Barrel roll

motoadve

motoadve

Pre-takeoff checklist
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motoadve
Learning the barrel roll in my CJ6 Nanchang.
If I try to do a nice wide big barrel roll, I end up too fast at the bottom.
If I do close shorter ones its fine.
What is the trick to not gain that much speed at the end of the maneuver?
Here is a video.

 
First, be sure you're pulling about equal G on entry and exit. Besides that, the main reason for exiting low and fast is due to not completing half of the roll by the time you've reached the apex of the looping component. You must be wings level inverted at the apex of the loop. If the airplane has started to head slightly back downward before you've reached wings level inverted, you will exit low and at a higher airspeed. Saw this happen at least a couple times here. Leave the power constant.
 
Looks like your roll rate is too slow through the first 1/4. Almost like a 30 degree pull followed by a roll instead of a constant roll
 
OP, there are lots of ways to do barrel rolls, there are no real standards other than the goal of ending up at the same heading and altitude you started from. You can pitch up first and then do a tighter barrel roll, or you can entirely integrate the pitching and rolling and aim for a 90 degree heading displacement on top...and anything in between. Regardless of how you do it, the same principle applies - if you have not reached wings level inverted before the airplane starts its parabolic trajectory back down, you will end up low, fast, and off heading.
 
RoscoeT pretty much sums it up. In my little Sonerai, I aim for 90 degrees of heading change and the top of the cowl just on the horizon as I get to inverted. If the nose is through the horizon as I roll inverted, I know I'm gonna end up too fast and hunting for the heading at the end.

The thing that helps me the most is to use a long straight road as my heading reference, with a local peak 45 degrees off my nose. The spinner describes a circle around the peak. I'm not perfect every time. But, I'm working on it.
 
Not an expert by any means at all, but the roll in the video looks more like an aileron roll than a barrel roll. Shouldn’t there be more of a heading change during the course of the roll? I’m looking for something like 90 degrees from the flight path course at the top inverted portion. I don’t see anything like that in the video.


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jimhorner said:
Not an expert by any means at all, but the roll in the video looks more like an aileron roll than a barrel roll. Shouldn’t there be more of a heading change during the course of the roll? I’m looking for something like 90 degrees from the flight path course at the top inverted portion. I don’t see anything like that in the video.
Click to expand...

No, he's doing a barrel roll with heading change, just not 90 degrees. Like I said above, there is no standard for a barrel roll. These rolls were barreled. A plain positive G aileron where you pitch up a little, neutralize the elevator and apply aileron is still technically a barrel roll, but his rolls were barreled more than that, but less than 90 degrees. It has to do with the corkscrew trajectory of the airplane. Forget heading. Pretend the airplane was a bowling ball going through the air. Viewed from behind, it would corkscrew through the air like those roller coasters. Technically the only way to avoid doing any degree of barrel roll is to either do a ballistic (purely zero G) roll, or a level roll where the flight path does not change. The latter requires positive/negative G transitions and lots of rudder.
 
Less of an expert than jimhorner. What is the role of rudder in a barrel roll? What balance between elevator, rudder, and ailerons? Barrel rolls weren't covered in the short "intro to aerobatics" course I took years ago.
 
Barrel roll is a positive G, ball-in-center roll meaning the only function of the rudder is to counter the adverse yaw of the aileron input as required to maintain ball in center coordination.
 
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Been practicing more, I climb steeper now and then start rolling, ending up higher and not that much faster.
At the top I get the feeling of float like when doing a loop.
I have the impression it should be a constant G maneuver? or getting the float at the top is part of it?
 
A big wide barrel roll should float a bit over the top just like a normal loop, not constant G. Typically the only constant G roll you should be doing is the basic 1G roll where you pitch up, neutralize the elevator and apply aileron while keeping the stick in the 1G position all the way through. As mentioned before, this is technically a (tight) barrel roll, but not really what you're after in this case.
 
Ok , it felt better when pulling steep and making the roll and float, no gain in speed or much loss in altitude, still working on it.

Barrel roll starts at 1:12 minutes.

 
I thought it was supposed to be a constant 1 g maneuver.
 
As already mentioned, there are lots of ways to do barrel rolls. If you're doing a big wide one with a 90 degree or so heading displacement on top, then the G loads should vary just like a normal loop, with a float over the top. If you're doing a tight barrel roll with very little heading displacement, that's the constant 1G roll, aka "Hoover" roll. And lots of area in between.
 
To add to what others have said: I tell my students - check that the nose is above the horizon when wings are level, inverted half way through, if not then move the stick forward to flatten it out.
 
A proper barrel roll should have you wings level inverted with 90 degrees of heading change. It’s not a 1 G maneuver and in most aircraft you use about a 2 G pull. You need to start the nose up at least 20 degrees before you start the roll. You need to relax the G as you go inverted or you will go nose low every time. As you roll back upright increase the G back toward 2 G’s.
 
Jeff767 said:
You need to start the nose up at least 20 degrees before you start the roll.
Click to expand...

Not sure if you're referring to the typical pitched up 1G aileron roll, but you don't have to do this with barrel rolls. You can make the full barrel roll a precision maneuver by combining two quarter clovers - one up, one down into a continuous barrel roll. Quarter clovers are sometimes done in aerobatic competition and involve integrating the rolling and looping such that you don't do one without the other, and maintain a constant roll rate and hit the 90 degree heading mark on top simultaneous with reaching wings level inverted. So in this case, you don't pull up first and roll, you start rolling as soon as you start pitching.
 
motoadve said:
Been practicing more, I climb steeper now and then start rolling, ending up higher and not that much faster.
At the top I get the feeling of float like when doing a loop.
I have the impression it should be a constant G maneuver? or getting the float at the top is part of it?
Click to expand...
You relax the back stick just slightly as you approach inverted. You should be still just postive, about +.5g as you go over the top, just like in a loop. Otherwise, you'll be egg shaped and picking up speed on the back side. If you arent recovering at the same altitude/airspeed, this is most likely the problem.

I was looking at your 2nd video, and it looks like the clouds and the road don't really move much in relation to your directon of flight. This makes it seem more like a ballistic roll than a barrel roll. Try doing one with a mountain peak 45 degrees off your nose in the direction of the roll, and keep that peak in the same relative bearing as you do the manuever. It will require 90 degrees of heading change in the first half and another 90 degrees in the 2nd half.
 
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RoscoeT said:
First, be sure you're pulling about equal G on entry and exit. Besides that, the main reason for exiting low and fast is due to not completing half of the roll by the time you've reached the apex of the looping component. You must be wings level inverted at the apex of the loop. If the airplane has started to head slightly back downward before you've reached wings level inverted, you will exit low and at a higher airspeed. Saw this happen at least a couple times here. Leave the power constant.
Click to expand...
Yup, that's the trick.
 
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