Skysprite RC Micro RTF Electric

 

Over the past couple of years we have seen considerable new activity in our hobby involving micro size RC model aircraft. These models generally weigh 3 ounces or less and, for the most part, are flown at indoor facilities. These facilities can vary from school auditoriums or gymnasiums up to large inflatable dome sports arenas.

The advantages of such small RC aircraft is (1)- no concern for wind or weather conditions, in other words you can fly anytime the facility is available, (2)- flying can continue during winter months when normally that wouldn’t be possible and (3)- the small size of these planes make them easy (fast) to build with only minimum investment.

For the most part, up until recently, these small indoor models have been constructed from plans and to some degree from kits. Although the next size larger models, like “Parking Lot Flyers” are readily available in ARF and RTF version, that has not been the case with the RC micro indoor models. Recently we have seen several RTF model aircraft come out with the express intention of being flown by RC at indoor facilities.

Photo 1

The subject of this review is one of those new RTF (ready-to-fly) models, the “SKYSPRITE” being offered by FMA Direct. This is a 1.6 ounce model, constructed of molded foam parts, that arrives ready to fly with both the power system and the control system already installed (photo 1). Everything necessary to fly this RC model is included with the exception of six AA size alkaline battery cells. These are required to power the RC transmitter.

The SKYSPRITE meets all the aircraft requirements of the Academy of Model Aeronautics’ (AMA) Park Pilot Program. The aircraft weighs less than 2 pounds (the Program’s upper weight limit) and has a level top speed under 60 mph (the Program’s upper speed limit). For complete Park Pilot aircraft details, follow this link.

The AMA Park Pilot Program offers non-AMA members the opportunity to become AMA members at a much reduced cost. Park Pilot membership includes a great magazine “Park Pilot”, $500,000 personal liability insurance, $2.5 million liability insurance for the both the outdoor and indoor flying site owner (see insurance details) and membership in the world’s largest sport aviation association – the AMA. For complete information and details about Park Pilot membership, just click here.

 

Photo 2

This entire RC micro indoor model system is selling at this time for only $39.95. How low can you go for a complete RC model, control system and power system? To provide a good size comparison, here is the SKYSPRITE pictured next to a conventional .60 size glow engine (photo 2).

The control system involves two-channel operation. One channel is used to control the electric flight motor, while the other channel operates a tiny electric motor, located in the tail (vertical fin) that steers the aircraft with motor thrust from this tiny rear motor.

Neither control channel is proportional. That means the motor runs full speed or zero speed (prop stopped!). The steering channel will provide full left or right control for as long as you hold down on the transmitter button. Whether you are a newcomer to our RC hobby or have previous experience, flying the little SKYSPRITE will require learning some new techniques. But those techniques are easy to learn and very rewarding after a few full-duration flights. For a very low-cost way to try RC flight there is nothing better than this model.

 
Photo 3    Photo 4

The “SKYSPRITE” comes fully assembled in a small box (photo 3). The wing span is only 14 inches, so even the shipping box is small, making it ideal to transport. The wing is permanently affixed to the fuselage. The small electric flight motor is already installed. I couldn’t tell the brand of motor because as it was hidden inside the fuselage. FMA Direct has indicated that it is a small (3 volt) Johnson motor. Overall fuselage length is 13 inches. The prop has a 3 1/2 inch diameter. It includes an integral spinner (photo 4).

 
Photo 5     Photo 6

Thoughtfully an extra prop and spinner in included (photo 5). The only assembly work required is to insert the main landing gear wire and the tail wheel into slots molded into the fuselage (photo 6). No gluing is required at all. As was the case with the motor, the pre-installed RC receiver and motor control were not visible and so I’m can’t comment on their origin. The instructions indicate that SKYSPRITE systems are shipped on both 27 and 49 MHz. None are available on 72 MHz, which means that it is unlikely that the SKYSPRITE would cause any interference to models being flown at a local club field.

(Ed. Note: However, there are just six “27” frequencies available for RC flight. They are numbered Channels 1 through 6. The same frequency rules for regular RC models also apply to indoor and Park Flying. Do not operate your transmitter until you have made certain your channel number is clear.)

