Aircraft Systems and Flight.

Cessna Citation CJ3 Hydraulic Systems and Operation.

The CJ3 business jet is a very reliable aircraft, It’s the perfect combination of range, speed and operating economics (Cessna 2004). One of the most important system of this aircraft is the hydraulic system.

The Hydraulic system permits the application of force by converting a volume of fluid flow into pressure on a hydraulic piston motor, in other words hydraulic pressure is converted into force to move a component of the aircraft. The hydraulic systems of the CJ3 is defined as open center hydraulic system which means that the hydraulic fluid is constantly circulating in the system at low pressure and it increases its pressure during the operation of the landing gear, speed breaks and flaps. The break system use a separate independent hydraulic system but, the same type of hydraulic fluid is used. 

One of the additional benefits of an open center hydraulic system is that this low pressure greatly reduces the quantity of hydraulic fluid required in the reservoir because there is minimum heat buildup (Cessna 2004), also it has a longer hydraulic pump life span, reduces leakage rates.

The hydraulic system is configure with two engine-driven pumps that pressurizes to 1500 PSI. When either of the three systems: the landing gear, flaps, or speed breaks are actuated, the loading valve in the hydraulic line closes, enabling the system to pressurize to1500 PSI. At the same time, either of the systems demanded by the pilot (e.g. the speed brakes) the control valve opens, allowing the pressurized flow into the selected system. In addition, a relief valve maintains the pressure at 1500 PSI and works in parallel with the loading valve keeping the pressure in the system. Once the selected systems completed its cycle (e.g. the speed brakes have extended) the systems returns to its initial stage, by closing the respective control valve, reverting to the low pressure, open center stage. 

During fight the systems remains in open center stage, during this stage the system is unlikely to fail unless a leakage or cavitation in the hydraulic pumps have occur. However, if one of the pumps fails during flights it’s an indication that the pump flow rate is below normal or a leak in the system is possible, with the remaining pump working its best to land as soon as practical. The situation could get worse if both pumps fail because the flaps, speed brakes and landing gear will be in operative. 

The required airmanship and experience of the crew to handle this type of in-fight emergency is critical, although abnormal procures checklist and standard operating procedures are usually establish in checklist and training. It’s important to understand that all scenarios are not practical for every emergency and not all emergencies happen in the same scenario. The best response to an emergency is the product of understanding the function and limitations of as systems so, when it fails you can determine the best course of action.

Below is a picture of the hydraulic schematic of the Citation CJ3

Manuel Gamarra

 

References.

Cessna Textron Aviation. (2004). Cessna Citation CJ3/CJ3+. https://cessna.txtav.com/en/citation/cj3