Spins, Citabria 7ECA

Bartman

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I'm new to this, my Citabria is the first plane I've had access to on a regular enough basis to learn aerobatics. Hopefully we'll hear from others that have either been exposed to more formal training or more stick time in departures from straight and level.

My approach was to start with spins since spins are what can happen when some of the other maneuvers get botched. For the Primary category, there is a 1 1/2 turn spin.

From a judge's perspective, the aircraft must clearly stall before beginning rotation into the spin, the spin must be stopped precisely at 180 degrees from the entrance heading, the vertical downline must be held momentarily to define the vertical line, and the exit must be to a horizontal level line.

The Citabria and Decathlon both share a common trait, the plane must be aggressively stalled at the last moment using the last bit of energy in order for it to fall into a tight spin. Any amount of mushing through the stall or no clean stall and it will nose over and yaw/roll into a spiraling descent.

For the exit, I've found full opposite rudder will stop the spin on heading and it takes only a bit of down elevator to establish a vertical downline but you should work to looking out your left window to set pitch using the wingtip and horizon. It took me a lot of spins before I could calmly point the plane straight down and then glance away from the ground rushing up at me to look at the wingtip! lol

A clean exit to a horizontal line will pull about 3 1/2 G's and the throttle should be pulled back as necessary to keep from over-revving the engine.

Keep in mind, too much forward stick in the recovery could cause the plane to pitch over into an inverted spin so learn the recovery with neutral stick and work your way up to a vertical exit with any down elevator pressure.

What did I leave out?
 
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Big Ed

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Always practice over a linear terrain feature such as a long straight road. Use that to maintain alignment with the box. Contest success is very much about alignment. You get dinged hard for being off heading.

A few additional tips on competition spins:
  • Keep it coordinated, straight, and level as speed decays. A bit nose high will help the break.
  • Firmly pull stick to the rear when it reaches about 3/4 deflection, and the nose should break cleanly.
  • AlwaysSpin left when you can, so you are not fighting torque and gyroscopic precession. Less critical for Citabria than heavy prop aircraft like Super D.
  • Don't relax pro-spin controls even slightly, or you will fall out of the spin. Pull/kick to the control stops and hold it there.
  • Opposite rudder 1/4 to 1/3 turn prior to desired heading to slow rotation. How much prior will depend on how developed the spin is.
  • Pop stick forward to neutral on heading, while simultaneously centering rudder.
  • Continue pushing forward and look left at gauge or wingtip to set vertical line.
  • If you have a CS prop, add full power in the vertical line.
  • If you are off heading, gradually correct with roll during vertical line. Ensure wings are perpendicular to desired heading before pull out.
  • Once you set the vertical line, count "one thousand" and then pull 4G to level.
  • If you are approaching the yellow arc on pullout, the correct response is more pull, not less.
The trickiest part of competition spins is getting used to different nose attitudes in recovery, which can impact the timing of your anti-spin rudder and your on-heading stick pop. Until the spin stabilizes, at about 3 rotations, the nose oscillates up and down. So a 1 turn spin and a 1+1/4 turn spin can have quite different attitudes, and react differently to anti-spin rudder. There's no trick here, just awareness and practice.

Competition spins are a GREAT exercise for building your confidence, and IMO one of the best benefits of acro. Every pilot is afraid of spinning when they start flying, which means that every pilot is worried about stalls, and thus nervous about maximum performance maneuvers and MCA. Once you do 30 or 40 spins and realize how benign they are, and how much control you have over recovery, the fear goes away and they become fun. The unknown becomes known, which allows you to fly stalls and MCA without apprehension.
 
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Bartman

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Ed,

Thanks for the reply! All good info!

I thought the same thing about always spinning left but was told to spin into the wind (if the wind has a crosswind component) and that concerns with torque and gyroscopic forces are unfounded since the engine is at idle in the approach to the spin and during it. But I agree with what you said about pinning the stick aft and the rudder hard to one side in the spin until it's time to move them for the recovery.

It's also worth mentioning if your tailwheel isn't well greased it may get stuck left or right after a spin causing the plane to yaw for no reason after the recovery. When it happens I'll typically slow down, get the nose high and then waggle the rudder which usually centers the tailwheel.
 

Big Ed

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I thought the same thing about always spinning left but was told to spin into the wind (if the wind has a crosswind component) and that concerns with torque and gyroscopic forces are unfounded since the engine is at idle in the approach to the spin and during it.
This discussion mixes together two separate issues: aerodynamics and box positioning.

