Help me select and RC airplane, 10 lb payload

[josephsomeone]

Hello Gentlemen,

I see an amazing wealth of knowledge in reviewing your forum and would like your suggestions.

I am new to the RC airplane world, but have decades of experience instrumenting aircraft for full flight simulator flight test data collection. I am eager fully instrument an RC airplane using some of the highly accurate equiptment that is accessible to me, but require the 10 lb payload. I also foresee some rough landings in my future so a sturdy construction is desired.

The balsa and plywood wing construction seems a little fragile for what I have in mind, but if it is the only construction available I will just need to keep a few spare kits around.

[jetblackaircra]

Hi Joseph,

I think they make a senior telemaster that's big enough for that payload. Try www.hobby-lobby.com It won't tell you how much it can lift, but search these forums for telemaster and there are some threads on how much people are lifting with them.

The airframe that I have designed and am building for my UAV project would work with some modifications (larger engine/battery). Would you prefer electric or gas/glow engine? What kind of flight times are you thinking of?

Check out http://www.rcgroups.com/forums/showthread.php?t=838652 and see what you think. The gross takeoff weight for my UAV will be around 12 lbs with about 5 lbs of that being payload. So, with a slightly beefed up spar and landing gear, and a larger motor you could go up to say 17-20 lbs gross. I've been planning on selling this airframe as a UAV platform, but it may be a little overkill for what you want to do.

Let me know if you want more details.

Mike

[clolson]

I've hauled an extra 5 lbs in a Rascal 110. That was doable and it flew ok once airborne, but it was really tough getting a good take off run in the grass with those loads. But perhaps if you have a paved runway and beef up the gear or bigger "tundra" tires and beefed up wing attach points, something in that size range might be made to work ??? The senior telemaster has about an 8' wing span and I think would have similar lifting capacity to the Rascal 110. The Rascal 110 is going to fly a lot nicer, but the senior telemaster has much easier access to fuselage space.

There is a 12' telemaster that is sold as a kit. That might handle a 10 lb payload a little bit better than the smaller airplanes. I would worry that something like the 8' Telemaster or the 110" Rascal would not be very forgiving if they are 10 lbs overweight ... very long take off runs, high stall speeds, I don't think the result of a stall/snap roll would be pretty, and I'd be very concerned about structural issues ... probably not insurmountable, but there would be a long line of issues just waiting for their turn to bite you.

What kind of gear is required to instrument an aircraft to get all the flight dynamics data? The MNAV system I've been working with recently (sadly discontinued) would cost about $2-3k to assemble from parts (including some of the other required bits) and could give you 3 axis gyro data, 3 axis accelerometer data, airspeed, pressure altitude, roll/pitch/yaw estimates, and control surface deflection angles could be derived from servo positions.

Something like that would weigh a heck of a lot less than 10 lbs which means it could be put on just about any RC aircraft, not just one that could support an extra 10 lbs, and if it gets you 90% of the data you needed, you could guess at the rest (or maybe derive close approximations) and probably be close enough that no one would notice.

One of these days when I get a bit further on some of my other projects, I've always thought it would be fun to devise some flight tests similar to what the FAA requires for certifying flight sims and really dial in some FlightGear dynamics models for the aircraft I have instrumented here. I've been through the Level 3 FTD process with a full scale simulator and it seems to me like most of those required flight tests could be done with pretty simple equipment. The control loading tests could pretty much be ignored. Alpha/beta would be the two useful pieces that are missing from the system I described above, but maybe you could derive estimates of these or modify the flight test maneuvers to work around this limitation?

Sounds like a fun project no matter what way you decide to go with this!

Curt.

[danstrider]

I agree with Mike on the Senior Telemaster. I have been with a group that has flown several different Telemasters. The 8-foot version (the Senior) will most decidedly carry 10lb of additional payload. We did a ballast check flight with a brick and 12v gel-cell battery, which is 11lb. Ours now weighs about 20.5lb all-up including batteries and fuel flying fine with an OS 91FX.

As for modifications, after fully-boxing the spar with shear webs, we like to use some prepreg carbon laminates from CST (the 0.014" is great) on top and bottom of the spar with some biased fiberglass wrapped all the way around the spar to tie the caps together. Kevlar tow could have done it well too. Also, we change to tricycle landing gear configuration for easier ground handling (such a big difference!). Last, we usually put 1/8" plywood on the sides of the fuselage from the nose to just aft of the wing. Oh yeah, we also have widened the fuselage an extra 2" or so for a total 6" interior width, which makes a huge difference for access and volume.

We flew a 12 foot Telemaster for a year and we never attempted to max out the payload capacity, but even with the 13+ pounds we had, it flew light. The wind would toss it around and actually make it hard to land at times. Perhaps at a flying weight in the 60lb range, it would have more penetration than at 44lb. It also needs a bit of a substantial engine. The Saito 180 did not quite cut it. The Evolution 35G at 4.1HP was a bit slack too. The Fuji BT-50 was about right. We treated the 12 footer to the same mods as the 8-footers described above.

The Telemaster series might seem not an awesome choice at first since it's built-up wood, but it's hard to find an easier flying airplane that handles well under the weight. The plywood sides and widening the fuselages really make it stout and boxy.

There are several photos available here:
12 footer: http://art1.mae.ncsu.edu/album.php?albumid=2 , http://art1.mae.ncsu.edu/twiki/bin/view/Main/12FootTelemaster
Original 8 footer: http://art1.mae.ncsu.edu/twiki/bin/view/Main/Original8Footer
Widebody 8 footer: http://art1.mae.ncsu.edu/twiki/bin/view/Main/WideBody8Footer
Superwidebody 8 footer: http://art1.mae.ncsu.edu/twiki/bin/view/Main/SuperWideBody8Footer

If you personally will by piloting expensive gear, I highly recommend getting a well-experienced RC pilot buddy to teach you. It definitely is going to take some work before you're confident flying expensive gear. At least with a Telemaster, you can learn and instrument the same airplane. I suppose you could just start flying it empty and then start ballasting it up to your flight weight, get quite comfortable flying heavy, then switch over to the real components.

Good luck and keep us posted!
Dan

[josephsomeone]

Hello Curt,

Thank you for your reply, I am really looking forward to doing this.

I will be measuring angle of attack and sideslip. Although I have not decided on the method there are several options that make sense for a RC airplane like the 8 or 12 foot telemaster. I need GPS, static and dynamic pressures, pitch roll yaw, accelerations and angular rates, control surface deflections, and a single board computer. I have some experience with inertial data from 2-3K units such as the one you have mentioned. The pitch/roll/yaw estimates are completely unreliable, the gyro data has a lot of random error that is difficult, but not impossible, to account for and the accelerometers also have biases. These can be improved by using the GPS data and Kalman filtering to improve on the inertial data. I have access to a highly accurate source of inertial data, which we use on aircraft for flight data collection, with a weight of approximately 5 lbs. I am giving myself a generous 5 lbs limit for the computer, some pressure transducers, the gps, and alpha/beta measurement.