PIREP: Zivko Edge 540

Budd Davisson, EAA/Sport Aviation, March, 1995

PAGE FOUR

Saddling up, it became immediately obvious Mark had the cockpit tailored just for him and he is mostly legs. Long ones! Bill Zivko had to get in there with one of his guys and adjust the rudder pedals back so I could come even close to getting full rudder.

Locking the canopy down, I cranked the engine, paying particular attention to Mark's directions for a hot start. The big Lycoming caught on the third time around and showed no indication of stumbling when the mixture went in.

The Haig locking tailwheel was controlled by a plastic coated cable stretched back from the vertical piece of tubing just under the throttle. Hook a finger around the cable and pull and the tailwheel was ful swiveling. Leave the cable alone and the wheel was locked straight forward. It was a nice, fool proof arrangement, although I still prefer steerable tailwheels.

As I lined up on the runway centerline, I was pleased to see I could see. Unless you've flown some of the mid-wing monoplanes with the low canopies you don't realize how blind the pilot is. The wing usually covers most of the pavement. The Zivko 540 is a long ways from being a C-172 in the visibility department, but it's not nearly as blind as some of the other unlimiteds. I had enough of the 75 foot wide Guthrie runway in sight I relaxed. Until that point I had been really worried about the landing. Now I was only apprehensive.

The takeoff wasn't so much a takeoff as it was a cat shot off a concrete deck. One second I was beginning to move the throttle and the next I was clocking 100 knots and going up at an angle that has to be seen to be believed. Everything about the experience was immediate. The engine spooled up the instant the throttle moved and the airplane reacted just as instantaneously. Left hand moving forward, airplane moving easily twice that fast, runway flashing past, brain telling my right hand to be gentle in bringing the tail up and the long hand on the altimeter started flashing in a circle.

By the time we were off the ground and I glanced inside, the airspeed was blasting past 110 knots and it was all I could do to keep it down to 120. Actually, I was well out of the pattern before I realized the airspeed was in knots, not mph, otherwise I would have pulled the nose into an even more rediculously steep attitude to keep it down. As it was, I timed the rate of descent at something over 3,500 fpm. Now that calls for explaination marks!!

The instant the gear left the ground I could feel the ailerons in my hand. I don't mean I could feel the airplane moving, I mean I felt the ailerons, as if their trailing edges were nested in my palm and I could sense their tiniest movement and the airplane instantly reacted. This is not an airplane for those of heavy hand. But, even at that early stage I could tell the stick ratio was long enough the airplane didn't feel twitchy.

As quickly as the airplane responds to a control input of any kind it would have been easy for the airplane to have been like trying to balance on a bongo board (those things where you try to stand on a board balanced on a roller). The stick ratios eliminate that feeling almost completely. Although the perceived pressures might as well be zero, they are so light, the stick has to move far enough that the pilot has total control and is able to really fine tune his movements.

It also didn't have any breakout forces to speak of, in any direction. In fact, a minute or so later when leveling out at 4,000 feet, I was treated to a unique control feel. It was unique because all stick force gradients were perfectly flat. Perfectly flat. The forces in any direction didn't seem to change at all regardless of how far I displaced the stick. In pulling "G", the stick force felt the same all the way through. The pressure at full aileron deflection was the same as barely starting a turn. The pressures also didn't change with speed.

It was hard to get full aileron deflection because the airplane whipped around so fast, that by the time you could get the stick up against a knee the airplane would already be right side up. The roll rate has been timed at 420 degrees, which is enough to blur the horizon. This is expecially true in doing vertical rolls. I've never been especially good in the vertical, but it goes around so fast you're into the second one before you know you've come close to finishing the first one.

Does it stop while rolling? On my first vertical I thought I'd do a quick half roll to see how it felt. Blur! Twitch the stick back the otherway to stop and my head bumped the side of the canopy as the airplane slammed to a halt. Crisp is hardly the word for it!

A lot of airplanes that have light control pressures in pitch will be assymetric in their behavior. They'll be light when positive but it takes a healthy arm to get much negative G on the airplane. This is absolutely not the case with the Edge, it comes as close to being the same outside as inside as any I've seen. It takes a little more arm, but only a little and just a touch of trim lets it fly hands off inverted. This made maneuvers like rolling 360's a whole lot less work.

The way the airplane handled when slow is at least as impressive as how it handled the fast stuff. Pulling out of the tops of verticals, I was being ginger, just letting it zero G its way over. The big engine let me do anything at that point because I was purely ballistic, just a passenger behind a whirling MT. At one point I bought the power back while pulling over the top at zero speed waiting to see what it would do. It didn't do anything. It kept on pulling. At least twice I found myself messing around at speeds around 30 mph, full back stick and still flying around the corner because I was low on G. Then I got down just over stall and honked into a hard corner trying to stall it. It would buffet a little but not do anything unusual. Then I'd unload, hit the power and go shooting straight ahead like out of a sling shot. Coming out of a slow speed situation, it acts as if it has JATO bottles.

Incidentally, a couple of times I played with the power while going verticle down hill to see what the prop would do. I pulled the power all the way back and even though I was pointed straight down, the prop would flatten out, airplane would slow down and I'd slide forward into the straps. Later, while shooting landings, I got a kick out of the way the big prop acted like a spoiler. Just a touch of power would keep the blades from flattening out, but pull the power and it acted like drag chute.

The first flight of any airplane is a tentative meeting of friends, you circle around one another trying to figure out the best approach. That's why a second meeting is always a must. You've had time to think about the first meeting and you've got all sorts of ideas about the second. Unfortunately, I only had time for one flight in the EDGE 540 which is no way to judge an unlimited aerobatic airplane. Assuming, that is, I was capable of juding it in the first place, which I'm not. I doubt if there are 25 pilots in the entire world capable of truly saying how well the airplane stacks up against the unlimited hot dogs and I'm not one of them.

Judging from the tapes I've seen of Kirby Chambless flying his Edge 540 at Fond du Lac, there seems to be little doubt the airplane can do some amazing stuff, including hovering at zero airspeed.

It would be nice to see something like the Edge make a serious mark for itself. It's American born and bred and comes out of a small shop tended to by loving hands. In a wildly three-dimensional sort of way, the Edge 540 and Zivko Aeronautics represent the best of the American spirit. Get an idea and make it happen! And that's exactly what the Zivkos are doing.

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