Subject: The Boeing PW-9

From: [email-masked] (Joseph F Baugher)
Date: 24 Aug 92 16:15:58 GMT

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

The Boeing PW-9 is not in the P-for-pursuit sequence, but some details
about it are needed for what is to come later.

In 1922, William Boeing of the Boeing  Airplane  Company  of  Seattle,
Washington  committed  his  company  to  a private venture which would
produce a fighter  that  would  compare  favorably  with  contemporary
British and French designs.  Heretofore, Boeing's only experience with
fighters had been in the production of the  Thomas-Morse-designed  MB-
3A.

The project was given the company designation Model 15.  The  fuselage
was  of  welded  steel  tubing  put together by arc-welding (a Boeing-
developed technique).  It was a single-bay biplane with tapered  wings
linked  by  an  N-strut.  The lower wing was shorter and narrower than
the  upper  wing.   The  wings  were  of  traditional   wooden   frame
construction  with fabric covering.  The Model 15 owed a great deal to
an examination of the Fokker D-VII, many examples of  which  had  been
brought to the USA under the terms of the Armistice.  The aircraft was
originally to have the same 300 hp Wright-Hispano engine that  powered
the  Boeing-built MB-3A.  However, early in the design process, it was
decided to switch to the 435 hp 12-cylinder liquid-cooled Curtiss D-12
(later  V-1150)  engine.  A tunnel radiator was mounted underneath the
nose.

Although the Army was interested in the Boeing Model 15, they were not
able  to  support  the project financially.  Money for any sort of new
military hardware  was  hard  to  come  by  in  the  early  'twenties.
However, on April 4, 1923, the Army signed a bailment contract for the
Model 15, in which they agreed to provide the armament and  the  power
plant  and  also agreed to test the airplane.  Boeing would retain the
airframe and all proprietary design rights.

The Model 15 made its first flight on April 29, 1923.  It was sent  to
McCook  field  in  June  1923  for  testing in the Army's 1923 Pursuit
Competition.  The Boeing design came into direct competition with  the
basically similar Curtiss PW-8. The Curtiss company had been so miffed
by the sudden appearance of  the  upstart  competitor  that  they  had
initially attempted to delay delivery of a D-12 engine to the Army for
installation in the Boeing design.

Both the Boeing and the Curtiss  aircraft  quickly  demonstrated  that
they  were  far  superior to the MB-3A which had just entered squadron
service.  On September 25, 1923, the Army had placed an order  for  25
Curtiss  PW-8s,  in  exchange  for  the Curtiss company's agreement to
participate in General Billy  Mitchell's  scheme  for  a  dawn-to-dusk
transcontinental crossing of the USA.

Although the Curtiss design was slightly faster, the Boeing design was
more  maneuverable,  more  rugged  and  easier  to  maintain.  Certain
features of the Boeing design such as the tapered wing and the  tunnel
radiator so impressed the Army that they asked Curtiss to try them out
on the  XPW-8A.   This  resulted  in  the  XPW-8B,  which  became  the
prototype for the famed Curtiss Hawk series of pursuits.

Although  the  Army  had  already  ordered  the  Curtiss   PW-8   into
production,  the Boeing company's gamble finally paid off on September
28, 1923.  On that day, the USAAS bought the Model  15  as  the  XPW-9
(Ser  No  23-1216)  and  ordered  two  more  prototypes  (Ser  Nos 23-
1217/1218).  The contract specified certain changes to be incorporated
in the second and third prototypes to make them conform to Air Service
specifications.  The second and third prototypes were delivered to the
Army on May 1, 1924.  A new Boeing-designed undercarriage with divided
axle was later tested on XPW-9 number 1, after initial  delivery  with
the Fokker-like straight axle.

The USAAS liked the Boeing design more than it did the Curtiss design,
and  the  USAAS  ordered  an  initial  batch  of 12 PW-9s (Ser Nos 25-
295/306) on September 19, 1924.  A second batch of  18  (Ser  Nos  25-
307/324)  was  ordered  on December 16, 1924.  The first delivery took
place on October 30, 1926.  The production PW-9 was based on the third
XPW-9  prototype, but differed from it in certain details.  The engine
cowling was better streamlined, the divided-axle undercarriage with 28
x  4  wheels was adopted as standard, and the center section fuel tank
of the prototypes was eliminated.  The wheels were changed in  service
to the larger 750 x 125 mm size.

