Subject: Twelvth in the Series--The Boeing P-12

From: [email-masked] (Joseph F Baugher)
Date: 8 Sep 92 13:37:31 GMT

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

The Boeing P-12 was one of the best known Air Corps  fighters  of  the
entire  inter-war  period.   It equipped most of the Air Corps fighter
squadrons  during  the early  1930s.   Numerically, it  was  the  most
important of  all the  "between-wars"  pursuit  aircraft.   Here  is a
history of this important warplane.

The origin of the P-12  series  can  be  traced  back  to  a  pair  of
experimental aircraft produced by Boeing at company expense in hope of
replacing the PW-9 and the Navy's F2B and  F3B  fighters.   These  two
sires  of  the  entire  P-12/F4B  line  of  fighters  bore the company
designations of Model 89 and Model 89.   These  planes  departed  from
earlier  Boeing  construction practice in that they had fuselages made
largely of bolted-up aluminum tubing  construction,  rather  than  the
welded  steel tubing of earlier Boeing fighters.  They retained welded
steel tubing in the  engine  mounting  and  center-section  area,  but
bolted  square-section  dural  tubing  was  used  aft  of the cockpit.
Bolted instead of welded joints had been used in earlier fighters, but
the  steel  tubes had been bolted to tabs welded to the longerons.  On
these planes, the tubes were bolted directly to  one  another  through
dural gussets.

The wings of the Model  83/89  had  a  straight  rather  than  tapered
planform,  which  was  a departure from previous Boeing practice.  The
wings were constructed of two wooden box spars with spruce flanges and
mahogany  ply  webbing. The ribs were band-sawed from mahogany ply and
were fitted with spruce strips.  The upper wing was built  up  in  one
piece,  but  the  lower  wings  were constructed separately and bolted
together at the spar butts for installation as a  unit.   The  airfoil
section  was  the newly-developed Boeing 106 section.  The entire tail
unit was of semi-monocoque metal  construction  using  the  integrally
stiff corrugated skinning originally developed for the F3B-1.

Armament was provided by two 0.30-cal or one 0.30-  and  one  0.50-cal
machine  guns.   These  guns  were located in the top of the nose with
troughs in the paneling and synchronized to fire through the propeller
arc.  The powerplant was the 450 hp Pratt and Whitney R-1340-7 radial,
driving a ground-adjustable variable-pitch two blade metal  propeller.
No  cowling  was fitted around the engine, but streamlined "hats" were
positioned behind each cylinder.   A  55-gallon  auxiliary  fuel  tank
could  be  fitted between the undercarriage legs.  Up to 700 pounds of
bombs could be distributed under the lower wing and fuselage belly.

First to fly was the Model 83 which flew June 25, 1928 at Seattle  and
was delivered to the Navy at San Diego three days later.  The Model 89
was completed the next month and was shipped by rail to the Naval Test
Center  at Anacostia, Maryland on July 24.  It flew for the first time
there on August 7.  The two planes were virtually identical,  but  the
Model  83 had a spreader-bar undercarriage with diagonal strut bracing
to the middle of the bar, whereas the Model 89 had a split-axle  gear.
The  89  had a 500-lb bombrack between the undercarriage legs, whereas
the 82 had an arrester hook.  Although not Navy  property,  these  two
planes  were  referred to as XF4B-1 for administrative purposes during
the testing.  Since both aircraft  were  Boeing-owned,  they  did  not
carry  military  markings.   However,  they  did  not  carry the civil
registrations that were allocated to them.

Both aircraft were originally powered by "long-nosed" R-1340B  engines
which  were  supposed  to  improve  the aerodynamic shape of the nose.
They were soon replaced by the standard dash-7  engine  with  no  more
than marginal effect on performance.

