rec.aviation.aerobatics FAQ

Document address: faq_aerobatics.html
Frequently Asked Questions about Aerobatics

Frequently Asked Questions about Aerobatics
===========================================


Preface
=======

This document is Copyright ? 1995 by Guenther Eichhorn. It may be freely
distributed in its entirety provided that this copyright notice is not
removed. It may not be sold for profit nor incorporated in commercial
documents without the author's written permission. This article is provided
"as is" without express or implied warranty. I would like to thank everybody
who took the time to send me their comments. Many of them contributed
substantial material for this FAQ.

In particular I would like to thanks Steve Pennypacker for writing some of the
paragraphs in this FAQ list and the list of aerobatic aircraft.

Last Update: 21 March 1998
-------------------------------------------------------------------------------

Table of Contents
=================

1. General Comments
1. International Aerobatic Club
2. IAC E-mail Distribution List
3. Aerobatics Books
4. Aerobatic Airplanes
5. Basic Aerobatics Figures
6. Advanced Aerobatics Figures
7. The Aerobatics Box
8. Aerobatics Contests
2. Specific Questions


-------------------------------------------------------------------------------

General Comments
================

First a Disclaimer: Any descriptions of aerobatics figures should not be
interpreted as instructions. No pilot should attempt to fly any of these
figures in aircraft not certified for aerobatic flight. Further, no pilot
should attempt these figures without training from a competent aerobatics
instructor. These descriptions are incomplete as instructional material and
will get you into trouble if you believe that they are.

Aerobatics competition flying is organized in the USA by the International
Aerobatic Club (IAC). It is a sport that requires skill and practice. If all
the rules are followed, it is quite safe. There are several dozen regional
competitions each year in the US. Once every two years, the World Aerobatics
Championships are held. They are in different countries each time and attract
the best of the world of aerobatics competition. If you have information
about the aerobatics organization in your country, please let me know so I can
include it in this FAQ.
-------------------------------------------------------------------------------

International Aerobatic Club (IAC)
==================================


IAC Address
===========

International Aerobatic Club
EAA Aviation Center
P.O. Box 3086
Oshkosh, WI 54903-3086
414-426-4800
Membership: 1-800-843-3612
E-mail:


IAC Charter
-----------

The International Aerobatic Club, Inc is a Division of the Experimental
Aircraft Association, Inc. All IAC members are required to be members of the
parent organization, the EAA. Membership is open to all who are interested in
aviation. The IAC is also a Division of the National Aeronautics Association
and is responsible for the administration, management, and promotion of the
sport of aerobatics in the United States under the applicable regulations of
the Federation Aeronautique Internationale; Paris, France. FAI is the world
governing body for all sport aviation competitions and record attempts. IAC
represents the United States at meetings of the FAI's CIVA committee which
establishes rules worldwide for aerobatics competitions.

A list of the officers of the IAC is available at: http://acro.harvard.edu/IAC/bod.html


IAC E-mail Distribution List
----------------------------

To sign up for the e-mail distribution list, send e-mail to:

with one line in the message body:
subscribe
The subject line will be ignored. You will receive a message back, stating
that you are subscribed to the list and instructions on how to unsubscribe.
If you do not receive this message, then the subscription failed. This can be
because the program takes your e-mail address from the "From:" line. This may
not work if your mailer doesn't include the correct address in your message.
You then have to use the on-line signup-form.

Please do not send subscribe or unsubscribe messages to the list itself at
. They get distributed to everybody on the list,
which is quite a nuisance.

There is also a digest version of the mailing list available. The digest
accumulates messages till the collection has reached a certain size, or a
certain time has passed, then e-mails the collection to the subscribers of the
digest. To subscribe to the IAC digest list, send a message to:


The message body should contain the line:
subscribe iac-digest

If you only want the digest version, you should unsubscribe from the regular
mailing list (see above).


Usage
-----

Once you have signed up with the list, you will receive a message that lets
you know how to use the list.


Charter
-------

This e-mail distribution list is intended to distribute information about
aerobatics flying and the IAC in general. We plan to distribute contest
schedules and contest results, as well as safety tips, etc. We hope it will
also be used as a forum for discussions about aerobatics flying, questions and
answers concerning IAC rules, etc. How it is used is up to you all.


