Air Crash Investigations - Fixed wing RC Models


Old and Bold RC PILOT
Whilst this is not exactly the place to post such an ambitious thread it is the closest I can find. If the moderators Etc wish to relocate it please do.

With this thread I hope to publish my crashes list, (abbreviated because some crashes are just not memorable), and the causes for the crashes. Perhaps upon reading this some of my errors and the cost thereof can be avoided by others.

I have had a long time experience with aircraft and flying models but apart from a few stalled attempts I never managed the actual flying effectively. With being out of the workforce I had the time and a little money so I managed to start again about 2 or more years ago. My flying had every possible error and crash event/cause and so I began my own investigative program to eliminate the crashes and I have seriously found many causes apart from the dreaded, and often blamed interference. Modern radio systems honestly do not really suffer from that much interference.

Also excluded from this list are the hundreds, (possibly more), of poor landings, brain fades, What ifs, and dumb thumb moments. If i Was to try and include those FT would need a few more harddrives:rolleyes:

Here goes.

Champ RTF - Store bought trainer.

1st entry: NUMEROUS crashes over a period of 6 months all attributable to pilot error, (I am self taught in flying!).
2nd entry: erratic and unstable elevator function - nose in roll and crash - cause poor preflight control horn slid down push rod in transport - Fix: Ensure preflight test includes physical examination.

STS - Depron scratch built - free plan
1st entry: Extreme veer left and roll on take off. Poor design/build quality insufficient right thrust combined with pilot error. - Fix: Revise motor mount and review poor control inputs.
2nd entry: Severe wobble in roll upon take off. crash on third flight. Over controlling due to control deflections being to severe and too rapid an attempt to take off. "P" factor causing forces to roll which where almost uncontrollable at high throttle/low speed take off. Fix: Reduce control throws, learn about and use Expo, revise take off technique.
3rd entry: Motor and firewall detached in flight but landed successfully. Found that Hotmelt does not adhere to plywood very well around a hot motor. Fix: Use epoxy for firewall/motor mount fitment in all future models.
4th entry. Roll in turn followed by severe dutch roll unrecoverable and crash. Very windy day turned across wind and the depron wings started twisting. No ailerons fitted and no way to exert control upon wings was just a spectator to the crash that followed. Fix: Never build single layer depron wing in a similar manner. Wings require serious torsional damping if flown in high wind.

SIG 4Star20 EP- Balsa crash rebuild
1st entry: - severe and permanent up elevator upon maiden take off. Found elevator servo had been damaged in previous crash. Fix: Relaced servo and crash survivor equipment tested more thoroughly and relegated to the FB designs.
2nd Entry: - Loss of signal event managed to avoid populace through roll and dive to ground from height. Was using HK T6A V2 entry level system which has a single polarity antenna system. Suffered from signal polarization loss, Antennas misaligned. Fix: Ensure correct antenna polarizations in future, (preflight failure again). System withdrawn from service and replaced with dual antenna system.

Quick Trick - 3mm FB Pylon racer emulation
1st entry: Wing folded in high "G" outside loop and battery catapulted across field from height. landed ok if out of control. Found that the Hotmelt glue joint failed as the FB aged and had absorbed moisture from the air. Fix: Revise design to fit dihedral or wing brace and retire hotmelt from wing joint connections.

Bixler 1.1 crash rebuild and FB Evans VP-1
1st entry: Bixler had numerous moments and a single crash, the VP-1 had the same issue and 2 consecutive crashes. Will describe last VP-1 incident as it was the most dramatic and easily evaluated.
Plane took off normally on a slightly windy day and suddenly servos jerked into different positions without any control input changes. Controls did not work and the plane stalled, rolled and crashed nose down. Found that I had overloaded the BEC within the ESC and the volts to the Rx had collapsed. Rx stopped functioning and servos twitched into random positions. I was able to replicate it at the flying field. Fix: Do an estimate of all future BEC loading and ensure that I have an adequate safety margin on BEC current draw for all builds and repairs. MY BAD!!!:rolleyes:

Since starting to investigate my crash causes interference has disappeared from my list of causes completely and has been replaced in the most part by "Pilot Error or build issues/design problems" but I needed to investigate to weed out those crashes which had explainable causes for my benefit and hopefully the benefit of others.

I encourage others who are not ashamed to admit that they crash to post the real causes if known so others can avoid the same problems



Maneuvering With Purpose
1st entry: NUMEROUS crashes over a period of 6 months all attributable to pilot error, (I am self taught in flying!).

Clearly you've never been before one off the Admiral's reviews.

"Pilot Error: To whit: an excess of confidence in pilot's own abilities, resulting in excessive risk-taking."

Self-taught. That's impressive.

Industrial companies dedicated to fostering and improving a "safety first" culture, are all about the documenting of accidents and near misses and then learning from them.
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Old and Bold RC PILOT
I am fortunate because in my case I only really have 2 choices when it comes ot determining the cause of an accident.

Either the plane suffers an equipment failure, (normally a rare occurrence), or it is my fault.

As I am mostly the designer, manufacturer, and test pilot it is easiest to just write pilot error. (Pilot has the least number of letters:rolleyes:).

I will clarify self taught. I had no on field instruction to assist my learning to fly effectively and beyond but off field I scoured the internet, books, spoke with anyone who could already fly all to get the information to help me get closer to flying or to improve my flight abilities. The same process has occurred in the design and manufacturing side.

That was before even joining the FT forums and since then I have used information from this site and helped where i could the progress of others.

