IElectric drive for chassis cleaning, in addition to significantly larger overall dimensions and weight compared to hydraulic cylinders, have one more drawback. The most likely reason for the failure of the electric drive is the failure of the electrical part. Short circuit in the circuit, burnout of the motor windings, etc. The drive is located outside the cabin and is subject to external influences, which can cause a failure. First of all, it’s getting moisture. In addition, the failure of the electric drive can not be neutralized. If the drive motor does not rotate, the drive will no longer move. And if one of the three drives fails, and in the cycle of release or cleaning, one rack «hangs» in an intermediate position. And you can not do anything. The hydraulic cylinder can be considered an absolutely reliable device. The failure of the hydraulic drive is 99.9% failure of the pressure source. And the most likely reason for this failure is the loss of working fluid due to leakage failure. But in this case, all three racks will not budge. That is, if they were released, then the plane returns to the airfield and lands as usual. If the chassis is not released, then sit on the «belly». This is less evil than landing on one, or without one rack.