View Full Version : IAC Primary Aerobatics without inverted oil/fuel

08-29-2011, 02:40 PM
Any IAC members flying their RV without inverted oil/fuel?

What techniques are you using to manage the inverted portion of the 45 downline off the 1/2-cuban? Or do you simply accept the point deduction and roll upright at the 45 and extend the remaining downline upright in order to recover at your initial altitude?

Any tricks to sharpen the spin entry? My -8 tends to ease into the spin rather than break into it.

Has anyone actually won or placed in a primary or sportsman class IAC event?


08-29-2011, 05:26 PM
Here's a darn good result by VAF member Bill 'WillyEyeball' McLean (RV-4). He's got inverted systems, but you can fly Sportsman without them if you don't mind some engine sagging (carb only) and momentary loss of oil pressure and maybe a little oil out the breather. Try it and see how much your plane really loses. 2-3 seconds of oil pressure loss is no big deal, and also happens with inverted systems.


One more with an RV-8:


Regarding the half-cuban, the judging criteria do not require your entry and exit altitudes to be the same. Just keep the looping portion round and establish a precise 45 inverted line while maintaining the 45 degree attitude during and after the roll. The length of line is up to you, but you must draw a perceptible line. Otherwise, it's a downgrade. Line lengths before and after the roll should be equal. RVs accelerate pretty fast on 45 downlines, so you wouldn't want a long line before the roll even with inverted systems. Your exposure will be so short, that you wouldn't necessarily need to cheat the figure, even without inverted systems. The only way you could remain positive throughout the figure is to start the roll before you reached the 45 degree inverted attitude.

Regarding spin entries, the biggest thing that will help is to climb slightly into the spin, keep the stick coming back steadily, and hold a little rudder in the direction you want to spin. Keep the stick coming back, but do not yank it at the last second - if the judges see the nose come up sharply before the stall, they'll call forced entry, or even zero the spin. As soon as the plane stalls, quickly apply full rudder immediately followed by full aft stick. The judging criteria for the spin is simultaneous movement about all three axes during the entry - nose drop, yaw, and roll. Also, don't force it by applying rudder before the stall. This will also result in a downgrade.

Every airplane is different, so it's hard to get too technical regarding spin entries. Just takes practice and playing around with the timing of the inputs. You can also mess around with aileron and a brief application of power in order to clean up the entries a little. Stopping on heading is pretty self-explanatory, but the biggest problem folks have in adapting to competition spins is getting vertical after the spin. Primary has a one-turn spin, which leaves you pretty well shallow after the spin stops. It takes a pretty good push to get get to vertical down. Look at your left wingtip to see how you did. You can either blend the push into the recovery, or pushover immediately as the spin stops. Just make sure it's immediate so that you don't get donwgraded for drawing a shallow line after the spin before pushing over to vertical. Get full power in immediately after the spin stops. This minimizes your altitude loss. Again, all you need is a perceptible vertical line.

For any figure, if you're going to be drawing short 45 and vertical downlines due to the rapid speed-build up of the RV, you should really make an attempt to set your lines crisply. For example, with the half-cuban, accelerate your pull during that last 10 degrees of pitch before reaching the inverted 45 attitude, then really pop the stick quickly to set the 45 line. Don't accelerate the pull too early, or the looping portion will be pinched. If you don't use this technique it can be hard for the judges to tell when you've established your line. Combine this with a short line, and you could easily get called for "no line before" the roll. Keep this in mind anytime you are setting (or breaking) any line, vertical, 45 or otherwise. Try to telegraph to the judges when you have set or broken a line. Be assertive, but also smooth.

08-29-2011, 06:38 PM
Thank you very much Eric! Nice explanations, especially the spin entry. I was playing with a little aileron in the entry the other day as it appears to me the -8 is slightly delayed in roll with neutral ailerons.

08-30-2011, 01:09 AM
Just a thought... Can you "trigger" the spin entry by giving opposite aileron to stall the inside wing first? I used to use that to help make a better defined spin entry when flying a 150 Aerobat. Without it, it wanted to wallow into the spin, and about 20% of the time it would spiral instead.