Model Forum / General / Models / November 2007

Suncorite!  I *knew* it had a name, but despite tacking my brains I just
couldn't remember it.  Thanks Ian.

I kept coming up with Flexane and Belzona, which were two other types of
protective coating in use at the time.

Certainly we never issued any Sidewinders suitable for underwing carriage to
Jaguar units.  The ones we did issue were specifically banned from underwing
carriage, but that was purely for logistical reasons.

The Sidewinder is a very cheap missile to manufacture, partially because
there is no electronic stabilisation system. All the electronics deal with
guidance. Stabilisation is purely mechanical. Have a look at the outer
trailing edge of a Sidewinder wing (the wings are at the back, fins are at
the front). You will see that it has a rectangular hinged natural metal
section with an odd bump on top. These are called "rollerons" and they
affect the flight of the missile in a similar manner to ailerons.  Each
rolleron has a metal wheel partially buried inside it, with one part of the
wheel exposed to the airstream. As the edge of the wheel is serrated, the
wheel spins and acts like a gyroscope. Like all gyroscopes it attempts to
resist sideways movement, so forcing the rolleron in the opposite direction.
The rollerons therefore tend to damp any spinning motion of the missile.

A problem occurs when the missile is in captive flight (ie mounted on an
aircraft's missile rail). If the rollerons are allowed to act naturally,
they will even attempt to control the flight of the parent aircraft!  Their
effect is so great that the pilot can receive warnings from his
flight-control systems. To prevent this from happening, the rollerons have a
seismic lock. The rolleron wheel still spins in captive flight, but the
rolleron itself is not free to move on its hinge. When the missile is
launched, the extreme acceleration overcomes the seismic lock allowing the
rollerons to fulfil their purpose.

The original seismic lock was shaped like a triangle. It fitted into a tube
in the wing, underneath the rolleron cutout and projected upwards, locking
into a slot on the rolleron. When the lock was released, it slid clear of
the rolleron in the manner of a radio aerial being deployed. Wings fitted
with this type of lock were known as Mod1. The problem with the Mod1 wings
was that the rolleron wasn't held completely rigid and there was a certain
amount of chatter in captive flight.  This caused the trailing edge of the
rolleron and the seismic lock to wear at an unacceptable rate.  It should be
noted that the original design requirement of Sidewinder wings and fins was
that they be used once and then scrapped. The RAF could not afford this
policy (it caused all sorts of other problems related to the ablative
coating of the wings).

Therefore, an improved seismic lock was fitted. This still used the
triangular locking plate, but it was combined with a longitudinal plate that
held the rolleron firmly in position. Instead of sliding out on an
extendable rod, it pivoted backwards and downwards. Wings fitted with this
type of lock are referred to as Mod2. There were a number of minor
refinements (Mod2A, Mod2B etc).  A Mod1 Wing could be converted to a Mod2
wing, although the process was quite labour intensive.

The Mod2 wing solved the wear problems until the introduction of the Jaguar
overwing pylons. When missiles are carried underwing they are held in a
relatively benign environment. On the other hand those on overwing pylons
are in a much more boisterous airstream. It was found that the airstream
would tear the Mod2 locks out of the wings during captive flight, so
releasing the rollerons and giving the pilot a bit of a shock when his
aircraft refused to respond in the manner that he expected!  Trials showed
that the Mod1 locks were much more robust than the Mod2 locks. Rather than
introducing a Mod3 lock to solve the problem, the RAF settled for de-modding
a number of wings back to Mod1 standard.

These wings were only ever issued to Jaguar units. They were specifically
banned from underwing fitment, but there was no physical reason for that. We
only had a very small revenant stock of Mod1 wings, which were subject to
the original chatter problem and so wore out quicker that the main stock of
Mod2 wings. We had to carefully husband these wings as under no
circumstances were we allowed to de-mod any more Mod2s. It was a complete
pain in the arse dealing with them. I bet the missile boys finally breathed
a sigh of relief with the Jaguar was withdrawn.

Mind you, having said that, I have no doubt that something else will arise
that requires a non-standard fit. The RAF is very good at that sort of
thing.  Twenty years ago they introduced an electronic bomb fuze that was
supposed to reduce the number of different bomb/fuze build standards to from
three to one - known as an All Up Round. Sadly, there was never an armament
steering committee available to disseminate information about AURs and so by
the time I left the RAF, there are now a dozen different build standards! No
doubt with the introduction of Typhoon, and yet another hardpoint locking
mechanism, that has risen to eighteen   It's a long, sad story.

Long range ferry flight?

Pat

And it's on telly RIGHT NOW - BBC2

Wulf

Sounds familiar.  I think I heard the same thing at Harrisburg when the
Tornado F.3 put on a display.  All I know was he was really moving and
we got a bit of a 'wumpf' when he passed.  Glad it wasn't any harder as
the hangars up there all have thousands of panes of glass windows in the
doors.

Bill Banaszak, MFE Sr.

You stock up model kits like a survivalist stocks up MRE's. :-D

Pat

Hey Enzo - try these regarding O/B AIM-9

http://www.airliners.net/open.file/0782244/M/

http://www.airliners.net/open.file/0952981/M/ ( OK - so it's an aqui -
but the wiring must be there )

When were you on Jags / in the dump BTW? ( me 85 to 06 ! )

Ian