A defense prime contracts to deliver a next-generation radar system by a fixed contractual date, with liquidated-damages penalties for every day late. The delivery schedule threads through multi-tier procurement, long-lead component manufacture, international transport and customs, assembly, integration and acceptance trials. The contract negotiation turns on one number: how many days of buffer the prime must hold to deliver with confidence. Tamara, Vose Software's project schedule and cost risk tool, runs the whole programme as a Monte-Carlo simulation and turns that number into a decision table.
The contingency ladder is the headline. It reads as a decision table: how many days beyond the 930-day deterministic plan (from the 1 June 2026 contract start) each delivery-confidence level requires. Committing to a date the prime can hit half the time costs +129 days of buffer (delivery day 1059). P70 confidence costs +228 days, and both P80 and P90 sit at +272 days (delivery day 1202) - a flat step that tells the prime the jump from 80% to 90% confidence is almost free once the buffer is bought. Squeezing out the last tail to P95 costs +309 days. A negotiator can read the price of each confidence level straight off the bars instead of arguing over a single optimistic date.
Each activity duration is modelled with a Beta-PERT distribution, and six discrete supply-chain risk events - supplier slips, manufacturing bottlenecks, transport and customs disruption - add delay to specific tasks. The deterministic plan assumes every supplier delivers on its most-likely lead time and nothing disrupts transport; across 60,000 simulated programmes that holds only 5% of the time.
The S-curve restates the ladder as a continuous probability curve. The deterministic 930-day plan has only a 5% chance of being met; the P50 delivery slips 129 days past the plan and the P90 reaches 272 days late - well into liquidated-damages territory.
The schedule tornado ranks each activity by the correlation (cruciality) between its duration and the delivery date. The long-lead transmitter array (0.50), system integration & test (0.39), and electronics integration (0.36) top the chart - the activities where a swing in duration most reliably moves the delivery date, and where dual-sourcing or expediting buys the most schedule certainty.
Schedule risk is cost risk: every day late carries extended programme overhead plus liquidated-damages penalties. Before mitigation the programme costs a mean of $96M with a P90 of $108M and a 31% chance of breaching the $104M budget. A supply-chain mitigation package - dual-sourcing the transmitter array and Tier-1 components, expedited transport, a pre-qualified Tier-2 second vendor - shifts the distribution left to a mean of $92M, a P90 of $101M, cuts the overrun probability to 14%, and lifts on-time-delivery probability from 5% to 51%.
The Pareto chart isolates the six supply-chain risk events and ranks them by expected schedule impact - probability times average delay, in weeks. The transmitter-array supplier slip (6.0 weeks), transport/customs disruption (4.6 weeks), and Tier-1 manufacturing bottleneck (4.2 weeks) lead; the top four events carry roughly 80% of the total discrete-risk delay exposure. That ranking is the prime's supply-chain mitigation priority list.
The combined picture - a ladder that prices each confidence level, a 5% chance of on-time delivery, and a clear ranking of which suppliers set the date - lets the prime negotiate realistic delivery terms, justify dual-sourcing investment, and price liquidated-damages exposure before signing.
This article is part of our Tamara case study series. Contact us to discuss how Tamara can quantify schedule and cost risk on your programmes.