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Yak-52 elevator failure

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richard.goode(at)russiana
Guest

Posted: Thu Mar 24, 2011 9:13 am Post subject: Yak-52 elevator failure

At the end of last year, the elevator actuators segment on a Russian Yak-52 failed, and the resulting crash was fatal.    

   

The “sector” involved is the plate between the two elevator end plates, underneath the vertical stabiliser.  The elevator cables connect to the top and bottom of this plate, and clearly if the plate fails all elevator control is lost.    

   

The current design is made from high tensile aluminium , and it is expected that there will be a formal Service Bulletin requiring a change to steel.  In the meantime, all 52 owners are strongly recommended to remove this plate and have it crack-tested.    

   

If you follow this link,  http://www.russianaeros.com/Yak-52%20Elevator%20Failure.htm you can see a photograph of the failed item from the crashed aircraft, as well as a photograph showing the plate in place on a 52.     

   

   

Richard Goode Aerobatics  

Rhodds Farm  

Lyonshall  

Herefordshire  

HR5 3LW  

United Kingdom  

   

Tel:  +44 (0) 1544 340120  

Fax: +44 (0) 1544 340129  

www.russianaeros.com  

   

       [quote][b]

tigeryak18t

Joined: 26 Sep 2009
Posts: 233
Location: PARIS FRANCE

Posted: Thu Mar 24, 2011 2:16 pm Post subject: Yak-52 elevator failure

Rich

Will that concern also The 18T???

Will you provide the steel plate for the 52?

Thanks and best regards



Didier Blouzard+33(0)6 2424 3672

Le 24 mars 2011 Ã  18:10, "Richard Goode" <richard.goode(at)russianaeros.com (richard.goode(at)russianaeros.com)> a Ã©crit :



[quote]    

At the end of last year, the elevator actuators segment on a Russian Yak-52 failed, and the resulting crash was fatal.    

   

The â€œsectorâ€ involved is the plate between the two elevator end plates, underneath the vertical stabiliser.  The elevator cables connect to the top and bottom of this plate, and clearly if the plate fails all elevator control is lost.    

   

The current design is made from high tensile aluminium , and it is expected that there will be a formal Service Bulletin requiring a change to steel.  In the meantime, all 52 owners are strongly recommended to remove this plate and have it crack-tested.    

   

If you follow this link,  http://www.russianaeros.com/Yak-52%20Elevator%20Failure.htm you can see a photograph of the failed item from the crashed aircraft, as well as a photograph showing the plate in place on a 52.     

   

   

Richard Goode Aerobatics  

Rhodds Farm  

Lyonshall  

Herefordshire  

HR5 3LW  

United Kingdom  

   

Tel:  +44 (0) 1544 340120  

Fax: +44 (0) 1544 340129  

www.russianaeros.com  

   

        	  Quote: 	
		  



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ef="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/Navigator?Yak-List

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ums.matronics.com">http://forums.matronics.com

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[b]

_________________
Didier Tiger YAK18T
Member of Commemorative Air Force
French Wing

richard.goode(at)russiana
Guest

Posted: Fri Mar 25, 2011 9:45 am Post subject: Yak-52 elevator failure

To answer the queries of several people who have written to me directly:  

   

<![if !supportLists]>Ø  <![endif]>I have passed on all that I know today – but it seemed to me that this is a critical issue that any sensible owner would want to check on their own aircraft.   

<![if !supportLists]>Ø  <![endif]>I understand from Yakovlev themselves that they will issue a formal Service Bulletin (AD).    

<![if !supportLists]>Ø  <![endif]>Again I understand that this will be made out of steel rather than aluminium alloy.   

<![if !supportLists]>Ø  <![endif]>However I do not know any more details of when/where the plate might be made etc.    

<![if !supportLists]>Ø  <![endif]>I have no idea if there would be a potential similar problem with the 18T/50 etc, which have a similar design.   

   

Richard Goode Aerobatics  

Rhodds Farm  

Lyonshall  

Herefordshire  

HR5 3LW  

United Kingdom  

   

Tel:  +44 (0) 1544 340120  

Fax: +44 (0) 1544 340129  

www.russianaeros.com  

   

       [quote][b]

pilko2(at)btinternet.com
Guest

Posted: Sat Mar 26, 2011 4:35 am Post subject: Yak-52 elevator failure

Trawling the website of Yak UK reveals this to be a well known gotcha.  

