Tervamäki ATE-3

The ATE-3 is a Bensen-style autogyro, with a fuselage of welded steel tube. (Tervamäki had spent summer 1958 as a graduate student working at Bensen's factory.) It has a single seat for the pilot, behind which is the rotor mast, and a piston engine driving a pusher propeller. The two-bladed propeller, two-bladed main rotor, and the empennage are all made of fibreglass. It was equipped with a mechanism to pre-rotate the main rotor.

The structure throughout was metal and composite materials, with Tervamäki specifically drawing attention in one of his articles about the aircraft that no wood was used in any part of it.

On Tervamäki's and Eerola's prototype, the forward fuselage was partially enclosed in a fibreglass pod, which was salvaged from a Fibera KK-1e Utu sailplane, along with the windscreen, pilot's seat, and instrument panel. On this prototype, as well as on two other examples, the cockpit was left open (unlike the Utu's fully enclosed cockpit), but at least one example was built without a cockpit pod. Tervamäki noted that the re-used sailplane nose actually added unnecessary weight to the ATE-3, since it was built to tolerate stresses of 6 Gs, while the autogyro could only achieve 2.5 Gs.Tervamäki 1969a, p.21 Its structure also complicated the ATE-3's fuel tank design. The prototype also used parts scavenged from a variety of other sources; motorcycle components were repurposed for parts of the undercarriage, and the throttle and pre-rotation levers came from marine engine controls.Tervamäki 1969a, p.22

Tervamäki and Eerola tested three different tail designs on the prototype. It first flew with a conventional tail, but this was later replaced with a fin and rudder only. The final configuration was a V-tail, which Tervamäki recalled offered the best longitudinal stability (that is, was the most resistant to pilot-induced oscillations), at the expense of lateral stability.

Tervamäki and Eerola began design work on the ATE-3 in May 1966. The design of the aircraft used computer modelling to determine the optimum dimensions for a one-person autogyro that would optimise its flight performance.Tervamäki 1969b, p.51 Within the computer model, the designers were able to vary parameters that included the diameter, chord, and airfoil of the rotor, the pitch, twist, and taper of the blades, plus overall characteristics such as the parasite drag of the fuselage, the gross

weight of the aircraft, and the power of the engine. They ran computations on around fifty different permutations of the design. When the aircraft flew, Tervamäki and Eerola discovered that the computer models had been too optimistic, because they were based on drag values that were not attained in real life.Tervamäki 1969a, p.20

The shape of the original fin and rudder were inspired by the looks of the Wallis WA-116 autogyro that had featured in the recent James Bond film You Only Live Twice.Tervamäki 1969b, p.51–52 Construction began in September 1968.

The powerplant was originally to have been a refurbished McCulloch O-100-1 drone engine, but when the engine vendor was unresponsive, Tervamäki and Eerola opted for a racing-modified Volkswagen automotive engine.Tervamäki 1969b, p.52

The prototype, registered OH-XYV, first flew on 11 May 1968.{{refn|group=lower-alpha|Sport Aviation gives a different date for the first flight: 1 May.}} The tail unit was modified in November 1969 to delete the horizontal stabilisers from the design, and to add an enlarged fin. The original {{convert |6.5 |m |ftin |adj=on }} diameter rotor blades were replaced with a {{convert |7 |m |ftin |adj=on }} rotor instead. The V-tail that was fitted to the aircraft was chosen to maximise longitudinal stability after Tervamäki and Eerola were asked to help the Finnish aviation authorities investigate the fatal crash of a Bensen B-8M at Pori.Tervamäki 1971, p.40 Concluding that the accident had resulted from pilot-induced oscillation, they modified the ATE-3 to increase its dynamic stability.Tervamäki 1971, p.41 They chose a V-tail to give the aircraft the largest practical tail surfaces while still preserving sufficient clearance for the main rotor.

