Serious accident

"Even those receivers that claim to respond only to YOUR transmitter (which smells of snake oil to begin with) and not going to save your plane in that instance."

I have been field and bench testing IPD & PLL RX for almost 12 months. As the old morse operators could be individually identified by their "key" or "signature" so to is the master TX recognised by some of the new breed of RX. I have had three different brands of TX operating similar RX on the same frequency - the main problem yet to be overcome is if a second transmitter of the same brand and model, on the same frequency, is turned on then the signature is usually to close and the RX will respond to the most powerful signal. With PPM receivers in current usage, problems arise when some users insist on using a micro receiver, designed more for light weight glider/park models with small servos, in a .90+ powered model with multi or heavy drain digital servos instead of the best for the job, especially when weight or size is not an issue, ( IMHO the HFD-08RD Supreme) which can handle the loads imposed on the board, or use another manufacturers crystal in place of the same brand as the RX. Also for consideration, is how often should TX and RX be retuned and issued a warrant of fitness to ensure that minor bangs and repeated hard landings have not sent both out of tune, in opposite directions. Many old units/crystals test well outside ideal parameters. regards Alan T. Alan's Hobby, Model & RC Web Links

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Reply to
A.T.
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Well there I disagree :-)

One of the reasons I switched to receivers wiith processor-based decoders was due to very nearly being shot-down by a burst of noise while I was on final approach with a model.

I was using a Hitec 555 receiver and with the plane at about 15 feet from the deck and about 50 yards out, the throttle went to full and the elevator went full down. Fortunately it pulled out *just* before it would have hit the deck.

Turns out that our field has a "dead spot" where your transmitter signal is canceled out by a reflection from a long row of steel hangars. I discovered that every time I flew through that dead spot I got exactly the same throttle-up, pitch down effect.

When I swapped out the 555 and put in an FMA M5 I could sail through that small dead spot without noticing the momentary loss of signal.

So, depending on your proximity to the ground (and perhaps a group of spectators or fellow modellers) the ability for a receiver to ignore a burst of interference can indeed offer "far more protection against being shot down". When that protection comes at *no* extra cost, I see no reason not to take advantage of it -- do you?

I've recently done some quite comprehensive testing of several RC receivers (dumb and smart) and the difference between a dumb decoder and a smart one is far more than you might expect.

As the level of RF noise (interference) is raised, the dumb receivers respond by starting to jitter wildly until the control inputs are dwarfed or totally eclipsed.

By comparison, the receivers with smart decoders respond to noise by simply driving the servos more slowly. If you request full up elevator you will get it -- but it may take several times as long as normal for the servos to move to that position.

This means that while the smart receiver is still affected by the noise, the results are far less likely to cause a crash and will provide a degree of control far beyond the point where the dumb receiver has sent its servos into an apoplectic fit.

However, the difference is that if you're usign a dumb receiver, your plane will probably gyrate wildly and plunge from the skies (probably with the engine still running at considerably more than an idle) in double-quick time -- far less time than it might take to advise others of your problem.

With the a smart receiver such as the Berg DSPIII, you'll either get some legacy of control (with the very slow servo movements I described earlier) or it will go into failsafe mode which, at the very least, will result in the throttle being cut. This has the potential to allow you to advise others of your problem in time for the idiot in the pits to turn off his transmitter.

But they *will* give you a much better chance of survival. And let's not forget you're *not* paying a premium for this improved chance of survival so why not take advantage of it?

So you're against improving public safety then if it means more laws?

Hell yes, but would *you* use a Hitec Feather in a 1/4 or 1/3 scale model???

There may be a place for "dumb" receivers, but that's certainly *not* in anything much bigger than 1/2A -sized models (IMHO).

I've already described the way these receivers *can* provide a valuable extra margin of safety.

Yeah, but a park-flier and a 1/4 or 1/3 scale (or even a .40-powered) model are entirely different beasts.

Wrong. Although the FMA M5 and Berg DSPII are "last-position-hold" receivers, the Berg DSP II has programmable failsafe.

Is the idiot in the pits *really* the biggest problem?

Sure, it does happen, but there seem to be a lot more people who get hit by interference from an "unknown" source.

As you concede, spread spectrum (SS) isn't a universal panacea either

-- as anyone who's encountered conflicts between their cordless phone and WiFi home network will confirm.

