RADIO CONTROL: SCALE AEROBATICS
Eric Hawkinson 319 Yellowstone Ave., Billings MT 59101
IMAC Nationals / Events
The IMAC (International Miniature Aerobatic Club) National Championships will be in Toledo, Ohio at the Flying Tigers' field, August 22–23. Contact your local IMAC representative if you want more information. It should be a great event to attend, even if you won't be competing.
This is the time of year when you can probably find a Scale Aerobatics contest fairly close to you, no matter where you live in the U.S. I strongly recommend that you go to one of these competitions, even if you feel that you're not ready to enter one (or never intend to). You'll most likely see many people having a great time, and you'll see some very interesting airplanes. Check the contest listings in this magazine and on the IMAC or other web pages.
Correction: Crosswind Landings
In the June column there was a mistake—probably mine—that garnered some letters. The topic was crosswind landings; specifically, how to cross-control in order to make a straight approach and landing. Rather than quote the error and risk more letters, I'll summarize the proper control inputs: use aileron to lower the upwind wing, then use opposite rudder to keep the fuselage pointed down the runway and on the proper heading.
Flying That New Beauty
Since it's springtime as I write this, the usual number of test flights are being performed around the country. I've made a few of them, although not on any of my new airplanes.
During the last few decades I've had the privilege of performing test-pilot chores on hundreds of airplanes, and it always makes me nervous. Not because I have doubts about my ability to fly, but because there are so many things that can make the test flight more exciting than it should be.
It's tense enough when it's my airplane being flown for the first time, but when it's someone else's (especially someone I don't know very well), the nerves get a more severe workout.
What makes test-flying someone's airplane so intense, and how can you, as the nervous owner of the model being flung into the sky for the first time, make the odds as favorable as possible? (If you are the owner and the test pilot, the same checks apply; you'll just have half as many eyes to work with.)
If you are asking someone to test-fly your airplane, I'll assume that you have a high level of confidence in that pilot's abilities. That's not necessarily saying that he's a better pilot than you; many of my "clients" are skilled enough to test-fly their own models, but can't bear the added stress.
Since you have chosen the test pilot, and he has little control over how you built and set up the aircraft or what equipment you picked, it's important that the two of you have a good understanding of what is expected.
You should point out that you are willing to live with whatever the results are, even if that means taking your airplane home in a bag. That's not what you are hoping for, but you have to realize that "stuff happens," and the test pilot will feel bad enough without your snide remarks or backseat piloting.
You and the pilot should be comfortable about the airworthiness of the aircraft. Go over the control throws, center of gravity (CG) location, and anything else that will affect the flying. Check the wings for any warps, and check the tail surfaces for proper alignment. Anything major that is wrong here should be cause to cancel the test flight.
Preflight and Setup Checks
Make sure all surfaces are centered properly and that all servos operate, moving surfaces in the proper direction when the sticks are moved. Make sure the throttle hookup allows full throttle and a good idle, along with the ability to kill the engine via the throttle trim or a "kill" switch. Let the pilot look at the "insides" to ensure everything is secured properly, and check all control-rod connections.
Make sure the pilot knows how your radio is set up. Most pilots fly Mode II, but don't take that for granted. If you use cross-trims or a kill switch, make certain that the pilot is comfortable with your trim and switch locations.
If dual rates are active, ensure that the low rate still allows control of the aircraft and that the high rate looks reasonable. (I once saw a beautiful airplane get dirt over its spinner because the pilot switched to low rates in flight while trying to activate a smoke system, and the low rates had been set to zero throw! Leave the smoke system out of the test-flight program.)
Check the receiver pack voltage (with a proper load applied) with one of the many Expanded Scale Voltmeters that are available. Let the test pilot observe this test. Then do a range test. Even if it's a tried-and-trusted system, this is a new installation, and you and your test pilot can use the extra assurance that the radio is working properly.
Be certain that the wings and any other surfaces are firmly attached to the airplane. Give the airplane a push and make sure the tail wheel (or nose wheel if you're flying a nose-dragger) and main gear are as aligned as possible. It's usually simple to get the airplane rolling in a straight line, and this will make the takeoff much less "interesting."
Probably the thing I hate most in the hobby world is "dead-stick takeoffs." I don't mind engine-out landings that much, though with ducted fans and small helicopters they can be too exciting. The only thing worse than losing power on takeoff is losing power when you attempt to throttle up for a go-around on a missed approach, but either can be bad for your airplane's finish.
Engines and Running-In
Since many new airplanes come equipped with shiny new engines, many unknown and unproved systems are strapped up in the test flight. I keep an old clunker around for use as a test bed, to check out new or rebuilt engines and radio components. That way I can test engines on expendable airframes rather than in my latest pride and joy.
Many pilots don't have such a setup, so the airplane's first flight will also be the first flight for the engine. Still, if you want to increase the odds of a happy test flight, do everything possible to ensure the engine will run reliably at all (I do mean all) throttle settings. On some engines it won't take much more than adjusting the throttle linkage and running one or two tanks of fuel for initial break-in. Other engines will be less cooperative.
Burn however much fuel you need to in order to get the engine running reliably before the test flight. Adjust the main needle, idle mixture, and/or ignition systems so that the engine will not die when you open the throttle after an extended idle. This is far more important than getting maximum power output, and is probably one of the most critical items on the test-flight checklist.
Why so much fuss about a good transition from idle? You don't want the engine to load up and die just as the airplane rotates or when the test pilot decides to initiate a go-around. At many club fields, the area upwind of the runway is unfriendly to emergency landings. This is a test flight, and the pilot may want to make one or more intentional "missed" approaches to get a good feel for the low-speed handling of the model. Every airplane looks different on approach, and the pilot may just misjudge on the first attempt. Give him a break by making sure your engine allows the option of a second try.
Test-Flight Profile
In general, I try to make my test-flight profile fit the owner and airplane. All test flights include trimming the aircraft for straight-and-level flight. I also try out the slow-speed and stall habits of the airplane at a safe altitude, and check the control rates for a general "feel."
If things are going well at that point, I do a full-deflection roll to show the pilot the present response rate, then a few loops with increasing elevator input. At the slowest part of the loop (on top), I pull in full up elevator to check for any tendency to snap. If things still look good, I usually try some spins, knife-edges, and snaps, then shoot an approach or two and land.
On most occasions the owner is ready to fly at that point—perhaps after some adjustments—and has a much more secure feeling about flying a new model.
I hope some of this will make your test-flight sessions more comfortable. Have fun and fly safely!
Transcribed from original scans by AI. Minor OCR errors may remain.
