Part 2: Intermediate Soaring | Contents | Chapter 6: Intermediate Trimming
What often differentiates the beginner from the intermediate flier is the sheer amount of stuff they have.
Here's a few guidelines for identifying the intermediate pilot, so you know when you are one:
- If your van is full of backup planes, many of which you've never flown, you might be an intermediate pilot.
- If you have a silly wide brimmed hat with a name tag and buttons on it, you are almost certainly an intermediate pilot.
- If you have more than one sticker on the wings of your plane, you might be an intermediate pilot.
- If your contest plane is covered in more than three shades of monokote or fiberglass, none of which match the original color scheme, you might be an intermediate pilot.
- If you have at least three timers in your flight box, you might be an intermediate pilot.
To be an intermediate sailplane pilot, you have to have the look.
Beyond the look, gizmos and toys of all kinds are required.
Timers are critical to the operation of your sailplane.
You simply cannot be an intermediate pilot without several timing devices hung around your neck.
It creates an image of believability, even in absence of good flying skills.
Thermal pilots use them to measure their flights, and slope pilots use them to make speed runs and make sure they don't run their batteries dry on the slope.
The stopwatch is the essential timing device.
While most advanced computer radios have a stopwatch feature, basic radios do not.
Since flying is a social event, it's considered neighborly to launch and time for friends once in a while.
In all cases, a stopwatch hung around the neck is a nice thing to have.
There are basically three classes of stopwatch. First, you can buy the cheap stopwatch from Walmart or K-mart.
The really cheap ones cost less than five dollars, and last a season or two before they die.
Second, you can buy a good quality sports stopwatch.
This will cost more, perhaps twenty-five or thirty dollars, but the watch will last as long as you can find batteries for it.
Finally, you can get a high-quality count-up, count-down watch.
These combine the features of a timer and stopwatch into one.
Northeast Sailplanes Products sells a Cronus watch that is currently the standard count-up, count-down watch for most serious sailplane competitors.
This particular watch has a switch that lets it move between count-up and count-down, so you can view either time elapsed or time remaining.
As of this writing, it is priced at around thirty dollars.
A popular trick for solo flying is to tape or Velcro a cheap digital watch on your transmitter.
This allows you to start and stop the watch without looking down at it after launch and landing.
If your transmitter does not have its own stopwatch, this is a good inexpensive way to add the feature.
The timer differs from the stopwatch in that its primary function is to count down from a preset time.
Many competitive pilots have both a stopwatch and a timer.
The reason for this is that you frequently want to use the timer to record the working time left for a given round while you use the stopwatch to measure elapsed time for a given flight.
Both times can significantly affect your strategy and tactics for timed events such as F3B and F3J.
A second reason to have a timer is for precision duration practice.
You can preset the timer to your goal, say seven minutes, and then use the timer to gauge your flight and landing.
Talking timers are great for practice, since they provide a precise audio countdown of your time remaining.
Inexpensive kitchen timers of all kinds are available from the local department store.
Look in the kitchen nic-nacs section.
They come in various configurations and sizes.
Some include multiple timers, memories, clips, magnets and other features.
The ones with separate hour, minute and second buttons are easiest to use.
Most are priced between ten and twenty dollars.
Radio Shack also has a broad selection of timers, including a very popular talking timer.
The talking timer, part #63-877, is a count-up and count-down timer that is very handy for precision thermal events.
It has a voice that actually announces the time every minute as it counts down.
In the last minute, every 10 seconds are announced as well as every second of the last 10 seconds.
Currently the Radio Shack talking timer sells for less than twenty dollars.
It is ideal for solo or team practice of precision thermal events.
You set the goal time, launch, and then listen to precisely control your flight and landing.
Other talking timers are also on the market, and equally useful.
Computer radios are the ultimate toy, even in a hobby that is dominated by great toys.
If you have a real toy addiction -- and what model pilot doesn't -- a computer radio is the best toy.
If you have a computer radio, the other pilots will think you really know how to fly -- at leas until they actually see you fly!
The problem is that most computer radios are designed exclusively for power plane flying, and have marginal features for sailplane flying.
Any four channel non-computer radio will work fine for a polyhedral three channel plane.
A computer radio in a polyhedral plane offers elevator compensation when you deploy your spoilers, but little else.
Expert sailplane pilots fly a standard six servo setup -- rudder, elevator, and two servos in each wing for flap and aileron.
A sailplane capable computer radio offers not only automatic compensation of the elevator for flaps, but also lets the four independent servos in the wing to be programmed for at least four other flight modes.
In the following sections, we will examine what a computer radio can do for you and then discuss some of the features and models that are popular among sailplane pilots. I will not attempt to describe every feature of every model.
For a comprehensive book detailing literally dozens of radio models, I highly recommend Don Edberg's Programming Computer Radios .
This section will introduce some of the things a computer radio can do for you from a flying perspective.
It is important to understand how the radio helps the pilot before we get into individual features.
- Launch Mode - Launch mode is a moderate flap setting that helps the pilot achieve higher launches.
Six servo lead-sleds fly fast. This actually hurts them on launch, where a high-lift slow flying wing is necessary.
