Hello Helicopter Enthusiast,
As a business plan, I had envisioned taking the Sikorsky S-52-3 helicopter, which I was very familiar with, and turn it into a kit. It would be the only four-passenger helicopter kit on the market; it was simple in design, easy to fly, aesthetically appealing and most of all it went thru FAA certification. While my wife and I lived in Guangzhou, China, I laid out my plans. At the time, I was working for Orlando Helicopter Airways and managing a joint-venture helicopter manufacturing plant in Guangzhou.
Upon returning to Florida in 1988, the first prototype was test flown. In 1988, I started Vertical Aviation Technologies, Inc. and in 1991 I began delivering Hummingbird kits around the world. Up until 1993 eleven kits were sold and all but one had been completed and flown.
In 1993, I began the development and certification of a nine-passenger Transport Category quiet helicopter appropriately named the Whisper Jet. Development and FAA Certification to make the world’s quietest production helicopter took nine years and included a new five bladed quiet rotor system and silencers on the turbine power plant.
As you can imagine, a lot of my resources and attention were away from the Hummingbird program until 2001. From that time until now, I have spent redesigning the Hummingbird with the Lycoming which has included extensive flight testing just like the Whisper Jet program. Other aircraft were built for customers as well like a special arctic equipped helicopter for Lockheed Martin.
I was very familiar with the S-52 helicopter because of my father, Fred Clark, had owned and operated many S-52’s. He has approximately 2500 hours fly S-52’s from sightseeing rides at Cape Kennedy and agricultural spraying. His company, Orlando Helicopter Airways, can be remembered by the Winnebago Helicamper, electric and propane powered helicopters, Russian Mi-24 Hind drone simulators, as well as S-55 and S-58T airliners.
The biggest challenge with the Hummingbird program was to take an FAA Type Certificated helicopter and structure the build process so the average person could finish the job accurately. Because all transmissions are shaft driven, there was no room for misalignment's. I manufactured all of the aluminum hydroform dies and alignment fixtures using the Sikorsky drawings I acquired. I own every drawing of the Sikorsky S-52, including every engineering report, process specification, and flight test report; including FAA certification reports.
The lower cabin section is first assembled and pilot drilled on a fixture at our factory. It is shipped to the builder disassembled. The builder cleco’s it back together, fabricates and adds angles, etc. to it and performs the final riveting. The structure is aluminum 2024-T3. The upper cabin and firewall assembly is assembled and riveted on fixtures at the factory. The builder simply sets it on the lower section and rivets them together. No alignment concerns because all the hard points have already been located. Next the landing gear is assembled and installed. Now your aircraft is on wheels and can easily be moved around.
The nose/windshield, instrument panel and composite doors make up the next stage. The windshield is FAA approved for the Bell 206L Longranger. The nose is composite and comes ready to install. Section 5 is the tail. Again, the tail cone is riveted together at the factory on fixtures. The builder assembles and installs the horizontal and vertical stabilizers. The tail section includes intermediate and tail gearboxes. Both are assembled and tested at the factory. The tail rotor blades are painted and balanced to the hub and require installation only. The next section is the main rotorhead, main gearbox, and tail shafting. All are assembled and tested at the factory and require only installation. Flight controls go in next and include dual controls with electric trim. The power plant section includes every item to install the IO-540 or the LS7. This includes the clutch and freewheel unit and a 75 amp Skytronics alternator. These engines are dry sump oil systems, so a three gallon oil tank is mounted on the firewall. After the power plant comes the fuel system. The fuel cell bladder holds 57 gallons. One electric fuel pump mounts on the firewall with the strainer. One engine driven fuel pump mounts on the engine assessory case. The LS7 uses two electric fuel pumps.
The next section is the electrical which includes the following gauges: dual tachometer, air speed, altimeter, manifold pressure, transmission oil pressure, cylinder head temperature, volt/ampmeter, fuel pressure, engine oil pressure, engine oil temperature, and fuel quantity. All wiring and connectors are supplied. Warning lights can include chip detectors for gearboxes and engine, alternator and rotor brake. Wrapping up the kit is the two front composite seats and composite cowling. They are made at the factory and require installation of camloc fasteners. We use only epoxy resin, no polyesters. Polyester is for boats.
The last section is the main rotor blades. Redesigned using the original aluminum extrusion design with aluminum pockets hot bonded to the spar. Each blade has a 7 degree twist. The blades are painted and balanced ready for installation.
This kit comes very complete and includes every nut, bolt, washer, switch, circuit breaker, bus bar, wiring, connector, canon plug, etc. Total build time is documented by builders at 1200 hours. There is no welding and no composite work required. The kit is eligible for the 51% rule including our Quickbuild option. Major modifications made to the original Type Design include the nose/windshield, instrument panel, composite doors, seats, flight control system improvements, powerplant, composite cowling, tail stabilizer, rotor blades as well as many smaller improvements too numerous to mention. Even components like the main rotorshaft are redesigned with better materials and manufacturing processes. All modifications meet or exceed FAR 27 – Airworthiness Standards: Normal Category Rotorcraft. The new nose is FAA approved by Ralph Alex (DER); the retired chief engineer, Aircraft Design and Development, Sikorsky Aircraft.
This helicopter is a real pleasure to fly. Forward flight is very stabile and very agile because of its inherently long tail. The S-52 was the first helicopter to perform loops. The new stabilizers were moved forward on the tail. This helped with hover stability and tail rotor authority. Improvements to the flight control system included a new mixing unit design and an electric cyclic trim system. This trim system has force gradient (spring) control rods that center the cyclic stick where positioned during flight with electric motors. The electric motors incorporate clutches so this spring pressure can also be switched off such as in a hover. In a hover, stick forces are so light it feels like the controls are hydraulically boosted.
Another appealing characteristic is actually on the ground; wheels. It is such a pleasure to be able to taxi a helicopter and not have to hover. This can only be found on helicopters costing over a million dollars. Even man handling in and out of the hangar is quicker and easier than ground handling wheels. Under high density altitude conditions running takeoffs can easily be accomplished. Maximum gross weight is 2800 lbs. Useful load is 950 lbs. The fuel tank holds 57 gallons. The Fuel Injected Titan engine burns 15 gallons per hour. The LS7 burn 13 gallons per hour. Cruising at 90 knots the range is better than 375 miles. The IO-540 provides plenty of power and is a pleasure to fly. The throttle is synchronized with the collective. An electronic governor is available.
The three-bladed rotor system is very smooth and has a medium inertia rotor providing good autorotation characteristics. Adding throttle brings the rotor rpm right back up. Main rotor disc loading is only 3.1 lbs per square foot. Rotor rpm is 320.
Another desirable characteristic of the Hummingbird is the large cabin interior. Inside width is 58”. Flight controls run under the floor so visibility is not impaired by controls running up thru the cabin. Large baggage areas are located under the pilot and co-pilot seats. Two people, 375-mile range and 220 lbs of camping gear! For engaging the rotor system, the clutch is automatic. A rotorbrake is included to slow the rotor during shut down.
When you finish building your Hummingbird, it is licensed in the amateur built category but it is as close to a Type Certificated production helicopter as you can get plus you get the pleasure of learning all about it while building. We spent a great deal of money and time developing instruction/service manuals, drawings, photographs, etc. to assist building this kit. When you’re finished, we have a test pilot/technician that can assist in final rigging/blade tracking and testing.
Vertical Aviation Technologies specializes in helicopter research, development, design, and manufacturing and is located at the Orlando-Sanford International Airport in Sanford, Florida approximately fifteen miles north of Orlando.
I hope to assist you in one day owning your very own helicopter.
Bradley G. Clark