That's true -- but in the meantime, if you can think of a good reason why someone should buy an old-fashioned "dumb" PPM receiver when there are better (and sometimes cheaper) options available, I'd love to hear it.

-- Yes it's true, I really am crazy! Look what I'm doing now

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Reply to
Bruce Simpson

Couldn't agree more. We are flying with old technology radio equipment. We need to go to newer technology. Spread sprectrum, frequency hopping, intellegent receivers, signatured transmitters and receivers, addressable models confirmation. This is all no big deal, no technology challenge. The AMA needs to take a leadership position, work with the radio manafucturers and FCC and transition to a new non-shared frequency, with a standard data protocol so that regardless of wether it's futaba, JR, Hitec..... they all interoperate and understand each other. Gee's wifi computers and periperials can interoperate, broadband computer modems interoperate. Yes the radios would be more expensive, especially in the beginning, but if I've got a lot of money wrapped up in an airframe, I'm sure willing to spend the money to make the radio part of the system bulletproof.

We consistently preach gloom and doom , BLP will ruin us, radio operated cranes, terrorists will use rc models. WRONG APPROACH. Times change, if we don't change we will eventually loose out. Write the AMA, request them to take the lead into newer, better, safer radio systems!!!!

Wouldn't it be nice, not to have a frequency board, that when your flying and somebody turns their radio on, their transmitter doesn't transmit till it knows whats available to transmit on! That your transmitter and your receiver know that you have the right model selected! That they can cohabitate safely with sporadic interference! Thousands of addresses (channels in old technology) Folks this technology has been around for decades!!!!!!!!!!!!!!!!!

Phil

Reply to
Phil

There is a better "receiver" then the ones you mentioned that everyone owns, its free, you live with it...cant live without it!! Its called a brain and with that "receiver" it = common sense which = preflight check, knowing how to set your plane up, and flying safely. No Hitec, Futaba, Berg, or FMA will do that for you whether they are "dumb" or "smart". Anyway Bruce, do any of those receivers (dumb or smart ) come with a "

100 % guarantee...............................or we will replace your plane at no cost to you" statement??

Mike

Reply to
Mike R

Amen, Mike. Preach on, bro!

Dr.1 Driver "There's a Hun in the sun!"

Reply to
Dr1Driver

A preflight check won't protect your plane, your safety, when another transmitter on the same frequency gets turned on while in flight either by accident, malciously or by interference. A BRAIN is when you take advantage of better technology that can solve real problems. With the everything should stay as is mindset, we would still be flying reed radios.

We ARE flying with old technology radio equipment. We would benifit by going to newer technology. Spread sprectrum, frequency hopping, intellegent receivers, signatured transmitters and receivers, addressable models confirmation. This is all no big deal, no technology challenge. The AMA needs to take a leadership position, work with the radio manafucturers and FCC and transition to a new non-shared frequency, with a standard data protocol so that regardless of wether it's futaba, JR, Hitec..... they all interoperate and understand each other. Gee's wifi computers and periperials can interoperate, broadband computer modems interoperate. Yes the radios would be more expensive, especially in the beginning, but if I've got a lot of money wrapped up in an turbine, a pattern plane, a TOC quality giant scale, I'm sure willing to spend the money to make the radio part of the system much more reliable.

Soltuion is simple, one new frequency band, up high where nobody wants to reside because of distance issues. Leave the 75mhz stuff alone and for those who are flying a sport plane, are happy with current equipment.

Wouldn't it be nice, not to have a frequency board, that when your flying and somebody turns their radio on, their transmitter doesn't transmit till it knows whats available to transmit on! That your transmitter and your receiver know that you have the right model selected! That they can cohabitate safely with sporadic interference! Thousands of addresses (channels in old technology) Folks this technology has been around for decades, parts of it are in our radios now. Synthesized transmitters and receivers are part of the solution, digital receivers are part of the solution, computer radios are part of the solution, those elements are in our radios today.

Phil

Reply to
Phil

No technology will eliminate that short between the ears!

Reply to
IFLYJ3

True. NOTHING will!

In your posts, you cite many types of "new technology" that will eliminate the danger from interference, intermittent or continuous. Will you post web sites or other information (showing factual proof) so the rest of us can bask in your advanced knowledge? Dr.1 Driver "There's a Hun in the sun!"

