The XRB SR Lama Sky Robo From Hirobo by Francis ... - Sport Aviator

The XRB SR Lama Sky Robo 

From Hirobo 

by Francis DeNovio 

Helicopter flying is very different and looks like a lot of fun. I am far from the only RC airplane 

driver who thinks so; there are thousands. However, flying a model Helicopter is far different than 

flying an RC aircraft. Therefore, many fixed-wing pilots think of a helicopter as a victory of 

lubrication oil and horsepower over common sense. 

So much is different between the two disciplines. The pilot’s perspective is different, especially 

from the rear. Unlike aircraft, the helicopter requires continuous pilot input to remain airborne and 

this particularly applies to the left, or “rudder”, hand. Every time I try to fly a helicopter on any RC 

Flight Simulator, I learned that I would only be buying some owner of a helicopter parts store a 

new Mercedes every year. 

While helicopter parts are easy to obtain, they are not cheap and most beginning helicopter pilots 

would need a lot of them: Probably a whole of them. This single fact limits the number of new 

model helicopter pilots. That is until now. A recent advance in helicopter design has opened up 

the realm of vertical indoor flight to everyone with some fixed wing RC piloting experience. 

Photo 1 

The development of indoor, twin-rotor electric helicopters (photo 1) has made it possible to 

transition from fixed wing flying to whirly wings. These helicopters are extremely stable and easy 

to fly. Most any experienced RC pilot can keep one airborne without scaring everyone else in the 

same room. Well, with terrifying them anyway. 

Despite being easy to fly and not needing a tail rotor for direction, a twin-rotor helicopter does 

keep that left hand busy. In fact, the XRB helicopter teaches the same skills that will be required

to fly the more advanced single-rotor designs that might lay in the new helicopter pilot’s future. It 

also teaches that helicopters require a very gentle hand on the transmitter sticks. Helicopters 

respond quickly and decisively to every control input. This is another difference from fixed wing 

piloting. 

Photo 2 

Hirobo’s XRB SR Lama Sky Robo is marketed in the United States by Altech Marketing in 

Edison, New Jersey. Altech did a very good job packaging the helicopter both for protection and 

for sales appeal. Nothing was damaged in shipment and everything arrived safely. 

Photo 3 

When I say everything, I do mean everything. Photo 3 shows that attractive box’s contents. There 

are twelve, yes twelve, extra rotor blades. Three complete sets of the foam blades are included 

just in case the new helicopter pilot has a few misunderstandings with hard objects while learning 

to fly. Of course, the expected 7.4-volt, 720 mAh Lithium Polymer (Li-Poly) battery and its 120volt 

wall charger are inside as are all the tools necessary to assemble and tune the helicopter.

Photo 4 Photo 5 

But there are some extras that are unexpected. While the regular landing skids are fine for flying, 

new pilots sometimes land harder than they should. The XRB has special landing skid braces that 

are easy to install (photo 4). There is even a “trainer” landing gear (photo 5) in the package. 

Another unexpected item, but a welcome one, is the small black balancing stand used to confirm, 

or adjust, the balance of each rotor blade. 


One more unexpected item is a set of lighter weight “fly bar” weights. The fly bar, stabilizer bar, is 

the metal rod with the two weights attached in photo 7. Its function is to stabilize and adjust the 

angle of the top rotor blade‘s disk, thereby keeping the helicopter stable. Using the lighter weights 

on the fly bar makes the helicopter more maneuverable but also more sensitive and difficult to fly. 

For now, it might be a good idea to keep to the factory installed heavier weights. 

Photo 8 

The transmitter is the Hirobo model CHO3-F four-channel analog transmitter. The transmitter 

broadcasts on the standard RC aircraft frequencies, in this case 72.630, and is useable in any 

aircraft. The transmitter features servo reversing and trim on all four channels. It is powered by 8 

“AA” Alkaline (non-rechargeable) batteries. The batteries are not included.

Even though there is far more in this “kit” then would ever be expected, there is one notable 

exception. The battery charger included for the Lithium Polymer (Li-Poly) can only be used with 

120 VAC current. There is no 12-volt DC powered charger included. But since this is not an 

outdoor machine, that isn’t a real problem. 

