The Bravo III Saga - The first 100 flights
Christmas in February!
After a long impatient wait, two packages arrived on the 5th of February: The RFT Bravo III, including battery charger, ordered on the 14th of January (5 working days for PayPal to process the cash payment, plus another 10 for shipping). The S300 kit was faster: Ordered on the 27th of January and it arrived within 7 working days. Everything arrived in good order.
The Bravo was well-packed and survived its longest flight unscathed.
I was first struck by how light/insubstantial the Bravo III (30g) felt, cetainly in comparison to the S107 (38g). Picking it up by the side windows, I could feel the thin plastic "give". Both the upper and lower halves of the flexible tail fin were slightly wonky. The landing gear is highly elastic, bending under the slightest pressure. The scale-look MD500 fuselage looks good, with a tight fit between the two halves, except for a rather larger gap on the underside of the tail boom, just aft of the "turbine exhaust". Nine Eagles saw fit to include nice little details like steps on the landing gear and "hinges" on the doors. Less impressive was the flame-pattern paint-job's smudgy edges.
The 2.4GHz Tx felt like a DX8i in comparison to the IR controller of the Syma, but with similar weighting on the control sticks. Both the battery and charger were smaller than I expected, and they met as soon as the useless battery cover was removed. Meanwhile I read through the comprehensive English manual. As soon as the charger's green light went out, it was time for flight #1!
The pre-flight check was simple: I pressed down on the right stick (cyclic AFAIK) to activate full-rates, and moved the servo's through their full range of motion to listen for binding (nada). Another click on the right stick and we were back in half rates mode and I slowly spun the blades up. The bottom rotor started turning at 4% throttle, top at 7%. The Bravo started drifting at about 25% throttle and lifted off at 40%. Bloody heck does this thing make a racket! Spooling up, the Bravo sounds just like a real turbine heli. Well, in my imagination it does. Either way, it is significantly louder than a S107, so much so that I've taken to wearing ear plugs when flying in my small office...
Despite reading reports about it, I was still surprised by the model's tendency to drift backwards during take-off. I've since learnt to counter with a bit of elevator, but somehow the Bravo always seems a bit tail-heavy. Hard landings usually ends with the model resting on its fragile tail fin.
The first couple of charges were consumed by trimming. This process took the sliding trim indicators a handful of clicks away from their centre positions, as shown on the functional LCD display. Especially that of yaw trim. This called for sub-trim mode, accessibly by five consecutive clicks on the black button on the back of the Tx, just below the aerial. A short beep, and all trim sliders jumped back to the middle. In sub-trim mode, all normal flight functions are available, with the exception of yaw. Clicking the trim buttons affected the model, but did not show on the sliders, giving equal space for adjustment on both sides.
Despite all the options for adjustment, I struggled to find a neutral position for the gyro (yaw). It seemed as if the step were too big: It was either slowly rotating to one side, or the other. Compounding the issue was the fact that on the Bravo, like the S107, battery power affected yaw. As the battery winds down it needs more and more clicks of right yaw trim to remain neutral. Lowering the gyro sensitivity (sub-trim > throttle trim) yielded a significantly faster piro rate, and seemed to widen the "yaw-neutral window" a bit. I've kept on tweaking the trim (yaw and gyro) until I've gotten to a workable setting, but it isn't a case of "set it and forget it". Overall I'm not overly impressed by the ability of the Bravo to hold its heading. Certainly not compared to the S107, which feels comparatively "locked-in".
The stock 110mAh battery arrived charged to 3.9v, a safe voltage for longer term storage.
The MIA S-300 canopy, frame kit and medium viscosity CA arrived within 7 working days.
Although the Bravo looks bigger, it weighs 27% less than the S107.
Once trimmed, I started flying around my living room. This was where the light weight and general sensitivity started to pay off. The Bravo feels "alive": Compared to the S107, it is highly responsive and reacts instantly to input. The "4th" channel is a welcome addition, adding a "real helicopter" look and feel to the model's flight. The Bravo feels rather powerful and I had some difficulty holding a steady altitude with its stepless hair-trigger throttle. Giving yaw input with the left-hand stick, while maintaining a steady throttle, proved to be a challenge.
Starting from the middle position on the yaw trim slider, the model needed a single rightwards click towards 8 minutes of airtime, before increasing rotation indicated low battery power.
Recharging the stock 110mAh battery takes 30 minutes, meaning that the Bravo can fly for around 15 minutes per hour. That is 50% more airtime per hour than the S107, where 50 minutes of charging = 5 minutes of flight, giving 10 minutes of airtime per hour. Easily the best initial aspect of Bravo ownership IMO.
After 20 flights I felt that I had the hang of it and I could not resist trying the higher-rate advanced mode. It made a heck of a difference to fast forward flight (FFF) and I experienced my first blade-strikes, with the poor Bravo repeatedly fluttering to the ground. I was not to be deterred though and soon started experimenting with a combination of aileron and rudder, yielding massively increased speed with a corresponding decrease in control. The inevitable crash resulted in a smashed canopy and a dramatic loss of trim. I tried countering the damage with a liberal helping of sub-trim, but ended up with clear Toilet Bowl Effect (T.B.E.) Upon close examination, I found that the plastic swash plate had come partially unseated. A couple of seconds with a pair of needle-nose pliers later, it was a simple matter of re-trimming and the Bravo flew as good as new!
Around the half-century mark, the Bravo and I started to understand each other a bit better. I could take-off, smoothly fly wherever I aim and land with a minimum of fuss. The Tx was permanently left in advanced mode, and I've found my control of the sticks improving. There is still a heck of a lot of room for improvement, but my enjoyment has increased exponentially with experience.
Switching to the S107, I was acutely aware of the throttle stick being restricted to a single plane of travel, and I sorely missed the aileron. The Syma was still good fun though: Smooth, stable and virtually silent. By this time I had built up enough confidence to try CD-case spot landings, though it was an uphill battle to begin with...
Despite, or perhaps because of my new-found confidence, the Bravo suffered crash after ham-fisted crash. Currently the model 'bowls lightly but noticeably, making spot landing tricky, to say the least. The rotors spin with a definite vibration, leading me to believe that the notoriously fragile inner-shaft is bent, which I've duly ordered along with a new swash plate and a linkage set.
After almost 100 flights in the hands of a beginner, the B3 is bowed, but not beaten.
Like a (non-German) European car, the B3 has systematically jettisoned superfluous parts, but gamely refuses to give up.
The high-cap Hobby King battery (150mAh) compared to the stock item (110mAh).
The arrival of 8 high capacity batteries (all charged to +- 4v) from Hobby King, exactly one month to the day after ordering, has shifted the airtime bottleneck to motor temperature. Before use, the too-large connectors had to be sanded down to fit the helicopter. To accomplish a good fit, I simply sanded down the plastic connector's 3 side (excluding the side with the actual metal connection), rounded the leading edges and removed the key-strips. Test fit often to ensure a good match!
Once the spares arrive, hopefully curing the TBE, I'll proceed to transform the sub-micro MD500 into a S300. Sylvia, whom I've been communicating with at MIA, has pointed me to instructions on their website. Combined with Mr Donaldsneffe's pics, I have a good idea of how the build is supposed to go.
I would like to retain the stock battery connector though, so I might have to deviate slightly from the plans. And given my poor safety record, I'm slightly concerned about the longer-term survival of the tail boom. Oh well, one way to find out!
Last edited by Quagga; Feb 16, 2011 at 07:16 AM.
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