   

 http://www.yakuk.com/2000-004.doc    

   

   

   MPD: 2000-004  

   

Subject: Crack in elevator control system pulley.  

   

Applicability: Yakovlev/ Aerostar or a SA Y B AK 52 aircraft.  

   

Reason: A 19 mm crack has been discovered in the elevator actuation part number 5251 or 00-80-3 (referred to as “lever” in the Romanian parts catalogue). The failure of this component could result in loss of the elevator control.  

   

Compliance: Within 50 hours from the effective date of this MPD, inspect elevator actuation pulley parts number 525100-80-34 cracking on its periphery below the attachment for the balance weight bracket, at the point where the section reduces from a 10 mm to 7 mm. Inspect using dye penetrant techniques. if the component is cracked, replace it before Further Flight. Repeat this inspection annually at renewal of the permit to fly.  

   

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wlannon(at)persona.ca
Guest

Posted: Sat Mar 26, 2011 3:03 pm Post subject: Yak-52 elevator failure

Interesting!

  

 How much weight is attached to this part?  And  for what purpose?

  

 Walt 

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William Halverson

Joined: 27 Feb 2010
Posts: 88

Posted: Sat Mar 26, 2011 3:27 pm Post subject: Yak-52 elevator failure

Well, the part is cracking on the upper side ... would it be due to aggressive pull back forces on the stick?

+--

wlannon(at)persona.ca
Guest

Posted: Sat Mar 26, 2011 7:20 pm Post subject: Yak-52 elevator failure

Possibly.  The crack is originating at the section change where loads would 

tend to concentrate but it may also be subject to bending loads from the 

balance weight attached to the upper, heavier, section.

Possibly rudder induced transverse loading?

I don't understand the use of a balance weight in this location.

Walt

---

wlannon(at)persona.ca
Guest

Posted: Sun Mar 27, 2011 2:14 pm Post subject: Yak-52 elevator failure

Hi Cliff;

  

 Thanks for your reply.  There seems to be a  bit of confusion re this part.

 It is not a control balance arm which would  typically extend well forward of the control surface hinge line.

  

 This is the elevator control cable drive sector  (bellcrank). 

 It appears to have  weight mounted on it  directly above the hinge centre line.

 That would have absolutely zero effect on elevator  balance if the weight is mounted where the attachment holes are  located.

 But, I am beginning to get the  picture!!!!!!!   Is this the mounting location for the balance  ARM?

  

 If so that takes my concern to a whole new  level.  That would be the absolutely dumbest place you could possibly  imagine to attach a balance arm.

  

 Not only does the sector have to handle the balance  weight the effect is severely magnified by the length of the arm.

 The cause of this cracking I believe is a direct  result of that installation.

 Any asymmetrical rudder loads will induce  horizontal loading of the ELEVATOR balance weight which will in turn  

 induce a twisting moment in the elevator sector.  

 Over (who knows how) many cycles this will result  in a fatigue failure at the most likely focal point. Barring a severe  nick or other mechanical damage that point is the section change.

  

 Now I begin to understand why they are  suggesting a STEEL replacement.  

  

 Walt

  

 PS:

 --

talew(at)bellsouth.net
Guest

Posted: Sun Mar 27, 2011 5:46 pm Post subject: Yak-52 elevator failure

Hi Walt ,

 That is a very incisive analysis of why this part might fail . I think you may have 

 shed some light on this problem .

 Terry



 

   From: Walter Lannon <wlannon(at)persona.ca>

To: yak-list(at)matronics.com

Sent: Sun, March 27, 2011 5:47:35 PM

Subject: Re: Yak-52 elevator failure



   Hi Cliff;

  

 Thanks for your reply.  There seems to be a bit of confusion re this part.

 It is not a control balance arm which would typically extend well forward of the control surface hinge line.

  

 This is the elevator control cable drive sector (bellcrank). 

 It appears to have  weight mounted on it directly above the hinge centre line.

 That would have absolutely zero effect on elevator balance if the weight is mounted where the attachment holes are located.

 But, I am beginning to get the picture!!!!!!!   Is this the mounting location for the balance ARM?

  

 If so that takes my concern to a whole new level.  That would be the absolutely dumbest place you could possibly imagine to attach a balance arm.

  

 Not only does the sector have to handle the balance weight the effect is severely magnified by the length of the arm.

 The cause of this cracking I believe is a direct result of that installation.