Assembly 


Although the XRB is supplied ready to fly, it is a good idea to install the landing skid braces and 

the trainer landing gear. Photo 9 shows both these systems. The gray plastic legs reinforce the 

landing skid while the white pieces comprise the training gear. Install the braces first to help 

protect the landing skid during installation of the training gear. 

The shorter braces go on the rear of the helicopter as shown in photo 10. Snap the brace onto 

the skid cross bar above the rear vertical strut as shown. The top piece is held in place by the 

same screw that holds the tail boom in position (photo 10). Remove one screw at a time to keep 

the boom in place, position the brace end and install the screw. Do not over tighten the screws as 

they are very tiny and are seated into plastic. You do not want to strip the treads in the plastic 

mounts. Use the small screwdriver provided. 


The longer, front braces attach on the top to the small top screws just outboard of the front 

coreless motor as shown in photo 11. Again, be careful not to strip the screw threads. The front 

braces clip to the front vertical strut just above the landing skid. Photo 12 shows the completed 

landing skid braces on one side. This side also shows the receiver crystal, in this case on 

Channel 42. If necessary, you can change the Channel just by changing both this and the 

transmitter crystal.


Photo 13 shows the mounting “hardware” for the training gear. Using this gear helps to prevent 

the XRB SR from falling over on its side during a “sideways” landing. We new helicopter pilots 

have a difficult time landing while the helicopter is in a true, motionless hover. The machine 

always seems to be moving one way or the other when it finally touches down. If it is moving fast 

enough when it lands, it can fall over on its side, wiping out one or more blades. The training gear 

ends this hassle and keeps the helicopter upright during “dynamic” landings. 


Photo 14 shows the training gear itself. The four “legs” of the gear and the ball ends are cut from 

the white plastic “tree.” The ball ends are just slid on the rod to the stop on the far end. There are 

two types of soft skid mounts (photo 13). Align them as shown in photo 15 and slide a rod into 

each with the ball end outwards. But do not mount the rods into the center 4-cornered hub yet. 

Position each rod towards the center as shown in photo 16. Once they all meet, then install the 

center hub. 

Photo 17

After about 20 minutes of assembly time, the XRB SR looked like photo 17. The braced landing 

skid system is very strong and the light-weight training gear keeps the machine upright even 

during a rather harsh landing; and I had plenty of those at the start but there was never even a 

hint of damage. When fully assembled, the XRB SR Sky Robo is a very attractive looking 

helicopter. 

In photos 13 and 15, you can see a few of the many illustrated directions that are included with 

this aircraft. The instruction book is very detailed and complete. It includes three pages with 

fourteen illustrations just on pre-flighting the helicopter. There is a six page flight instruction 

manual and six pages with 36 illustrations on making post-flight adjustments. 

Another four pages show how to adapt the XRB helicopter and its receiver to a different 

transmitter than the one supplied. As they gain experience, some helicopter pilots may wish to 

use a computer transmitter instead on the analog one supplied. This is done to increase mixing 

options such as rudder trim to throttle to adjust trim as the motors heat up during operation. The 

receiver and its integral gyroscope, used to stabilize the helicopter, are compatible with all brands 

of transmitters. 

Battery Charging 

Before flying, charge the battery using the included wall charging unit. It is important to always 

use this charger when flying the XRB. Li-Poly batteries are a great technological advance over 

older Nickel Metal Hydride or Nickel Cadmium batteries. In fact, small electric powered 

helicopters like the XRB SR would not be possible without Li-Poly batteries. But with increased 

capacity and light weight, Li-Poly batteries also have increased risk factors. 

Using a non-Lithium charger will cause the batteries to explode. Burning or damaging them will 

also cause the battery to burn. Lithium Polymer batteries burn with a temperature around 2,000 

degrees F. That is very hot and will certainly ignite any burnable items, including aluminum cans, 

within reach. Lithium is an extremely reactive metal and combines explosively with the oxygen in 

the air. No other ignition source is required. If the battery pack is ever physically damaged or 

shows any signs of expansion or swelling, do not use it. Discard it at an approved recycling 

center. 

