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gear collapse, no uplocks?

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elmar.hegenauer(at)telus.
Guest

Posted: Mon Mar 31, 2008 8:23 am Post subject: gear collapse, no uplocks?

I have a thought  here..................

  

 Some of the CJs (incl. mine) have no  uplocks.

 The gear is solely kept in the wells by  the

 air pressure in the actuators, what on the  other

 hand puts quite some  stress on the bolts, studs 

 and brackets, especially doing aerobatics and 

 pulling Gs.

 When I come out of a loop, I can see the red  gear

 lights going out and the air pressure gauge  needle

 climbing up until  the pressure relief valve kicks in.  

  

 cheers

  

 Elmar

  

   [quote][b]

jblake207(at)COMCAST.NET
Guest

Posted: Mon Mar 31, 2008 3:13 pm Post subject: gear collapse, no uplocks?

I leave my gear handle in the “UP” position during flight.  I’ve been told to move to neutral.  Does it matter?  

     

Respectfully,  

Jon Blake  

   

  

--

adsavarese(at)hotmail.com
Guest

Posted: Mon Mar 31, 2008 3:44 pm Post subject: gear collapse, no uplocks?

FWIW Jon, depressurizing the landing gear actuators by putting  the gear handle in neutral can cause the gear to slam when placing the gear  handle into the down position.  The reason being; you are depressurizing  the actuators.  With no pressure in the actuators, there is no "shock  absorption" from the air escaping in the actuator when the gear handle is placed  in neutral.  As the air pressure is applied to one side of the actuator,  the other side is depressurizing.  Thus, the shock absorption.  With  no uplocks and the gear handle in neutral, the gear will have the opportunity  move freely with g-loads.

  

 The only way to prevent the gear from slamming after the gear  handle is put in the neutral position is to move the gear handle back to the  previous position.  Then move the gear handle to the down position and the  gear will not slam down.

  

 Test this the next time you have the airplane on jacks.   Raise the landing gear.  Then put the gear handle in neutral.  After  the air exhausts, put the gear handle down.  The landing gear will slam  into position.  Then try it with not putting the handle in neutral.   ie: leave the gear handle in the up position.  Move the handle down and see  how smoothly the gear goes into the down and locked position.

  

 One last comment.  You will use more air from the main  air tank when you depressurize the actuators by moving the gear handle to  neutral.

 Dennis

  

 [quote]   ---

wlannon(at)persona.ca
Guest

Posted: Mon Mar 31, 2008 6:22 pm Post subject: gear collapse, no uplocks?

Dennis, et al;

  

 I have no knowledge of the Yak gear procedure.  The manual procedure for the CJ specifies the lever to neutral after retraction.  The first step in extending the gear is "Gear Lever UP" for the reasons you  have noted and is included on the cockpit placards I supply.

  

 The 50/52 and the CJ main gear are totally  different and cannot be compared in operation.

  

 Having said all that, I expect that many CJ pilots  do not use the neutral position (including yours truly most of the time!) and  there are a number of CJ's with no uplocks so pressure on these must be  maintained. Uplocks were removed for at time by the PLAAF (though perhaps only  individual bases) during the 1970's, probably in response to uplock release  failure. No one seems to know the whole story.

  

 Moving the gear lever to neutral with the gear UP  would certainly remove all the load from the adaptor fitting ( item that failed  on Blitz's aircraft). Otherwise that fitting will be under continuous pressure  since the actuator, in the extended position, is, by design, 3mm short of it's  fully extended position.

  

 In the DOWN position, assuming that the overcenter  and the gap between the overcenter stop faces are correctly adjusted, the  adaptor is also unloaded. In this case the actuator is fully retracted and  the ball lock engaged. The proper gap setting ensures that the ball lock is not  restricted from engagement and the adaptor fitting carries no load.

  

 What all this seems to imply is that there is a  reason for the "lever neutral" procedure. Maybe also explains why the factory  hard chrome process on this part is apparently inadequate for a highly  loaded item. The only load it would carry is the weight of the gear  during transit.

  

 Cheers;

 Walt  

  

 [quote]   ---

ByronMFox(at)aol.com
Guest

Posted: Mon Mar 31, 2008 7:32 pm Post subject: gear collapse, no uplocks?

In a message dated 3/31/08 7:23:21 PM, wlannon(at)persona.ca writes:

 

 

  	  Quote: 	
		  Moving the gear lever to neutral with the gear UP would certainly remove all the load from the adaptor fitting ( item that failed on Blitz's aircraft). Otherwise that fitting will be under continuous pressure since the actuator, in the extended position, is, by design, 3mm short of it's fully extended position.