Reply to
Dr1Driver

If there is a dead spot at your field, are all of the other fliers experiencing your problem? 15 feet high, full throttle, full down elevator and you still pulled it out. Pretty amazing! The only glitch I have ever had in all my years of flying is the one between my brain and fingers. I think true radio glitches are rare. A much bigger concern should be shoddily built planes, poor wiring, poor pilots, etc. I think you will find many more crashes and accidents are a result of these than as you say "dumb" receivers.

John VB

Reply to
jjvb

I agree 100%.

We had a guy at our field who, whenever his plane went wacko, started screaming "I was hit!" Finally, one day he was flying an original Sweet Stik. Low and slow, down the center of the runway. Slower now, nose higher to hold altitude. Slower, nose higher... Suddenly: nose straight up, wing flip, half spin. SMACK! "I was hit, I was hit!" No, you moron, can you say "stall'?

I've been in R/C over 20 years, and have only experienced provable interference twice. One time from high voltage power lines, and one time from another radio on my channel. The first time, my "out of date" PPM radio flew through it, and the other time, my plane was on the ground, in the pits. Dr.1 Driver "There's a Hun in the sun!"

Reply to
Dr1Driver

Would you like to fly with someone knowing that they have cream of the crop equipment, but does not do a rutine preflight check????? I dont know about you, but I would not. Even if he has the best technology..........a clue would be when the prop is ready to fly off the engine because he forgot to check if his propnut was tight. Would a "smart" receiver tell ya that???????????

Do you know I can build xxxxxx number of models and I woud not even need a computer radio with model memory. Check the travel of your servos before installing them, install them correctly.....you would never have to worry about touching your servo reversing switches ( how many times has someone operated a different model and forgot to reverse a servo "" ooppps plane turns left when it should be turning right" ) ................one simple reliable inexpensive radio.............so many models that it will operate.

A simpler solution would be to leave things the way they are and if someone wants to use the new techno goodies then let him/her do so when they want to.

I will belive you when the manufactures can give me a "100% guarantee".........

Mike

Reply to
Mike R

First URL :

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Others at the end.

Couple of points take for what they are worth: I am a EE designer and was working testing military frequency hopping radios decades ago. I'm not trying to "bask you with my advanced knowledge" just trying to help my fellow modellers understand that we are settling for "spark gap" technology when there are many aids in our plight.

Second let me do some explanations and relate it to things that you see take advantage of these technology today.

Our existing radios transmit a rf signal 100% of the time when you turn them on, that is why you can not have two transmitters on the same frequency. The information that is modulated on those rf signals contain information that does not require them to transmit 100% of the time, it was just a simple and cheap way to do it 40 years ago. Todays electronics are very fast, it is a simple task to esentially turn the on/off switch thousands of times per second. This is part of the fundamental requirement for frequency hopping and networking. In today's world, your cell phones and computer wireless networks utilize this technique to send/share information. For example, a current RC transmitter may send servo update information 50 times a second. Start thinking of that transmitter not being on constantly but the electronics inside your transmitter turning on and off

