Häfeli DH-3

Häfeli DH-3
Type:	Reconnaissance and training aircraft
Design country:	Switzerland
Manufacturer:	Federal construction workshop (K + W)
First flight:	1917
Production time:	1917-1925
Number of pieces:	DH-3: 24 ; DH-3a: 83 ; DH-3b: 3

The Häfeli DH-3 was a double-decker - reconnaissance aircraft manufacturer's Federal Konstruktionswerkstätte (K + W).

history

At the beginning of 1917, K + W received the order to build 30 copies of the DH-3, this without testing, as it was an improved version of the previous DH-2 design and the airframe remained essentially unchanged. However, the landing gear was found to be fragile and there were also cooling problems with the engine until an improved system was installed.

Twenty-four specimens were produced in 1917 with the Argus As II engine, which were withdrawn from service in 1923 when defects in the structural strength of an airframe that had flown 600 hours were discovered. A DH-3 carried out the first airmail flight in Switzerland from Zurich / Dübendorf to Bern on January 8, 1919 .

variants

DH-3a: four copies were built in 1918, three of them with a Hispano-Suiza HS-41 -8Aa engine. The planes were scrapped in 1922. A second series of 30 machines ordered in 1919 used motors of the same type built under license by Adolph Saurer AG . A third installment of 49 copies was issued in 1925. These included six starter training aircraft with double controls and a test aircraft with the 180 hp Hispano-Suiza HS-41 8Ab engine, which was tested by the Swiss Air Force from October 1929 to April 1930. One machine in Great Britain received Handley-Page slats , which proved themselves so well that all 55 DH-3a still existing at the time were converted accordingly in 1932 in Thun . At the same time, the machines were modified so that the crew could carry back parachutes. These improved DH-3a remained in use until 1938 (according to Hans Giger) or 1939.
DH-3b: three DH-3b used a 150 HP LFW O engine in the test run. Built in 1918, they were in service until 1922. The armament in the form of a single observer machine gun was supplemented by two machine guns permanently installed above the engine.

For winter operation, a number of interchangeable skis kits were available instead of the wheeled chassis.

Whereabouts

Since none of the aircraft was preserved, a project of a replica was started in 1994 for the Museum of the Swiss Air Force .

Technical specifications

Parameter	DH-3a
crew	2
length	7.95 m
span	12.50 m
height	3.10 m
Wing area	38.00 m²
Empty mass	720 kg
Max. Takeoff mass	1110 kg
Top speed	145 km / h at sea level
Service ceiling	4500 m
Range	400 km
Engines	1 × V-engine Hispano-Suiza HS-41 8Aa with 150 PS (110 kW)

literature

World Aircraft Information Files - A – Z of Aircraft , File 896, Sheet 1
Dübendorf Military Airfield Department (ed.) The planes of the Swiss Air Force since 1914 , Th. Gut publishing house, Stäfa, 1974

Web links

Photos and data on the DH-3 (accessed July 11, 2019)

Individual evidence

↑ Hans Giger: Report on the activities of the senior groups Buochs and Interlaken from mid-1979 to the end of 1998 ( Memento from July 10, 2019 in the Internet Archive )

[1] Hans Giger: Report on the activities of the senior groups Buochs and Interlaken from mid-1979 to the end of 1998 ( Memento from July 10, 2019 in the Internet Archive )