Goes up - doesnt come down. Carbon Cub

[Upkeep]

Hi Folks

 

Ive been enjoying my Carbon Cub for the past couple of weeks ( no crash so far !! )  Plenty of circuits and bumps. 

 

Ive been flying it on intermediate and with full throw. The machine flies like a dream, straight as a die from the box however when its flying level it goes up with up elevator but when I input some down, it doesn't go down ?

 

To land I find Im having to turn and throttle right back to get the thing down. Ive got used to it now but wouldnt mind it coming down a bit more aggressively when I want it to 

 

Any ideas ? 

 

Should I bring the ( battery ) CG forward and trim the elevators. 

 

Bones

[MattyB]

Sounds very strange - I assume this the Hobbyzone CC with the Spektrum SAFE / AS3X stabilised receiver?

 

 

If so, have you tried flying it in a different mode and seeing if it does the same thing? I suspect this is because you have it in a mode where it doesn't want to let you nose dive it under any circumstances...

 

 

Edited March 5, 2021 by MattyB

[Upkeep]

Yes it has the safe stabiliser but im flying in intermediate. I should have some authority in that setting ?? Im hesitant to switch to full on just yet, suppose I could for a second or two to see what happens ?  I get tons of rudder and aileron and it climbs very well if I whack on full up, it just doesn't want to come down  ? 

Edited March 5, 2021 by Upkeep

[MattyB]

1 minute ago, Upkeep said:

Yes it has the safe staibiliser but im flying in intermediate. I should have some authority in that setting ?? Im hesitant to switch to full on just yet, suppose I could for a second or two to see what happens ? 

 

Check your instruction manual, but yes, in intermediate I would certainly expect you to be able to push the nose down below the horizon, perhaps to a maximum angle but you should be able to do it nevertheless.

[Upkeep]

Im thinking I need to push the battery forward a bit and trim the elevators up ? 

[Upkeep]

I havent fitted flaps on my cub 

[J D 8]

  Just something to check, is the servo arm at neutral [ or near 90 degrees to servo body ] when elevator is level.

 

  PS we have a recovered practice Hiball outside the local airfield caff. 

 

  

[MattyB]

This is from the instructions - looks like it self levels below 50ft even in intermediate mode....

 

Edited March 5, 2021 by MattyB

[Chris Bott - Moderator]

2 hours ago, Upkeep said:

Hi Folks

 

Ive been enjoying my Carbon Cub for the past couple of weeks ( no crash so far !! )  Plenty of circuits and bumps. 

 

Ive been flying it on intermediate and with full throw. The machine flies like a dream, straight as a die from the box however when its flying level it goes up with up elevator but when I input some down, it doesn't go down ?

 

To land I find Im having to turn and throttle right back to get the thing down. Ive got used to it now but wouldnt mind it coming down a bit more aggressively when I want it to 

 

Any ideas ? 

 

Should I bring the ( battery ) CG forward and trim the elevators. 

 

Bones

I don't know the model but that sounds a good description of one of the first things an instructor would teach a pupil. 

That contrary to what you'd think, elevator controls aircraft speed and throttle controls height. 

OK that's very simplified, but to explain, think of it like riding a bike. Pulling up elevator is like going up a hill, you'll slow down. As lift is related to speed, you'll not only slow down but you'll get less lift so won't climb as much as you'd think, maybe not at all. 

Putting in down elevator increases your speed and lift. The faster you go, the less likely you are to dive. 

 

Using throttle though, cut that and any slowing down will reduce lift and you'll start losing altitude. 

 

It's a control interaction that you'll need to get used to. 

[Don Fry]

Plus  1. 

[MattyB]

58 minutes ago, Chris Bott - Moderator said:

I don't know the model but that sounds a good description of one of the first things an instructor would teach a pupil. 

That contrary to what you'd think, elevator controls aircraft speed and throttle controls height. 

OK that's very simplified, but to explain, think of it like riding a bike. Pulling up elevator is like going up a hill, you'll slow down. As lift is related to speed, you'll not only slow down but you'll get less lift so won't climb as much as you'd think, maybe not at all. 

Putting in down elevator increases your speed and lift. The faster you go, the less likely you are to dive. 

 

Using throttle though, cut that and any slowing down will reduce lift and you'll start losing altitude. 

 

It's a control interaction that you'll need to get used to. 

All true, but the difference here is that the SAFE system is also actively fighting down elevator input when the model is below 50ft. I’d suggest next steps should be the servo test suggested by JD8 to check the down movement available, followed by taking it up high and switching to experienced mode (assuming the OP is ready for that). Push a quick burst of down in and see what it does - hopefully it will give the desired nose down attitude.

[Chris Bott - Moderator]

OK yep I see that. So what is SAFE doing in intermediate mode? It is still maintaining straight and level below 50ft? If so then the only way to reduce height is by reducing throttle? Isn't it?

[EarlyBird]

15 minutes ago, Chris Bott - Moderator said:

OK yep I see that. So what is SAFE doing in intermediate mode? It is still maintaining straight and level below 50ft? If so then the only way to reduce height is by reducing throttle? Isn't it?

Yes and that is what I was taught to do, SAFE is forcing the right way to land. Is it not?

[MattyB]

1 hour ago, Chris Bott - Moderator said:

OK yep I see that. So what is SAFE doing in intermediate mode? It is still maintaining straight and level below 50ft? If so then the only way to reduce height is by reducing throttle? Isn't it?

Yep, seems that is almost certainly the case.

 

1 hour ago, EarlyBird said:

Yes and that is what I was taught to do, SAFE is forcing the right way to land. Is it not?

