Salvage and Reprogram the AR636A Receiver from Eflite Planes with SAFE®

The Plight

Many Eflite foamy planes sold by Horizon Hobby come with SAFE® technology based on AS3X® receivers from Spektrum. While Spektrum’s AS3X receiver can be purchased separately and installed on any planes to give them 3-axis gyro stabilization, Horizon Hobby has coupled the AS3X receiver with most of their Eflite foamy planes, with additional programming, to make their planes more accessible to beginner flyers. The receiver/plane package is known as SAFE®. And the main features of SAFE® include the famed “Panic” button, as well as beginner-friendly receiver-side flight modes.

planeThese SAFE® features annoy veteran flyers to no end, and render most of these fine aircraft useless to experienced flyers, unless the $80 AS3X receiver is replaced with a normal receiver. Take the NIGHT VisionAire that I can’t stop flying, for instance. This is an exceptional 3D plane that delivers great value for the price. But its built-in receiver forces the pilot to choose either the Precision flight mode with intermediate gyro gains and ridiculously low throw rates, or the 3D flight mode with very high gyro gains, and 100% control surface throws. The gyro stabilization can never be turned off.

Perhaps Horizon Hobby can’t fathom why anyone would want to fly their VisionAire with low/zero gyro gains and very high throw rates, or high gyro gains and low throw rates. The end result is that one can never fly the VisionAire at very high speed without the plane swimming in the air like a dolphin. And one can’t have a relaxed cruising experience under strong winds.

Sarcasm aside, I do understand why gyro gains are coupled with expo and throw rates in these receiver-side flight modes. Often beginner pilots have nothing more than the free DX5e that comes with their plane. So Horizon Hobby must make it such that pilots with a dumb radio can still fly these sophisticated planes. Receiver-side flight mode is one way to achieve this goal.

The Seldom-mentioned Solution

AR636A picture IMG_1356 Cropped AdjustedBut it turns out that most of these planes actually come with an extremely capable $80 Spektrum AR636A Sport receiver, and it can be reprogrammed using just a smartphone and a special programming cable. You can change gyro rate gains, as well as heading gains. You can completely turn off AS3X stabilization in any of the three receiver-side flight modes, if you want to fly your plane without gyro stabilization.

The fact is, Horizon Hobby does not go out of its way to advertise that these supposedly locked-down “AR636A Sport” receivers can be reprogrammed without losing SAFE® features. There isn’t a lot of information online talking about repurposing the AR636A receiver, except on and some YouTube videos, and only if one knows what exactly to look for.

Updated March 2019: I’ve finally spent time understanding the AS3X firmware, SAFE and SRM (Spektrum Receiver Model). I have now written a much longer and more comprehensive article which you may want to visit, in addition to this one. Go to: What on earth is SAFE® or: How I hacked AR636 from V900 to fly the Freewing Mirage 2000, with SAFE and AS3X

Many experienced pilots chuck the AR636A and install a new receiver in order to make the plane fly the way they want. What most do not know is that AR636A is simply a normal AR636 Sport receiver with preconfigured parameters and some built-in customization tailored to particular Eflite planes. For instance, here is a version of AR636A customized for the Sukhoi. In replacing the AR636A, not only does the pilot waste an $80 receiver, they also lose Panic mode and other SAFE® features that may come in handy when lending a plane to a newbie.

spma3081 cable pictureThe solution in most cases is a $12 AS3X programming cable, plus a free app called Spektrum AS3X Programmer for one’s smart phone. These are designed to work on normal AR636, AR6335, AR7350 and AR9350 receivers. But they work just fine for the AR636A, too. In fact, the app knows about these custom AR636A receivers – when connected to one, it will properly set the receiver type to “AR636 SAFE” which is not a choice one can explicitly set in the app under normal circumstances. (Update 2018-12-15: this 3.5 mm audio cable is discontinued. It is replaced by a Bluetooth version: SPMBT1000)

Identify Your Receiver

AR636A picture IMG_1356 Cropped Adjusted AnnotatedNot all Eflite SAFE® planes come with AR636A. The VisionAire and Carbon-Z Yak 54, for instance, in 2014 shipped with the AR635 receiver. While this was a fine gyro-stabilized receiver, it could only be reprogrammed using transmitter sticks. Another example is the Apprentice S 15e – it comes with a one-of-a-kind receiver.

If you already have an Eflite plane, make sure the receiver looks like this picture. Note the extra “A” at the end of the model number, the “Sport” designation, and most importantly the “PRG” label by the bind port which serves as the programming port.

But even then there is no guarantee that your receiver is “easily” reprogrammable. Page 428 and Page 429 of the AS3X receivers thread on 2016-07-28 clarified the issue. As of this date, only a few AR636A receivers can be directly reprogrammed using the app. Most previous AR636A receivers, even if they look identical to the above, must be connected via an USB cable to a PC, and have its receiver firmware flashed, in order to unlock the receiver for reprogramming. If you want to program the receiver from your Windows PC, and not from your phone, buy the USB Programming Cable (SPMA3065) instead. Then download the PC software.

Reprogrammable receivers from the appAt this time, it seems like one reliable way to find out if the receiver from your plane can be reprogrammed without requiring a firmware flash is to look at the Programmer app. In the New Model page, planes with reprogrammable receivers are listed explicitly.