The production PW-9 was powered by the Curtiss D-12  (V-1150)  liquid-
cooled  inline engine. Maximum speed was 165 mph at sea level, 159 mph
at 10,000 feet.  Initial climb rate was 1445 ft/min, and  an  altitude
of  10,000 feet could be attained in 7.9 minutes.  Service ceiling was
21,000 feet, and range was 390 miles.  Armament consisted of a pair of
0.30  cal  machine guns in the upper fuselage cowling, synchronized to
fire through the propeller arc. A heavier 0.50-cal machine  gun  could
be substituted for one of the 0.30-cal guns.  A 244-lb bomb load could
be carried under the fuselage.  Weights were 1936 lb. empty, 2835  lb.
gross.   The  PW-9s  were  shipped  to  US  bases  in  Hawaii  and the
Philippines.  One PW-9 was fitted at McCook Field with all-metal wings
for tests.

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  510 hp Packard 1A-1500 turbosupercharged engine.
The modification was important enough to warrant a designation  change
to XP-4 in accordance with the new system which had just been adopted.

Even though the production version of the third Curtiss  XPW-8,  which
had  been modified as XPW-8B with tapered wings and a tunnel radiator,
was built as P-1, the old PW-designation was retained  by  the  Boeing
design all throughout its production run.

The PW-9A was basically similar to the PW-9 but  was  powered  by  the
later Curtiss D-12C engine (later redesignated V-1150-1).  25 examples
were ordered on October 26, 1925.  Serials were 26-351/375.  The  only
noticeable  outward  change  was  that the landing wires were doubled.
The first delivery took place on June 19, 1926.

PW-9A Ser No 26-374 was  converted  to  AT-3  (Boeing  Model  68),  an
experimental  single-seat  advanced  trainer  powered by a 180 hp war-
surplus Wright-Hispano Model E engine.  A similar sort  of  conversion
was  made  by  Curtiss when the same type of engine was installed in a
Curtiss P-1A airframe, creating the AT-4. The  AT-3  was  considerably
slower  than  the  PW-9A,  since  the  weight  had not been reduced in
proportion to the lesser power.  Consequently, the  AT-3  trainer  was
neither  as  fast  nor as maneuverable as it could have been if it had
been initially designed for the purpose.  Therefore, the Army  ordered
no  production  examples  of  the  AT-3.   A  similar problem with the
Curtiss AT-4/5 series of single-seat advanced trainers led to an  Army
decision to convert most of them back to P-1 configuration.

The PW-9B was the designation given to the last PW-9A (Ser No. 26-375)
when  it  was  re-engined  with  a  Curtiss  D-12D  (V-1150-3) engine.
Fifteen  production  PW-9Bs  were  to  have  been  built,  but   their
designations were changed to PW-9C because of a change in the military
specifications under which they were ordered.  26-375 reverted back to
PW-9A  configuration  with a D-12C engine when it was delivered to the
Army in February 1927.

The PW-9C was the production version of the PW-9B  with  modifications
to  the fuel supply system, reinforced structure, and bigger wheels on
the undercarriage.  Outwardly, the PW-9C  was  similar  to  the  PW-9A
except  for  rearranged  flying  and  landing  wire  fittings.  It was
powered by the D-12D engine of the PW-9B.  An  initial  order  for  15
examples  was placed on June 19, 1926 (Ser. Nos. 26-443/457), followed
by an order for 25 more on August 18,  1926  (Ser.  Nos.  27-128/202).
The  first delivery took place on July 9, 1927.  Maximum speed was 163
mph at sea level.  Weights  were  1936  lb.  empty,  3170  lb.  gross.
Originally,  the  PW-9C  had the small unbalanced rudder of the PW-9A,
but that was changed in service (along with the  those  of  the  other
production  models) to the balanced type developed on the experimental
Navy FB-3.

The last PW-9C (27-202) was delivered with alterations  as  the  first
prototype  for  the  PW-9D.  The PW-9D was the final production model.
It was powered by the D-12D engine. It had a newly- designed radiator,
landing  gear  with the same size wheels as the first PW-9s, and wheel
brakes.  An aerodynamically-balanced rudder of  increased  area  first
tested  on  the  Navy  FB-3  was adopted as standard.  This rudder was
later retrofitted to most  earlier  PW-9s,  including  Cs  already  in
service.   Sixteen  examples  were ordered on August 12, 1927 (Ser Nos
28-026/041), the first delivery  being  April  25,  1928.   The  gross
weight  of  the PW-9D had crawled upward to 3234 lbs, as compared with
2835 lbs for the initial PW-9.  Maximum  speed  was  155  mph  at  sea
level,  and  an  altitude of 5000 feet could be attained in 4 minutes.
Service ceiling was 18,230 feet.  The last PW-9D (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 Navy versions of the PW-9 series bore the designation FB-1 through
FB-5.  They were basically similar to the PW-9, but with various naval
equipment such  as  tailhooks,  reinforced  fuselages,  and  beefed-up
undercarriages.   These  will  be  described  in  a  separate  article
(assuming that I find the time :-) ).

The last PW-9D in Army service was surveyed in February 1934.

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