Allocation fails socially more often than it fails mathematically: the arithmetic is too simple to break, but the judgements around it bend under programme pressure. Every entry below is a pattern seen on real programmes; the guards are correspondingly procedural.
| Pitfall | What it looks like | The guard |
|---|---|---|
| Equal apportionment that never dies | The day-one placeholder split still governing budgets at CDR | Flag equal splits as provisional with an expiry milestone |
| Budgets where there is no design freedom | A COTS unit allocated twice what its vendor has ever demonstrated | Cap COTS budgets at evidence; escalate the shortfall, don't bury it |
| Series arithmetic across redundancy | Redundant channels summed as if independent series elements | Budget the redundant group as one element; its internals belong to the RBD |
| Ratings without ground rules | FOO scores drifting toward whoever argued loudest | Written criteria per factor, independent scoring, archived rationale |
| ARINC over a stale prediction | Last year's estimates scaled into this year's contracts | Re-run the prediction first; date-stamp the weights |
| Unit and clock mismatch | Budgets in FIT against predictions in f/10⁶ h, or different mission times | One declaration of unit, clock and mission time, shared with prediction |
| Structure edits outside the budget | Elements added after the split, carrying no allocation | Conservation check (Σ children = parent) after every structure change |
| Allocation as decree | Budgets issued without feasibility checks, absorbed as fiction by the teams | Every budget line held against similar-equipment or vendor evidence |
| No reserve | The first surprise reopens every sibling's contractual target | Allocate tighter than the requirement; hold the difference as reserve |
| Target mistaken for achievement | Allocated MTBF columns quoted as if they were predictions | Keep the allocated-vs-predicted view current; never report one without the other |
Two of these deserve a closing sentence each. The decree failure is the deepest: an allocation that was never negotiated against feasibility does not distribute a requirement; it distributes disbelief, and every team quietly reverts to designing to what it thinks is possible while the budget table becomes ceremonial. And the static-budget disease is the slowest: an allocation is a snapshot of a negotiation, and a snapshot left unrevised while the design, the predictions and the structure all move ends up describing a programme that no longer exists. The fix for both is the same habit: treat the allocation as a living contract, re-opened deliberately, on evidence, at every milestone that changes what anyone knows.