If you search in, you’ll find enthusiasts discussing AR636A reprogramming, such this discussion in the Night VisionAire thread around 2015-10-29. Note that, like this article of mine, no online information can be trusted alone. And not all information from the past you dig up will still be current and applicable by the time you read it. That discussion from 2015, for instance, makes one believe that wiping out the receiver firmware via a PC and losing the panic mode in the process is the only way to reprogram the AR636A from the Night VisionAire. That is not true, or at least no longer true as of the writing of this article (2016-07). Use the app itself as the definite source of truth.

If you are considering buying an Eflite plane, and want to make sure you can reprogram its receiver, with or without the need to first flash the firmware, start with the page which lists all planes. For some planes it lists their exact receiver model number. These are planes listed as having the AR636A receiver:

  • NIGHT VisionAire
  • Pulse™ 15e
  • P-47D Thunderbolt
  • Rare Bear
  • FJ-2 Fury

The page alone is not to be trusted, however. It lists the ParkZone® Sukhoi SU-29MM as having a normal AR636 receiver. I have the Sukhoi, and I know it comes with a locked-down AR636A Sport receiver. And AndyKunz from Horizon Hobby confirmed on that no Sukhoi receiver can be reprogrammed without firmware flash. Now you know what keywords to search for online, when researching a plane. Do your homework first.

Learning to Reprogram the Receiver

So you’ve got the AS3X Programming Cable. And you’ve downloaded the Spektrum AS3X Programmer app. Furthermore, your receiver does not require firmware flash. Where do you begin now?

If you are relatively new to RC flying, you should start with the AS3X page at Spektrum. Just remember that almost everything they write about the AR636 applies to the AR636A. Spektrum has a 16-video tutorial series on AS3X on Youtube, designed for users who buy an AS3X receiver to install on their own planes. It is useful to go through the entire set if you are new to the scene, starting with Spektrum AS3X Step 1: Transmitter Setup.

But for the purpose of reprogramming AR636A, what you need are Step 13, 14 and 15.

Spektrum AS3X Step 13: Exponential and Dual Rate explains how to set expo and dual rate on the receiver, in one of the three receiver-side flight modes. Honestly, I recommend that you change expo to 0% and D/R to 100% in all receiver-side flight modes. I set up expo and D/R on my radio instead. This allows me to decouple expo and throw from gyro gains. Recall that the bundled expo, throw and gains were what caused pilots grief in the first place with these locked-down receivers.

Spektrum AS3X Step 14: Gain Adjustment explains gyro rate gain and heading gain very well. You must watch this video. You should note that there is a small difference between AR636 and AR636A. SAFE® planes hijack the heading hold feature of AR636A to implement the Panic Mode. When you hold down the panic button on the radio, it forces the receiver into heading hold mode, to move the plane back to a stable, upright orientation. So you will want to leave the heading gain settings in N/A, if you want to keep the panic mode. You can, however, freely change the rate gains.

Spektrum AS3X Step 15: Relative Gain Settings is the key to understanding how to find the right gains for ailerons, rudder and elevator for different flying scenarios. This only applies, however, if you have a modern Spektrum radio such as the black DX6, DX9, DX18, etc. that support telemetry, and is updated with modern firmware. Your AR636A receiver is able to send back its expo, D/R and gain settings as telemetry data, to the transmitter. The transmitter then allows the pilot to dial up and down the relative gain, on the radio, while flying the plane, until the right gain is achieved. Once the right gain is found, you read the “actual” gain shown on the radio, and reprogram the absolute gain on the receiver to match what you found.

Actually Reprogram the Receiver

So you patiently learned to reprogram the receiver. And now you are actually going to do it. Just know that you are doing this at your own risk. No one can save you if you screw up.

Wiring the programming cableFirst remove the propeller from your plane. You never want to program your receiver with your propeller on the plane. Most tutorials advice you to remove your receiver, and power it with a battery pack for programming. But no one does this in practice. Everyone just plugs a flight battery pack into their plane, and power up the receiver that way. So you want to remove the prop. See how John Adams does it in this picture? Connect the programming cable to the bind port of the receiver as shown.

Power up your receiver. And launch the programmer app on your phone.

Don’t do anything in this app yet. Do not follow the initial setup instruction from the Spektrum video. Instead, just connect the programming cable to your phone. The Spektrum app will detect your receiver, and prompt you to create a new model FROM THE RECEIVER. This is the key to your success. You must let the app download current factory settings from the receiver to your phone. The app apparently tracks the model of the receiver it connects to, and it will not allow you to synchronize model changes you make in the app to the receiver, if it did not create this model from the receiver in the first place. For the Night VisionAire you will see default factory settings of AR636A reflected in the app. Flight mode 1 and 2 are identical.

App FM1   App FM3

You should take this time to name the auto-created model. And from the Settings pane, you can email this model to yourself. Save it as a backup, so you can go back to factory settings later, if you wish.

In the Settings page you’ll find that the app sets the “receiver type” for this model to “AR636 (SAFE)”. This is not a receiver type you can normally choose in the app, if you were to create a model file anew, without synching it from the receiver. The app apparently knows that it is dealing with a special, customized AR636. Note how it sets heading gains to N/A? The app knows that SAFE® uses heading hold to implement panic mode.

You can now tweak rate gain, D/R and expo on each axis. And you can try it out in real-time, too. After you tweak a value, the app will automatically synchronize it to the receiver. You can move the sticks on your radio to see these changes right away. Just remember two things. First, for the AS3X to engage in the receiver, you must first throttle up past a certain percentage – it’s a safety guard. So if the plane doesn’t seem to respond to your gain changes, make sure you have activated the AS3X once by throttling up, and then back to 0% throttle. Secondly, you have already removed the prop, right?

