Aerostructures: work packages, jigs and the problem of very large parts

A work package award commits a decade of capacity

Winning a section of an aircraft resembles a joint venture more than a sale. The supplier commits floor space, tooling and engineering for the programme's duration, prices a recurring cost expected to fall over time, and accepts responsibility for feeding the integrator's final assembly sequence. Because the section is unique to that aircraft, the assets have no alternative use, and exit is practically impossible without surrendering design data and tools. Bidders modelling only the recurring margin miss the point: an award's value depends on the rate actually achieved, on escalation terms, and on who pays when the integrator changes the design.

Assembly jigs define the factory footprint

Large structural assemblies are built inside jigs holding interfaces to tolerance while parts are drilled, shimmed and fastened. Those jigs are huge, costly, slow to build and effectively immovable, so the number of jig positions sets maximum rate long before labour does. Adding rate means adding a jig, which means adding building, which means a capital case and a construction programme. Aerostructures capacity therefore expands in visible steps rather than smoothly, and an integrator requesting a modest rate increase can trigger a disproportionate investment argument at a supplier with no spare position.

Composite and metallic routes are different businesses

Metallic structure is machined, formed, chemically processed and mechanically fastened, with scrap recoverable and rework often possible. Composite structure is laid up, cured and inspected, with material carrying limited shelf and out-time, cure capacity as a hard constraint, and defects that resist repair and sometimes visual detection. The two demand different engineering skills, different quality methods and different capital. Suppliers running both usually keep them in separate halls with separate teams. Buyers comparing quotations should note that the composite route shifts cost away from labour and towards material, energy and inspection.

Moving the product is itself a production constraint

A completed wing or fuselage section cannot simply be palletised. Movement to the integrator may require oversized road convoys, purpose-built barges, dedicated freighter aircraft or a rail path with clearance surveys, and each imposes schedule and packaging requirements back onto the factory. Protective transport fixtures are engineered items in their own right, needing storage and return logistics. Site selection follows: these plants cluster near ports, airfields or navigable water for good reason. Damage in transit is also a real loss event, since a scratch on a cured skin may need an engineering disposition before acceptance.

Risk-sharing terms decide who absorbs a rate cut

Contracts here allocate development cost, tooling ownership, escalation and rate variation, and those clauses matter more than the headline price. A risk-sharing arrangement usually means the supplier funds part of development in exchange for programme content, betting on delivered volume. If the integrator cuts rate, the supplier carries underabsorbed overhead against a recurring price set for higher output. Well-negotiated agreements contain rate bands with price steps, notice periods for changes and compensation for tooling left idle. Suppliers lacking those protections find that a programme delay transfers almost entirely onto their own balance sheet.

Frequently asked questions

Why are aerostructures suppliers so exposed to a single programme?

Because tooling, jigs, facility layout and trained labour are specific to one aircraft section. There is no secondary market for a fuselage assembly jig, and the design data belongs to the integrator. A supplier holding one major package therefore has its utilisation, cash flow and workforce plan tied to decisions taken elsewhere. Diversification is possible but slow, since a second package means competing for an award that may only appear when a new aircraft is launched.

What limits how fast an aerostructures plant can raise rate?

Jig positions bind first, then cure capacity if the structure is composite, then skilled labour, then long-lead material. Each has a different lead time, and the binding constraint moves as rate rises. Because a jig takes a long time to design, build and qualify, rate increases must be committed well before demand is certain. Suppliers therefore push for firm rate commitments or capacity reservation payments instead of accepting an integrator's forecast at face value.

Is composite structure cheaper to produce than metallic structure?

Not usually in acquisition cost. The material is expensive, cure cycles consume energy and time, inspection is more demanding, and repair procedures are stricter. The case for composite rests on weight, fatigue behaviour and the ability to form large integrated shapes with fewer joints and fasteners. In factory economics terms, the composite route substitutes material and energy for assembly labour, and makes the plant more sensitive to cure capacity than to headcount.