Caveat
------

There is just one restriction: It cannot be used for any commercial purposes.
Please understand that this e-mail distributer is located on institutional
computers and cannot be used commercially.


Help
----

If you have any questions, need help with anything, or something doesn't work,
please contact Guenther Eichhorn. You can just click on his name and send a
note through the form that comes up.


Acknowledgement
---------------

Thanks to Allan Hessenflow for hosting the IAC email list.


-------------------------------------------------------------------------------

Aerobatics Books
================

Probably the most popular instructional book for learning aerobatics is "Fly
For Fun", by Bill Thomas (available from EAA). It does a very good job of
explaining the maneuvers and how to fly them. The book has a couple of
shortcomings, however. One is that it doesn't go much beyond the maneuvers
themselves into other things you'll probably want to know. The other is that
it assumes you're flying a Pitts, which isn't the best choice for beginning
acro. This does make a difference, as performance characteristics and visual
cues are quite different than a lower performance trainer, such as a
Decathlon. If you're interested in competition, Thomas' "Fly For Fun To Win"
is also recommended.

The second book is Mike Goulian's and Geza Szurovy's new book, "Basic
Aerobatics". Few people on this list had seen the book yet. It also does a
good job of describing the maneuvers, but it also goes into lots of other
subjects like physiology and conditioning, safety, aerobatic preflights, and
costs of ownership. It also assumes you're in a Decathlon, which is probably
what you'll be flying.

Another book is Primary Aerobatic Flight Training with Military Techniques" by
Lt. Col. Art Medore, USAFR (ret). It has five sections which include detailed
ground study on a variety of topics and a curriculum for 12 flight lessons. It
also offers a section on transition from tricycle gear to tail-draggers. There
are appendices for manufacturers' recommended entry speeds for maneuvers
covered in the text. The aircraft covered a Beech Musketeer Sport III,
Cessna Aerobat, Champion Citabria, Beech T-34, Stearman PT-17, and North
American T-6.

The lesson curriculum begins with simple warm-up exercises (air work),
military chandelles, and lufberry turns. Advanced maneuvers covered at the
end include the reverse Cuban eight, the avalanche, inverted spins, hesitation
rolls, and inverted turns.

Simple sequences of maneuvers are covered and there is an introduction to
Aresti diagrams.

Other books that people seem to like a

* "Roll Around a Point", by Duane Cole
* "The Conquest of Lines and Symmetry", by Duane Cole
* "Aerobatics", by Neil Williams
* "Aerobatics Today", by Bob O'Dell
* "Flight Unlimited", by Eric Mueller
* "The Basic Aerobatic Manual", by Bill Kershner
* "Stalls, Spins and Safety", by Sammy Mason

The new second edition printing is now available from a dealer (and
aerobatic pilot) in England.

Alan Cassidy
Tharn
18, Woodhurst Road.
Maidenhead
Berkshire SL6 8TF

Tel: +44-1628 37732 (evenings only)
FAX: +44-1628 777083



-------------------------------------------------------------------------------

Aerobatic Airplanes
===================

First I want to emphasize that you should do aerobatics only in airplanes that
are approved for aerobatics. It is potential suicide to try aerobatics in any
other airplane. Other planes are not stressed for this type of maneuvering
and they WILL break. Please don't do it!

A list of aerobatic airplanes is available at http://acro.harvard.edu/IAC/acro_planes.html
with a summary of their features. If you know any of the numbers that are
missing, or know of any other aerobatic airplane (not one-of-a-kind planes
though) please let me know about it.

Which aerobatic plane to use is almost a religious question, but here are some
pointers:
The most common aerobatic planes for beginners are probably:

* Citabria
* Decathlon
* C-150 Aerobat

For more advanced aerobatics the most popular trainer is probably the Pitts
S-2A or Pitts S-2B. Most other higher performance aerobatic planes are
experimental and cannot be used for regular flight instruction.