All I wanted was a cruise mode with less pitch rate gain to avoid the porpoise-like motion. I also did not want the receiver to impose any expo and throw constraints on any axis. So I edited flight mode 2 to make it so.

I also wanted a mode where stabilization is completely turned off. So I made the same changes as above to flight mode 1, and in addition zeroed out all rate gains.

Now I have three flight modes: 1. no stabilization, 2. low gyro stabilization, and 3. high gain for 3D flights.


That’s it for today. Fly responsibly. And try not to make garbage.

ps: 2016-07-26. Eflite is about to make available a second generation Sukhoi SU-29MM. This is the first time Eflite publicly states that a plane with the AR636A receiver can be tuned using the programmer app on a phone. But there is scantly any additional information on this detail. Instead, the gen-2 page and video go to great lengths to explain how pilots can now easily disable the Panic mode at binding time. I think Eflite is solving a non-issue – no one cares about disabling the panic mode. People want to learn to free their planes from the tyrannical regime of bundled receiver parameters. Instead of releasing a gen-2 Sukhoi with a disabled panic mode, Eflite and Horizon Hobby can better engender enthusiasm by simply providing proper documentation on reprogramming of AR636A receivers in existing planes. That said, this gen-2 plane probably comes with a receiver that can be programmed without firmware flash. I expect this plane to show up in the known plane list in the Spektrum Programmer app soon.

ps: 2016-07-28. There is apparently a new set of planes with the so-called “SAFE Select Receiver” (Spitfire and Timber). These are advertised as easily reprogrammable. I take it to mean that you don’t need to flash the firmware and lose SAFE features. Perhaps the Sukhoi Gen 2 comes with this receiver as well.

Updated March 2019: I’ve finally spent time understanding the AS3X firmware, SAFE and SRM (Spektrum Receiver Model). I have now written a much longer and more comprehensive article which you may want to visit, in addition to this one. Go to: What on earth is SAFE® or: How I hacked AR636 from V900 to fly the Freewing Mirage 2000, with SAFE and AS3X

About Xinhai Dude 辛亥生

The name Xinhai Dude 辛亥生 is a pun in Chinese, as it means both “he who was born in Xinhai” as well as “he who studies Xinhai”. I had an ambitious plan to write something about the great Xinhai Revolution of 1911, thus my blog But after an initial flurry of activities the initiative petered out. One day I will still carry it through. But for now, this website has turned into a conglomerate of my work on various topics of interest to me, including travel pictures, RC model airplane flying, inline skating, ice skating, classical music composition, science fiction short stories, evolution and atheism.
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115 Responses to Salvage and Reprogram the AR636A Receiver from Eflite Planes with SAFE®

  1. Matt Prater says:

    I have an AR636A that came from a friend after he crashed his plane (electronics were fine). I have a gas 5 channel plane I’d like to put it in. Any idea where to connect the receiver battery? Thinking I could do channel 6 since the plane needs only 5. Thanks for any help

  2. Robert says:

    Can I factory reset the AR636A, and is there any way of telling what model the receiver came out of, was given one and tried binding to my DX9 motor works as do the aileron and Elevator but no rudder.
    Or do I need to work out what the mounted orriantation was in the model from where it came,?

    • Mockinpott says:

      You can reset the receiver with the Spektrum programmer to factory settings, preferably to version 2.3 and then download an appropriate SRM file from the Spektrum site, e.g. from the apprentice s and load it onto the receiver. With the SMB program from flightengr on you can tune it to your model. You need a Spektrum USB cable or a Spektrum Bluetooth adapter.

  3. martin says:

    hi can anyone help i have a ar636a and i try to update it to put on my plane nd it says can nt update its registered to someone else i got some time back on ebay how can i get over this it will not let me register it thanks for any help

  4. Alex says:

    Hopefully you see this. This is driving me insane for simply trying to add new servos.
    I have an old Corsair with ar636a. I try to register the receiver, but they say the serial number is bad. I cannot download the update files because they are trapped behind their registry system.

    I tried to connect it to the update software, and now my receiver is useless. I don’t know if it works with an update because I cannot get the files.

    I’m hoping to use your methods, but they are impossible. I cannot find the update files anywhere.

  5. leslieomf973b4938a says:

    Thank you for your response.
    You’re suggestion worked a treat.
    Age can sometimes be a barrier to the mind!.
    Kind regards.

  6. Leslie OMeara says:

    Good afternoon.
    My name is Leslie OMeara
    I am hoping you may be able to help me.
    I purchased an E Flite Opterra flying wing with AS3X receiver installed. On setting everything up i have slight variation on the elevons one slightly up the other down. I have tried rightly or wrongley to adjust the movement to centralise the eĺevons with a servo tester, resulting in making the matter worse. Are you able to help me overcome this and go back to factory settings.
    Thank you in advance.
    Kind regards.

    • Bryan Liss says:

      You should be able to mechanically trim each elevon by:
      – First disconnecting the plastic clevis attached to the metal pushrod from the plastic horn on the elevon,
      – Next turning the plastic clevis in or out on the rod to add/reduce extension
      – Then re-connecting and checking each elevon for level,
      – Repeat until both are level.for level.

      Best to do this actually with the plane on, prop-off, throttle hold on.

      If you go to a local club, folks there can help you mechanically trim your plane and then test fly it for you, further trimming it in the air. This will make flying/learning much easier. They should also be able to help you learn to fly this plane – it’s a lot of fun :)

      Good luck!!