 
Photo 7     Photo 8

The RC transmitter that comes with the system is of the hand held variety (photo 7). You will need to purchase a total of six AA size alkaline battery cells (photo 8). These are non-rechargeable batteries. Once expended they are discarded and replaced by fresh cells. It is interesting to note that, after installing the six battery cells (using the instruction manual to determine the correct polarity) I couldn’t get the hatch cover to stay in place. It took some time to get the catch to hold. My concern was that the battery cover might pop off while I was flying with the batteries falling out of the transmitter. I learned that FMA Direct was aware of this problem and that they are taking steps to have the battery compartment molding and cover modified on future transmitters.

Photo 9

The RC system has two channel functions and neither provides any proportional control. Squeezing the throttle “trigger” button (switch) with your index finger (photo 9), and holding it, turns on the electric flight motor at full speed. As long as you hold that button down, the motor continues to run at full power. Release the button and your motor (and prop) stops. Ascending and descending flight is achieved by turning the motor on and off.

Photo 10

At the same time, your thumb sits on top of a second switch, which controls the steering of the SKYSPRITE (photo 10). It is a rocker type switch. When you push it to the right side the plane turns right and the opposite occurs when you push the switch to the left side. What will really interest you is the way the actual steering is accomplished.

Photo 11

The SKYSPRITE employs neither an RC servo nor a magnetic actuator. Installed in the vertical fin is a tiny motor with an equally tiny prop (only 7/8 inch diameter!). Photo 11 shows how the motor and prop are installed in the fin much like you have seen on model and full size helicopters (as a tail rotor).

Photo 12

Pressing the steering channel button on the transmitter causes this tiny tail rotor motor to rotate in one direction (to steer left) or to rotate in the other direction (to steer right). Again this is non-proportional control so the tail rotor will spin and the tail will make a turn as long as you hold down that button on the front of the transmitter (photo 12). I’ll get back to discuss this steering control later.

My particular transmitter (I think) operates on the 27 MHz band. I say that cautiously because there were no band, channel or frequency markings on the transmitter. A single ribbon flag was provided and it was red in color. Using the reference material provided in the AMA Membership manual (2004 edition, page 17) I was able to determine that a single red colored ribbon was suppose to note CH-02 (27.045 MHz) on the 27 MHz RC band. There are a total of 6 channels called out on this band, so my suggestion to FMA Direct would be to include the channel number and frequency and make sure that the correct colored flag is supplied with the system.

Although you might be able to purchase the SKYSPRITE on any one of six different channels, I suspect you couldn’t fly all six at the same time. I had no other 27 MHz RC systems in my inventory to run an adjacent channel check. But at 50 kHz channel spacing it is possible that these systems might interfere with one another. If you attempt to run two SKYSPRITE’s at the same time I would make a range check first before flying. I suspect a similar situation might exist for systems operating on the 49MHz band. If that is the case, these systems should also be marked for band, channel and frequency.

 
Photo 13      Photo 14

A very small, 3-cell, 120 mAh NiMH airborne battery pack is supplied with the system. It weighs just 0.43 oz. (photo 13). This battery powers both electric motors and the RC system. It can be fast-charged by attaching it to a slot located on the front of the transmitter (photo 14). After plugging in the pack you hold down a momentary contact switch all the while the battery is charging. A fully depleted battery will take only one or two minutes to achieve a new full charge. Considering this, you won’t be holding on to the switch button very long.

Photo 15

A very simple and clever thermal indicator is affixed to the outside of the battery. Before initiating the charge, the tiny indicator will be blue in color (photo 15). As the charge progresses, this indicator will turn from blue to a white color. When that happens the pack is said to be fully charged. Several amps worth of current are applied in a brief period of time, so expect the pack to get quite hot.

The total weight of the SKYSPRITE (on my scale) was 1.6 ounces, including the weight of the battery. I calculated the wing area at about 33 square inches. At that weight and area, the wing loading works out to 7 ounces/sq.ft. which is still quite respectable. Since everything is already set up for you, there is no mention about the CG position. Then again, that really isn’t important for this application. My SKYSPRITE seems to balance at about mid wing chord, with the battery pack in place. Normally I would say that it would be tail heavy, but the plane certainly flew fine.

