FAQ

Rotax Aircraft Flightpics 083

FAQ

Why does the engine not develop maximum RPM?

The main reasons:

  1. The propeller is incorrectly selected.
  2. The tachometer is faulty or unregulated.
  3. Climatic conditions. Use the formulas of reduction to standard atmospheric conditions.
  4. Engine malfunction (loss of compression, spark plug malfunction, insufficient pressure supply...).
  5. Low quality gasoline.

Why is there a dip in the region of 4000...5000 rpm when the ores are abruptly moved to increase the speed?

This phenomenon is usually associated with the depletion of the mixture:

  1. Air suction.
  2. Pump wear.
  3. Clogging of filters and/or highways.
  4. A drop in the fuel level in the carburetor.

But if you are sure that these reasons are excluded and failures have appeared when the ambient temperature decreases, it is necessary to lower the adjustment ring of the needle by one position.

Why is my engine unstable?

There are two factors affecting the stability of the engine:

  1. Fuel. In case of failures and malfunctions of the fuel system (including the carburetor), the engine speed "floats".
  2. Ignition. In case of failures and malfunctions of the ignition system, the engine "shudders".

I got a new device with 582 rotax. Unlike the old engines, the new one works at the limit of the coolant temperature.

The temperature of the coolant is a complex parameter that depends on both the cooling system and gorenje process in the combustion chamber. The causes of engine overheating by coolant temperature may be:

  1. The quality of gasoline. When running at 95, the engine is cooler than at 92.
  2. Incorrect adjustment of the carburetor. Poor mixture leads to overheating of the engine.
  3. Instrumentation. Perform calibration of the sensor and pointer.
  4. Incorrectly selected propeller. A light screw leads to the engine running on a depleted mixture and overheating.
  5. Cooling system efficiency:
  • Radiator area. The use of a "native" radiator does not guarantee the normal operation of the cooling system.
  • Cooling liquid. In summer, it is possible to dilute the coolant with distilled water. It is recommended to use imported liquids or concentrates.
  • Radiator purge. The installation of extension bushings on the screw shaft, the transition to large gear ratios, to adjustable screws lead to a deterioration of the radiator purge and a decrease in its effectiveness.
  • Radiator shading.

How to calibrate the tachometer?

The simplest method is the use of a frequency meter: The generator of a two—stroke engine gives out 6 pulses per revolution, and a four—stroke engine gives out 5 pulses per revolution. That is, for a two—stroke engine - 600 Hz = 6000ob/min, and for a four-stroke engine - 500 Hz = 6000ob/ min. You can also use an inductive frequency meter on a high-voltage wire.

There are no comments when testing the engine on the ground. But during takeoff or climb, the crankshaft rotation frequency spontaneously decreases until a complete stop.

99% of this is insufficient fuel supply to the carburetors. The reason for this may be:

  1. Malfunction (wear) of the pump.
  2. High resistance of fuel lines (hoses of unsuitable diameter, low-lying tank, clogging of filters, clogging of the drainage hole of the fuel tank).
  3. Unsuitable size of the jet in the return fuel line (if any).

I once saw an aircraft with a ROTAX like a 912, so it turned aerobatics. In our case, when trying to perform aerobatics, the engine stalls. Do regular carburetors from 912-914 allow working at negative overloads?

99% of this is insufficient fuel supply to the carburetors. The reason for this may be:

  1. Aviatics turns aerobatics on both 582 and 912. Moreover, the c 582 is better because of the lower diving torque from the propeller thrust and more stable engine operation (due to the design of the carburetor — overload does not affect the position of the plunger). Aerobatics – only on positive overloads and a short time on near-zero ones. To ensure more stable operation of the engine at near-zero overloads, the fuel level was raised to 10..11 mm from the upper section of the float chamber with the floats removed.
  2. Only diaphragm carburetors or an injection system can ensure the normal supply of fuel to the combustion chambers of the engine at negative overloads. But there are also engine lubrication and cooling systems, the fuel system of the aircraft, which should also work normally under negative overloads. So one carburetor can not solve the problem.
  3. ROTAX engines are designed for ultralight and "very light" aircraft. These are flying apparatuses with a maximum take-off weight of no more than 750 kg, a stall speed in the landing configuration of no more than 45 knots, performing non-acrobatic flights during the daytime under visual control conditions.

Non-acrobatic types of operation include:

  • any maneuvers inherent in normal flight;
  • dumping (except for the "bell" figure);
  • combat U-turns, eights of combat U-turns, steep U-turns
  • in which the roll angle does not exceed 60 °

At the request of the engine, in the event of short-term negative overloads caused by wind gusts, the occurrence of dangerous failures of the engine, its elements or power plant systems is not allowed.

For all four-stroke engines, the company guarantees normal operation for 5 seconds with a negative overload of no more than -0.5g.


The mounting flanges of carburetors on a 100-horsepower engine are constantly torn. What is the reason?

The carburetor suspension on the engine is made through an elastic rubber flange. This suspension is designed for the normal operation of the float mechanism and the absence of foaming fuel.

The main reason for premature failure of flanges:

  1. Re-tightening of the yoke.
  2. Aggressive impurities in gasoline.
  3. High idle speed.
  4. Increased vibrations:
  • imbalance of the propeller,
  • asynchronous operation of carburetors, take-
  • off and landing from the ground.

It is recommended to exclude the cantilever suspension of carburetors.

The engine does not start. The fuel is there and is coming. Checked the spark. Very weak.

It is not recommended to check the spark for breakdown. It is better to use an induction probe. For normal sparking, the crankshaft rotation speed should be at least 300 rpm. During the electric start, check the condition of the accumulator, power wires, and the mass of the starter relay.

In the case when the moment of inertia of the propeller significantly exceeded the norm, it is simply impossible to obtain the required crankshaft rotation speed with a manual starter.

The presence of fuel in the float chambers does not guarantee the required quality of the mixture to start the engine (especially cold). To facilitate the start of a cold engine, it is necessary to use concentrators, a filler syringe, an enlarged starting jet (for four-stroke engines).

When checking the contours of the ignition system, the crankshaft speed drops by the tachometer more than 300 rpm, and the sound is practically not felt.

The requirement of the instructions for installing the motor in the part of the power supply system is not met, namely: to prevent interference in the charging coils LC1 and LC2, the generator must have an electrical load (rectifier-regulator, electric motor ...) In the absence of consumers, it is necessary to connect the generator wires (yellow and yellow with a black stripe) to each other.

P.S.: No need to shout that this is a KZ…

The three-phase rectifier regulator has four wires: three yellow and one black. How to connect them to the power supply system?

In full accordance with the instructions. Any two yellow wires to the generator, black — output "+", housing — output "-". The third yellow is superfluous, it must be insulated.

I assembled an electrical circuit with a three-phase rectifier-regulator ("hedgehog"). The voltage is significantly different from 12 V.

A failure of the generator and/or the rectifier-regulator is possible, but this is unlikely. Most likely, the circuit lacks the capacity necessary for the correct operation of the rectifier-regulator. A capacitor and/or a charged serviceable battery can act as a capacity.

Is it possible to use a car ignition lock instead of an ignition switch?

In most cases, a car lock is considered as an "anti-theft" tool and/or a "gadget". He has zero anti-theft, because he cut two black and yellow wires and that's it. As a gimmick or security, it's clearer, but:

  1. Before takeoff, it is necessary to check the ignition system by alternately turning off/on the ignition circuit.
  2. The failure of one lock will lead to the failure of the dual-circuit ignition system, which negates the duplication of the system.