 Any asymmetrical rudder loads will induce horizontal loading of the ELEVATOR balance weight which will in turn 

 induce a twisting moment in the elevator sector. 

 Over (who knows how) many cycles this will result in a fatigue failure at the most likely focal point. Barring a severe nick or other mechanical damage that point is the section change.

  

 Now I begin to understand why they are suggesting a STEEL replacement.  

  

 Walt

  

 PS:

 --

dsavarese0812(at)bellsout
Guest

Posted: Sun Mar 27, 2011 6:50 pm Post subject: Yak-52 elevator failure

Hi Walt,

Yes, the 4 mounting holes are for the mounting arm as you suggest which

extends forward and has a significant weight on the end. I will take

some photos of the counterweight arm as mounted on the bellcrank

tomorrow and post them on the list.

Dennis



On 3/27/2011 8:17 PM, T A LEWIS wrote:

[quote] Hi Walt ,

 That is a very incisive analysis of why this part might fail . I think

 you may have

 shed some light on this problem .

 Terry



 ------------------------------------------------------------------------

 *From:* Walter Lannon <wlannon(at)persona.ca>

 *To:* yak-list(at)matronics.com

 *Sent:* Sun, March 27, 2011 5:47:35 PM

 *Subject:* Re: Yak-52 elevator failure



 Hi Cliff;

 Thanks for your reply. There seems to be a bit of confusion re this part.

 It is not a control balance arm which would typically extend well

 forward of the control surface hinge line.

 This is the elevator control cable drive sector (bellcrank).

 It appears to have weight mounted on it directly above the hinge

 centre line.

 That would have absolutely zero effect on elevator balance if the

 weight is mounted where the attachment holes are located.

 But, I am beginning to get the picture!!!!!!! Is this the mounting

 location for the balance ARM?

 If so that takes my concern to a whole new level. That would be the

 absolutely dumbest place you could possibly imagine to attach a

 balance arm.

 Not only does the sector have to handle the balance weight the effect

 is severely magnified by the length of the arm.

 The cause of this cracking I believe is a direct result of that

 installation.

 Any asymmetrical rudder loads will induce horizontal loading of the

 ELEVATOR balance weight which will in turn

 induce a twisting moment in the elevator sector.

 Over (who knows how) many cycles this will result in a fatigue failure

 at the most likely focal point. Barring a severe nick or other

 mechanical damage that point is the section change.

 Now I begin to understand why they are suggesting a STEEL replacement.

 Walt

 PS:

 --

mark.bitterlich(at)navy.m
Guest

Posted: Mon Mar 28, 2011 8:23 am Post subject: Yak-52 elevator failure

Cliff, what you are saying here makes perfect sense.  Thanks for writing it.  



Inspecting the part makes sense, but in my mind it is MUCH more important to determine why it cracked in the first place.  



Mark Bitterlich

 



--

dsavarese0812(at)bellsout
Guest

Posted: Mon Mar 28, 2011 9:36 am Post subject: Yak-52 elevator failure

Since the cause of the crack in the bellcrank has not been determined 

(or published), as Cliff points out, it is also very important to make 

certain your airplane is configured/rigged properly.  ie: Elevator 

travel is set to specs; rudder travel is set to specs; aileron travel is 

set to specs; cable tensions are set to specs and the elevator counter 

weight bolts and nuts are 100% tight.



Last but not least as Cliff points out, the elevator bellcrank bearing 

CAN and WILL wear.  It is a 6x19x6 mm self aligning bearing and they are 

used in several places on the airplane.  The ones used on the control 

surfaces are open face bearings (not sealed) and are prone to collecting 

dirt and grit which causes premature wear of the bearing.  The elevator 

bellcrank bearing is one of these bearings that can easily be degraded 

because of dirt and grit migrating to the inside of the bearing. 

Another one of these self aligning bearings is the inboard aileron 

bearing.  This one is the worst of all for collecting dirt because of 

its proximity to the main wheel tires which flick the dirt upward during 

ground operations.



Dennis



On 3/28/2011 10:47 AM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 

64E wrote:

[quote] 



 Cliff, what you are saying here makes perfect sense.  Thanks for writing it.



 Inspecting the part makes sense, but in my mind it is MUCH more important to determine why it cracked in the first place.



 Mark Bitterlich

 --

wlannon(at)persona.ca
Guest

Posted: Mon Mar 28, 2011 1:52 pm Post subject: Yak-52 elevator failure

Hi Cliff;

  

 The self-aligning bearing is there to compensate  for any minor mis-alignment in the assembly of the sector to the rear spar  attach fitting with the left & right elevators attached

 to the sector.