Since I do a lot of original design work, I like to really get into the inner operations of these small aircraft. That being the case I hooked up my Astro Flight SUPER WHATT METER-II and checked the motor voltage, current and power (watts). Since this battery only supplies 3.6 volts nominal, I used the added battery on the SUPER WHATT METER to be able to read below 4.0 volts. With the 3 cell 120 mAh NiMH pack at close to full charge; I measured 3.18 volts under load, at 1.2 amps and 3.0 watts power level. That works out to 1.87 watts/ounce, which is fine for this sport flying model. My calculations determined that at 1.2 amps motor current the 120 mAh NiMH battery should be capable of powering the SKYSPRITE for about 5 to 6 minutes.

The instruction manual mentions the possibility of substituting a single cell 340 mAh FMA/Kokam Li-Poly battery cell for added flight time. I have not done this as yet. The Li-Poly battery would weigh 0.36 ounce, as compared to 0.43 ounce for the 120 mAh NiMH. That’s very close in weight. But the Li-Poly might provide for motor run times in excess of 15 minutes, which is quite long. The interesting paradox here is that the NiMH pack runs the motor 5 minutes or so and takes only 1-2 minutes to recharge. The Li-Poly cell can provide 15 minutes plus motor run time but takes at least one hour to recharge. In this particular instance, the NiMH battery might just prove the better choice. (Ed. Note: One hour is a long time to be holding down that charge switch!)

I also measured the current draw for the tiny tail mounted steering motor. I suspect this is one of the small pager motors. Surprisingly, this motor only measured about 100 mA current when spinning that little 7/8 inch diameter tail rotor prop. So the current necessary for steering is probably less than that consumed by either a servo or a magnetic actuator — an interesting point.

The instructions were quite detailed in regard to flying. The fact is that the SKYSPRITE is what we use to call years ago a rudder only aircraft, with throttle control. You have no elevator control so turning the motor on and off provides the only means for elevation control. Motor “ON” the plane climbs and motor “OFF” it glides down for a landing.

Photo 16

The instructions tell you to initially hand glide the plane without using the motor. There are small adjustment tabs on both the elevator and rudder to allow for a straight and level glide. Although they state that you can take the SKYSPRITE off the ground, I never found a smooth enough surface and so resorted to hand launching. The very best technique is to let the plane go up under power without attempting any left or right turning maneuvers.

Photo 17

I let the SKYSPRITE gain 20-30 feet of altitude before I attempted to turn it. The steering control is more sensitive than you might imagine. So get used to only pulsing the switch button in quick spurts. To make a full circling turn, it is better to just keep “blipping” the steering button. If you hold on to the steering button you will quickly begin to corkscrew into the ground.

Of course I did manage to do that on several occasions. But the SKYSPRITE proved quite resilient, bouncing back ready to go again each time. My six year old grandson, with little flying experience, had no trouble getting the knack of flying this tiny RC aircraft. On the other hand, several of my fellow club members (my age) took more time to get used to it. It does take a while to learn to do without proportional steering and elevator (pitch) control. But we did it years ago, so why not now.

Photo 18

TECHNICAL HIGHLIGHTS

Model: “SKYSPRITE”

 Distributed by: FMA Direct

Street Price: $39.95

Type: Indoor R/C electric, sport/beginners model, also suitable for calm weather parking lot or backyard flying

Wing Span: 14 inches

Wing Area: 33 square Inches

Weight: 1.6 ounces

Wing Loading: 7.0 oz./sq.ft

Length: 13 inches

Motor: Johnson 3 volt variety, direct drive!

Prop: 3 1/2 inch diameter (supplied with plane plus a spare)

Motor Current:  1.2 amps (at start)

Motor voltage: 3.18 (under load at start)

Motor Power: 3 watts (at start)

RPM: 10,200 (at start)

Watts/Oz: 1.87

Battery: Three cell 120 mAh NiMH as supplied or as an alternative a single FMA/Kokam 340 mAh HD Li-Poly cell.

Radio System: Supplied and already installed in the aircraft. RC is a two channel function, non-proportional, system operating on 27 MHz (although some systems will also be sold on 49 MHz frequencies).

 

MANUFACTURER ADDRESSES:

FMA Direct Inc.

5716A Industry Lane

Frederick, MD 21704

(301) 668-4280

Website: www.fmadirect.com

Short URL: http://masportaviator.com/?p=224