Tervamäki and Eerola flew their ATE-3 for three years before they sold it to an aero club in Kokkola. During this time, Eerola flew the aircraft for its scenes in Leikkikalugangsteri. By 1969, they had also presented the ATE-3 at two airshows in Finland,Tervamäki 1969b, p.54 and before they sold it, at an Experimental Aircraft Association European fly-in at Gothenburg.Raivio 1973, p.10 The latter appearance was noteworthy as one of the few occasions that a Finnish-built aircraft had been presented internationally at the time.

In addition to selling plans to the design, Tervamäki also sold prefabricated rotor blades. Although their mountings were specific to the ATE-3, they could be easily adapted to Bensen rotor heads.

The ATE-3 provided the basis for Tervamäki's later autogyro designs, the JT-5 and MT-7.Taylor 1987, p.564

{{Aircraft specs

|ref=Taylor 1974, p. 41

|prime units?=met

|genhide=

|crew=one pilot

|capacity=

|length m=3.20

|length ft=

|length in=

|length note=

|span m=

|span ft=

|span in=

|span note=

|upper span m=

|upper span ft=

|upper span in=

|upper span note=

|mid span m=

|mid span ft=

|mid span in=

|mid span note=

|lower span m=

|lower span ft=

|lower span in=

|lower span note=

|swept m=

|swept ft=

|swept in=

|swept note=

|dia m=

|dia ft=

|dia in=

|dia note=

|width m=

|width ft=

|width in=

|width note=

|height m=

|height ft=

|height in=

|height note=

|wing area sqm=

|wing area sqft=

|wing area note=

|swept area sqm=

|swept area sqft=

|swept area note=

|volume m3=

|volume ft3=

|volume note=

|aspect ratio=

|airfoil=

|empty weight kg=150

|empty weight lb=

|empty weight note=

|gross weight kg=

|gross weight lb=

|gross weight note=

|max takeoff weight kg=260

|max takeoff weight lb=

|max takeoff weight note=

|fuel capacity=

|lift kg=

|lift lb=

|lift note=

|more general=

|eng1 number=1

|eng1 name=Volkswagen

|eng1 type=four-cylinder, horizontally-opposed, air-cooled automotive engine

|eng1 kw=56

|eng1 hp=

|eng1 shp=

|eng1 kn=

|eng1 lbf=

|eng1 note=

|power original=

|thrust original=

|eng1 kn-ab=

|eng1 lbf-ab=

|eng2 number=

|eng2 name=

|eng2 type=

|eng2 kw=

|eng2 hp=

|eng2 shp=

|eng2 kn=

|eng2 lbf=

|eng2 note=

|eng2 kn-ab=

|eng2 lbf-ab=

|eng3 number=

|eng3 name=

|eng3 type=

|eng3 kw=

|eng3 hp=

|eng3 shp=

|eng3 kn=

|eng3 lbf=

|eng3 note=

|eng3 kn-ab=

|eng3 lbf-ab=

|more power=

|prop blade number=

|prop name=

|prop dia m=

|prop dia ft=

|prop dia in=

|prop dia note=

|rot number=1

|rot dia m=7

|rot dia ft=

|rot dia in=

|rot area sqm=38.5

|rot area sqft=

|rot area note=

|perfhide=

|max speed kmh=140

|max speed mph=

|max speed kts=

|max speed note=

|max speed mach=

|cruise speed kmh=110

|cruise speed mph=

|cruise speed kts=

|cruise speed note=

|stall speed kmh=

|stall speed mph=

|stall speed kts=

|stall speed note=

|never exceed speed kmh=

|never exceed speed mph=

|never exceed speed kts=

|never exceed speed note=

|minimum control speed kmh=

|minimum control speed mph=

|minimum control speed kts=

|minimum control speed note=

|range km=300

|range miles=

|range nmi=

|range note=

|combat range km=

|combat range miles=

|combat range nmi=

|combat range note=

|ferry range km=

|ferry range miles=

