Originally Posted by luddite42
RV acro is not special. Just get some training in a Decathlon and understand the RV is cleaner.
I am not telling you HOW to do a loop. As luddite42 said, good advice, get some dual, understand before you start.
Second, there are things you should do and think of before looping your RV. You should start at 3000 feet AGL and practice stalls and stall recovery. Stalls (and spins) are always possible with a poorly executed aerobatic maneuver. Consider practicing stalls and doing steep turns to get your feel for stick force and G force.
Blue line or maneuvering speed is 134 mph. We are not doing abrupt maneuvers, just be aware. 180 mph is bottom of yellow, or smooth air speed. 210 mph is red line, never exceed.
A loop can be done easily at 3G's initial pull up. In fact all aerobatics in the RV can be done at 3G or less. Make sure your seat belts are tight and secure. With constant speed prop you can just set throttle and RPM and leave it. Fixed pitch prop may require some throttle use. Make sure your W&B are in CG and aerobatic weight. Make sure you are in an area legal for aerobatics (not on an airway), and clear the area for traffic...
A loop starts in level cruse flight (recommend start at or below yellow line 180 mph); you are +1G (straight and level), force pushing you in seat. Negative G is pulling you our of your seat (which you should not feel in a loop). We consider load factor "G" to be vertical, perpendicular to the wing in any attitude.
Initiate a moderate straight and level cruise (under 180 MPH bottom of yellow line) and pull up smoothly to 3G. (2.5-3.5 will work but beginning 3G is about right). Having a G meter helps. There is some significant stick pressure (like in a steep turn), but again don't over load and don't be abrupt. Blue line or maneuvering speed is 134 MPH.
Too little pull up you will run out of airspeed before getting over the top. Too much you are needlessly loading the plane and may have excess speed at the bottom of loop. As you go through the loop you will release the back pressure continuously, to make a round loop (not an egg shape).
At first 90 degrees look left and right out the wings to see your position in loop and make sure you are going straight (up). You may need a little rudder to keep from yawing and making the loop fall over to the side. This is your chance to get orientated. You speed should have bleed off to about 125 mph
As you reach the top of the loop, inverted 180 degrees from direction started, you have released most or all of the back pressure. At the top of the loop you will be above stall speed, say 70-80 mph (Vs = 59 mph bottom of green) and less than 1G. Anything over 0.0 G is positive. You want to have about +0.5G +/- . You want to keep some positive G. Some folks float over the top, adding some forward stick. Engines and fuel will be OK for a few seconds near zero G, I don't do that. Speed over top should be over stall with margin (and not too fast either). Again look out the wings, and look out top of canopy, to see your position over the ground; did you get off heading (typically you use a road to line up with)? Keep track of your progress through the maneuver and check your speed and attitude is as planned.
As you start down the back side you will feel the G forces built (and hear airspeed build) back up. You increase stick back pressure smoothly.... At the bottom you should be a 3G and same speed you started with (180 mph for example) and same altitude (approximately). You may even hit your own wake turbulence. Do not go over 210 Vne ever.... You will also be looking at altitude because you are trying to level off at entry altitude. At the straight down line look out wings and again see your position and heading.
Going through loop you see speed slowly decay from 180 to 70 mph for example, then build back on the back side. The initial 3G will go to 0.5 G over the top, back to 3G at bottom... If not doing another loop you release back pressure at the bottom, straight and level, going from 3G to 1G, and that is the end of maneuver.
It is way harder to explain than do. I start students doing 3G pull ups and then knocking it off and leveling off. Doing steep turns and getting warmed up for G's is a good start... As was suggested get some aerobatic dual. There are great books on aerobatics as well.... RV aerobatics are fun, easy and safe but it is serious business, so have a plan. However I say easy. To do a loop or roll is easy, to do them well, is very difficult and takes real dedication.