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gmcjetpilot
Joined: 04 Nov 2006
Posts: 170
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 Posted: Sat Jan 20, 2007 3:16 pm Post subject: Aerobatics, just say NO to inverted Spins! HOW TO PART III |
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(LONG POST)
Dear RV group:
How many RV's have crashed from an inverted spin?
I know inverted (death) spin, has some emotional
connotation, but the fear is ignorance squelched w/ facts.
I got a few responses from my How to do a Roll and
Loop article, several complimentary and one just plan
odd and wrong, so let me clarify a few things:
Number one, acro in a RV is not F-16, Pitts or F-14
acro. I think some folks have watched top gun too
much (the inverted spin scene where "Goose" dies).
RV's are stable and WANT to fly right side up.
I am not going to explain basic aerodynamics,
but due to wing dihedral, design (NACA 23013.5) and
pitch, yaw, roll controls and stability with proper CG,
RV's are stable in any attitude. RV's also resist spinning
unless intentionally spun.
Spins: RV's don't like to even spin right side up,
much less inverted. You have to hold controls
aggressively and keep and keep them there to the
control stops. Once you release or neutralize the
controls it will stop spinning in most cases. Some RV's
(power on, to the left, fully developed +3 turn stall)
might need a touch of anti-spin rudder. By all means be
familiar will basic stall / spin recovery.
INVERTED SPIN: I have not tried it in a RV
and doubt you can even do it intentionally, due to lack
of elevator authority and the basic design of the plane.
Again dihedral, airfoil design and CG (which is still the
same inverter or right side up) makes the plane want to
recover naturally in a nose down attitude right side up.
The dihedral will naturally make the plane roll upright.
Also to spin you need a yaw input or forces, ie rudder.
Leave the rudder alone (as I said before) for beginners
in rolls and loops.
*G LOAD (The MAGIC of 3 Gee's)
G load: IF YOU ARE PULLING 4.5 g's to do acro in a
RV you are doing it wrong and its not wise. The drag
(induced) is proportional to the lift coefficient. As you
pull on the stick and load up the wing you increase
drag, and drag gets exponentially greater. When you
plot lift v drag you will see the curve gets real steep.
Over 3 g's is a waste and needlessly bleeds energy
(speed) and is like throwing the anchor out. Don't do it
unless you want to slow down or in worst case scenario
break the airframe (3.5 g's OK fine, +4 g's no not needed).
*SPEED
Speed for loops: Look for a loop if you want to do 200
mph and pull 6 g's, fine. However I can loop almost
ANY plane at 140 mph, Cessna aerobatic for example
(of course you have to dive first). It has more drag and
less power and about the same weight as an RV. It can
loop at 130-140 mph. Stearman? Same thing. The
recommend RV loop entry speed is 140-160 mph. You
can do it faster. Some guy wrote me and say he can't
loop at less than 150kt (173mph) & pulling 4.5g's! OH
MY GOSH, that is dangerous for a beginner's.
135-140 mph is "Va", maneuver speed. Flying
closer to Va is safer. Even if you mess up and pull too
hard, you will not break the plane, it will stall first.
To stall is NOT DEATH. It is a normal maneuver you
should have mastered as a 10-20 hour private pilot
student. Now breaking the wing off? I don't have a
recovery for that. Flying fast and pulling more G's is
counter productive and gives less margin (structural
and airspeed limits).
If you pull less G's you lose (need) less speed!!!
Yes you need speed for any vertical maneuver but
going faster to overcome poor technique or lack of
understanding is not good. RV's have low drag and
great power/weight. If a Cessna C152 can do it a
RV can.
IF YOU ARE AFRAID OF STALLS OR NOT
PROFICIENT IN ALL KINDS OF STALLS:
recognizing impending stall, recovery from stalls:
straight, turns, accelerated, power on climb, power off
climb, with minimal loss of altitude and effort, THAN
DON'T DO AEROBATICS. It does not mean you can't
learn and conquer stalls but you will need an instructor,
say in an Aerobat or Citabria.
I thought I made that clear, but some folks have
been spreading fear about stalls. I would rather a guy
stall at 3,000 feet and recover than pull the wings OFF.
For beginners work at lower entry speeds 140-160 mph
and use 3 g's as a basic limit for your maneuvers. At
high speed and g's you are very close to the structural
and speed limits, especially if you mess up and get
nose down with power on.
Some folks are worried about stalls and inverted spins.
How many inverted stall spin accidents have you heard
of in RV's? Pitts special? (several) RV's? (none); Now
may be that its the pilot, plane or may be the Pitts is
flown in aggressive acro more? Pitts can have
symmetric airfoil wings and they have very little roll
stability and no dihedral.
