Breaking News Vtx Tail Blades In Development

ChopsyWA · Mar 18, 2017

Just like the VTX main blades, here is the initial rendering of the up n coming VTX 107 Tail blades.

This info taken from HeliFreak:
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Hey Folks - welcome to our new thread specifically for VTX Tail Blades.

Here we'll keep you up to date on tail blade development, design, engineering and production updates. Plus welcome your comments and requests of course!

With the engineering and initial graphic design complete on the new VTX107X5 tail blade, I asked and got approval from VTX to put up a couple renderings of the new blade, and talk just a bit about its development. Our tail blade design effort was really launched last summer, with work beginning here while wrapping up design on the 557 main blade.

Why 107mm on the tail blade you ask? Because 105 comes up short on thrust on 700 class heli's so often and 110 is too big - and of course it ends in a "7" Plus our aero thrust analysis shows a 13% improvement in fully developed static thrust compared to the 105mm blade span. All good!

So what you see here will be the starting point for our first flying prototype and represents 5 major design iterations following the initial planform & airfoil layout. Due to the environment a tail blade runs in, and due to the extremely high inflow velocities tail discs generate, a whole new dynamic analysis methodology was developed to direct-design this aerodynamic platform. We do want some visual synergy between the current VTX main blades and the tail blade, so planform shape is similar, but very much re-proportioned for the dynamic thrust environment tail systems run in. But don't let that fool you - this isn't simply a scrunched down main blade - its another completely clean sheet "data driven" design that's optimized for a very specific set of operating parameters. And as you might suspect, our tail blades will also employ mission specific airfoils across the entire tail blade family.

We're going to have a few flying prototypes of these built and test flown. As with all VTX products, it will be put through the wringer in an extensive flight test program on the Logo700.

This is really an experimental blade for now, with all new airfoils and of course a heavily massaged planform shape. It embodies many of the fundamental design principles used on our main blades.

There are some new twists included here as well: all new mission specific VTX1125TR airfoil; active boundary layer control; and a thickened trailing edge. While the blade you see here is fully symmetrical I'm also pushing hard to test some non-symmetrical airfoils as well.

All exciting stuff - initial thrust estimates are off the chart on this blade. I'm not going to release numbers until we fly them, but sure looks like it will make any and all tail thrust issues completely disappear even in the most demanding maneuvers.

Stay tuned ... blade molds will be cut soon!

Bill
VTX aero engineer
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http://www.helifreak.com/showthread.php?p=7317036

smakmeharder · Mar 19, 2017

HMMM... i wonder how this profile will affect hard stops. Also what are the ramifications in a tail first hurricane? How will gains be affected. Will it kickoff sooner for the same RPM?

ChopsyWA · Mar 19, 2017

smakmeharder said: ↑

HMMM... i wonder how this profile will affect hard stops. Also what are the ramifications in a tail first hurricane? How will gains be affected. Will it kickoff sooner for the same RPM?
Click to expand...

Plenty of information being posted in the thread on HF.

I wouldn't worry, these are the only blades that are engineered for purpose (every other blade is just a pick of a NACA profile and then tested). I am sure they know what they are doing and will conduct extensive real world test as they did with the mains.

VTX blades are designed for each size.
Every other blades manufacturer starts with a NACA profile, test it on a starting size, then just scales the design for every other size. VTX design each blade size from a clean sheet. The only blades being designed by an actual aerodynamics engineer.
Hence why they take time to be released and are a bit more expensive than other blades, fully engineered and tested for around two years before the market sees the blade.

ChopsyWA · Jun 26, 2017

smakmeharder · Jun 27, 2017

Boy can this dude fly... WOW. The tail seems to have control even during slow manoeuvres. I wonder if the blades actually "feel" any different. The claim of extra tail thrust is an interesting one. I take that as more responsive.