Now on which trainer should you get started? It depends on various things, not
the least on the amount of money that you want to spend. Here are some rough
figures for hourly rates:

* Citabria: $60 - $90
* Decathlon: $70 - $120
* C-150 Aerobat: $50 - $80
* Pitts S-2A: $130 - $200
* Pitts S-2B: $160 - $220

It obviously is much less costly to get started in a Citabria or a Decathlon
than in a Pitts. And both are good enough to teach the basics of aerobatics.
The C-150 Aerobat is very limited in the type of aerobatics it can do. It
seems to be a consensus on the IAC e-mail list that it makes sense to get
started in one of these trainers and then move up to a Pitts to work on more
advanced aerobatics.
-------------------------------------------------------------------------------

Basic Aerobatics Figures
========================

A description of a list of aerobatics figures is available at http://acro.harvard.edu/IAC/acro_figures.html.
Here is a summary that tries to explain the difference between maneuvers that
are often misunderstood on the rec.aviation.* newsgroups.


Rolls
-----

There are four different types of rolls:

* Aileron Roll
* Slow Roll
* Snap Roll or Flick Roll
* Barrel Roll


Aileron Rolls
-------------

Aileron rolls are flown with the rudder and elevator in the neutral position
during the roll. The aileron is fully deflected in the direction of the roll.
This is the easiest of the rolls to fly.

The aileron roll is started by pulling the nose up to 20 - 30 degrees above
the horizon. The elevator is then neutralized and the aileron fully deflected
in the direction of the roll. The controls are maintained in that position
till the roll is completed. After the roll is completed the nose is usually
20 - 30 degrees below the horizon.

The aileron roll is not a competition maneuver.


Slow Rolls
----------

Slow rolls have to be flown normally on a straight line (exception is the
avalanche). The roll rate has to be constant and the longitudinal axis of the
plane has to go straight. This requires constantly changing rudder and
elevator control inputs throughout the roll. Hesitation or point rolls include
stops at certain roll angles. The number on the base of the roll symbol
describes the number of points the roll would have if it were a 360 degree
roll. Allowed are 2 point, 4 point and 8 point rolls. The fraction on the
arrow of the roll symbol describes what fraction of a full roll is to be
executed. If no points are specified, rolling is done without hesitations. If
no fraction is specified, a roll symbol that starts at the line specifies a
half roll (see description of the Immelman). A roll symbol that crosses the
line specifies a full roll (first figure). The second figure shows the symbol
for 2 points of a 4 point roll (adding up to half a roll) from upright to
inverted flight.


Snap Rolls
----------

Snap or flick rolls also have to be flown normally on a straight line. A snap
roll is similar to a horizontal spin. It is an autorotation with one wing
stalled. In the regular snap, the plane has to be stalled by applying
positive g forces. In an outside snap, the plane is stalled by applying
negative g. In both cases rudder is then used to start autorotation just like
in a spin.


Barrel Roll
-----------

The Barrel Roll is a not competition maneuver. I The barrel roll is a
combination between a loop and a roll. You complete one loop while completing
one roll at the same time. The flight path during a barrel roll has the shape
of a horizontal cork screw. Imagine a big barrel, with the airplanes wheels
rolling along the inside of the barrel in a cork screw path. During a barrel
roll, the pilot experiences always positive G's. The maximum is about 2.5 to
3 G, the minimum about 0.5 G.


Turn-around maneuvers
---------------------

There was a confusion about the difference between a wingover and a hammerhead
turn on the rec.aviation.* newsgroups a while ago. Here is a description of
the two maneuvers.

Wing Over
---------

The Wing-Over is a competition maneuver in glider aerobatics. You pull up and
at the same time bank the plane. When the bank increases past 45 degrees, the
nose will start to drop while the bank keeps increasing and the plane keeps
turning. Halfway through the maneuver, the plane has turned 90 degrees, the
fuselage is level with the horizon and the bank is 90 degrees. The plane is
above the original flight path. The nose then keeps dropping below the
horizon and the plane keeps turning, while the bank is shallowed. When the
bank drops below 45 degrees, the nose is pulled up towards the horizon and the
plane reaches horizontal flight with wings level after 180 degrees of turn.
At the completion of the maneuver, the plane is at the same altitude as on
entry and flying in the opposite direction.


