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Testing at max gross weight

LettersFromFlyoverCountry

Well Known Member
The Phase I endorsement for the logbook that's required seems to suggest that the testing for V speeds should be done at as many different weights as possible, which would seem to include maximum gross weight.

I'm 170. Full fuel is 250... give or take... which gives me about 350 pounds for ballast I'd need in a fashion that allows me to move it forward and back.

What are people using to provide this much ballast (in an affordable way)?
 
Hi Bob,

I used 60lb bags of concrete. Just put them each in a garbage bag so you don't get dust all over. I took out the passenger cushions and they stack up nicely and can be belted in.
 
I used sand bags in various tote bags and used the handles of the totes to tie the bags to spots to keep the weight from shifting. In the baggage area I tied it to the central flap housing and varied the length of rope for various loading scenarios. I also put various weights in the passenger seat and ran the seat belts through the tote handles. It was still a bit messy until a friend loaned me some bags of lead shot which I also put in the totes for securing. Much easier with the bags of shot.
 
Large dog food bags #34. We use to breed Boxers so the extra bags didn't go to waste. Not as dense as concrete but not as messy if/when the bag breaks open.

YMMV
 
Large dog food bags #34. We use to breed Boxers so the extra bags didn't go to waste. Not as dense as concrete but not as messy if/when the bag breaks open.

YMMV

Just don't be surprised when all the airport dogs chase you down the taxiway.
 
Do be careful,... especially when working on fwd cg

make sure what ever you use will not shift with bumps, acceleration, or deceleration.... plastic bags are bad about sliding around...

you don't want something heavy sliding onto the stick or into the rudder pedals,... similar... certainly don't want all your ballast going aft when you takeoff.

I used bags of oil-dry, (can re-use later during oil changes, etc) ... and weights from a weight bench.
 
Boy, none of these do much for me. If I'm doing a 60 knot climb, everything's gonna shift. the box of lift weights (all duct-taped up and strapped in) might work. There's just so little room on a seat without messing with the passenger stick (I know what you're about to write, but it's bolted in per the plans and it ain't coming out!)
 
Some time ago, Van's RVator published an article I submitted using lead dive weights and a custom box that I strapped into the passenger seat. I could also reposition the box in the baggage area for CG trials. Everything was secure and weights could be easily be added or removed.
 
Bob,

I was given this advice for the front passenger seat, and it worked well for me. Use the 80 lb. bags of concrete mix. Double bag them with large garbage bags separetly in case you have any leaks. Remove the passenger side seat cushions. Place the bags one at a time upright against the seat back. Use your 5 point harness to strap them tightly in place. An additional partially filled bag can be used to fine tune for your particular airplane's c.g. and gross weight.

In the baggage compartment, I used 40 pound livestock salt blocks from the feed store. They are very easy to handle and fit easily.

Warning! Heed the others advice about strapping things down tight. Then double check it. If you do not have tie downs, stop now and add them. Do not take a chance. I could tell you a story but I don't want to embarass my friend...:rolleyes:
 
Lead shot

I used sand bags and lead shot. I really like the lead shot, it was easy to move around and didn't take up much space.
 
Boy, none of these do much for me. If I'm doing a 60 knot climb, everything's gonna shift. the box of lift weights (all duct-taped up and strapped in) might work. There's just so little room on a seat without messing with the passenger stick (I know what you're about to write, but it's bolted in per the plans and it ain't coming out!)

Well I know this going to cause a bunch of people to go absolutely nuts, but this is exactly why my FAA FSDO inspector has told us to forgo the sand bag/lead weight in the seat method and use a live human if they understand the potential ramifications. My large brother in law comes in quite handy for these tests!
He loads himself, which also cuts down on potential back injuries for me, as I don't have to awkwardly load sandbags/water jugs/lead weights!
The inspector investigated an accident where the sand bags shifted and jammed the stick, resulting in a fatal crash. He doesn't like those!
 
I really like the lead shot, it was easy to move around and didn't take up much space.

Yep, another vote here for lead shot; bought it in 25 lb bags at a sporting goods/gun store. Very dense and compact and can be secured by putting 'em in a duffle bag to tie down. It's probably more expensive than bags of concrete or dog chow, but could be passed/sold on to another builder.
 
