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Revolution Models . CarbonXtreme . Midland Helicopters

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Thunder Tiger Raptors 30-90 - Imperio > Can flying backwards blow out the tail?
 
 
Hummingbird3D
Veteran
Location: California

On the G3 sim I'm flying backwards a lot and fast. On my raptor 50 & 90 I'd like to do the same. My concern is would the tail blow out/fail if I fly hard backwards for a long time?
Raptor 50
gyro - futaba 401
servo - futaba 9254
Raptor 90
gyro - futaba 611
servo - futaba 9256

Fly It Like You're On The Simulator!
05-19-2006 Over year old.
 
 
flytech
Veteran
Location: Sunland, CA

Flying backwards for a long time is not an issue. If it's gonna blow out, it will usually do it in two main conditions I've seen - wind or high speed FBF.

The only bird's i've seen blow out were equipped with a gy240 or gy401 even though they were properly setup. I've also seen a couple 401's handle extreme FBF very well.

I've seen an R50/gy401 not blow-out - but after several crashes started blowing out. I've never seen a gy601, gy611 or csm SL720 blow-out - under any conditions (though I've never experimented with doing a poor setup and seeing if it will).
05-19-2006 Over year old.
HOMEPAGE  
 
 
SPB
Elite Veteran
Location: Athens - Greece

My 50 with 401/9254 and 92mm Radix tails has only once blow the tail in FBF with strong wind and this only when I was turning.

So far even with medium to strong wind had no problems.

The same day with the strong wind my 90 with 611 and 105 VBlades was holding the tail under all conditions.


Sotiris
myhelis.com Flying Team
05-19-2006 Over year old.
 
 
Heli88
Key Veteran
Location: Clarkston, MI

A 611 on your 90 now Sotiris! Very nice...
05-19-2006 Over year old.
HOMEPAGE  
 
 
SPB
Elite Veteran
Location: Athens - Greece

Hans

buddy that was a good upgrade


Sotiris
myhelis.com Flying Team
05-19-2006 Over year old.
 
 
spaceman spiff
Key Veteran
Location: Tucson

Been running 401 and a standard JR 537 servo and never had a blow out using 60 size tails trimmed down to 90 mm
05-19-2006 Over year old.
 
 
bperry
Senior Heliman
Location: Detroit, where we eat the dead

By blowout do you mean the gears break?? Or just that the tail lets go....
05-19-2006 Over year old.
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clever
Heliman
Location: South FL

Quote 
By blowout do you mean the gears break?? Or just that the tail lets go....



I'd like to know the same thing. I was just about to start trying FBF after alot of sim practice.
05-19-2006 Over year old.
 
 
Heli88
Key Veteran
Location: Clarkston, MI

Blowout means the same as let go! No damaged gears.
05-19-2006 Over year old.
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jwegman
Heliman
Location: Rochester, MN - USA

How about pirouetting during fast forward flight? Neither of my R50v2's @2000rpm with 401/9253{4} will provide a constant pirouette (will start slow, and swing fast at the end). Have I been mistakenly calling those 'blow outs'? The same with another like manuver - fff into knife edge with a 360 pirouette does the same thing.

Regards,
Jake
05-19-2006 Over year old.
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3d type
Senior Heliman
Location: Bridgeport,CT USA

if you bog the engine bad enough you will blow out the tail no matter what gyro you have, if the tail blades slow down enough the tail will blow out.

how'd the ground come up like that ?
05-20-2006 Over year old.
 
 
Jerry Sudimick
Veteran
Location: Connecticut

Jake,

Thats normal for the 401. Its related to it's programming logic. It will exhibit weathervaning characteristics while moving because it's priority is more tail suppresion and stop than constant piro -rate.

The 601/611's have two modes. F3C and 3D. In the F3C mode - the logic is similar to the 401. Suppression and stop. It will weathervane (fast slow, fast, slow) while moving or stationary in heavy wind.

The 3D mode prioritizes piro-rate. In other words, when you deflect the TR stick full left, the logic is.....he wants 400 degrees per second of piro rate. The gyro then modulates TR input to yield a constant 400 degree per second piro rate. No more fast, slow, fast, slow.

So what you see with a 401 is normal. If you upgrade to a 601 or 611 you can select the 3D mode to get rid of this characteristic.

Jerry
05-20-2006 Over year old.
 
