Subject: Seventh in the series--The Boeing XP-7

From: [email-masked] (Joseph F Baugher)
Date: 30 Aug 92 12:08:21 GMT

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

The Boeing XP-7 was an attempt to adapt the PW-9 fighter  to  the  new
Curtiss  Conqueror  engine, and bore much the same relationship to the
PW-9 as did the Curtiss P-6 to the Curtiss P-1.

The Army was interested in seeing how much the performance of the PW-9
fighter could be improved by the use of the Conqueror engine, and they
ordered a single example on March 5, 1928.  The last Boeing PW-9D  off
the  production line (Ser No. 28-041) was experimentally fitted with a
new 600-hp Curtiss V-1570-1 Conqueror engine and was redesignated XP-7
under  the new system. The cowling had to be redesigned to contain the
larger radiator, giving a shorter, deeper nose than that of the PW-9D.
In  addition, the new model incorporated an all-duralumin tailplane, a
different type of tailskid, and a new control system for the ailerons.

The XP-7 was delivered to the Army on September  8,  1928,  and  began
flight  testing shortly thereafter.  The Conqueror engine proved to be
suitable for use in fighters, and an Air Corps specification was drawn
up  to  cover  the  building  of  four  service  test  P-7s.  However,
subsequent tests demonstrated that the performance of the XP-7 was not
much  better  than that of the standard PW-9D, maximum speed being 168
mph at sea level as  compared  with  163  mph  for  the  PW-9.   Since
Boeing's  radial-engined XF4B-1 had already reached nearly 170 mph, it
was concluded that the XP-7 project showed little promise and the Army
cancelled  its order for the four service-test P-7s.  After the end of
the tests, 28-041 was converted back to standard PW-9D configuration.

Performance of the XP-7 included a maximum speed of 167.5 mph  at  sea
level  and 163.5 mph at 5000 feet.  Initial climb was 1867 ft/min, and
an altitude of 10,000 feet could be attained in 7.1 minutes.  The XP-7
had  the  same armament as did the PW-9D, namely one 0.50 cal. and one
0.30 cal machine  gun  mounted  in  the  upper  fuselage  decking  and
synchronized to fire through the propeller arc.  Weights were 2358 lbs
empty, 3260 lbs. gross.

Sources:

  Boeing Aircraft since 1916, Peter M. Bowers,  Naval Institute Press,
  1989.

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

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