50 times each second. Now as designed, our radios take a little over .02 seconds to send 8 channels of servo position information for a Futaba/Jr/Hitec PPM system. In reality that can be done much faster and for the purposes of explanation I'll use .0001 seconds just for round numbers. Doing the math, 50 times in one second times .0001 seconds takes .005 seconds. So 50 transmitter bursts of information only takes up .5% of that frequency, 99.5% is available to do other things, like 199 other simulatainious transmitters running interference free. They way 200 transmitters would cohabitate on the same frequency is the also have a built in receiver. They listen before they transmit so to speak. Now think of each second as having 200 time slots repeating 50 times a second. slot 1 thru 200, then repeat 50 times each second. slot 1 is time 0 to .0001, slot 2 is .0001 to .0002, ... flyer a is in the air flying, flyer b turns on his transmitter. flyer b's transmitter listens first before ever uttering a single transmission. It "hears" transmitter a's transmissions and understands that it (transmiter a) has taken time slot 1 time intervals, so it knows it can't use that slot, so it picks time slot 2. In this example 200 flyers would never interfere even though they are on the same frequency. And you don't have to worry somebody is goin to shoot you down while flying. Incorporating this kind of technique thus has eliminated that potential, but if there is other radio ineterference on the same frequency, your still in trouble. In comes: Frequency hopping. i.e. the transmitter can change frequencies thousands of times a second. i.e. slot one is on channel 51, slot 2 is on channel 32. So your transmitter isn't just one one frequency its on many during each one second interval. Vwala, you have become significantly more immune to interference or being hit. You combine the two and you have thousands of "channels". Again this technique is used in your broadband cable modems for your computers, wifi and cell phones. All this time slot and frequency hopping is first determined by a protocol. i.e. a specification and a predetermined sequence that all the transmitters and receivers understand and expect. That makes Futaba, Hitec and JR et all all play together for interoperatabliity. That protocol defines the algorithm or sequence of how the time slots are determined and frequencies are hopped around. i.e. slot 1 is channel 51, slot 1 second frame (time period 201) is channel 37... In the computer world those protocols is 802.x or cell phones it cdma technology. In the computer world every 802.x device has a unique number or address. It's called a MAC address. The address is what establishes "connections" for devices talking to each other so the data is organized. Think of a multi model computer radio, the transmitter is address AV45, you own two receivers XC34 and VS99. In your setup you define airplane 1 as address XC34 and airplane 2 as VS99. Those two receivers are also setup to only listen to transmitter AV45. So you turn on your transmitter and it comes up setup with the last time you used it as flying the airplane with VS99 receiver. In reality you brought the airplane that has XC34 in it with completely different servo settings. You power up you plane, and it does nothing, because your transmitter is sending info to for address VS99.

At this point we have significantly reduced being hit by an accidental transmitter turn on of the same frequency, we've made it less suspectable to noise hits, and we have eliminated selecting the wrong model on our transmitters. Yet there is more that can be done. If you have not been "hit" by radio interference, you probably know somebody who has. AM and PPM are suspectable to that because they can intrepret noise as valid servo position information. In comes data validation. Computers use many types and combinations of error checking, you probably heard the term checksum. Essentially a cecksum is a numeric addition of all the data that was sent in one frame or packet.... In our case as the transmitter is sending those 8 channels of data in slot 1 it adds all the position information of each channel and sends that number like its channel 9. The receiver does the same, it adds all the 8 channels of data and compares it to the checksum the transmitter sent as channel 9. If they match, the receiver updates the servos with the information, it they don't it doesn't update the servo's and it start to gather information to make a decision. In the next slot of time on a different frequency the receiver does the same checksum test. If it's good it updates the servo's at the flyer doesn't have a clue he got hit, if it doesn't the receiver starts down a decision path. That decision path would be programmable, i.e. if you get 20 consecutive frames of non checksum confirmed data, you throttle down to idle, if you get 100 you set the surfaces to a failsafe psition you determine when you set the receiver up initially. So we have just made the noise issue even less impacting, in fact it maybe able to cohabitiate with random noise without knowledge.

This is just some high level explanations of how rf networks work and the computer technology we should be seeing in our radios. Do I propose getting rid of the existing radios, no. Put the new technology on a different band, let the sport flyer or beginner use the $150 radio or the jet guy if he wants. But give hime the option of better technology so if he has a $10000 turbine he can take advantage of making it as safe as the technology allows.

url's

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My fingers are worn out. :-)

Phil

Dr1Driver wrote:

Reply to
Phil

No they don't -- at least not any more than the seatbelts and airbag in your car guarantee that you'll survive a road-smash -- and that's perhaps the best analogy.

Few of us have had a really serious auto-crash -- but most of us would not even think about driving every day without putting on a seatbelt or enjoying the peace of mind that an air-bag provides.

Neither the belt nor the bag will save you from death or injury in a really bad smash -- but they significantly increase your chances of survival.

And that's how I like to look at these receivers.

It's not often we get hit by interference (just like it's not often we have an auto-smash) but doesn't it make sense to take precautions to protect ourselves in the event that it does happen?

-- Yes it's true, I really am crazy! Look what I'm doing now

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Reply to
Bruce Simpson

There is no such thing as a 100% guarantee. Ask yourself these questions. 1. Do you drive a model T or much more recent vehicle? 2. Do you just have a radio no TV? Probably in both cases you have the newer technology. With your equivalent line of radio reasoning you would still be driving the model T because it can get you there just like a much newer vehicle, and you would still be listening to a radio because it entertains and gives you the news also.. Analogy, would you make every body skip bypass surgery with severly blocked arteries just because it wasn't 100%.

