Apprentice S 15e vs. Sensei Trainer Match Up

We take them head-to-head to see if one is better

Text, photos and video by Tom Hintz

Test flying by Tom Hintz & Mike Basmajian

Flight video by Clark Ponthier

Posted – 7-13-2016

Not surprisingly FlyingRC.net gets lots of email asking what is the best RC trainer. What did surprise me is the number of people who asked about two specific planes. We have seen a number of these trainers at our flying field so a side-by-side review seemed to be the logical way to go. This Review will focus on the Apprentice® S 15e RTF with SAFE® Technology from Horizon Hobby and the Flyzone Sensei FS EP Trainer ARF w/WISE Gyro sold by Tower Hobbies. We were not able to get a fully RTF Sensei package that included the radio so I am going to use a Spektrum DX8 and a Spektrum AR6210 receiver to make the Sensei “ready to fly”. To keep the comparison on an even plane the DX8 will be programmed to use only the basic functions available in the Apprentice® S 15e RTF system. No dual rates, expo or other enhancements will be enabled in the DX8 for the Sensei.

Another thing I liked about comparing these planes is that both have stabilization systems with very similar capabilities purported to help the rank beginner learn to fly safely. In this review we will look at the stability systems to see how they work. In the near future we will do a more detailed “thrash” of these stability systems to look for their strong and weak spots – if any – that apply to the student pilot.

Test Pilots

Throughout the testing and evaluation of these trainers Mike Basmajian will pilot the Apprentice® S 15e and I will fly the Flyzone Sensei FS. Having one pilot focusing on one plane will give us a more complete look at these trainers and how the stabilization systems apply to their flying characteristics.

In the Kits

Both planes were bought new from their major distributors. The Apprentice® S 15e from Horizon Hobby and the Flyzone Sensei FS from Tower Hobbies. When the planes were ordered Tower was out of the Ready To Fly version so we purchased the Receiver Ready kit (#LXEXZM) and ordered compatible batteries and extra props at the same time.

I began work on the Flyzone Sensei FS by installing a Spektrum AR6210 receiver and bound it to a Spektrum DX8 transmitter to make it RTF (ready to fly) like the Apprentice® S 15e. The DX8 has many features not available on the DX5e included with the Apprentice® S 15e so none of those features will be enabled in the DX8 to keep the radios on an even playing field.

Physical Match-up

The Apprentice® S 15e is made from Z-Foam™ while the Flyzone Sensei FS is molded from AeroCell foam. These materials are reasonably similar and have similar strengths. Both tend to break with jagged, complex edges that make repairing with epoxy easy to do. The complex breaks mean that the pieces “index” insuring an accurate alignment that helps maintain the flying performance after the repair.

The Apprentice® S 15e has a wingspan of 59”, is 42-1/2” long and weighs 49 ounces or just over 3lbs. It uses a 15-size, 840Kv motor running on a single 3S, 3200mAh (1 pack included). A 30-Amp brushless electronic speed control (ESC) with built in BEC is pre-installed. A 12V only 2-3S LiPo balancing charger is included as is a Spektrum DX5e transmitter.

The Flyzone Sensei FS EP Trainer is made from AeroCell foam with a wingspan of 58", is 48" long and weighs 3.2lbs. The Flyzone Sensei FS has a brushless outrunner motor powered by a 3S 2200mAh LiPo battery.

Stabilization Systems

Both the Apprentice® S 15e and Flyzone Sensei FS are equipped with built-in stabilization systems advertised to make learning to fly safer. It is important to note that while these systems do seem to help the novice learn to fly they do not remove the threat of a crash entirely. In both systems, even if they are able to right the plane and return it to straight and level flight before it hits the ground neither have the GPS capabilities needed to return the plane to the area of the pilot. I have trained pilots for decades and a common problem for nearly all of them in the early learning process is letting the plane get too far out or away from the pilot entirely. Neither of these stabilization systems can prevent this.

I have been in the woods near our flying field three separate times looking for two Apprentice® S 15e and one . The new pilots of all three felt they had used the “save” switch but their planes continued and flew out into the woods and crashed. We simply cannot expect an inexperienced pilot to fly the plane back from even reasonably great distances. An instructor is still needed, at least until the new pilot learns the basic skills to keep these stabilization-equipped planes as safe as possible.

Apprentice® S 15e SAFE™ (sensor assisted flight envelope) Stabilization Modes

Beginners Mode allows approximately 15 degrees of up and down pitch and left and right roll. Let go of the sticks and the Apprentice® S 15e RTF returns to level flight. Beginners Mode also includes automatic assistance on takeoff and landings and we will look at these features more closely later during testing.

Intermediate Mode is similar to Beginners Mode but allows 90 degrees of pitch and roll rate to let the pilot be more aggressive with the plane while preventing it from going inverted. Once again, release the sticks and the Apprentice® S 15e returns to straight and level flight if it is at sufficient altitude.

Experienced Mode removes control limits allowing the pilot to loop, roll or fly inverted without interference of the stabilization system. The basic stabilization remains in effect, smoothing flight in all of the modes.

