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Written by Don Apostolico
How to do it
How-to
As seen in the November 2009 issue of
Model Aviation.


Many pilots in our hobby say, “Sooner or later, all models crash.” Is it me, or does that statement sound like a self-fulfilling prophecy?

Some can fly for years without damaging their airplanes, or they can experience electronic/mechanical failures without crashing. Others experience the same failures, and harm their models.

What’s the difference?




Don watched a stunning new Giant Scale model crash after only a few flights, because of hinge/linkage issues; the result was $4,000 lost. Little or no glue can be seen on the flat nylon hinges, and they were not pinned in place.


This article will make you aware of the major issues that often result in needless crashes, so that you can take appropriate corrective measures to eliminate the problems that cause these accidents and endanger others. I will primarily address Giant Scale models, but many of the issues I will address apply to smaller airplanes and helicopters.

The keys to model longevity are:

• Carefully choosing the correct equipment.
• Setting up equipment properly.
• Learning to fly with proficiency.
• Regularly maintaining the aircraft.

If a pilot does the preceding, the chances of crashing are substantially reduced.




Small trainer nylon servo gears cannot withstand the loads that Giant Scale models impose, but the heavy-duty metal gear on the right can.


Come to think of it, that is the safety profile for full-scale aircraft. Why not apply some of the safety concepts that have allowed full-scale airplanes to fly and land safely for decades, even if they experience equipment failure?

The world is imperfect and there are occasional full-scale accidents, but they are the exception rather than the rule. In the aeromodeling world, crashing is often the rule rather than the exception. Many modelers are doomed to repeat the same mistakes that have caused countless others to destroy their airplanes, because they don’t know what they don’t know.

The full-scale industry learns from each crash, documents details, and disseminates the information so that the cause of the accident will not be repeated. In contrast, the modeling world often depends on well-meaning but sometimes misinformed opinions and Internet threads written by modelers and RC flight instructors who are trying to help but teach with incorrect information, because that’s how they were taught. When faulty information is repeated often enough, it usually becomes fact because so many believe it.




Vent filters keep dust, dirt, grass seeds, dandelion fuzz, and other trash from entering the tank through the vent line.


These are not criticisms of the wonderful people who try to help others, but observations of the basic problem. This lack of knowledge is a challenge in education.

Throughout many years, our industry has learned the clearly identifiable success and failure patterns that have been observed to consistently work or fail under a wide variety of operational conditions. Those who don’t know the patterns are far more prone to crash airplanes than those who do know the successful setups.

Crashing or not crashing is also driven by attitudes. Some aeromodelers assume that their equipment will always work. That is an accident waiting to happen.




This meter measures current flow and locates binding servos. It is plugged into the servo, and the other end is plugged into the MatchBox or receiver.


Another attitude is that all airplanes crash sooner or later. I have learned to assume the opposite. Some type of mechanical or electronic failure will eventually occur. When that happens, I have to have set up my model to enhance the chance of a safe landing. We learned long ago how to prepare our models so that safe landings can be made if various onboard components fail or malfunction.


Success and Failure Patterns

In the past 50 years, we have learned that there are no new reasons why aeromodelers crash airplanes. We can often finish their sentences when they talk about such an incident, because we have heard the same failure patterns numerous times.




A terrific regulator from Fromeco has an adjustment feature, allowing the modeler to choose the regulated voltage from 4.8 to 6.4.


If you deal with the public in your respective professional field, you probably know what I mean. You repeatedly hear the same issues; therefore, you know what many people are about to ask or say.

My business is no different. By listening to thousands of hobby shop customers during the course of many years, I have learned what works and what doesn’t. I wish you could be a fly on the wall at my store and hear people say the same things, such as:

• “I should have listened.”
• “I won’t do that again.”
• “I learned that one the hard way.”
• “That mistake cost me an airplane.”
• “I’d still have my model if I had set it up differently.”




Proper baffling can drop cylinder-head temperatures by more than 100°. Lack of proper baffling can result in hot-running or seized engines.


Since we ask the cause of the crash at the store, we have learned that aside from pilot error, the leading causes are battery failure, switch failure, and receiver failure, in that order. Conversely, some customers tell us that they had a specific failure and simply landed their aircraft.

The next question we ask is, “How did you have your model set up?” The success and failure patterns are clear.

