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Boeing Model 40

United States (1927)
Picture of Boeing Model 40 Mailplane Transport Biplane
Picture of Boeing Model 40 Mailplane Transport Biplane Picture of Boeing Model 40 Mailplane Transport Biplane
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Fewer than 100 Boeing Model 40s were produced in the latter part of the 1920s - these serving with a select few global operators.


Detailing the development and operational history of the Boeing Model 40 Mailplane Transport Biplane.  Entry last updated on 4/25/2016. Authored by Staff Writer. Content ©www.MilitaryFactory.com

One of the earlier, effective uses of the airplane outside of the military realm was in mail delivery. Until this point in history, mail arrived view rail or other ground-based method. Some aircraft designs were developed exclusively for the mail delivery service and generally built around good speed and inherently strong hauling capabilities. Boeing did just that with its Model 40 which undertook its first flight on July 20th, 1925 and introduced the product in July of 1927. About 80 of the type were ultimately built and served several transport lines of the day (including Boeing Air Transport).

The aircraft was originally developed to a new requirement put forth by the United States Postal Service (USPS). Up to this point, the service relied on the British de Havilland DH.4 biplane which appeared during the fighting of World War 1 (1914-1918) in 1917. Nearly 6,300 of the two-seat biplane light bombers were produced with a bulk of this (including its Liberty engines) emerging from American factories. The line went on to influence subsequent aircraft such as the DH-9 detailed elsewhere on this site.

To ease development and production, the same Liberty engines used by the wartime version of the aircraft would be featured in the new mail plane. A biplane wing arrangement was retained and the tail unit sported a conventional single-finned configuration. The open-air, single-seat cockpit was seated aft and under the upper wing element. The undercarriage was fixed and wheeled at all three legs. The exposed Liberty V12 radial engine was fitted in the nose and drove a two-bladed propeller. Steel tubing, aluminum, wood and fabric were used in the aircraft's general construction makeup. The original aircraft held a cargo capacity of 1,000 lb.


Picture of the Boeing Model 40 Mailplane Transport Biplane
Picture of the Boeing Model 40 Mailplane Transport Biplane


The resultant design was the Boeing "Model 40". The USPS ended up pursuing the competing Douglas M series instead after securing the Boeing prototype. However, the Contract Air Mail Act of 1925 opened two fronts in the mail service approach, an eastern and western region, and Boeing looked to secure its aircraft for the latter routes. This involved revising the Model 40 into the "Model 40A" to make for a more tempting product in which a key change was introduction of the lighter weight Pratt & Whitney "Wasp" radial engine of 425 horsepower output. An interesting addition was a two-person cabin fitted between the upper and lower wing elements where each position was given a hinged, automobile-style access door and viewing windows. In terms of cargo, the aircraft improved its hauling capacity to 1,200 pounds of mail goods.

Twenty-five Model 40A aircraft were purchased and some were eventually fitted with Pratt & Whitney "Hornet" engines of 525 horsepower for improved performance. This produced the Model 40B-2 variant which were essentially re-engined Model 40A aircraft. The Model 40B-4 designation marked new production aircraft fitted with Hornet engines from the outset. The Model 40B series was followed by the "Model 40C" which could seat four persons in its cabin space.

Beyond the United States, the Model 40 was featured as part of the Honduran Air Force service and a pair are known to have been delivered to New Zealand. Boeing Canada added aircraft to the total production stock through a few of its Model 40H-4 variant.

Performance from this interwar biplane (in particular the Model 40A) included a maximum speed of 128 miles per hour, a cruise speed of 105 miles per hour, a range out to 650 miles, a service ceiling of 14,500 feet and a rate-of-climb of 770 feet per minute.






Our Data Modules allow for quick visual reference when comparing a single entry against contemporary designs. Areas covered include general ratings, speed assessments, and relative ranges based on distances between major cities.

Image of collection of graph types

Relative Maximum Speed Rating
Hi: 150mph
Lo: 75mph
    This entry's maximum listed speed (127mph).

