MRO Operations: Upgrades and Maintenance

The words upgrade, refurbishment, and modification are frequently heard throughout the industry. I’m told it’s not uncommon to hear of a corporate flight department considering what it may take to operate an aircraft for longer periods of time rather than replacing it with a new aircraft. If a flight department were to keep an aircraft for a longer period than perhaps was originally planned, would consideration be given to upgrading it to gain operating efficiencies and to provide a new feel and look for the passengers?

Common upgrades include cabin interior refurbishment, cockpit avionics, or perhaps exterior paint, while others include engine upgrades or changes to the aircraft in order to gain greater performance. Would those upgrades mean significant modifications to the aircraft? Yes they would. Where would major modifications be accomplished, at a maintenance, repair, and overhaul (MRO) service provider, at the factory, or at a factory-owned or authorized service center? I have to imagine there are many factors to consider; more than I am aware I’m sure.

The impact on maintenance

From a technical and maintenance perspective, what comes to mind is all the activity that goes into the design, engineering, planning, and modification of an aircraft going through an upgrade program, and more importantly for the maintenance community, what impact might there be on the MRO and technicians that are providing maintenance services to a customer who operates an aircraft having substantial aftermarket upgrades? What maintenance program tasks have changed as a result of a modification, and how are the Instructions for Continued Airworthiness (ICA) implemented? What does the MRO providing future maintenance services on a modified aircraft need to be aware of? Perhaps there would be little or no impact on performing future maintenance.

AMT discussed the subject of upgrades and modifications to business aircraft with one of the original equipment manufacturers (OEM) Hawker Beechcraft Corporation (HBC).

At the 2010 European Business Aircraft Convention and Exhibition (EBACE), HBC announced an aftermarket upgrade package for the Hawker 800XP aircraft called the Hawker 800XPR. Among other options this upgrade will include replacing the aircraft’s original engines with new technology Honeywell TFE731-50R powerplants, and improving the aerodynamics of the aircraft by modifying the wing with HBC designed winglets similar to the 900XP. Additional upgrades could be cockpit avionics and of course the passenger cabin.

Brian Howell, vice president for strategic aftermarket integration, shares the HBC view of the industry and accomplishing upgrades to a flight department’s aircraft. Howell says, “First, the person or company who wants a new aircraft will buy a new aircraft. However, we feel there is a very real trend where people are deciding to keep an aircraft and do something to change it rather than replace it. Some customers become comfortable with a certain aircraft and decide to keep it.”

Howell shares three parameters that HBC feels drive an aircraft upgrade. They are the need to increase aircraft performance; the need to reduce aircraft operating costs; and the desire to protect the investment by increasing the resale value of the aircraft.

Howell says, “We believe that having major modifications accomplished to existing aircraft will be a big movement in the future, regardless of whether you own and operate a $2 million aircraft or a $50 million aircraft. It only makes sense that an OEM would participate in this movement. As an example, we’re looking at upgrades and modifications for most aircraft in our broad product lineup.”

Modifications are not limited to or only considered for older aircraft either. Howell shares, “Our market study looked at owners having 10- to 12-year-old aircraft, five- to eight-year-old aircraft, even owners of three- to four-year-old aircraft. A case can be made for upgrades in all of these groups by offering new aircraft technology in an aftermarket program.”

Modification design and engineering

Mike Edwards, chief engineer of the 800XPR program, says, “When considering an upgrade to an aircraft you must think through all of the details that go into the modification, and we feel the OEM is in a good position to do this. If all of the details are not thought through in the beginning, the customer may be left to think through the details themselves at a later date.”

He shares the first item when designing an aircraft upgrade: review the entire Type Certificate Data Sheet (TCDS) for the aircraft, and make a proposal to the FAA certification group that holds the Type Certificate (TC) regarding:

  • The scope of the upgrade and any submodifications
  • The upgrade’s proposed certification basis
  • How regulatory compliance will be demonstrated.

The FAA wants to be involved from the beginning of any modification that requires a significant change to the TCDS. Edwards says, “In many cases the engineering and technical data used for the original certification of an aircraft can be used during the design, engineering, and certification for a modification, which is a huge benefit.”

Edwards says, “A re-engine program is a complex exercise and every technical discipline in the company is involved. We try hard to minimize the downstream effect to all other aircraft systems, and the operation of the aircraft.”

As an example, he says, “We try not to dramatically change the concept of engine controls for the flight crew, and when possible mechanical controls remain mechanical and electronic controls remain electronic. Maintaining the same concept simplifies the certification path and maintains commonality with an aircraft that has not received the modification. Minimizing operating differences and procedures is a huge benefit when supporting the aircraft in the field.”

Once the new engine type is determined, and its installation characteristics and operating environment fully defined, all the related systems are reviewed for potential impact regarding design, certification, installation, and engine operating environment. These system reviews include cooling, heating, vibration analysis, anti-ice provisions, low pressure and high pressure bleed air provisions, fire detection/suppression, hydraulics, pneumatics, electric power generation, fuel and oil systems, engine control and health monitoring, thrust reverser operation, and more.