  7. Dave says:

    Not sure if this ancient post is even monitored any more, but I have a question about panic mode. I acquired an E-Flite timber with the AR636A, and I’m programming my Radiomaster TX16S with EdgeTX to work with it. I have everything working, EXCEPT panic mode. Can you explain what the radio sends to the RX to tell it to go into panic mode? Is it a separate channel from SAFE mode selection, or a different value on that channel?
    Thanks for this thread and all the work you do/did. Apologies if this brings back a dark chapter in your life LOL!

    • I am still alive. As long as I am alive, I’ll try to respond and help :)

      When you wrote that you have everything working, I take that you meant that you have Rate Gain and Priority working, and that you can switch between the three “flight modes” you configure with the app. Right?

      If you really want to get to the bottom of your issue, you should check out the second article I wrote since I wrote this first one: In this much longer article I actually broken down topics into chapters. There is one on exactly how AS3X is different from SAFE. SAFE is built on top of AS3X. SAFE is not the same as AS3X.

      But I’ll try to summarize key points as answers to your question.

      If Heading Gains is editable in Spektrum AS3X Programmer, then Panic will not work for you, because your receiver is in the open stock AS3X-only mode. It supports no SAFE feature, but can be reconfigured to do so (thus my second article).

      If Heading Gains is locked out for you (showing N/A) in Spektrum AS3X Programmer, then you need to set a channel (say AUX3) as the panic button. Usually people chose the channel they use for the Bind button (hopefully not a switch – don’t bind to a channel behind a switch), because during normal flight you’ll not need the “bind” functionality of your transmitter.


      • Dave says:

        Thank you for the prompt response. My rx is still in the “locked”, not ope-stock, state. so since my TX does not have a panic button, what “channel” to I need to map my momentary switch to to signal the RX to go into panic mode? is panic a “normal” channel on the RX? I’m using “GEAR” Ch 5, I think) for SAFE mode selection. but how do I tell the RX which “channel” is PANIC (I’m assuming I cannot?).

        • I am not in front of my equipment and I have not flown these for several years now. But I I remember right, maybe the receiver defaults to listening to aux 3. On spectrum transmitter they set the bind button to trigger aux 3. So in a way the AR636 is not a six channel receiver. It can listen to at least two more channels. You just can’t make it drive more than six servos. I don’t remember if the spectrum app allows you to do this in the port assignment page. Probably not. Or you would have found it. The SAFE Model Builder app I mentioned in the second article definitely did. I think in the Panic config tab. But you should double check my memory recall. Try setting the bind button on your transmitter to Aux 3. Or hit whatever switch triggers aux3. Also, remember that SAFE behavior is only turned on after initial inertial with the plane sitting without moving for a few seconds on level surface, and after you increase throttle past certain threshold. As I mentioned hopefully in both articles be careful. Either be extremely careful, or remove the prop during the process. Cheers

  8. Jim says:

    Any idea on how to get throws to go to 150% via the programming tool? In the Surface Setup section I have all the Travel set to 150% (same in the radio). In the radio’s monitor section I can see the throw go up to 150% but the servo stop at 100%. So there a dead zone between the 100 and 150 percent area.


    • Honestly, I don’t know the answer to this question. I haven’t been flying this last year, and don’t have equipment in front of me right now. Otherwise I’ll test it out myself for you.

      But I don’t recall the receiver not allowing me to go past 100% throw. Could this be a misinterpretation? Remember that the % you set on the AR636 is really a scaling factor. It’s not a direct travel %. For instance, if you set dual rate to 50% on the AR636, and then again 50% on your radio, you will get effectively 25% travel on your servo.

      So, setting 150% on both AR636 and your radio doesn’t do what you think it achieved. Also, I don’t remember if the programming tool lets you enter values greater than 100%. I just simply did not try that. As I wrote in this article, the consensus is for us (who want better control) to set dual rate to 100% and dial in 0 exponential on AR636. Then set our desired settings on the radio, only. This makes the receiver a passthrough, as far as these inputs are concerned.

      Could it be that your radio’s 100% output already got translated by your AR636 to 150% travel? You could prove this hypothesis wrong by trying your radio’s settings with a regular receiver on the same servo, if you have an extra receiver handy.

  9. Frank says:

    I recently wrecked my Cirrus and purchased a new body. When I connected my AR636A to the new body and bind it to my radio I’ve lost the Ar3x. I want this back on but not interested in having Safe on or off. How do I fix this, please?

    • Frank, I can’t really think of many reasons for this. One that comes to mind is perhaps you did not raise the throttle above 25%? See page 11 of

      This bites all the time, when I forget.

      Also makes sure that you are clear of the prop when you raise the throttle briefly, to activate AS3X.

      Just to be sure, your receiver does initialize properly after you place the plane on a flat surface, right? By initialization, I mean that it wiggles control surfaces some 5 seconds or so after you leave on a flat surface.

