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