After hearing numerous modelers tell us that they crashed their airplanes because the airborne batteries failed and hearing others say that they had battery failures but didn’t crash because they installed a battery backup system, we quickly learned that such a setup would prevent a crash.




This deflection tool has been the standard used to measure control movement in degrees for more than 20 years.


Therefore, we recommend battery-backup systems.

That’s the kind of cause-and-effect relationship this article will cover. There is no guesswork or opinions—only straight data obtained from many people throughout many years.

One bias that aeromodelers need to be aware of is that uninformed fliers often consider their experiences the norm, because they have not seen or experienced the problem. That is not empirical data; it is an uninformed opinion based on limited data input.




The clogged filter, top, had roughly 350 flights in on one of Don’s 40% aircraft.


Setup configurations are not recommended or eliminated based on a few modelers’ individual experiences. They are chosen or excluded based on a mass of aeromodelers’ collective experience.

I suggest that we modelers, as do full-scale pilots, learn from others’ misfortunes and avoid setups or procedures that cause the needless destruction of aircraft and endanger others when an airplane goes out of control and crashes. Safety is the priority.


The Challenge

The answers to the question why models crash have been identified, but the fix is more difficult. That is because the challenge involves a personal commitment to a number of issues.




The Jaiccio regulator, designed by Jim Odino, has been the standard for many years. It reduces the 7.0-8.4 volts to most receivers’ and servos’ maximum rated voltage of 6.0.


We need to unlearn bad information or hand-me-down bad habits and educate ourselves, to overcome generations of misinformation that circulates throughout the modeling community. This education requires you to make an effective effort to obtain accurate information about performance profiles and equipment issues.

Just because your friend does it or says it’s correct doesn’t make it so. Is his technical opinion based on solid data, or is it an opinion with no factual data to back it up. Is his aircraft on borrowed time because he has “gotten away” with an unsafe setup and therefore considers it safe?

It’s for you to judge, since it’s your legal responsibility to safely set up a model.




Fuel fittings on tanks should be safety-tied on the inside and outside, to keep hoses from slipping off of fittings.


If you hurt someone or damage someone’s property, saying that your friend said it was okay and not knowing are unacceptable excuses in the law’s eyes.

Sifting out bad information from aeromodelers who are trying to be helpful can be difficult. I recommend that you challenge the source of data by asking the next questions.

If a modeler tells you that your receiver will burn out because it can’t take all the current flow from the high-powered digital servos, ask, “What is the receiver’s current limitation and how much current flow does a properly set-up model draw?”




Don load-tests batteries before every flight. Notice the reading on this 5200 mAh Lithium battery with a 1-amp load applied. This battery is safe to fly.


A pilot who can’t answer that basic question after making the profound claim or answers that he saw it on an Internet thread is probably not a source I would trust. Compare the preceding answer to, “I called the JR service center and was told that the receiver was rated for 20-30 amps.”

Which response are you going to trust? Are you going to trust your $1,000-$6,000 model to an uninformed opinion? Many do and have accidents as a result.

The good news is that aeromodeler education can solve all of these issues.

Although there are preferences in equipment choice, as with the old Ford vs. Chevy debate, the systemic issues that cause airplanes to crash don’t change.




Mitch and Tracy Kral’s good-looking 40% Carden Extra 260 on Don’s EZ Balancer. It’s easy to use and takes all guesswork out of locating the exact CG location.



Hand-Me-Down Information

Great flying skills and having been in the hobby for a long time do not necessarily mean that a flier possesses accurate information. The skilled pilot could be giving bad technical advice.

I often say that just because a person has brushed his or her teeth since childhood doesn’t qualify that person to be a dentist. Because a person can hover a model doesn’t mean that it is set up correctly. I’ve seen some excellent 3-D pilots who have unsafe setups.

Some bad hand-me-down information has been around for years. Several aeromodelers recommend that the rudder and ailerons be coupled so that the rudder moves in the same direction as the ailerons and allows the airplane to perform coordinated turns. You might have heard this from friends, read it described in magazine articles, or overheard it at the field.




Don’t guess about your needle settings. The pinch test, using a tachometer and needle-nose pliers, is the easy way to determine if the engine is rich or lean.


The problem with this is that in any crosswind takeoff or landing, the rudder is moving in the wrong direction and the takeoff or landing becomes difficult or impossible to perform safely. Try that technique in a full-scale aircraft and you’ll be calling the coroner.

