January 20, 1992 Canadian Aviation

Improving the performance and safety of your Cessna

Russell Lee, AOPA 26292

I am writing this article to outline to all Australian single engine’d Cessna owners a discovery that we were fortunate to make when traveling to New Zealand to investigate an undercarriage brace kit. The brace kit did not shape up to be what we were expecting, but a STOL kit, which was developed using a NASA flight test report, manufactured by a United States firm Flite Research and installed by Mt. Cook Airlines on all of their Cessna ski-planes, proved out trip well worth the effort.

The Sportsman wing kit comprises no moving parts, which minimizes any additional maintenance, once fitted. Flight test figures have shown a Cessna 170B at gross weight increase its glide distance from 7-1 to 13-1. Landing and take-off distances are reduced by approximately 35 percent due to the improved lift to drag ratio of the wing. This improved wing efficiency then translates to increased aircraft performance. Mt. Cook pilots claim it is equivalent to increasing the engine power by 30 horsepower on a Cessna 185.

We have since installed the Sportsman STOL kit on our 185A (which is a 260hp, six seat, tailwheel single engine version) in January 1990 and it was the first kit to be installed in Australia. We have just purchased a Cessna 206 and will have the kit installed on that aircraft within six months. Why bother to modify a perfectly good Cessna? More correctly, why bother modifying a wing that has served well for over 30 years.

You should first look at the type of flying that you are involved in. If you regularly fly your Cessna upside down using the original Cessna symmetrical wing to its full potential, I would not concern myself with the Sportsman wing because you will probably lose performance when flying upside down. If you enjoy the excitement of discovering how long it will take the rudder to level the wings after the aircraft has stalled, again this kit is not your cup of tea.

For all other single engine’d Cessna operators, particularly those with the original Cessna wing, this modification is something worth consideration.

The most noticeable feature is that the edge is extended forward a few inches, allowing the leading edge to be shaped into a drooped shape similar to a glider. This adds four square feet to the wing area and gives a marked improvement in the performance of the wing. Cessna did change the later model wings by putting an under-sided cuff. The design of the Sportsman wing is such that it is fitted as a fairing into the main wing. This modification is available on most single engine’d Cessna wing profiles.

The most important part of the modification is hidden between the back of the wing and the ailerons. This is a series of small folded pieces of sheet metal that are inserted under the wing skin, in front of the ailerons. This reduces high pressure air from leaking up through the gap of the ailerons and creating drag at high speed or rendering your aileron ineffective when you are at slow speeds. We have been so amazed by the difference that this gap sealing has made to our Cessna that we think that the CAA should make it an AD on all Cessnas.

The positive results from the gap sealing have meant that we always have full aileron response even when the airspeed is indicating 40 knots or less. This against all previous Cessna experience and I am sure that having this part of the STOL kit fitted alone would have saved many Australian lives over the years.

We have all been trained to use rudder to correct from a stall and I would predict that probably 90 percent of Australian pilots would do that at 5000 feet. How many would use rudder at 50 feet when one or both wings have just stalled and the ground is looming fast or you are about to hit a tree. With the Sportsman wing you can safely level or lift your wings from the stalled position using ailerons only!

This leads to the reasoning behind fitting the entire Sportsman kit.

We did not need a STOL performing aircraft to get in and out of a 3000ft strip. But we are human and like most other pilots, we do get tired and make mistakes and occasionally piston engines stop or lose power. With a stall speed of less than 40 knots, we think that you would survive a landing into nearly any terrain. With 15 knots headwind, you would have a touchdown speed of 25 knots.

We have found that our plane now stalls at between 10 and 15 knots slower than the figure published in the operation manual, depending on the flap setting. It now also has a TAS equaling that published, which it did not achieve before modification.

There are many details that can be quoted on performance improvements of the Sportsman kit, but if you like us, you will probably take these with a grain of salt, or probably would not believe until you actually see for yourself. If you are interested in the above information, go and fly a Cessna with a Sportsman wing on it and compare the difference. Both of ours are based in the Geelong area. We welcome anyone who would like to see our aircraft to contact us and try out our 185 or 206 when modified. A friend has modified his Cessna 172 and his is just as happy as we are. That aircraft is also based in the Geelong area.

The other aircraft in Australia that we know of is a 172 used for power line checking in South Australia. We know of many that have been modified in New Zealand.