Yes and no. If you only fly calmer weather conditions at larger, open sites then yes, this is a good technique. However, if you fly in higher winds and/or at sites with more limited approach options you may need to come in steeper and faster to avoid issues with wind gradient, rounding out positively nearer to the ground before letting the excess energy bleed away. As a pilot who learned to fly on the slope I learnt this early - nose level constant AoA approaches can easily end in disaster when you have no power source to get you out of trouble. I still tend to land my power models in this “slope style” too in anything more than a gentle breeze, I guess it is too deeply ingrained to be train out now!

 

Edited March 5, 2021 by MattyB

[Upkeep]

As I understood it, SAFE mode works when there is no input from the pilot ??  ie, if you panic and let go of the sticks it will level off for you.

Thanks folks, I will have a look at all those points raised. 

[EarlyBird]

9 hours ago, EarlyBird said:

Yes and that is what I was taught to do, SAFE is forcing the right way to land. Is it not?

SAFE is forcing a novice the right way to land in a light breeze. It's absolutely true what @MattyBsays in that when the wind gets up down elevator is required with power in order to land. I never had to do that as a novice because my Instructor always landed for me when I started flying RC.

 

@Upkeepyou are doing amazingly well and obviously having fun. ?

[David Davis]

11 hours ago, Don Fry said:

Plus  1. 

Plus 1 from me too.

[Frank Skilbeck]

I have had a few newbies at the club with these types of model, and while they are very good in assisting the flight, they will maintain the models attitude when you take power off, and with power off you often needed to push the nose down to get the model to penetrate, if you applied power all it did was maintain height. Whereas with a non-stablised model taking the power off usually results in the model adopting a nose down attitude, in fact some of the old fashioned IC trainers I have flown required you to hold in some slight up to slow the model down on approach.

 

I am with Matty too, I often tell beginners that they need to get a slope soarer and get on the slope if they really want to master elevator control, when I was teaching my son to fly he came on in leaps and bounds once he started slope flying.

[Ron Gray]

47 minutes ago, Frank Skilbeck said:

I am with Matty too, I often tell beginners that they need to get a slope soarer and get on the slope if they really want to master elevator control, when I was teaching my son to fly he came on in leaps and bounds once he started slope flying.

 

Not so good if you live in (south) Norfolk!

[MattyB]

4 hours ago, Upkeep said:

As I understood it, SAFE mode works when there is no input from the pilot ??  ie, if you panic and let go of the sticks it will level off for you.

Thanks folks, I will have a look at all those points raised. 

No, in beginner and intermediate mode SAFE is limiting bank angles at all times as well as self levelling when sticks are released - see the screen grab from the manual further up this thread. Even in experienced mode it is doing the sticks released panic recovery.
 

Personally I find the fact there is no mode available were the functionality is completely off is somewhat cynical from HH - it means beginners can’t transition to a fully unstabilised model when you are ready for that unless you buy a new plane, or at least for an alternative RX. 

[Geoff S]

4 hours ago, Ron Gray said:

 

Not so good if you live in (south) Norfolk!

 

Surprisingly, there are some quite steep hills in 'flat' Norfolk.  One near Holt had us on the granny ring on our tandem.  I seem to remember a few hills round Thetford when we lived there for a year but I was working most days then and didn't get much chance to explore.

[Ron Gray]

Yes, the coast is good but still 1 ½ hours drive to get there from South Norfolk. Not a lot around Thetford that I’m aware of, I live about 9 miles from Thetford!

 

Norfolk should never be described as flat, I always say ‘undulating’.

Edited March 6, 2021 by Ron Gray

[Frank Skilbeck]

On 06/03/2021 at 10:33, MattyB said:

Personally I find the fact there is no mode available were the functionality is completely off is somewhat cynical from HH - it means beginners can’t transition to a fully unstabilised model when you are ready for that unless you buy a new plane, or at least for an alternative RX. 

 

Matty, I think you have mis-read it, in experienced mode the self levelling is off, you have to switch to beginner mode and release the sticks for the model to self level. I know this as we had a beginner turn up at our field with one, he switched into experienced mode, got into trouble and couldn't find the mode switch quick enough to stop terra firma from terminating the flight. But for the A test you would have to use a different Rx or model as even in experienced mode it still does wind dampening, but as a lot of these models are less than the 1kg min weight limit they can't be used for the A anyway.

[Gary Manuel]

51 minutes ago, Frank Skilbeck said:

 

Matty, I think you have mis-read it, in experienced mode the self levelling is off, you have to switch to beginner mode and release the sticks for the model to self level. I know this as we had a beginner turn up at our field with one, he switched into experienced mode, got into trouble and couldn't find the mode switch quick enough to stop terra firma from terminating the flight. But for the A test you would have to use a different Rx or model as even in experienced mode it still does wind dampening, but as a lot of these models are less than the 1kg min weight limit they can't be used for the A anyway.

Matty was correct about beginners not being able to transition to a fully unstabilised mode then if it still has wind dampening in experienced mode.

[MattyB]

6 hours ago, Frank Skilbeck said:

 

Matty, I think you have mis-read it, in experienced mode the self levelling is off, you have to switch to beginner mode and release the sticks for the model to self level.

...But for the A test you would have to use a different Rx or model as even in experienced mode it still does wind dampening...

Fair enough, but I still feel that you should always have the option to turn off all stabilisation if you want. Yes I get it wouldn’t be allowed in the A-test, but it would still be useful to an advancing beginner to be able to turn off the stabiliser fully to understand what the system is doing for them and prep them for unstabilised models.