September 25, 1996

Dear Members,

Three excellent PBS documentaries, "Why Airplanes Crash", "The Crash of Flight 201", and the multi-part series on "Building of the Boeing 777", prompts me to write to you.

"Why Airplanes Crash" highlighted how simple problems can have the most dire of consequences. It showed why everyone concerned with aircraft safety needs to stay constantly alert to any possible problem, and be responsible enough to take action to correct these problems.

In "Flight 201" bodies were shown strewn throughout a South American jungle, apparently the result of a pilots response to a intermittently malfunctioning position indicator caused by a loosly connected wire. The "Boeing 777" series talked about why Boeing switched from a potentially safer 4 engine design to a two engine design to eliminate half of the intermittent wires that couple the engines and sensors to the control computers.

The purpose of writing this letter is to alert the commission and others in the airline industry, to the availability of a new technology that now allows you to test for these intermittent failures in large complex avionics systems.

We are a small startup company, with an excellent patent-pending product, but a limited advertising budget. We, in behalf of ourselves, the airlines and the traveling public, would like your help in getting this information to those people and organizations that are in a position to expedite implementation of a unique win-win solution to a chronic problem.

Intermittence, once just an annoyance for the technicians, has grown to be the "achilles heel" of modern aircraft electrical and avionics systems. Forgotten and ignored for years by test engineers and test equipment manufacturers, it has become the cause of major maintenance and safety problems for the airline and defense industries.

As every technician knows, there are only two types of failures in any electronic system; hard failures and intermittent failures. To find hard failures, technicians have dozens of specialized and generic pieces of test equipment. However, to find intermittent failures that may occur on any one of hundreds of circuits, and randomly at any time, the test equipment in place fails miserably.

These intermittent failures in the aircraft electronic and electrical systems are causing delayed or aborted flights, emergency landings, wasteful and expensive repairs, compromised safety and even crashes.

Most of these intermittent problems are the result of the aging of the aircraft electronics and wiring. Over time, electrical wires and connectors wear or corrode and solder joints become loose and break. Wires rub and chaff on the bulkheads, eventually shorting to the airframe or other wires. Sensors and relays become erratic or noisy and previous, improperly made repairs begin to cause problems.

Pilots and passengers experience the effects of most intermittent problems while in the air. After the aircraft is on the ground and the systems are out of the stressful operating environment, the technicians find that intermittent failures are hard to duplicate and even harder to isolate. Because of limited turn-around times, the failures that don't repeat on the ground often go unrepaired or are swapped out. This is generally referred to as the "No Fault Found" (NFF) or "Can Not Duplicate"(CND) problem.

Putting a NFF or CND label on a unit that tests OK out of the aircraft, is easier and more economical than trying to actually find the problem. So "labeling" it a NFF, often becomes the "repair action" of choice. The alternative is to test the unit repeatedly, often for hours or days, and wait for the problem to reappear, and then hope your test equipment can detect and isolate it when it happens.

This inability to detect NFF or intermittent problems has been going on for so long now that the word "intermittent" has become disassociated with the terms NFF and CND. When a suspect unit is tested and no faults are found, rather than applying a little environmental stress to help trigger an intermittent fault, technicians sometimes tend to view the phenomenon as something mysterious, or possibly that the pilot made a mistake. 

When an intermittent unit is encountered and they try to isolate the problem to a particular wire or component, they may wiggle a wire harness or connector, or reseat the circuit cards, causing a temporary connection to be made. If this "repair" lasts long enough to pass the test, then the unit is accepted as "good" and is reinstalled in the aircraft with no "real" repairs being made.

According to Avionics Magazine, relative to American Airlines, NFF or CND problems account for 40-60 percent of all reported avionics failures. Studies indicate that military avionics statistics are comparable. These are average numbers; in certain older aircraft the intermittent defects could reach as high as 70-80 percent of all failures.

Many accidents seem to occur during high physical stress times such as take-offs, landings and turbulence. This is also the same time that intermittent problems are most likely to occur. With so many documented, stress-triggered, unrepaired defects, could it be possible that the root cause of numerous accidents are due to intermittent defects in the avionics that the pilots rely on to control the aircraft during these critical times?

