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Author Topic: Throttle Cut - A Critical Item!  (Read 102 times)

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Offline Deerslayer

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Throttle Cut - A Critical Item!
« on: July 24, 2018, 07:32:13 AM »
Please, folks, do something about this on your electric models before someone gets seriously injured!

Before instructing or helping anyone, why not take a minute to ensure that your client has a proper Throttle Cut set up, or help them to set it up. Prove it before flight!

 Wouldn't this be a good time to ensure that your power failsafe works properly, as well?

 Here is the proper way to set up Throttle Cut on Spektrum radios.  If you do not understand, or if you disagree with this, please contact me and we will upgrade it.  Taranis, Graupner, Futaba are also in common use at our field; perhaps others will add appropriate procedures.

 First, decide which common switch you plan to use for ALL of your models.

Electrics:
Set the Throttle Cut value to -100%. Spektrum has a default of -130%, but this is a very bad idea for electrics. Why? Some ESC's "auto-learn" the Throttle channel endpoints. They are not very consistent across brands; if your ESC "learns" -130% as the new zero point, as soon as you disengage the Throttle Cut, the motor may start! This has happened to me and to countless others that I know of.

Disable the Trim (set = 0) for Throttle. That will ensure that you cannot leave the throttle Trim advanced, release the Throttle Cut and have the motor come to life. Or, have inadvertently programmed your ESC to an undesired range.

Glow and Gas:
 Set things up such that activating Throttle Cut will drive the channel to your kill point. The -130% may be OK, with leaving the Throttle Trim enabled. With our IC engines, we tend to use Throttle Trim at least on some occasions, so you may want to leave its sensitivity at the default (setting = 5?) or somewhat less.

If someone wants help with this, PLEASE ask one of the Instructors or experienced pilots. This is a serious issue and everyone is responsible to ensure that injuries do not occur due to misunderstood technology or lack of attention.
« Last Edit: July 24, 2018, 07:37:01 AM by Deerslayer »
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Offline Deerslayer

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Re: Throttle Cut - Belt and Suspenders
« Reply #1 on: July 24, 2018, 07:36:13 AM »
Even with the normal Throttle Cut set up properly (refer to previous posting), some folks are concerned about having  additional protection to ensure that when perhaps their Throttle Cut switch gets bumped while the Throttle stick is partially advanced, the motor will not activate. Not a bad idea for those times when you may be working around the plane on the bench yet it is not convenient or feasible to remove the prop, tie down the aircraft, disconnect power to one of the motor leads, etc.

Here is a very simple solution that will take you about 2 minutes to set up. This is specific to Spektrum but may be similar for other brands:

Choose a switch that you wish to be your secondary means of disarming the Throttle channel. Set up a Mix:

THR > THR
Rate: -100% -100%
Offset: -100%
Trim: Inh
Switch: Switch D ( for example)
In the next line, darken whatever box(s) representing the switch position(s) where you want this safety cut-off to take effect.

Refer to the attached screenshot.

As long as (Switch D here) is in one of the positions (1 or 2 in this example) where this Mix is active, you have disabled the Throttle stick from control of the Throttle Channel. You should have already set the Throttle Trim = 0, via the Trims Menu, so there is no way to move the Throttle Channel away from its -100% or lowest position. Even if you bump your normal Throttle Cut switch. In order to power up the motor, both switches will have to be set in the correct position (0 in this example).

This secondary disarming switch can be either 2-position or 3-position. Just set the position(s) where you want it to disable the Throttle stick.

However, none of this matters if you fail to use it!
« Last Edit: July 25, 2018, 09:35:54 AM by Deerslayer »
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Offline Deerslayer

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Throttle Cut - Some Suggestions
« Reply #2 on: July 24, 2018, 08:36:41 AM »
Here are a couple of things which you may wish to consider:

1. Always use the same switch for Throttle Cut, regardless of the model. It should/will become part of your mental checklist for any time you handle a model and will be foremost in your mind if you need to quickly kill a motor.

2. On Spektrum radios, I use the A switch, which some folks think of as the "Gear switch" - it may even be labelled as such on some radios. It is easily reachable with my Throttle hand and it is fairly clear of other switches. To set Throttle Cut, this switch is pulled toward me. That way, if the radio gets bumped or I brush against the switch, it will not be released such that the motor can start.

3. But, what if you actually use the "Gear switch", either for retracts or, as is sometimes the case, the so-called Gear or 5 Channel is dedicated to being the Mode switch on a stabilizer or other device? Well, the H switch, over on the other side may be a good second choice. A better solution, I think, is to do a Channel Assign and move that channel's controlling switch over to another switch.
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Offline Wilf

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Re: Throttle Cut - A Critical Item!
« Reply #3 on: July 25, 2018, 08:25:48 AM »
I sent an E-Mail to Doug of GRAUPNERUSA asking if it was possible to program the throttle cut switch to be mixed with throttle stick position at low throttle before the throttle cut would rearm the motor.


Doug’s response, “COOL IDEA, I WILL WORK ON IT”.

Offline Wilf

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Re: Throttle Cut - A Critical Item!
« Reply #4 on: July 31, 2018, 09:55:13 AM »
So far Doug from GRAUPNERUSA was not able to find a quick solution. He was able to use two switches before the motor was armed, but if the throttle was not at zero the motor still ran.
I have been using logic switches to emulate an “And” function with my cutoff switch and low throttle. It works, sort of. The motor will not arm until the throttle is at zero.  The problem, as soon as you advance the throttle, the and function is no longer valid and the motor stops.


Any ideas people???


I have not given up quite yet....