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Old Jun 12, 2010, 01:21 AM
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United States, MN, Minneapolis
Joined Jul 2009
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PZ Sukhoi XP - Maiden flight

My friendly LHS called me today.

I bound her to my Futaba 10CHP. I set her up for max throws all around. I adjusted the trims for zero deflection @ center-stick. With a Hyperion G3 CX 160 mounted to the rear of the slot, the CG is @ 37mm - right on factory spec. I had 4 Hyperion 160s charged & ready to go. It was time to fly!

Specs:

EW: 31.15g
Stock AUW: 35.80g
Hyp 130: 35.25g
Hyp 160: 36.00g
MA 180: 36.30g
CG: 37mm (Hyperion 160 to the rear of the slot)

Setup:


Control linkages set for max throw
Servo travel: +/-100%
Rates: 100%
Expo: 80% on ailerons & elevator; 25% on rudder

Test conditions:

Elevation: 940' AMSL
Temp: 67 F
Wind: 5 MPH; g15 MPH
Static RPM (Hyperion 160 - 30 sec into run): 7500 RPM

Maiden flight:

I couldn't wait for the wind to die down, so I took her up - despite the 15 MPH gusts. With the control surfaces visually centered, I lined her up & nailed the throttle. She was airborne within a few feet. A couple clicks of up-elevator trim & she was flying level - hands-off. I pulled to vertical, and she headed upstairs with authority. Like her predecessor, she handled the gusty conditions with ease.

General flight

Take-offs @ WOT are quick. As with all taildraggers, she requires right-rudder input to remain on course during the takeoff roll. She handles much like her predecessor. She seems to be fast enough with the stock prop, and had no trouble making headway in the wind. Slow-flight is great, and she's a pussycat on landing. The slight increase in weight over my V2 w/P-51 motor/GWS 5043/Hyp 240 didn't seem to be noticeable.

Aerobatics

Trimmed for level flight with the CG @ 37mm, she flies level inverted with a hint of down-elevator input. She tracks well through loops, and the increased elevator authority allows for some very tight ones, as well. She does have a tendency to corkscrew out of really tight loops when full elevator is used, however. Rolls are crisp. Like her predecessor, she rolls like a drill bit! Elevators are reasonably flat, although bit of wing-rock was present. Harriers also had some wing-rock, but it was manageable. As with her predecessor, her 3D performance will improve with the CG moved back to 38-39mm. Since she balances @ 37mm with no ballast, moving the CG to 39mm will be easy to do. A strip of clear packing tape under the horizontal stab should do the job.

She has plenty of power for hovering & vertical maneuvers; however the wind was too gusty for me to hold hover for more than a few seconds. She can accelerate vertically out of a hover, and she climbs straight up for a couple hundred feet or more with ease. The increased elevator/rudder throw is very noticeable (and very welcome!). Knife-edge flight is easy. She does sustained knife-edge at just over half-throttle. I couldn't check for coupling during knife-edge flight, as the wind was too strong.

The wind was starting to get quite unpredictable, so I cut my flying session short. I flew about 3 packs. I had to do zero forward speed, power-on landings, as the wind speed was often somewhat above her stall-speed.

First impressions:

HH got it right this time. This plane flies very well in stock form. There is plenty of power on tap for most any pattern or 3D maneuver. With max throws and some expo, she can be mild, yet wild when commanded. With the CG @ 37mm, she can fly very slowly, with no tendency to tip-stall. She's a real pussycat on landing.

Pros:

* Much stronger tail feathers. They seem to be made from the same material as the J-3 Cub's tail feathers.
* Plenty of power with the stock motor/prop & a good battery.
* Achievable aerobatic CG.
* 6400L brick is a great improvement.
* Pushrod guides dramatically improve elevator & rudder authority.

Cons:

* Slightly heavier than a V2 with a Hyperion 240 mAh flat-pack cell & c/f strips on the tail feathers. (Not enough to be noticeable in flight, however.)
* Under certain conditions, the blue leading edge can make the wing difficult to see during a head-on approach.
* Aileron linkage could be factory-set for maximum throw, so that one wouldn't have to cut the decals right away.

Summary:

HH incorporated the most cost-effective mods from the R/C community, and added a robust tail, pushrod guides, and the long-throw brick. The XP flies very well right out-of-the-box. It flies even better with higher-c cells. Horizon - the XP is a real winner! Thanks for listening!

Joel
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Last edited by turboparker; Jun 12, 2010 at 11:43 PM.
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