Subject: Fourth in the Series--The Boeing XP-4

From: [email-masked] (Joseph F Baugher)
Date: 25 Aug 92 14:39:33 GMT

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

In June 1925, before the first of the PW-9s ordered in 1924  had  been
delivered,  the  USAAS decided to have the 30th and last PW-9 aircraft
(Ser No 25-324) modified during production to test  the  high-altitude
performance  of  the  new  510  hp  Packard  1A-1500 turbosupercharged
engine.  This modification was considered important enough to  warrant
a  designation  change to XP-4 in accordance with the new system which
had just been adopted.

The XP-4 had a new, more aerodynamic wing  profile,  with  both  wings
being  of  equal  size  and  larger than those of the PW-9 in order to
provide the necessary larger area needed to lift the increased weight.
The  fuselage-mounted  pair of 0.30-cal machine guns were supplemented
by two extra 0.30-cal machine guns mounted in the lower wing, situated
far  enough  outboard  to  clear  the  propeller  arc.   A four-bladed
propeller was fitted.   The new engine made it necessary  to  redesign
the  cowling,  and the turbosupercharger was mounted externally on the
right-hand side.

The XP-4 was delivered to the Army at Wright Field for tests  on  July
27, 1927. The Packard engine did not prove to be sufficiently powerful
to compensate for  the  800-lb  increase  in  empty  weight,  and  the
performance  of  the  XP-4 was rather disappointing.  It did, in fact,
actually perform more poorly than did the standard PW-9, and the  XP-4
project  was  abandoned  after  only  four  hours of flying time.  The
airframe was surveyed on May 1, 1928.

Empty weight was 2711 lbs, with gross weight being 3603 lbs.   Maximum
speed  was  161  mph.   Initial  climb  rate was 2055 ft/min.  Service
ceiling was 22,000 feet, and range was 375 miles.

Sources:

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

  "Boeing F4B-4", Peter M. Bowers, in "Aircraft in Profile", Doubleday,
  1969.

  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.

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