Aerobatics in the 7ECA

[volvo164]

Today was my first Aerobatics lesson in my 7ECA. My last aerobatics instruction (I only had 3 or 4 lessons before) was 2 years ago in a Super D. Things are different in the 7ECA than what I remembered in the Super D (of course). Rolls a major pain (I don't have spades ... yet). The fixed pitch prop / throttle needs some experimentation. In terms of inverted, we've only done slow rolls, so far, with the engine sounding just a bit rough upside down. I was too busy trying to get the maneuver, fighting the stick and didn't get a glimpse at oil pressure. Question: the manual states at least 6 quarts for inverted flight - implying you can fill it up beyond the 6 quart line. Do others do that? I'm a bit annoyed at the effort to roll. Since it snaps into a competition steep turn so readily, I thought it will be fine without spades. But I'm finding that for a full roll (either simple aileron or slow roll), getting the stick all the way to the stop takes quite a bit of effort and time, and the last thing you want to do in this plane is to slow the roll down.

 

[Bob Turner]

You might have the wrong manual. The six quart limitation is for the inverted oil system and fuel injection. If you have a carbureted 115 hp Citabria, inverted flight will cause loss of power and oil. Not all of the oil, but enough to get your attention on postflight.

 

[Big Ed]

Older Super D's take a lot of stick force in the roll too, even with spades. Just part of the design. My current Super D does not have spades, but my previous Decathlon CS did. It was still a bloated cow in the roll, but it was manageable once you got used to it. I have considered trying to chase down some spades for my new plane, but I have a lot of wants that are higher on the mod list. I have also read that the aftermarket spades put a lot of stress on the structure.

If you are competing, straight up slow rolls are not that common anyways. Rolls are usually a component of other maneuvers, often at slower speed where stick forces are less. Try the half roll on an Immelman, Cuban or Reverse Cuban. You might find that more pleasant. I never felt the Decathlon roll rate was a hindrance on those maneuvers, and in fact felt the judges enjoyed the graceful look if done well.

You should be able to find your oil system max capacity somewhere in specifications. Maybe in the service manual. For example, my Super D holds 10, with 8 marked on the dipstick, and 6 as aerobatic minimum. I never fill over 8 because I am told the excess just vents overboard.

 

[volvo164]

Thanks for the inputs:
- I do have the correct manual, the original Champion, that's for all the 7 series from the 7ECA to 7KCAB. I was reacting to the last page in the manual, that stated - Special Notice! - Warning - Do not fly inverted for more than 2 minutes - Minimum oil for inverted flight must be 6 quarts. It's a strange warning to stick in at the end, without specifying models. It seems only applicable to the KCAB, since none of the other models will make it anywhere near 2 minutes. Indeed the 7ECA's capacity is 6 quarts, hence why I got confused - but it now seems this warning must have been some legal guy asking it to be stuck in the manual at the end.
- I do have the ACA metal spar wings - so I'll probably go ahead and get the spades from them for it. But I'll wait for another lesson or 2, maybe it's just getting a technique perfected - I developed a strong dislike for them on the ground, banging into them. Interesting comment about stress on the aileron - I can see how that's the case, although without them I feel like I'm putting quite a bit of stress on the pulley system.
My current objective is to be able to do try to compete at the Sportsman level with it, just for fun.

 

[Big Ed]

You will have a blast in Sportsman!

The spade stress comment applied to the older aileron design and wooden spars. It is my understanding that the new ACA metal wing design addresses that issue.

 

[aftCG]

After about 20-30 times of walking into those spades you'll learn.

I've only been designing airplane parts most of my career, but I have stayed at a Holiday Inn Express recently.

Spades mounted on the inboard end per the Olin Pash design don't increase stress on the plane, assuming the aircraft is flown the same. If anything they reduce the stresses on the control cables, stick assembly and of course the user's muscles. If it weren't physically possible to reach full deflection before but now you can, that's a different story. In my experience all they do is result in balanced control inputs instead of super heavy in roll and okay in the other two axes.

