Engine Upgrades on Non-Standard Airframes in Canada

Understanding the Serialized STC (sSTC) Pathway and Avoiding Costly Pitfalls

Upgrading an aircraft engine is often seen as straightforward when a well-known STC already exists. But what happens when the airframe or engine combination is not easily found in the usual approval lists?

In Canada, these upgrades are still very much possible, but the approval pathway has evolved. Understanding that pathway before any work begins can save owners thousands of dollars, months of delays, and significant frustration.

This article outlines the current best practice for engine upgrades on non-standard airframes, based on real-world experience.

The Old Model vs the Current Reality

For many years, owners and shops relied on LSTCs (Limited Supplemental Type Certificates) to approve modifications on a case-by-case basis.

That process is now obsolete.

Today, Transport Canada issues serialized STCs (sSTCs). These approvals are:

Issued for one specific aircraft
Tied directly to the aircraft serial number
Based on a documented engineering evaluation

Understanding this shift is essential. Many delays and rejected projects still happen because people unknowingly follow outdated LSTC-era assumptions.

The Key Player: The Design Approval Representative (DAR)

The most important figure in a non-standard engine upgrade is not the maintenance shop. It is the Design Approval Representative (DAR).

Transport Canada maintains an official list of DARs who are authorized to:

Research the technical feasibility of a proposed modification
Evaluate regulatory compliance for a specific airframe
Submit findings to Transport Canada for verification
Support the issuance of a serialized STC

Critical rule:

A DAR must be consulted before any modification work begins.

If physical changes are made first, the project may later be deemed non-compliant, regardless of how well the work was performed.

Why Choosing the Right DAR Matters

Not all DARs operate with the same efficiency, experience, or cost structure.

In practice, estimates for similar projects can range dramatically. It is not uncommon to see quotes from $3,500 to over $20,000 for comparable evaluations.

The difference often comes down to:

Familiarity with the aircraft type
Experience navigating TC expectations
Practical understanding of engine and airframe history

A well-chosen DAR can deliver:

A faster approval timeline
Lower overall cost
Clear guidance before work begins

Many owners find the best results by selecting a DAR recommended directly by a Transport Canada regional office.

The Role of Owner Associations and Type Clubs

Aircraft owner clubs and type associations can be an excellent resource. Most General Aviation types have active communities with valuable historical and technical knowledge.

For example, organizations like the Beech Aero Club often provide insight into how similar upgrades were successfully approved.

That said, many contributors may still reference older LSTC-based processes. Their experience is helpful, but it should always be validated against the current sSTC framework.

A Practical Summary for Aircraft Owners

If you are considering an engine upgrade that is not already covered by a readily available STC, the safest approach is:

Consult a DAR first, before committing to any modification
Confirm whether the upgrade is feasible for your specific airframe
Obtain a serialized STC approval path
Proceed with physical work only once regulatory feasibility is confirmed

Following this sequence dramatically reduces risk and uncertainty.

Final Thoughts

Engine upgrades outside standard STC listings are not unusual, and they are not inherently difficult. The process simply requires the right order of operations and the right expertise early on.

In many cases, success comes down to planning before doing.

Owners who take the time to understand the sSTC pathway and engage the right professionals from the outset tend to experience smoother approvals, predictable costs, and faster timelines.