Cessna 210 Centurion / Turbo Centurion 210C; 210D
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 37; Flight Crew Total 2234; Flight Crew Type 945
Situational Awareness
Aircraft Equipment Problem Critical; Ground Event / Encounter Gear Up Landing
Aircraft Aircraft Damaged; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Maintenance Action
Aircraft
I was on approach in day VFR conditions in a Cessna 210.  I selected gear down with the gear select handle.  The green gear-down light did not illuminate.I elected to divert to ZZZ and ran the emergency procedures checklist for landing gear malfunction.  This included utilizing the hand pump to manually pump the gear down.  To my surprise; upon exercising the hand pump; no resistance was felt.  This indicated to me an absence of hydraulic fluid in the gear extension system.With the aircraft flying at a suitable altitude on autopilot; I removed the cover panel from the right side of the center pedestal; and removed the dipstick for the hydraulic fluid reservoir.  It indicated no fluid present.  I then elected to attempt to fill the reservoir with the available liquid on hand; a 1-liter bottle of water.  I poured the entire bottle into the reservoir and exercised the hand pump; but still felt no resistance and was unable to lower the main gear into position.After notifying people on the ground by radio that I would likely need to execute a gear-up landing; and requesting that they notify the Fire Department to be on hand; I climbed to altitude and attempted several other procedures to bring the main gear legs forward and lock them into place.  None of these attempts were successful.I could see in the gear mirror that my nose gear was down and apparently locked.I returned to ZZZ; announced my intention to make an emergency gear-up landing on Runway XX; and executed a full-flaps landing at minimum airspeed.  On short final I elected to pull the mixture to full lean cutoff and turn off the engine ignition as well as the electrical system master.  After touchdown the aircraft rolled on its nose wheel and skidded on its tail tie-down ring; eventually leaning to the left whereupon contact with the asphalt runway was made by the left horizontal stabilizer and aft-most portion of the left wingtip fairing.  The aircraft came to a halt left of centerline but prior to exiting the paved surface of the runway.I exited the aircraft and walked around it to assess for the possibility of fire.  I saw none; and was also pleased to see that the propeller tips showed no signs of ground contact.  External damage appeared to be limited to gear doors; the main gear door fairing aft of the left main gear well; the left stabilizer and elevator; and a very minor scrape on the aft tip of the left wing fairing.  Hydraulic fluid was noted to be dripping from the area of the nose gear.  An aircraft mechanic on the scene noted the apparent separation of a hydraulic hose from its swaged fitting.  This hydraulic hose was connected to the nose gear door actuator.In retrospect I believe it is possible I could have averted the gear up landing by not touching the gear handle after I noticed the green gear-down-and-locked light had failed to illuminate.  In the system on this aircraft; the sequence of events is doors-open; gear-down; doors-close.  I glanced out my pilot-side window and saw a tire in position on the left main landing gear.  I don't know whether it was in position on the right but suspect now that it was.  I then tried to debug the system by cycling the gear handle; but if I had simply left it alone; I think the condition would have been gear down and locked; gear doors open; which would not have been problematic.  The hose that failed was on the door-closing side of the nose gear door actuator.  I now think of the green gear status light as a 'gear-sequence-concluded-and-doors-closed' indication; whereas before I used to equate it with 'gear-down-and-locked'.  It really doesn't mean that; gear down and locked occurs without that light illuminating necessarily.
C210 pilot reported a partial gear extended landing following an apparent hydraulic system failure.