 

[Bob Turner]

No - I have owned a J3 for 58 years, and yesterday, for the hundredth time, I opened up my scalp on the lower aileron horn. Admittedly, those inboard spades seem a lot safer.

 

[BB57]

Thanks for the inputs:
- I do have the correct manual, the original Champion, that's for all the 7 series from the 7ECA to 7KCAB. I was reacting to the last page in the manual, that stated - Special Notice! - Warning - Do not fly inverted for more than 2 minutes - Minimum oil for inverted flight must be 6 quarts. It's a strange warning to stick in at the end, without specifying models. It seems only applicable to the KCAB, since none of the other models will make it anywhere near 2 minutes. Indeed the 7ECA's capacity is 6 quarts, hence why I got confused - but it now seems this warning must have been some legal guy asking it to be stuck in the manual at the end.
- I do have the ACA metal spar wings - so I'll probably go ahead and get the spades from them for it. But I'll wait for another lesson or 2, maybe it's just getting a technique perfected - I developed a strong dislike for them on the ground, banging into them. Interesting comment about stress on the aileron - I can see how that's the case, although without them I feel like I'm putting quite a bit of stress on the pulley system.
My current objective is to be able to do try to compete at the Sportsman level with it, just for fun.

I'm assuming you are talking about the large print special notice on page 36 of the manual for the 1970 and earlier models. I agree the 2 minute or 60 psi minimum oil pressure warning is directed at the 7KCAB as none of the other models will run more than a few seconds in a negative G condition.

The oil warning is less clear, but I also think that's applicable to the 7KCAB only as well. The original Champion inverted oil system uses a baffle with a trap door in the sump along with a "clunk" type oil pickup. In inverted flight, the trap door closes and the baffle becomes the "bottom" of the sump, with the oil pickup pivoting down to stay immersed in the oil. However oil isn't returned to that side of the baffle so when the oil trapped in the sump is gone, the oil pressure will rapidly fall. In that regard 6 quarts is probably the minimum needed to get any meaningful period of oil pressure above 60 psi in inverted flight.

That "2 minutes" is also in my experience very optimistic and is probably based on a full sump with 8 quarts of oil in it. In practice I don't push it more than 30 seconds and I think 45 seconds is probably a more realistic number with 6 quarts of oil. But then again, 30 seconds is plenty for the limited inverted flight I do.

If you ask ACA they'll tell you it's a horrible system and to replace it with the Christen inverted system. It is a much better system, especially if you engage in a lot of inverted flight and negative G maneuvers. However, it is more complex and consumes more of the already very limited accessible firewall space on the 7KCAB. There was also initially a 400 hour inspection required, but I don't think that proved to be needed. My 7KCAB has been through two engine overhauls and the engine and airframe logs don't reflect the 400 hour inspections or note any issue with the system at the 1600-1700 hour point where overhauls were done. Other than some minor rubbing on the pickup tube at TBO, I also also never seen anything on the internet or in person that indicates failed baffles or pickup tubes are a real issue.

The reality is that if someone is doing extensive inverted flight or negative G maneuvers they'll move on to an 8KCAB or something much more capable of inverted maneuvers pretty quickly.

In addition, in the Bellanca 1975-77 manual, 6 quarts is listed as the minimum for the Citabria models other than the 7ECA, which has a listed 5 quart minimum.

My dip stick is 1/2 quart off, showing just 6 quarts when I refill it with 6.5 quarts of oil in it at oil change. In other words there is 6.5 quarts oil in it when it's at the "6" mark. I maintain the oil level close to that mark adding a half quart at a time. With this practice, oil consumption stays right at 1 quart every 12.5 hours. If I fill it over that mark oil consumption goes up to about twice that amount as it starts venting the excess over board.

 

[volvo164]

I'm assuming you are talking about the large print special notice on page 36 of the manual for the 1970 and earlier models. I agree the 2 minute or 60 psi minimum oil pressure warning is directed at the 7KCAB as none of the other models will run more than a few seconds in a negative G condition.

