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What happens with the MRO after the project kick-off meeting?

In his ongoing series, Ken Elliott describes how a typical MRO would handle an ADS-B Out installation in a business jet after an operator has attended a kick off meeting with company personnel.

Upon arrival at the selected MRO, your aircraft will be assigned a crew chief who is a senior airframe mechanic and proficient with your specific make and model. The crew chief has the delicate task of juggling the schedule, so that avionics, interior and airframe-engine specialists can conduct their work tasks. (Along with engineering, procurement and certification, some avionics tasking is also conducted off the aircraft itself.)

It is common for avionics shops, including those embedded in MROs, to have two primary functions—installation and service. One set of specialists focuses on the upgrade, while the other handles day-to-day inspection items and repairs. As the customer, you are likely to find yourself dealing with both.

The avionics team may also be supplemented by a sheet metal and an interior shop, both of which carry out work independently on behalf of the airframe groups. It is surprising just how much interior, sheet metal and even paint touch-up is directly related to an avionics modification.

Note that the interior team will undertake a removal and reinstallation (R&R) of the aircraft interior as required. This may extend to a complete removal of cockpit and cabin furniture, galleys, sidewalls, overheads and bulkheads. Do not be surprised to find a day or two added to either end of a schedule to accomplish interior R&R.

On larger projects this complete team of skillsets can be a formidable presence on and off the aircraft.

Avionics Wiring

For an avionics upgrade at the magnitude of ADS-B Out, there will be wiring required. The avionics team will conduct some of that preparation away from the hustle and bustle of the hangar floor.

Complex avionics harnesses will route different ways throughout the aircraft, and technicians will pre-lay harnesses on vertical boards in the wiring shop. Each wire is laser stamped with a dedicated code; then each harness is sleeved and marked, making it easier to pin into connectors and better still, troubleshoot later.

Harnesses will typically terminate at connectors or equipment racks. Few owners realize the quality and reliability of these miscellaneous items found everywhere throughout the aircraft. Industry has come a long way, through many costly learning experiences, to today’s modern installation.

On board the aircraft, the avionics technician will connect for power as needed, always with some form of circuit breaker protection. Do you recall the coaxial cables used for television whisker antennas or for video connections between devices at home? Aircraft still need antennas and in some cases may need a dedicated or updated antenna (e.g., ADS-B’s Global Positioning System satellite signal requirements).

The technician will be routing these coaxial cables as well as regular wiring. Coaxial cables can be delicate and often require special care in termination. Another cable that has its own special connectivity tooling is fiber optic, which serves as a super highway for high-speed and broadband data transfer.

Careful thought will be given by the avionics engineer to a whole host of safety, access, routing and future troubleshooting considerations specific to your wiring harness. Both the systems and the certification engineer will have carefully followed a checklist of dos and don’ts to ensure the finished product will pass a quality inspection.

The Equipment

Let’s assume that the aircraft needs two new transponders and upgraded dual GPS for equipage of ADS-B Out. The equipment delivery schedule is, of course, as important as the aircraft work itself. As the aircraft owner or operator, you should not hesitate to confirm the equipment is in-house (ask to see it).

If still on order, make the calls to the modification-shop to ensure the necessary components are on their way. This will become more critical as we draw closer to January 1, 2020 and the remainder of the 15,000 business jets in the US alone are each scrambling for their ‘boxes’.

While not equipage per se, the ADS-B Out upgrade requires a special annunciator. Sophisticated business jets may require a change to an existing unit, system or even software modification, to allow electronic annunciation of ADS-B Fail. Often the installation delay is created because of the time it takes to ship, modify and return aircraft systems.

For both the GPS upgrade and the modification for annunciation, there is a possible need to subcontract the work required. With all the best intentions, shops can fail in this endeavor because of all the touch points involved. From paperwork, to shipping, to factory schedules and inspections, there are many places a slip-up or delay can occur. Even weather can spoil the plan, especially when the shop had promised just a few days to complete all tasks.

With respect to the Transponders used for ADS-B Out, they are required to have extended squitter, widening the bandwidth to accommodate the extra packets of aircraft data the transponder needs to broadcast. These data include a unique 24 bit ICAO address for each aircraft and may be strapped in the aircraft itself or programed into a module. As an aircraft owner or operator, ensure this address is registered and more importantly, correct for your aircraft.

You may know the address but if wrongly strapped or programmed, it will broadcast incorrect information. The Mode S address, as it is known, is tied to the registration number of your aircraft. The FAA registry has a dedicated address for each N number assigned. If you change your aircraft N number, be sure to ‘re-strap’ or re-program your aircraft equipment accordingly.

Engineering, Certification & Inspection

In aircraft design there are some baseline considerations for engineering and certification, all of which fall in line behind the overarching criteria of SAFETY.

Somewhat behind the scenes, the systems engineer will be fine-tuning existing prints, based on input from the shop floor. It is normal for each aircraft to have slight differences. The older the aircraft, the more likely that will be.

Technicians will discover such irregularities as they progress through the install, and the engineer will clean up the prints and any structural drawing as required. Meanwhile the certification engineer will be finalizing the paperwork to allow any individual approvals to take place. For an ADS-B upgrade, such approvals could be for box mounting and pressure bulkhead penetration, for example.