The military, airlines, NTSB and FAA are all pursuing their own methods of reducing NFF problems and improving safety. The NFF problem has been the main topic of discussion, at the Avionics Maintenance Conference (AMC) for the last two years. The Air Force is studying the use of Portable Maintenance Aids (PMAs) and Onboard Diagnostic programs to "ease" the burden on the flightline technicians.

It has been our experience that many in this industry want to "talk" about the "No Fault Found" problem, but few actually understand it. Neither the military nor the airlines, has yet made the "connection" between intermittent defects and their mysterious NFF/CND problems, and neither group is doing anything that tackles the problem directly with a testing solution.

Now that a new testing technology is available to eliminate NFF problems, isn't it time to reexamine these other programs or at least combine them with this progressive and economical testing solution? Logic says yes, but mind-sets, budgets, politics, funding and self interests resist.

To remedy some of these problems expeditiously, this is what we challenge the commission to do:

• Instruct the NTSB to investigate accidents with more of a suspicion that intermittent problems may be at the root of all accidents.
• Mandate that the FAA improve it's directives on inspection techniques concerning intermittent or NFF problems. They should require testing for intermittents or NFF problems with equipment that can "see" the problems, and not rely on visual inspections and Automatic Test Equipment as being adequate.
• Determine what steps technicians and their management should follow to resolve NFF problems based on a safety viewpoint rather than repair production rates or self interests.
• Reexamine expensive defense programs that are attempting to resolve NFF/CND problems using inferior methods that may even add to the complexity of the problem.

This "No Fault Found" problem is not new, but it is getting worse as more and more electronic sensors, computers, control functions and wires are being added to todays highly complex aircraft.

Proposed NFF reduction programs such as On-board Diagnostics, Portable Maintenance Aids, Tracking of NFFs, Tracking of CNDs, Tracking of Anomalies, Tracking of Rogues, Redundant Systems, Backup Systems, Fault Tolerant Systems, Programmed Maintenance, Scheduled Maintenance, Delayed Maintenance, In-the-Air Maintenance, Remote Maintenance and all other Huff-n-Fluff, NFF work-arounds, are not acceptable as stand alone solutions to random intermittent connectivity problems.

At best, these programs may identify an intermittent unit, but when it is sent to the depot for repair, they are right back where they were, no way to test, isolate or repair the exact cause of the failure.

At worst, these programs give us a false sense of security. Edward Tenner in his new book "Why Things Bite Back:

Technology and the Revenge of Unintended Consequences", speaking about Titanic like disasters, states that "a belief in the safety of the ship [becomes] the greatest single hazard to the survival of it's passengers." Maybe we should think about this the next time the airline industry congratulates themselves on having the safest mode of transportation in the world.

Unless intermittence testing is used to find these NFF problems, there may come a time when the burden of maintaining all these new avionics improvements will result in an aircraft that is either too expensive to operate safely, or too unsafe to fly.

That time may be sooner than most may think.

Please contact me if you have questions or concerns to discuss. I would appreciate communication from you on this subject. I offer my assistance and expertise in any useful way you may determine.

Thank you for your time and attention in looking at this serious problem,

Enclosures:

1. AMC Proceedings 1995: Keynote speech concerning NFF problems in the industry.

2. AMC Proceedings 1996: Solving NFFs, a Depot perspective.

3. Avionics Magazine Sep. 1996 Finding No Fault, and other problems that cause NFF.

4. Avionics Magazine Service Alerts, Sep. 1996, Several examples of problems the IFD-2000 is designed to find on the ground, before they pose a safety problem.

5. Avionics Magazine, Various safety bulletins from 1995, More insights into NFF problems.

6. IEEE White Paper from AutoTestCon 1994, Our view of the problem from a military perspective.

7. Sales Brochure from Universal Synaptics, Highlights of the NFF problem and and the benefits to be gained.

8. Test and Measurement World Magazine, Sep. 1996, Comments by Jon Titus, editorial director, about intermittent problems and our IFD-2000 tester, after a recent visit to our facility.