  

 It will have no effect whatever on the any  twisting/bending moments induced in the upper (thicker) part of the  sector.  Those loads are transmitted to the thinner (7mm) section which is  firmly bolted to both elevators through the attachment plates.

 These plates are substantial and very effectively  increase the bending resistance of the sector in the area just below the section  change.  This of course further defines the focal point for cracking at the  section change by eliminating any flexure below that point.

  

 For the universal bearing to have any effect the  entire elevator assembly would have to translate laterally.

  

 Sorry. I think it is a very poor design and  probably dictated by a lack of space in that area.

  

 The CJ is quite different.  The balance arm is  attached to the primary structure of the elevator assy.

 I would expect the CJ system is a direct copy of  the earlier Russian systems. 

 Jump in Doug -- how is the Yak 18  done?

 Anyone know the Yak 50,  Yak18A  systems?

  

 Cheers;

 Walt

  

  

 [quote]   ---

dsavarese0812(at)bellsout
Guest

Posted: Mon Mar 28, 2011 2:31 pm Post subject: Yak-52 elevator failure

Yak 50 bellcrank and counterweight is the same design as the 52.

Dennis



On 3/28/2011 4:18 PM, Walter Lannon wrote:

[quote] Hi Cliff;

 The self-aligning bearing is there to compensate for any minor

 mis-alignment in the assembly of the sector to the rear spar attach

 fitting with the left & right elevators attached

 to the sector.

 It will have no effect whatever on the any twisting/bending moments

 induced in the upper (thicker) part of the sector. Those loads are

 transmitted to the thinner (7mm) section which is firmly bolted to both

 elevators through the attachment plates.

 These plates are substantial and very effectively increase the bending

 resistance of the sector in the area just below the section change. This

 of course further defines the focal point for cracking at the section

 change by eliminating any flexure below that point.

 For the universal bearing to have any effect the entire elevator

 assembly would have to translate laterally.

 Sorry. I think it is a very poor design and probably dictated by a lack

 of space in that area.

 The CJ is quite different. The balance arm is attached to the primary

 structure of the elevator assy.

 I would expect the CJ system is a direct copy of the earlier Russian

 systems.

 Jump in Doug -- how is the Yak 18 done?

 Anyone know the Yak 50, Yak18A systems?

 Cheers;

 Walt



     ---

dougsappllc(at)gmail.com
Guest

Posted: Mon Mar 28, 2011 3:16 pm Post subject: Yak-52 elevator failure

Walt,The elevator on the 18 attaches just like the CJ6.  Don't know about the 50, and have never seen a 52 elevator, so I'm afraid I can't be of much help here.

Doug



 On Mon, Mar 28, 2011 at 2:18 PM, Walter Lannon <wlannon(at)persona.ca (wlannon(at)persona.ca)> wrote:

[quote]        Hi Cliff;

  

 The self-aligning bearing is there to compensate  for any minor mis-alignment in the assembly of the sector to the rear spar  attach fitting with the left & right elevators attached

 to the sector.

  

 It will have no effect whatever on the any  twisting/bending moments induced in the upper (thicker) part of the  sector.  Those loads are transmitted to the thinner (7mm) section which is  firmly bolted to both elevators through the attachment plates.

 These plates are substantial and very effectively  increase the bending resistance of the sector in the area just below the section  change.  This of course further defines the focal point for cracking at the  section change by eliminating any flexure below that point.

  

 For the universal bearing to have any effect the  entire elevator assembly would have to translate laterally.

  

 Sorry. I think it is a very poor design and  probably dictated by a lack of space in that area.

  

 The CJ is quite different.  The balance arm is  attached to the primary structure of the elevator assy.

 I would expect the CJ system is a direct copy of  the earlier Russian systems. 

 Jump in Doug -- how is the Yak 18  done?

 Anyone know the Yak 50,  Yak18A  systems?

  

 Cheers;

 Walt

  

  

 [quote]   ---

alikatz(at)mbay.net
Guest

Posted: Thu Mar 31, 2011 9:47 am Post subject: Yak-52 elevator failure

Watching the Weather Channel, Florida is getting pounded, noticed a CJ  

sitting off the Field backed into a small ditch of water in Lakeland,  

praying for everyones safety...



Direct TV CH:202

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