RV-8 Slowest loop entry speed

[RV8R999]

Curious how slow some of you guys are when you enter loops and what initial g loading used to get over the top?

I've entered as slow as 145mias @ GW of 1400#, 5000ft DA with a 3.5g pull and still had margin. Wondering if anyone has gone much slower? I hadn't fully explored the spin characteristics at the time and wasn't willing to find the loop entry limit. Thought I start that up again.

[lostpilot28]

Hey Ken,
I don't know how close of a data-point this will be for you, but I watched on the ground as I had a test pilot put my airplane through the ringer at 6 hours (Phase 1). He did several loops, going slower each time to see when it wouldn't do it again...the last successful loop was at 110 mph, and he was at 7,000 ft. On the 105 mph attempt, the elevator was no longer effective when the RV was pointing straight up. The 110 mph loop was ugly, but it went around.

Weight of the aircraft was close to 1400 lbs, with just the pilot and a little over half full of fuel. I'm guessing an -8 would be similar.

[schristo@mac.com]

pretty hard to do much of a loop if you don't have enough energy to float it out at the top... more of a teardrop flop than a loop... still fun though.

[RV8iator]

going slow, but it sure works good if you enter them at 200 KTAS.. Perfect, round, pretty loop.

Smooth pull right to 3.5 g's, about 1/4 g over the top and easy down the back side back to about 3..

Works every time

[bach33089]

Unfortunately, no RV-8 experience YET, but I know the Extra can loop from 80knots. The airplane stalls at around 60? nose up but the prop wash over the elevator keeps it going around. It buffets like ****, and will try to roll off on a wing, but good rudder control will see you through. Some call this a "micro-loop." My Super Decathlon will do the same thing from around 95 mph. I think the trick to this is a CS prop so that you maintain flow over the elevator throughout the maneuver. The trick is to find that "sweet spot" entry stick position that walks the line between accelerated stall and falling out of the maneuver. Worse case scenario, you'll end up in an upright spin. Make sure you have plenty of altitude and proper spin training before you give it a try, but it is a blast to see just how slow you can go! As far as the "shape" of the maneuver, if done right, it should be fairly round, with a VERY tight radius.

[sandifer]

Minimum "looping" speed would be the minimum speed it takes to get the airplane vertical with full power, at which point it would flop onto its back. Not pretty, but would technically get it done. I bet you could add full power and do it from 70kts or so in an RV depending on your weight and engine/prop combo.

[RV8R999]

Originally Posted by sandifer

Minimum "looping" speed would be the minimum speed it takes to get the airplane vertical with full power, at which point it would flop onto its back. Not pretty, but would technically get it done. I bet you could add full power and do it from 70kts or so in an RV depending on your weight and engine/prop combo.

Funny! I was trying to keep things more loopy rather than floppy.

[RV8R999]

Originally Posted by RV8iator

going slow, but it sure works good if you enter them at 200 KTAS.. Perfect, round, pretty loop.

Smooth pull right to 3.5 g's, about 1/4 g over the top and easy down the back side back to about 3..

Works every time

I agree however, for practicing competition aerobatics I'm thinking the slowest A/S in which a nice looking loop can be performed is better for staying inside the box and managing A/S on the downlines. I haven't competed yet but I've practiced and the box is pretty small. I'd like to keep everything right at Va if possible.

[sandifer]

Originally Posted by RV8R999

I agree however, for practicing competition aerobatics I'm thinking the slowest A/S in which a nice looking loop can be performed is better for staying inside the box and managing A/S on the downlines. I haven't competed yet but I've practiced and the box is pretty small. I'd like to keep everything right at Va if possible.

Ken - in the Primary sequence, the loop comes after the half-cuban, which can have a high exit speed if you let it. But in an RV, there's no need to get over 150kt doing the Primary or Sportsman sequence. The lower your loop entry speed, the more you'll need to pull. At slower entry speeds, you'll probably want at least 4G and full power on the way up.

Make sure you don't make a pull and freeze it until near the top of the loop. You have to increase the amount (not pressure) of the pull after passing vertical. Keep this going until about 30 degrees before level inverted, then relax it and be patient floating over the top. Failure to do this will produce a flat spot on the second quarter of the loop and cause the top to be pinched. Almost everyone I've seen learning to do round loops starts off with this problem - not increasing the pull sufficiently past vertical, and not unloading and floating enough before reaching the top. Let it float to around 30 degrees nose down from inverted before steadily and smoothly increasing your pull and pitch rate all the way to the bottom. The G meter reading at the bottom should read the same as your initial pull. Make sure you shift your view to the wingtip after you've lost the horizon during the initial pull. Otherwise, it'll be hard to learn to do a round loop. I see lots of videos of folks never looking anywhere but straight ahead, which means you've lost reference to your pitch rate until the horizon appears at the top. Shift your view back to straight ahead when you can see the horizon at the top to ensure you're wings level and maintaining heading.

Loops are hard to self-critique and need a lot of help from the ground initially in order to get them round. One thing that will help a lot is to pay attention to your your pitch rate throughout the loop. For example, if you enter a loop at 150kt, and float over the top at 75kt, your pitch rate at the top must be half that of what you initially started with if you're going to have any chance at making it truly round. As you start down the backside at full throttle, start returning to your original power/RPM setting (FP prop only) once past 30 degrees nose down. And of course come out at the exact same altitude, and expect that nice bump of your wake.

[mike newall]

Jerry,

One of the recent accident reports showed the various g limits throughout all the speed envelope and I seem to remember at or close to Vne, it was much reduced.

Just a thought