Hirobo SRB Quark

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Hirobo SRB Quark
Quark Main.jpg
Manufacturer Hirobo
Class Fixed pitch electric; about 175 size
Build RTF
LevelBeginner to Intermediate
Quark SRB


The Hirobo S.R.B Quark (aka Quark, Quark FP), is a micro-sized fixed pitch electric helicopter manufactured by Hirobo Corporation. “SRB” stands for Single Rotation Blade to distinguish it from Hirobo’s coaxial “XRB” helicopters. Released in February 2008, the Quark has developed a reputation for its high degree of flight stability, precise handling, safety features, robust and reliable parts (but expensive), and historically high MSRP. The Quark is considered by many to be one of the easiest and safest single-rotor fixed pitch helicopters to fly.

In January 2011, a new version of the Quark, Quark STD, was announced for sale in early February 2011 in Japan. The new version will have some minor updates including use of the SG blades, upgraded tail shaft, and a 5 channel transmitter (5th channel for use with the Hirobo LED light kit).


  • Gear Ratio: 5.29:1 (Main Blade), 4:1 (Tail Blade)
  • Length: 350 mm
  • Height: 146 mm
  • Width: 72 mm
  • Main Rotor Diameter: 355 mm
  • Tail Rotor Diameter: 106 mm
  • All Up Weight: 170 g

Stability features

Flight stability is a result of a combination of design features that includes:

  • Hirobo’s flybar (a patented 45 degree angle offset from the main blades).
  • Full Bell-Hiller mixing in the rotor head.
  • Slight tilting of the helicopter axis to balance the thrust produced from the tail rotor.
  • Raised landing gear on one side to facilitate vertical take-off.
  • High coning angle of the main foam blades when flown.
  • Individual pitch adjustments for each of the main blades.
  • Adjustable handling modes from beginner (default) to advanced/sport (see section below for advanced settings).

Safety & damage resistance

Safety features of the Quark make use of polystyrene (Styrofoam) blades, a flybar with rubber paddles, and a relatively low running head speed (1800-1900 rpm at hover). In a crash, the blades are meant to break and the flybar is designed to fall apart: this helps to absorb impact and prevents damage to other components.

In general, the Quark is very resistant to damage, with the exception of the blades. However, it is common for users to laminate the foam blades with tape to make them stronger, although this may be detrimental to other components when there is an impact, and may modify the flight behaviour due to less coning.

Another safety feature of the Quark is its autoland function. If the helicopter loses the transmitter signal (e.g., the helicopter is flown too far away) or the battery voltage drops too low (e.g., flying beyond normal flight time), the Quark will hold its position and land by itself.


The Quark control unit contains the receiver, gyro and electronic speed controller (ESC), and all electronic adjustments can be made on the control unit itself. If damaged, the control unit cannot be purchased as a replacement part but may be repaired by an authorized service.

The helicopter uses a brushless main motor and the tail rotor is shaft driven by a brushed coreless motor.

Lipo battery

These motors can draw power from the bespoke Hirobo stock battery, a 2-cell 7.4 V 480 mAh Lipo with battery connectors for balance charging. The stock battery yields flight times between 8-10 minutes. Third party 7.4 V batteries can been used with the Quark such as the Rhino 460 (also 360, 610 and 780) and the Thunder Power Pro-Lite V2 730. Most of these third-party batteries have a JST connector but the Quark uses a proprietary Molex connector.

A JST-Molex adapter cable or connector change is required in order to use third-party batteries, along with slight modifications or removal of the battery tray for most of them, due to battery thickness. Most users remove the battery tray and attach third-party batteries with Velcro directly to the bottom of the helicopter, or use elastic bands. Connecting a battery the wrong way round, through a bad JST adapter for instance, is known to immediately "burn" or "smoke" the control unit.


The Quark is currently available in two different kits: ready to fly (RTF) with transmitter or without transmitter. The RTF package comes with a basic stock 35/40/72 MHz FM transmitter, made by Futaba but unbranded. There are no options to use a 2.4 GHz transmitter, due to the custom Hirobo control unit, so the traditional shortcomings apply: shorter range, the transmitter requires a much longer aerial, increased greater power consumption (AA batteries last for about 2-3 hours), and risk of radio interference or temporary loss of signal. A "no transmitter"/barebone option is also offered and the helicopter can be bound to Futaba, Sanwa or Japan Remote Control FM-PPM transmitters with at least 4 channels.