Hammerhead
----------

It starts with a quarter loop into a vertical climb. When the plane stops
climbing, it pivots around its vertical axis (which is now horizontal).The
nose moves in a vertical circle from pointing up through the horizon to
pointing down. After moving vertically down to pick up speed again, the
maneuver is finished with the last quarter of a loop to horizontal flight.
This figure can have optionally rolls on both the up-line and the down-line.

The quarter loop is flown just like the first part of a loop. When the plane
is vertical, the elevator backpressure is released completely. During the
vertical line up, some right aileron and right rudder is needed to maintain
the vertical attitude because of the engine torque and p-factor. When the
plane has slowed enough, full rudder initiates the turnaround. It is followed
by right-forward stick (right aileron and forward elevator) to keep the plane
from torquing off. The pivot is stopped with opposite rudder when the nose
points straight down. When the pivot is completed, the ailerons and rudder
are neutralized. Elevator and rudder are used to keep the nose pointing
straight down. The pivot must be completed within one wingspan. Rolls on
the downline require only aileron input if the plane is trimmed correctly.

This maneuver is sometimes called a hammerhead stall. This is not an accurate
name because the airplane never stalls. The airspeed may be very low, close
to zero, but since there is no wingloading during the turn-around, there is
no stall (at zero g wing loading, a wing does not stall). The plane is flying
throughout the maneuver with all the control surfaces effective (although
sometimes only marginally so).

The previous paragraph is true even for gliders that don't have the support of
the propeller slip stream. The missing slip stream makes it much more
difficult to keep some flow over the control surfaces during the turn-around
in a glider.


-------------------------------------------------------------------------------

The Aerobatics Box
==================

The aerobatics box is the area in which aerobatics competitions take place.
The competitor has to stay within the lateral limits of the box and within the
height limits. During competition there are boundary judges in place that
determine when a competitor leaves the box. Boundary infringement penalties
subtracted from the score in such cases. The dimensions of the aerobatics
box are as follows:

Lower limits:
-------------

1500' AGL: Basic and Sportsman Categories
1200' AGL: Intermediate
800' AGL: Advanced
328' (100m) AGL: Unlimited

Upper limits:
-------------

3280' (1000m) AGL: Unlimited
3500' AGL: All Others

Lateral dimensions:
-------------------

3300' x 3300' centered on the judges line.

The lower limits of the box are, for safety reasons, strictly enforced.


-------------------------------------------------------------------------------

Aerobatics Contests
===================

The International Aerobatic Club (IAC) has over 6000 members. Probably about
800 of these are active competition pilots. Competitions are held locally
throughout the US. There are two national competitions, one in August in Fond
du Lac, Wisconsin, and the other in September in Dennison, Texas. In regional
competitions there are usually between 30 and 60 competitors, in the national
competitions there are usually between 100 and 150 competitors. The regional
competitions are3 held on weekends, the national competitions last one week.
There are five categories of aerobatics competition: Basic (the beginners
category), Sportsman, Intermediate, Advanced, and Unlimited.

Every competitor flies three sequences of aerobatics maneuvers, a Known
sequence, a Freestyle and an Unknown. A competition sequence is composed of
set of aerobatic maneuvers selected from a catalog of allowed figures. The
Known sequence is the same for each competitor in a category. It is the same
throughout a competition year, and changes each year. The Freestyle is a
sequence that each competitor designs according to certain rules. The Unknown
is selected by IAC headquarters for each contest. The competitors receive
these Unknowns the day before they fly it and are not allowed to practice the
sequence.

The competition is flown in the aerobatics box (see above). Penalties are
assessed for flying outside the box. The number of points deducted for each
boundary infringement depends on the competition category and is higher in the
higher categories. The most severe penalties are given for violiting the
bottom of the box. For Basic and Sportsman, a violation of the lower altitude
limit zeroes the complete flight. This is designed to enhance the safety of
aerobatics fling by enforcing safe altitudes during a contest.

The flying is judged by judges on the ground. There are specific judging
criteria for each figure. All allowed figures are specified in a catalog.
These aerobatic figures are the same world-wide. Each figure is assigned a
difficulty factor. The final score for each figure is then calculated from
the score that the judges give for each figure (in the range of 0 - 10),
multiplied by the difficulty factor. The total score for a sequence is the sum
of the scores for each figure. To become a judge requires participation in a
judges school and assisting judges during several competitions. Each judge
has to complete a re-validation exam every year and needs to judge a minimum
anumber of competition flights in order to remain on the current list of
judges.


