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What Hydraulics are found on a Cessna 150 or 172 – What answer to give the DPE on Checkride?

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Aircraft Systems, Flight Instructor, Private Pilot, Student Pilot

So on a Cessna 150/172 and the like, the brakes work via hydraulic principles, and pushing the brake pedal, much like in a car, forces the brake fluid through a tube to the brakes next to the wheel, and braking occurs. Wonderful.

So if  a check ride question come up asking what are the hydraulic systems on a 150, is there anything besides the brakes that should be mentioned?  Would the wheel shimmy dampening cylinder be considered a hydraulic system? How about the oleo struts on the nose wheel? When priming the engine with several squirts of fluid, does that employ hydraulic principles and therefore should it be mentioned as well?

Just trying to cover all the bases here. There are some local DPEs who are real sticklers. As a local wag recently told me...  "if you want a 4 hour oral on the private check ride, I've got your man. "

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2 Answers



  1. ayavner on Apr 13, 2021

    For those planes, yeah just the disc brake system. You could certainly make sure to mention that your oleo struts and shimmy dampener also work on hydraulic principals, but in the context of a “system” your brakes are about it.

    Other planes are different and might have hydraulically actuated gear or flaps etc, but not the case here. Good luck and don’t overthink it!! 🙂

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  2. KDS on Apr 13, 2021

    I certainly agree with the do not overthink it recommendation. Despite what you may hear, the examiner WANTS you to pass. At the same time, they want to ensure you can operate safely, so they are not going to ignore issues, but they really are on your side during the test.

    As far as the brakes go, you might also understand that each one is independent. Each rudder pedal has its own master cylinder and the lines do not connect. Additionally, you should know that you check for the presences of leaked hydraulic fluid during a preflight. Although, it is an old Marine joke that when asked what it means if you come out to your aircraft and it is not leaking hydraulic fluid that the correct answer is that means it is out of hydraulic fluid. But, keep that one to yourself for a time other than a test.

    Good luck. I know you will do fine.

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