Small Jet Operators Face Mandate to Inspect Wiring

‘Onerous burden’ feared in documentation and inspection proposals

SAVANNAH, Ga. – Operators of small jets can anticipate a wave of new wiring inspection requirements, based on recent inspections of a sample of the fleet and the need to bring comparable attention to the state of wiring that already has been applied to large jets.

At a meeting here last week, the results of recent wiring inspections of some three dozen small jets revealed numerous cases of chafing, broken insulation, dirt, chemical contamination, and inadequate separation of wiring from structure and flammable materials. In many cases, the wiring installations violated approved wiring practices.

“We found instances that should not have happened,” said Jon Haag. He led the task force that conducted the inspections. Known as Harmonization Working Group 10, the group’s Jan. 13 report was presented to the Aging Transport Systems Rulemaking Advisory Group (ATSRAC). The report requested exemptions from practices earlier endorsed by the ATSRAC to assure the safety of wiring in large jets. As such, the exemptions stimulated a vigorous debate.

For the moment, small jet manufacturers and operators have achieved some relief from what their representatives here perceive could be a costly mandate to trace the installation of every wire installed in the airplane and to conduct close visual inspections.

The long term implications, however, seem clear enough. Wiring and associated components have acquired a new priority that will translate into a greater emphasis on training, awareness, maintenance, inspection and documentation. Regional airlines and the host of other small jet operators can expect regulators to apply essentially the same standards and requirements to their aircraft as have already been taken for large jets. For small jets, the timing remains uncertain, in contrast to inspections in large jets of cockpit, electronics and equipment (E&E) bay wiring and power feeder cables slated to commence around January 2006 (see ASW, July 15, 2002).

The population

There are some 8,600 turbine-powered multi-engine aircraft in service capable of carrying 6-30 passengers and weighing upwards of 7,500 pounds. Falling into the small transport aircraft (STA) category, these aircraft are built by five different manufacturers and tend to operate in smaller fleets. For example, the ratio of owner/operators to aircraft averages 1-to-1.4. In comparison, the ratio of carriers to large transport aircraft (LTA) is on the average of 1-to-108.

The LTA fleets are more standardized, and their operators typically feature engineering departments. In the STA community, engineering departments are a rarity, avionics packages vary widely and interiors are changed out more frequently. While large aircraft may have numerous owners during their service lives, their smaller brethren may lead more unstable lives. One airplane had three owners in five years and the cabin fittings and avionics were changed out each time. As another indicator of the lack of standardization, some 15,000 supplemental type certificate (STC) modifications have been previously approved and installed in the STA fleet. Not all are electrically related, but all could potentially require review for their impact on electrical wiring interconnection systems (EWIS). This term includes not only the wiring but also clamps, connectors, shields, circuit breakers and the like.

In addition, some 65 percent of STA operators do not perform their maintenance “in house.” Rather, the majority of the maintenance is “outsourced,” creating further potential for non-uniform practices and further variability for the same model aircraft from one operator to another.

In simplest terms, the LTA community can be likened to larger “nation states,” while the STA community is significantly more “Balkanized.”

The findings

To determine the state of wiring in the STA fleet, a representative sampling of 39 aircraft with more than 15 years of service was subjected to general visual inspection (GVI).

The inspections uncovered more than 2,281 individual wiring-related discrepancies, for an average of 58 discrepancies per airplane. None were deemed immediate “fleet wide safety of flight” concerns, but similar comforting caveats were uttered when dozens of discrepancies per airplane were found in the earlier GVI inspections of LTA (see ASW, March 19, 2001).

The findings were similar in terms of the major problem areas. To these comparative findings, a few observations are in order. In terms of wiring condition, breaches were found in the insulation; these are important as insulation breaches can provide a pathway for electrical arcing.