Whatever you use, double bag it!

If you use dog food, you don't want to invite mice. If you use sand or concrete, it would sure stink to have a bag rip open and you permanently add 20 or 40 lbs to your plane.

I used lead shot bags, double ought works great. Again, double bag. I had one rip open right as I set it on the hangar floor after testing.

Our EAA chapter bought a bunch of bags and makes them available to any chapter member. Maybe you can talk your chapter into doing the same.

The only time we ran out of weight was with on member's Murphy Super Rebel. Man, can that thing ever haul a ton and then some! He said his plane can haul more than his Dodge Durango SUV.
 
Oil Dri...

... -then you have a lifetime supply of something you know you will use up. Kitty litter (basically the same thing - treated Fuller's Earth) for those who have cats.

Larry Tompkins
544WB RV-6A
W52 Battle Ground, WA
 
Multiple bags of chicken feed. Removed the copilot stick and belted the bags into position plus a couple in the back.
 
Use another RV pilot

We know the dangers and should inspect the plane before flight.

Like Jon, my FSDO recommended this to me. There was a local crash due to sandbags falling on controls.
 
We know the dangers and should inspect the plane before flight.

Like Jon, my FSDO recommended this to me. There was a local crash due to sandbags falling on controls.


Just curious, did FSDO recommend to take people up as part of Phase I? Or as a part of Phase II? Did they put their recommendation in writing?

bob
 
John Adams pointed out that my math is off.... 250 is what I need with full fuel, not 350.

But on this question of using a person... how does that work w.r.t. Phase I, the endorsement for emerging from which seems to suggest you test for Vx Vy and stall speeds at all -- or at least the obvious -- weight conditions?

When people enter that wording into their airframe logbook, are they entering the conditions under which the speeds were obtained? Or just entering speeds for one flight condition... normal CG and pilot-only weight?
 
My understanding is that the W&B that you carry with the airplane, that was derived from Phase 1 flight testing, needs to show that the plane has been tested at the extremes of the flight envelop you intend to fly, therefore @ gross weight and aft cg. If the paperwork in the airplane only shows more benign loadings than what you are ramp checked intending to fly with, it's a problem. I could be wrong, but that's why Mel's here:D
 
I don't think the W&B data is derived from flight testing. The W&B, I think, is derived from design and calculations of CG, which wouldn't change in flight testing. The CG is what the CG is, isn't it?

The endorsement in the logbook however, refers specifically to SPEEDS derived in flight testing.

I certify that the prescribed flight test hours have been completed and the aircraft is controllable throughout its normal range of speeds and throughout all maneuvers to be executed, has no hazardous operating characteristics or design features, and is safe for operation . The flight test was completed under the following conditions: XXXX


And my operating limitations -- if memory serves -- specifically mentions an indication of V speeds to log.
 
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You'll still need to have a weight and balance ENVELOPE where the airplane will operate - which needs to be populated with data at those min/max points in the corners. The CG doesn't change for an empty airplane - but the balance sure does depending on where you put the useful payload (fuel/passengers/bags).
 
Bob,

From my Operating Limitations, "During flight testing phase, no person may be carried in this aircraft during flight unless that person is essential to the purpose of flight."

I would not recommend this until nearing the end of phase 1. We both agreed it was essential in the front seat only. The rear seats and baggage area got the dogfood. The other pilot needs to be proficient in same type aircraft and should do a very detailed insp before flight. Both should wear appropriate safety gear. Of course, check with your insurance company too.
 
You'll still need to have a weight and balance ENVELOPE where the airplane will operate - which needs to be populated with data at those min/max points in the corners. The CG doesn't change for an empty airplane - but the balance sure does depending on where you put the useful payload (fuel/passengers/bags).

I still don't understand. Weight and balance is a mathematical formula. How does the result of that formula change in testing? Similar to the thread on testing VNE, if I load up 200 pounds in the baggage area, even though my W&B calculations say 100 pounds max, and I fly at 1830, instead of 1800, how does that change the W&B calculations which we're required to use to come up with the W&B data.

In other words, if I got the darned thing off the ground in that situation, does that really expand the W&B envelope in any sort of scientific way? What is the data that is populated on existing W&B data?

