Store drawing

A part reference can carry the drawing of the store it designates. An aircraft’s underside plan then shows its actual silhouette, at its position and at its true size, instead of the generic shape derived from its dimensions. The “Store drawing” block lives on the part record (Part catalogue).

This block only appears on references of the Store type — missile, drop tank, pod. An oil or a wheel has no silhouette to overlay on the plan, and the API refuses to attach a drawing to one. The type is set under Part types, where the “Store” box tells it apart from an ordinary spare.

Nothing is required, and that is deliberate

The plan never depends on a file. It degrades through three levels, from richest to plainest, and each one states honestly what it knows:

What the plan draws, according to what it knows

Calibrated drawing — the real silhouette
The reference carries a drawing AND its calibration: the store is drawn as it is, scaled to its published length, aligned with the aircraft axis.
Dimensions only — a shape at true scale
No drawing, but a length and a width on record: the store is represented by a plain shape at exact dimensions. The view says “an object of this size, at this place”, which is enough to judge clearance.
Neither — a marker, and the fact is written down
A plain marker shows the station, and the plan STATES beneath the image which references are in that case. Never an invented size, never a silent absence.

Why two points, and not the file’s frame

Drawing calibration: Two points clicked by hand on the image: the store’s nose tip and its tail end, in file pixels. The distance between them equals the reference’s published length, which yields the scale; their direction yields the orientation.

The file’s frame says nothing usable. A store drawing arrives with transparent margins of arbitrary width, in an arbitrary orientation — nose right, nose left, nose up — and at an arbitrary resolution. Nothing in the file states where the object begins and ends. Scaling the image on its bounding box would draw the store too short and too thick, in a proportion that depends on how whoever exported the file happened to crop it.

This is exactly the same stance as calibrating an aircraft’s underside view, and for the same reason: two points remain readable and correctable a year later, where a pre-computed matrix would be unverifiable.

The projection is recorded, because a side view is not an underside view

On saving, you declare whether the drawing is a side view or an underside view. This is not a decorative label: it is what decides the treatment.

A cruciform store — four fins at right angles — does not present the same thing from both directions: seen from the side, two fins appear full-size and two edge-on; seen from below, it is the reverse. On a body of revolution the silhouette therefore stays very close, and a side view is an acceptable approximation. What a side view will never show are the details that exist on one side only — the suspension lugs, for instance, which sit on top and would be hidden by the body when seen from below.

The screen says so rather than keeping quiet: the tooltip of a store drawn from the side announces an “approximate projection”.

Pair symmetry, and the guard that comes with it

A side view has a top and a bottom. Aligned nose-forward, that top would always fall on the same side: two missiles carried on the left and right wings would lean the same way instead of mirroring each other. The plan therefore flips the drawing on one side, restoring a pair’s visual symmetry.

That flip never applies to a genuine underside view. Mirroring a drawing that tells the truth would swap port and starboard with nothing to signal it — the same invisible error as a flipped aircraft underside calibration. Declaring the projection honestly is what protects against that trap.

Replacing the drawing clears the calibration

The two points are pixels of the file they were clicked on. Changing the drawing therefore voids them mechanically, and the calibration is cleared: the assistant returns to its first click. This is not excessive caution — a drawing replaced by another with different cropping would otherwise leave a calibration that looks valid and draw the store at the wrong size, without a word.

A caller who supplies the drawing AND its calibration in the same gesture is honoured: that is the case of a retouch which rigorously preserves the geometry.

The whole is carried by PATCH/part-numbers/:id — which carries the drawing (drawingDocumentId) and its calibration (drawingCalibration).

A cross-instance limitation worth knowing

A part reference is not partitioned by instance — the catalogue is shared — whereas a document is. The attached drawing therefore lives in the document space of the instance that uploaded it, and another instance will not obtain the file. The plan then falls back to the shape derived from the dimensions: degradation stays clean, but the drawing remains invisible to it.