By Robbin Laird
Improving sustainment has been an ongoing major effort throughout the evolution of the tiltrotor enterprise.
The Nacelle Improvement program (NI) is a major milestone in this effort.
When discussing sustainment, an important metric is the mission-capable rate (MC). That rate – expressed as a percentage of total time an aircraft can fly and perform at least one mission – is used to measure of the health and readiness of an aircraft fleet.
The key objectives of the NI program were to improve maintainability and reliability, so as to improve the V-22’s mission-capable rate. A reduction in maintenance man-hours to troubleshoot and repair, coupled with reduced failure rate of components results in less downtime and increased mission-capable status.
I wanted to learn more about industry’s role in the Nacelle Improvement program, so I turned to David Albin, the Nacelle Readiness Program Manager at Bell.
For 20 years, David Albin served on active duty in the Air Force and in the New Mexico Air National Guard as a helicopter and tiltrotor instructor pilot, completing more than 200 combat sorties in the V-22 and rotorcraft.
From my experience with the U.S. Marine Corps in terms of the evolution of maintenance and sustainability, the first years were focused on getting the aircraft deployed to Iraq and Afghanistan and learning how to support it. The focus was on providing parts to ensure mission availability.
As a digital aircraft, the Osprey generated data on parts performance that allowed the Marines to understand better the maintenance profile of the aircraft. By the time it was anchoring the new Special Purpose-MAGTF or SP-MAGTF, Marines could make a reasoned judgment about what parts needed to be onboard the KC-130Js, which were flying with the Osprey on crisis management missions.
By 2015, enough data had been accumulated to focus on how to shape a sustainment enterprise. This enabled the Marines to achieve better mission-capable rates and lower cost per flight hour for the Osprey.
This is where nacelle improvement entered the narrative, as described by Albin:
“When we started the nacelle improvement effort in 2014, we had access to data that allows industry to generate solutions using the fleet’s data. We worked with government on the input from maintainers about the aircraft and looked for solutions to enhance the MC rate and lower cost for flight hour.”
Albin continued, “There are fixed costs and variable costs in working sustainment for an aircraft. We focused on the variable costs and how to reduce them. How do we reduce the demand for components? How many times are parts being ordered based on false positives from the diagnostic system? How do we reduce false positives or get more accurate reporting from the diagnostic system? How do we improve the choke points in maintenance which reduce MC rate, and drive-up cost?”
The focus of the redesign effort was on engineering efforts to improve the operational characteristics of the nacelle.
Albin underscored: “The redesign focused both on service components to reduce the need for in-service repairs, like cracked frame stations, cracked baffles, the hinges and latches were all improved, so that maintainers would have to spend less time dealing with these components and their follow-on effects on the aircraft such as vibration in flight which caused the doors to open and potentially depart the aircraft, for example.”
He continued: “The Reliability & Maintainability Team used the data which had been accumulated from the operational fleet to determine what components or areas on the aircraft needed redesign. Based on this work, the engineers went and did the redesign and the NI program – then delivered reduced maintenance man hour rates and enhanced reliability.”
These combined effects of reduced maintenance man hours & improved reliability are what have holistically resulted in modified aircraft demonstrating higher MC rates compared to aircraft with the prior variant of nacelle.
This approach which yielded the NI program was rooted in two things: (1) a demand side shaped by the maintainers, and (2) the data generated by the aircraft from the operational fleet.
This information then flowed into industry, which then could parse the data and convert the maintainer input into engineering requirements. The engineers then focused on specific, realistic solutions in a re-design precisely focused on a more sustainable aircraft.
The resulting program had four key lines of effort:
- New build of the nacelles;
- Enhanced reuse of repairable components;
- A new wiring design which improved maintainability, reliability and reduced part count;
- New structure, consisting of targeted improvements to address fleet needs.
What has been the result?
According to data through the end of 2023 from the first users of the NI effort, namely the Air Force CV-22 community, the results have been significant. Twenty-one NI modified aircraft have flown 4,065 hours to date. During those flight hours, the maintainability improvements of NI have saved over 10,000 maintenance man hours or over 400 days of maintainer time on the modified aircraft compared to the time that would have spent on the legacy nacelle design.
Based on the NI program objective to improve reliability by four times, the prediction for NI after over 4K flight hours was 140 component failures. The actual failure rate of NI components to date has been zero, which is a truly significant result.
With regard to the NI maintainability rate, the results have also been notable. The objective was to reduce maintenance man hours by 75%, which after 4K flight hours should have accrued 2,195 hours. The actual accrued maintenance man hours on NI components are at 12-man hours to date, which is a remarkable outcome.
As for the MC rate benefit from NI, in October 2023 AFSOC observed a 10.8% MC rate improvement in their NI modified aircraft compared to the legacy nacelle aircraft in their fleet.
Industry predictions are for an overall MC rate improvement of 7% or higher for the CV-22 fleet once all 50 aircraft in the Air Force fleet are modified.
To data leads to one conclusion: The NI program is a significant step forward in shaping a more sustainable tiltrotor enterprise. The benefits to the fleet from improved maintainability, reliability and overall MC rate are certain to provide great benefit in the austere and distributed operations employment of the aircraft in the future.
The featured photo shows Albin in his military role as a CV-22 pilot.
See also the following:
Osprey Major Redesign Effort: Modified CV-22s Arrive at Cannon Air Force Base