10/23 Raptor Video

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Marc Zeitlin

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I didn't suggest he was doing any flutter testing. Only that it didn't spontaneous flutter at that new speed as far as we know.
You're correct - it didn't flutter on it's own (as far as we know). But "didn't flutter" and "is flutter resistant" are two different things, because what happens without an excitation is not necessarily and indication of what will happen with an excitation.

Might have vibrated or something but we don't know details anymore without the video reports.
Each speed increase increment has some technical value.
Agreed - speed increase increments have some technical value, but only if flutter TESTING is performed at each increment. Unless an excitation of the control surfaces is provided, merely going faster isn't necessarily telling you anything useful.

Is there any public disclosure of flutter testing in the EA-B plans or kit industry?
Not sure what you mean here. AN90-89B discusses flutter and it's causes and prevention fairly extensively, but it does NOT discuss flutter testing.

However, the COZY (and IIRC, the Varieze and Long-EZ) POH's DO have a section on "Flutter Envelope Expansion", in which they explicitly discuss how to conduct speed expansion and stick raps. It incorrectly indicates that one should only test up to Vne, not to Vd, but that's a relatively minor nit considering that many E-AB aircraft are hardly tested at all...
 

BBerson

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Not sure what you mean here.
I was asking if plan sellers or kit companies report what level of flutter testing the prototype was tested to and found free of flutter. And how common is this information available?
However, the COZY (and IIRC, the Varieze and Long-EZ) POH's DO have a section on "Flutter Envelope Expansion", in which they explicitly discuss how to conduct speed expansion and stick raps. It incorrectly indicates that one should only test up to Vne, not to Vd, but that's a relatively minor nit considering that many E-AB aircraft are hardly tested at all...
Does the POH say something like: "prototype was flutter tested to Vd"? Or do they ignore disclosure perhaps for liability? Since many EA-B are hardly tested at all, is it also true that many prototypes are hardly tested at all?
 

BJC

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I was asking if plan sellers or kit companies report what level of flutter testing the prototype was tested to and found free of flutter. And how common is this information available?
Very few report any details. I know that Stoddard-Hamilton did flutter testing on the Glasairs. Van’s likely did, but I don’t know for certain.

Some kit company principles, when questioned, supplied answers that verified that they had no clue as to flutter testing, Vd and Vne. Buyer beware.

Question for HBAers: Have you tested your aircraft to Vd? Have you tested it for flutter at Vd?


BJC
 

BoKu

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What testing?...Looks like he is simply trying to get out of Phase 1 so he can jump ship. Lot's of experienced people warned of this.
Except that he doesn't have a Phase 1. Raptor is certificated as Experimental R&D, which doesn't have anything like the phases that apply to EAB. The earlier posts by Marc Zeitlin explain it well.
 

Marc Zeitlin

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I was asking if plan sellers or kit companies report what level of flutter testing the prototype was tested to and found free of flutter. And how common is this information available?
Aha. I cannot say that I've ever seen that type of information publicized by either kit or plans sellers, but that doesn't mean it hasn't happened. It's hard enough to pry individual aircraft testing results out of people, mostly because most of them have no clue how to do it even if you point them to AC90-89B or the Phase I test protocol on the COZY builders web site:


or the newer EAA document on flight testing. And the once or twice I've asked MFG's about what testing they've done, I got some hand wavy BS. YMMV.

And as others have stated, flutter testing is about the scariest **** thing you can do in an airplane - my CFII is an AF test pilot at Edwards AFB, flies F-16's and F-35's as well as a COZY MKIV and has been in combat, and he gets nervous when I ask if he's interested in flutter testing a customer's airplane (but he's done it). I did flutter testing on my plane (back when I was a lot stupider than I currently am and knew about 1% of what I now know about airplanes and flight testing), but will admit that I've never done it up to Vne, much less the POH Vd. But I restrict my airspeed only to speeds 10 KIAS lower than anything I've flutter tested to. If I ever want to sell the plane, I'll get someone else to flutter test it to Vd before I sell it.

Does the POH say something like: "prototype was flutter tested to Vd"? Or do they ignore disclosure perhaps for liability? Since many EA-B are hardly tested at all, is it also true that many prototypes are hardly tested at all?
Never seen a POH with an indication of what a prototype might have been flutter tested to, or under what conditions, but again - doesn't mean it hasn't happened or doesn't exist. Certainly, many prototypes, particularly those designed by folks with little to no engineering or flight testing experience, should be looked at with a squint unless there's some specific information about what they have and haven't tested.

As I said, the LE/VE/COZY POH's say to flutter test to Vne (not Vd), but says nothing about the prototypes.
 

Voidhawk9

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There was an RV-7 that broke up here in NZ a few years ago, and was determined to have occurred due to rudder flutter at around 244kts resulting in separation of the entire vertical and subsequently one wing. The rudder was found still attached to the vertical but broken in half half-way up and the skins separated at the trailing edge. The balance mass(es) has separated as well.

The report notes that Vans flutter tested the RV-7 up to 220kts; the VNE is 200. There's one data point at least.
 
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