 
Hummingbird3D
Veteran
Location: California

Yes, I do mean, do the gears break.
I have been practicing fast backward flight on the sim and I'm taking that to the field. I'm just unsure that going backwards so fast would cause the gears to strip or something. But then I suppose no one would ever be doing tail slides then.

Fly It Like You're On The Simulator!
05-20-2006 Over year old.
 
 
Al Austria
Key Veteran
Location: Gainesville, FL

Just to set your heli terminology straight, the term "blow-out" is synonymous with the tail/gyro "letting go" in backwards flight. In the occurance of a blow-out, the heli usually just whips around, nothing more.

Century Field Rep
Always remember you're unique, just like everyone else.
05-20-2006 Over year old.
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Colin Mill
Veteran
Location: England

The possibility of the tail blowing out in fast backwards flight depends on quite a lot of factors. The amount of heading lock gain the system will run is a significant part of it. I always assess the HL gain not by looking at the Tx percentages but, because servo arm length, servo 'gain' (angle change per microsecond pulse change) etc come into it, by looking a the heli heading change needed to get the tail servo to drive the linkage from full left pitch to fill right pitch and vice versa. Assuming you have a good tail pitch range (45 degrees right to 35 degrees left or there abouts) a modest HL gain is one where it takes a heading swing of about 80 degrees to cover this range (i.e. about 1 degree of tail pitch for 1 degree of heading swing). A high HL gain is one where you get between 2 and 2.5 degrees of tail pitch change per degree of heading change.

Bear in mind that even with a modest HL gain the gyro will get the full available pitch on for a heading error of about 40 degrees so any swing beyond this is due to a lack of adequate tail power to control the swing. The tail thrust varies as the square ofthe rotor RPM so a loss of headspeed can have a dramatic effect on the ability of the tail to hold.

If you are worried about the ability of your model to hold backwards flight I suggest you try the following check on the tail authority which is easily recovered from if the tail does not hold:-

Starting from a generous height dive the heli near vertically at full pitch to reach as near terminal velicity as you can. Use right tail to get the heli going left sideways and see if the tail will hold it there (recover with right cyclic if it does, and back cyclic if it doesn't!).

If it will hold then you have enough tail power to avoid a blow out so long as you maintain at least those revs. Try it, if you like, at reduced headspeed to see what sort of margin you have.

If you want to know more please let me know (I could bore for pages on this stuff )

Best regards

Colin (CSM)
05-20-2006 Over year old.
 
 
Hummingbird3D
Veteran
Location: California

Yes Coling I would like to know more.
In one part of your explaination are you describing an aileron flip?This morning I was working on the tail slides and backward flight more. The confidence/trust is getting there. I suppose that this similar to ( as good as a heli pilot you are ) after a crash, one tends to revert just a bit in flying ability.

Fly It Like You're On The Simulator!
05-20-2006 Over year old.
 
 
Colin Mill
Veteran
Location: England

Hi HummingBird3D

Well, the move I'm suggesting is really a high speed entry into a sideways loop. By yawing the heli right during the dive you are putting the maximum weathercocking force on and in the same direction as the main rotor torque so this is about the maximum load you can put on the tail. The high airspeed puts the bigest demand on the pitch of the tail as well because the blades have to reach before they can produce any thrust at all because of the speed at which the air is rushing into the tail rotor.

This brings me neatly to another point about the tail rotor for 3D flight. Because there can be significant sideways flight components to the manouvres it is better to have a fast rotating small diameter rotor than try to get the same tail authority from a large slow turning rotor. The small diameter rotor generates its thrust from shifting a small amount of air fast while the larger rotor gets it from shifting a large amount of air slowly. The small rotor is less affected by changes to the inflow speed - the sideways flight component. It is also less troubled by turbulance. The down side is that it is aerodynamically less efficient so it takes more engine power.

I think its well worth working on the tail linkage etc to pinch every last bit of tail pitch throw you can. Sometimes filing a bit of the inside face of the tail hub, the end of the pitch slider or the gearbox can allow a useful extra few degrees of throw to be obtained. Quite a lot of designes lack left tail pitch. Especially where a governor is being used you can't rely on the engine torque always being there to assist the left pitch so you need nearly as much left pitch as right.


See - I told you I could bore for pages on this stuff!

Best regards

Colin(CSM)
05-21-2006 Over year old.
 
 
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Thunder Tiger Raptors 30-90 - Imperio > Can flying backwards blow out the tail?
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