OPS 574 Week 2 Process Flow and Bottlenecks Example

Waiting on the Inspector's Stamp: Process Flow and Bottleneck Analysis of a Regional Jet Heavy Check

[Student Name]

University of Phoenix

OPS/574: Creating Value Through Operations

Week 2 Assignment

[Instructor Name]

[Date]

Blue Ridge Regional Airlines, its check process, times and figures are composites written for a model paper.

Week 1 established that the Knoxville maintenance base of Blue Ridge Regional Airlines, a composite regional carrier, loses about $38,000 of value for every day a jet stays in a heavy check beyond plan, and that checks averaged 15.4 days against a 12-day plan. The causes were systemic, not individual. This paper maps how work flows through a check, finds the constraint and proposes changes aimed at it.

The Check From Induction to Release

A heavy check on a regional jet moves through nine stages. Induction: the aircraft is towed in, defueled and prepared. Open-up: technicians remove panels, interior furnishings and access covers, about 600 hours. Inspection: inspectors examine structures, systems and zones, generating findings. Findings and disposition: each finding becomes a non-routine card; minor ones follow standard repairs, while others need an engineering disposition specifying the repair. Parts: materials for routine work are kitted in advance; parts for non-routine repairs are ordered as findings appear. Repairs: technicians perform routine and non-routine tasks. Buy-back: inspectors verify each repair before it can be closed up. Close-up and functional checks: panels are reinstalled and systems tested. Release: records are reviewed and the aircraft is returned to service.

Routine and Non-Routine Work

A typical check contains about 2,900 hours of routine task cards, known before the check begins, and about 1,800 hours of non-routine work generated by findings, averaging about 140 findings per check. Routine work is predictable and can be planned to the hour. Non-routine work is uncertain in amount and timing, and it is where checks run late. Samaranayake and Kiridena (2012) described aircraft maintenance planning as complicated by the unpredictability of work revealed during inspection and proposed integrating planning of tasks, resources and materials to cope with it. The base plans routine work well and treats non-routine work as an afterthought.

Measuring Flow

Time studies on six recent checks recorded what each technician, inspector and engineer did and how long each card waited between steps. Technicians spent about 58 percent of their shift on hands-on work, about 17 percent waiting for buy-back, about 12 percent waiting for engineering dispositions or parts and the rest on paperwork, breaks and movement. Non-routine cards waited an average of 9 hours for an inspector's buy-back and 16 hours for an engineering disposition when one was needed, about a third of cards.

Finding the Constraint

Utilization tells the story. The base has 12 inspectors serving four bays. Inspection and buy-back demand during the peak middle days of a check is about 92 percent of inspector hours available on day shift. The engineering desk of two engineers handles dispositions for all four bays, and its utilization runs about 95 percent. Technicians, by contrast, are about 75 percent utilized on hands-on work. When a resource runs near full utilization and work arrives unevenly, as findings do, queues grow steeply, because work arriving during a busy period must wait. That is why technicians, the largest and most expensive group, stand idle while cards wait.

The base was measuring technicians, but technicians were waiting on the two people at the engineering desk.

The Theory of Constraints

Goldratt and Cox (2004) laid out a five-step cycle: find what limits the system, squeeze the most from it, arrange all other work around it, add capacity to it if needed and, once it is no longer the limit, repeat the cycle on whatever has taken its place. Mabin and Balderstone (2003) reviewed published applications of the theory of constraints and reported substantial improvements in lead times, throughput and inventory in most cases, while noting that the reported cases may favor successes. The steps fit the base's situation.

Exploit: inspectors spend about a fifth of their time on paperwork and walking between bays to find cards ready for buy-back. A dispatcher who batches ready cards by zone and a tablet showing cards awaiting buy-back would free inspector time for inspection. Engineers spend time on findings that fit standard repair manual solutions; a triage rule lets lead technicians apply manual repairs directly for defined findings.

Subordinate: technicians' work is sequenced so that cards needing buy-back reach inspectors evenly through the shift rather than in bursts before breaks.

Elevate: if exploitation is not enough, the base can certify six senior technicians as inspectors for routine buy-backs and add a third engineer during peak months.

Starting Non-Routine Work Earlier

Much non-routine work is predictable in aggregate. Records show that certain zones on aircraft of a given age produce corrosion findings in more than 80 percent of checks. Pre-ordering the most common repair parts and scheduling those zone inspections on day one, rather than when a technician reaches them, moves findings earlier, giving engineering and parts more time. Ayeni et al. (2011) reviewed lean practice in aviation maintenance, repair and overhaul and found growing use of lean methods but noted that the uncertainty of findings and regulatory requirements make the industry's processes harder to stabilize than manufacturing; earlier inspection of high-finding zones addresses that uncertainty directly.

Estimated Effect

Freeing about 15 percent of inspector time and halving engineering queue time, together with earlier inspection of high-finding zones, is estimated to cut average check duration by about 2.2 days. At $38,000 a day across 40 checks, that is worth about $3.3 million a year, against costs of about $400,000 for the dispatcher role, tablets, training for inspector certification and a third engineer in peak months.

What Technicians and Inspectors Said

Time studies explain where time goes; the people involved explain why. Technicians said they often finished a repair and then searched for an inspector, or moved on to another card and forgot to request buy-back, so cards sat closed in practice but open on paper. Inspectors said they were interrupted constantly, rarely able to finish a zone inspection before being called to a buy-back. Engineers said many disposition requests arrived without photographs or measurements, so they had to walk to the aircraft before deciding. Each comment points to a fix in the plan: a dispatcher, protected inspection blocks and a standard disposition request form with photos and measurements attached.

Where the Constraint Will Move

Once inspection and engineering are relieved, the next constraint is likely to be parts availability for unexpected findings, the subject of Week 4, and close-up and functional testing, which must wait for the last repair. The base will repeat the analysis after six checks under the new practices.

Conclusion

A heavy check's 12 planned days stretch to more than 15 not because technicians are slow but because non-routine work waits for two highly utilized resources: inspectors' buy-back and engineering dispositions. Mapping and measuring the process makes this visible, and the theory of constraints provides a sequence of responses, from freeing inspector time to adding capacity. Starting predictable findings earlier reduces uncertainty itself. Together these changes should recover about two of the three lost days.

References

Ayeni, P., Baines, T., Lightfoot, H., & Ball, P. (2011). State-of-the-art of 'Lean' in the aviation maintenance, repair, and overhaul industry. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 225(11), 2108-2123. https://doi.org/10.1177/0954405411407122

Goldratt, E. M., & Cox, J. (2004). The goal: A process of ongoing improvement (3rd ed.). North River Press.

Mabin, V. J., & Balderstone, S. J. (2003). The performance of the theory of constraints methodology: Analysis and discussion of successful TOC applications. International Journal of Operations & Production Management, 23(6), 568-595. https://doi.org/10.1108/01443570310476636

Samaranayake, P., & Kiridena, S. (2012). Aircraft maintenance planning and scheduling: An integrated framework. Journal of Quality in Maintenance Engineering, 18(4), 432-453. https://doi.org/10.1108/13552511211281598