    Graph average of 112.5 miles-per-hour.
City-to-City Ranges
NYC
 
  LON
LON
 
  PAR
PAR
 
  BER
BER
 
  MOS
MOS
 
  TOK
TOK
 
  SYD
SYD
 
  LAX
LAX
 
  NYC
Graph showcases the Boeing Model 40's operational range (on internal fuel) when compared to distances between major cities.
Aviation Era
Pie graph section
Pie graph section
Pie graph section
Pie graph section
Pie graph section
Useful in showcasing the era cross-over of particular aircraft/aerospace designs.
Unit Production Comparison
Comm. Market HI*: 44,000 units
Military Market HI**: 36,183 units
80
80


  * Commercial Market High belongs to Cessna 172.

  ** Military Market High belongs to Ilyushin Il-2.


Altitude Visualization
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National Flag Graphic
Origin: United States
Year: 1927
Type: Mailplane Transport Biplane
Manufacturer(s): Boeing - USA
Production: 80
Global Operators:
Canada; Honduras; New Zealand; United States
Historical Commitments / Honors:

Military lapel ribbon for Operation Allied Force
Military lapel ribbon for the Arab-Israeli War
Military lapel ribbon for the Battle of Britain
Military lapel ribbon for the Battle of Midway
Military lapel ribbon for the Berlin Airlift
Military lapel ribbon for the Chaco War
Military lapel ribbon for the Cold War
Military lapel ribbon for the Cuban Missile Crisis
Military lapel ribbon for the Falklands War
Military lapel ribbon for the French-Indochina War
Military lapel ribbon for the Golden Age of Flight
Military lapel ribbon for the 1991 Gulf War
Military lapel ribbon for the Indo-Pak Wars
Military lapel ribbon for the Iran-Iraq War
Military lapel ribbon for the Korean War
Military lapel ribbon for the 1982 Lebanon War
Military lapel ribbon for the Malayan Emergency
Military lapel ribbon for the attack on Pearl Harbor
Military lapel ribbon for the Six Day War
Military lapel ribbon for the Soviet-Afghan War
Military lapel ribbon for the Spanish Civil War
Military lapel ribbon for the Suez Crisis
Military lapel ribbon for the Vietnam War
Military lapel ribbon for Warsaw Pact of the Cold War-era
Military lapel ribbon for the WASP (WW2)
Military lapel ribbon for the World War 1
Military lapel ribbon for the World War 2
Military lapel ribbon for the Yom Kippur
* Ribbons not necessarily indicative of actual historical campaign ribbons. Ribbons are clickable to their respective campaigns/operations.
Measurements and Weights icon
Structural - Crew, Dimensions, and Weights:
Unless otherwise noted the presented statistics below pertain to the Boeing Model 40 model. Common measurements, and their respective conversions, are shown when possible.

Operational
CREW


Personnel
1


Dimension
LENGTH


Feet
33.14 ft


Meters
10.1 m


Dimension
WIDTH


Feet
44.29 ft


Meters
13.5 m


Dimension
HEIGHT


Feet
12.30 ft


Meters
3.75 m


Weight
EMPTY


Pounds
3,538 lb


Kilograms
1,605 kg


Weight
LOADED


Pounds
6,019 lb


Kilograms
2,730 kg

Engine icon
Installed Power - Standard Day Performance:
1 x Pratt & Whitney Wasp radial piston engine developing 420 horsepower.

Performance
SPEED


Miles-per-Hour
127 mph


Kilometers-per-Hour
205 kph


Knots
111 kts


Performance
RANGE


Miles
649 mi


Kilometers
1,045 km


Nautical Miles
564 nm


Performance
CEILING


Feet
14,501 ft


Meters
4,420 m


Miles
2.75 mi


Performance
CLIMB RATE


Feet-per-Minute
770 ft/min


Meters-per-Minute
235 m/min

Armament - Hardpoints (0):

None.
Variants: Series Model Variants
• Model 40 - Base Series Designation; original model of 1925 with Liberty powerplant.
• Model 40A - Fitted with PW Wasp radial engine; two-seat passenger compartment; 25 examples.
• Model 40B - Fitted with PW Hornet radial engine
• Model 40B-2 - Re-engined Model 40A with Hornet engine; 19 examples.
• Model 40B-4 - Four-passenger cabin seating; 38 examples completed.
• Model 40B-4A - Engine testbed airframe
• Model 40H-4 - Boeing Canada Model 40B-4; four examples
• Model 40C - PW Wasp engine; ten examples
• Model 40X - Special variant based on Model 40C with two passenger seating in cabin; forward cockpit ahead of pilot.
• Model 40Y - Special variant based on the Modle 40X; PW Hornet engine used.