Expert: Paul Soderman - 9/16/2009

Question
QUESTION: Why is it I can not find the glide ratio  of a piper PA 18 super club in a dead stick  configuration ?
The closest I can find is 7 to 1 or 10 to 1 .

ANSWER: I don't know.  Maybe it has never been in a wind tunnel, or maybe Piper never released the flight test data.  If you could find drag data for a similar aircraft you could get pretty close because all you need is lift-to-drag ratio and lift is almost equal to weight in a shallow glide.  This thing has a light wing loading so it should glide pretty well.  Check out the following for converting L/D to glide ratio:  http://www.grc.nasa.gov/WWW/K-12/airplane/ldrat.html.  If you have access to NASA and NACA reports you might be able to find drag or L/D data for a similar configuration.  Some libraries such as in engineering schools have NASA reports.  NASA also has some reports on line.

Paul

---------- FOLLOW-UP ----------

QUESTION:  Thank you Paul .Do you happen to know a similar configuration or
do you know the wing load per sq.ft. on the PA 18?

Answer
According to http://www.airliners.net/aircraft-data/stats.main?id=299, the PA 18-95 has a max takeoff weight of 910 lbs and the PA 18-150 has a max takeoff weight of 1750 lbs.  The wing area of each is 178.5 ft^2.  So the wing loadings of the two versions are 5.1 lb/ft^2 and 9.8 lb/ft^2, respectively.  That of course goes down as fuel is burned.  I don't know of a similar aircraft that has been documented without doing a literature search, which I will leave to you.
Paul