The oil warning is less clear, but I also think that's applicable to the 7KCAB only as well. The original Champion inverted oil system uses a baffle with a trap door in the sump along with a "clunk" type oil pickup. In inverted flight, the trap door closes and the baffle becomes the "bottom" of the sump, with the oil pickup pivoting down to stay immersed in the oil. However oil isn't returned to that side of the baffle so when the oil trapped in the sump is gone, the oil pressure will rapidly fall. In that regard 6 quarts is probably the minimum needed to get any meaningful period of oil pressure above 60 psi in inverted flight.

That "2 minutes" is also in my experience very optimistic and is probably based on a full sump with 8 quarts of oil in it. In practice I don't push it more than 30 seconds and I think 45 seconds is probably a more realistic number with 6 quarts of oil. But then again, 30 seconds is plenty for the limited inverted flight I do.

If you ask ACA they'll tell you it's a horrible system and to replace it with the Christen inverted system. It is a much better system, especially if you engage in a lot of inverted flight and negative G maneuvers. However, it is more complex and consumes more of the already very limited accessible firewall space on the 7KCAB. There was also initially a 400 hour inspection required, but I don't think that proved to be needed. My 7KCAB has been through two engine overhauls and the engine and airframe logs don't reflect the 400 hour inspections or note any issue with the system at the 1600-1700 hour point where overhauls were done. Other than some minor rubbing on the pickup tube at TBO, I also also never seen anything on the internet or in person that indicates failed baffles or pickup tubes are a real issue.

The reality is that if someone is doing extensive inverted flight or negative G maneuvers they'll move on to an 8KCAB or something much more capable of inverted maneuvers pretty quickly.

In addition, in the Bellanca 1975-77 manual, 6 quarts is listed as the minimum for the Citabria models other than the 7ECA, which has a listed 5 quart minimum.

My dip stick is 1/2 quart off, showing just 6 quarts when I refill it with 6.5 quarts of oil in it at oil change. In other words there is 6.5 quarts oil in it when it's at the "6" mark. I maintain the oil level close to that mark adding a half quart at a time. With this practice, oil consumption stays right at 1 quart every 12.5 hours. If I fill it over that mark oil consumption goes up to about twice that amount as it starts venting the excess over board.

Yes, that was the notice that alarmed me - as I never got to the end of the manual before ;-)
I figured it had to be the KCAB only - but strange to put such a general warning in there. For my 1st acro training (about an hour) I went up with 5.5 quarts (which as you say is 6 given that I have a filter STC), and lost just a .25. I have brand new cylinders, so my oil consumption has been 1 qt. per 25 hours otherwise, keeping oil level at the 4.75 to 5.25 mark. Prior to the new cylinders, it was pretty bad ...

 

[BB57]

After about 20-30 times of walking into those spades you'll learn.

I've only been designing airplane parts most of my career, but I have stayed at a Holiday Inn Express recently.

Spades mounted on the inboard end per the Olin Pash design don't increase stress on the plane, assuming the aircraft is flown the same. If anything they reduce the stresses on the control cables, stick assembly and of course the user's muscles. If it weren't physically possible to reach full deflection before but now you can, that's a different story. In my experience all they do is result in balanced control inputs instead of super heavy in roll and okay in the other two axes.

I took some pipe insulation and sewed a simple nylon cover for it to make some forehead protectors for my ACA metal winged 7KCAB. I eventually added a length of bungee cord from one end to the other to loop over the back of the spade to keep them from blowing off in any wind. When it had the original wood wings it had a set of Olin Pasch spades. Since they were mounted on the inboard end of the aileron it was much harder to walk into them. With the ACA spades mounted outboard, something like this should come with the kit and or from the factory.



My early experiences with a Citabria were in a couple of 7GCBCs, a oleo geared 1965 and a later Bellanca model with spring steel gear. Neither of them had spades and I disliked the control harmony on both of them due to the excessively high aileron forces.

The accepted ideal is that the elevator control forces should be about twice as heavy as the aileron control forces and the rudder control forces should be about twice as heavy as the elevator control forces. Those relative control forces provide good control harmony without the elevators or rudders being overly sensitive.