The pilot compensates by extending the flaps to generate more lift on launch, frequently coupled with some elevator trim to achieve optimal climb.
Rather than trying to manually dial in the correct amount of flaps and elevator trim for each launch, advanced computer radios offer a flap switch that puts the entire plane in the right configuration at a single click.
The pilot can also click the switch off at the top of the launch in preparation for the zoom.
Some advanced radios let you mix the ailerons with the flaps so the entire wing is cambered for launch.
- Normal Mode - This is the default flight mode where the pilot flies the most.
The plane is configured to fly cleanly with neutral flaps and elevator.
In this mode the pilot may have a variety of mixing options set to ease the workload.
The most popular setting is automated rudder-aileron mixing.
In this setting, the rudder is automatically mixed with the ailerons so the plane can be flown entirely from the right stick.
A mixing switch disables rudder-aileron mixing on demand so you can turn and burn on speed runs or coordinate the rudder by hand for very light lift.
- Speed Mode -
In speed mode, flaps are reflexed and down trim is added to provide speed.
For thermal flying, this extra speed is used primarily to move to areas of high lift, and get out of areas with down air.
It is a subtle, but useful effect.
Competition F3B fliers use extreme amounts of reflex on speed runs.
Having a pre-programmed setting lets both fliers move quickly in and out of speed mode with a flip of the flap switch.
- Cambering -
Many pilots have a knob or switch available to camber the plane slightly in thermals. Camber slows the plane and allows it to flight a tighter thermal spiral. On faster planes in light lift, this feature can be essential.
- Landing Flaps -
The throttle (left) stick is configured to control flaps for precision landing.
Full flaps can also be used as speed brakes for a rapid descent and relaunch.
When fully extended, landing flaps will be almost perpendicular to the wing.
Extending the flaps vertically down generates a lot of upward pitch, and on fast planes it is not possible to manually keep up with this pitch.
Computer radios automatically compensate by mixing the elevator into the flaps so the right amount of pitch compensation is added as the flaps are deployed.
- CROW - An alternative to full flaps is CROW.
In CROW, the flaps extend downward and ailerons extend upward at the same time.
The net effect is lots of drag with less pitching moment than flaps alone.
CROW can be used as a speed brake or for precision landing.
Some computer radios allow the left throttle stick to control either CROW or flaps at the flip of a switch.
Now that we have seen some of the practical functions of a computer radio, let's examine features that provide this functionality.
This is a laundry list of functions, most of which are provided only on the high-end radios.
Low-end computer radios typically have some, but not all of the functions listed.
- Multiple Plane Memory - The ability to store and remember multiple plane configurations.
Once you have spend $500 or more on a computer radio, you will want to use it with more than one plane.
Most computer radios store at least four models, but top of the line radios can store dozens of planes.
One big problem with this feature is that many of us have had the wrong plane selected and launched our plane -- resulting in disaster!
Selecting the wrong plane is the biggest problems with computer radios, and no one has yet come up with a workable solution.
- Electronic Subtrim - Electronic subtrim provides a mechanism for electronically centering all of your servos. This eliminates the hassle of trying to mechanically trim each control rod.
For example, if you've installed an aileron servo in the wing you just need to get the control rods in the ballpark.
You can then use the electronic subtrim
to adjust the servo so it precisely matches lines up with the wing -- no mechanical adjustment of clevises is needed.
- Travel Adjustment - Travel adjustment controls the travel (endpoints) of each servo's motion. For example, if you want your elevator to go up only 50 This also provides a method on some systems for creating aileron differential, where the aileron servo travels farther in the up direction than down direction.
Aileron differential improves the handling and reduces adverse yaw in aileron planes.
- Dual Rates - Dual rates let you adjust the throw or travel on aileron, elevator and sometimes rudder channels by flipping a switch for each.
One switch position is set to full throw while the other is usually set for partial throw -- perhaps 50 The feature was originally developed for powered pattern aircraft where large throws are needed for aerobatic maneuvers and small throws for precision maneuvers and landing.
In soaring, the feature is used primarily for different tasks.
For example, a low rate might be used for thermal soaring, while a high rate might be used for speed where violent turns are required.
- Exponential Rates - Exponential rates offer a variation on the dual rate concept.
Rather than provide a switch, exponential settings alter how the stick responds to movement.
If you move the stick a little, the servo will move a little.
If you move the stick a lot, the servo will move disproportionally more.
With exponential settings you get fine control near the center, but still maintain very large movements if you bang the stick over.
It is a useful feature, but takes some time to get used to.
Some radios offer varying degrees of exponential, which is very useful for slowly increasing the exponential throw to get familiar with the feature.
- Fixed Mixing Functions - A computer radio that fully supports sailplane programming has a number of important fixed mixing functions for sailplanes.
This is a feature than distinguishes sailplane capable radios from the more common and inexpensive pattern radios.
Common features to look for include the ability to automatically configure six servo sailplanes, V-tail mixing, flap to aileron mixing, aileron to flap mixing, a switch for CROW and flap on the throttle stick, and a three position flap switch.
This is a minimum list.