Kit contents

All kits include a:

  • Spare set of 8 main blades.
  • Spare set of 4 tail blades.
  • Set of small tools (small Phillips and Flathead screwdrivers; 0.89 mm and 1.5 mm hex keys).
  • Blade balancer.
  • Lipo battery, AC charger and adapter.
  • Decal set (with two colour schemes included: orange/blue and purple).
  • Comprehensive 45-page printed user manual.
  • Warranty card, although no warranty terms are stated and not all components are available as spares.


Stock items

  • RTF: in October 2009, the MRSP for the S.R.B. Quark (RTF) was $429 USD, with a usual street/Internet price of about $335 USD; as of June 2010 the street/Internet price in the USA dropped to about $200-$250 USD or less
  • TX-less version: $305 USD
  • Hirobo battery (480 mAh): $60 USD
  • Hirobo main blades (set of 8): $18 USD
  • Hirobo tail blades (set of 4): $10 USD

New performance/upgrade parts (see Hirobo upgrades section below for more details)

  • Hirobo LED light kit: $50 USD
  • Hirobo tail boom pipe, carbon fiber (about 1.5 g lighter than the stock boom): $18 USD
  • Hirobo tail drive shaft, double bearing/high precision: $30 USD
  • Hirobo metal swashplate assembly: $110 USD
  • Hirobo metal rotor head assembly: $145 USD

Hirobo upgrades

Possible upgrades from Hirobo include:

  • A LED light kit (includes 7 LEDs and a control box, with several modes). The kit increases the weight of the Quark by about 13 g, but makes flying in dark conditions much easier. Flying time is reduced by about 1 min, mainly due to the added weight rather than the current draw of the LEDs. The LED kit is installed permanently with some double-sided tape, so is difficult to remove once installed.
  • A new but very expensive blue metal head and swashplate (combined cost is $250 USD).
  • A new carbon fiber tail boom, with reduced weight compared to the stock aluminum one.
  • A new dual-bearing tail shaft. The dual-bearing tail shaft is an upgrade from the stock single bearing one, and was released by Hirobo to correct the common issue of excessive vibrations and loss of power (commonly referred to by users as "BRRRTing" for the distinct sound it makes). Despite the known issue around the tail shaft, Hirobo does not provide the corrected part at a discounted price or coverage under warranty.
  • An improvement in advanced flight performance has been reported with the Hirobo SRB Quark SG main blades. Compared to the Quark FP main blades, the SG main blades are stiffer which consequently leads to decreased coning. The SG blades will fit the Quark FP without modification but some pitch adjustment may be required.

Other upgrades

Common aftermarket upgrades from other vendors include:

  • Aftermarker batteries, usually found on ebay
  • Custom canopies (mainly from MIA Micro-FLIGHT).
  • Custom fuselages (mainly from Darthdrk).
  • Wider/taller landing gear (MIA Micro-FLIGHT).
  • Carbon fiber main blades (eBay).
  • On-board cameras: stick cameras (eBay) or key fob cameras (eBay).

Known issues/shortcomings

Design/Manufacturing items

  • Foam blades are fragile and break easily. Usually they can be repaired with 5 minute epoxy, Maxi-Cure Extra Thick CA.
  • Newer main blades, which have a crinkled shiny undersurface, may not perform as well as the older blades, which have a smooth matte undersurface and are typically found in the kit. When using the newer blades, it is common for users to set maximum blade pitch in order to maintain the correct head speed for hover.
  • Older tail fins were 71mm in height which did not provide much protection against tail strikes. However, newer tail fins have an extended height of 77mm.
  • Tail noise and vibrations ("BRRRTing") with standard tail shaft. Double bearing replacement shaft highly recommended (see link to installation video below).
  • Pinion may come loose from the end of the tail drive shaft due to poor factory assembly (poor glue). This problem can cause tail twitching or complete loss of rudder control. The loose pinion can be easily fixed by regluing the pinion to the tail shaft (be careful not to drop glue into the bearing). This issue is unrelated to the BRRRTing issue, but BRRRTing can advance the onset of this.
  • There have been several reports where the antenna sheath may be nicked by sharp edges of the canopy at the antenna opening. This problem could potentially cause the antenna to break off. Recommend filing the opening, or taping the edges of the opening and the antenna.
  • In some cases, the Hirobo LED light kit has been purported to cause some problems with initialization. These problems have been observed to be transient or become manifested after a prolonged period of time following installation. Disconnecting the LED kit and reconnecting fixes the issue.