No I wouldn't, would you fly with somebody who did a preflight but bragged his radio was designed by himself, it was the next channel over, and look like a hairball of wires?

Of course not, but a smart receiver that new it wasn't receiving correct servo data that shutoff rather than going full throttle would have probably prevented this accident.

need a computer radio with model memory. I can, I have, but I prefer model memories. If you had a multimodel radio and you built a new plane, that had a servo built in and you found out on the first flight it had a surface had to much authority, would you tear it apart to move the horn position or would you turn the settings on that model down with your radio?

wants to use the new techno goodies then let him/her do so when they want to. That is exaclty what I said " Soltuion is simple, one new frequency band, up high where nobody wants to reside because of distance issues. Leave the 75mhz stuff alone and for those who are flying a sport plane, are happy with current equipment." I should have left the sport plane out and just used the phrase "happy with current equipment" though. Nobody should be forced to switch.

Does your prop manufaturer give you a guarantee it won't break? Of course not. Hypothetical- If you could buy a "super prop" that was 100 times safer with better performance for a few bucks more you wouldn't? Thats what your effectively saying about the radio system.

Guys I'm not trying to pick a fight here, I'm not trying to come off as some brain or intellect. If I did either I didn't intend too. Believe me I am no smarter than you, but my education, work experience and expertice is electronics.

Finally I love my hobby, enjoy the heck socializing with my fellow flyers, I DON'T WANT THE GOVERNMENT OR FAA OR FCC OF CONSUMER PRODUCT SAFETY COMISSION TAKING IT AWAY BECAUSE IT"S NOT SAFE PER THEIR DEFINITION. I say lets help reduce the potential to give them the excuse because they want the frequency, or they don't like RC'rs.

Phil

Mike R wrote:

Reply to
Phil

I know you are not picking a fight, neither am I...........it is fun to argue :-) I checked the links out and I understand what you are saying. I have nothing against this stuff. I am guilty of it myself. As an avid model railroad junkie I jumped on the DCC bandwagon a few years back. Just love my DigiTraxx Challenger. I do know how to block....never forgot that. What I am saying is we should not solely rely on technology to help us. It should be a "tool" to use wisely. I believe more emphasis on pilot skill, practice, and proper setup. I guess I am just "old school".

Mike P.S. I drive a 90 Pontiac AWD sedan ( would rather have the model T because I just got the bill back from the tranny shop.....$900.00 ouch...I could sell the model T and get a new car... :-) ) Have a TV......not HDTV......but soon :-) If I see someone show up with a "hairball wired homemade radio" I probably would give the guy phone numbers of good attorney. Servos stuffed into plane that are inaccessible are as useful as a rubber crutch in a hospital ward.

Reply to
Mike R

Not the only reason.

The

It also suppresses low level interference. AGC and all that etc.

At this point we have significantly reduced being hit by an accidental transmitter

Indeed.

a

Well, yes or no? Who wants to pay $500 for a slightly more reliable sstemn when $50 buys you a simple one that works most of the time?

I used to fly 27Mhz superregens. One plane at a time ONLY folks.

I upped the power to 5W or so and got total reliability :D

Do I propose getting rid of the

Now you are making total sense. If interference is the prime suspect.

BUT in the context of this and other accidents, is this really the cause

- usually total loss of control is NOT interference, Its gross failure - broken wires, flat batteries, servos just 'let go' or hinge or clevis failed.

Ive been flying afater coming back a few yaers now - seldom at a club field, mostly solo, and all my loss of control scenarios have been failures. Pack fell out (twce at least, different models) wings folded (twice) BEC shut down (once maybe, or possibly twice) hinge failed (once) ESC blew completely due to partually sized motor (once) forot to extend Antenna (once)

I've had plenty of intereference, but never enough to totally lose control.

Sure I'd like better radios, but it wouldn't have solved MY problems.

Biggest cause is pilot error, second biggest is unexpected failure of a component. Often as a result of crash damage or heavy landings.

The reason full size aircarft are so safe is not due to any particular peice of technlogy: Its down to the skill and training of the pilots, flying very conservatively, and a rigiorous maintenance schedule that won;t let a plane in the air unless it checks out.

