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6 Answers

Cessna 172RG landing gear system

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Aircraft Systems, Commercial Pilot

Hey, I just need a little clarification on the 172RG's landing gear.  From what I can tell from my POH and the ASA commercial oral test prep book, which focuses on the RG, it seems like the landing gear is held down by down locks, and held up by positive hydraulic pressure.  I'm assuming that means if you lose hydraulic pressure, the gear will free fall.  Conversely, my CFI is insistant that if you lose all hydraulic pressure, the gear will just be stuck in whatever position it was in, so if you lose hydraulic fluid while the gear is up, they will remain there.  Which is the correct answer?  Thanks for the help!

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6 Answers

  1. John D Collins on Sep 10, 2013

    I expect your instructor is correct. There is an emergency hydraulic pump that is used in the event of the electrical hydraulic pump failure. The gear may come down partially without hydraulic pressure, but they won’t be in the full down and locked position. The POH indicates that the emergency gear hydraulic hand pump is only to be used to extend the landing gear and not to retract it. So if a hand pump was not needed to extend the gear and get it down and locked, it would be unnecessary. Obviously, it is needed. I don’t know how far the gear will come down without hydraulic fluid, but it certainly won’t come down all the way. On some other aircraft types, the system is similar, but the gear will free fall to the down and locked position, so its emergency procedure for extension is to operate a hydraulic switch lever that releases pressure from the system so it free falls.

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  2. Best Answer

    Donnie on Sep 10, 2013

    On Pipers, the releasing of hydraulic pressure does allow the to drop and lock. Cessna RG’s are different in that they retract in a trailing fashion. In order to be down and locked, the gear must be forced forward against the relative wind. Gravity alone doesn’t do this.

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  3. Fly92020 on Sep 12, 2013

    Carry a broomstick in the backseat (NOT in the baggage compartment). That’s what we used to do on the Cutlass; use it to poke the gear into a ‘locked’ position.

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  4. Mark Kolber on Sep 13, 2013

    The broomstick idea is sooo funny. But the better one is the method an instructor once demonstrated to me: open he door, stand on the threshold and, with one foot inside the plane on the threshold, kick the gear down with your other foot. 😀

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  5. Jason on Jan 14, 2014

    Okay, another CFI here going to chime in on this one. Your instructor is correct with the gear being held up with pressure, however he/she is sadly mistaken about the rest. I too fly and train fellow pilots in a C172R and C172RG in Pompano Beach FL at American Flyers. If the RG begins to lose hydraulic pressure, the gear will dangle. There is no such thing as a gear up landing in the RG, unless for whatever reason the pilot forgets to extend the gear which is beyond my belief since you have a gear warning horn anytime the power is reduced below 15 inches of manifold pressure and or with the flaps extended. If you hear the power pack constantly turning on and then back off, the pilot should put the gear and leave it down. The power pack is designed to maintain 1500 psi throughout the system and kick on when the pressure drops below 1000 psi. If you notice the power pack turning on and off it is and you are most definitely losing hydraulic pressure. Put the gear down and leave it down while you still have fluid, if you don’t you are surely asking for an emergency. Also, with no hydraulic fluid, the emergency gear extension hand pump is of no use to the pilot. The hand pump is mostly going to be used in the event of an electrical failure, and since the gear is electrically activated and hydraulically actuated, you have no way to extend and lock the gear down without the electronics, except for the hand pump. In any case, ALWAYS revert to the checklist. Hope this helped!

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  6. Zach Morgan on Apr 29, 2017

    Thank you Jason. I am a CFI in Missouri at the University of Central Missouri and was thinking I was going to have to write the novel, but I finally came across your response. You nailed it on the head.

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