|ferry range nmi=

|ferry range note=

|endurance=

|ceiling m=

|ceiling ft=

|ceiling note=

|g limits=

|roll rate=

|glide ratio=

|climb rate ms=3

|climb rate ftmin=

|climb rate note=

|time to altitude=

|sink rate ms=

|sink rate ftmin=

|sink rate note=

|lift to drag=

|wing loading kg/m2=

|wing loading lb/sqft=

|wing loading note=

|disk loading kg/m2=

|disk loading lb/sqft=

|disk loading note=

|fuel consumption kg/km=

|fuel consumption lb/mi=

|power/mass=

|thrust/weight=

|more performance=

|armament=

|guns=

|bombs=

|rockets=

|missiles=

|hardpoints=

|hardpoint capacity=

|hardpoint rockets=

|hardpoint missiles=

|hardpoint bombs=

|hardpoint other=

|avionics=

}}

{{aircontent

|see also=

|related=

|similar aircraft=

|lists=

}}

{{reflist|group=lower-alpha}}

{{reflist}}

• {{cite conference |last=Charnov |first=Bruce H. |title=From Rolf von Bahr to Jukka Tervamäki: The Scandinavian Influence on European Gyroplane History |conference=American Helicopter Society 65th Annual Forum |date=May 27–29, 2009 |url=http://www.vtol.org/forum65/forum65.html |access-date=21 July 2024 |archive-date=5 May 2009 |archive-url=https://web.archive.org/web/20090505221851/http://www.vtol.org/forum65/forum65.html |url-status=dead }}
• {{cite magazine |last=Raivio |first=Jyri |title=Tuo lentävä mies mainiossa koneessaan |trans-title=That flying man in his magnificent plane |magazine=Ilmailu |volume=36 |number=5 |pages=10–12 |date=May 1973 |publisher=Suomen ilmailuliitto |location=Helsinki }}
• {{cite book |title=Jane's All the World's Aircraft 1974-75 |editor1-last=Taylor |editor1-first=John W.R. |date=1974 |publisher=Jane's Yearbooks |location=London |edition=65th }}
• {{cite book |title=Jane's All the World's Aircraft 1987-88 |editor1-last=Taylor |editor1-first=John W.R. |year=1987 |publisher=Jane's Information Group |location=London |edition=78th }}
• {{cite book |last= Taylor |first= Michael J. H. |title=Jane's Encyclopedia of Aviation |year=1993 |publisher=Studio Editions |location=London }}
• {{cite magazine |last=Tervamäki |first=Jukka |title=Featuring the ATE-3 |magazine=Popular Rotorcraft Flying |volume=7 |number=4 |pages=20–24 |date=July–August 1969a |publisher=Popular Rotorcraft Association |location=Raleigh, North Carolina }}
• {{cite magazine |last=Tervamäki |first=Jukka |title=A Sleek Autogyro From Finland |magazine=Sport Aviation |volume=18 |number=2 |pages=51–54 |date=February 1969b |publisher=Experimental Aircraft Association |location=Hales Corner, Wisconsin }}
• {{cite magazine |last=Tervamäki |first=Jukka |title=Losing Faith in Autogyros – and Gaining It Back Again! |magazine=Sport Aviation |volume=20 |number=5 |pages=40–41 |date=May 1971 |publisher=Experimental Aircraft Association |location=Hales Corner, Wisconsin }}

• [https://www.tervis.fidisk.fi/JTsite/ate3gyrocopt.html History and photos of the ATE-3 on designer Jukka Tervamäki's personal homepage]

{{Tervamäki aircraft}}

Category:1960s Finnish sport aircraft

Category:Tervamäki aircraft

Category:Autogyros

Category:Conventional-tail aircraft

Category:V-tail aircraft

Category:single-engined pusher aircraft

Category:Aircraft with fixed tricycle landing gear

Category:aircraft first flown in 1968

Category:Single-engined piston aircraft