Sport Cruiser

I had previously tried your VGs on the wings of my Piper Sport (Czech SportCruiser) with mixed results. However, recently I installed them on both sides of the fin in accordance with your directions for the elevator underside. Previously, I felt the rudder was ineffective, with little feedback, which I now believe was due to a stalled condition occurring when I deflected the rudder beyond a limited stall position, about half of its total deflection range.

I tested it today and, for the very first time, I had full control of the rudder on takeoff and even during higher-speed taxiing. My plane has a castoring nosewheel, so with an ineffective rudder at low speed, I usually had to rely entirely on the brakes to maintain directional control, even on takeoff, which was obviously not ideal. Today, with the VGs installed at 30 mm vertical spacing and 100 mm ahead of the rudder pivot (in accordance with your elevator specifications), I experienced full directional control during takeoff for the first time.

I recently heard from a previous instructor who had used my plane for training before I bought it, that many pilots had problems with low-speed directional control. This also explains why the brake discs and pads wore out prematurely, as I recently discovered at my own expense. 

A single test flight indicated that I may have lost one or two knots in cruise speed, but I really do not care if it means avoiding a scary and potentially dangerous takeoff scenario. I have sometimes had to drag the plane off the runway early to avoid hazards along the sides due to limited directional control, but today I had no such problems.

Jeff

Results of Testing Stolspeed VGs on a SportCruiser by Viktor in Switzerland

Viktor is a very experienced pilot, first with VGs on his Zenith 601HDS, and now on his new SportCruiser (PS-28) by Czech Sport Aircraft.

VGs were mounted on the wing in front of the ailerons with 60 mm spacing, and on the remaining wing with 90 mm spacing. VGs were also installed on the elevator, both top and bottom, with 60 mm spacing. Test flights were conducted on the same day at a total weight of approximately 550 kg, so the results with and without VGs are directly comparable. With VGs installed, it was immediately noticeable that the rate of climb was higher, and in cruise flight the nose was about three degrees lower, providing much better forward visibility.

At 3000 ft and maximum power, there was no measurable difference in maximum speed. Indicated airspeed (IAS) was 116 kt, and true airspeed (TAS) was 120 kt in both configurations. During takeoff, the aircraft lifted off the wet grass runway significantly earlier, and the landing roll distance was notably shorter.

Note: With maximum power and flaps up, the stall speed was 1 kt lower with VGs than with full flaps and no VGs. In all configurations, the aircraft with VGs remained stable, well-behaved, and easy to control. It is worth noting that even without VGs, the SportCruiser already has very docile stall characteristics.

Viktor reports that he will now rotate for takeoff at 30 kt and climb initially at 40 kt. For approach, he begins at 45 kt (Va) and aims for 40 kt over the threshold (1.3 Vs).

Performance Table