An analogy is that if you want to turn your car to the left, you turn the wheel to the right. Ridiculous! But no more so than coupled ailerons with the rudder moving in the opposite direction than it should be traveling in a crosswind.

Tell a full-scale pilot that you take off in a crosswind by rolling in upwind aileron and upwind rudder to compensate for the crosswind. That pilot will look at you as if you came from another planet.




To stop a model from weather-vaning and drifting on takeoff, bank the upwind wing into the wind and apply downwind rudder to keep the fuselage aligned with the runway.


If you don’t apply upwind aileron and downwind rudder in a crosswind, out-ofcontrol takeoffs and landings are frequent. In some cases, a crash results. This is a pilot-skill issue.

Crosswind takeoffs and landings require upwind aileron and downwind rudder to maintain directional control of the aircraft; the opposite of a program coupling mix that some recommend and use. The result is often needless damage to a model or a crash caused by improper control input. When you see an airplane with this mix, you can tell that the pilot doesn’t know what he doesn’t know, or he wouldn’t be using this hazardous setup.

This flier might have gotten away with that setup and not had an accident, but that doesn’t make it right—just lucky. I don’t want to depend on luck when it comes to not harming someone; I’ll take knowledge every time. The first priority is to not hurt people or damage their property, and the second priority is to save the model.




To compensate for wind drift in a crosswind landing, bank the upwind wing into the wind and align the fuselage with the runway with downwind rudder.


Another pilot training issue is the well-meaning instructor who teaches a student to land the aircraft while controlling the descent rate with elevator rather than throttle. If the airplane is too high on final, many modelers have been trained to point the nose down to burn off altitude. Wrong!

When too high, the throttle should be retarded and the nose raised slightly to bleed off airspeed. Once the speed is bled off, the model will drop like a stone. Then the throttle is used to regulate the descent rate.

If a pilot gets this relationship backward, the model will often zoom down the runway at high speed. The result is its running out of runway or being pinned to the ground with down-elevator and flipping over.




This excellent-flying $4,500, 33-pound Cessna 152 had a receiver become inoperative after roughly two years of flight. Now it is eight years old and is as attractive as it was the day it came off of the building board.


Sometimes you hear a pilot claim that an airplane floats and won’t slow on landing. This lack of airspeed control is responsible for many landing accidents. If you have blown the approach, go around again and do it the right way.

Deficient pilot skills can be remedied by learning the limits of the flight envelope and practicing until you are proficient. An entire chapter in Gemstone Publications’ third edition of Proficient Flying, available from Don’s Hobby Shop, is devoted to this subject. Remember that elevator controls airspeed and throttle controls descent rate.

Now the hard work begins. And in some cases, you will incur expenses as you decide what degree of commitment and expenditure are appropriate. Crashing can be avoided, and in the next article, dealing with accident avoidance, I will address the major categories and issues that can prevent disasters.

If you commit to unlearning bad habits, undo bad setups, eliminate choke points, properly install the correct equipment, and learn the flight envelope to become a more proficient pilot, you will enjoy safe flying for years because you made the choice. Crashing is not an option.

Click here for a quick look at the reasons why model aircraft crash.

Have fun and fly safely.

-Don Apostolico
gems@windstream.net


Sources

Don’s Hobby Shop
(800) 972-6273
www.donshobbyshop.com






2 comments

If "the leading causes are battery failure, switch failure, and receiver failure..." I would expect this article to discuss set ups that address these causes. Instead I read a quite lengthily discussion about improper rudder to aileron mixing. This is not the best article I've read in the magazine.

Agree with position 100%.

Is my record perfect record? But one ought to strive for perfect and follow lessons of full-scale pilots and manufacturers. These planes are getting way more expensive as we engage in giant scale, and even the small planes can be deadly - years ago saw a 1/2A pylon racer hit the roof/door cornice of a Ford Explorer - had that hit someone's head, expect it would have been lethal based on the dent left in that SUV. Rare occurrence? Yes. But the ability to control a broken air system safely may go to zero and the consequences can be extremely high.

I'm building a 1/6th scale Hellcat, now, and after reading your article, feel I could use an update in current 'best practices for aircraft longevity.' Do have such a listing or could you point to a good source?

Thank you,

Dale

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