Service Bulletins


Subject:    Service Bulletins
From:    Richard Goode (richard.goode@russianaeros.com)
Date:    Mon Sep 01 - 9:26 AM
I have been asked to give more detail about the specific problems that 
led to Yak-52 Service Bulletins.   However it is not so simple.  

As I have said before there are thirty-one of these covering what, I 
believe, Yakovlev would term "potentially serious airframe defects".   
Of course I have a list of these thirty-one; I have seen examples of 
each physically on an aeroplane, but have no detailed background as to 
why each of the 31 was introduced.   However I have sat through several 
sessions at Yakovlev in Moscow discussing Yak airframe issues, 
particularly for 50 and 52 and I HAVE seen a wide range of technical 
reports and associated photographs showing REAL airframe failures.   For 
the 50, these were serious and led to four fatal accidents and there 
would have been a number more had it not been for very vigilant 
technicians, and an extremely vigorous inspection regime.   

For 52s, I have seen evidence (at the meetings above) of failure in a 
number of areas, including wing mounting brackets; aileron mounting 
brackets; detachment of elevator balance weights etc.   Although I 
cannot provide a detailed explanation and background for each of the 
thirty-one SBs (and I cannot believe that anyone would expect me to) I 
can assure any 52 Owner that each was a real issue; was taken very 
seriously, and ended with an appropriate Service Bulletin.   

It surprises me that there seems to be a significant body of 52 Owners 
who seem to regard these SBs as being discretionary.  I assume that if 
Piper or Pitts issue an Airworthiness Directive, then the Owner will 
ensure that their aeroplane complies to that AD.   What I find puzzling 
is that the same approach seems not to apply with Russian aircraft. 

Clearly there is a difference in that the Russian aeroplanes are not 
Normal Category and Certificated aircraft in the USA.  Nevertheless, 
surely one assumes that the Service Bulletins are just as vital for 
aircraft safety. 

There also seems to me to be a suggestion that Yakovlev promulgated SBs 
for reasons other then those purely related to safety.   I know Russia 
better than most, and few things surprise me about Russia but, from a 
combination of my own experience and simple logic, I can see no 
foundation for such thinking.   The key points are surely:

  a.. Yakovlev is a Design Bureau, and has no role in the manufacture or 
subsequent modification of its aircraft.  
  b.. So Yak design aircraft, and other, and completely separate, 
organisations manufacture them, and then build any modification kits etc 
that might be required. 
  c.. So Yak-18T was (and is) built in Smolensk; 52 at Aerostar in 
Romania; 50 and 55 at the State Factory at Arsenyev in the extreme 
Russian Far East. 
  d.. In addition the vast majority of these Service Bulletins were 
issued in Soviet days, when Yakovlev, and indeed the whole Soviet 
aircraft industry was well-funded.  All 18T Bulletins were finished by 
1984; all Yak-50 Bulletins by 1985, and the last significant 52 Bulletin 
(SB number 107) in 1990. 
  e.. When these SBs were promulgated by Yakovlev, they only did the 
design and practical work for one prototype.  At that stage the 
manufacturing unit was then required to make whatever modification kits 
were required, and then installed by appropriate technicians. 
  f.. None of this benefited Yakovlev, and I suspect, not good news for 
them, since it clearly would not reflect well on their capabilities as 
aircraft designers if their designs needed constant modifications.   So 
I think  we can be sure that Yakovlev only issued SBs when they regarded 
them absolutely necessary!  For further information please see the 
attached links below.
http://www.russianaeros.com/Yak52service.htm

http://www.russianaeros.com/Yak-55%20Service%20Bulletins.htm

http://www.russianaeros.com/Yak-50%20Service%20Bulletins%20after%20crashe
s.htm

Richard Goode Aerobatics 
Rhodds Farm 
Lyonshall
Herefordshire
HR5 3LW 
United Kingdom

Tel: +44 (0) 1544 340 120
Fax: +44 (0) 1544 340 129 
www.russianaeros.com




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