Vertical 8s

[Kevin Horton]

The first serious cold snap of the season hit last week. The overnight lows were in the -20 deg C (-4 deg F) range for several nights. Saturday my schedule allowed me to spend most of the day at the airport, so I plugged in the preheat at 10:30 AM, then went into Smiths Falls to do some final Christmas shopping. I started the engine just after 2 PM to go flying, dressed like a Michelin man, with all my cold weather flying gear.

Given that it was fairly cold, I decided to try some manoeuvres that probably wouldn't be possible in the summer. I experimented with loops from very slow speed. I found that I could get the aircraft around loops starting at 100 kt IAS. They were pretty ugly loops (quite egg shaped), as the airspeed was very slow going over the top, but they worked.

Next, I decided to try a manoeuvre that I used to enjoy in the Canadair CT-114 Tutor (Canadian military jet trainer) - if you've seen the Snowbirds aerobatic team, you've seen some Tutors. The Tutor had enough vertical penetration to do what we called a "Vertical 8". This was a half loop, followed by a roll to upright, then a loop, followed by a roll to upside down, then the second half of a loop. The manoeuvre would look like a figure eight - two balls, one on top of the other. In the Tutor, you started at 350 kt, pulled 5 g on the first half loop, and started the second one at about 200 kt. In the winter, when it was very cold, we could do what we called a "Snow Man", which was like a Vertical 8, but with a third ball on top. You started at VNE (412 kt), and pulled max allowed g (7.33 g) for the first one, and you were going very slow over the top of the third one, but it would make it around. Those were the days!

In the RV-8, I was quite impressed to find that I could start from 180 kt on the bottom of the first half loop, and have 100 - 110 kt at the start of the second loop. I pulled to idle coming down the back side of the loops, and there was no problem keeping the speed well below VNE (200 kt), as long as I got the g on early, and kept it on. Note that my three-blade MT prop has a huge amount of discing drag at idle, so someone with a different prop might find that airspeed control was a bigger issue.

I really didn't expect that this aircraft would have what it took to do a Vertical 8. Gotta love these cold temperatures

[WillyEyeBall]

Kevin,
I saw Van do this maneuver in his "new" RV-4 in 1984 at Oskosh. That's one maneuver I haven't been able to do yet.

Bill McLean
RV-4 slider
Sky Dancing

[pierre smith]

....into the lower half loop?

Best,

[Kevin Horton]

Originally Posted by pierre smith

What was your terminal speed after the split-ess into the lower half loop?

I was coming out the bottom of the second half loop at around 180 KIAS. I could have come out slower if I pulled a bit harder. I could have also easily busted VNE by a whole bunch if I was slow getting the g on.

[tinman]

Kevin,
Thanks for this post.
Do you have an inverted fuel/oil system? I have a fixed pitch with no inverted system and have found that I need a higher initial speed in order to pull a loop with any sort of "0" shape to it...my problem is probably pilot induced, but in order to round out the top of the loop, I must "push" a tiny bit on the top. Sometimes I burp a slug of oil, but never has the engine stumbled... I need a 3 g pullout to keep things slow...
Any tips? Should I expect an "egg" to be the best outcome?

[Kevin Horton]

Originally Posted by tinman

Kevin,
Thanks for this post.
Do you have an inverted fuel/oil system? I have a fixed pitch with no inverted system and have found that I need a higher initial speed in order to pull a loop with any sort of "0" shape to it...my problem is probably pilot induced, but in order to round out the top of the loop, I must "push" a tiny bit on the top. Sometimes I burp a slug of oil, but never has the engine stumbled... I need a 3 g pullout to keep things slow...
Any tips? Should I expect an "egg" to be the best outcome?

I do have inverted fuel and oil systems, but I wasn't trying to do a nice, pretty, round loop, so I did not push going over the top. I was down around 40 kt going over the top, so it wasn't going to be pretty no matter what I did. But it sure was fun.

[jferraro17]

"...Those were the days."

Great post Kevin! I quoted this part because it brought a smile to my face, as a former T-37 IP. We could do a vertical 8 entering at Vne and g-locking the other guy

Sure motivates me to get this dang RV-8A done...and makes me wonder about those tiny bolts holding my tail on!

Merry Christmas!

Joe

[Danny King]

Kevin,
I had a Air Force student pilot (UPT) start a Split S at mil power, twenty thousand feet, and 200 knots. The aircraft was doing 500 knots when reaching level. Then he rolled inverted, and started a second Split S from 500 knots. I took the T-38 away from him, and recovered from the high speed dive before we broke windows less than ten thousand feet below us. Those truly were the days!

I going to try the vertical 8 in the Doll. Sounds like fun!

[zspivey]

Have enjoyed all posts on the vertical 8.
Don't believe I will try it. I think I am a good pilot. The reason I think so is, I know my limitations. Believe this maneuver exceeds my limitations.
I do admire those of you who have the motor skills, knowlege and experience to fly this one. It must be great.

[rocketbob]

Originally Posted by Kevin Horton

I do have inverted fuel and oil systems, but I wasn't trying to do a nice, pretty, round loop, so I did not push going over the top. I was down around 40 kt going over the top, so it wasn't going to be pretty no matter what I did. But it sure was fun.

Sounds like it! I'll have to give this a try. I like to do rolls on the top of loops, this will add a little bit to the fun. It doesn't matter how slow you are at the top if you unload, since the airplane can't stall at zero g.