Service Alert

[jdmcbean]

Service Alert

[PapuaPilot]

Thanks John, that's a great reminder.

[Delta Whisky]

A great point, well made.

[Maverick]

So, would adding vortex generators be a change like the memo describes?

[AMK53]

I think he’s referring to airfoil or camber changes and causing changes to lift behavior of the wing. Vortex Generators don’t really change the lift curve all that much.

[PapuaPilot]

I think he’s referring to airfoil or camber changes and causing changes to lift behavior of the wing. Vortex Generators don’t really change the lift curve all that much.

True, that is what the Service Alert addresses, but the underlying issue is a statement that is put in the operating limitations of experimental aircraft. They say something like: After incorporating a major change as described in § 21.93, the aircraft owner is required to reestablish compliance with § 91.319(b) and notify the geographically responsible FSDO of the location of the proposed test area. The aircraft owner must obtain concurrence from the FSDO as to the suitability of the proposed test area.

§ 21.93 Classification of changes in type design.
(a) In addition to changes in type design specified in paragraph (b) of this section, changes in type design are classified as minor and major. A “minor change” is one that has no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product. All other changes are “major changes”.

The real question about vortex generators is "would it be a major change"? Unfortunately the FAA does not define it clearly other than the statement in 21.93, and a Major Change is not the same as a Major/Minor alteration on certified aircraft. But if any change appreciably affects the operation (flight) characteristics it is a major change and the aircraft is required to go back into Phase I flight testing, typically for 5 hours.

All this to say I believe VGs would be a major change. Isn't the goal is to change the flight characteristics of your aircraft? You won't know until you test fly the aircraft. It could be better, worse, no change or downright unsafe. This is the bottom line of the Service Alert that Kitfox just posted.

FYI one of the presenters earlier this week on the EAA Homebuilder's Week said that VGs are a major change. I can't remember who said it, but the statement stuck in my mind because I am considering VGs on my horizontal stab.

[n85ae]

I would imagine the downside of being a manufacturer, is that you get called every time somebody terminates their
existence with your product. So you would be quite inclined to formally say - This is what we designed, it's safe,
don't change it. If you do, you're on your own.

I'm not sure I would ever even consider selling my airplane, simply because I don't want to have anything to do
with what somebody might do with it in the future after it left me.

Pretty obvious watching YouTube video's that a percentage of people flying Kitfoxes are stupid.

Jeff

[Eric Page]

I either read in one of the experimental aviation magazines, or heard in a webinar, that no builder has ever been sued (or was it, "successfully sued?") for an accident by a subsequent owner in an aircraft they built. I don't know the truth of that assertion, but maybe someone else remembers the reference.

[jrevens]

It’s “successfully”, and it’s been stated many times in print. Even if “unsuccessful” you will probably have to spend a fortune to defend yourself if it happens. Having sold an airplane that I built (from “scratch”), I can say that there are ways to drastically minimize the possibility. One of them is not having made structural changes that deviate from the original proven design. The proper legal sales agreement, as well as being very careful about who you sell to are others. Of course we all know that anyone can sue anybody for anything in our world.

[109JB]

I can tell of one where a lawsuit was brought. Wasn't successful but I'm sure it cost the guy a boatload in legal fees anyway. Look up John Denver's Long EZ accident. The original builder, who deviated from the build plans with regard to the fuel selector, was sued, but If I remember right, that suit was eventually dropped. Denver's Long-EZ (check-six.com)