The battery charger puts out 0.65 Amps. That means that it will fully charge the .72 Ah (720 mAh) 

battery in about one hour. Is practice, the battery is never fully discharged so plan on about 40 

minutes to recharge after each flight. An extra battery, Hirobo part number 0301-032, would be a 

good idea for more flying time. Just be sure to allow a ten minute cooling period for the motors 

between flights. 

The charger appears to be a “balancing” charger. This means that the charger individually senses 

each of the two 3.2 volt cells in the pack. As one cell reaches full charge, current to it is reduced 

while the other cell completes its charging cycle. This is an important safety feature and is fast 

becoming the norm with Li-Poly chargers. Without balancing during the charge cycle, one cell 

may reach capacity before the other. The non-balanced charger would continue supplying full 

current to the fully-charged cell and it could rupture or explode. 

Never charge the battery inside the helicopter; always remove it. It would be safest to place the 

battery and charger on a non-flammable surface such as a concrete block or steel, not aluminum, 

plate. Make sure nothing is within five feet of the area above the battery or within two feet on any 

side. 

These safety precautions apply to ALL Lithium Polymer batteries, not just the one supplied with 

this helicopter. 

First Flights

Photo 18 

The entire assembly process took about 30 minutes. All the control movements were checked 

and they all wiggled in the right directions. The battery was inserted with the connector under the 

front cross member as shown in the instructions. This makes it easy to snap the cockpit on and 

off. Connect the battery to the receiver and everything is ready to go. 

Remember this is an indoor helicopter. So the first flights were done in a school cafeteria with ten 

foot high ceilings. The XRB SR has a convenient on-off switch so it is possible to safely connect 

the battery before turning on the transmitter. For flight however, the transmitter must be turned on 

first. 

Then hold the helicopter still with on finger on the landing skid and gently turn the receiver on. Do 

not let the helicopter move until the LED on the side is lit. The short, about three seconds, startup 

period sets the gyro for straight flight so it is important to make sure the helicopter is motionless 

during this period. 

Then just lower the throttle switch all the way to arm the motors. There is an extra safety that 

prevents the motors from turning until the transmitter throttle is reduced all the way. Once the 

safety is disarmed, the red and green LEDs should be lit, warning that the gyro is initialized and 

the motors are ready to be armed. Carefully press the motor arming switch, called the start 

switch, and the XRB SR is ready to fly. 

I like it that this helicopter has three separate safeties to protect my fingers from the blades. But in 

reality, these safeties actually protect the foam blades from my fingers. While the coreless motors 

are powerful for their “180” size, these are not four-horsepower units from a 30% Extra and 

cannot cause much physical damage to people or furniture. The foam blades resist scratching 

tables or skin, but it is always good to be on the safe side. 

Photo 19 

Photo 18 shows the XRB SR Sky Robo just before its first liftoff. Remember that I do not fly 

helicopters, only fixed-wing models, and that this was a new experience for me. The helicopter 

lifted off and hovered with a slight backwards motion (photo 19). I held the right transmitter stick 

forward just a small amount and added some “down” trim.

Photo 20 

The machine moved forward during this process and rotated its nose to the right. One thing a 

new RC helicopter pilot learns quickly is to watch the nose direction, not the tail motion. With the 

helicopter pointed away from the pilot, moving the left-hand “rudder stick” to the right moves the 

helicopter’s nose to the right while the tail boom swings leftwards. However, when the helicopter 

is pointed at the pilot, moving the transmitter stick to the right swings the tail boom to the right 

while the nose seems to travel to the left. This is similar to the aileron control reversal a fixedwing 

pilot experiences when the airplane heads back to the pilot. 


I was very surprised by just how easy this helicopter is to fly. It is extremely stable and goes just 

where it is pointed. There is plenty of reserve power; liftoff needed only about half throttle. After 

about 5 minutes of hover and landing practice, I was getting to feel just a little bit of confidence 

that “hey, I can do this!” and brought the helicopter up to eye level and hovered around. This is a 

very easy machine to fly. 

I tried left and right side movements using the “aileron stick” and these also were predicable and 

stable. Intentional backward flight, not the accidental one on liftoff, proved possible but needed 

some more pilot orientation to keep the tail boom pointed “straight ahead”. Still, there were no 

stability problems but the rearward motion was very slow. 

