Keep the Proper Perspective
I certainly applaud anyone’s efforts to make flying safer. However, I think it is also important to keep things in proper perspective.
In the article "The More Complex the Better" in the November 2003 issue, George Marsh quotes LHT (Lufthansa Technik AG) as working with a no fault found (NFF) rate of 25 percent. But in a presentation at the Airline Maintenance Conference, James Pierce, chairman of ARINC, has placed the problem of no fault found at 50 percent of all pilot reported defects. Your publication, on several occasions, has echoed and confirmed that the industry indeed has a 50 percent NFF rate overall.�
Your Editor’s Note, however, as well as Walter Shawlee’s fine column, brought up the rather benign subject of personal electronic devices (PEDs). You indicate to your readers that PEDs are a "runaway" problem that needs some sort of immediate attention. In studying the metrics of your decision to editorialize on the subject of PEDs, at the expense of NFF, we find the following:
The British Civil Aviation Authority (CAA) found 35 instances of PED anomalies over a seven-year period, or five per year. The sample size was not given, but it is probably safe to assume it is rather large.�
In the LHT case, the sample size is 55,000 units. By LHT’s own estimates, that equates to 13,750 known and documented defective units being placed back into service by just one repair center. If we use a more realistic NFF rate of 50 percent and we plug in a modest increase in shop or repair incidents of 500,000 for all avionics failures worldwide, you get 250,000 anomalous, unrepaired NFF failures hazarding the world’s fleets every year.�
The overall PED rate, boosted by the same ballpark estimates, may amount to 50 per year. The PED problem, when compared to the NFF problem, then, is only 0.02 percent as serious. To make matters worse, since NFF rates generally increase dramatically with the age of the aircraft systems they are in, the NFF problem is undoubtedly age-related. This means intermittentcy in the connectivity elements, shielding, solder joints, etc. is to blame.�
It follows, to some degree, that if you fix the wiring so it is no longer intermittent or NFF, you may also take care of a large portion of the PED problems. Why not, then, instead of devoting so much magazine space to PEDs, focus on the real problem, NFF, with editorials and more articles on NFF and the improper testing that allows these anomalies to escape detection?��
Brent Sorensen
President Universal Synaptics Corp.
Ogden, Utah
Response
You make valid points about the importance of reducing no-fault-found (NFF) anomalies. In the article mentioned, however, Lufthansa Technik AG (LHT) does not say it is working with a 25 percent NFF rate. Rather, the company comments that the often quoted 25 percent NFF rate is overstated. Much equipment, LHT contends, is deemed faulty because of improper operation or external issues such as antenna corrosion.
–Editor
Corrections
An article in our February issue incorrectly stated that the signal structure proposed by the United States for the Galileo satnav system’s open service would have 50 percent less impact on the U.S. ability to use the military GPS M-Code than would Europe’s preferred OS modulation. The correct way to describe the comparison is that the preferred European modulation would have 50 percent greater impact on the ability to use M-Code.
And, in our January Scan section, we reported that Curtiss-Wright Corp. acquired the Dy 4 Systems business from Solectron Corp. and will make it part of Curtiss-Wright’s Vista Controls Division. In fact, Dy 4 will not be part of Vista Controls but will be a separate entity within Curtiss-Wright Corp.
–Editor