To do critical path analysis for an aircraft maintenance assignment, list each task with its single-person hours and predecessors, run a forward and a backward pass to find earliest and latest times, then mark every activity with zero total float as critical. Next draw the bar chart and resources diagram from those times, and only then test how extra people shorten the job.
You have a landing gear replacement split into fourteen lettered tasks, a spreadsheet template that wants a network diagram pasted into Word, and a brief that also asks about outsourcing and A320 checks. The network is where most of the marks sit, and it is also where one early slip carries through every later table. This guide follows the order in which a Kingston AE6005-style report is actually marked. You can see a worked example in our AE6005 landing gear network analysis sample, which is for reference only, and the original wording on the AE6005 question page.
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Start with the network, and use the hours exactly as given
The brief says to use single-person hours, not hours divided by the maximum crew. That is an instruction, not a hint. If you divide by crew size at this stage, your durations, floats and critical path all come out wrong, and the marks for correct floats go with them.
Build a table first: activity, description, hours, maximum people, predecessors. Then draw the action-on-node diagram, with each node showing ES, EF, LS, LF and the activity letter. A clean node layout is worth more than a pretty one, because the marker is checking numbers, not artwork.
Forward pass, then backward pass
The forward pass takes the largest EF of the predecessors as the next ES. Where an activity has several predecessors (the installation task in this kind of case has three), the latest finisher decides. The backward pass starts from the final EF and takes the smallest LS of the successors as each LF. Total float is LS minus ES.
| Term | How to calculate it | Common slip |
|---|---|---|
| Earliest start (ES) | Largest EF among predecessors | Using the first predecessor, not the latest |
| Latest finish (LF) | Smallest LS among successors | Using the largest, which inflates float |
| Total float (TF) | LS − ES (or LF − EF) | Quoting free float in the TF column |
| Free float (FF) | Earliest next ES − this EF | Giving free float to activities whose successor starts immediately |
| Critical path | Activities with TF = 0 | Forgetting a second path with zero float |
In the landing gear case the critical activities form a single chain covering preparation, jacking, removal, inspection, installation, servicing checks, independent checks and release. Check for a second zero-float route before you say there is one path. Here there is not, but other networks have parallel critical paths.
Floats: the part students get wrong most often
Most students calculate total float correctly and lose marks on free float. Free float is only non-zero when an activity can slip without moving even its successor’s earliest start. Two activities on the same non-critical branch can have identical total float yet only the last one on the branch carries free float. Draw the branch out and the reason is obvious.
When you mark the diagram, show free float at the right-hand end of the bar on the chart, as the guidance in the brief asks. Leave nothing floating at the start of a bar or between tasks.
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Turn the numbers into a bar chart and a resources diagram
The bar chart is the same data on a time axis. Put critical activities in one continuous row, then arrange the others so each starts at its ES. The brief allows two bars on one row if there is a gap between them, which saves space and keeps the page tidy in Word.
For the resources diagram, count people per hour. At earliest start with one person per task, a landing gear case like this peaks at three people early and then runs on one for long stretches. Say so in words: name the peak, state the hours it lasts, and comment on what it means for staffing. Total person-hours is a useful sanity check. If your resource profile does not add up to the sum of the task hours, something has been drawn wrongly.
Resource levelling in one sentence
Levelling means moving non-critical work within its float to smooth the demand without lengthening the project. In this assignment you do not need new diagrams for the reduction question, but you should be able to describe the moves in words.
Reducing duration with a limit on people
Reducing overall duration means shortening critical activities. Shortening anything else only uses up float. Add people to each critical task up to its stated maximum, and duration becomes hours divided by crew. Tasks capped at one person cannot be shortened and become the new bottleneck.
Then check the crew count hour by hour against the limit. If the maximum crews on parallel tasks exceed the limit, use the float to delay non-critical tasks until people are free. Often the limit costs nothing, because the work that would clash is the work with float. For the illustrative case set in this brief, a four-person cap still allows the critical path to fall from 20 hours to 12 hours. Test your own numbers; do not copy ours without checking, because small differences in precedence change the answer.
State whether the critical path changes. The sequence may stay the same while the float on the near-critical branch shrinks to almost nothing. That is the point a marker wants to see: the path is unchanged, but the schedule has become more fragile.
Comparing in-house and outsourced maintenance
With a 300-word limit you cannot cover everything, so choose four criteria and compare each directly. Mix cost, control, capability and risk, and give a verdict at the end.
| Criterion | In-house | Outsourced |
|---|---|---|
| Cost | Large fixed investment | Variable cost, provider margin |
| Control | Direct oversight of priorities | Dependent on contract and audit |
| Capacity | Limited by own hangar | Bought in when needed |
| Risk | Skills retention, idle assets | Dependence, records interface |
Anchor it in regulation. A maintenance organisation holds a Part-145 approval, and airworthiness management is covered by separate arrangements, which is why outsourcing does not remove the operator’s responsibility (UK legislation, 2014). Kinnison and Siddiqui (2013) give you a textbook framework for the management side.
