LIPNUR Belalang

{{Infobox aircraft |name=Belalang |image=LIPNUR NU-85 Belalang, Dirgantara Mandala Museum 43.jpg |caption=NU-85 Belalang prototype in-flight |national_origin=Indonesia |type=Military trainer |manufacturer=Angkatan Udara Republik Indonesia, Depot Penjelidikan, Pertjobaan dan Pembuatan/LIPNUR |designer=Nurtanio Pringgoadisuryo (id) |first_flight=17 April 1958<ref name="Janes 65 p83"/> |introduction=1959 |retired= |status= Retired |primary_user=Indonesian Air Force |more_users=Indonesian Army <br/> Indonesian Civil Aviation Institute |produced= |number_built=9 (estimated) |developed_from= Piper J-3 Cub |variants= }}

The '''LIPNUR Belalang''' ({{langx|id|Grasshopper}}) was a military trainer aircraft built in small numbers in Indonesia by LIPNUR in the late 1950s. It was essentially a Piper L-4J Grasshopper converted to give it a low wing. The NU-85 prototype flew for the first time on 17 April 1958 and the first production of NU-90 took place in 1959.<ref name="Flight International">{{cite web|url=http://www.flightglobal.com/pdfarchive/view/1962/1962%20-%201288.html|title=Asia's Aircraft Industries:NU-90 Belalang|publisher=Flight International|date=26 July 1962|access-date=9 March 2021|archive-url=https://web.archive.org/web/20121025165557/http://www.flightglobal.com/pdfarchive/view/1962/1962%20-%201288.html|archive-date=25 October 2012|url-status=dead}}</ref> The aircraft was operated by Indonesian Air Force.<ref name="Flight International"/> Indonesian Army and Indonesian Civil Aviation Institute at Curug, Tangerang also used this aircraft.<ref name="Belalang">{{cite web|url=https://aviahistoria.com/2017/07/31/swadaya-pesawat-latih-yang-gagal-nu-8590-belalang/|title=Swadaya Pesawat Latih yang Gagal – Nu-85/90 Belalang|website=aviahistoria.com|date=31 July 2017|access-date=10 March 2021|lang=id}}</ref>

==Design and development==

In 1949-1950 period, the Indonesian Air Force (then called AURI) received around 60 Piper L-4J Grasshoppers from Royal Netherlands East Indies Air Force as part of the transfer of sovereignty.<ref name="PiperCub">{{cite web|url=https://aviahistoria.com/2020/03/19/piper-l-4j-r-344-museum-satria-mandala/|title=Piper L-4J R-344 Museum Satria Mandala|website=aviahistoria.com|date=19 March 2020|access-date=10 March 2021|lang=id}}</ref> AURI used them as liaison and primary trainer aircraft.<ref name="PiperCub"/> In 1957, AURI decided that their ex-Dutch L-4Js, which were powered by 65 hp Continental O-170, were already ageing and needed to be replaced. The L-4Js also has high wing configuration so its aerobatic performance is very limited.<ref name="Belalang"/>

Nurtanio Pringgoadisuryo, head of AURI’s Research, Development, and Production Depot at Andir airfield in Bandung, decided to modified the ageing L-4Js as it can be developed rapidly and with low technology and thus has a low production cost.<ref name="Belalang"/> An L-4J was then modified by converting it into a low wing design with "V" lift struts and it was powered with an 85 hp Continental C-85 four-cylinder horizontally opposed piston engine with Sensenich two-bladed fixed-pitch propeller.<ref name="FledglingInsects p113-115"> Stroud Oct 2017, p.113-115.</ref> The aircraft maintained its old canopy but due to the new wing structure the canopy was hinged open to the right.<ref name="Belalang"/> The prototype was then designated as '''NU-85 Belalang'''. The 85 was derived from the 85 hp engine, while the name ''Belalang'' (grasshopper) was used as his single-engine designs were named after insects.<ref name="Belalang"/>

The NU-85 prototype first flew on 17 April 1958. Another source stated that it was first flown on 26 April 1958, piloted by Nurtanio himself.<ref name="Belalang"/> After testing, it was determined that the NU-85 performed better than the L-4Js in their role as primary trainer.<ref name="FledglingInsects p113-115"/> Despite the performance observed, Nurtanio determined it still needed further refinement.<ref name="Belalang"/>

