Rate switches

[Cliff Bastow]

I can only speak from my own experience but non of the military a/c I worked on had anything like rate switches, what you had was what you got! However on the Hunter I remember the whole tailplane incidence was electrically movable for trim adjustments and this could be switched in to activate with elevator movement so that say as you pulled up elevator the tailplane would also move leading edge down so giving more nose up pitch. I believe this was used for ground attack on the later marks to make the elevators more effective when it was switched in.

[Bob Cotsford]

I suspect that full size aircraft don't tend to need rates as they are thoroughly tested and control response tuned for the designed flight profile. I wouldn't have thought that they would generally operate over such a wide relative speed range as a model.

Then again, when the Hunter et al were in service weren't we flying bang-bang reed systems with fixed movements? Do the more recent computer assisted aircraft run 'fixed rates'? I wouldn't have thought so.

[Cliff Bastow]

Again from my experience of the Tornado, which of course is computerised and fly by wire, The flight control systems ensure that the pilot always gets the same response for a set joystick movment irespective of the many variables, speed, height, fuel load, weapons load and a/c configoration such as u/c, flap, wing sweep angle airbrake position etc.

[Cliff Bastow]

This made control checks much more complicated for us ground crews. On the Hunter it was much as you would do on a model, one man in the cockpit moving the controls and one measuring control surface deflection.

On the Tornado you had a whole list to go through as say the taiplane would have to move a certain amount in the clean state, and different amounts if say the flaps were down or the wings swept and any of the possible combinations of all the options so you had a lot more options to check.

[Bob Cotsford]

so it had rates controlled by flight modes automatically set according to the flight envelope? Bet you could program that in the Taranis, what do you say BEB?

[Cliff Bastow]

Hi Bob,

Yes basically you are correct in that it had rates controlled by the computer, but they are not just high and low but infinately variable (within the limits set physically) Theoretically it is not possible to overstress the airframe as the computer would not allow it.

I am sure that with the advances in model r/c the technology could be incorporated in models, after all we now have telemetry sent between receiver and transmitter and I am sure someone cleverer than me could use this to make such things possible. Would we want it though? I suppose its a bit like those who like gyros and those who think it takes some of the skill away. You pays your money and takes your choice.

[Chris Bott - Moderator]

Cheating?

I think it's horses for courses and all down to personal preferences.

I know the pattern guys spend hours tweaking a model until it performs as they want. First mechanically, and then my adding mixes to take out any unwanted control responses.

I don't think you can draw a line and call one side of it cheating and the other not. It's up to us to enjoy the hobby as we see fit.

[Chris Bott - Moderator]

Posted by Bob Cotsford on 07/06/2014 09:43:28:

so it had rates controlled by flight modes automatically set according to the flight envelope? Bet you could program that in the Taranis, what do you say BEB?

Bob I just had a quick look and am surprised (as I am quite often) as to how easy his sort of thing is in Taranis.

The "weight" of a mix can indeed be controlled dynamically using a Global Variable. That GV could simply be throttle position, or it could even be derived from the models speed via telemetry. (Although I don't find the speed readings from GPS accurate enough to consider this viable - yet)

So yes, you could certainly have a "rate" which is proportional, and related to throttle, or flap position, or whether retracts are down - etc etc

[Bob Cotsford]

An ASI would be needed, a GPS wouldn't refresh fast enough to be much use. Possibly a vario connected to a pitot head? An accelerometer would be useful to limit max G.

Variable rates assigned to a slider or pot would be good for maidens where it would be useful to adjust the response on the fly. In a similar vein for maiden flights I sometimes slave elevator to a pot or slider for a way of making course trim adjustments.

[WolstonFlyer]

Up (away from me) low rates, down for high rates.

Same as a switch, down for On.

[Martin Harris - Moderator]

Posted by Chris Bott - Moderator on 07/06/2014 10:21:32:

]

The "weight" of a mix can indeed be controlled dynamically using a Global Variable. That GV could simply be throttle position, or it could even be derived from the models speed via telemetry. (Although I don't find the speed readings from GPS accurate enough to consider this viable - yet)

Whether or not GPS updates in real time, the information is practically useless for model control purposes unless flying in dead calm conditions. We often fly at wind speeds up to or even above stalling speeds (measured in un-accelerated flight, of course) so your GPS speed could easily show you at twice the stalling speed when close to or below the stall...

[Cliff Bastow]

The models speed would not be measured by GPS. It would come from a minaturised pitot static system as in full size. I know such things are already available, therefore you would get a true air speed reading.

I seem to remember an article in RCME about just such a system for measuring airspeed in models.

Porbabally my fault but I think we are getting a bit of the origional topic of this thread!

[Max50]

Jeti has a minature pitot sensor. One person was using it to alter his gyro gain above a certain air speed.

One of the first questions my instructor asked when flying my trainer for the first time was had i got rates set on a switch; when i said yes, he just flicked the switch,found high,and flew on that.

[Martin Harris - Moderator]

Posted by Cliff Bastow on 08/06/2014 06:08:37:

The models speed would not be measured by GPS. It would come from a minaturised pitot static system as in full size. I know such things are already available, therefore you would get a true air speed reading.

I seem to remember an article in RCME about just such a system for measuring airspeed in models.

Porbabally my fault but I think we are getting a bit of the origional topic of this thread!

Thanks Cliff, but Chris had suggested the use of GPS for sensing air speed which is the point I was trying to make. I have the Jeti ASI which has given me some interesting information and I'm thinking of getting the new Vario 2 to combine with it to give total energy compensation in a glider. Still vaguely on topic as GPS info was suggested as an alternative method of rate switching...