Subject: Eleventh in the Series--The Curtiss XP-11 Hawk

From: [email-masked] (Joseph F Baugher)
Date: 4 Sep 92 16:28:32 GMT

>From Joseph F Baugher <[email-masked]>

The Curtiss P-11 Hawk was an attempt to adapt the P-6 airframe to  the
new  600  hp  Curtiss H-1640 Chieftain two-row, 12-cylinder air-cooled
engine.

Three P-6 airframes (29-367, 368, and 374) were to be reserved for the
P-11  project.  A  similar  conversion  of an existing airframe to the
Chieftain engine had  already  progressed  further  along--a  standard
production Curtiss O-1B Falcon two-seat observation plane converted as
a flying test bed.  When fitted with the new Chieftain engine, the  O-
1B  was  redesignated  XO-18.  Flight tests with the XO-18 showed that
the new Chieftain engine was subject to chronic overheating  problems.
It  was  thought  that the problems with the Chieftain were insoluble,
and any further work on this engine was abandoned.  The  XO-18  flying
testbed  was  converted  back  into standard O-1B configuration with a
Conqueror engine.

With the failure of the Chieftain engine, any thoughts  of  proceeding
further with the P-11 project were abandoned.

Ser Nos 29-367 and 268 were subsequently completed  to  P-6  standards
(later  converted to P-6D) with the installation of Conqueror engines.
Ser No 29-374 was to have a completely different history.    It  later
became  the  YP-20 when a 650 hp Wright R-1860-9 Cyclone radial engine
was fitted.  The fin and rudder of the YP-20 were changed slightly  by
raising  the  division  between the rudder balance area and the top of
the fin by half a rib space.  The Cyclone radial  engine  installation
in the YP-20 proved to be unsatisfactory, and this engine was replaced
with the 700 hp V-1570-23 Conqueror liquid-cooled engine, mounted with
an new horizontal tail, and given the single-strut undercarriage first
tried out on the XP-22.  A tailwheel was used in  place  of  the  tail
skid.   The YP-20 was then redesignated XP-6E, to become the prototype
of the famed P-6E variant of the Hawk pursuit.

Sources:

  United States Military Aircraft Since 1909,  Gordon Swanborough  and
  Peter Bowers, Smithsonian Institution Press, 1989.

  The American Fighter, Enzo Angellucci and Peter Bowers, Orion Books,
  1987.

  Curtiss Aircraft: 1907-1947, Peter M. Bowers, Naval Institute Press,
  1987.

  "The Curtiss Army Hawks",  Peter  M.  Bowers,  Aircraft in  Profile,
  Doubleday, 1969.

Joe Baugher       AT&T Bell Laboratories    2000 North Naperville Road 
		  Naperville, Illinois 60566-7033.   (708) 713-4548