      • Ron Rempel says:

        I have a question on initialization my ar636 I wiped it clean by updating it to the oldest version I read some were it would create a open reciever . No w all settings read 0 but priority as it should . After binding the surfaces wiggle three times ? Why ? If I raise throttle past 25 % there is no surface reaction as expected with 0 gain my goal was to erase the memory and have a reliable open regular reciever is it now safe to use . Side note it binds and initializes upside down or in any position so I know there’s no safe or as3x in it right ?
        Thanks Ron

  10. Randolph W Geller says:

    I haven’t E-flite Apprentice e s I want to put the receiver in a F-22 Raptor by freewing is it possible or should I reprogram it what is the suggested

  11. Randolph W Geller says:

    I have an E-flite Apprentice S I crashed it I want to put the receiver into another plane can I change the program bind it or can I just flush it what do I do to it I have the Spektrum plugs for it to do this. Download on the computer what is the process it seems to work when I put it in another plane I want to put it in a F-22 Raptor by freewing

    • I also have an Apprentice S 15e which was my second plane in fact. It still flies. This was from (I can’t really remember) at least 5 years ago. My Apprentice S 15e came with one-of-a-kind receiver which I actually mentioned in this article.
      But perhaps they now come with a regular AR636?
      Does your receive look like AR636(A) shown on this article?
      Or does it look like this one-of-a-kind:

  12. George K says:

    Hi Thanks for this very helpful post! I have an ar636a from the old green sukhoi which could not be seen by the program, Then a buddy who flies futaba gave me the AR636a from the newer BLUE Sukhoi which the cable (usb) does find and allows changing settings. I wanted to disable any and all gyro flight assistance stuff, and do all flight settings (rates, expo etc) from my transmitter. I Have set all rate gains to 0, all priorities to 100 all dual rates to 100/100 and all expos to 0/0. Will these settings give me effect of an old fashioned plain vanilla non-stabilizing receiver?

    PS i also have an AR636a from 2 meter opterra- and loaded same settings into that receiver- but have not had courage to try either in an aircraft-


  13. Uri says:

    Wow, what a great article!!!

    I, too, own an AR636A which came with the Aeroscout 1.1 (HBZ3850). What I tried to do was to create on option in which no gyro stabilization occurs – using the bluetooth cable and the iPhone app, I started programming the RX and I totally messed it up.

    Do you know whether this specific model of my receiver can be reprogrammed and ultimately reverted to the original setting delivered with this model? I’, absolutely desperate here – my stupid mistake playing with it while, as you state, there’s hardly any truly reliable info about the how-to’s.

    Thanks anyway, and hope you have an idea for me.

  14. LESTIL ARNOLD says:

    I have a AR636A receiver In a different plane. There is a lable on the front of it with EFL7450 on it. I’m partially confused. I bought the plane used, a Spitfire MK2 by Phoenix. This is the plane the receiver is in. Is this receiver the one that uprights the plane to level if you get into trouble? Or is this the receiver that just assists you with flying in windy conditions. I have a Spektrum DX6I TX. Please advise. Thank you.

    • Hey Lestil. That’s an AR636A programmed for the V900 plane. If you google for “EFL7450” you will find this: Someone bolted the AS3X receiver to a plane of similar structure.

      I cannot confidently tell you if the previous owner wiped out SAFE programming (what you referred to as “one that uprights the plane to level”), without testing the receiver myself. The best way is to contact the previous owner, if you do not know what to do.

      If you are unable to find the previous owner, then you can check out my follow-up to this article you commented on. That follow-up will explain in details AS3X and SAFE. If you get a simple cable, you will be able to find out what the previous owner has done or not done, to this receiver. She may have simply bolted the receiver on without reprogramming anything, if servo orientations, etc. are identical.


      • Anonymous says:

        thank you for your assistance. I will be going through this for the next few days and see about what’s inside of this RX. I am new to this and really want to understand how to set this up. I will be writing information and reading the articles you you’ve sent.
        Thank you again for your guidance

  15. Stephen says:

    Thank you for this extensive explanation.It is interesting that you have to restore the AR636A to the earlier version 1 download in order to reprogram for a different model even though Horizon explicitly states not to do this in the case of the AR636A .

    • Yeah. One minor reason is that Horizon Hobby does not have an incentive to help people who bought a plane with a BNF AR636A (basically free with the plane) to reuse it on some other plane, when Horizon Hobby can sell you an open stock AR636.

      But the main reason is that every plane with SAFE has a fine-tuned SRM. You can’t really take that and use it to fly a different plane. Tweaking SAFE parameters is a tricky business – I’ve only understood it and started appreciate its complexity recently. HH can’t be responsible for people doing this and crashing their planes. So they have to go out of their way to tell you not to reprogram or flash your BNF AR636A.

      Not all BNF AR636A receivers can be re-programmed or flashed. Doing so with some ancient receivers may brick them. All software from Spektrum explicitly states that you must only use their software with open stock AR636. This is true. But the majority of people reported success, including myself.

      Earlier “version 1.xx” does not necessarily mean ancient and unsupported firmware versions. Basically, firmware 1.xx is pure AS3X. Firmwire 2.xx is SAFE built on top of AS3X. Spektrum continues to provide new versions of both 1.xx and 2.xx. You flash down to 1.xx, if you do not need SAFE, and only want AS3X. It’s a fine choice if that is what you want. I flashed my receiver to 1.xx so I could get heading hold on my Freewing Mirage 2000. It worked out very well.

      I’ve just written a follow-up to this article. If you really do care about reusing a BNF AR636 on a different plane, you should head to

      • Steve says:

        Like you,I am not interested in SAFE ir panic mode.I have a small Starfighter that has permenant wing wobble in windy weather and also a small Extra 330 that is quite pitch unstable if not trimmed for selected speed.I know I have to tread carefully ,however.

      • Greg says:

        I found a E-Flight FJ-2 Fury at a local Hobby shop. I am getting planes that my Dad flew as a Marine aviator. So I was glad to find the FJ. Being that Me, my Son and Grandkids fly my planes I wanted “Safe Select”. So when I tried to update the Ar636A in the Spektrum Programmer I could not. Any way around this? All my planes have AR636A RX in them and have been tweaked and tuned in the Spektrum Programmer and flightengr’s Model Builder. Thanks in advance for any thoughts

        • Wow. That’s good story and family tradition to pass down :)

          When was the e-Flite FJ-2 released ?

