High Flying Measures

by Joe Cebulski

Joe Cebulski demonstrates a test indicator calibration to Andy Lozinski. (photo by Micheal Clifton)

In the airline industry, safety has always been the top priority. Calibration of all measuring and test equipment verifies accuracy and reliability, which contributes to safety assurance. Calibration shops were originally established in the airline industry to meet Department of Defense contracts, which required compliance with MIL-STD-45662A, Calibration System Requirements. Air carriers receive authority to operate from the Federal Aviation Administration (FAA). They are the national agency responsible for developing regulations, and for certification and safety oversight of over 7,000 US and international commercial airlines and air operators.

Following findings in 1996 that maintenance and repair may have contributed to several aviation accidents, the FAA tightened its scrutiny of a Federal Aviation Regulation (FAR), which required that all measurements be traceable to the US national standards held at NIST. FAR 121 then stated, “… all inspection and test equipment must be tested at regular intervals … to a standard derived from NIST or to a standard provided by the OEM.”

Foreign airlines typically own and operate inspection and test equipment that is calibrated with traceability to their own national standards. If they serve cities in the United States, they fall under the guidance of this FAR. US cities at that time were served by over 1200 daily international flights. Foreign repair stations frequently perform maintenance on US aircraft, such as fueling, de-icing, and routine or emergency repairs. The FAA challenged the compliance of these inter- national airlines and repair stations. This posed a major impact on these businesses, to either bear the additional costs and difficulties of sending measuring equipment to NIST traceable labs for calibration, or lose their FAA certification to perform this maintenance or to serve American cities.

For discussion on this topic, representatives from American, Ansett Australian, Continental, Delta, Northwest, and United Airlines met with NIST representatives at the 1998 NCSL conference. Discussed were some questions from the FAA regarding traceability to national standards. Dr. Stephen Carpenter of NIST was present to explain the FAA had turned to NIST for guidance. He spoke of the pending Mutual Recognition Agreement with many other national measurement institutes. He also committed that NIST would continue to advise the FAA and our committee members to advance our understanding of calibration and traceability.

At that meeting, other calibration and tooling issues of mutual interest were discussed. The attendees agreed to form a committee of the NCSL dedicated to metrology issues in the airline industry. Industrial committee 156- Airline Metrology was formed. There has been participation from Delta, United, American, Continental, Northwest, Air Canada, Ansett Australian, Varig, Thai, Finnair, and Frontier Airlines.

An outstanding benefit of our industrial committee is the opportunity to discuss tooling issues, problems, and solutions. Since many airlines maintain similar fleets and engines, much of our required tooling is also similar. Challenges and solutions to particular tooling issues can be discussed with other members in our committee. Here are some examples of shared successes. Many analog tire gauges are not rugged enough for the brutal conditions on the flight line. The first airline in our committee to intro- duce digital tire gauges into service was able to report excellent results. This particular gauge proved to be more durable and reliable for our flight line conditions. 

When some carriers experienced concerns with torque multipliers, a solution came from within our committee. Another member suggested the multiplication factors that are placarded on the device from the factory must be removed and revised when calibrations identify errors or changes.

Mechanical tensiometers have historically been high maintenance, low reliability. At our request, a prototype electronic cable tensiometer was designed and manufactured primarily for airline use. Samples of this prototype were put into limited field service for evaluation. The feedback was favorable. A few modifications were suggested, and are being built into the new design. We expect this new design to reduce maintenance and reliability problems.

In Non-Destructive Testing, most airlines use TAM panel fluorescent penetrant inspection (FPI) standards. These chrome plated metal panels have five cracks formed in the chrome. They are used to validate the FPI process. Since these panels have raised some quality and safety concerns in the past, some airlines take great care to calibrate and document the processing of these panels. We believe their calibration procedure for these panels is the best in any industry.

Another benefit of this committee has been improvements in tool procurement.

