ARP 4754B governs the development assurance of aircraft and systems — how rigorously each function and item must be developed and verified, expressed as a Development Assurance Level. Getting allocation right is both a safety question and a cost question: an over-conservative DAL is expensive, an under-allocated one is a finding.
Top-down allocation that honors the logic
- Apportion the top-event target across gates and down to basic events, respecting gate logic.
- ARP 4754B §5.4 Options 1, 2 and 3 for AND gates, with a carrier-child designation for Option 1.
- External-source linkage so a node can inherit a value from another tree or an FHA target, with free siblings rebalancing automatically to honor the parent budget.
- FDAL (functional) and IDAL (item) designations carried through to the items and configuration items that realize the function.
Tied to the analysis, not a separate spreadsheet
Because DAL allocation runs on the same fault trees you quantify in FTA, a change to the architecture or a failure condition's severity reflows the allocation instead of silently going stale. The DAL Reference view summarizes the DO-178C and DO-254 objective counts by level so the downstream effort is explicit.
From function to item
ARP 4754B is a two-level story: aircraft functions realized by systems, systems realized by items. Safety Lab Aero mirrors that — system functions trace up to aircraft functions, system failure conditions trace up to aircraft failure conditions, and development-assurance allocation stays traceable from the aircraft function down to the line-replaceable unit.
Frequently asked questions
Does Safety Lab Aero support the ARP 4754B §5.4 AND-gate options?
Yes — Options 1, 2 and 3 are supported for AND gates, including a carrier-child designation for Option 1, with siblings rebalancing automatically to honor the parent budget.
What is the difference between FDAL and IDAL?
FDAL is the functional development assurance level assigned to a function; IDAL is the item development assurance level assigned to the hardware or software item that implements it. Safety Lab Aero carries both and keeps them traceable from aircraft function to item.
See it on your own analysis
Safety Lab Aero keeps functions, hazards, fault trees, FMEA, common-cause, requirements and verification in one connected model — from FHA to a certification-ready evidence package.