Aerobatics in the 7ECA

[Bob Turner]

Why am I the only guy who thinks a slow roll is done from level flight, and includes a negative G loading? If you dive for a roll, then pitch up and add aileron, isn't that an aileron roll?
I get so confused!

 

[volvo164]

Why am I the only guy who thinks a slow roll is done from level flight, and includes a negative G loading? If you dive for a roll, then pitch up and add aileron, isn't that an aileron roll?
I get so confused!

The original Champion / Bellanca manual lists 120mph as entry speed - and well - the 7ECA doesn't go 120mph! I've struggled with the slow roll with 2 up (with instructor) without spades, although doing it solo was much easier. I would run out of energy coming back around ending up in a shallow dive. Hoping the spades will allow me to just snap into it faster, as well as ensure I hold full aileron all the way through. Anyway, given the challenges at 120mph, have not tried it at the 100mph cruise speed, hence the dive to 120mph, then level, then roll (no pitch up).

 

[volvo164]

I'm spoiled, have never flown acro with fixed pitch. Worrying about RPM would stress me out. One day I would love to get a Pitts S1S, so I maybe I'll learn then.

@volvo164 Where did you get the spades?

ACA for the spades - I have ACA metal wings.
Yes, the RPM management is a PITA - at least initially. I had unintentionally exceeded red line a couple of times (but within Lycoming limits). My instructor never flew fixed pitch acro, so that didn't help. I'm trying to now establish a pattern / process that will get me through the routines without worrying about red line - knowing it won't be optimal going up or down. The mechanical tach doesn't help (too slow to react), plus there's a delay with the prop speeding up as well. So if you're in the dive, reach 140mph, level out, glance at the rpm, it's 2800, then as you pull up into a loop or whatever and gance back at the RPM, you're now at 3000. Not sure if it's the combined delay of the tach, prop, or if the G acceleration further spinning the prop (or all added together). So I learned that the RPM needs to be well under red line at the level out - same for coming out from a dive. Also learned not to feed power back in so quick on that pull up. The Bellanca manual (that's found on this forum) instructs to add power for the loop, but actually it's not necessary. The manual also states to pull power to idle on the descent (from loop, etc.) but I'm inclined to not cycle the engine full power / idle / full power so much, and I want to have the right entry speed for the next maneuver as well, so I'm also trying to identify the right power setting up on top. I'm thinking if I set this right, I won't have to worry about adjusting the power for the next maneuver at the bottom (aiming to end up at the right airspeed and RPM from the pull out).

 

[Big Ed]

It's not so much the speed and roll rate that make it hard to fly slow rolls cleanly. It is your flat bottomed wing.

The dive is caused by not keeping the nose high enough thru knife edges and inverted. Little drops at different points of the roll add up, and once the nose drops you are not getting it back.

A flat bottomed airfoil needs a very high angle of attack to fly inverted. It needs the same attitude when rolling thru inverted in a slow roll.

There is nothing inherently wrong with pitching the nose up some at the start of the roll. In fact, I'd say it is a necessity in your aircraft. From a judging perspective, only pitch up enough to put the nose in the attitude you want to hold thru inverted, and don't do it long enough to visibly affect the flight path. If you blend it into the first 8th of the roll, it will look clean. Enough.

I maintain that a slow roll can be done at any speed that does not result in a stall. The Split S and Immelman both include a half roll at 85 mph. You have to be less aggressive with control inputs to avoid an accelerated stall, and you aren't going to get much lift in knife edge flight, so you will need even more AoA. But it can be done, and is useful to learn. Worst case, you stall and fall out, so have plenty of altitude.

I would be hesitant to do a lot of slow rolling in an aircraft without inverted oil. Maybe it's not a problem, I just don't know enough about engines to say.

Adam Cope, the IAC board test pilot for the known sequences, posted on Facebook yesterday that the reference aircraft for Sportsman is a Citabria with non-inverted systems.

 

[Bob Turner]

Ed and I have the same understanding of slow rolls.

If you are doing aileron rolls, all the spades in the world will not prevent a nose low rollout. You need a tad of forward stick while inverted.

For a slow roll in a Citabria, you need a whole big handful of forward stick while rolling through inverted, and your engine will cough, guaranteed, unless injected.

 

[Big Ed]

If you finish nose low on an aileron roll, then pitch higher before starting the roll. In a Citabria I would use at least 30 degrees, maybe even 45. Pitch up, center controls, then roll. If the nose starts high enough, you won't need anything but aileron and it will be zero G the whole way around. But it's not a scored maneuver so you can do it any way you feel like.

