That's the word from defence sources with intimate knowledge of the troubled program.
The federal government has refused to accept four test helicopters, currently parked at the Canadian Forces facility in Shearwater, N.S., on the basis they are "non-compliant" — and most of the public explanation has related to software issues.
But the sources say there's concern that delicate flight systems, including a computer that runs the engines, are not sufficiently shielded against powerful electromagnetic waves, such as those produced by military-grade radar on frigates.
The interference has the potential of blanking out the digital instruments and possibly shutting down the engines.
The directorate of air worthiness at National Defence issued a restricted flight certificate in July and imposed restrictions on the helicopter's operations specifically because of so-called E-3 concerns — electromagnetic compatibility, electromagnetic vulnerability and electromagnetic interference.
"Each of them are potential show-stoppers," said one source, who asked for anonymity.
"The vulnerability depends on the frequency and the strength of the signal. You have the potential of losing your instruments and not knowing where you are, and having to take visual cues from outside your aircraft to get down safely."
The Cyclone, meant to replace 50-year-old CH-124 Sea Kings, was cleared to fly within sight of the ground only during daylight hours as part of a long-delayed flight test program that was to have been carried out last month in Nova Scotia.
It also cannot fly over water because of separate, unresolved concerns about the flotation system.
The Conservative government signalled last week it is examining "other" options to the Sikorsky-built helicopter, which is five years behind schedule and overbudget.
Debate within the military test community has revolved around whether the electromagnetic issue is a fatal blow to the program, since the Cyclone's design was based on a less-rugged civilian variant.
"The aircraft was not designed from the ground up with this kind of shielding in mind," said the source. "Military aircraft, the skin of military aircraft, are sometimes embedded with a fine copper screen or mesh to prevent the intrusion of electromagnetic interference."
There are potential fixes, according to several defence sources.
One solution could involve retroactively installing screens around sensitive electronics, but that could add as much as 136 kilograms to the weight of the helicopter. That worries engineers who have long been concerned whether the Cyclone's engine is powerful enough to comfortably lift its existing weight.
Both Sikorsky and National Defence were asked to comment on the technical concerns, and given specific detailed questions.
"Our contractual agreement with the Canadian government precludes us from publicly discussing technical aspects of the program," Sikorsky spokesman Paul Jackson responded in an email. "Since your questions pertain to such aspects, I will have to decline to comment on them."
Public Works, which manages the contract on behalf of Defence, ducked the issue.
"The government expects suppliers to meet their contractual obligations and Canada will not accept the helicopters until contractual requirements are met," Annie Trepanier, the manager of media relations at Public Works said in an email.
"The government of Canada continues to work with Sikorsky in respect to the contract."
The National Defence website says the aircraft is built with an aluminum frame to withstand high-intensity radio frequencies, but those are only one form of electromagnetic energy.
Defence expert Michael Byers, of the University of British Columbia, documented the Conservative government's struggles with the Cyclones in a report earlier this year.
The public deserves straight answers about the $5.7-billion program, he said.
"At some point, someone should say enough is enough," said Byers. "The question is, when are they going to stop messing around and deliver a highly functioning maritime helicopter for the men and women of the Canadian Forces?"
The Cyclones were supposed to be on the flight line in 2008, but Sikorsky has delivered only a handful of choppers for testing.
Former auditor general Sheila Fraser trashed the program a few years ago in a report that set out in painstaking detail how Paul Martin's Liberal government agreed to buy the Cyclones, even though the military version had not been developed.
The theme cropped up again last week in a leaked independent report that the Harper government commissioned. The analysis said the helicopters were essentially still in development and the federal government should attempt to salvage program within 90 days.
The air force recently sent a team to look at the runner up in the 2003-04 competition, the EW-1 Merlin, and a Public Works official said they are considering aircraft "other" than the Cyclone.
Byers said cancelling the program might actually boost the political stature of the Conservatives.
"The Cyclone was selected by a Liberal government and they have the political room to say, we tried, but the fundamental flaw in this procurement was just too serious," said Byers, who ran for the federal NDP in 2008.