You are more likely to get killed from a stall or
stall-spin in the traffic pattern (from pilot miss handling
the controls and not maintaining airspeed) than doing a
loop at a safe altitude. Now I am not saying everyone
loop your RV. Truth be told there are some pilots that
may be should be flying at all, straight and level much
less trying acro. Please read what I wrote
before and all the cautions and caveats.
IF YOU STALL INVERTED, THE RV WILL
NOT SNAP INTO AN INVERTED SPIN. In fact
if you do nothing the nose will just drop and it will just
roll/dish-out and end up the way it was designed to fly,
nose down probably flying wings level straight ahead
or in a bank / spiral. A simple recovery is all that is
needed. Even in you stalled upside down, and pushed
the stick forward and added rudder it would probably
snap roll. If you just release the controls it would fly
again. You really have to put in PRO stall and PRO spin
(yaw) controls to get a RV to stall and spin. However
even a stall from inverted with rudder kicked in the
spin would likely be up-right, not inverted.
It would take talent to do an inverted spin in a RV.
*FLOATING?
(i.e., less than +1g to plus side of zero-g)
The fear of having less than 1 g over the top a loop, so
called FLOATING, from one guy that wrote me, who
likes to enter a loop at very high speeds and G's scares
me. A FULL ONE G is ridiculous at the top of a loop.
Since gravity is a negative 1 g at that point, than you
need to still be accelerating down (at) +2 g's vertical pitch.
That is a very tight loop and really what I call a "Whiffer-
Dale" (any maneuver that is really not a recognized
aerobatic maneuver) a kind of a vertical climb with a
hook on the end and a dive and level off, not a loop.
Lots of g's and not necessary or elegant.
Than he said some stuff about a perfect loop is not for
beginners. I have no idea what he is talking about. One
my technique is far from the perfect loop, just a safe
loop. Second I have been flying for over 20 years and
doing acro for at least 15 years, I still can't do a perfect
loop.
The RV fly's fine on +1 g, +1/2 g, +1/10th g. You do not
need inverted systems to fly around "light" in the seat.
With an inverted systems great, but the RV design
(wing, dihedral, CG) likes to fly right side-up. Intentional
inverted maneuver in most planes are hard, especially
the RV. Now planes with no dihedral and symmetric
airfoils are easy to fly upside down. That is not the RV. I
have several RV buddies with inverted oil/fuel. When
they are upside down and the wing needs a lot of neg
AOA to fly, very nose up attitude in level -1g inverted
flight. RV's don't like to fly negative G's.
Also the stall speed of a RV at acro weight is what?
50-55 mph at 1g. At 1/2 g stall speed will be way lower.
At zero g's it will be basically nothing. YOU WILL NOT
STALL,SPIN AND DIE IF YOU LOOP AT 140-160 mph,
IF YOU DON'T PULL TOO MANY G's and BLEED ALL
YOUR ENERGY OFF (as some recommend).
RV's also because of the great wing don't do snap rolls
well because the wing wants to fly. You have to put stall
strips on it, which raises the stall speed. RV's are good
basic fun acro planes but not serious hard core acro
planes. The actual problem with RV's is they acro TOO
easily and make pilots think they are better than they
are. Many acro planes are not as forgiving, demanding
more skill and technique to properly loop and roll around
the sky. Basic acro the RV is the best there is.
Good Luck, again because of people who wrote me and
said scary things who think they know, is the reason I
wrote the article. As I stated you need to be competent
and confident in you airmanship before undergoing
acro. However acro is not inherently dangerous. The
plane fly's fine in all attitudes. However professional
airshow and competition pilots that are dedicated to
acro do crash from time to time. Flying has risk folks.
Do ignore the alarmist's. However if you have GOOD basic
skills and follow GOOD basic common sense than acro
in RV's is very safe, but of course NOTHING is without
risk. I suggest you find an OLD back issue of the
RVator and Van's two or three part article on doing
ACRO. It basically was from the same point of view,
you should get dual BUT I know you are going to do it,
so at least have some advice. The problem is getting dual
anything in RV's, much less dual acro in a RV. You can
go up in a Pitts and have a guy loop, roll and show off and
it will not help you fly the RV. The RV is not a Pitts. It
would probably be better to go up in a Cessna Aerobat
or Citabria and learn some basics if you can't get RV
dual. Also many RV's are too heavy to for dual acro.
