CP File Investigators attach pieces of wreckage from Swissair Flight 111 to a reconstruction frame at CFB Shearwater in 1998.

By Alison Auld / The Canadian Press

Aviation experts are hoping new safety recommendations related to the crash of Swissair Flight 111 will impose limits on volatile wiring used in the plane, but sources don't expect airlines will be forced to pull the material from their fleets.

A source, who asked not to be named, told The Canadian Press that the five recommendations expected to be released today by the Transportation Safety Board are unlikely to deal directly with the wiring issue.

Wiring has been a central part of the investigation into the 1998 crash that killed 229 people when the MD-11 went down off the coast of Nova Scotia.

Ed Block, an aviation wiring expert, said it's time regulators took steps to eliminate what he considers a safety hazard.

"I would look for the murder weapon and the murder weapon in a number of instances has been the wiring on these aircraft and I would hope the TSB will move in that direction," said Block, a member of an Federal Aviation Administration committee and the International Aviation Safety Association.

Such an overhaul would cost hundreds of millions for airlines and manufacturers, he said.

Investigators have focused on a controversial wire covering known as aromatic polymide tape, or Kapton, that has been found to char and is susceptible to damage.

The TSB has found evidence a fire developed in the ceiling near Flight 111's cockpit, but haven't discovered the cause. The agency has also determined that wire covered in Kapton was charred and that there were signs of arcing, a phenomenon similar to a short circuit.

Sparks can char the Kapton insulation, creating carbon buildup. The carbon eventually acts as a conductor and the sparking begins tracking along wires. The problem can ultimately lead to an explosive fire that burns at 5,000 C, incinerating everything in its path.

Wiring experts have been pressing the TSB and the Federal Aviation Administration in the United States to force the removal of Kapton from aircraft, claiming the material poses a major threat to airline safety.

A spokesman for the TSB wouldn't reveal what the recommendations will address specifically, but said they will likely have broad implications for the airline sector.

"These recommendations are going to be very important for the entire industry," Jim Harris said last week.

"They deal with a systemic problem that we uncovered during the investigation."

Harris said planes will not be grounded as a result of the safety recommendations.

Observers have speculated that the five points will include warnings about fire detection and suppression, pilot practices and tests to check existing wiring.

Some say the TSB should take bold steps in dealing with the suspected problem of wiring on planes after senior American officials openly stated wiring was a national concern.

"The White House has admitted that, 'Folks we have a problem, we admit we don't know enough about it,' " said Mike Murphy of the Air Passenger Safety Group in Ottawa.

"I would hope that that would embolden the TSB to put this issue on the table. This was a major accident and, frankly, I expect some major changes."

The recommendations will be given to aviation regulators in Canada, the U.S. and Europe, who will then decide if they want to accept them as regulations governing the industry.

The TSB has issued several recommendations and advisories as a result of the investigation, one of the longest and most expensive in Canadian aviation history.

One interim safety recommendation dealt with safety deficiencies in metallized insulation blankets on the plane that have been suspected of spreading fire.

The FAA responded by issuing a notice that would force the removal of the blankets from all U.S.-registered MD-11 aircraft within four years.

The TSB has also issued safety notices dealing with an emergency power supply for flight recorders, an increase in recording capacity of cockpit voice recorders and the potential source of heat from flight crew reading lights.

The TSB will also announce today that the reconstruction phase of the investigation is over. Dozens of investigators have been poring over two million pieces of the plane's wreckage in a hangar in Shearwater. That material will remain there, but the investigation will move to the TSB lab in Ottawa.