From an aerodynamic perspective, as we all know, the aircraft does not feel wind. Wind direction only matters in reference to the ground. Wind has no impact on how the aircraft breaks into a spin or recovers.

I have been taught that our aircraft break more cleanly and consistently to the left. In order to spin, an aircraft must roll and yaw in the same direction. Even at idle there is some amount of left roll tendency imparted in reaction to the force of the prop pushing against the air, some amount of left yaw imparted by the slipstream, and some amount of left yaw felt by gyroscopic precession of the prop disc in response to the nose dropping. All of these forces favor a spin to the left. I cannot say for certain this is the case with all aircraft, but in my experience with several Decathlons it seemed to be the case. I certainly concede that an aircraft should spin in either direction and that you should be comfortable doing that.

What muddies the discussion is box positioning, which is all about the wind. Spins are frequently used as a wind correction maneuver in sequences. If there is a substantial crosswind component, the aircraft drifts sideways in the box. By the latter half of the sequence, the aircraft will no longer be centered. Most sequences include a 90 change of axis maneuver about 2/3 thru the sequence to reposition the aircraft. A 1+1/4 turn spin works well for this purpose. In that instance, you must rotate into the wind to accomplish the correction. I have seen pilots go out of the box and get DQ because they spun away from the wind and it carried them out of the box before they could finish the reversal maneuver.

However ... if it were a 3/4 spin or a 1+3/4 spin, you would turn AWAY from the wind. Additionally if it were a single turn or 1+1/2 turn spin like the current primary sequence, then wind is irrelevant to the direction. In that instance, I would advocate going in the direction that the aircraft more readily spins. I think that is to the left, but that could just be superstition on my part, like wearing a rally cap.
 
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Hiperbiper

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My only input to this discussion concerning spins (or any IAC competition maneuver) is simple:
Learn the maneuver itself before trying to fit it into a box or routine. Go do 15-20 spins just to get used to the sight picture, sounds and control use. Ditto for rolls or loops or hammerheads...see what works and what doesn't.
Get used to making the plane do what you want it to using all the controls in concert. Get comfortable with G, get comfortable with a windscreen full of planet coming your direction occasionally, get comfortable being thrown around in the belts...
Have FUN getting comfortable with all that stuff.
Getting comfortable doing acro is the learning of a new skill set.
Learning how to use your new-found skills in an imaginary box in front of judges is merely polishing your skills to an acceptable level...
You'll be surprised at all you can learn having a blast boring holes in the sky on a sunny afternoon without a cue card on the panel...
JMPO
Chris
 

volvo164

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I'll have to pay more attention, but so far found no difference in left or right spins in my 115HP 7ECA. Perhaps the lower HP makes it less obvious - now I need to test it out more. For some reason my instructor didn't mention a preferred direction, and I've been mostly spinning to the right! Had no issues with a clean break - as the plane slows, I pull the stick correspondingly faster to full back, doesn't need to be aggressive just swift, first sign of stall full right rudder, and there she goes. On occasion I had issues with my opposite foot falling off the rudder, which for me are just bars as I have heel brakes. My recovery is as specified by Ed: opposite rudder, stick to neutral once rotation stops, and once I'm out of the spin set the vertical down with further forward stick. Maybe it's not as fluid as what judges like? I've been reluctant to recover straight into vertical dive, exactly to avoid an accidental inverted spin.
 

Big Ed

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I don't know the judging criteria, but I do it the same way as you: break the spin, break the stall, set the dive.

I would not worry too much about an accidental inverted spin. You would really, really have to overcontrol it. It takes a LOT of forward stick to stall or spin inverted in these aircraft. In my Decathlon I have to grab the frame and do an abdominal crunch to get it far enough forward, and the slightest relaxing of the stick breaks it. As long as your stick input is reasonably smooth and not abrupt, I don't see how it could happen. Also, you should be neutralizing rudder at the same time you move the stick forward, so even if you found a way to stall inverted, it should not progress into a spin.

But of course I'm not experienced in your airplane, which has a different airfoil than mine. You should definitely get some inverted spin training so you know how to recognize and recover, if you have not already. Inverted spins are a wild ride.