-------------------------------------------------------------------------------

Specific Questions
==================


How do I find an instructor?
============================

The IAC maintains the most comprehensive list of aerobatics schools. If you
have a World Wide Web browser, you can access the list at http://acro.harvard.edu/IAC/schools.html.
It is also periodically published in the IAC magazine, Sport Aerobatics. You
can also call IAC at (414) 426-4800 and ask for a list of local schools. In
addition to names, locations and phone numbers, the IAC list also includes
aircraft types and rates used by each school. Note that inclusion or
exclusion from the list does not constitute any sort of endorsement or
qualification by IAC.

If you don't find what you're looking for on the IAC list, the next step might
be to contact a nearby IAC chapter and ask for recommendations. A list of IAC
chapters is on the World Wide Web at http://acro.harvard.edu/IAC/chapters.html,
or you can call IAC at the number listed above.

Of course, you can always ask around at your local airport, or put out a
request on the rec.aviation newsgroups.

Once you've found a school, check them out! This can't be stressed enough. Get
references from pilots who have taken instruction with them. Find out how
long they've been in business, and how much and what type of aerobatics
experience they have. What kind of a reputation do they have? Are they
self-taught weekend warriors who recently bought an aerobatic airplane, or are
they Unlimited-level competition pilots with 20 years of experience? What kind
of airplanes do they fly? What condition are they in? Have they had any
accidents? Will they rent the airplane to you (solo) after you've completed
the course?


-------------------------------------------------------------------------------

Will I feel sick?
=================

Aerobatics entail forces and visual situations that are new to just about
everyone. Each person will respond differently to these. Typically, on your
first few flights you may feel queasy after some number of maneuvers. With
each flight, your tolerance will build and you will feel a bit better and
better, until you eventually find that you feel perfectly fine at the end of a
flight. Don't let the initial discomfort discourage you. It's natural, and
the end result is well worth it! The more often you practice, the higher your
tolerance will become.

There are a few ways to minimize the discomfort. The first is to know when to
quit. Once you start feeling queasy, flying one or two more maneuvers is a
great way to get yourself sick. Instead, take the controls. This will help
take your mind off of how you're feeling, and will also help your brain
resolve what it's feeling with what it's seeing. Fly straight and level for a
few minutes. Open the vents wide, and keep your eyes looking outside the
cockpit. If you continue to feel sick, you may want to think about landing.

You'll probably also find that when you fly the maneuvers yourself, you won't
feel bad as quickly as if someone else (i.e.- your instructor) is flying.
This is probably because when you're handling the controls, you have a better
idea of what to expect. Seating position is also a factor. For example,
people seem to do better in the front seat of a Decathlon than in the rear.


-------------------------------------------------------------------------------

Can I do acrobatics in a non-Aerobat C-152?
===========================================

Sure, you *can*. HOWEVER: If the maneuvers are not listed as approved in the
Pilot's Operating Handbook, you have done something illegal (and quite stupid
to boot, since it would be quite dangerous).

The changes made to the C-150 & C-152 are not very visible, but are extensive.
Cessna was worried about people doing aerobatics in the non-aerobatic
version, so the original paint jobs given the aerobatic versions were quite
distinctive.

What might confuse things a bit for the uninformed is the appearance of a
"normal" airplane doing aerobatics at a local airshow. An experienced acro
pilot should be able to put on a decent aerobatic show in many of the
"standard" category aircraft. There are a couple of problems with this,
though. THERE IS NO ROOM FOR ERROR! Aerobatic category ships have a strength
reserve for the maneuvers for which they are approved. For example, even a
low power/weight craft should be able to do a nice loop and not exceed +3 G's.
A normal category plane is certificated to +3.5, aerobatic to +6. A Bob
Hoover can do it safely, you can't. The other problem is, if you do maneuvers
outside what's listed in the POH, you now have an experimental airplane.
Hoover's Shrike and other "normal" category airplanes on the airshow circuit,
have been re-certificated under Experimental-Airshow/Exhibition.


