Aircraft Line Maintenance Scheduling Optimization / by Hatem Mohamed Abdelaty Attia ; Under the Supervision of Prof. Dr.Gamal Mahmoud Sayed El-Bayoumi, Dr.Mohannad Ahmed Draz.

Thesis (M.Sc.)-Cairo University, 2023.

Bibliography: pages 61-64.

Due to the emergence of advanced aircraft and new technology, many of the maintenance
tasks conducted on an aircraft can now be considered line maintenance tasks, i.e., they can be
executed during layover periods between flights and without the need for hangar space. This
flexibility gives rise to the opportunity of using appropriate optimization techniques to replace
the task grouping-based maintenance scheduling technique that is manually and traditionally
used by airlines with a more efficient individual task-based scheduling concept. This thesis
studies the Line Maintenance Scheduling Problem (LMSP) and provides a compact and
efficient mathematical optimization model describing several realistic conditions for the
problem along with two tested solution methods, an exact linear programming method, and a
fast approximate heuristic method. The LMSP aims to determine the best starting time for every
single line maintenance task so that their finish times are as close to the task's due times as
possible, minimizing the total deviation of tasks submission time from the due dates and
making the most of the aircraft components' lifetime, which subsequently reduces the overall
number of repairs and saves maintenance costs.
A practical schedule should ensure that at any moment in time, the number of resources
required by tasks does not exceed the time-dependent resource supply of the airport. Other
realistic constraints were applied to the LMSP, such as precedence constraints ensuring that
tasks are performed in the correct order and deadline, and release time constraints ensuring that
tasks start and finish sometime between their release time and deadline. Several simulated
airline scenarios and instances were designed to test the performance of both solution methods
showing that both methods are applicable under realistic conditions. The heuristic approach is
nearly 7.5 times faster than the exact approach but at the expense of a 6% deviated sub-optimal
solution from the actual globally optimal solution generated by the exact Mixed-integer Linear
Programming approach. The exact approach was able to find the optimal schedule for each
instance within an hour on average. One of the instances was further studied, showing a
reduction of around 10% in service time of maintenance tasks leading to nearly $30 million of
annual maintenance savings. Furthermore, the effect of the level of congestion in the system
was investigated to understand the effect of adding more maintenance stations and more
resources in airports on the maintenance cost of a schedule. The analysis showed that it is far
more advantageous to add more maintenance stations than to add extra resources to supply
each of the existing maintenance stations.

مع ظهور وانتشار الطائرات ذات التكنولوجيا المتقدمة والحديثة ومع التطورات في مجال صيانة الطائرات، كثرت الآن مهام الصيانة التي يمكن تنفيذها خلال فترات التوقف بين الرحلات ودون الحاجة إلى مساحة الورشة وحظيرة صيانة الطائرات. يعرف هذا النوع من مهام صيانة الطائرات بمهام الخط لكونها تُنفذ أثناء انتظار الطائرة في طابور الإقلاع. تمنح هذه المرونة فرصة لاستخدام خوارزميات التحسين المناسبة وعلم بحوث العمليــاتبهدف استبدال طريقة جدولة الصيانة التي تعتمد على تجميع المهام والتي يتم استخدامها يدويا وبشكل تقليدي من قبل شركات الطيران بتقنية جدولة المهام الفردية الأكثر كفاءة. تدرس هذه الرسالة مسألة الجدولة المثلى لصيانة الخط (LMSP) وتوفر نموذجًرياضيًفعال وموجزاً للمسألة يصف العديد من الظروف الواقعية في صيانة الطائرات بالإضافة إلى طريقتي حل تم اختبارهما، وهما طريقة برمجة خطية دقيقة وطريقة تقريبية سريعة. مسألة الجدولة المثلى لمهام صيانة الطائرات (LMSP) تهدف إلى تحديد أفضل وقت بدء لكل مهمة صيانة على حدة بحيث يكون وقتالانتهاء من المهام قريب على قدر الإمكان من الأوقات المحددةلانتهاء المهام، وذلك لتقليل الانحراف الإجمالي والاستفادة القصوى من عمر مكونات الطائرة، مما يقلل بشكل كبير من عدد الإصلاحات العامة ويوفر تكاليف الصيانة.

Issued also as CD

Text in English and abstract in Arabic & English.