ChopsyWA · Jun 27, 2017

From HeliFreak, Jonas review from the previous posted flight vid:

Johnny31297;7396658 said:

VTX 107 Test Report

“Hey Jonas - I'm flying 2 Frankfurt trips next month. If you would be able to meet, I would enjoy talking with you in person.” This is how it all started. Fast forward a month, I’m at the Karlsruhe main station to pick up Bill, VTX’s aero engineer, who brought along the very first flyable prototypes of the VTX 107 tail blades for me to test. I don’t think I have to mention how excited I was!

Disclaimer, VTX doesn’t pay me in any way to write this report, they didn’t even ask me to write it in the first place. Bill just said he’d be happy if I did so, and I think it’s the least I can do for him after he trusted me with his $30,000 prototypes! He also asked me to be completely honest on the findings of our testing and include everything we find, which I will attempt to do here, though there really isn’t anything negative to say.

[IMG640]https://www.helifreak.com/attachment.php?attachmentid=712543&stc=1&d=1498153058[/IMG640]

Let me start by saying a couple words about the blades. First off, these obviously are prototypes, and therefore may still be subject to change after undergoing more testing with different helicopters and flying styles. The testing we did was based around finding things to improve on, finding the blades’ limits and evaluating their flying characteristics, so you’ll read a lot about how they behaved in especially demanding maneuvers, as you can assume they did behave completely predictable and stable in the normal flight envelope if not mentioned otherwise.

The X-5 prototypes I got to fly were hand built by Bill, and he did an amazing job if I may say so. They were built in a very similarly way compared to how Fun-Key does it, so I would expect similar results in terms of torsion- and flapwise stiffness on the production blades, leading to really close flying characteristics to what you’ll find in this report.

What these particular prototype blades don’t have is paint or a gel coat, but they will very likely still be one of the lighter blades on the market when painted. As far as I recall, there will be no need for Fun-Key to use lead on them, which they do in most other blades to adjust their lead/lang angle.

I tested several other tail blades in the past, of which RotorTech 105mm were by far my favorites. They provide good thrust while still remaining fairly quiet, so these are the reference I’ll be comparing the VTX 107s to.

Here’s a picture for comparison with other blades:

[IMG640]https://www.helifreak.com/attachment.php?attachmentid=712540&stc=1&d=1498152519[/IMG640]

Important testing parameters:

Helicopter: LOGO 700

Main blades: VTX 697

Collective pitch range: +-13°

Weight: 5.3kg rtf

Tail deflections: 45° CW/40° CCW

Tail servo: Futaba BLS256HV at 8.4V

Flybarless: VBar Blueline Fullsize 6.0.7

Climate: 34°C ambient temperature, 70% humidity, 1001mbar air pressure.

Flight Testing

1000rpm (5000rpm tail)

Starting out with low rpms, the first thing that stood out to me was that the VTX felt a lot crisper off center than the RotorTechs. At that low of a headspeed, you usually have to be careful about what you do with your tail rotor, especially when flying sideways in a manner that drags the tail rotor behind. The VTX held the tail in place quite a bit longer when doing sideways loops or funnels. Another thing that is crazy is, that although they really have to work hard at this rpm, I never heard them stall. Despite running this low of an rpm (at which the tail will naturally be driven into its extremes quite easily by anything using right rudder under power), they provided way better authority in situations where the tail has to deliver more thrust than it actually can.

Good example: A piro stop from a full left rudder piro would take RotorTechs about 180° until the heli reverses, while the blades would completely stall while slowing the heli down. The VTX actually took less than 90° to stop the heli in the same situation, and more importantly, there was no apparent blade stall during the whole event. They start getting noisy when you do that, but they don’t lose their “grip” in the air.

1400-1600rpm (7000-8000rpm tail)

The performance here was beyond what RotorTech blades could do as well. The VTX 107s produced more thrust and had a way higher off-center acceleration as well. This rpm also gave us a slight heureka moment.

I was doing fast sideways loops, continously increasing the collective with each loop to increase the load on the tail. As soon as I hit full collective (13°), the tail wasn’t quite up to the task anymore and started lagging behind. The thing here is, the blades didn’t stall. I still felt the thrust being there, it was just somehow limited. I went ahead and gave it full right rudder the next time it happened, which confirmed that the cause was purely mechanical, the LOGO 700’s tail can “only” do about 45° CW. Combine that with the high torque, inflow velocity from the left and the fin trying to weathervane and you just hit a limit at some point. This time it was the mechanics- the blades would have been up for it.