*Mo Knowledge:
Books to read:
"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
Check out some of the aerobatic clubs like EAA's IAC
http://www.iac.org/
"A person who teaches himself to do aerobatics has a
fool for an instructor". Author unknown
However I know some are going to do it any way. I also
know there are a few out there that are doing and have
been doing acro who don't have a clue and they scare me.
I hope the info is help full.
*Mo Practice
The information I presented is basic outline. There is
NO FAR that prohibits you from doing aerobatics with
out an endorsement or training as long as you are off
the airways and not too low or close to persons, places
and things. Of course that does not mean you will not
get the catch all of reckless and careless operation. I
personally am a very conservative pilot, former CFI-II-MEI
with 1000's of hours of dual given and now airline pilot.
I have looped and rolled many planes (not airliners of
course) and its fun. Just use common sense and KNOW
THY SELF. Training is BEST but many have lost their
acro virginity solo.
*G TOLERANCE
To get use to G's I highly recommend 70 degree
banks is about 3 g' (level turn). 60 degree banks are
only 2 g's. You will need to add LOTS of POWER for 70
degrees. Again respect the structural and speed limits
and do not enter at higher than Va. Va is your safe speed.
Also the g's will acclimate you. Some people go cationic
or freeze when they see the sky and earth flip or their
body experiences more than 1.5 g's.
*Hate Mail (not you Bob)
One guy wrote me and scolded me about how dare
I teach or post on the web how to do aerobatics,
"beginners don't have the touch or feel". That is
either pure ignorance or pure ego, like its so
difficult and only he can do it. Please again read all
my previous caveats. I recommend not doing acro
with passengers, and do acro over remote areas.
Why? Well if you kill your self than you will not
hurt anyone else. Hate to be grim but Aerobatic
accidents are from many reasons but mostly
pilots doing them 1) too low and 2) with out
knowledge and 3) no skill. I have addressed all three.
RULES: safe altitude, respect limits
SKILL: Practice the prerequisites to acro maneuver's
KNOWLEDGE: Read and ask questions
YOU CAN LEARN RULES,
YOU CAN GET KNOWLEDGE,
BUT THE ACRO SKILL WILL NOT COME UNLESS
YOU PRACTICE AND ACTUALLY DO IT. YOU
CAN'T LEARN WITH OUT EXPERIENCING IT.
Many times the practice or initial acro experience
comes solo and is self taught, but if I explain how to
do an ILS instrument approach I don't expect a
VFR pilot to launch into solid IMC. Same with
aerobatics, however a skilled private pilot should
have the basic tool kit of skills and knowledge to
understand aerobatics. You never can have enough
info, skill or knowledge, but there is a first time for
every thing. Ideally when you lose your roll or loop
virginity you have some one there to back you up.
Can I roll on takeoff. Yes, but I don't because I
know my chance of death go up 10,000 fold. Do I
fall out of acro maneuvers? Yes but not basic ones
like I described previously, aileron roll and loop.
Respect the airplane's limits and your personal
limits. Acro is not for everyone.
Fly Safe, George ATP B73/75/76, CFI-II-MEI, RV-4, RV-7
Now that's room service! Choose from over 150,000 hotels
in 45,000 destinations on Yahoo! Travel to find your fit. [quote][b]
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garrys(at)tampabay.rr.com
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| Posted: Sat Jan 20, 2007 4:50 pm Post subject: Aerobatics, just say NO to inverted Spins! HOW TO PART III |
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Great post by George. Very informative. Two questions however........if one does not have a G meter, is there any other way to do rolls and loops? Second, George says don't do aerobatics with a passenger. Really? How else can I show off my new skills?
Garry Stout
RV7A in progress
Tampa Florida
[quote] ---
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n5lp(at)warpdriveonline.c
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| Posted: Sat Jan 20, 2007 4:53 pm Post subject: Aerobatics, just say NO to inverted Spins! HOW TO PART III |
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On Jan 20, 2007, at 4:15 PM, <gmcjetpilot(at)yahoo.com> wrote:
| Quote: | ...
RV's also because of the great wing don't do snap rolls
well because the wing wants to fly. You have to put stall
strips on it, which raises the stall speed....
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Ok, George, you've got me curious about how the RVs you have flown
snap. I have a 6 with an O-360 and fixed Sensenich and it seems to
snap just fine (I have only done it solo).
I have never flown an all out aerobatic plane, so maybe I don't know
what is supposed to happen. At the recommended entry speed I put in
full elevator and rudder and bam, it goes around smartly. I have
difficulty timing the recovery so it happens at exactly wings level,
but I have that same problem with Citabrias.
Larry Pardue
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