Transitions from upright to inverted spins are an issue in the Pitts special and similar aircraft, for 2 reasons. First, they have huge control surfaces and control authority. Second, they have very short bodies and wingspans, which leads to an extremely high rate of rotation and very little difference in pitch between upright and inverted. A spinning Pitts rotates at 720 degrees per second. Multiple Pitts fatalities have occurred from the same scenario: the pilot enters an upright spin, and applies anti-spin control inputs, which immediately breaks the spin and puts the aircraft into an inverted spin in the opposite direction. Visually there is very little difference and so the pilot does not recognize what happened, and continues holding anti-spin inputs for an upright spin and wondering why it won't stop. That is a topic of great concern in that community and a strong consensus has emerged on the requirement for 5-10 hours of type-specific training as an absolute minimum.
 

volvo164

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So after multiple tests - at least in my 7ECA, the direction makes no difference. I think the torque at idle with that skinny prop on the 7ECA makes little difference, technique (timing) is a bigger factor.
 

VaporGlobalAviation

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I’ve been having issues getting a proper (non-comp) spin as well in an ECA. Mostly 50/50 spin vs spiral. I’ve noticed that power just above 1000, like 12-1300 helps with getting it right. But as soon as I pull to idle, it pops put… Not sure… maybe just a super stable platform.
 

Big Ed

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Now that I understand the control system better, I would recommend checking to verify you are getting full upward elevator deflection. Sit in the seat, pull the stick aft, and have someone confirm the stop bolt on the elevator horn is contacting the stop. If not, use the elevator cable turnbuckles to adjust the stick travel.
 

VaporGlobalAviation

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Now that I understand the control system better, I would recommend checking to verify you are getting full upward elevator deflection. Sit in the seat, pull the stick aft, and have someone confirm the stop bolt on the elevator horn is contacting the stop. If not, use the elevator cable turnbuckles to adjust the stick travel.

YES! After today’s flight, I was planning on doing this as well. Just making sure that it was not poor technique. I am pretty sure I am hitting the stop, the stick stops with space between the seat and stick when I do my Flight Control Check during preflight (me out of the seat) and during run up (me in the seat).
 

Bob Turner

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In the olden days a Sportsman spin was 3/4 turn. Period. Grades were how crisply you got the break, how vertical your down line was, and whether you pulled out heading directly for the next maneuver. They told me I got good points for my down lines.

Hard to believe three turn spins are part of modern contest sequences.
 

Big Ed

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Hard to believe three turn spins are part of modern contest sequences.
They are not. That would be a very poorly designed sequence. In addition to throwing away a ton of energy, it would probably bust the altitude floor.

The highest spin would be a 1.5 to reverse direction, as is the case with this year's Sportsman.

Used to be common to use a 1.25 as a wind correction maneuver. I liked those.
 

Hiperbiper

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Now that I understand the control system better, I would recommend checking to verify you are getting full upward elevator deflection. Sit in the seat, pull the stick aft, and have someone confirm the stop bolt on the elevator horn is contacting the stop. If not, use the elevator cable turnbuckles to adjust the stick travel.
You might also want to check for proper throw when the surface is against to stop. A simple digital cube type level zeroed on the stab then measure the up and down angles on the elevator.
Adjust the stop as required.
Chris
 

Big Ed

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You might also want to check for proper throw when the surface is against to stop. A simple digital cube type level zeroed on the stab then measure the up and down angles on the elevator.
Adjust the stop as required.
Chris
Related question ... what is the correct configuration of bolt and nuts on the stops? Not clear from the parts diagram. I just have the bolts inserted in the horn with heads toward the stop, and a stop nut on the other end. Is there a way to set it up to be adjustable by turning the bolt, or is it necessary to stack washers under the head to get the desired stop?
 

Hiperbiper

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Quite frankly I've seen a multitude of stackups for the up and down stops. I used the bolt head as the bumper with the required number of washers and a lock nut. But I've seen other configurations using spacers, dual nuts, ect.
Chris
 

Big Ed

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Quite frankly I've seen a multitude of stackups for the up and down stops. I used the bolt head as the bumper with the required number of washers and a lock nut. But I've seen other configurations using spacers, dual nuts, ect.
Chris
I suppose not really necessary to adjust once you get it set up with proper travel, so stacked washers should be sufficient.
 

VaporGlobalAviation

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So, finally determined the left rudder stop is limiting travel enough to only get one spin before mushing into a spiral going left. Spinning to the right is perfect. Some simple measurements confirmed. Will be working exact measurements via A&P prior to making any adjustment to the stop. Service manual says to remove material from the stop. These old birds crack me up sometimes.
 

VaporGlobalAviation

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Went and flew with the adjusted rudder stop. I now get one full spin to a mushy spiral. Someone mentioned that the wing dihedral may be off…? The airplane flys like a dart with the exception of the left spin. So, not sure about having the dihedral adjusted…