Bill said that, if the mechanics allowed it, we could go way past that pitch angle without stalling, which would solve this issue. For comparison, we repeated the test with RotorTechs, which didn’t even hold the same kind of loop at 3/4 collective (~9.5°), they stalled and the tail started to feel loose and turn around.

1800rpm (9000rpm tail)

This is where I found the blades to shine the most and bring me the most benefits for my flying style. Running 1800 with RotorTechs, I sometimes felt like the tail power wasn’t quite there. It would sometimes hang for a short moment, sometimes stall and get really noisy before starting to move.
Well, the VTX increased the performance so far that the tail felt like, in comparison, it was running RotorTechs at like 10,500rpm. They straight out never gave up, no matter what I tried. Huge backwards loops, sideways loops, funnels, piroloops with full right rudder and high collective, piro pogos with reversals to right rudder at the lowest point, the blades didn’t care. It seemed almost effortless for them to hold the tail, although they sometimes told us quite audibly that they were shoveling a lot of air around back there.

2000rpm (10,000rpm tail)

Granted, I have not yet managed to really blow the tail out at 2000rpm with RotorTechs 105s either. The main difference I found was that the VTX 107s stayed a lot quieter doing the same maneuvers I usually do, to a point where they never even seemed to get into an area where they really had to work hard, they just pulled through everything, really. The only times they got loud was in funnels and sideways loops that drag the tail rotor behind, yet I could feed the helicopter full collective in all maneuvers and the tail would just cope.

I spent two flights just thrashing the heli around, trying to do anything to upset the tail, the only things that really happened was that both flights ended in an overheated Tribunus 200.

Another thing I noticed was the seemingly higher base acceleration and reversing power of the blade. You move the stick, the tail follows quite a bit quicker than with conventional blades. Reversing from left to right felt easier, smoother and the tail stayed a lot quieter than with RTs.

[IMG640]https://www.helifreak.com/attachment.php?attachmentid=712541&stc=1&d=1498152537[/IMG640]

Summary

Making an educated guess, I’d say the VTX 107 prototypes were able to produce about 20% more thrust across the whole spectrum of 1000-2000rpm (5000-10000 tail), while remaining a fair bit quieter than the RotorTechs they were compared to. I suppose the thrust advantage goes quite a bit further, I assume up to 30-35ish%, if your heli can provide the additional tail throw. It helps extremely with authority at lower rpms, it felt kinda like the tail was running about 1000rpm more at all times compared to normal blades, similar to how the mains have a comparable effect. At high rpms, it takes the noise out of the tail and gives you a really connected, locked in and quick feeling.

The tail gains had to be dropped about 5 points in each bank, most likely due to the VTX’s thick, forward loaded airfoil having a better off center response than RotorTech’s NACA0012.

Now, what could be interesting, especially for helicopters with belted tails, is power consumption. These blades can, very similarly to how the VTX main blades work, extract a lot more power from the tail drive train if they have to. Other blades will stall and go “limp” and stop drawing more power at some point, while VTX never did that in this particular testing session. My take on the subject would be that they draw less power under normal circumstances, but can spike way above the power demand of regular blades if the additional thrust is required (remember, the power goes into thrust, not the noise a stall produces!).

Here's a video covering some of the flight testing at 1000 and 2000rpm:

TL;DR:

About 20% more tail power within the limits of the L700’s tail throw, more should be achievable with higher tail deflections. This gave us significant gains in authority and holding power especially for low rpm flying, felt like running 1000rpm more on the tail.

Quieter than regular tail blades, will only start getting noisy when pushed way harder.

Higher acceleration- and reversing power across the whole rpm range.

I hope this answers any questions that may arise. If not, let me know!

Jonas :hug:

[IMG640]https://www.helifreak.com/attachment.php?attachmentid=712542&stc=1&d=1498152668[/IMG640]
Click to expand...

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