Hiller HJ-1
| Hiller HJ-1 Hornet | |
|---|---|
|
|
| Type: | helicopter |
| Design country: | |
| Manufacturer: | |
| First flight: |
1950 |
| Number of pieces: |
18th |
The Hiller HJ-1 Hornet is a blade tip drive helicopter from the US helicopter manufacturer Hiller Aircraft .
history
The civil prototypes
Stanley Hiller began developing the HJ-1 Hornet as a single-seat sports helicopter in 1948 . Significant development work went into the ramjets , each weighing just 5 kg , each of which developed just under 14 kp (137 N) of thrust. Early ideas with deflagration jets were abandoned in favor of ramjets; The long-term goal was - despite the high g-load - the use of small jet engines .
The first prototype with a cell made of steel and aluminum tubes flew in 1950 without any fuselage fairing. The second prototype was already equipped with two seats arranged side by side and a cabin made of fiberglass - one of the first applications of this material in aircraft construction. The third HJ-1 was created as a model for series production, which was planned to cost $ 5,000; that was the equivalent of a luxury-class Cadillac . The cockpit had been significantly enlarged, at the same time the empty weight rose from 160 to 230 kg; the possible cruising altitude sank to 2100 m. For the first time, the rotor blades were made entirely of steel.
Military advancement
The military orders for the Hiller UH-12 with a total of 2000 units produced after the beginning of the Korean War blocked the planned production capacities for the civil helicopter. In 1952 Hiller sold three "HJ-1" under the designation "XHOE-1" to the US Navy, which was looking for an ultra-light aircraft for the Marine Corps . The US Army , which compared to the Marine Corps lagged behind in the use of helicopters, also ordered two "HJ-1" under the designation "YH-32" as a possibly inexpensive replacement of the Jeep for connection tasks , for laying cables and as an observation platform. Before delivery to the military at the end of 1954, the tail boom was lengthened a little and two horizontal stabilizing fins were added to improve stability in forward flight. The late delivery was also due to the approval according to "Civil Aviation Authority Standards", which Hiller continued in addition to the military approval.
The US Army ordered 12 more YH-32s for extensive operational testing. Due to the systemic restrictions, the well-developed project was abandoned around 1956.
construction
To start the ramjet engines, a 50 hp petrol engine brought the rotor to a speed of 150 min −1 . This corresponded to a circumferential speed of around 200 km / h at which a glow plug each ignited the engines, which were already loaded with almost 90 g. The glow plugs had the designation “flame-holder” because they also supported combustion after starting. Gasoline, kerosene or diesel oil could be used as fuel, other sources also indicate alcohol. The operating speed was 550 min −1 , which corresponded to a blade tip speed of 715 km / h and almost 1200 g on the ramjet engines. The high g-load also explains why gas turbines could not be used here.
It can be assumed that the ability to steer around the vertical axis was generally unsatisfactory, as the conventional rudder used initially on the YH-32 was replaced by a V-tail that was angled downwards . In principle, no tail rotor was actually necessary because the blade tip drive did not transfer any torque to the airframe. In at least one YH-32, however, the tail unit was removed and replaced by a conventional tail rotor.
use
The demanding flight characteristics during autorotation in the event of an engine failure caused major operational problems . The ramjet engines generated considerable drag when there was no thrust; accordingly, the rate of descent during the autorotation of 15 m / s was about twice as high as with conventional helicopters.
The fuel consumption was about ten times what would have been expected for a conventional design. The maximum amount of fuel of 136 kg was sufficient for 30 minutes - including take-off and landing. This meant that a maximum range of 50 km could only be achieved. The planned military use was also counteracted by the design-related extreme noise development and the bright flames from the ramjet engines, which merged into a radiant circle at night.
Technical specifications
| Parameter | Data |
|---|---|
| crew | 2 |
| length | 3.9 m |
| Rotor diameter | 6.9 m |
| height | 2.4 m |
| Empty mass | 243 kg |
| Max. Takeoff mass | 489 kg |
| Top speed | 62 kts |
| Range | 30 NM |
| Engines | two Hiller 8RJ2B ramjet engines
with a total of 27 kg of thrust |
See also
Web links
Individual evidence
- ↑ a b c Hiller XHOE-1 Hornet. In: National Air and Space Museum. Smithsonian Institution, accessed March 19, 2018 .
- ↑ Kermit Weeks: 1956 Hiller Hornet. Fantasy of Flight, accessed on April 10, 2016 (English): "If it'll burn, it'll turn!"
- ↑ Michael JH Taylor: Military Prototypes of the 1950s (Warbirds Illustrated No. 18) , Arms and Armor Press, 1983, ISBN 0-85368-579-7 , p. 50