Flight test dummy?

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malte

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We use lead and lead bags and lead installations in our certification test flights. They can be relocated to make not only the mass, but also the CG fit the purpose and don't take up too much space, so we have room for putting measuring equipment. On some flights, we are flying with the flight test engineer for that purpose.
 

proppastie

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I have several friends built multiple seat home-builds and I do not think any one of them ever bothered to load the passenger seat with sand......people really do that I guess I am learning, but with a proven design like the RV is it necessary? Or why?
 

bifft

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Well, I consider it necessary. I've never flown an RV right at the aft CG limit before, and seems irresponsible for my first flight in that condition to be with a passenger. That said, no problems at that condition (just like you'd expect for something as well known as an RV). Not quite as stable, but much better than the Starduster at aft CG (which it always was with 250-270 lbs of me in the back seat).
 
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Daleandee

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I have several friends built multiple seat home-builds and I do not think any one of them ever bothered to load the passenger seat with sand......people really do that I guess I am learning, but with a proven design like the RV is it necessary? Or why?
Main reason is that the 40 hour phase one flight testing has to include information found at gross weight and CG locations. It's also very useful (as pointed out already) that the pilot knows how the airplane handles at gross weight and how the trim systems work in those conditions.

Dale
 

proppastie

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Now I have a way to bust their stones......I will see what they say when I ask them about their phase I testing.
 

Daleandee

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Now I have a way to bust their stones......I will see what they say when I ask them about their phase I testing.
The language from CFR §91.319 (2) (b) "No person may operate an aircraft that has an experimental certificate outside of an area assigned by the Administrator until it is shown that—

(1) The aircraft is controllable throughout its normal range of speeds and throughout all the maneuvers to be executed; and

(2) The aircraft has no hazardous operating characteristics or design features."

Operating limitations issued with the AWC will usually have a statement much like,

"The following aircraft operating data has been demonstrated during the flight testing: speeds Vso ______, Vx ______, and Vy ______, and the weight ______ and CG location ______ at which they were obtained.”

Here is a sample: Amateur Built Operating Limitations

Hope this helps,

Dale
 

gtae07

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I have several friends built multiple seat home-builds and I do not think any one of them ever bothered to load the passenger seat with sand......people really do that I guess I am learning, but with a proven design like the RV is it necessary? Or why?
It’s part of responsible flight testing. And part of learning your airplane. Even a fairly standard/“proven” basic design is going to perform differently when completed, thanks to the variety of engine/prop combinations, drag reduction means, etc. Generating performance numbers so you know what to expect at higher weights is a good idea. Most of us probably aren’t going to operate near max gross very often so it’s good to have numbers for reference.

I’ve flown an RV-6 at max gross, aft CG limit on the way to Oshkosh and back. It handles a lot differently on the runway compared to more “normal” W/B situations.

Regarding weights/bags... make sure they’re secured very well, and put things like sand (and especially concrete, as it’s dusty and such) inside another container like a heavy duffel bag or something. The idea is to contain the mess in case of a rupture, and keep it from coming loose in the cabin. In the big airplanes at work we use stacks of mild steel plates bolted to the seat tracks for ballast; that’s usually not an option in our homebuilts.
 
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malte

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A sack of dry Portland cement is 95 pounds and $10. Don't hurt your back.
Yes, and stuff like this is really a mess to clean up, if it ripps during e.g. accelerated stall tests with back CG.

You can attach less masses in lead or steel to the back of the fuselage to control CG. We often use the spin chute mount for this, but you might find other places to secure bars of lead or steel.

Same goes for fwd cg and ballast in the engine compartment. Try to hang a sack cement to the engine mount...
 

BJC

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You can attach less masses in lead or steel to the back of the fuselage to control CG. We often use the spin chute mount for this, but you might find other places to secure bars of lead or steel.
Never drove an airplane with a spin chute mount. All of mine spin just fine without the aid of a chute.


BJC
 

malte

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Never drove an airplane with a spin chute mount. All of mine spin just fine without the aid of a chute.


BJC
How many certification spin programs were among them?

Once certified or tested for spin, usually I have no need for it neither. But for an unproven design during initial flight testing it is a comfortable safety measure.


Anyway, my comment was aiming just at possible ease of controlling CG with lower masses and more comfort than carrying sand or cement in the spare seat.

Cheers,
 

cluttonfred

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I would be leery of putting weight in places other then where it would normally go when testing CG positions. A mass at the end of a long moment arm (like ballast in the tail) will behave differently than the larger mass of a passenger closer to the CG.

I like the idea of a water ballast if I could find an appropriate soft container that can be secured, maybe 5 gallon increments (45 lb or so depending on the container)? Some sort of tough bladder with tie-down grommets would be ideal, I have seen some European military surplus 20- or 25-liter water carriers that would work. For example....


 

BBerson

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I only suggested cement because one large bag is easier to strap down than several 50 pound bags. I would wrap it it in duct tape first and tape the straps securely. Sand is probably best. Or get sand and cement and build a patio afterward.
 

BJC

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No need to be sorry. Over time, you will get to know the regulars here and begin to recognize pet peeves, lame attempts at humor, and, on occasion, some really good information.


BJC
 

Daleandee

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No need to be sorry. Over time, you will get to know the regulars here and begin to recognize pet peeves, lame attempts at humor, and, on occasion, some really good information.


BJC
As Meat Loaf would sing: "Two outta three ain't bad!" 🤯
 
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