Beware many inexpensive computer radios that are designed for powered pattern fliers, and do a lousy job of providing needed sailplane mixes.
- Programmable Mixing - In addition to general mixing to handle most tasks, a good computer radio should have four or more programmable mixes.
Programmable mixes let you mix any channel with any other channel with any percentage and centering for the mixes.
These are incredibly useful for programming special features for particular planes to correct odd or inconsistent behaviors.
While programmable mixes cannot completely correct for the lack of the appropriate sailplane capability, they make a great supplement to pre-programmed mixes.
In addition, the radio should have a few programmable mixing switches so the pilot can enable or disable different features on the fly.
Rudder-aileron mixing is a good example -- the pilot sometimes wants the mixing and sometimes does not.
Quality computer radios let you decide which switch to use for different mixing functions.
- Flap Switches - A good computer radio should have at least one three position flap-switch.
The flap switch should at a minimum support preset flap and elevator settings to support the launch, cruise and speed modes so useful on competitive sailplanes.
Ideally, the radio would also allow ailerons to be mixed so the entire trailing edge can be cambered on launch and reflexed for speed.
Some radios require you to distribute these functions over several switches,
but most pilots prefer a single flap switch for instant in-flight configuration changes.
- Timer and Stopwatch - Computer radios often have a built-in timer and stopwatch you can enable from one of the switches.
These are very convenient for the sailplane pilot since you can start and stop the timer without having to look down or fumble for your stopwatch.
- Ease of Programming - Though not an outwardly visible feature of the radio, the ease with which you can program your radio to perform all of these functions is certainly a factor to consider when selecting one.
I have been to the field many times when even the pilot has no idea how to program his radio.
You might spend hours getting the settings on your plane just right, so don't overlook the importance of ease of use.
A large display, easy to follow programming menu, good instruction booklet, and pre-programmed sailplane features are most important.
Most sailplane pilots consider the Airtronics Vision and Stylus the easiest radios to program.
The Airtronics radios use a template system that lets you pick a plane like yours as a starting point, and then tailor settings for your particular situation.
Next in ease of use is the JR series (347, 388, and up).
These systems have a relatively friendly menu of features and pre-programmed sailplane features, but are not quite as friendly as the Airtronics systems.
I have not tried it, but most people tell me that high end Futaba and other systems are somewhat harder to program than JR or Airtronics radios.
Its not possible in a limited space to detail every model of radio available from every manufacturer. Instead, I will attempt to highlight some of the more popular radios in use today.
Where prices are quoted for used equipment, it is usually for either transmitter only or a transmitter/receiver pair.
Used computer transmitters are frequently sold without a receiver or servos.
Again, I recommend Don Edberg's book Programming Computer Radios for a more complete reference.
JR Radio Home Page
- JR 347 - - The JR 347 radio, though no longer in production, is probably the least expensive used fully functional sailplane radio on the market today.
It can be purchased for as little as $150-200 (RX/TX only) on the used market.
It is a seven-channel system and can operate in either FM or PCM mode.
The stock 347 includes programming for two to six servo sailplanes, dual rates, electronic subtrim, exponential, reversing, and both fixed and programmable mixing.
Fixed mixing functions include both CROW and flaps from the throttle stick, V-tail, flaperon, flap to aileron, various trims, and more.
It has four programmable mixes for additional control, and stores up to four airplanes in memory.
The only significant limit is a two position flap switch, rather than the preferred three position switch, but this can be overcome by creative programming of other switches.
JR used to sell a relatively cheap sailplane mod which converts the two position flap switch to a three position switch.
The transmitter is both PCM and FM capable.
- JR 388 - - The JR 388 is a successor to the JR 347, and is also no longer in production.
The 388 offers all of the features that the 347 does along with an eight channels, eight plane memory, eight programmable mixes, and a three position flap switch.
It has some minor additional software features for customization.
It is fully sailplane capable out of the box, and probably more widely available than the 347 because it was sold for a longer period of time.
On the used market, I would estimate that a 388 sells for $200-300 for TX/RX only.
- JR 783 Airplane Version - - The JR 783 is the follow on to the 347, and is commercially available as of this writing. It essentially offers all of the features of the JR 388, but only seven channels.
It has eight model memory, dual rates, electronic subtrim, exponential, reversing, and both fixed and six types of programmable mixing.
The JR 783 also features a smaller price tag than its predecessors, starting at around $400 for the FM, four servo version retail.
If you are looking for an inexpensive full feature computer radio and want a new one, I think the JR 783 is a great value.
- JR XP8103 Airplane Version - - The new 8103 is JR's successor to the 388.
It offers several new features - most importantly a new large size screen for easier programming.
A graphical interface makes it quicker to program than its predecessors.
The 8103 maintains all of the features you would like to see in a full-house computer radio.
It has eight channels, 10 model memory, PCM and FM, and all of the traditional features including sailplane programming and six types of programmable mixing.
It is also reasonably priced, starting at $470 for the FM, four servo system.
Part 2: Intermediate Soaring | Contents | Chapter 6: Intermediate Trimming
Copyright 1997-1998 Bradley J. Smith
All Rights Reserved