And, of course, we know the balance is going to change by moving the weight. But how does actually changing it show a different set of results than the mathematical formula which already confirms it's going to change?

It seems to me the point of flight testing here isn't to establish W&B parameters, it's to confirm that the the calculations you've already done, actually are proven correct. (or, unfortunately in some cases, not)
 
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I still don't understand. Weight and balance is a mathematical formula. How does the result of that formula change in testing? Similar to the thread on testing VNE, if I load up 200 pounds in the baggage area, even though my W&B calculations say 100 pounds max, and I fly at 1830, instead of 1800, how does that change the W&B calculations which we're required to use to come up with the W&B data.

In other words, if I got the darned thing off the ground in that situation, does that really expand the W&B envelope in any sort of scientific way? What is the data that is populated on existing W&B data?

And, of course, we know the balance is going to change by moving the weight. But how does actually changing it show a different set of results than the mathematical formula which already confirms it's going to change?

It seems to me the point of flight testing here isn't to establish W&B parameters, it's to confirm that the the calculations you've already done, actually are proven correct. (or, unfortunately in some cases, not)

Ok, I misunderstood where you were coming from on that initial post. True, the calculations used won't change, but you can't operate in Phase II in a region of the W&B envelope that has not been explored during Phase I, at least as I understand the regs. If you don't explore the GTOW with max aft CG during Phase I you can't take off in that condition during Phase II. Now you can specify your envelope for Phase II as long as you have fully explored it during Phase I....
 
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Ok, I misunderstood where you were coming from on that initial post. True, the calculations used won't change, but you can't operate in Phase II in a region of the W&B envelope that has not been explored during Phase I, at least as I understand the regs. If you don't explore the GTOW with max aft CG during Phase I you can't take off in that condition during Phase II. Now you can specify your envelope for Phase II as long as you have fully explored it during Phase I....

ah, OK. and of course that brings up new questions.

The farthest aft CG I can get in the W&B envelope, as near as I can tell...is to run on about 5 gallons of fuel...put four 25-pound bags of shot on top of each other against the baggage bulkhead (yeah, I realize that probably won't support 100 pounds, but this is theoretical), and then put 325 pounds of shot in the passenger seat.

If I can't fly in a particular configuration in Phase II that I haven't tested in Phase I, does that mean I have to also try it with 6 gallons of fuel and 319 in the passenger seat, 7 gallons with 313... and so and and so forth?

I could do a seemingly endless array of configurations in the 10 hours I have left, but by "all regions" of the W&B envelope, but what are the practical arrangements/configurations (i.e. how many and in what configuration) are people using?

Most of the performance charts I've seen over the years have two general configurations. Me by myself and, say, 1/2 to 3/4 full tanks... and me, full fuel, and as much weight as I can stuff to get to gross weight. Is that generally it?
 
Bob, I think the answer you're looking for is that you have to test the "corners" on your W&B graph. How you reach the corner point isn't relevant. If you can get to your aft CG at 1800 lb with a 300lb passenger (or simulation thereof) and 100lb of baggage, or with a 325lb passenger and 75lb of baggage, it doesn't matter, assuming both conditions equate to the same GTOW and CG location.
 
Sorry Bob, I wasn't very clear when I wrote of the W&B that is carried in the plane. I just have the scenarios of light, forward, heavy and aft covered in the W&B that I have in the plane. I've also found that the forward part of the envelope (full fuel, including tip tanks and just me at 160lbs) to have unexpected characteristics. I found that is was a bad idea to land full flaps because with the full flaps pitching moment I barely had enough elevator to keep the nose off and the nose came down at a higher speed. Wouldn't have been good on an unimproved strip.

Great to hear that you are getting so close to completing your Phase 1 testing!
 
So essentially, load your airplane into the worst possible configuration you can see being possible, fly it there in Phase I (assuming it's still flyable) and that defines your usable Phase II envelope.

I've also found that the forward part of the envelope (full fuel, including tip tanks and just me at 160lbs) to have unexpected characteristics. I found that is was a bad idea to land full flaps because with the full flaps pitching moment I barely had enough elevator to keep the nose off and the nose came down at a higher speed. Wouldn't have been good on an unimproved strip.

.... and that's exactly why we test the corners in Phase I - good to know these things... :eek:
 
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