Flight testing of these two prototypes showed that  they  outperformed
all  serving  fighters.  As a result of testing of the two prototypes,
the Navy ordered 27 production F4B-1s  (serial  numbers  A-8130/8156).
Navy  bought  both  the  Model  83  and  89  on June 19, 1929, and the
designation XF4B-1 became official.  Both prototypes were returned  to
the  factory  after  testing  for  modification  to  the  standards of
production F4B-1s.  These two planes were then  assigned  Navy  serial
numbers  immediately  ahead  of those in the F4B-1 contract (A8128 for
Model 89 and A8129 for Model 83).

F4B-1  #A8133  was  modified  as  a  special  executive  airplane  for
Assistant  Secretary  of  the  Navy  David S. Ingalls, the Navy's only
World War 1 ace.  It was stripped of all armament, fitted with a  ring
cowl  and  painted  with  the  special blue fuselage coloring of Naval
executive aircraft.  This plane was designated F4B-1A.

Although the Model 83/89 had both been  submitted  to  the  Navy,  the
Model  89  was  loaned  to and tested by Army pilots at Bolling Field,
which was located  just  on  the  other  side  of  the  airstrip  from
Anacostia.   Like  their  Navy  counterparts,  the  Army  pilots  were
impressed.  As a result of the Army pilots' reports on the  Model  89,
Boeing  received  a  contract  for  ten  P-12s (Ser Nos 29-353/362) on
November 7, 1928.  These airplanes bore  the  company  designation  of
Model 102.  This order by the Army was quite unusual, because they had
not even tested a prototype, simply having "borrowed" the Navy's plane
for the tests.

The first nine P-12s were similar to the F4B-1 naval version with  the
exception  of the deletion of the arrester hook and other purely naval
equipment.  The first P-12 completed was  handed  over  to  Air  Corps
Captain  Ira  C.  Eaker  on  February  26, 1929 for use in a good-will
high-speed  flight  to  Central  America.   The  first  flight  of   a
"standard"  P-12 was on April 11, 1929. The last example was delivered
on April 26.

The basic P-12 was the only model  in  the  Army  series  to  use  the
tapered  ailerons  of the prototypes.  Production P-12s were delivered
with fairings aft of the engine cylinders, but cooling problems led to
their  removal  soon  afterwards.   The P-12 was powered by the 500 hp
Pratt and Whitney R-1340-7 radial.  Maximum speed was 158 mph  at  sea
level  and  171  mph  at 5000 feet. Initial climb was 2080 ft/min.  An
altitude of 10,000 feet could be attained  in  5.8  minutes.   Service
ceiling was 28,200 feet and range was 520 miles. Weights were 1758 lb.
empty,  2536  lb.  gross.  Armament  was  the  same  as  that  of  the
prototypes--a  pair  of  0.30-cal  or  one  0.50-cal  and one 0.30-cal
machine guns.

The last P-12 (Ser No 29-362) was  delivered  as  the  XP-12A  (Boeing
Model  101).   It incorporated various refinements suggested to Boeing
by Army pilots.  The differences included the use  of  Frise  balanced
ailerons  with  hinge lines lying parallel to the wing spar, a shorter
undercarriage, a long-chord engine cowling, redesigned elevators,  and
a  castoring  tail  skid  in place of the fixed skid of the P-12.  The
first flight of the XP-12A took place on  April  11,  1929.   However,
after  only  four  hours  of  flying,  it  was  destroyed  in a midair
collision with another P-12 at Wright Field on May  18.  Nevertheless,
evaluation  of  the  remaining P-12s sufficed to eliminate some of the
minor snags.

The P-12B was  an  improved  version,  owing  a  great  deal  to  Army
experience  with  its nine P-12s. On June 10, 1929, Boeing received an
order for 90 P-12Bs, the largest single aircraft order placed  by  the
Army  in peacetime thus far.  Serials were 29-329/341 , 29-433/450 and
30-029/087. The company designation for the P-12B was Model 102B.  The
P-12B  could  be  distinguished  outwardly  from the P-12 by the Frise
balanced ailerons as originally fitted to the XP-12A, by  the  revised
elevators, and by the use of slightly larger wheels.  The landing gear
and uncowled engine were  the  same  as  on  the  P-12  (omitting  the
cylinder  fairings),  but  some  P-12Bs  were  retrofitted  with  ring
cowlings developed on later versions. Rail delivery of  dismantled  P-
12B  aircraft  began  on February 1, 1930 The first P-12B flew May 12,
1930, and the last example was delivered on May 17.

