ITF:  STOL Sense

 

Our design philosophy for STOL planes may seem subtle, since our planes are void of any fancy high lift devices.  But they are not lacking the most important high lift device, the wing. Add  a set of big flaps you have a potent STOL machine, provided a few other factors are incorporated. Making sense of what is a good idea into a great idea for a STOL plane is pretty easy once you understand the design factors behind the choices we have made.

 

The Wing is the Thing

Like there is no replacement for cubic inches in engine, there is no replacement for square feet in wings. Of course you can design a small wing STOL plane, adorn it with every high lift device known to man and get pretty impressive results in thick cool air. But what happens to such a plane when you load it up to gross or beyond and try taking off from a high mountain strip? Unless you have a very light and powerful engine ( something like a Rotax 914 ) you may be in for a surprise. All the stuff that makes lift also makes drag, and that requires power. Power that has dropped off as much as 40% due to the high density altitude. The other penalty is speed. Drag and weight take away speed. I have heard many say they do not care if the plane is slow, they prefer  STOL over speed, but why not have both? Our planes cruise typically 20 MPH faster than similar craft. You have greater range, need less fuel, and have the margin of fuel to explore the places  from the air you are visiting. This became pretty obvious in Alaska. We had sold some SLSA Couriers to an outfit using  Super Cub type planes. When they discovered the Couriers out ran the Cubs on less fuel, suddenly speed was important. It adds a safety margin to the overall operation by having added range or time aloft.

 

The better alternative is a clean wing, with more chord, and square feet. And around 6:1 aspect is fine. Why this works is angle of attack. It is simple physics, if you can fly with a wing at the least angle of attack you will have less drag. The larger wing does this with some added benefits. Number one you are not hanging the plane on the prop during take off or landing. Hanging a plane on the prop to make a short take off invites disaster if there is a power interruption. Whenever you need power to land or take off  you most likely are flying below the power off stall speed. Hanging it on the prop on landing has the same risk with the added issue of pilot work load.  Taking off or landing with the nose radically high in the sky is fun to watch, but is a risk you should not have to take. With a lower angle of attack and an approach speed just above power off stall you still have decent glide and low sink in the even of power loss.  

 

Keep it Light

Every pound counts, heck every ounce counts. We build an inherently light plane. That is one advantage tube and cloth affords without becoming to high priced. High lift devices add weight, build time and failure modes you may not be able to fly out of. Keeping it light is tough for some builders, but sticking to the plan will give as promised results. We approach weight reduction in our kits with the attitude that everything is suspect, when you build, keep that in mind, even your choice of colors will vary the outcome.

 

Power Up

Going up in horsepower does not always mean improved performance at high density altitudes. It is still about power to weight. Unless you can significantly increase the power to weight, and retain that increase,  the bigger heavier engine may not pay off.  At high density altitude the non-turbo heavier engine still weighs as much as it did at sea level, but now has less power. A great real life example of this was at Johnson Creek a few  years ago.  Two 914 powered Couriers were out performing 180 HP Super Cub type planes. The Couriers still had 115 HP, so at gross the power to weight was 11.4 pounds. The 180 HP planes were down to 127 HP, but since they grossed higher (1600) the power to weight was 12.6. To get the Super Cub to the same power loading the gross would have to drop to 1447. That may explain why a couple of wives were left behind!

 

In the end simple and light is good, and simple, light, practical, and powerful is great. Stay safe, and stay into the flight.

 

 

 

 

 

ITF:  REMOTE CHARGING POST

 

A chaging post makes jump-starting a plane much easier!  The post is made of CNC machined nylon, and houses the positive pole direct to the battery.  There are plenty of negative contact points, any bolt head, within easy reach of the charger cable, should work.  On the S-19, we hook into one of the bolts that attach the nose gear pylon.  This kit is for sale and in stock!  It's a perfect accessory for winter time flying!  Call today to order!  Stay safe, and stay into the flight.