I have never really learned to barrel roll. I can do some random crappy thing with some pitch, roll, and yaw, but it makes no sense and is not consistent. One day I need to play with that. In theory with a proper barrel roll you are 90 degrees to the direction of travel when inverted, no?

 

[volvo164]

If you finish nose low on an aileron roll, then pitch higher before starting the roll. In a Citabria I would use at least 30 degrees, maybe even 45. Pitch up, center controls, then roll. If the nose starts high enough, you won't need anything but aileron and it will be zero G the whole way around. But it's not a scored maneuver so you can do it any way you feel like.

I have never really learned to barrel roll. I can do some random crappy thing with some pitch, roll, and yaw, but it makes no sense and is not consistent. One day I need to play with that. In theory with a proper barrel roll you are 90 degrees to the direction of travel when inverted, no?

This is true for the aileron roll (and indeed 45 pitch up is better). But for the slow roll, in theory you're not supposed to pitch up. Good suggestions by Bob and Ed, to start with a slight pitch up which does help. I have indeed been giving lot of forward stick inverted. This is where the aileron spades will hopefully help - I've found it difficult to keep full aileron in + shove the stick forward inverted, resulting in the roll slowing down while inverted. The engine does sputter, and you hang by the seat belts. Again, single up it was much easier. My understanding (and Champion documentation dictates) that oil is not an issue for momentary negative Gs - the engine will quit way before it runs out of oil, as it indeed has for me when I was hesitating inverted.

 

[Big Ed]

But for the slow roll, in theory you're not supposed to pitch up.

Not necessarily. You are supposed to apply whatever control inputs are necessary at each stage of the roll in order to maintain a straight and level flight path. That is not the same as a level attitude.

Here is what Mike Goulian has to say about it in Basic Aerobatics:

"In training aircraft that have asymmetric wings, such as the Decathlon, pitch up slightly and neutralize controls after establishing the entry speed, but do not allow a climb to develop prior to commencing the roll. The pitch-up helps establish a high angle of attack approaching the inverted position and eases some of the force that will be required to push on the stick to keep the nose sufficiently above the horizon."

 

[ehaecker]

OLD thread but bumping it because I enjoyed the read. As a new 7KCAB owner, this has been good. I did most of my acro training (15 years ago) in an 8KCAB and some in a 7ECA. My current 7KCAB does not have spades, and I find the control harmony to be a bit heavy, even for regular flight. I've got original wings with Milman spars. I was told be ACA that the new spades would work, but need field approval as they're only approved for ACA wings. Anyone here ever dealt with adding spades to wood wings with metal spars? I'd assume spades from a wood wing would bolt right on.

 

[Big Ed]

OLD thread but bumping it because I enjoyed the read. As a new 7KCAB owner, this has been good. I did most of my acro training (15 years ago) in an 8KCAB and some in a 7ECA. My current 7KCAB does not have spades, and I find the control harmony to be a bit heavy, even for regular flight. I've got original wings with Milman spars. I was told be ACA that the new spades would work, but need field approval as they're only approved for ACA wings. Anyone here ever dealt with adding spades to wood wings with metal spars? I'd assume spades from a wood wing would bolt right on.

Sounds like quite the research project. If you could find a set of Olin Pash spades, those were STC'd for the wood wings. If the Melman spar STC does not exclude installation in wings with spades, seems like there might be a legal basis for installation. Not sure, just spit balling.

 

[Big Ed]

I spent some practice time this spring focused on slow rolls for competition. What helped me the most was marking the windshield brace with 2 dots to index the horizon for level upright and inverted flight. To fly a perfect roll, put the lower dot on a fixed object on the horizon, then roll inverted such that the upper dot is on the fixed object.
Basically you visualize a circle with the dots at the 12 and 6 o'clock positions, and then roll that circle on the distant target so that the lowest point of the circle is always on the horizon. That helps to cue when to feed in rudder and elevator, and visualize how much is needed.
When I get my engine back, I'm going to go one step better and draw a circle on the windshield with a grease pencil.

 

[volvo164]

Good idea - although difficult to set up I suppose in a non inverted Citabria. Indeed one challenge is to figure out by experimentation where to place the target in the windshield as you roll around. For me another challenge was after I was inverted - i.e. the 2nd half of the roll, keeping right rudder in longer than you would think is needed, as well as to avoid letting up on the stick. At least in the 7ECA, you need to be patient with it, can't rush it.