          Not all AR636As can be successfully reprogrammed, especially from older planes. You mentioned SMB. So you are aware of the various rcgroups threads, I think. Someone publishes once in a while the know list of planes from which pulled AR636s could be reprogrammed.

          When I have time later I’ll try to find these and link to them from my 2019 update article to this 2016 article.


          • Greg says:

            Thanks Fred, the FJ-2 Fury from E-Flight first came out in 2014. I think it has been discontinued since about 2016 or so. And yes, I have used the RCGroup site to bring me up to speed on a lot of things as I last flew RC back in the late 70’s. So I do have all my planes programmed to my liking and wanted to do the same to the Fury. I called Horizon and they said it could not be updated. I was looking for a way around that. If not, I’m sure we will wear out or crash one of my planes at some point and a AR636A will come available!

          • As we say at our field, fly safely, but when you blink, you make spare parts :)

  16. Ken says:

    For what it’s worth I rescued a AR636a from a deceased Opterra and converted it to a plain vanilla AR636. To do that flash it with version 1.43 firmware using the PC app. You give up panic and SAFE but you gain heading hold which what I needed for a new project.

  17. mockinpott says:

    On the website under “Receiver Configurations” you can find so-called srm-files for different aircraft models with AS3X Safe receivers. Could it be possible to load these files onto an AS3X Safe receiver in order to transfer the settings of the respective model to the receiver? If so, with which program/application?

  18. Ken Rosloniec says:

    Hello I have a question and may need some help.

    I followed steps in the upgrade firmware PDF. I have an a DX6 Gen3 Transmitter and the AR636a. It had firmware version 1.32 I think it was, the as3x was working ok, So I upgraded to the 2.27 version. Now it seems to not be working I installed pask in the plane I am working with I can bind it ok but after that the light on the RX goes out and I get nothing. I can disconnect and reconnect it I hear the servos make a sound and then nothing. The RX light won’t blink or flash other then in the binding mode.

    I used the latest version of Spektrum programmer 3.1 and also tried importing to the RX the : efl5150_1.2m_clipped_wing_cub and the mini_apprentice_s_1.2m. and still nothing Do I need to do something on the transmitter side? I am new at this and lost as to what I should do.

    Just for giggles to see what would happen after getting nothing, I did try the flash 1.43 ( it says not to use this) and that seemed to get the RX working again. I reflashed it to the 2.27 version and I have nothing!

    If you or anyone have any thoughts that would help would be great.



  19. Ken Rosloniec says:

    Is there any way to know what plane the AR636a came from? I purchased one from RCG but he was not sure what plane it came from as he had three of them.

    • I don’t know how you can tell. Sigh. It probably does not matter, if you get a programming cable and reset its parameters. These receivers are programmed to suit the particular planes they are plugged into. Take the VisionAire, for instance. It’s got insane throws. If you fly it at high gyro rate gains, the plane will oscillate at high speed. HH probably customized rate gains for each plane. That’s my guess.

      Again, if you follow this article and reset these parameters to your liking, it does not matter what the original parameters are. Perhaps you can connect the receiver to the mobile app, and look at its existing parameters. If it came from a Night VisionAire, the values should match what I showed in the article (I posted factory parameters for the two default flight modes in a screen capture). You may be able to find default values for other planes, online.

  20. Ken Rosloniec says:

    This question was asked, however I did not see a reply to it.
    I will be using a PC and the Spektrum programing cable with the downloaded Spektrum programmer for the AR636A. Will this method present any limitations to programming receivers?

    • I don’t have any PCs anymore, except for my home theater PC. So I have never tried to connect the receiver to my PC. I believe the iPhone app came much later compared to the PC version. People had been flushing firmware and built-in parameters on this receiver long before the mobile app came out. You should be able to do everything on the PC.

      In the beginning, flushing the firmware on a PC to make this a bare AR636 receiver appeared to be the only way. I didn’t want to do that. I wanted to keep the panic heading hold feature. This article is premised on not losing that functionality, while being able to change and decouple gyros gains from throw rates.

      You shouldn’t run into any issues. Please report back for the next guy.

      As for me, I am still flying this night VisionAire. It is seemingly indestructible. I’ve had the landing gears replaced with custom piano wire my friend bought from HobbyKing. I’ve replaced the props countless number of times. I’ve torn the vertical stabilizer off in an inverted flight gone awry. The foam body is becoming softer in places. But the whole plane still holds up very well.

  21. David Adams says:

    The ar636 is a big waste of money and time.
    Bottom line, it’s a piece of shit.

  22. Gaston says:

    You have done a great job with a pathetic subject. Thank you. I am 73. Got my first computer in 1979. Somehow, my AS3X (A636A in Park Zone Sport Cub) is finally working. How are they getting away with this illegal “tie-in” sale for a cable? In my case, make that two cables. All seems like a perfect subject for a class action lawsuit.

