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Pawnee air-oil bear strut pressure



 
 
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  #1  
Old March 6th 18, 12:38 AM posted to rec.aviation.soaring
Larry Ruggiero
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Default Pawnee air-oil bear strut pressure

Yes I know they’re problematic. Just returned our PA 25-235 from its annual, where one of ours was rebuilt (locked solid) and both serviced. Like I assume many of yours are, our Pawnee has no hopper and will never see gross weight again. So should the air side of the struts still be 575psi per the book? Noticed neither strut budged a bit during taxi and it landed pretty stiff. Plus the gear is now spread wide compared to “normal.” Called our IA and got a virtual shoulder shrug. Thoughts?

Larry Ruggiero, pilot/A&P
Carolina Soaring
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  #2  
Old March 6th 18, 02:37 AM posted to rec.aviation.soaring
Charles Longley
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Default Pawnee air-oil bear strut pressure

OK I give up. What part are you talking about?

Charlie
Pilot/ A&P
  #3  
Old March 6th 18, 02:41 AM posted to rec.aviation.soaring
Larry Ruggiero
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Default Pawnee air-oil bear strut pressure

Landing gear struts instead of bungees.
  #4  
Old March 6th 18, 02:57 AM posted to rec.aviation.soaring
Charles Longley
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Default Pawnee air-oil bear strut pressure

Ahh who makes them? One of our Pawnees has bungees the other one has Cessna spring gear.
  #5  
Old March 6th 18, 03:04 AM posted to rec.aviation.soaring
Charles Longley
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Default Pawnee air-oil bear strut pressure

Never mind I found them as an option from Piper. I have no advice other then follow the POH for troubleshooting. Maybe set the pressure towards the lower end of the spectrum.
  #6  
Old March 6th 18, 03:54 PM posted to rec.aviation.soaring
Roy B.
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Default Pawnee air-oil bear strut pressure

On the subject of Pawnee landing gear - be very careful of the Hutch conversion 2 piece slab type gear that is fixed with 3 vertical bolts. If the centermost bolt fails (as it can from vibration over the years) the gear collapses, the prop strikes the ground, and you have a totaled plane from a situation that really can't be detected/inspected before the failure. We lost a towplane that way in a very light landing on grass when the bolt snapped.
The bungee system has some redundancy and the Cessna one piece gear slab is good - but the 2 piece Hutch gear is a problem.
ROY
  #7  
Old March 6th 18, 06:46 PM posted to rec.aviation.soaring
Dan Daly[_2_]
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Default Pawnee air-oil bear strut pressure

On Tuesday, March 6, 2018 at 10:55:02 AM UTC-5, Roy B. wrote:
On the subject of Pawnee landing gear - be very careful of the Hutch conversion 2 piece slab type gear that is fixed with 3 vertical bolts. If the centermost bolt fails (as it can from vibration over the years) the gear collapses, the prop strikes the ground, and you have a totaled plane from a situation that really can't be detected/inspected before the failure. We lost a towplane that way in a very light landing on grass when the bolt snapped.
The bungee system has some redundancy and the Cessna one piece gear slab is good - but the 2 piece Hutch gear is a problem.
ROY


The PA-25 SB 25/32/04 dated 01/03/2008 describes a Main Landing Gear Shock Absorption System modification adding a cable to restrict lateral movement of the landing gear leg should a piece of the Hydrasorb shock absorber crack and fail (which they do). We had a Pawnee mod'd (bungee gear system) and had the failure of one support on landing. The down wingtip didn't touch, and neither did the prop. Laviasa had a kit (KIT LA-K-005) with support fittings, a security cable, and longer bolts. Money well spent. I have a soft copy of the SB (2 pages text, 3 pages drawings) if anyone wants one. Also pics of the cable having done its job, a closeup of the installation, and a pic of an unluckier Pawnee without the mod kit.

For light reading, I attach a link to a Canadian Civil Aviation Safety Alert showing the fatigue cracking of the part. https://www.tc.gc.ca/eng/civilaviati...11-02-1344.htm

Dan
  #8  
Old March 6th 18, 07:01 PM posted to rec.aviation.soaring
Larry Ruggiero
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Default Pawnee air-oil gear strut pressure

Thanks Dan, I will look into this mod. Our gear’s pivot bolts have been replaced in the past few years, but I totally agree redundancy is good.. At least one operator has shared with me a story of her experience with that bolt failing— scary. Right now I need to get its gear unsplayed and softened back up. The POH was written to accommodate a full-up gross weight ag plane, which ours will never be again. Unless greater wisdom appears here, I will start by reducing air pressure in modest increments and see what happens.

Larry
  #9  
Old March 6th 18, 07:08 PM posted to rec.aviation.soaring
Waveguru
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Default Pawnee air-oil gear strut pressure

If the gear is splayed, it means you need MORE pressure, not less.

Boggs
  #10  
Old March 6th 18, 07:20 PM posted to rec.aviation.soaring
Larry Ruggiero
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Default Pawnee air-oil gear strut pressure

Well having read through the above data, it's not applicable. Ours doesn't have the hydrasorb gear that also incorporates bungees. Ours is the 2 massive air-oil strut units Piper had on at least one series of Pawnees. I'll try posting a photo.

Larry

 




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