WINDMILLING - THE ANATOMY OF A TOWER CATASTROPHE

  By Robert F. Gonsett
  Copyright, Communications General Corporation, 1999

  This article describes the step-by-step events that led
to the tower collapse which claimed the life of Andy Figge,
a well respected rigger and Registered Professional Civil
Engineer.  The article was written at the request of several
Southern California broadcast engineers who had close ties
with Andy and wanted to understand the events that cost him
his life.  Hopefully, this understanding will help others
avoid similar tragedies.

  Most of the technical information in this article was
obtained from Ernie Jones, a Registered Professional Mechanical
and Civil Engineer.  Ernie visited the accident scene as a good
neighbor and pieced together the events from interviews and
physical evidence.  Additional data were provided by Ralph Young,
president of Empire Crane Service, and Hundley Batts, one of the
owners of the broadcast station where the tragedy occurred.
A small amount of non-technical information was gleaned from
a Huntsville Times article of February 12, 1999.

  Here, then, is how the tragedy appears to have unfolded:

  On February 10, 1999, Andy Figge was in the process of
installing a 250 foot guyed uniform cross-section tower at
Radio Station WEUP(AM), Huntsville, Alabama.  He had erected
the first 100' of tower and had attached three fiberglass guy
lines to the top of that tower.  The remaining 150 feet of
tower was laying on the ground in a continuous length where
it had been preassembled out of 10 foot sections.  The plan
was to use a crane to set the 150 footer on top of the
existing 100 footer, and that would be done in two stages.

  The first stage involved connecting a crane cable to the
side of the 150 footer so there was about 60 feet of tower
on one side of the connection point and 90 feet on the other.
The 150 foot section was successfully lifted upright and
temporarily set parallel against the existing 100 foot tower
section with the bottoms of both sections essentially at
ground level.  (The base of the 100 foot section was anchored
to its "point type" foundation while the bottom of the 150
footer was resting firmly on the ground.)

  Since the crane was not tall enough to lift the 150 footer
into place with the crane cable attached at the 90 foot mark,
Andy reconnected the cable to a point that was only 70 feet
above ground.  That left 80 feet of tower above the connection
point and caused an obviously unstable situation where the tower
could "windmill" and turn over.  Andy had anticipated that
state of affairs and had already attached weights to the
bottom of the 150 foot section to prevent overturning.

  In the second stage of the project, Andy was atop the 100
foot tower section and secured to the tower with his climbing
belt.  He was ready to bolt the bottom of the 150 footer to the
top of the 100 footer as soon as the crane completed the lift.

  A decision was made to raise the 150 foot section, just a
little, to make sure that the added weights were sufficient to
prevent windmilling.  Unfortunately, the weights were not
sufficient.  The bottom of the 150 foot tower section moved out
horizontally at an alarming rate (the crane cable attachment
point serving as the pivot) and the bottom of the 150 footer
headed directly for the studio/transmitter building.

  The crane operator reportedly tried to set the load down, but
could not do so in time.  Seconds later, the bottom of the 150'
tower section slammed into the underside of the roof eave.  That
brought the rotation of the 70 foot portion to a halt.  Of
course, the 80 foot portion wanted to keep going.

  This state of affairs put tremendous strain on what we
could now call the "top" tower leg of the 150 foot section.
A leg bolt broke (calculations suggest that its ultimate strength
was exceeded) so that the 150 foot section folded in two with the
80 foot end eventually coming to rest on one of the fiberglass
guy wires that held Andy's 100 foot tower section upright.  The
guy line reportedly held at first, then broke as the tower
metal slid down and sheared or sliced the line.

  Andy was never able to unbuckle himself and rode the 100
footer down as it toppled onto the roof of the studio/transmitter
building.  He was reportedly killed instantly.  There were no
other injuries or fatalities associated with the accident.

  Ralph Young, president of Empire Crane Service, commented
that a safety meeting had been held on Monday prior to the job,
and that the crane operator had attended.  Andy presented himself
professionally and there was no question in anyone's mind
that he had carefully thought over each step of the job,
and that he was well qualified to complete it.

  Through the course of this project, the staff and management
of Empire Crane and WEUP had grown to respect and care about Andy
as an individual.  They were severely shaken by the tragedy.
Empire Crane had reportedly been in business 34 years without
a major injury accident.

  By clearly understanding the step-by-step events that led to
the fatality, it is hoped that similar accidents will be prevented.

  ______

  This article is published as part of the CGC Communicator
newsletter and may be reprinted or republished - free of charge -
provided the story is unaltered and printed in full, including
this section.

  Stories that pertain to this incident begin with CGC
Newsletter #312.