    • Thanks. And I hear you. and I am as unhappy about this situation as you are. But I think there are reasons why ParkZone/HorizonHobby/Spektrum would lock down the AR636A receiver. You need to consider that they sell their planes, as whole packages, at fairly affordable prices. The Sport Cub is $180. That AR635 receiver, sold alone, is $80. If anyone could pluck out an unlocked AR635 from their foam planes, and replace it with a cheap Orange receiver, then the market would be flooded with tons of AR635 on eBay, I think :)

      • Gaston says:

        You are correct – I am unhappy about time wasted by such jury-rigging. You could be thinking about the wrong fruit! Pluck out the AR635 and replace it with a Lemon 7-Channel or 7-Channel PLUS in about 8 minutes start to finish. The app is an insult to our intelligence and value of time, not to mention financial interest. But, the idea is great. The execution, in this case, is very weak. Can you imagine what this would sound like if I was an opinionated person? Regardless, I am having fun with this hobby. Ahh, I feel better! :) Keep up the fine work, please.

  23. Anonymous says:

    Thank you so much for this. I just bought the Timber and Night Visionaire and was having nightmares about not being able to change the pre-programmed parameters. This is good advice for advanced pilots who don’t want to waste money.

  24. Koosha says:

    I just bought an E-flight T-28 bfn 1.2 with AR3X AR636A
    I follow the instruction and put them together and bind the receiver with my DX6i spectrum radio
    Now all control surfaces work as normal but in page 10 of instruction manual said something about checking the AR3X if it is active or not which is tilting the plane up an down left and right and so on in this point I realized that my control surfaces does not respond to those movement
    This means theAS3X is not active (as I understand from manual)
    I don’t know what to do now
    I wonder if anybody had or have this problem and any chance to fix this?

    • Search for throttle or prop in this article. For the stabilization to engage you must first throttle up. It’s a safety mechanism. But you need to be very careful that your prop won’t cut you nor fly the plane away from you when you do this. Normally one holds the tail of the plane, or stands with the horizontal tail stabilizers wedged against the heels. If you are not sure please google for videos before you try this.

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  26. Garland Jones says:

    Good info,,but I need to know how to put safe back on the 636,, any thing

  27. Tony says:

    I have anAR636 bought from a local hobby shop. it is not programmed for anything. I have been trying to load any of my models into it so as to enable SAFE.. but i can not get it to work.

    Other than sending it back to HH any ideas?

  28. Sam says:

    Why so complicated! All I want to do is fly the plane not become a software icon a5 ar636a safe plus is off. No correction from wind or overbanking or anything…can’t figure out the issue. If only it were as easy as a red switch! Only it’s software jargon

    • Late reply as usual fr me. Sorry. I don’t have the Icon. Hit it looks like you probably bound the radio normally which would disable SAFE.

      • Koosha says:

        I just bind to my radio normally all control surfaces respond to my radio normally
        But it doesn’t respond as safe mode when I tilt the plane in the ground test
        What we can do now

  29. Anonymous says:

    I will be using a PC with the downloaded Spektrum programmer since I don’t have a smartphone. Will this method present any limitations to programming receivers?

  30. Don says:

    Excellent article. Of course by now you probably know you can buy an off-the-shelf AR636 and send it back to HH and they will program it, for a fee, to one of their stock SAFE setups that you specify.

  31. kiwi-craig says:

    do you know if the app works on the blade 200SRX helicopter receiver, its listed as an AR636A many thanks

  32. Mark Ellis says:

    Thanks for all your hard research. All very useful and well presented. I thought I would share my experience. I purchased an AR363a on a well know auction site not knowing it had been extracted from a BNF model. All seemed good as it bound with my new Spektrum DX6 and the flying controls worked after a fashion. So I purchased an Audio Updater which would not connect or give me a serial number so that I could register it. So I then purchased the USB interface cable…. I was able to connect with this cable (after applying power via a BEC) and download the Serial number which was then not recognised by the Specktrum RC product registration service. BINGO the Device was shown as Sukhoi at this point I had not found your excellent work, so lesson learned I now have 2 expensive cables and no result. I suspect Spektrum deliberately or otherwise use the same product Number on discreetly different kit to provide uncertainty to persuade modelers to chuck the recovered RX or not to buy second hand ones. All this in the hope we will buy new….. they should be happy with the money they make on the cables because I cant afford to buy a new one now ☹

  33. Wolfgang says:

    Thanks for the great summary.
    I have a gen 1 SU29 mm and am suffering from oscillations in 3D mode and ridculosly small throws in precision mode which cannot be overturned on the sender side. I do not care about SAFE at all. I just want to fly the plane like a grown up guy with decent throws …

    Hence I tried to optimize the AS3X settings of my AR636A. Here is the result:
    – The mobile app would not detected the receiver,
    – the Windows Updater would detect it and show the serial number
    – the Windows Programmer would not connect to the receiver
    Hence I tried to register the receiver to download the firmware updates.
    Unfortuantely the Spektrum website would not allow registering the receiever.

    Any hints?
    You wouldn’t have a firmware update file for the AR636 that you could make available?

    Thanks from Munich


  34. Gary Davidson says:

    Please help…. I have an Eflite Sukhoi Gen 2. The app communicate well with my plane, but during an upload the app crashed. Now i can’t get as3x working. Does anyone have the settings saved for this aircraft who could email then to me?

    • 辛亥生 says:

      I don’t have a Sukhoi Gen 2. My Gen 1 receiver can’t be flashed. I wrote about that here. I also noted my expectations about Gen 2. But I’ve just checked the app store for update to this app. I am on v 1.0.8 (iPhone). And this version hasn’t been updated since Nov 7, 2016.

      So, how did you make the app talk to your plane? Did you choose the “Default (SAFE)” profile, then?

      You need to call Horizon Hobby or Eflite. I found their customer service very professional and customer-friendly. They’ll be happy to help you.