----

Certification wise, for stick controls, minimum elevator control force for maximum g has to be at least gross weight/140 (12.5 pounds for a 1750 pound ACA metal spar winged Citabria), or 15 pounds, whichever is greater, but the upper limit is 35 pounds regardless of gross weight. With a +5.2 G limit that 15 pound minimum would work out to an average of 2.88 pounds per G and that's actually too low as it increases the potential to over stress the airframe. I used to own a Monnet Moni with a side stick and very low control forces. Describing it as "twitchy" in terms of pitch control is charitable and PIOs were a real possibility.

The lower limit is generally accepted as an average of 3 pounds per G to avoid increased risk of an over G condition, and the upper limit in the desirable range is about 8 pounds per G. Any forces above 8 pounds per G are going to quickly become tiring for the pilot. By that metric, the controls on a Citabria are still on the heavy side, but spades do help improve control harmony significantly.

 

[aftCG]

I took some pipe insulation and sewed a simple nylon cover for it to make some forehead protectors for my ACA metal winged 7KCAB. I eventually added a length of bungee cord from one end to the other to loop over the back of the spade to keep them from blowing off in any wind. When it had the original wood wings it had a set of Olin Pasch spades. Since they were mounted on the inboard end of the aileron it was much harder to walk into them. With the ACA spades mounted outboard, something like this should come with the kit and or from the factory.

View attachment 2769

My early experiences with a Citabria were in a couple of 7GCBCs, a oleo geared 1965 and a later Bellanca model with spring steel gear. Neither of them had spades and I disliked the control harmony on both of them due to the excessively high aileron forces.

The accepted ideal is that the elevator control forces should be about twice as heavy as the aileron control forces and the rudder control forces should be about twice as heavy as the elevator control forces. Those relative control forces provide good control harmony without the elevators or rudders being overly sensitive.

----

Certification wise, for stick controls, minimum elevator control force for maximum g has to be at least gross weight/140 (12.5 pounds for a 1750 pound ACA metal spar winged Citabria), or 15 pounds, whichever is greater, but the upper limit is 35 pounds regardless of gross weight. With a +5.2 G limit that 15 pound minimum would work out to an average of 2.88 pounds per G and that's actually too low as it increases the potential to over stress the airframe. I used to own a Monnet Moni with a side stick and very low control forces. Describing it as "twitchy" in terms of pitch control is charitable and PIOs were a real possibility.

The lower limit is generally accepted as an average of 3 pounds per G to avoid increased risk of an over G condition, and the upper limit in the desirable range is about 8 pounds per G. Any forces above 8 pounds per G are going to quickly become tiring for the pilot. By that metric, the controls on a Citabria are still on the heavy side, but spades do help improve control harmony significantly.

I totally agree on the stick forces in roll. The first Citabria I flew to get my tail wheel endorsement and mountain checkout had Pash spades. A few years later I bought my Citabria and on my first takeoff had a WTF moment when I realized what those spades did for me.

 

[Bob Turner]

Back to the 2 minute thing - the Christen system will run forever inverted. You run out of gas in two minutes. Getting gas back in to that header tank after you roll right side up is exciting - I was seriously looking for a place to land!

 

[Big Ed]

The inverted systems in my skull and eyeballs generally reach their limit before my airplane does.

 

[Bartman]

Today was my first Aerobatics lesson in my 7ECA. My last aerobatics instruction (I only had 3 or 4 lessons before) was 2 years ago in a Super D. Things are different in the 7ECA than what I remembered in the Super D (of course). Rolls a major pain (I don't have spades ... yet). The fixed pitch prop / throttle needs some experimentation. In terms of inverted, we've only done slow rolls, so far, with the engine sounding just a bit rough upside down. I was too busy trying to get the maneuver, fighting the stick and didn't get a glimpse at oil pressure. Question: the manual states at least 6 quarts for inverted flight - implying you can fill it up beyond the 6 quart line. Do others do that? I'm a bit annoyed at the effort to roll. Since it snaps into a competition steep turn so readily, I thought it will be fine without spades. But I'm finding that for a full roll (either simple aileron or slow roll), getting the stick all the way to the stop takes quite a bit of effort and time, and the last thing you want to do in this plane is to slow the roll down.

