ALW Tapis

Shown below, a drawing of the wing section of the SP-2000. We will use the same section on the Tapas high wing.

alw wing section

Why have we included this drawing ? I hear you ask. Simple:

Out of the thousands of drawings  (service manual drawings, manufacturing, parts manual etc.) that make up the SP-2000 design documentation, this drawing epitomizes the strength of the SP-2000’s aerodynamics. Developed from experimentation and also based on years of experience gained from producing the GR and GA Australian LightWing, this section and wing shape is an absolute gem.

The SP will fly at Max takeoff wt. using only about 45 hp (4,300 rpm) to maintain altitude at a speed of about 60 kts with zero flap. The wing section just hangs in there. At this low speed, the angle of attack is very high but so little horse power is required to  remain aloft that its just staggering to watch. Pour on the coals, take the revs to 5,250, cruise RPM and you instantly rocket up to 112 kts. This wing section and the  unique  shape of our wing tips combine to give a great balance between low stall and high cruise. Come for a test fly, over the beautiful Northern Rivers, you will be surprised.

The variable pitch prop debate:

Originally back when we first designed the SP-2000, the applicable standard used to define LSA aircraft was the ASTM  set of rules and in 2005, this did not include a standard for propellers.  This was discussed with the RAAus tech manager and it was decided that we could introduce our own in-flight adjustable  prop, the VIP was borne.

It was a simple exercise made more so by the fact that I have been thinking about its design for the past 20 years or so. I had investigated other designs and so on. Mark Bergman ran a local CNC machine shop, drawings  and G codes were produced and the first prop carried me safely to Narromine in 2006 on its first flight. Now you might say that that was taking a bit of a risk but the design was fool proof and fail-safe and has been ever since.

Fast forward to 2012 and someone in the USA decided that aircraft fitted with in-flight adjustable props would or could compete with the few light trainers being manufactured in the USA, mmm, I can’t agree with this, but, nevertheless Variable pitch props were not included in the most recent LSA standards……

…..or to put it another way, they are currently not permitted.   My opinion of that… would make a coal miner blush, needless to say I disagree.

In-flight adjustment of your prop pitch contributes to the overall operational safety of the aircraft by providing faster cruise and better rate of climb, longer range due to better fuel burn and many other advantages including lower engine wear etc., it’s a no-brainer so lets all urge CASA to accept in-flight adjustable props providing they meet basic safety criterion such as:

1. If the mechanism fails, the pitch goes to a useable, safe, fine pitch;

2. The prop has a good history of operation, like 500 hours without problems;

3. The prop has been justified in standard engineering terms

4. Comes with operational, safety, service and repair manuals.

Come on guys, we have had 10 aircraft flying behind our props and I am not saying that we have had NO problems but the glitches we have had have all been minor and we have learnt and  improved the design as a result. The difference between cruising at 100 kts and 115 kts could mean the difference between getting home before last light or attempting a dangerous landing in the dark.

          Speed is good. So is a good rate of climb.

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