Photo 23 Photo 24

Now over-confident by just how easy this machine is to fly, and fun too, I lifted off and went to 

“high altitude” to set out on a cross country flight (photo 23). After flying about five minutes and 

now recklessly over-confident, I decided to land at the far away “Table Top Mesa” airport as 

shown in photo 24. You know, the darn thing landed like it was being guided in by a Tractor 

Beam.” 


Liftoff from Table Top airport was uneventful as was the return trip (photo 25). However, 

remember that the XRB SR is designed primarily for indoor flight. As such it does not cover 

ground quickly. Maximum controllable forward motion is 3-5 mph. Trying to fly faster than 5 mph 

causes some instability and rocking motion. But 5 mph indoors is 7.5 ft. / second and that seems 

pretty fast when the wall and ceiling start to approach the helicopter. While attempting some high 

altitude flights, I bounced the XRB SR off the ten-foot high ceiling (photo 26). The rugged 

construction survived with no damage and the foam blades never scratched the fragile ceiling 

tiles. 


Returning from the cross country flight, and after having determined the aircraft’s service ceiling, 

it was time to land. Still not quite believing how easy this helicopter is to fly, I made the landing 

approach (photo 27), hovered a bit and landed (photo 28) with just the slightest side motion. Not 

bad for a first helicopter flight. 

How It Works

Photo 29 

Twin rotor helicopters simplify rotary flight because they sacrifice, up to a certain point, forward 

motion for stability and easy control. The twin rotors shown in photo 29 rotate in opposite 

directions to eliminate the torque effects caused by a single large rotor blade. This means that a 

tail rotor is not required. 

Photo 30 

Having the twin rotor blades counter-rotate around a single shaft reduces the mechanical 

complexity usually found in twin rotor systems. The upper blade and moveable head are not 

connected to a servo. Instead, the stabilizer bar, fly bar, senses the helicopter’s body movements 

and automatically adjusts the cyclic operation of the top blade to control “rudder” direction 

opposite to body motion. This stabilizes the machine in directional flight. 

Photo 31 

The angle between the stabilizer bar and the top rotor blade is important and should be about 90 

degrees. However it is adjustable should that be required for trim. Our XRB SR did not need 

adjustment. 

The lower rotor blades and head are not stabilized. Instead they are controlled by the servos. The 

servos control the rotor through a swash plate for “aileron” and “elevator” control. By angling the 

lower rotor disk downwards or upwards, an elevator effect is induced. By pitching the disk angle 

left or right, there is an aileron effect.

Photo 32 

“Rudder” control is determined by the twin coreless “180 series” motors. Depending on the 

transmitter inputs, one rotor is made to turn faster than the other and creates a torque that 

controls the yaw axis. 

How is forward flight limited? Inputting “down” elevator tilts the bottom rotor disk downwards 

toward the front. Pointed in this direction, the bottom rotor disk provides some forward thrust. But 

the top rotor is stabilized by the fly bar and remains rotating in a plane horizontal to the air. Its 

disk is not pointed downwards at the front as is the bottom rotor disk. Increasing the angle 

between the top and bottom rotor disks too much, by asking the helicopter to fly forward quickly, 

begins to result in an instability caused by the widely divergent disk thrust angles. 

But the twin rotors sure make the XRB SR easy to fly for a novice helicopter pilot! And indoor 

flight is measured in feet, not miles, so fast forward speeds are not useful nor desired. This is a 

very sophisticated machine. Tiny control inputs have big results. While not overly sensitive, the 

XRB SR responds quickly to inputs. You will find that stick movements are almost imperceptible, 

even to the pilot. Fortunately, the helicopter flies itself, right from the start. 

Everything needed for a beginning helicopter pilot is included and then some. The list price for a 

painless introduction to rotary flight is $350.00. But the street price is usually $300 or less. For 

more information about this very complete package, please go to: 

http://www.modelrectifier.com/products/rcHelicopters/xrb_Sky_Robo.asp

The XRB SR Lama Sky Robo From Hirobo by Francis ... - Sport Aviator

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