The P-12B was somewhat heavier than  the  P-12,  and  its  performance
suffered  accordingly.  The engine was the 500 hp Pratt and Whitney R-
1340-9.  Weights were 1956 lb. empty, 2638 lb. gross.   Maximum  speed
was  166 mph at 5000 feet.  Initial climb rate was 2040 ft/min Service
ceiling was 27,450 feet, and range was 540 miles.   The  armament  was
the same as that of the P-12.

The P-12C was an improved P-12B with a later  engine  and  some  minor
refinements.   The  Army  ordered 131 P-12Cs on June 2, 1930.  Serials
were 31-147/277.  The company designation for the P-12C was Model 222,
and  the  the naval equivalent of the Army P-12C was F4B-2.  The P-12C
differed from the B-version in  having  an  engine  ring  cowl  and  a
spreader  bar  undercarriage  similar  to  that fitted to the original
Model 83.  This undercarriage arrangement had been first tried out  on
the experimental XP-9. Wingtip navigational lights were provided.

Delivery of dismantled P-12C aircraft to the  Army  began  August  30,
1930  and  was  completed  on  February  12, 1931.  The first recorded
flight of a P-12C was on January 30, 1931.  In  the  event,  only  the
first  96  examples  of  the original order (31-147/242) were actually
completed as P-12Cs, the remaining 35 being completed as  P-12Ds.   In
addition,  Ser Nos 31-152/154,156,157,159/161,175,195,209/212,233, and
234 were later converted to P-12D  standards  after  having  initially
been delivered as Cs.

The engine powering the P-12C was  the  450  hp  R-1340-9  (SR-1340D).
Maximum speed was 175.5 mph at 10,000 feet and 176.5 mph at sea level.
Initial climb was 1410 ft/min, service ceiling was  26,200  feet,  and
range was 580 miles.  Weights were 1938 lb. empty, 2630 lb. gross.

The Navy equivalent of the P-12C was the F4B-2.  Serial  numbers  were
8621/8639 8791/8809.

Only the first 96 examples of the original  P-12C  order  (31-147/242)
were  actually  completed as P-12Cs.  The last thirty-five examples of
the original P-12C  order  were  completed  as  P-12Ds,  beginning  on
February  25,  1931  and ending on April 28.  Serial numbers of the Ds
were 31-243/277.  The company designation of the P-12D was Model  227.
Deliveries of the P-12D began on February 25, 1931, and were completed
on April 28.  The first flight of a P-12D was made on March 2, 1931.

The P-12D differed only internally from the P-12C.  On the P-12D,  the
ignition  harness was on the front of the engine rather than behind it
as on the P-12C.  In addition, the cowling support struts  visible  on
the  P-12C  were  not used on the P-12D.  The P-12D was powered by the
more powerful 525 hp Pratt and  Whitney  R-1340-17.   Performance  was
improved.   Maximum  speed  was 178 mph at 7,000 feet and 176.5 mph at
sea level.  An altitude of  10,000  feet  could  be  attained  in  5.8
minutes.   Initial  climb  was 1410 ft/min, service ceiling was 25,400
feet, and range was 475 miles.  Weights were 1956 lb. empty, 2648  lb.
gross.

Both C and D models were later retrofitted with P-12E  vertical  tails
by the Army.