Flight issues

  • Mild to excessive tail drift with some control units as gyro warms up. Requires trim or mid-flight landing and power cycling to reset.
  • Main motor lacking punch.
  • Cannot handle very much wind due to low head speed and small weight. Heli must be flown in very little (< 3-5 mph) or no wind.

Radio system issues

  • Control unit/receiver antenna wire must dangle from nose of heli for optimal reception.
  • Limited radio range when helicopter is on the ground. Take-offs and landings should occur within 10-20 feet of the operator.
  • Range issues with some 72 MHz radios when transmitter antenna points skyward - pointing it down may help. Info

Hirobo eccentricities

  • Control unit is not available as a spare, but is repaired free of charge by Hirobo.
  • Expensive stock battery, non-standard connectors, and tight battery tray (which compel owners to use Hirobo proprietary batteries (expensive)).
  • High price, including spare parts.
  • No explicit warranty terms stated by Hirobo.
  • Some replacement parts are "bundled" with their respective assemblies. For example, replacing the two canopy mounts requires purchasing a new main frame kit that includes the frame, canopy mounts and main shaft bearings.


The Quark performs very well out of the box and, as a result, no major modifications are required. Some optional mods are listed below.

  • Laminate the blades.
  • Do-it-yourself (DIY) dual bearing tail shaft.
  • Remove stock battery tray, and mount aftermarket batteries with velcro/crisscrossed rubber-bands.
  • Add weights to the flybar for even more stability.
  • Twist tail boom/tail rotor a few degrees CW or CCW for better hovering and/or yaw performance.
  • Glue the windshield to the canopy.
  • Protect the antenna from being nicked or cut by the sharp edges of the canopy antenna opening by filing the opening, or taping the edges of the opening and the antenna.

See "Mods and repairs" in the "External links" section below for Websites for some more information and instructions.


Although the Quark is generally considered to be very safe around people, flying aircraft is a dangerous activity and can cause injury or even death. Follow all safety procedures as outlined in the manual and local regulations.

Tips for the beginner

  • If you are moving up to the Quark and have never flown a FP heli before, buy a simulator first and practice - it's invaluable.
  • For new FP pilots flying the Quark, start with an area of at least 20'x20' (or follow Radd's school of rotary flight). A larger area will provide space for error and recovery.
  • Performing piros (spins), especially slow ones, are usually difficult to perform for beginners. The heli will "swoop out" with rudder input only - this is normal and due to translating tendency. Right piros usually require slight left and aft cyclic. Left piros usually require slight right and forward cyclic. Also, slight throttle adjustments are usually required to maintain altitude during a piro.
  • Take your time and practice.
  • Recommended reading Getting Started in RC Helicopters by Mikeflyz.

General tips

  • The heli will hover and fly better if all blades are balanced, blades are tracked properly, and hovering head speed is set.
  • Do not overtighten the blade pitch screws - they can strip easily.
  • Ensure that third-party battery connections are correct in order to prevent "smoking" the control unit. Some users mark the connectors' ends.
  • Allow the antenna to hang straight down for best radio reception.
  • Be careful when moving around the throttle stick on the stock transmitter. There is no throttle hold/kill switch.
  • Avoid taking off and landing in tall grass - grass can get caught in the main gear.
  • Head speed can drop rapidly, avoid dropping the throttle too fast.
  • To prevent the motors from burning out prematurely, allow the motor to cool down for a minimum of 5-6 mins after each flight.
  • Avoid touching the motors after flight - they're hot!
  • Allow the battery to cool down for a minimum of 5-6 mins after each flight before recharging the battery.
  • Double check the flybar, linkages and tail section after crashes.

Advanced/sport settings

The Quark is shipped from the factory with normal/basic settings for the beginner. However, the settings can be changed to advanced for the intermediate or expert flier (references to page numbers in the manual below).

Mechanical adjustments:

  • Reposition the balls in the stabilizer from the lateral positions to the centre positions (p. 33). This will make the heli more sensitive to steering and less stable.
  • Move the inferior end of the stablizer control rod to the outer hole on the washout assembly. This will increase the sensitivity of the heli and make it less stable.
  • Move the pitch rod ball on the seesaw assembly to the most outer hole (third hole). This will also increase the sensitivity of the heli (see p. 33 for a diagram of the seesaw assembly).

