Finally Maidened! :) Ugly second spool up :(

[Groucho_]

Well, the maiden went really well…

On spool-up the machine did give a rotating kick as the head governing was passed from the Helijive to the SK-720. It's OK, but I decided there and then to switch to the Helijive governing, until the SK-720 and the helijive can 'talk to each other' and mesh the control exchange.

Unfortunately I didn't have the jive user manual, and I also didn't have any facilities where I could do this (and I also couldn't be arsed), so headspeed would have to remain SK-720 controlled for today.

Lift off was smooth, and although there was a bit of wind - enough to bother my 550 in the previous two flights - the TDR handled it as though the wind wasn't there.

The machine was equally stable both with and without the self-leveling function of the SK-720. In fact I only used the SL to help with fighting the wind.

It seemed so nicely tuned, that I went for a couple of aileron rolls and some flips and loops. These looked so much better on the TDR than with my 550… I've no idea why… The TDR seems not to lose altitude even if your rolls are not so well executed…

The nicest thing about the flight though has to be the sound. 1450 RPMs had a lovely growl to it...

Flew for seven minutes, then brought it down safely.

So onto the next pack. Now pay attention at the back… Remember when I mentioned the SK was governing and I wanted to switch to the Helijive, but had to leave it tale-quale for the day?

Well, that proved to be my undoing…

As I touched the throttle up from zero into the deadband zone, my friend and cameraman remarked that the camera had not yet started rolling. So I put the stick back to zero. Now keep in mind that the blades hadn't yet begun moving, but for the SK-720, that little throttle input was enough to register the beginning of a flight. And that return to zero was probably enough for it to go into what we'll call autorotation bailout mode… So what it did as soon as I fed some throttle, was to tell the Helijive to go to maximum ASAP.

The helijive doesn't take the amount of throttle into consideration on spool up - it always goes for a nice slow start. However after two seconds it probably passed head speed control to the SK, whereby the helijive instantly received something akin to a full throttle command, and proceeded to quickly accelerate the head speed.

This resulted in a seven-tooth loss on the main gear, and two ugly nicks in the main blades when they folded due to the speed and hit the blade holders.

Now here I'm assuming that the problem is due to the SK-720 not meshing nicely with the Helijive, but I suppose that it could also be the sole fault of the helijive - Though I doubt this. After all there is no bailout mode on mode 8 in the helijive, and that's what mode I was using.

So all in all, very satisfied with the maiden. Not so much with the second spool up.

Before I forget - Vibes were acceptable. (pic attached) Below 2 when just flying and hovering, around 3, peaking at 4 when doing everything else. One nasty spike at 9(!) and I have no idea why that is. This at 1450 RPMs though. I never got to try a higher speed.

I was so much looking forward to that second flight

[ZuvieleTeile]

The fact, that you regretted your HJ-SK-720 governing decision on the first spool-up is a first step to a sound decision making process. . .

I don't want to be a a mart ass here, but I have to agree with you Groucho.
Why not using your HeliJive's expensive and very safe features first and get used to the heli, before playing with all the electronic governing possibilities you have between SK-720 and HeliJive. . .

Oh, did I forget to congratulate you to your maiden . . .

[Groucho_]

Thanks ZT...

I forgot to attach the video so here it is...

TDR Spoolup 2 (0 min 10 sec)

[KidHeli]

Congrats on the maiden but hate the issue with the second spool up. As much as I like what I hear about the vBar gov I just really can't see the reason not to use the HJ gov... well at least for now. Maybe in the off season I might explore that option but then there is the hassle of a phase sensor and more wires.

At any rate though congrats again and welcome to the club my friend

[Groucho_]

Thanks Kid,

I'd have liked to use the SK-Governor as it has a few nice features included, but then again, I'd rather have a smoother spool up each time and eliminate the risk of a repeat occurrence...

Now I'm trying to embed that youtube video... Can't seem to remember how I did them before..

[Egroeg]

Forgive my ignorance, but what is the point of using the skookum gov, when the jive gov works just fine?
I must have several hundred flights on my TDR with the jive gov on, with absolutely no issues do far.

[KidHeli]

Originally Posted by Groucho_

Thanks Kid,

I'd have liked to use the SK-Governor as it has a few nice features included, but then again, I'd rather have a smoother spool up each time and eliminate the risk of a repeat occurrence...

Now I'm trying to embed that youtube video... Can't seem to remember how I did them before..

the way i do it is copy the link from address bar on the YT page where the vid is

[Groucho_]

Originally Posted by Egroeg

Forgive my ignorance, but what is the point of using the skookum gov, when the jive gov works just fine?
I must have several hundred flights on my TDR with the jive gov on, with absolutely no issues do far.

Ignorance excused...

Well the SK-720 Governor is a pro-active governor. It will adjust the head speed according to your collective input BEFORE reading the RPM data which results AFTER said input has been applied.

It also integrates with the tail holding, though I'm not sure if that bit is pro-active or not.

The SK also reduces collective when it detects that there could be a motor bog-out, though it can also do that with an RPM sensor attached and without the governor enabled.

In any case. it's Helijive governing for now for me...

Originally Posted by KidHeli

the way i do it is copy the link from address bar on the YT page where the vid is

I did that - Youtube might have changed something...

[Egroeg]

I have not managed to bog my TDR so far.
Honestly, but I pay attention to the helicopter while flying.
I know when I'm giving it a hard time so I have learned to back off when asking for too much.
I have respect for the model so I fly it with care.
I suppose the collective management...has to do with instances where people expect too much and would rather leave the management to the machine.
CSM had a collective management unit for Nitros...it was a gov too.

[AcidDrink]

Congratulations on your maiden.
So, from what you are saying, SK720 can activate bailout mode when not coming from throttle hold?