Each aircraft team will have an inspector (the inspection department falls outside of engineering and systems certification). Inspectors support all work on the aircraft and are responsible to ensure both the quality of the work completed and the overall safety of the aircraft. The certification engineer will be focusing on compliance, mainly with respect to data that systems engineers previously provided and possibly then modified.

The importance of the three support functions of engineering, certification and inspection cannot be stressed enough. Those job functions will ensure safety and very often be the enablers for your aircraft to leave on time. It is not uncommon for a delay to occur because of a minor difference between a drawing and the ‘aircraft as modified’.

However frustrating that minor difference might be, these corrections must be resolved prior to releasing an aircraft back into service. The final arbiter of the aircraft’s release is the inspector, who has the enormous responsibility for all the work of the MRO’s specialists and for the complete aircraft.

Before final inspection and as part of certification, the engineer (who may be a Designated Engineering Representative for the Airworthiness Authority) will check for conformity and system functionality. The work of the DER is conducted at two levels; a company test with regulatory conformity and test for final approval.

One precedes the other and allows for any corrections to be made, thereby not wasting the time and resources of airworthiness designees. For an STC, the process is significantly involved with many steps and milestones, including design reviews.

Ground and Flight Test (ADS-B Out)

As previously noted there is often an installation and service side to the average avionics shop. Once the work is complete the installation team will hand off the aircraft to the service specialists. The service team will already be involved in items related to an aircraft inspection, conducting routine continued airworthiness tests such as pitot static and verifying system functionality.

Using sophisticated test equipment, technicians will complete performance checks based on manufacturer instructions. Anything found out of order on the upgrade will be reverted to the installer for rework or engineering redesign. Meanwhile, any equipment found to be faulty will be replaced directly by the service technician. This additional activity may add to the schedule, or at the very least squeeze it into overtime.

For our ADS-B Out example, the extent of the work requires not only a ground test, but also flight check. Before the pilots can launch into the skies, however, the aircraft must go through a final inspection and receive that all-important blessing of the inspector and be documented in the aircraft’s logs.

With respect to ground testing of ADS-B Out, recently the FAA issued a Safety Alert For Operators (SAFO 17002) highlighting the hazards of some ground tests interfering with active air operations. Technicians testing aircraft systems simulate the aircraft at specific altitudes, and the on-board transponder will broadcast that reading along with other ADS-B aircraft information.

If aircraft antennas are not effectively shielded, the simulation of the test aircraft can appear to in-flight aircraft as a real target, even a threat, causing the receiving aircraft’s Traffic Collision & Avoidance System (TCAS II), to command a flight deviation. The SAFO directs modification facilities to consult three different Airworthiness Circulars (ACs) for testing guidance.

For the flight test, it is highly recommended that the aircraft owner’s pilots attend the pre-flight briefing. Knowing ahead of time the test flight profile and its anticipated outcome will be extremely beneficial to all.

The FAA provides for ADS-B Out Validation Flights. A visit to FAA’s website will provide the aircraft owner and MRO with the procedure for a validation flight. A date and time is requested, along with aircraft and equipage details. The flight will be monitored and the results e-mailed. These results are in the form of a Public ADS-B Performance Report (PAPR) and will be release typically within 30 minutes of the actual flight.

Note that ADS-B Out capability includes surface operations. If your aircraft is tested at one of 35 or more Airport Surface Surveillance Capability (ASSC) equipped facilities, your report will include surface performance.

A User Guide to the report, which can be complex, is available and will be very helpful to operators. Note that the test to verify ADS-B Out performance can also be conducted at any time during normal operations. Because the report also includes error codes and fault indications, it is very useful to provide this information to your maintenance facility if you suspect any performance degradation.

Return to Service

Producing a ‘Return to Service’ authorization is dependent upon a series of steps that the facility working on your aircraft must take beforehand, as highlighted by Figures E and F.

Product Support

Even though your test flight may have gone per plan, a payment was made and a return to service (RTS) issued, your visit is not complete until you have discussed product support. This can exist on many levels but, at a minimum, you should ensure the following:

  • Your equipment warranty is filed (or will be);
  • Some form of installation warranty exists (including workmanship);
  • You have a good contact for follow-up service;
  • The operations manual or instructions are in the aircraft (this may exist as a Flight Manual Supplement).

In Summary

If you have not already done so and are planning on scheduling your aircraft for an ADS-B Out upgrade to meet the 2020 mandate, hopefully you have gleaned from this and previous articles that there is much to the average work scope. In fact, what occurs behind the scenes is more than twice the activity at the aircraft.

When you see aircraft downtimes promising five-day turns, ask if your aircraft is the same as the one initially certified, whether the engineering is complete, and if equipment is in-house and harness kits are ready to run. If the answer is “no” or “not exactly”, expect added downtime (and cost). Hence the importance of checking all assumptions and promises long before you turn up with the aircraft.

It always takes a team to accomplish major work on your aircraft. As the owner, operator or designated pilot, see yourself as part of that team; you and your boss will be glad you did. There are many moving parts to the aircraft upgrade, as our ADS-B Out example illustrates.

While this article has covered some of the bigger steps and issues of the installation, there are still many more centered on the logistics of juggling airframe, engines, interior, paint and avionics that demand your attention. We will address some of those areas next month.

Read more on Business Aviation Avionics

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Read more about: ADS-B | Business Jet Maintenance | Business Jet Upgrades | Business Aircraft Avionics

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