Then in 1959, Nurtanio designed the '''NU-90'''.<ref name="Belalang"/> The differences from its predecessor are it was powered by more powerful 90 hp Continental C-90-12F flat-four direct-drive engine.<ref name="FledglingInsects p113-115"/> It also has bubble canopy that were split into two sections, the forward section hinged to the right and the rear section slides to the aft.<ref name="FledglingInsects p113-115"/> The improved '''NU-90A''' variant was powered with 100 hp Continental O-200 engine with 6 ft (1.8 m)-diameter McCauley metal fixed-pitch propeller. The NU-90A also has sliding canopy.<ref name="Janes 65 p83"/> It retains many of the L-4J's features, although modified, such as its USA-35B airfoil but with the flaps removed, extended length of the ailerons, the split-axle mainwheels which was moved 10 cm forward, and also L-4Js original wing structures.<ref name="FledglingInsects p113-115"/> The wings itself was braced with V-struts from the top section of the fuselage longerons and was set 1° 37’ incidence at the root and 5° dihedral.<ref name="FledglingInsects p113-115"/> The control surfaces were consisted of aluminum-alloy-frame covered with fiberglass.<ref name="FledglingInsects p113-115"/> The fuselage was of welded steel construction covered with fiberglass, while the vertical stabilizer was fabric-covered welded steel.<ref name="FledglingInsects p113-115"/>

==Operational history==

Three pre-production NU-90 were sent to the Indonesian Air Force Academy in Yogyakarta for evaluation. Although the aircraft were still in the evaluation stage, eight cadets managed to solo fly after being trained with the three Belalangs.<ref name="Belalang"/> The three aircraft were then sent back to the LIPNUR facility at Bandung to be reconditioned and overhauled.<ref name="Belalang"/> Those aircraft then were transferred to the Indonesian Aviation Civil Institute in Curug, Tangerang.<ref name="Belalang"/> Satisfied with the aircraft's performance, Indonesian Air Force ordered 50 units of Belalang to replace the L-4J Grasshoppers, but the orders could not be fulfilled as the LIPNUR facility at that time lacked tools to mass-produced them.<ref name="Belalang"/> The Indonesian Army Aviation Command also expressed interest with Belalang. The Indonesian Army Aviation School at Kalibanteng airfield in Semarang received 5 Belalangs to be used as primary trainers.<ref name="Belalang"/> As of 2017, a single incomplete Belalang still exist and used as a teaching tool at a vocational high school in Semarang.<ref name="Belalang"/>

==Variants== * '''Belalang NU-85''' - 85 hp Continental C-85 engine and hinged canopy, single prototype.<ref name="Belalang"/> * '''Belalang NU-90''' - 90 hp Continental C-90-12F engine, three pre-production aircraft.<ref name="Belalang"/> * '''Belalang NU-90A''' - 75 kW (100 hp) Continental O-200 engine replacing 67 kW (90 hp) Continental C-90-12F of earlier versions, sliding canopy, revised undercarriage,<ref name="Janes 65 p83"> Taylor 1965, p.83.</ref> five production aircraft.<ref name="Belalang"/>

==Operators== ; {{INA}} * Indonesian Air Force * Indonesian Army ** Indonesian Army Aviation Command * Indonesian Civil Aviation Institute (id)

==Specifications (90A)== {{Aircraft specs |ref=Jane's All The World's Aircraft 1965-66 <ref name="Janes 65 p83"/> |prime units?=met  |genhide=

|crew=2 |capacity= |length m=7.70 |length ft= |length in= |span m=9.50 |span ft= |span in= |height m=2.03 |height ft= |height in= |wing area sqm=15.0 |wing area sqft= |airfoil=USA-35B |aspect ratio=6:1 |empty weight kg=472 |empty weight lb= |gross weight kg=682 |gross weight lb= |fuel capacity={{convert|45|L|USgal impgal|abbr=on}}  |eng1 number=1 |eng1 name=Continental O-200-A |eng1 type=air-cooled flat-four engine |eng1 kw= |eng1 hp=100

|perfhide=

|avionics= }}

==See also== {{commons category|LIPNUR Belalang}} *Piper J-3 Cub *LIPNUR Kunang *LIPNUR Super Kunang *LIPNUR Sikumbang

==References== {{reflist}}

* Taylor, John W. R. ''Jane's All The World's Aircraft 1965-66''. London: Sampson Low, Marston, 1965. * {{cite journal |last1=Stroud |first1=Nick |date=15 October 2017 |title=Indonesia's Fledgling Insects |journal=The Aviation Historian |volume=21 |pages=110–117 |issn=2051-1930}}

Category:1950s Indonesian military trainer aircraft Category:Single-engined tractor aircraft Category:Low-wing aircraft Category:Aircraft with fixed conventional landing gear Category:Aircraft first flown in 1958 Category:Single-engined piston aircraft