Calibration Technician Robin Hubel inspects transducer during engine cell testing.
 The purchase of unreliable or inappropriate tooling in the past has caused problems and expenses for our operations. United Airlines has developed a calibration steering committee, which guides and recommends tool procurement. At Delta, we have developed an Approved List of Calibrated Tools. These are tools proven through years of service and calibration to be accurate and reliable.
Since the inception of this committee, some airline members have developed Out of Tolerance Notifications and Corrective Action Reports. These notifications prompt an investigation by engineering or the Quality Assurance Department. This method ensures that a tool found with an out of tolerance condition did not cause an unresolved problem. At Delta Airlines, after implementation of these notifications, out of tolerance conditions with torque wrenches caused laborious and expensive evaluations. As a solution to this problem, they installed torque testers at the large tool rooms. Torque wrenches are tested at each check-out and check-in. This eliminates the possibility of an out of tolerance wrench going into service, and generates an immediate response when a wrench is found in error.

Our committee has completed one very informal Interlaboratory Comparison (ILC) with a set of four ring gages. Four airline calibration labs participated. As a result, one participant identified some process errors. All participants were satisfied with the results, a plan to improve confidentiality was recommended for the next ILC.

We are excited about the training opportunities available as members of the NCSLI. Many of our members attend conference training, and some have attended the Uncertainty Road- show now available. We also have the opportunity to receive training from tooling vendors of mutual interest to our members.

Meetings are scheduled, at each MSC and NCSL Conference, and quarterly at a member airline facility. American Airlines hosted the first quarterly meeting, which included a tour of their calibration facility. Continental Airlines also hosted a meeting at their Houston tooling and calibration shop. After a tour of their facility, the group was treated to delicious genuine Texas brisket and barbeque. United Airlines frequently hosts our committee meetings at the Denver Airport. It is our most popular meeting location, because most members can fly in and out on the same day of the meeting. Delta Airlines hosted our most recent meeting at the Technical Operations Center in Atlanta. Members enjoyed a tour of Delta’s physical and electronics calibration labs. They visited the fuel and hydraulic components test shops. They observed operation of a Labmaster Measuring System, a Sweeney Torque Multiplier calibration, and an Axiam engine build system. In the aircraft sheet metal shop, they were shown a demonstration of reverse engineering of airplane floor panels, using a Faro Arm Measuring System and five axis router. The committee meetings at our respective maintenance bases are usually the most productive. Members have the opportunity to network with many specialized technicians. Testing and calibration demonstrations are very beneficial.

Efforts are proceeding in many airlines to improve data collection and calibration record keeping. Most are using existing maintenance and repair

Tom Weber reviews features of a Calibration Report with the airline committee members, from left to right: Andy Lozinski, Joe Cebulski, Siraj Rajabali, Randy Jones,Tom Weber.

Tom Weber reviews features of a Calibration Report with the airline
committee members, from left to right: Andy Lozinski, Joe Cebulski,
Siraj Rajabali, RandyJones,Tom Weber. (photo by Michael Clifton)

software, customized or assisted with Excel or commercial calibration software. The coordination of repair, maintenance, and scheduling at an airline maintenance operation is already a formidable task for any software program. To successfully integrate calibration record keeping; with data collection, procedures, traceability, uncertainty calculations, into this program will be a remarkable achievement. No airline member yet has an enterprise level calibration records system with all of these features.

Airlines have seen record losses and even bankruptcy filings in the past few years. Many have been through leadership changes. It is sometimes challenging to justify the value of our NCSLI membership to managers unfamiliar with calibration and metrology. While our airlines endeavor to return to sustained profitability, it is our charge to continuously improve our calibration system’s efficiency and quality. Membership in the NCSLI Airline Metrology Committee gives us additional tools and opportunities to achieve continuous improvements. These improvements ultimately improve the safety of our operations. Our commitment to safety is evident by the collaboration in this committee.