I've been held up an hour on a runway in an airliner whilst the brake discs were changed. Despite the intended destination having a runway long enough to never need brakes at all hardly.

We fly our models aggressively, without such rigorous strip down and test regimes, and in (scale) conditions no full size pilot would take off into. At power to weight ratios the average spitfire piliot would be proud of, pulling enough G's sometimes to render a real pilot unconscious.

In short we are expecting an awful lot from a few cents of connectors and wires and servos. and a few bits of balsa and plastic film. Let alone our own skills and reflexes.

Let's solve the real issues.

How many people DO really get 'shot down' ?

and even with advanced technology - e.g. my cellphone - there are still places where it goes bad on me (near matallic objecst) occasionally suffers from oher channel breaklthrough (yes, I have heard the odd scrambled and garbled speech of others occasionally even on a GSM system

- lord knows how tho) and is still susceptible to being swamped by other lager transmitters in the neighborhood that overload it.

Its a thought tho. Put a cellphone in your plane receiving data transmissions, and fly your plane with unlimited range as long as there is a GSM cell, from a transmitter plugged into your own phone, for only the cost of a 'network call'.

How many people feel that reception on their GSM phones is reliable enough for that, I wonder?

Reply to
The Natural Philosopher

Indeed. If I could get a model T for $500, I WOULD drive it.

I DO listen to teh radio - yes even AM radio - precilely because it DOES carry teh news.

If it checked out, yes.

No argument there. All my leccy planes have speed contrllers that shut teh motor of they don't receive valid or seemingly valid throttle signals.

However all that takes is a minor additin to e.g. the throttle servo. Or a single chip in the receiver.

So is mine, but it also goes beyind that to running companies and actually having to make decisions based on risk assesmnet as well.

Sure we can build MUCH better radios, but will that solve the problems And how much will they cost?

All the technology in the world won't fly a plane whose receiver battery has just died.

Reply to
The Natural Philosopher

If "true" you're on the right track.

Texas Pete

Reply to
Pete Kerezman

They guy who is flying a 12,000 turbine or a $7000 Big bird, Or a extremly labor intensive Scale model, or a guy flying a $4000 pattern ship. On the other hand, it probably shouldn't cost an additional $500. Because there are cheaper compatability modes. Frequency hopping really isn't required, that would eliminate the sysnthesized transmitter which is a definite cost. But burst transmissions, addressable receivers and a receiver in the transmitter is. S/B little to no recurring cost to the receiver, traasmitter would go up. A lot of transmitters are computerized today, so the recurring cost it the cost of incorporating a receiver in the radio.

True, but my second airplane was totalled because a person turned there transmitter on on my frequency without looking at the frequency board. I have wittnessed several other peoples losses because of mistakes made in frequency handling, all accidents, none malacious. Radio interference is like to become more of an issue if BPL turns out to be the terror for radio systems some people believe it will be. A jet rally in Ohio last weeken was called after one jet was lost and scanners showed periodic random interference on multiple channels. People had come from long distances for nothing.

cell phones don't use any error checking, periodic loss of portions of voice they consider no big deal.

You don't want a cell phone in your plane, you just want our current transmitters and receivers moderized to take advantage of error checking, addressable communications. Technically there is no reason today that error checking coudn't be more incorporated. Some PCM systems do have some, a PPM system could, but I don't know of any that do. Receivers could be better also even with existing ppm systems. Pulse widths, frame times and sync times could be validated to discrimiate interference. Receivers could also have some minor energy storage, so if power were lost, it could detect and close the throttle servo, and electronically disconnect that servo before the last breath of energy was lost. None of this is very expensive.

Again, nothing sould be forced on the existing channels. Let those continue as is for those who want. One spot on a higher frequency band for a new system. If that happened, it was done right, I'd be money 10 years later, nobody would be on the existing channels.

Phil

Reply to
Phil

True, BUT......... Even with todays radio systems. IF they would just put some capacitive energy storage in a receiver and implemented battery fault detecion, a receiver could, when it sensed imment power loss, kill the throttle servo with its last gasp of power. At least then you wouldn't have an aircraft flying full throttle out of control. This was a full throttle out of control big bird with a carbon fiber prop that hit the guy some significant time after he lost complete control. If the receiver had killed the engine, this serious injury would likely not have happened.

Phil

Reply to
Phil

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