To start, I'd like to state clearly that this is not a single-vendor situation or concern. Everything below applies in a general sense. It just so happens that this thread is the one where discussion is currently taking place around what is importantly a more-general topic.
Over time we've seen a number of changes from a variety of sources to portions of the RV airplane designs that carry higher levels of risk - and that's what's predicated publication of the service letter that's linked below.
We've published a letter (
SL-00062) warning builders/owners/operators about the potential risks associated with untested design changes to RV aircraft. Whether making a single change or a set of cumulative/additive changes, in the interest of safety we want to ensure that people understand and accept the risks associated with their departures from the kit plans. Some aircraft structure/systems changes inherently carry greater risk than others, and it's important that people understand and think about their planned changes in context.
That said: the Experimental Amateur-Built category certainly allows builders and owners to experiment and make changes that vary from the kit aircraft design, and in some way each aircraft is unique. When ordering parts from Van's Aircraft or other parties and using them in a manner for which they were not intended by the company's design, we want to make sure the customer understands clearly that fact any modifications they plan have not been evaluated or tested by Van's and that by selling parts to a customer we can't and don't review or approve of their use. In other words, the person making the modifications is on their own and should be certain they understand the risks and impacts on various important elements of design such as stresses, structure, operational systems, etc.
Generally speaking, as we've observed both kit builders and owners of flying aircraft making significant changes, at times we've noticed people making combinations of changes which prompted us to question whether the person making changes had thought about the overall impact to risk and safety. It's this class of concern that leads us to publish the below-linked letter in an attempt to communicate information to customers. We're not saying "no," but we are communicating information that we deem important - especially when our parts and materials are used in customizations.
Broadly, and this is not a complete list by any means, here are a few of the general categories of potentially riskier changes that come up from time to time:
- Changes that potentially impact the structural integrity of the airframe (overstress structural failure, long term fatigue)
- Changes that modify critical systems for which a failure is considered especially critical (fuel, electrical, controls, ignition, etc.)
- Changes that impact weight, balance, loading, and stresses imposed on the airframe
- Other changes that affect aerodynamics and handling (performance, stability, spin resistance, flutter etc.)
- Changes that result in the aircraft operating beyond the design limits and into the engineering safety margin
While some might read this and thing that Van's has jumped on the legal bandwagon, that's really not our purpose here. Our common interest and concern is safe and fun flying, and that's what we're all about. In general, we've always stressed safety in the design, building, maintenance, and operation of RV aircraft and our intent here is simply to ensure everyone thinks about and accepts any risks and is aware of the fact that Van's cannot determine the relative risk or safety of something we don't produce. Therefore it's important for people to analyze and consider their specific risk situations.
Link to:
SL-00062
Where applicable, we will include a copy of the letter in shipments of our parts to customers to help prompt proper customization analysis, and we plan to communicate important concerns and things to consider in future articles concerning modifications, as well.
Thanks everyone.