  35. Michael Lee Holmes says:

    I have one of the AR636a receivers and am trying to figure out how to flash the firmware to make it programmable, I’ve tried to register it on the Spektrum website and it keeps giving me the error message that it’s not an AR636 receiver.

    • 辛亥生 says:

      Sorry about the late reply. I have never flashed my receiver. Part of why I went through the trouble of researching and then writing this article is because I did not want to have to deal with flashing the receiver. I didn’t really have a working PC at the time. Flashing was dealbreaker for me at the time.

    • Late reply :)

      I’ve finally spent time understanding the AS3X firmware, SAFE and SRM (Spektrum Receiver Model).

      I have also written a much longer and more comprehensive article: What on earth is SAFE® or: How I hacked AR636 from V900 to fly the Freewing Mirage 2000, with SAFE and AS3X.

      I think I finally answered all questions people asked me here, that I did not know how to respond in the past, including your questions.

      • Steve Arve says:

        Sorry but your article does not cover the fact that you cant register an Ar636A as a Ar636 at, at it says mismatch between S/n and model nr. When you cant register it, you cant download firmwares for it on web, or thru spektrum programmer.

        • Steve, I imagine that you are referring to the 2019 article, not this one from 2016. This 2016 article is about minor tweaks to AR636A without having to flush firmware.

          For more advanced tweaking, the 2019 article is more useful. And, yes, that article is geared towards regular AR636, not the pre-configured ones in AR636A. And yes, I probably should mention that you will need a real AR636 to get to the goodies.

  36. Isaak says:

    Got new Timber with AS3X on it and AR636A rx. in first 12 flights 3 times at take of plane sharply turn around and hit the ground. I got no control to recover from it. And sure plane broke. Fix it and plane do the same. Found out that AS3X settings for rudder in reverse and at take off time wind or anything else turn plane horizontally it altivate AS3X and make it worse. I did not planning in programing, but tech support says no other way to fix it. Support says if I change direction on my radio, you need to rebind. and I did several time with no result. Only reprogram with my IOS device .
    How hard to reverse rudder direction in AS3X?

    • 辛亥生 says:

      Sorry about the very late reply. The mobile app has a servo reverse setting under the Surface Setup page. Here is what the built-in help says:

      “Reverse. Changes the direction of the servo movement.Servo reversing for the control surface must be done in the application and not the transmitter. The versing setting for all control surfaces (Aileron, Elevator and Rudder) must remain normal in the transmitter.

  37. Rossi Nuccio says:

    Im trying to reprogram my rx that came with my HH Opterra / AS3X 636A. I cant seem to get the IOS cable to work well.Keeps crashing and saying recycle power etc. Any idea whats going on here?

    • 辛亥生 says:

      Perhaps it’s an app vs new iOS issue. Have you upgraded to the new iOS 10.2? When I wrote this article I was on the previous iOS version. I haven’t used this app since then. I have upgraded to 10.2 now. When I have a chance I’ll see if the app/cable still work.

      • Rossi Nuccio says:

        I’m on 10.0.2 Should I upgrade?

        • 辛亥生 says:

          I meant that I was not on 10.2 when I used this app. 10.2 is the latest iOS version. When a new version of the iOS comes out I often see apps crash.

          For example weather underground stopped working. Sometimes you have to wait for the app developer to release a new version of the app. In the case of weather underground I uninstalled the app and reinstalled it. It stopped crashing.

          • Ross nuccio says:

            Thanks very much. I’m getting connected ok now. Just need to figure out how to get a wing to work properly with a DX6i. Anybody have AR636a settings they can email me from the app ;) ??? Thanks.

  38. Eric Filsinger says:

    Thanks so much i’m getting a night vision air and wondering if this will work on my hobby zone Sport cub s2

  39. I possible could you share a screen shot of your final settings? Getting a NV next week THANKs

    • 辛亥生 says:

      Sure. I just did. Reload the article to see new screenshots showing the three modes I programmed for the NV. As I wrote on the article, I zeroed out expo in all three modes, because I programed expo separately on my radio and assigned that to a different switch. I set dual rate on all three modes to 100, because again I programed that separately on the radio.

      So, you see, the only difference between the three modes is simply the rate gain. I have effectively disabled all bells and whistles on the AR636A, except for the rate gains.

      That said… I can tell you that I’ve flown the NV every other two days for almost two months after I wrote this article. I found that I really didn’t need anything other than mode 1 where all rate gains are turned off, under most flying conditions. When it was really gusty, I sometimes switched to mode 3 when hovering. But that’s an exception, not the norm :)

  40. Hamid Sami says:

    what about programming a AR636 without the”a” to make it work like the SAFE? with the three modes and the panic? can you share the inputs?

    • 辛亥生 says:

      I don’t think you can take a stock AR636, and add SAFE to it. If you really want an AR636A with SAFE, buy one online. There are lots of people fed up with the locked-down versions.

      What you want is the opposite of what this article addresses. If you want to arm your plane for a beginner, then even a locked-down AR636A (like the one from the old Sukhoi) will be fine. In that case, pairing gyro gains to control surface throws is desirable for its simplicity. And the beginner will probably never want to turn off gyro assist.

    • No you cant, there is heading programmable but its not exactly the same, Spektrum also does not sell SAFE receivers separately for a reason, they are plane specific!!!!! Some also are locked and can not be programmed

  41. Skip Vedell says:

    Thanks for the detailed explanation. Where do I find the pc app that unlocks my AR636A to make it more tunable. I have the first gen parkzone sukhoi. Thanks

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