In terms of wiring installation, one example featured two circuit breakers with 4-gage wire connected to them bent so severely that the insulation was wrinkled. In another instance, wiring in a galley was found rubbing against structure. This example relates to the large number of STCs issued for the small aircraft. The rubbing wire was an STC installation. To be sure, the aircraft manufacturer had issued a service bulletin (SB) to correct the problem, but this case illustrated that manufacturers often find themselves issuing such bulletins to correct STC installation errors. Of the 2,000+ discrepancies, an unknown number were STC-generated.

Visually, the wiring in general appeared to be in better condition than for the large transport aircraft, but when bundles were opened up during intrusive inspections, metal shavings were found. The chemical contamination was less severe; the amount of dust and dirt accumulated on the wiring was less. As in the case of the large transport inspections, not all the damage was caught by GVI. Intrusive inspections were necessary to assay the full extend of degradation.

When the flight hours and flight cycles of the two fleets are compared , the small transport aircraft with the greatest number of hours does not come close to the large transport with the lowest hours in service (17,389 vs. 21,000). The small transport aircraft with the least number of flight cycles was significantly short of the large transport with the smallest number of cycles (2,639 vs. 8,633).

In short, the smaller aircraft were used a lot less, but when examined their wiring was not in that much better condition. The degradation was disproportionate to time in service.

For these reasons, Capt. Ken Elias, representing the Air Line Pilots Association (ALPA), suggested that the same approach being used for the large aircraft be applied to the small jets. The ALPA position is that the same level of safety in regulatory oversight should be applied to all revenue passenger-carrying aircraft. The small transport wiring findings indicate similar problems as those found on the large jets. The approach for large jets involved an enhanced zonal analysis procedure (EZAP), in which each and every original wire, and each and every STC-related wire, would have to be mapped out and inspected as part of a comprehensive wire integrity assurance program over coming years (see ASW, July 15, 2002). This approach might not be required for all STCs ever issued for small jets, but perhaps could be restricted to that fraction of the small jet fleet – about three percent – in revenue passenger service.

Exemption requested

The members of the small aircraft task force said the EZAP protocol would involve a nightmarish process of reviewing wiring related aspects of all STCs. “The FAA [Federal Aviation Administration] did not require detailed design drawings 15 years ago,” said Ric Peri, vice president of government affairs for the Aircraft Electronics Association. Since the drawings do not exist, aircraft would have to be pulled in, torn apart, all their STCs reviewed and their wiring examined.

Since about 95 percent of the wiring would be examined in a small transport aircraft at some time during maintenance intervals ranging from 150 hours to eight years, the need for EZAP was questioned.

Referring to the scheduled carriers, Elias Cotti of the National Business Aircraft Association said, “EZAP is appropriate for Part 121 operators,” but he described EZAP as an “onerous burden” for the small aircraft community.

The small aircraft community representatives requested they be granted a choice: EZAP or “an equivalent analytical process.”

Kirk Thornburgh of Northwest Airlines said, “I am uncomfortable with this ‘other analytical process.’ I don’t know what that is. If you don’t use EZAP, what will you use?”

By taking the zone-by-zone approach to the aircraft, which is inherent to EZAP, Thornburgh said the process has forced positive changes among the large transport operators. Operators look at what the wire does, where it comes from and goes, any contamination, the state of connectors, the wire’s proximity to combustible materials, and so forth.

Kent Hollinger, ATSRAC chairman, described the EZAP process as pro-active, “rather than issuing a service bulletin after a problem is discovered.”

Without EZAP, Hollinger asked, “How would an OEM know that a power cable to a microwave oven isn’t strapped to a fuel line?”

Working Group 10 chairman Haag said, “We currently look at the wiring in the aircraft … and if there is a requirement to go do EZAP on every STC, that is a huge problem for our industry.”

There is no dispute over the applicability of EZAP to future STCs. “Our problem is the past and going through an EZAP for every STC that was ever installed in an airplane,” Haag demurred.

The Air Transport Association‘s Ric Anderson said bluntly, “I do not agree with giving small transport operators carte blanche to do what they want to do.”