This is certainly not very safe "feature". It's not like it works on v-bar too.

[CyprusFlyer]

Congrats on the maiden, shame about the govenor issue but have to agree with the KISS approach and get the best out of that expensive ESC. Just started my build today so a long way to go. Great engineering, the main thing I am worrying about is getting the stickers on the canopy! Ah well, cracking on and hoping to learn from you guys.

[Groucho_]

Originally Posted by AcidDrink

So, from what you are saying, SK720 can activate bailout mode when not coming from throttle hold?

I'm not entirely sure if the behavior is due solely to the SK, solely to the Jive, or the combination of both SK and Jive, but yes, once throttle up is detected - even if it is still not enough to start the motor, then once throttle is reduced to zero, or throttle hold is activated (same thing for me) there is a preset amount of time during which the next spool up will be a quick spool up.

It's actually a good feature which I would like to have if it didn't strip gears when it engages due to user error.

I was aware of this behavior when bench testing, but it slipped my mind today...

[AcidDrink]

Originally Posted by Groucho_

I'm not entirely sure if the behavior is due solely to the SK, solely to the Jive, or the combination of both SK and Jive, but yes, once throttle up is detected - even if it is still not enough to start the motor, then once throttle is reduced to zero, or throttle hold is activated (same thing for me) there is a preset amount of time during which the next spool up will be a quick spool up.

It's actually a good feature which I would like to have if it didn't strip gears when it engages due to user error.

I was aware of this behavior when bench testing, but it slipped my mind today...

I see.
I'd remove 0 throttle curve from normal mode then and just use flat throttle curve and throttle hold to prevent accidents.

[Groucho_]

Originally Posted by AcidDrink

I see.
I'd remove 0 throttle curve from normal mode then and just use flat throttle curve and throttle hold to prevent accidents.

That makes so much sense in hindsight...

I could start normal mode at +5 or thereabouts, which would still be in the deadband zone, and even if I were to abort mid-spool up by bringing throttle stick all the way down, AR protection will not engage.

I'd just need to set up my DX8 'throttle is not at zero' alarm for when the TX is powered up.

Great suggestion. I'm implementing this one. Thanks!

[mkovalcson]

There are a couple other good reasons not to have a "normal" flight mode.

One I experienced personally but was lucky enough to pull out of and that was flying inverted and accidentally powering down.

Now I run straight throttle curves on all of my helis in all flight modes

[Groucho_]

Originally Posted by mkovalcson

There are a couple other good reasons not to have a "normal" flight mode.

One I experienced personally but was lucky enough to pull out of and that was flying inverted and accidentally powering down.

Now I run straight throttle curves on all of my helis in all flight modes

Oh, I'm not going to set my normal mode to a straight line though... Just not have it start at zero to avoid fast spool-ups.

I don't envisage a problem with me forgetting to switch to idle up before doing anything inversive...

[mkovalcson]

Originally Posted by Groucho_

Oh, I'm not going to set my normal mode to a straight line though... Just not have it start at zero to avoid fast spool-ups.

I don't envisage a problem with me forgetting to switch to idle up before doing anything inversive...

I didn't envision that happening to me either.... just sayin....

[thefrog]

Originally Posted by Groucho_

I'm not entirely sure if the behavior is due solely to the SK, solely to the Jive, or the combination of both SK and Jive, but yes, once throttle up is detected - even if it is still not enough to start the motor, then once throttle is reduced to zero, or throttle hold is activated (same thing for me) there is a preset amount of time during which the next spool up will be a quick spool up.

It's actually a good feature which I would like to have if it didn't strip gears when it engages due to user error.

I was aware of this behavior when bench testing, but it slipped my mind today...

A mix of congratulations and commiseration from me. My heart is leaning heavily towards
TDR nowadays, so who knows.. Maybe i'll get in line soon.

Regarding your mishap, I'm leaning towards a compatibilty issue between HJ and SK. I say this because I run SK gov on nitro and electric and I've found it will only do an auto bailout if the throttle is in an idle up position (as displayed in the SK software). I have, on numerous occasions, throttled partly up, then back to zero to check something. I've never experienced this issue. ESCs in question were Hobby Wing and Align.

[Groucho_]

Originally Posted by thefrog

I've never experienced this issue. ESCs in question were Hobby Wing and Align.

Now that I think about it, I have an SK governing with an Align ESC on my 550, and I never had this problem.

That is not to say that there was no fast spool-up, just that if there was one, it didn't strip gears and I didn't hear it...

I'll have to check the helijive on it's own (SK just feeding straight line throttle) and see if it still does this.

I'm leaning towards the incompatibility between the two units, or at least incompatibility between the units when helijive is on mode 8.

[marcosp]

Usually the point of full down throttle and bailout are different to avoid exactly this. The helijive's internal bailout works like that for instance. 0% will always do a slow spool up, 10% to 20% is still motor off but bailout upon raising the throttle. So, you normal curve can go to 0, you Hold to 15% and what happened to you would occur only if hitting hold and releasing it as soon as the blades stop. There is a timeout for this too, if you remain in Hold for 8 or 9 secs next spool up will be slow (which is too short for aerobatic autos BTW). On Vbar Gov the bailout feature arms after a few seconds of active governing, so going back to cero without having waited 10 or 15 seconds in governed speed won't have the bailout active.

I am pretty sure SK thought about this. Check how your SK works in this regard. After the HJ transfers governing to the SK it is in flight mode so don't blame it for doing a bailout after returning to low stick and back up without a power reset or what sounds to me as incorrect lower points on you Normal and Hold, it is supposed to do that. Maybe the SK doesn't work like this, don't know, but if it doesn't it's dangerous, and I doubt DK would release something like this. I have 3 720s but never used the Gov.

Hope you find the answer!