Do we need a new model for dent evaluation? A commentary.

Is the current model for dent evaluation 'good enough', or does it just follow the limitations of traditional analog and manual measurement tools?

Let's discuss.

But first things first.?

In Pasquale Lafiosca's recently published research paper "Aircraft skin inspections: towards a new model for dent evaluation", he he poses the hypothesis that "the current approach discards any information about the actual shape" and "the current SRM dent representation is ambiguous and insufficient for an objective evaluation of the damage.

?So…what’s the current approach?

Damages like dents on primary aircraft structures are a safety issue. Dents are extremely common during aircraft operations due to ground support vehicles, hail, debris on the runway, etc. Once dents are detected, they need to be measured and qualified. Traditionally, technicians perform measurements with depth gauges, rulers, etc.?

The structural repair manual (SRM) is the primary document containing strict guidelines about assessing and evaluating dent damage. Following the SRM, dents are first qualified by their dimensional characteristics: length, width, and depth. Additional properties like distance to certain aircraft parts, type of material, etc., also play a role.

So far, so good.?

Pasquale now argues that these three geometrical parameters aren't enough to evaluate a dent's structural impact and classify the damage as go/no-go.

Even by fixing the three parameters (length, width, and depth), he argues, you can obtain multiple different dent shapes, even if all those dents would be classified similarly (see illustration below).

In his paper, Pasquale derives another model for dent classification from a mathematical standpoint. He suggests including four additional values --

1. The base: How fast does the depth increase going inward?
2. The egg-factor: How is the dent boundary shaped?
3. Shift of the deepest point along the length
4. Shift of the deepest point along the width

While it is possible to derive these four additional elements from 3D scanning information, obtaining these measurements in the traditional workflow with depth gauges and rulers is impossible.

As 8tree's customer case studies have shown several times, traditional dent measurements with a ruler, flashlight, and depth gauge are error-prone and inaccurate. Pasquale gives another perspective, stating that the three parameters (length, depth, width) the industry uses today to qualify damage are insufficient.

?

Back to the beginning

• Should the industry be limiting itself to traditional analog measurement tools and methods?
• Should the standards be updated to meet the metrology capabilities that we have already made available??
• Or does the aviation industry regard Pasquale’s proposal as a case of ‘technology for the sake of technology, rather than actual industry need'?