This took place at the campus of University of California at Santa Cruz

While walking to class I hear a flooppping sound.  I looked up above the redwoods....maybe 20 feet above them....so say about 50-70 feet in the air I see a White plane.  Cessna sized....the plane was all white with with a a very large propeller in the front.
The plane made almost no sound, and was incredibly low to the ground.
On the left hand side from underneath a pod with a long antenna came from behind.  It was mounted under the wind.  Clynder probably about 8-10 feet long with a 3-4 foot antenna out the back.
The sound fo the twapping sound which was faint would be about once every 7/10ths of second.
The angle of the hill had the plane going North to South and downhill.  It was almost gliding.  There were no markings on the plane at all.  Zero....nothing on the tail or under wings.  I had a viewing angle from side...then I quickly ran to see it going away  I have basically assumed this was a sample of Military spy craft...as Lockheed has a development above the University.
If flying at night...and or painted black.....this craft could fly overhead of people or areas with very very little notice.
I am sure I saw this.....and lean towards earthly device...but would be classified.  It was like a glider with a huge propeller.  The body was more substantial than a glider...more like Cessana.
If you need more info....I would be fine with calling back after you email.  This was not anything that would fly from a normal airport....unless I missed hearing about a virtually silent plane.
We wonder whether the witness might have observed the YO-3A, a silent aircraft designed for use in Viet Nam.  It used to fly out of Moffett Field in San Jose.  It is built on a glider frame, and is similar in appearance to what the witness describes.  PD