Kalinin K-4

__NOTOC__

The Kalinin K-4 was an airliner built in the Soviet Union in the late 1920s which was also adapted for use as a photographic survey aircraft and as an air ambulance. A further development of the K-1, it was a conventional high-wing, strut-braced monoplane with separate enclosed cabin and cockpit. Kalinin undertook the design to offer a locally-produced alternative to pioneering Ukrainian airline Ukrvozduhput, which was at that time flying Dornier designs. The structure was of mixed wood and metal construction, but with major assemblies designed in both wood and metal versions, allowing them to be interchanged. The design also featured a variable-incidence horizontal stabiliser, and the engine mounting was intended to facilitate the ready interchange of different powerplants.

Development

By May 1928, four pre-production machines were being constructed at the Kharkov Aviation Factory. While this work was proceeding, Dobrolyot placed an order with Ukrvozduhput for two photographic survey aircraft, a request that the latter undertook to fill with two specially equipped K-4s. These machines took priority at the factory, and differed from the passenger version in having a ventral hatch for one or two cameras mounted on the cabin floor, plus a self-contained darkroom. The air ambulance version was developed initially to exhibit at the 1928 Berlin Air Show, and examples would later see military service with Soviet forces in Finland during the Winter War.

In summer the same year, Soviet pilots evaluated the K-4 against a Dornier Merkur that was making a promotional tour. Encouraged by the positive feedback for his design, Kalinin obtained approval for a demanding flight between Kharkov, Baku, Tbilisi, and back. Piloted by Mikhail Artemevich Snegirev, a K-4 named "Червона Украина" (Chervona Ukraina - "Red Ukraine") made the trip between 22 and 24 August. This same pilot and aircraft would set a new aerial distance record almost exactly a year later, flying from Kharkov to Moscow to Irkutsk, then back to Moscow and Kharkov. Although the original intention had been to reach Vladivostok, Snegirev still covered 10,400 km (6,500 miles) in 73 hours.

Operational history

Flight testing was concluded in July 1928, and the four pre-production machines were handed over to Ukrvozduhput. They were put into service on routes linking the Crimea and Caucasus, and another ten aircraft were ordered. The following year, services were expanded to Tehran in a joint service arrangement with Junkers Luftverkehr. On 1 May 1929, seven Ukrvozduhput K-4s flew in formation from Kharkov to Rostov, Sochi, Mineralnye Vody and Tbilisi. Service with the airline was short, however, as the K-4 demonstrated a poor safety record. Between 23 May and 24 August, K-4s were involved in fourteen accidents, including two in which passengers were killed. The first of these fatal accidents took place on 25 June, when K-4 (registered СССР-219) crashed after take-off from Sukhumi due to engine failure, killing two passengers. The second took place on 24 August when K-4 registered СССР-217 dove suddenly into the sea shortly after take-off from Sochi. The wooden wings of the aircraft enabled it to float long enough for rescuers to reach it, however it sank soon afterwards, taking one passenger and one of the rescuers with it. The rescuer who drowned was celebrated Latvian military commander Jan Fabricius, who had been Commander and the Commissioner of the Red Army during the Russian Civil War. Although the subsequent investigation attributed the crash to pilot error, numerous manufacturing defects were discovered throughout the K-4 fleet, leading to their withdrawal from service shortly thereafter.

Dobrolyot's survey machines commenced operations in August 1928, and were soon joined by around a dozen examples of the airliner version, which were used on routes in Kazakhstan and Central Asia. The K-4 proved unsuitable for these conditions, with the hot conditions causing the aircraft's wooden structures (especially the wings) to deform. The costs of maintenance and repairs soon became prohibitive, and by Spring 1930, the aircraft were withdrawn. The type was evaluated for service on routes in the north, and one was used for the first passenger flight from Moscow to Tashkent, but nothing came of this. Eventually, the remaining aircraft were used for survey work in Siberia and the Urals.

Operators

; USSR
* Ukrvozduhput
* Dobrolyot

pecifications (airliner version)

aerospecs
ref=
met or eng?= met

crew=Two pilots
capacity=Four passengers "or" 410 kg (900 lb) cargo
length m=11.35
length ft=37
length in=3
span m=16.75
span ft=54
span in=11
swept m=
swept ft=
swept in=
rot number=
rot dia m=
rot dia ft=
rot dia in=
dia m=
dia ft=
dia in=
width m=
width ft=
width in=
height m=2.76
height ft=9
height in=1
wing area sqm=40.0
wing area sqft=430
swept area sqm=
swept area sqft=
rot area sqm=
rot area sqft=
volume m3=
volume ft3=
aspect ratio=
wing profile=
empty weight kg=1,540
empty weight lb=3,390
gross weight kg=2,350
gross weight lb=5,170
lift kg=
lift lb=

eng1 number=1
eng1 type=BMW IV
eng1 kw= 180
eng1 hp= 240
eng1 kn=
eng1 lbf=
eng1 kn-ab=
eng1 lbf-ab=
eng2 number=
eng2 type=
eng2 kw=
eng2 hp=
eng2 kn=
eng2 lbf=
eng2 kn-ab=
eng2 lbf-ab=

max speed kmh=173
max speed mph=108
max speed mach=
cruise speed kmh=
cruise speed mph=
stall speed kmh=
stall speed mph=
range km=1,040
range miles=650
endurance h=
endurance min=
ceiling m=4,500
ceiling ft=14,800
g limits=
roll rate=
glide ratio=
climb rate ms=2.4
climb rate ftmin=470
sink rate ms=
sink rate ftmin=

armament1=
armament2=
armament3=
armament4=
armament5=
armament6= aircontent
see also=
related=
similar aircraft=
lists=

References

*
* [http://www.ctrl-c.liu.se/misc/ram/k-4.html Russian Aviation Museum]
* [http://www.airwar.ru/enc/cw1/k4.html Уголок неба]
* [http://airliner.narod.ru/airliners1927-30/kalinin-k4.htm Авиалайнеры мира]