The best-known version of the P-12 series was the  P-12E.   The  P-12E
had  its  origin  in  the private venture Model 218 which flew for the
first time on September 29, 1930.  The Model 218 was  a  company-owned
aircraft intended to develop new features for the P-12/F4B series.  It
was essentially a P-12B with a semi-monocoque metal fuselage structure
similar  to  that  of  the  experimental XP-9 monoplane. It had a tail
wheel in place of the tail skid of the earlier  versions.   A  pilot's
headrest  was  provided behind the cockpit.  The fin and rudder of the
Model 218 were originally the same as that of the P-12B, but they were
soon   enlarged   to  a  more  rounded  form.   An  experimental  Army
designation of XP-925 was  assigned  during  testing  with  a  R-1340D
engine  and  was  changed  to  XP-925A  when  an  R-1340E  engine  was
installed.  Empty weight increased to 1954 lb, gross weight  was  2694
lb.  Speed  with the altitude-rated R-1340D engine was 195 mph at 8000
feet.  The Model 218 was temporarily fitted with  wheel  spats  in  an
attempt to obtain additional speed.

The Model 218 was tested by both the  Army  and  Navy  under  bailment
contracts.   During  the  test  program,  the Model 218 bore the civil
registration X66W.  The Model 218 was sold to China after the  testing
was  completed.   Once  there,  it was flown by the American volunteer
pilot Robert Short.  In an  air  battle  over  Shanghai  in  1932,  it
destroyed  two  out of three attacking Japanese fighters before it was
shot down.

The Army ordered the Model 218 into production as  the  P-12E  (Boeing
Model  234).   135 P-12Es were ordered on March 3, 1931.  110 aircraft
(31-553 to 586 and 32-1  thru  76)  were  delivered  as  such  between
September   19  and  October  15  of  1931.   They  bore  the  factory
designation of Model 234.  The naval equivalents were designated F4B-3
and F4B-4. The first flight of a P-12E took place on October 15, 1931.
The P-12E was the most widely used and long-lived of the Army  series.
It  used the new fuselage and tail surfaces of the Model 218, but most
other components were essentially those of the P-12D.  The  P-12E  was
initially  fitted with a tailskid, but it was replaced in service with
a tailwheel as  first  tried  out  on  the  Model  218.   P-12Es  were
originally  built with flotation gear in the upper wing as on previous
models, but this feature was deleted in service and replaced  in  most
examples  by  a  rubber  life raft for the pilot stored in an enlarged
"Panama" headrest, so named because it was  originally  developed  for
use  in  the  Canal  Zone  area.   This  gave  the P-12E a distinctive
"hunchback" appearance.  The maximum speed was 189 mph at 7,000  feet,
and initial climb was 1920 feet/min.  An altitude of 10,000 feet could
be attained in 5.8 minutes.  Weights were 2014  lb.  empty,  2701  lb.
gross.  Service ceiling was 31,400 ft and range was 585 miles

The last 25 aircraft of the March 1931 order (Ser No 32-077/101)  were
powered  by 600 hp R-1340-19 engines, rated for maximum performance at
10,000 feet, 3000 feet higher than the -17  in  the  P-12E.   As  this
significantly  altered the performance characteristics, these aircraft
were designated P-12F (Model 251). Deliveries of the P-12F took  place
between  March 6 and May 17, 1932.  The last ten P-12Fs had tailwheels
rather than tailskids, but tailwheels were later  retrofitted  to  all
the  E's  and  the  F's.   Many P-12Fs were fitted in service with the
"Panama" headrest.  The maximum speed was 195 mph at 10,000 feet,  and
initial  climb was 1784 feet/min.  An altitude of 10,000 feet could be
attained in 4.2 minutes.  Weights were 2035 lb. empty, 2726 lb. gross.
Service ceiling was 31,400 ft and range was 300 miles

The last aircraft in  the  P-12  batch  (Ser  No  32-101)  was  fitted
experimentally with an enclosed cockpit and sliding canopy.

The production history of the P-12 ends with the F-version.  All later
versions were produced by "one-off" conversions of earlier variants.

P-12E Ser No  31-553  was  redesignated  XP-12E  on  October  1,  1931
immediately  after  delivery.   This  was  used to identify a standard
example of the E-series withdrawn from service for test work, and  was
not  considered  as a prototype.  It was later restored to service and
resumed its P-12E title.

