Zenith 601 HDS

Zenith 601HDS Page

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Experiences of Viktor Stausak in Switzerland

with Stolspeed VGs on his 601HDS

Stolspeed VGs on Viktor's HDS

08.10.2007

Hello JG

I tested my Zenair 601 HDS with your VGs installed.

Engine is 80hp Rotax 912.

Prop is Woodcomp 3-blade in flight adjustable.

Weight 545kg.

I do have a new airplane!!!!!!!!

I’m absolutely impressed and surprised about the results, never expected!

It is a big advantage for safety and operation. I demonstrated my new airplane to 601 flyers and to the German dealer of Zodiac. My test results with fotos go to all experimental builders in Switzerland , later in Germany and England

. And I hope to the ZENAIR homepage. Every one is impressed and will install your little things.

On each wing I installed 38 VG’s and 33 VG’s on each elevator (lower side), a total off 142 VG’s, according your instructions.

The following results are not yet the final results, but very accurate.

Take-off: Lift-off speed now 40 kt (before above 50 kt)

From high altitude airport samedan LSZS, witch is at 5600 ft and OAT 15°C the lift-off speed was 42 kt with 2 persons and 72 lt fuel.

Take-off distance now with 2 persons and 50 lt fuel approximately 130 m (means more than 20% reduction)

Rate off climb much better, in all speed range

Cruise-speed with max. power the same as before. You never use this.

With typical cruise-power-settings between 12 lt/h and 15 lt/h an increase for approximately 2-3 kt in Speed with the same power setting. But very impressive is, the nose is 3° lower (less drag). To find out the reasen I installed “stallfäden” on the wing, as you can see on the fotos, and we do now the same on 601 HDS without VGs.

Stall-speed with max. power 35 kt with very high angle off attack, power off 40 kt (very comfortable)

I can fly 360° turn with 58 kt IAS in only 15 sec., witch gives a circle diameter of less than 150 meters.

I’m impressed, how much better the flight-characteristics at high altitude up to 13’500 fts are. A very big change! The cruise at very high altitude is much better.

My approach speed is now 55 kt (before 65 kt) and touch down below 50 kt. Limited by tail contact.

The flight controls are now much more comfortable, especially the elevator.

The safety margin is improved considerably over the entire flight envelope.
To install VGs is the best modification I ever made, even for a low investment. The only mistake I made, not to install VGs 800 flight hours earlier.

Best regards

HB-YKViktor

Tuft testing over the Alps with Stolspeed VGs.

Note the very high angle of attack and the clean airflow.

An identical HDS without VGs.

Note the disrupted airflow at a lower angle of attack.

Another 601 wing, this time with VGs only on the outer portion.

Note the difference in airflow!!

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Viktor installing Stolspeed VGs on his HDS wing.

Viktor is a keen and experienced experimenter and flyer.

See photos of some of his adventures.

Flying the Swiss Alps

Viktor's Sahara Desert Flight

Viktor's North Cape Flight

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601 HDS

Having installed the VGs last Saturday when temp was 51 degrees F, the weather finally allowed me to take a test flight. It was, however, cut short to 20 minutes when the ceiling dropped to 2500 ft. Don't like doing stalls starting at 2000 ft ASL! As a base, my 601HDS with Rotax 912, Arplast in-flight adjustable prop, radiator and oil cooler inside the cowl and some drag reducing fairings normally cruises at 120 mph IAS at 26 inches manifold pressure and 5500
rpm. I re-checked stall speed before VG installation at 3000 ft and air temp of 49 degrees F as being "stall buffeting at 58 mph IAS (all speeds IAS) and full stall at 56 mph". Test conditions air temp was 40 degrees F. Altitude 3000 ft. Atmos. pressure approx equal. Takeoff weight equal to test flight. First impression was an increase in climb rate at 80 mph. Rough attempt to measure would be an extra 200 ft/min. Pre-stall buffeting now begins at 54 mph and is significantly more apparent. Full stall at 52 mph, no more abrupt than without the VGs. There appears to be no measurable difference in cruise speed - the 120 mph. Since I only made one landing I will make no comment as to stability, but greased it on using my normal over the fence speed of 75 mph. No VGs parted company.

One thing I did not mention - slow flight was significantly more stable, with an incredible angle of attack. With 3000
rpm on the 912 I was climbing very slowly at 55 mph with the nose pointingup at what seemed like 45 degrees.
So far, certainly meeting expectations!

I installed the VGs at the 10% line per John's instructions last fall and
got the results I posted above.
After a new paint job I reinstalled the VGs at the 18% line. My logic was
that with the airfoil of the zodie wing, the air would start to detach
further back.
For many reasons, so far I have not done any real exploration of the
envelope, but one thing has really stood out. When landing at my previous
75 mph indicated the plane would float much more and not sink until below 60
mph indicated. With a passenger, the previous harder touchdown if I forgot
to add 5 mph to the speed has gone. The plane seems to be significantly
more controllable at the landing speeds. Cruise speed has not been affected
at all. Stall is maybe a bit lower than with the 10% application.
I've had absolutely no problem with them falling off. They were not
difficult to remove. Just needed to be cleaned before reinstall. The glue
rubbed off the wings with the fingers.
For me, they are a well worthwhile improvement.

Dave, Ontario, Canada

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The following is a link to a wesite created by Peter Chapman, in Canada, regarding the results of his testing of Stolspeed VGs on his 601HDS. There are videos and still photos of tuft testing there.

http://sites.google.com:80/site/601cgzdc/Home/Tuft-testing--vortex-generators

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