 	


 Interesting observation, Walt.   Because my CJ has uplocks,   I routinely placed the gear handle in the neutral after raising the gear for the first four years I owned the plane. For the last two years, however, I've just left it in the up position based on the recommendation of older and wiser CJ heads.   Hmmm.....     ...Blitz Fox

 

**************

Create a Home Theater Like the Pros. Watch the video on AOL Home.

      (http://home.aol.com/diy/home-improvement-eric-stromer?video=15&ncid=aolhom00030000000001)  [quote][b]

wlannon(at)persona.ca
Guest

Posted: Mon Mar 31, 2008 8:23 pm Post subject: gear collapse, no uplocks?

[quote] ---

adsavarese(at)hotmail.com
Guest

Posted: Tue Apr 01, 2008 1:46 am Post subject: gear collapse, no uplocks?

Is it possible the fracture was contributed to or accelerated  by the operation of the landing gear from the neutral position due to the fact  there is no back pressure in the actuator when placing the gear in the down  position from the neutral position?

 Dennis

  

 [quote]   ---

cjpilot710(at)aol.com
Guest

Posted: Tue Apr 01, 2008 4:29 am Post subject: gear collapse, no uplocks?

In a message dated 4/1/2008 12:24:39 A.M. Eastern Daylight Time,  wlannon(at)persona.ca writes:

  

 I've owned my 1969 CJ for some 14+ year now.  It never had up  locks.  It had 1088 hours on it and thousands of landings.  I don't if  the all the parts were original. Some 5 or 6 years ago I changed out bushings  but for the exception seals that I've changed 5 or 6 times, the rest  of the parts are original since I got it.  I've put over 1,500 hours  on my ship with out problems.  There is no such thing as the perfect gear  system, but the CJ's is damn close to it, as far as I'm concern.  Like  Walt, it'd be interesting to look at the fracture area.

  

 Jim "Pappy" Goolsby

  

  	  Quote: 	
		     Hmmm is right. Two years operation is not much.  I know    of two CJ's with no up-locks in service for the past 12 years or so with no    problem to date.  I'm sure there are many others.

   Would be interesting to view the fracture    surfaces, locate the origin and maybe get some idea of     progression.



   Walt

	


 

  



Create a Home Theater Like the Pros. Watch the video on AOL Home.

  [quote][b]

wlannon(at)persona.ca
Guest

Posted: Tue Apr 01, 2008 8:16 am Post subject: gear collapse, no uplocks?

Hey Pappy;

  

 I absolutely concur with all your comments except for the last " There is  no such thing as the perfect gear system, but the CJ is damn close to it  ---"

 Just to stir the pot I have to say --- Yes there is and no it is  not.

  

 Getting the gear down and locked depends on having some air to  blow on some goofy little air valves that may decide not to let go anyway.  If they do decide to let go you still need air to be sure they get to "down and  locked" If you run out of puff and still have some luck left the mains may get  to overcenter AND engage the ball lock, not a hope for the nose gear.

  

 On the other hand  the  perfect gear system does not need air,  hydraulics (though it has that for gear UP), electrons running around in  circles, motors, brushes etc. and all the other diabolical devices man has  invented to have 3 in the green.

  

 The perfect gear system is from North American Aviation 60 + years ago,  it's on the Harvard/T6.

 It is perfect for two reasons;

 1. Moving the handle to down MECHANICALLY releases the gear.

 2. GRAVITY puts it down AND locked. Hydraulic pressure catches up  later.

  

 Well maybe not exactly perfect. The early models had a tendency for the  uplocks to release on their own which was not good. Later corrected  with a spring bungee installation.

  

 Cheers;

 Walt

  

 [quote]   ---

ByronMFox(at)aol.com
Guest

Posted: Tue Apr 01, 2008 11:59 am Post subject: gear collapse, no uplocks?

In a message dated 3/31/08 9:24:18 PM, wlannon(at)persona.ca writes:

 

 

  	  Quote: 	
		  Would be interesting to view the fracture surfaces, locate the origin and maybe get some idea of  progression.

 Walt

 

 	


 My intention is to have the part analyzed by a metallurgical lab to establish if posiible what happened. Obviously, I'll share the results. ...Blitz

**************

Create a Home Theater Like the Pros. Watch the video on AOL Home.

      (http://home.aol.com/diy/home-improvement-eric-stromer?video=15&ncid=aolhom00030000000001)  [quote][b]

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