-------------------------------------------------------------------------------

Do I have to wear a parachute when I do aerobatics?
================================================== =

Wearing parachutes for aerobatics flying is regulated in FAR 91.307. It
specifies that whenever you carry a passenger, you may not exceed 60 degrees
of bank or 30 degrees of pitch up or pitch down unless both occupants wear an
approved parachute. This means that you do not have to wear a parachute when
you fly alone. It does not say anything about aerobatics, it just specifies
the bank and pitch limits. So any maneuver that exceeds these limits falls
under this rule and requires you and your passenger to wear a parachute.
-------------------------------------------------------------------------------

How safe is aerobatics?
=======================

Many (most?) people contemplating getting involved in aerobatics feel a bit
apprehensive at first. By it's very nature, aerobatics involves risks that
are not involved in non-aerobatic flight. But as with most anything else in
aviation, it is only as safe or dangerous as the pilot makes it. Discipline,
planning, common sense, and knowledge are basic prerequisites to safety.
Aerobatics can be quite safe if certain safety rules are followed religiously.
Examples include:

* Get proper training, especially in all types of spins and botched
maneuvers.
* Fly at a safe and conservative altitude.
* Know your equipment and yourself, and keep both well maintained.
* Don't overstress the airplane (and never fly aerobatics in non-
aerobatic aircraft).
* Always perform a proper, thorough aerobatic preflight.
* Set and observe strict personal limits (altitude, g-limits, flight
duration, health, etc).
* Stay current and take recurrency check rides.
* Don't run out of fuel! (should be obvious, but it happens a lot)
* Stay clear of conflicting traffic, either with regular clearing turns or
an observer on the ground.
* Know how to handle emergency situations.
* Always leave yourself a way out.
* Always wear a parachute. Know how to bail out and use it.
* Learn by others' mistakes, not your own.

An example of how safe aerobatics can be is that there has never been a
fatality in IAC-sanctioned competition, where strict safety rules are always
followed.

The penalty for ignoring safety procedures can be quite high. A review of
NTSB accident data for the 8KCAB Decathlon (probably the most common aerobatic
trainer) from 1983 through 1993 shows 14 accidents related to aerobatics.
Eight of them involved attempting aerobatics at low altitudes. One was caused
by lack of training, one by lots of unsecured loose baggage (ie- lawn chairs
and more) floating around the cockpit, and one by structural failure. Causes
of the remaining three are less clear from the reports, but two appear to have
been due to low level aerobatics, and the third by failure to recover from a
spin. So, of the 14 accidents in ten years, all but one (structural failure)
could have been prevented by following the few simple rules listed above. The
structural failure was in a known problem area and *might* have been avoidable
if the pilot was more familiar with his equipment.

With higher performance aircraft and more advanced aerobatics, there are
additional risks. The airplanes are less forgiving, the forces on plane and
pilot are higher, some of the equipment is newer and less proven, and much of
the flying is done at lower altitudes. Also as skills and experience build,
complacency and bad habits can begin to creep into the picture. By the time
you get to this level, you won't need this FAQ to learn how to manage these
risks.

One thing is for certain. Once you have learned to fly aerobatics, your
increased knowledge will make all the rest of your flying safer.


-------------------------------------------------------------------------------

More Questions
==============

If you want to answer one of these so I can include it in this FAQ, please
send me something.

- What is aerobatics?
- Why do people learn aerobatics?
- How do I learn aerobatics?
- What type of plane should I learn in?
- How do I get involved in competition?
- What is the Aresti system, and how do I read the symbols?


----------------------------------------------------
Access provided by:
Guenther Eichhorn | gei at cfa.harvard.edu
Smithsonian Astrophysical Observatory, Cambridge, MA
CPL,ASMELS,Glider,LBH,IA,CFI | Pitts S-2A: N1GE
DC-3 type rating | Flying is the Pitts
See: http://acro.harvard.edu/ACRO
and: http://acro.harvard.edu/SOARING
--
---------------------------------------------------
Dr. Guenther Eichhorn |
ADS Project Scientist | Phone: 617-495-7260
http://ads.harvard.edu | Fax: 617-496-7700