Electronic adjustments on the control unit:

  • Turn dip switch #4 to the "on" position (move switch to the right) (p. 38). This will increase the sensitivity of the aileron and elevator.
  • Turn the RUD ATT (rudder rate adjustment dial) clockwise (p. 40). This will increase the rudder rotation speed for faster pirourettes.

Trivia/interesting tidbits/rumours etc.

  • Owners of the Quark commonly refer to themselves as members of the "Brotherhood of the Quark" or simply "Brotherhood".
  • Hirobo now provides an online electronic copy of the manual and an expensive hardcopy (e.g., replacement) is available for sale at $25 USD. See links to the manual below.
  • When the warranty card is returned to Hirobo in Japan, the buyer is mailed a "free registration gift" which is a sheet of some large Hirobo stickers.
  • The rear light of the LED light kit is not only for lighting but it also indicates when the gyro has completed initialization in pre-flight, and also when the hovering head speed has been achieved during flight. This feature of the rear LED is undocumented. The rear LED is much easier to see than the small LED on the control unit which may be partially obstructed by the canopy.
  • Around September 2009, Hirobo announced on its Japanese Website, a package that included the helicopter, LED light kit, an aluminum case, and a JR X-2720 transmitter for $76,650 JPY (approx. $850 USD). Around late October 2009, the package was updated to include the Futaba 6EX-HP transmitter for $68,775 JPY (approx. $765 USD). These "dream" kits are not currently available.
  • A Quark with collective pitch (CP) was rumoured to be released late 2009 and was formally announced as the Hirobo SRB Quark SG (Quark Second Generation) at the Nuremberg International Toy Fair, around February 6, 2010.
  • On July 9, 2010, Hirobo announced on its Fanblog that the Quark would still be made available, "We are still making and selling SRB Quark and we do not have any plan to stop this line." However, as of August 27, 2010, it was rumoured that the Quark was being discontinued as some reported difficulty finding stock in the US. It has been suggested that the Quark is being replaced by the Hirobo SRB Quark SG.
  • In January 2011, it was reported that Hirobo would release a new version of the Quark, "SRB Quark STD" (Standard), in early February in Japan. It is expected that the STD will come with a 5 channel transmitter for easier transition to the Hirobo SRB Quark SG, improved tail drive shaft, and the price will be reduced.


  • "Hirobo Quark SRB - Best thing since sliced bread?", strx, January 30, 2009.
  • "Hirobo SRB Quark - Ultimate Indoor......! I can't say enough about this tiny Heli. Yes, it's expensive, but IMHO it's worth every penny. The build quality is top notch! AND the flight characteristics.....one word: WOW! Stable as heck, but not so much as it's boring compared to the Blade CX2 counter-rotator", huskynox, May 21, 2008.
  • "Most stable, durable and best made heli needing no mods would be the Hirobo Quark but its also the most expensive up front. Its the BMW of 4 channel single rotors and will cost less in the long run because it needs nothing to fly correctly, is very nimble and can really move like your MSR and is just as stable in hover but it really depends on your budget", Xrayted, October 29, 2009.
  • "I am a huge proponent of the SRB Quark. It's the ultimate beginners heli for many reasons...The Quark will take you from rank beginner to a point where you can fly a decent sized CP heli with relative confidence, with few unexpected expenses", Balr14, June 26, 2009.
  • "The Quark is an excellent model for beginners and great fun for experienced pilots too as long as they don't mind the price tag of around $350/£250. One of its greatest features is safety. This model has very light blades which rotate at a relatively low speed which makes it safer to be around people than just about any other single rotor model", Radio Control Rotorworld, Issue 35, March 2009.
  • "Hirobo has introduced a very cool product. If priced lower it would undoubtedly be a hot ticket item. However, even at the price it is set at, the model is sure to be moderately popular. It is incredibly fun, easy to fly, and offers similar stability to a counter-rotator while still being able to venture outdoors", RC Heli Magazine, Issue 23, May 2008.


Show us your heli! Feel free to upload your pics and add them to the Quark SRB Gallery

Links to selected quark videos

External links

Hirobo Quark official website and other information

Main discussion forum


Mods and repairs

Parts and product support


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