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Sub Menu: GENESIS - Aircraft Design Details
IntroductionMultipurpose Landing GearTelescopic WingInterconnected Propeller Drive
Modular FuselageSimplicity of OperationAerodynamicsDesign Verification
SpecificationsComparison to the CompetitionSafetyReliability
MarketFrequently Asked QuestionsConclusionPatents

Interconnected Propeller Drive
Gevers Aircraft, Inc. * GENESIS *

The wing mounted props are belt driven from fuselage mounted engines.

Safety is greatly improved with the Genesis. The twin engine twin propeller arrangement has both engines connected together to both propellers in such a way that during an engine failure both propellers are still powered equally by the remaining engine. As a result no action is required by the pilot to maintain directional control during an engine failure because there is no asymmetric thrust only a decrease in total power. In normal operation the propellers will be coupled together and are driven at the same RPM. However, they can be coupled and decoupled in flight from the cockpit at the pilot's discretion. Engine out rate of climb is also significantly improved with this design.

Cross section Plan view
This interconnected propeller system gives the Genesis the operational ease of a single engine design with twin engine performance and greater safety than both. This is a very simple mechanical fail-safe system. Two engines are mounted facing each other in the fuselage directly above the main landing gear. They both drive into a common, simple gearbox through overrunning clutches. The gearbox drives two constant speed props through a triple set of redundant timing belts and pulleys. The 3 parallel belts in each set are separated by partitions preventing a failed belt from becoming entangled with the others. Belt drives are becoming common in new production helicopters along with experimental and FAR part 23 aircraft. This belt system is lighter and more reliable than a gearbox system because there are three belts in parallel providing a triple redundant fail safe advantage that a conventional gearbox system does not have. No power is transmitted through the gearbox unless one engine is shut down.

The high reliability of timing belts is well known. Failures of these components occur from misalignment, contamination, and shock loads. Alignment and lack of contamination are guaranteed by this design. And if shock loads occur (prop striking an object), we want the belt to fail rather than the engine. Belts in a properly designed system will last longer than the engine overhaul time (and will be replaced at overhaul).

Overrunning clutches provide single engine simplicity with multi-engine reliability.
During normal operation both engines produce nearly the same power, and are geared together so they run at exactly the same RPM. The engines power a common gearbox, which in turn drives both propellers and provides automatic synchronization. There are two instances in which the engines would not operate as one.

In the first case, one engine produces so little power that it can't maintain the RPM at which the other engine is running. For example, during a catastrophic engine failure or even when one engine is at 75% power and the other is at idle. Here the overrunning clutch on the dead or idling engine allows it to "drop out" so it doesn't contribute any detrimental drag on the other engine. In fact, it can even be shut off and re-started while the other engine powers the gearbox and both propellers. One engine can suddenly loose power (and even come to a stop) and the other engine automatically assumes the load of both propellers - no asymmetric thrust. The "dead" engine does not load down the running engine.

It should be noted that one engine driving both props is more efficient (and much safer) than the conventional situation of one engine driving one propeller. Two props running at half power produce more thrust than one prop at full power. This design also avoids the asymmetric thrust which causes the aircraft to assume a dangerous high drag producing configuration.

A second situation in which the engines would not run at the same RPM is produced when the pilot elects to de-couple the props. This is done with a cockpit control which separates two gears in the gearbox. Each engine drives its respective propeller as in conventional designs. The overrunning clutches are still in the drive system.

Decoupling is required in the unlikely event of a propeller failure, in which the offending prop must be shut down. Note that in the case of a runaway prop (pitch goes to low - RPM goes out of control) the overspeeding prop cannot damage the engine by forcing it to a higher RPM. In fact the propeller speed governor located on the engine prevents engine overspeed even when the load is suddenly removed.

Internal fuselage mounted engines.
Cross section Side view
Hinged side panels in the fuselage allow for easy access to both engines for maintenance.

Locating the engines above the center main landing gear is structurally beneficial because the landing forces from the engines are transmitted directly to the main gear without passing through the wing structure.

The majority of aircraft noise comes from engine exhaust and the propellers. Noise levels in the Genesis cabin are decreased because the exhaust and propellers are well behind the passengers and sound baffling can be used in the engine compartment similar to a car. Whereas a typical single engine aircraft has the prop directly infront of the cabin and the exhaust below the pilot's feet and a typical twin has both the exhaust and props right next to the passengers on both sides. So the Genesis is much quieter than conventional twin or single engine aircraft.

Eliminating the engine nacelles from the wing reduces drag and returns that section of wing to a smooth lift generating surface.

With the engines internally mounted better temperature control for the engines is possible over the range of flight conditions from ground operation to cruise. Forced airflow through the engine compartment gives the pilot direct control of cooling when hot as well as heating in cold environments.

Placing both engines near the C.G. greatly reduces the rotational moment of inertia of the aircraft, which improves spin control and safety. The C.G. is also kept low in this arrangement improving high-speed taxi maneuvering in the water and on land.

Movable propeller arms.
Cruise Hard surface

Mounting the engines internally and driving the propellers through timing belts allows for the propellers to be mounted on arms that can be rotated clear of the ground and water spray. This also eliminates the possibility of passengers and ground personnel from coming into contact with a running propeller. For cruise, the props are positioned so the thrust line matches the drag line. This eliminates the inefficiencies of a typical amphibian where the high thrust line creates a large nose down pitching moment in cruise. The propellers are mounted on the upper end of the outrigger landing gear leg. When the landing gear is extended the props automatically raise.

Cockpit Controls:
The overrunning clutches and central power gearbox allow for improvements in engine controls. The pilot no longer has to look at instruments inside the cockpit to synchronize engines during the critical takeoff period when he needs to be looking outside. There is one lever for engaging and disengaging the gearbox to connect the propellers. When engaged, both throttle and both "Prop" levers act together so operation is similar to a single engine aircraft. Power changes can be done without the need to match engines by referring to the manifold pressure gages and tachometers. When the gearbox is disengaged, the controls are identical to a conventional twin engine aircraft.

The propeller arms are part of the landing gear outriggers so they move automatically when the gear extends or retracts and the pilot does not need to actuate or monitor them separately.



GENESIS SECTION SUB MENU: Introduction.. Multipurpose Landing Gear.. Telescopic Wing.. Interconnected Propeller Drive.. Modular Fuselage.. Simplicity of Operation.. Aerodynamics.. Design Verification.. Specifications.. Comparison to the Competition.. Safety.. Reliability.. Market.. Frequently Asked Questions.. Conclusion.. Patents

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