Volvo,

I too started rolling my 7ECA not too long ago and you're right (!!), it's a lot of work without spades to get the stick over to the stop when you're starting the roll at 130 mph! The spades make a huge difference, especially at higher entry speeds for aerobatics.

The 2020 Primary known sequence had the slow roll after a 180 degree competition turn which seems implausible since the recommended entry speed for a roll is 130 mph. I've been grounded for a couple of weeks but am starting up again this week and working on a more competition-appropriate slow roll is on my short list of stuff to do. Exiting a 180 degree competition turn would probably leave a 7ECA at about 95 mph so I'm not sure a competitive slow roll can be done at that speed, it would probably require a break from the sequence and a diving re-entry into the box to make it work.

Good luck, keep us updated and we'll figure it all out as we go!

Bart

 

[volvo164]

Volvo,

I too started rolling my 7ECA not too long ago and you're right (!!), it's a lot of work without spades to get the stick over to the stop when you're starting the roll at 130 mph! The spades make a huge difference, especially at higher entry speeds for aerobatics.

The 2020 Primary known sequence had the slow roll after a 180 degree competition turn which seems implausible since the recommended entry speed for a roll is 130 mph. I've been grounded for a couple of weeks but am starting up again this week and working on a more competition-appropriate slow roll is on my short list of stuff to do. Exiting a 180 degree competition turn would probably leave a 7ECA at about 95 mph so I'm not sure a competitive slow roll can be done at that speed, it would probably require a break from the sequence and a diving re-entry into the box to make it work.

Good luck, keep us updated and we'll figure it all out as we go!

Bart

I'm not at the point of stringing the maneuvers together, but started to discuss with my instructor. I guess the challenge is to figure out where and how to take deductions. Although reluctant to get the spades, I am planning to install them over the winter.

 

[Big Ed]

You can fly a slow roll at any speed. The half roll at the top of an Immelman or Split S is typically performed at 80 or so. You should have no problem flying a slow roll at 95-100, and stick forces will be pleasantly less than at 130. It may be challenging to avoid altitude loss, but higher nose high attitude in knife edge and inverted will minimize. Try in practice; worst case you fall out of it.

 

[Bartman]

that's true about the immelman, hadn't thought of it that way.

falling out though is a zero at a contest, taking a break is one point deduction I think.

 

[Big Ed]

If the sequence is well designed, maneuvers naturally flow together, with the end point of each maneuver putting you at an appropriate airspeed and altitude for the next. In that case, stringing them together is a simple matter of setting straight and level, then checking your entry altitude and airspeed. It helps to verbalize those checks when learning.

The sportsman sequence is by definition well designed, so that is a great place to start. The sequence is generally designed in thirds, with a wind correction maneuver after the second third. So pick the first 3 figures and try flying them with 5-10 seconds of straight and level between each. As long as you check speed/altitude, it is very easy to learn.

When you start learning box positioning, you simply stretch out the straight and level as needed to compensate for headwind and tailwind.

 

[Big Ed]

falling out though is a zero at a contest, taking a break is one point deduction I think.

Agreed, that's why I said to try it in practice, so you are not worried about points. If you chose to fly it that way, you would want to practice it dozens of times to refine your presentation. By the time you tried it in a contest, you would be very confident in your minimum airspeed to fly it.

Having never flown a 7ECA, I can't say for sure what the limits of performance are. But the Sportsman is designed for aircraft like ours to complete without a break if flown efficiently. 7ECA would be challenging for sure, but the judges would be impressed by success.

 

[Bartman]

I thought Primary used the 7ECA as its performance basis and Sportsman used the Decathlon. No? Sportsman is probably possible in a non-inverted 7ECA but breaks would likely be a necessity. Not sure, would have to look at the sequence.

I can just hear the judging line gasping at the sight of a 7ECA starting the slow roll at 95 mph and powering through it, barely! Probably with a few engine coughs at the halfway point.