As for the engine nacelle on this particular modification, there are very few changes. The physical size and shape differences of the nacelle are very subtle, but the effort to integrate this powerplant with the existing airframe and aircraft systems is still considerable and deliberate in order to maintain the level of safety and operating simplicity for downstream customers.

The aerodynamics of the wing is improved with the addition of Hawker designed composite Winglets that were created for the Hawker 850XP. It is outwardly canted and constructed using advanced composite materials. The winglet installation includes an internal structural wing modification engineered by HBC. It is essentially the same winglet as the new production 900XP. Again, structural design and certification for the integrity of the new installation must be analyzed. A comprehensive review takes place that includes stress analysis, dynamic loading, and damage tolerance.

As for when an upgrade like this can be accomplished, of course, a logical time would be when the aircraft is due for an engine overhaul, or when the aircraft is coming due for extensive maintenance and inspections checks. As for where, HBC recommends that in order to keep long-term value in an aircraft, the OEM be engaged, and it feels strongly that an OEM supported facility is the better choice for having these types of upgrades and modifications accomplished due to the knowledge of the engineering and certification of the original aircraft.

Technical data and the ICAs

One of the most important parts with changing any aircraft configuration is to revise all of the technical data to ensure the MRO and maintenance technicians in the field who will be working on the aircraft in the future, have all the necessary information and complete instructions to accomplish the work in an efficient manner.

John Szelenyi, HBC director product support, says, “Our Technical Publications group is engaged from the beginning of the engineering and design and is part of developing the ICAs for the modifications.” ICAs may be listed separately in the aircraft maintenance manual (AMM) as supplements, or depending on the modification, an ICA may be directly inserted into the AMM instructions.

When asked what advice this OEM would give to MROs working on modified aircraft, Szelenyi says, “Closely review all of the ICAs established as part of the modification and build a relationship with the area field service representative for that type of aircraft. Most OEMs have field service reps located around the world, or they can be dispatched to any location worldwide to assist with maintenance if needed.” Szelenyi says, “ICAs are published on our Interactive Maintenance Library (IML) along with all of the other technical data needed to perform maintenance and inspection functions. As far as MRO support goes, we have the ability to grant total access to applicable technical data through the IML to any independent MRO or field technician.”

For an MRO perspective, AMT spoke with Shane Heier, engine technical representative for Duncan Aviation at Lincoln, NE, regarding ICAs on aircraft post modification. Heier shares that they do see differences in the level of technical detail in ICAs and other technical data from one modification to another. Heier says, “This is a very important issue. We’ve seen modifications having detailed ICAs and others that were vague. We’ve seen some ICAs where data had been inadvertently omitted which requires the MRO to spend a lot of time and energy conducting our own research in order to accurately determine correct part numbers or task details. We also work with OEMs on temporary revisions to the AMM on issues we see for the first time post modification.”

One example provided by Heier relating to a different modification was the ICA instructions post modification were not clear regarding time-change components. The upgraded engine installed had different time between overhaul and inspection cycles than the original engine, which created a situation where some related components would fall out of sequence with the related maintenance tasks. Again, adding work to the MRO. Heier fully agrees with the importance of thoroughly reviewing and understanding any ICAs when planning the maintenance visit of an aircraft.

Information important for future maintenance

Regardless of where the upgrade is accomplished, having complete, accurate, and understandable technical data from the beginning is a key point. Each modification or upgrade made to an aircraft requires a review of the maintenance program to determine if there is any effect on the related systems or aircraft operation, regardless of how large or small that change may be.

The results of this review just may require some change to the maintenance program or implementation of an ICA in order to maintain that new equipment or system to the same high standard as the rest of the aircraft. Designing and engineering a modification while keeping a maintenance consciousness is an important point for the future maintenance providers of the aircraft.

Aircraft OEMs have invested in extensive parts inventories and dedicated technical support teams to support the airworthiness of the aircraft they build, but that support does not always transfer to heavily modified aircraft unless the OEM sanctioned the upgrade. In addition to upgrade engineering, modification, and ICA quality, parts availability and a highly experienced and dedicated technical support team are critical to maintaining the viability of a major performance upgrade program. If not OEM sanctioned, ensuring that the upgrade provider has invested in these areas in order to maintain the upgrade, and support to the maintenance provider in the future can help ensure that the upgraded aircraft does not become an orphan.

Major performance upgrades can significantly improve an aircraft’s capabilities and lower its operating cost. So, whether replacing an engine or upgrading other integral systems, consider the changes that will apply to maintenance from the manufacturer’s standpoint and from the maintenance facility that has to follow through to guarantee continued airworthiness.

Assistance and information for this article was provided by Randy Znamenak, Hawker Beechcraft Global Customer Support Marketing. He can be reached at (316) 676-3404 or at email