Weights for flight testing

[dougbush]

What type of weights are recommended or typically used to simulate passengers and cargo for flight testing at various gross weights and CG locations?

[Auburntsts]

I recommend using something that can used for another purpose post flight. I used 40# bags of mulch. Others have used bags of water softener salt, cement, potting soil, sand, dog food, cases of water, etc. I also recommend putting down a plastic sheet/tarp under whatever you use just in case a bag rips.

[martymayes]

lead shot bags used to be the aviation standard. 25 lb bags and you can work in 25# increments. They are also great for semi permanent ballast. Oh, they are also the most $$$

[CHICAGORANDY]

As others have said, use things for which you have a later use. One caveat re: bags of sand/soil, most Big Box stores have outdoor garden centers where rain could add considerable weight to exposed bags so that supposed 30# bag of sand could really weigh a lot more. Weigh before use. Dog food is a GREAT donation to your local shelter, cat litter makes a very good oil spill absorbent for a garage floor or as winter traction assist.

[Auburntsts]

As a side note for possible ballast once you’re in Phase II, I use collapsible 5-gal plastic water containers typically used for camping. I can easily add or dump water as required and the empty containers take up little space or weight. Very handy for flights where you are solo for one leg and then pick up pax/cargo on another away from home base.

[FlyingRon]

I'd recommend against water. The problem occurs if your water container breaks or otherwise leaks. Your 5 gallons of water is now 40 pounds of ballast that may end running way aft and putting you irrecoverably out of CG. It's happened in gliders (who often take water ballast along).

[CarlOrton]

I used 40lb bags of play sand. Yes, I weighed them first! I bought some cheap plastic drop cloths and wrapped the bags well to prevent sand "leakage." The last thing you want in a brandy new plane is grit all over the place.

[Auburntsts]

There is risk, admittedly, but it’s minimal IMO. Plus in my airplane any leak would drain forward and out of the plane.

[Frank Giger]

This is where one starts polling folks in their EAA chapter to see who has the bags of shot. Chances are someone has an ancient set that have been in multiple projects.

I know folks can and have used water as ballast, but I vote against it. If a hole is in a sand bag, it doesn't all flow out endlessly. It's one of those "odds are" things. Odds are that in normal flight the water jugs won't develop a leak. But what a mess if they do!

[1600vw]

If you use shot for weight don't use this for ballast in your airplane. I speak of permanent ballast. I did this and the ballast bag moved just a little a slid against something that tore it. These bags get heavy. I then had shot all over my fuselage and my C/G could have changed if I lost enough of it. I used a sledge hammer head for my ballast. I had an old one laying around without a handle. Ran a bolt through the center and bolted it into place.

[Ron Blum]

Use whatever is cheap and easy for you. OEMs do use lead, but steel works just as well, and it is MUCH cheaper. The main concern is that the ballast is properly secured, especially if it is located behind occupants. It would be tragic to be in a survivable crash but be fatally injured by flying weight (it happens). OEMs typically bolt it in (or put it in a box that is bolted in). Seat rails are a good place to secure it. Also remember that the G loads may becoming from any direction. Flight test safely! ��

[Kyle Boatright]

I've used weight plates in gym bags secured by seatbelts. Not sure that would stand up to a 10 G impact, but I was comfortable with the setup.

Not sure what I'm gonna do on the RV-10, which will require 6-700 pounds of ballast to test properly. One thing I don't want to do is schlep anything that weighs over 25-30 pounds up on the wing and into the airplane, so...

[rv7charlie]

Two anecdotes on 'ballast'.

Years ago, before I got my license, I saw an older Vari Eze that had some cloth bags of lead shot in the nose for ballast. The owner was doing some maintenance & noticed some shot scattered around the floor of the plane. The cloth bags had rotted, and the shot had started spreading around the airframe.

While I was training for my private ticket in an old ragged Luscombe 8A, we went through about a month of bad weather, with rain almost every day and constant low ceilings. Finally got a good day to fly, so headed to the airport. Topped it off, drained the sumps, propped it off, untied, & headed for the runway for solo T&Gs. Takeoff was completely normal feeling. 1st T&G, seemed like it took fewer turns on the trim for approach, and more to set up climb attitude. 2nd one, it definitely did. 3rd, I ran out of trim on climb out & had to hold forward stick in the climb. Must have looked...unusual...because the tower radio'd to ask if everything was alright. Last landing was 3 point holding heavy forward stick. Taxied back to the tiedown, wondering what had happened. I noticed that there seemed to be a couple of drips from the belly, under the baggage area. I saw that the water was dripping from a small hole (remember, student pilot at the time), so I got a small screwdriver & poked at it. Instant stream of water. Moving aft, I poked the hole at each bulkhead & got another stream. The old fuselage was so dirty, the years of grit, dust, etc had plugged up all the weep holes in the fuselage.

Even though this was a taildragger, the water that entered the fuselage during that 'monsoon season' stayed in the cabin area until I got it sloshing over the bulkheads on climbout, with every T&G moving the water farther aft.

So don't think that water (or sand, or shot, or...) will necessarily drain forward...

Charlie