Fred Sobeck, a senior FAA official who ultimately would have to bless an alternate means of complying with the EZAP dictat, said, “Working Group 10 is hanging its hat on this analytical equivalent that I do not understand clearly.”

Chairman Hollinger suggested exempting small transport operators, “based on the regulator’s acceptance of the OEM’s analytical equivalent.

Exemption approved

The committee adopted this proviso on a 16-1 vote. The FAA’s Sobeck was a non-voting participant in the proceedings.

The one “no” vote was registered by Cliff Neudorf, representing Transport Canada, that country’s equivalent to the FAA. Neudorf explained his concern: “We haven’t defined what’s happening with this analytical logic. If we’re going to start mixing analytical logics you have synergy for disaster.”

He feared the potential for different inspection procedures and intervals between manufacturers and operators.

Neudorf pointed out that the notion of mixing maintenance protocols was soundly rejected at the International MRB (maintenance review board) Policy Board. “We took the decision not to mix different versions of analytical logic,” Neudorf recalled. As an example, the policy board rejected the notion of applying MSG-3 maintenance doctrine to engines and the MSG-2 guidance to structure.

Given the need for standardization and harmonization, Neudorf said, “We don’t want to put in place a system that’s unworkable.”

He pointed out that, the potential for mixed, proprietary maintenance protocols aside, “the OEM can simply specify nose-to-tail DVI [detailed visual inspection] and you’d get pretty much what EZAP will do.”

Nonetheless, Sobeck indicated the potential for different practices between large and small transport aircraft. Of the 8,000 small aircraft, he said about 270 of them are in regular passenger service. He indicated that when the “equivalent analytical processes” for complying with the new battery of wiring inspections are submitted to the FAA, they will have to look very similar to the EZAP process to gain approval.

Contretemps over new regulations

A dispute could be in the offing on another point raised by the small airplane group. They asserted in their Working Group 10 report that the wiring inspection results “do not support” proposed rulemaking known as Subpart H, and therefore applying its provisions “is not necessary to achieve the desired level of safety for small aircraft.”

Subpart H represents a battery of new EWIS standards to be incorporated into Federal Aviation Regulations. Some 28 new provisions embodied in Subpart H will include specific barriers and distances for wiring, and notably not an equivalent or alternate method (see ASW, July 15, 2002). Working Group 10 chairman Haag said, “Our opinion as a working group is that we don’t agree with Subpart H.”

ATSRAC chairman Hollinger countered that just two months ago the committee sent a document to the FAA recommending that Subpart H be incorporated into the FARs, and “this action takes the opposite course.”

ALPA representative Elias said the 2,000 wiring discrepancies provide a clear rationale for not exempting small transport aircraft from the Subpart H standards. The findings for small aircraft were similar to the earlier inspection findings for large jets; therefore the same regulatory standards should apply.

The committee voted to include a footnote in the Working Group 10 report that it does not agree with exempting small jets from the Subpart H standards.

The FAA, of course, can establish whatever applicability it deems appropriate. FAA officials expressed the view that passenger jets flying as Part 21 scheduled service should be treated from a regulatory standpoint the same as the large jets.

Haag recognized the tectonic shift that has occurred. “Wiring has become an issue over the past four years. This is a whole new ball game in terms of priority,” he acknowledged.

Discouraging Findings

The ALPA view of the wiring findings for small jets:

“Upon examination of the Working Group 10 evaluation results … it is noted that 31 percent of the significant items were due to wiring conditions. In the December 2000 [Large] Transport Aircraft Intrusive Inspections Report the comparison figure was 35 percent. The data in other categories of these evaluations is similar.

“The relatively small differences in the data become more meaningful when the extreme airframe hour range and cycle range of the large aircraft are considered. It would be reasonable to assume that the number of items detected … should be significantly less. The aircraft inspected by Working Group 10 were all operational aircraft while the large transport inspections were performed on decommissioned (salvage) aircraft.”

Source: ALPA, Jan. 16, 2003 letter to chairman, Small Transport Category Aircraft Harmonization Working Group 10 (extract)