View source for Hitachi Ha-51

{{Short description|Aircraft engine}}
{|{{Infobox Aircraft Begin
 |name = Ha-51
 |image = 
 |caption = 
}}
{{Infobox Aircraft Engine
 |type= [[Radial engine]]
 |manufacturer= [[Hitachi]]
 |national origin= [[Japan]]
 |first run= 1944
 |major applications=
 |number built = 4
 |program cost = 
 |unit cost = 
 |developed from = 
 |developed into =
 |variants with their own articles =
}}
|}

The '''Hitachi Ha-51''' (unified designation), was a [[Japan|Japanese]] air-cooled twenty-two-cylinder twin-row radial aircraft engine designed by [[Hitachi]] during the final years of [[World War II]]. The first prototype ran in 1944 at a rating of {{convert|1772|kW|hp|-3|abbr=on}}, but only four examples were built. In August 1945, development was halted. The engine had yet to find an application and bombing had destroyed the factory where production was to take place.

==Design==
In 1942, the most powerful Japanese aircraft engine in service produced less than {{convert|2000|hp|kW|abbr=on}} and the [[Imperial Japanese Army]] understood that this constrained the development of higher performance aircraft. In response, in December 1942, the Army issued a request for a new radial aircraft engine capable of more than {{convert|2500|hp|kW|abbr=on}} which was to be designated Ha.51. Two companies responded, [[Nakajima Aircraft Company|Nakajima]] and [[Hitachi]]. The Hitachi engine was designed at the company’s engine plant in Tachikawa as a 22-cylinder engine, with cylinders arranged as a two-row radial engine with 11 cylinders per row instead of 9.{{sfn|D’Olier|et al|1947|page=8}}

The resulting Hitachi design was one of the first radial aircraft engines with more than twenty cylinders developed anywhere in the world.{{sfn|Suzuki|et al|2008|page=73}} The engine had a steel crankcase, with an aluminium head mounted on steel cylinders each of bore {{convert|130|mm|in|abbr=on}} and stroke {{convert|150|mm|in|abbr=on}}, similar to the eighteen-cylinder [[Nakajima Homare]], but angled at 60° rather than 78° to accommodate the additional four cylinders.{{sfn|Suzuki|et al|2008|page=74}}

Five engines were ordered and three built.{{sfn|D’Olier|et al|1947|page=51}} The first ran in 1944.<ref name=Mawhinney2020>{{cite web|last=Mawhinney|first=Rob|title=Japanese Engines: Ha51-01|website=enginehistory.org|url=http://www.enginehistory.org/Piston/Japanese/japanese.shtml|accessdate=1 June 2020}}</ref> One prototype engine was built and ran for 100 hours on test.{{sfn|Suzuki|et al|2008|page=76}} The engine reported very high oil consumption, up to 20g/kW⋅h, which was attributed to the rigidity of the crankcase.{{sfn|Suzuki|et al|2008|page=75}}

The factory was bombed on 24 April 1945 and the programme was halted. The Japanese Army did not have an aircraft available that needed the engine and development had taken substantial resources and these were to redirected to producing engines that had a more immediate need.{{sfn|D’Olier|et al|1947|page=51}}

==Surviving engines==
A single example found at [[Haneda]] is on display at the museum next to [[Narita airport]].<ref name=Mawhinney2020/>

==Specification==
{{Pistonspecs
<!-- If you do not understand how to use this template, please ask at [[Wikipedia talk:WikiProject Aircraft]] -->
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| ref = The Radial 22 Cylinder Engine "HA51" and Genealogic Survey of the Gasuden Aero-Engines {{sfn|Suzuki|et al|2008|page=74}}
| type = 22-cylinder, twin row, air cooled [[radial engine]]
| bore = {{convert|130|mm|in|abbr=on}}
| stroke = {{convert|150|mm|in|abbr=on}}
| displacement = {{convert|43.8|L|in3|0|abbr=on}}
| length = {{convert|2100|mm|in|abbr=on}}
| diameter = {{convert|1270|mm|in|abbr=on}}
| width = 
| height = 
| weight = {{convert|1000|kg|lb|abbr=on}}
| valvetrain = 
| supercharger = Mitsubishi 2-speed
| turbocharger = 
| fuelsystem = 
| fueltype = 
| oilsystem = 
| coolingsystem = 
| power = <br>
** '''Max power: ''' {{convert|1838|kW|hp|abbr=on}} at 3000 rpm at sea level
** '''Rated: '''
**: {{convert|1772|kW|hp|abbr=on}} at 3000 rpm at {{convert|2000|m|ft|abbr=on}} 
**: {{convert|1449|kW|hp|abbr=on}} at 3000 rpm at {{convert|8000|m|ft|abbr=on}}
| specpower = 
| compression = 
| fuelcon = 
| specfuelcon = 
| oilcon = 
| power/weight = 
| designer = 
| reduction_gear = Planetary (0.42)
| general_other = 
| components_other = 
| performance_other = 
}}

==See also==
{{aircontent
<!-- other related articles that have not already linked: -->
|see also=

<!-- designs which were developed into or from this aircraft: -->
|related=

<!-- aircraft that are of similar role, era, and capability as this design: -->
|similar aircraft=

<!-- relevant lists that this aircraft appears in: -->
|lists=
* [[List of aircraft engines]]
<!-- For aircraft engine articles.  Engines that are of similar to this design: -->
|similar engines=
* [[BMW 803]]
* [[Pratt & Whitney R-4360 Wasp Major]]
* [[Wright R-4090 Cyclone 22]]
<!-- See [[WP:Air/PC]] for more explanation of these fields. -->
}}

==References==
===Citations===
{{reflist}}

===Bibliography===
*{{cite book |last1=D’Olier |first1=Franklin |last2=Nitze | first2=Paul H. |display-authors=1 |title= Hitachi Aircraft Company (Hitachi Kokuki K.k.) Corporation Report No.VII| publisher=The United States Strategic Bombing Survey |year=1947 |ref={{harvid|D’Olier|et al|1947}} |url=https://books.google.com/books?id=TvYsAAAAIAAJ}}
*{{cite book |last1=Goodwin |first1=Mike |last2=Starkings |first2=Peter |title=Japanese Aero-Engines 1910-1945 |date=2017 |publisher=MMPBooks |location=Sandomierz, Poland|name-list-style=amp |isbn=978-83-65281-32-6}}
* {{cite journal |last1=Suzuki |first1=Takeshi |last2=Kaki|first2=Kenichi |last3=Takahashi |first3=Toyohiro |last4=Nakanishi |first4=Masayoshi |display-authors=1 |title=「ハ51型 」星型22シ リンダエンジンとガス電航空エンジンの系譜 |trans-title=The Radial 22 Cylinder Engine "HA51" and Genealogic Survey of the Gasuden Aero-Engines |journal=Transactions of the Japan Society of Mechanical Engineers C |volume=74 |number=746 |pages=2403–2410 |language=Japanese |year=2008 |doi=10.1299/kikaic.74.2403 |url= https://www.jstage.jst.go.jp/article/kikaic1979/74/746/74_746_2403/_pdf/-char/ja |ref={{harvid|Suzuki|et al|2008}}|doi-access=free }}

{{Hitachi aeroengines}}

[[Category:1940s aircraft piston engines]]
[[Category:Aircraft air-cooled radial piston engines]]
[[Category:Hitachi aircraft engines]]