
As the name of this maneuver
implies, it’s based on the half Cuban 8. The only difference is how the
fun begins.After establishing a horizontal line, I pull the airplane up
to and establish 45-degree line. Next, I roll the airplane inverted and
hold the 45-degree up line as the speed bleeds off to < 80 knots, and then
I smoothly pull the airplane through a looping arc that, like the half Cuban
8, ends with the airplane having changed direction 180 degrees and back
at its original altitude.
During the beginning of a reverse half Cuban 8, look straight head as I begin the pull to the 45-degree up line, glance left or right to confirm the angle, and then look straight ahead when I call the start of the roll to inverted. After we’re inverted, glance left or right again to check out the same view that Space Shuttle astronauts see during launch, and then switch your gaze straight ahead for the looping part of the maneuver.
The hammerhead, essentially an aeronautical
cartwheel, is a favorite maneuver among folks who take aerobatic rides.
You’ve seen the hammerhead (often erroneously called a “hammerhead stall”)
in many variations at air shows.
This maneuver begins from a horizontal line. I pull the airplane up smoothly but aggressively to establish a vertical line. I hold the vertical line until the airplane almost runs out of airspeed, and just at that point, push full left rudder to make the airplane pivot, or cartwheel, around its left wing. I then establish and hold a vertical dive before pulling the nose back up to a horizontal line. The hammerhead ends with the airplane flying 180 degrees from its original heading.
When I start the hammerhead, look straight ahead, but as the nose rises, shift your gaze to look out along the left wing and enjoy the view as we climb straight up.
During the pivot at the top, rotate your head to look straight over the nose for the vertical dive and the pull back to level flight.
After an introductory hammerhead, I may demonstrate variations on the maneuver, including a vertical roll (.wmv) as we climb straight up or a roll during the vertical dive.
If you’re interested in more detailed
information about aerobatics, check out the websites of the
International Aerobatic Club (and its
sibling organizations around the world) and the
International Council of Airshows (ICAS),
the sponsoring organization for most air shows and air show performers in
North America.
Each of those organizations provides information about aerobatics as a sport, valuable training tool, and spectator event. Another source of information is the rec.aviation.aerobatics FAQ.
A good general introduction to aerobatics is
The Basic Aerobatic Manual by
William
Kershner (ISBN 978-1-56027-617-3).
Basic Aerobatics (ISBN 0070629269) and its sequel Advanced Aerobatics (ISBN 0070633029) by Geza Szurovy and Mike Goulian are excellent, thorough discussions of aerobatics.
Skydancing: Aerobatic Flight Techniques by David Robson (ISBN 1-56027-389-5), offers additional insights.
Other good titles by Duane Cole (but out of print and harder to find) on the subject include:
