Subject: Number Seventy in the Series--Douglas P-70 Nighthawk

From: [email-masked]
Date: 18 May 93 16:33:53 GMT

>From [email-masked]

The Douglas DB-7/A-20 Boston/Havoc was one of the most popular and 
effective light bombers of the Second World War.  A total of 7478 of 
these bombers were built, and they served with the USAAF under the 
designation A-20 and with the RAF under the designation *Boston*.  
However, it is a little-known fact that there were night fighter 
versions of this attack plane which served with the RAF under the name 
*Havoc* and with the USAAF under the designation P-70.  

First, a little background on the DB-7 is in order.  The origin of the 
DB-7/A-20/Havoc/Boston series can be traced back to 1936, when Donald 
Douglas, Jack Northrop, and Ed Heinemann and a group of Wright Field 
technicians drew up a set of requirements for a twin-engined light 
attack bomber.  The initial Douglas proposal bore the designation 
Model 7A, and was a two-seater powered by a pair of 450 hp engines and 
capable of achieving a maximum speed of 250 mph.  However, the 
experience of the Spanish Civil War resulted in the replacement of 
this design with an even more advanced conception, the Model 7B.  

On January 1, 1938, Jack Northrop left the Douglas subsidiary to 
strike out on his own, and Ed Heinemann took over as chief designer on 
the Model 7B project.  The Model 7B made its first flight at the end 
of 1938.  Powered by a pair of 1100 hp Pratt & Whitney R-1830 Twin 
Wasp engines, the Model 7B featured a shoulder-mounted wing and had 
retractable dorsal and ventral turrets.  The Model 7B featured 
interchangeable noses--a "bomber" nose with a transparent bombardier 
position and an "attack" nose with four 0.30-inch machine guns for 
ground strafing.  

The first flight of the Model 7B coincided with the arrival in the USA 
of the French Purchasing Commission which was seeking aircraft for the 
Armee de l'Air.  They were sufficiently impressed by the Model 7B that 
they ordered one hundred examples on February 15, 1939.  This was the 
first solid order for the Douglas design.  170 more examples were 
added to the order in October, following the outbreak of war in 
Europe.  

However, the French insisted on a large number of changes to prevent 
the aircraft from becoming obsolescent in the rapidly-evolving 
European market.  So many changes were required, in fact, that the 
revised design was a virtually new aircraft.  The modified version for 
the Armee de l'Air was designated DB-7 (which stood for Douglas Bomber 
7).  

The DB-7 retained the wing geometry of the 7B, but had a redesigned 
and larger fuselage.  The engines were enclosed in revised nacelles 
that were attached beneath the wings, whereas the engines of the 7B 
prototype had been enclosed in nacelles partially extending above the 
wings.  The DB-7 was fitted with a glazed nose incorporating a 
bomb-aimer's position and housing four forward-firing 7.5-mm machine 
guns.  Defensive armament consisted of a flexible 7.5-mm machine gun 
in a dorsal position and a similar weapon firing through a ventral 
hatch.  No provision was made in the DB-7 for the installation of an 
unglazed nose containing a battery of forward-firing guns.  Most of 
the internal equipment was of French manufacture, with the instruments 
being calibrated metrically.  

The first DB-7 flew on August 17, 1939, and the first deliveries to 
France were made in October.  The first one hundred DB-7s were powered 
by a pair of 1000 hp Pratt & Whitney R-1830-SC3-G radials with 
single-speed superchargers.  The additional 170 DB-7s differed from 
the earlier batch of one hundred in having two 1100 hp Pratt & Whitney 
R-1830-S3C4-Gs equipped with two-speed superchargers.  

The DB-7s bore the French military designation of DB-7 B-3 (the B-3 
meaning "three-seat bomber").  They were operated by the Armee de 
l'Air starting from January 1940.  Late production DB-7s were fitted 
with self-sealing fuel tanks and included some armor protection for 
the crew.  By the time of the fall of France, about half the DB-7 
order had been completed, but many of these aircraft never got to 
France since they were en route at the time of the collapse.  Some 
sixteen DB-7s from the first production batch were diverted for use by 
Belgium's Aviation Militare.  In the event, France actually only 
received about seventy DB-7s out of the 270 that it had ordered.  Only 
a very few of these actually saw any combat.  

After the fall of France, the United Kingdom took over the DB-7 order, 
including those aircraft intended for Belgium.  The early DB-7s 
powered by 1000 hp R-1830-SC3-G engines were designated Boston I.  RAF 
serials were AE457 to AE472 and DK274 to DK277.  The throttles had to 
be modified so that their operation was reversed--being pushed forward 
to open rather than close as was the French fashion.  These Boston Is 
were considered as being unsuitable for combat, and were restricted to 
training and other non-operational duties.  

The ex-French contract DB-7s powered by the more-powerful 1100 hp 
R-1830-S3C4-G engines were designated Boston II.  The French had 
originally intended the DB-7 for use as a short-range tactical attack 
aircraft, and these former French machines had too short a range for 
the RAF to be able to use them as light bombers to reach targets in 
Europe.  At that time, the RAF was in desperate need of an aircraft 
suitable for night fighting and intruder duties and which was also 
capable of carrying the heavy and cumbersome airborne interception 
radar that was available at the time.  The Boston II, powered by a 
pair of 1200 hp Pratt & Whitney R-1830-S3C4G Twin Wasp engines, had a 
good performance and had a large fuselage and appeared to fit the 
bill.  The decision was made to modify the Boston II aircraft (as well 
as some Boston I aircraft which had been reengined) for night intruder 
and night fighting duties.  

There were two basic versions, an intruder version with a three- man 
crew, a glazed nose, five 0.30-inch machine guns, and 2400 pounds of 
bombs, and a night fighter version with an early AI Mk.IV radar, a 
two-man crew, and eight 0.30-inch machine guns.  These conversions 
were named *Havoc I* by the RAF.  

The first Boston II -> Havoc I conversion was carried out by the 
Burtonwood Aircraft Repair Depot during the winter of 1940/41.  More 
than a hundred of these conversions were completed during the next few 
months.  In all, 181 aircraft were converted to Havoc I configuration.  
Included in this total were some Boston I aircraft which had been 
reengined.  Serials were AW392 to AW414, AX848 to AX851, AX910 to 
AX918, AX920 to AX975, BB890 to BB912, BD110 to BD127, BJ458 to BJ501, 
BK882, BK883, BL227, BL228, BT460 to BT465, BV203, DG557, DG555.  

The intruder version of the Havoc I had armor protection for its three 
crew members and was equipped with flame-damping exhausts for night 
operations.  It featured four forward-firing 0.303-inch Browning 
machine guns in the lower part of the glazed fuselage nose, plus a 
single 0.303-inch Vickers flexible machine gun in the rear cockpit.  A 
bomb load of up to 2400 pounds could be carried.  

For pure night fighting duties, the Havoc I was fitted with a "solid" 
nose housing an additional four 0.303-inch guns and carrying the AI 
Mk.IV radar.  A crew of two was carried, the radar operator sitting in 
the rear cockpit.  There were no provisions for rear-defense machine 
guns or for bombs.  

The first of these Havoc Is entered service with No.  85 Squadron of 
the RAF on April 7, 1941.  Havocs subsequently also served with No.  
25 and 92 RAF Squadrons.  The Havoc night fighters and intruders were 
not outstanding combat aircraft in RAF service, but they managed to 
fill the gap until better equipment became available.  

Number 92 Squadron received twenty modified Havoc I (Pandora) intruder 
aircraft, the name "Pandora" being a code name for the Long Aerial 
Mine (LAM) which was an explosive charge towed by a 2000-foot length 
of cable stowed in the bomb bay of the Havoc.  The LAM was trailed in 
the path of enemy aircraft in the hope of scoring a hit.  This device 
was not very successful, and No.  92 Squadron was disbanded in 
November 1941.  The "Pandora" Havocs were converted back to Intruder 
configurations.  

The Havoc I Turbinlite was the name given to a night fighter version 
which was modified to carry a 2700 million candlepower Helmore/G.E.C.  
searchlight that was to operate in conjunction with the AI radar.  
Thirty-one such Turbinlite conversions were made.  Since the nose and 
the bomb bay were now full of equipment, the Turbinlite Havoc was 
unarmed, and depended on accompanying fighters to destroy the targets 
which it was supposed to illuminate.  This mode of attack was not all 
that successful, since the glaring searchlight gave enemy defensive 
gunners something bright to fire at.  

The RAF also inherited a French contract for one hundred DB-7As 
powered by the more powerful 1600 hp fourteen-cylinder Wright 
R-2600-A5B Double Cyclone air-cooled radial.  The engines were housed 
in longer nacelles and the vertical tail surfaces had increased area.  
In the original French specification, the aircraft were to have had 
similar armament as the DB-7 but were to be equipped with a fixed, 
aft-firing machine gun mounted in each engine nacelle.  These DB-7As 
were taken over by the RAF and assigned the serials AH430 to AH529 and 
given the name *Havoc II*.  They were all converted to night fighter 
configuration and fitted with a new unglazed nose housing twelve 
0.303-inch Browning machine guns.  Thirty-nine Havoc IIs were modified 
to carry Turbinlite searchlights and had all their armament deleted.  
These served briefly until the development of centimetric radar made 
such techniques obsolete.  

The DB-7B was the only version of the DB-7/A-20 series directly 
ordered by Britain, all others having been commandeered ex-French 
contract machines.  An initial order for 150 was placed on February 
20, 1940, which was later increased to 300.  The RAF designation for 
the DB-7B was Boston III.  The DB-7B had revised systems and 
introduced a bomb-aimer nose extending six inches further and having 
25 percent more glazed area.  Serials were W8252 to W8401 and Z2155 to 
Z2304.  Power was provided by two 1600 hp Wright R-2600-A5B radials.  
The self-sealing tanks were improved and armor protection was better.  
Total fuel capacity was increased from 205 US gallons to 394 US 
gallons in order to improve the range, which had been the primary 
weakness of earlier Bostons.  They were fitted with British 
instruments, bomb rocks and 0.303-inch machine guns.  Deliveries began 
in the spring of 1941.  

Boston III serial number W8315 was experimentally fitted with a 
four-gun Boulton Paul power-operated dorsal turret, and W8268/G was 
fitted with four rocket-launching rails underneath each wing.  

The French equivalent of the DB-7B for Britain was designated DB-73.  
480 DB-73s were ordered by France on May 18, 1940.  They were to be 
fitted with French equipment and instruments, but all were completed 
to DB-7B standards following the French capitulation and were 
delivered to Britain as Boston IIIs.  They bore the serial numbers 
AL263 to AL502 and AL668 to AL907.  In addition one DB-7B (AH740) was 
delivered as a replacement for the DB-7A (AH430) which had crashed in 
the USA before delivery.  Power was provided by two 1600 hp Wright 
R-2600-A5B radials.  Total fuel capacity was increased from 205 US 
gallons to 394 gallons in order to improve the range so that the 
aircraft could operate against targets in occupied Europe.  

The Boston III was the first of the DB-7/A-20 series actually to 
operate with the RAF in its intended role of light bomber.  However, 
many were modified to Turbinlite and Intruder configurations.  The 
Boston III (Intruder) aircraft retained their transparent noses but 
were painted matte black, equipped with flame-damping exhausts, and 
fitted with a belly gun pack housing four 20-mm Hispano cannon which 
supplemented the standard Boston III armament.  These operated from 
mid 1942-onwards with Nos 418 (RCAF) and 605 Squadrons.  

205 DB-73s and six DB-7Bs were retained by the USAAF when the original 
British and French contracts were transferred to the Lend-Lease 
program.  

The initial USAAC order for the DB-7 was for 63 A-20s.  They were to 
be powered by turbosupercharged Wright R-2600-7 radials, and were to 
have been high-altitude light bombers.  However, these engines 
developed cooling problems and troubles were encountered with the 
turbosuperchargers.  In the event, only the fifteenth aircraft 
(39-735) was actually fitted with the supercharged R-2600-7 engine.  
Since it was felt that there was no need for higher power at high 
altitudes for an aircraft which was meant to perform at its best at 
low and medium altitudes, all other A-20s were converted to A-20A 
configuration with 1600 hp Wright R-2600-11 engines without 
superchargers.  

Before the USA entered the Second World War, the USAAC felt that it 
needed long-range fighters more than it needed attack bombers, and the 
prototype A-20 (39-735) was adapted for night fighting duties under 
the designation XP-70.  Two unsupercharged 1600 hp Wright R-2600-11s 
replaced the turbosupercharged R-2600-7s.  RAF experience with the 
modified DB-7 Havoc was used as a guideline.  British AI Mk IV radar 
was mounted in an unglazed nose, with an arrow-like transmitting 
antenna located in front of the nose, and receiving antennae being 
located on the fuselage sides and on the port wing.  All bomb racks 
and all defensive armament were removed.  The crew was reduced from 
three to two, the second crewman being a radar operator seated in the 
rear cockpit.  Four 20-mm cannon with 60 rpg were installed in a 
ventral tub.  The success of these modifications led to a USAAC 
decision on October 15, 1940 to have fifty-nine more of the A-20s on 
order modified as P-70 night fighters.  

Fifty-nine P-70s, originally ordered as A-20s were completed with 
R-2600-11 engines as night fighters.  Serials were 39-736 to 39-740, 
39-742 to 39-744, 39-746 and 39-747 and 39-749 to 39-797) They were 
identical to the XP-70 except for minor equipment changes.  Maximum 
speed was 329 mph at 14,000 feet.  An altitude of 12,000 feet could be 
attained in 8 minutes, service ceiling was 28,250 feet, and combat 
range was 1060 miles.  Weights were 16,031 pounds empty and 20,984 
pounds gross.  The first P-70 was delivered in April of 1942, and the 
order was completed in September of that year.  The name *Nighthawk* 
seems to have been given to the P-70, although I don't know if it was 
official.  

The P-70A-1 was the designation given to thirty-nine A-20Cs modified 
by the USAAF in 1943.  The A-20C was the US equivalent of the British 
DB-7B.  They were powered by two 1600 hp R-2600-23s and were armed 
with six to eight 0.50-inch machine guns in a ventral tray.  Improved 
radar equipment was installed in the nose.  Serials were 42-33143, 
33148,33152, 33164, 33165, 33170,33177, 33179, 33221, 54057/54062, 
54064/54068, 54103, 54105, 54106, 54108/54110, 54112, 54126/54129, 
54131/54142, 54161, 54163/54165, and 54267/54274.  

P-70A-2 was the designation given to 65 A-20Gs modified as night 
fighters.  The A-20G featured an unglazed nose housing a battery of 
forward-firing guns.  Starting with the A-20G-20-DO production block, 
the single hand-held machine gun in the dorsal position was replaced 
by a two-gun Martin turret.  The P-70A-2 retained the A-20G's standard 
battery of forward-firing guns, but all flexible defensive weapons 
were removed.  They were otherwise similar to the P-70A-1.  I don't 
have any record of the serial numbers of the P-70A-2s.  

P-70B-1 was the designation given to a single A-20G-10-DO modified as 
an experimental night fighter fitted with SCR720 centimetric radar in 
the nose.  Armament consisted of six 0.50-inch machine guns in three 
blisters on each side of the fuselage.  

P-70B-2 was the designation given to 105 A-20Gs and A-20Js modified as 
night fighter trainers and fitted with SCR720 or SCR729 centimetric 
radar in the nose.  Six to eight 0.50-in machine guns could be carried 
in a ventral tray, but were not always fitted.  Serials were 42-86858, 
26892, 86896, 86900/86902, 86904/86911, 43-9682, 42-9727, 9728, 9732, 
9727, 9739, 9784/9789, 9992, 10000, 10004, and 21551.  

Since the USAAF had no night fighter units when the USA entered World 
War 2, a night fighter training organization was established at 
Orlando, Florida.  Most of the P-70 Nighthawk aircraft served there 
with the 481st Night Fighter Operational Training Group to develop 
tactics and procedures for radar-controlled night interceptions and to 
train the crews of nineteen night fighter squadrons.  Very few of 
these P-70s ever went overseas, most remaining in the USA to be passed 
on to the next night fighter units that needed to be trained.  Most 
units trained on the P-70 were reequipped with the Northrop P-61 Black 
Widow before they transferred overseas.  

Only five night fighter squadrons were still equipped with P-70s at 
the time they were deployed overseas.  Four P-70-trained night fighter 
squadrons were sent with their aircraft to North Africa in 1943 for 
service with the Twelfth Air Force.  However, when they got there, 
these outfits used Bristol Beaufighter VIF fighters obtained from 
Britain under Reverse Lend-Lease.  The 427th Night Figher Squadron 
took its P-70s with it when it deployed to Italy, but the squadron 
exchanged its P-70s for Northrop P-61 Black Widows before it became 
operational.  

The P-70 actually saw some combat action in the Pacific Theatre, 
although their service there was quite brief.  The 6th Night Fighter 
Squadron began operations with its P-70s from Henderson Field, 
Guadalcanal, in February 1943.  It was later supplanted by the 419th 
Night Fighter Squadron.  The 418th and 421st Night Fighter Squadrons 
flew P-70s operationally in New Guinea for a brief time.  The P-70 was 
not very successful in combat, scoring only two kills during the 
entire war.  The P-70 lacked sufficient performance to intercept 
Japanese night raiders unless it was extremely fortunate.  P-70s were 
replaced with P-61s just as soon as these aircraft would be made 
available.  

Sources: 

  McDonnell Douglas Aircraft Since 1920, Vol 1, Rene J.  Francillon, 
  Naval Institute Press, 1988 

  The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.  

  American Combat Planes, Ray Wagner, 3rd Edition, Doubleday, 1982.  

  War Planes of the Second World War, Fighters, William Green, 1964.  

Joe Baugher		AT&T Bell Laboratories   	
2000 North Naperville Road      Naperville, Illinois 60566-7033