Propulsion and power

This is the parent guide for everything that makes power on an aircraft: turbine and piston engines, electric and hybrid propulsion, propellers, auxiliary power units, electrical generation and distribution, batteries and fuel systems. The guides beneath it are where a buyer with a part number should go. This one is about the thing those guides share, which is that propulsion is approved in layers, and the layer decides who answers when something has to change.

Three approval paths, three kinds of supplier

An engine is a product with its own type certificate, and Part 33 prescribes the standards for issuing it, together with the emissions requirements of Part 34 that an applicant must also meet.¹ A propeller is a separate product with its own type certificate under Part 35, which also requires instructions for continued airworthiness and identifies propeller critical parts, the ones whose failure the design must be engineered against.² Most of the rest arrives as articles. A technical standard order is a minimum performance standard for a specified article, a TSO authorisation is a design and production approval issued to the manufacturer that meets it, and holding one is not an approval to install the article on an aircraft.³ When a supplier says its unit is approved, that sentence has three possible meanings, and you want the one that matches the aircraft you are putting it on.

What a buyer decides

Ratings first. An engine's power or thrust ratings and its operating limitations are part of what was certificated, so a rating you buy is a certificated rating and not a marketing figure.¹ Then the life of the thing: ask for the published life-limited part list, the current lives, and the cost of a set at the first shop visit. Ask what the instructions for continued airworthiness require and how often the manufacturer revises them, because the revision is the mechanism by which your cost per hour changes without anybody selling you anything.¹ Ask what the overhaul interval is, whether it is hard time or on condition, and what the last three published field campaigns cost operators. For electrical power and energy storage, ask the same questions in the same order, and add the qualification test evidence for the environment the unit will live in.

Support is bought with the hardware

A repair station's ratings tell you what it may work on, and the powerplant classes are explicit: reciprocating engines of 400 horsepower or less, reciprocating engines above that, and turbine engines, with propeller work rated separately.⁴ Ask where in the world the approved shops are, which of them are the manufacturer's own, what a spare engine or a lease pool costs when yours is in the shop, and how long a standard exchange takes. An engine deal is really a maintenance agreement with hardware attached, and the agreement should be read that way.

Where the public record can be checked

The FAA publishes its design approvals, and engine and propeller type certificates, parts manufacturer approvals and technical standard order authorisations are all searchable.⁵ That record proves the approval exists, who holds it and what it covers. It does not prove in-service reliability, and it does not tell you what an operator pays per hour. Those numbers come from operators, and they will usually tell you.

The companies below are listed on public facts, each with its source linked.