North American Rotorwerks


Why is the engine in front?Tractor Engine Advantages

Positive dynamic stability

Tractors are naturally stable. Thrust coming from the most forward part of the airframe has the inherent tendency to stay in line of the direction of travel. There is no substitute for the stability gained in having the propeller up front.

Propeller to Rotor blade clearance

Distance between the rotating parts is just one of the obvious advantages of the tractor design. There is no known case of P.I.O. (Pilot induced oscillation) and subsequent propeller to rotor contact in the Original Tractor Autogiros of the 20ís & 30ís.

Center line thrust

All tractors are consistent in having good center line thrust.

Pilot reference

Pilot position in relation to the rest of the airframe plays a very significant role in stability. To best sense the movement and direction of the aircraft the pilot should have at least some of the gyro ahead of his or her vision. This makes coordination of the controls easy and accurate.

Propeller size

Due to the tractorís propeller clearance, it has a larger propeller, which makes for better performance in the flight envelope gyros excel at (short takeoff, slow flight, hover and angle of climb).

Ample clean air

To maximize any propellerís thrust, it is crucial that it has a clean supply of air with no obstructions before it. Having to pull air around seats, frame members, and even the pilot, produces a dirty, erratic supply to the propeller.

First hint of a problem

Whether it be visually seeing an oil leak or smelling a scent of something wrong, having the engine up front gives the pilot an early warning.

Foreign objects

At one time, exhaust failures with engines on ultralight aircraft were the source of many accidents on pusher aircraft, if anything were to get loose and come off, it would not end up going through the propeller in a tractor configuration. Also small rocks and anything the wheels can lift up wonít find their way into the propeller on a tractor.

Propeller failure

Although very rare, the case of piece of the propeller coming off has little chance of hitting the frame or rotor blade in a vulnerable spot on the tractor.

Injury from propeller

Even in general aviation there are accidents where the plane is running with no one at the controls and the plane gets away. With the tractor, the aircraft will most likely go away from the person standing beside it and not into them as would a pusher.

Protection up front

In the case of a crash, the pilot fairs greatly in comparison to a framework where there is no protection in front of them and the heavy mass of the engine behind them.

Water and float flying

There is clearly no better position for the propeller than in front, ahead of the spray that the floats produce on the beginning of the take-off run. Even a short amount of time can erode a propeller leading edge if allowed to be in the line of the spray.

Sound

Noise decibels from a tractor aircraft are always far lower than for the same engine propeller combination in a pusher.

Stresses in the mast

In the tractor configuration, the mast is relieved of the typical stresses the engine is producing mounted on and right behind it, pushing in the opposite direction from the forces the rotors are inducing.

Balanced center of gravity

In the tractor configuration there is correct balance for flight, whether the gyro is lightly loaded or is at full gross weight.

Engine cooling

Whether water or air cooled, front placement offers the most efficient position for cooling.


North American Rotorwerks