A320 base maintenance checks without inventing numbers
The question asks about primary types of base checks on the A320 family in about 500 words. Describe the C-check as a hangar visit with detailed inspection and rectification, and the heavy structural check as the deepest. Say that the A-check is usually overnight line work and sits outside base maintenance, but mention it for contrast.
Treat intervals carefully. Airbus publishes a Maintenance Planning Document that is not itself a controlling document, and each operator builds an approved programme from it (Fehrm, 2024). Any figure you quote should be labelled as indicative and dated to a revision. One published example puts the A-check cluster at 750 flight hours, 750 cycles or six months for one MPD revision, but intervals have since lengthened (Fehrm, 2024). A made-up number is a worse risk than a missing one.
Mark-maximising checklist
- Hours used as given, not divided by crew, in Q1.
- Forward and backward pass shown, with ES, EF, LS, LF in each node.
- Total float and free float in separate columns.
- Critical path stated in letters and in hours.
- Bar chart with free float at the right-hand end of bars only.
- Resource peak named, with its hours and its cause.
- Reduction answer states the new duration and whether the path changed.
- Word counts stated and within 10% for Q3 and Q4.
- Harvard references and the generative AI acknowledgement included.
Common mistakes
- Dividing hours by crew size in the first question.
- Calling a near-critical path critical, or missing a second critical path.
- Giving free float to every non-critical task.
- Drawing the resource chart from the reduced schedule rather than the original.
- Writing a general essay on outsourcing with no link to aircraft maintenance regulation.
- Quoting A320 check intervals from a forum with no source.
Most students find that the network is quick once they have a clean table, and that the writing, within 800 words, is what takes time. Do not leave it to the night before your deadline.
Frequently asked questions
Do I divide task hours by the number of people in the network diagram?
No. The brief asks you to use single-person hours for the network, floats and critical path. Crew size matters only later, in the reduction question, where hours divided by people give the shorter durations.
How do I tell total float from free float?
Total float is how long an activity can slip without delaying the project. Free float is how long it can slip without delaying the next activity’s earliest start. Free float can never exceed total float, and is often smaller.
Can there be more than one critical path?
Yes. Any chain of activities with zero total float is critical, so parallel routes of equal length are both critical. Check every route into the joining activity before stating a single path.
Does adding people always shorten the project?
No. It only helps on critical activities with a maximum crew above one. A one-person task cannot be shortened this way, and adding people to non-critical work saves nothing.
How should I treat A320 maintenance check intervals?
Give them as indicative, cite a dated source and say that each operator’s approved programme may differ from the manufacturer’s planning document. Avoid presenting any single figure as fixed for all operators.
Can I submit a sample answer as my own work?
No. Samples are for reference and study only. Your institution expects your own analysis, and this brief requires an acknowledgement of generative AI contribution. Use a sample to check your method.
Our aerospace engineering assignment help and engineering assignment help pages explain the support available, and you can read student reviews first. When you are ready, send your brief and we will respond with a quote.
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About the expert
This guide was reviewed by James Whitfield, who holds an MEng in Mechanical Engineering from the University of Sheffield and has 15 years’ experience, with a focus on mechanical systems.
References
- Fehrm, B. (2024) ‘Bjorn’s Corner: New aircraft technologies. Part 48. Maintenance Program for the A320/A321’, Leeham News, 1 March. Available at: https://leehamnews.com/2024/03/01/bjorn-s-corner-new-aircraft-technologies-part-48-maintenance-program-for-the-a320-a321/ (Accessed: 22 October 2026).
- Kinnison, H.A. and Siddiqui, T. (2013) Aviation maintenance management. 2nd edn. New York: McGraw-Hill. Available at: https://www.mheducation.com/highered/mhp/product/aviation-maintenance-management-second-edition.html (Accessed: 22 October 2026).
- Lock, D. (2013) Project management. 10th edn. Abingdon: Routledge. Available at: https://www.routledge.com/Project-Management/Lock-Lock/p/book/9781409452690 (Accessed: 22 October 2026).
- UK legislation (2014) Commission Regulation (EU) No 1321/2014 on the continuing airworthiness of aircraft and aeronautical products, parts and appliances, and on the approval of organisations and personnel involved in these tasks, Article 4. Available at: https://www.legislation.gov.uk/eur/2014/1321/article/4/data.htm?view=plain (Accessed: 22 October 2026).
- European Union Aviation Safety Agency (n.d.) Aircraft maintenance and continuing airworthiness (FAQ). Available at: https://www.easa.europa.eu/en/node/121041 (Accessed: 22 October 2026).