This thread was started for forum users who have discovered the real reason behind their accidents and would like ot inform others of the causes and thereby help others avoid a similar occurrence.

Have fun!


Maneuvering With Purpose
I am certain that it will prove beneficial to the studious. We can look at my 2nd to last bad crash and the last one reviewed by the Admiral.

If you Google Map 470 Tinker Road, Waimanalo, HI you will find yourself at famous Bellows Field of Pearl Harbor fame. On that fateful day, two P-40 pilots managed to get off the ground and were promptly vulched by attacking Zeros.

For our purposes draw an imaginary line from the map pin to the Brothers Paintball Field. Where that line bisects the runway indicates the general southwest boundary of our old flying field. We used the area to the north of that line towards the beach for our old field. That clearing on the south side of the runway is where we conducted glider ops. We stretched the hi-starts parallel to the runway which happened to be aligned with the prevailing winds. Note the nearby low mountain range to the north. The seen of the crime.

Twice when we had abnormally calm winds, I took the Olympic 99 off the hi start and proceeded directly to the mountain ridge. Both times I made it and both times I was logging really long flights. Then, on both occasions I became disoriented and crashed into the sea.

While poor pilot judgment was the cause both times, it was not however " excess of confidence in pilot's own abilities, resulting in excessive risk-taking." Rather it was the result of exceeding line of sight visual range.

Edited: Hi-start ran parallel to the runway along the grass.
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Faster than a speeding face plant!
But isn't exceeding los visual range attributable to an excess of confidence in pilot's own abilities, resulting in excessive risk taking? :p


Maneuvering With Purpose
But isn't exceeding los visual range attributable to an excess of confidence in pilot's own abilities, resulting in excessive risk taking? :p

The Admiral would have happily invited you to the prosecuting team. We can certainly agree that it was boneheadedness. There was definitely a LOT of ego going on at the time. I was fresh off a state glider championship at the tender age of 15. But some good came of it. I WAS innovating a little. Pushing the envelope. Look at the geography. That was a little bit of a journey to that mountain. And the Olympic 99 was the WORST glider to try to cover territory with. The undercambared wing made it quite challenging to penetrate into the wind.

I have no idea if anybody ever mastered that run or even attempted it again. I was the first. I believe that the way to do it properly would be to just brush past the ridge and run east and then south. It might be possible to set up an orbit and keep it going.


Maneuvering With Purpose
Pilot error comes down to three? basic types:

1) Disorientation: the pilot becomes confused as to the attitude of the aircraft and is unable to make intelligent control inputs.

2) Overflying the design capabilities of the aircraft: this is fairly broad as it includes things like folded wings, as well as managing stall speed (tip stalls). General energy management.

3) Control input errors: twitchy thumbs, pushing stick the wrong way etc.

It seems as though most pilot error crashes can be classified this way for further analysis.


Old and Bold RC PILOT
Often the cause of a crash is rejected by those who do not understand the subject matter or who have supposedly never experienced the problem, (that they are aware of).

A case in point is the local RC club that has some very strange ideas of what safety really is. Recently they have mandated that all transmitters must be powered up before the receiver and the receiver must be powered down before the transmitter.
If you travel to the filed you will see almost every transmitter at the field is powered on even if unattended or not in use.:rolleyes:.

Personally I use a setup and operating procedure based upon a "Smartsafe" setup where my model is effectively totally dead when the transmitter signal is absent. Rather than even allow such a operation the club banned it!

The fact that I went from a crash every flying day to where I have not crashed a plane in over 2 years did not matter at all. Old school ideas die hard as does ignorance.

The "Why" is an interesting and somewhat technical argument which is beyond most, (I am trained in communications including Spread Spectrum technologies). Firstly the radios we use at 2.4GHz are NOT encrypted and transmit their GUI and data in the clear. The radios select clear channels to move, (hop), to as part of their operation. Some radios have a broader bandwidth and slower hopping rate than others.

Now here is the real issue! When there is a lot of radio transmissions at the same location it is likely that a number of transmitters will try to hop to the same clear channel at the same time. Where one of these radios is being used to control a model and, (due to polarisation losses), the transmitters signal is not the strongest received by the receiver the wanted signal can be swamped and the transmission fail totally. Where the radio transmission also includes the "Next channel" information the sync between the Rx and Tx can be lost and a LOS condition can arise.

Add to this that it is possible for a rare situation to develop where the valid transmission is received initially and the GUI is received and validated and then the Rx is swamped by an unwanted signal which has different channel information and well as different "Next channel" information. The result can be a change in flight trim/control followed immediately by a LOS, (And crash).

When flying miles from anywhere the problem is lessened but still possible when the number of transmitters using the same on air protocol are all powered up at the same time. In a residential area where there are many sources of WiFi transmissions for your transmitter to compete with for clear radio spectrum the problems become all the more likely. I deliberately chose a different on air protocol and religiously turn off my transmitter only when it is required to control my models! (Beware my setup requires a properly setup and stable radio platform).

Sadly the users of some radios believe the manufacturer hype which is based upon factory testing and not the real world. Also manufacturers are aware of the issue which is why much has been done to increase the speed at which re-association of the radio receiver to the transmitter occurs. Sadly the local club does not appreciate that its self imposed interference cloud is causing them to lose models at a regular rate. Just last week they had three crash and in the week previously they had a multicopter climb up the arm of its operator slashing with its props all the way. The random interference post GUI validation CAN include a command to start the motor/s.

Just a update on a hidden cause of random model crashes and other problem behaviours.

Have fun!