The XP-12G was produced by the conversion of P-12B Ser  No  29-329  by
fitting  it  with an experimental Y1SR-1340G (R-1340-15) radial engine
equipped with turbosuperchargers  and  ring  cowlings.   Later,  other
experimental  versions  of  the  R-1340  were fitted to this airframe.
After the series of tests were over, the plane  reverted  to  standard
P-12B configuration.

P-12D Ser No 31-275 was modified  as  the  XP-12H  to  accommodate  an
experimental  Pratt  and Whitney GISR-1340E geared radial engine and a
P-12E tail.  This engine arrangement turned out to  be  unsatisfactory
and the aircraft was returned to P-12D configuration in June 1932.

P-12E Ser No 32-042 became P-12J with installation of a 575  hp  Pratt
and Whitney SR-1340H (R-1340-23) engine and a special bombsight.  This
engine improved the service ceiling but  gave  few  other  advantages.
This  plane  became  one of the seven YP-12Ks after yet another engine
change.

The XP-12E, the P-12J, and five standard P-12Es (32-033,  -036,  -040,
-046,  and  -049)  became  YP-12Ks  when  SR-1340E  engines  with fuel
injection were installed for service trials. One YP-12K was flown with
a  combination  of  ski-wheel  chassis.   All  reverted  back to P-12E
standards in June, 1938.

YP-12K 31-553 (ex XP-12E) was redesignated XP-12L on January  2,  1934
when  fitted  with  a Type F-7 turbosupercharger.  It reverted back to
YP-12K in February 1937 and then to P-12E in June 1938.

Boeings were used by the 17th Pursuit  Group  (34th,  73rd,  and  95th
Squadrons)  at March Field, and the 20th Pursuit Group (55th, 77th and
79th Squadrons) at Barksdale Field.   The  older  P-12s  equipped  the
overseas  units; the 3rd Squadron in the Philippines, the 16th Pursuit
Group (24th, 29th , 745h, and 79th Squadrons) in the Canal  Zone,  and
the  18th Pursuit Group (6th and 19th Squadrons) in Hawaii.  The P-12E
and F remained in service with front-line pursuit units until replaced
by  Boeing P-26s in 1934 and 1935.  Thereafter, they were relegated to
secondary roles and to  training  duties.   Most  P-12E  and  Fs  were
grounded  and assigned to mechanics's schools in 1941.  After American
entry into the war, twenty-three miscellaneous P-12s (P-12C:  31-151,-
154,-209,-210;  P-12D:  31-245, -258; P-12E: 31-561,-564,-576,32-010,-
013,-025,-033,-040,-041,-044,-046,-048, -057,  -066,-069,-074;  P-12F:
32-85) were handed over to the Navy for use as radio-controlled target
aircraft.  These were all referred to by the Navy  as  F4B-4A,  the  A
designating  their former Army status.  They were assigned Navy serial
numbers 2489/2511 in the second series.  Most were  shot  down  during
training exercises.

P-12E 32-017 which had been given to civilian schools in  1940-41  was
later  obtained  by  the  Ontario  Air  Museum  in California from the
California Polytechnic Institute.  It was slowly restored  to  display
conditions and was made airworthy in 1962 under the civil registration
N3360G.  It was painted as a Navy F4B-3 for Navy celebrations of Armed
Forced  Day  in  1961.   In  1962,  it  was  repainted  to its correct
configuration as a P-12E.   It  is  now  based  at  the  Museum's  new
facilities at Chino Airport, California.

Ser No 31-559 was a former ground school P-12E which was acquired by a
private  owner  and  donated  to  the  US  Air Force Museum at Wright-
Patterson AFB near Dayton, Ohio.  It was rebuilt and put on display in
the markings of the 6th Pursuit Squadron which it once carried.  Yours
truly saw it there in May of this year.  Quite a thrill!

Sources:

  American Combat Planes (3rd edition), Ray Wagner, Doubleday, New York,
  1982.

  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