Panic Mode is available in all of the flight modes. If the plane gets out of control the pilot simply engages the Panic switch and holds it until the plane is flying level again. While the automated recovery is surprisingly quick the Apprentice® S 15e RTF with SAFE® Technology needs a bit of altitude to complete the recovery without hitting the ground.

Flyzone Sensei FS WISE System

In the Beginner and Intermediate modes the WISE system limits the amount of pitch and roll allowed very much like the Apprentice® S 15e system regardless of how far the sticks are moved. And, in Beginner and Intermediate modes the system returns the plane to straight and level flight when the sticks are returned to center. In the Advanced mode the pilot has full control, can do loops and rolls and the system will not return the plane to level when the sticks are released.

When pulled the Bailout Switch overrides the sticks entirely and returns the plane to straight and level flight regardless of its orientation. The Flyzone Sensei FS Bailout function is available in all flight modes. If the Bailout switch is held for more than five seconds it “times out” and the sticks once again become active in the mode selected.

Landing Gear

Both planes feature tricycle landing gear long favored on trainers because they steer more easily and eliminate having to “fly” the tail on tail dragger's. However, there are liabilities to having steerable nose wheel. One of the common mistakes new pilots make, usually several times, is landing with a slight nose-down attitude that can deliver a major shock to the nose wheel. That force on the nose gear can require re aligning the nose wheel or having to straighten the wire strut holding the wheel.

The Apprentice® S 15e has a removable cowl that exposes the area around the nose wheel gear to make repairs and adjustments relatively simple. For some reason the folks designing the Flyzone Sensei FS used a glued-on foam cowl with a small hole through which you can reach only the locking screw on the lower (vertical) positioning collar of the front wheel strut. You can see, but not reach the set screw on the steering arm to make adjustments. Virtually any damage or alignment issues mean that the cowl has to be cut apart to expose the nose wheel components or to service the motor and its mount and a new cowl installed. I think that this is an un necessary complication of an airplane specifically designed for pilots that are new to the hobby.

When I wrote this (7-7-2016) I checked for a replacement cowl on the Tower Hobbies site and had to use their sites search system to find it because it did not come up in the parts listing, possibly because it was out of stock and not due in until late July (2016) with a price of $16.99. This isn’t one of the Flyzone Sensei FS better qualities.

The Flyzone Sensei FS uses aluminum main gear while the Apprentice® S 15e has relatively heavy wire holding the main wheels. Both are capable of absorbing reasonably hard landings and both can be straightened to fly again. Both planes get a thumbs up for their main landing gear.

Tail Feathers

The Apprentice® S 15e and Flyzone Sensei FS come out even on the tail feathers as well. Both are modular, using bolt in easy to replace pieces that should keep the money down if you tear something up. Both designs fly well and have more than adequate response.

Wings

Both planes have two-piece wings to keep the size of the shipping box within reason. Both planes use a flat-bottomed wing profile with a bit of dihedral to enhance the inherent stability that design brings to the models.

Both use a carbon fiber spar but the Flyzone Sensei FS has a plate on that spar that slips into both wing panels. The attachment points on the front and bolt plate at the rear secure the wing halves together. The Flyzone Sensei FS has down-turned wing tips that might give it a small edge with low-speed handling.

The Apprentice® S 15e also has a carbon fiber spar but uses front and rear plates that are secured by double sided tape to retain the wing halves. They do include two almost comically small pieces of double sided tape that can be put on the mating surfaces of the wing halves. They do mention in the instructions that you can use epoxy to bond the roots of both wings which is exactly what I did and anyone building this plane should do.

Battery Power

Both the Apprentice® S 15e and the Flyzone Sensei FS are powered by 3-cell, 11.1V LiPo packs. The Flyzone Sensei FS RTF kit comes with one 3200mAh pack and a 12V only balance charger. We added three 3000mAh packs to have enough power for a typical day of flight training. I already have the ICharger 306B and will use that for all recharging.

The Apprentice® S 15e RX-R kit had no batteries and no charger included. We bought 4 3-cell, 220mAh packs to provide an equal number of flights without having to re charge batteries.

We are going to begin flying both planes on a 5-minute timer and will determine changes to that period based on the amount of power left in the packs. We are looking for about 30% of the packs capacity to remain after the flight to avoid damaging the pack with excessive discharge. I can say that both planes are now up to 8 to 10 minute flights at more reduced throttle settings more common during training flights. Actual flight time might go even longer as we refine battery usage. Neither the Apprentice® S 15e or Flyzone Sensei FS come with timer-equipped radios so we will use the clock app of our cell phones to time the flights.

Final Tweaks

Before going to the flying field I went over both planes looking for loose fasteners and secure linkages. A battery was installed in both planes and their CG (center of gravity) checked closely to be sure the balance was exactly where the manuals called for. Both planes came out right on the suggested CG location without having to add weight. This is a plus for both the Apprentice® S 15e and Flyzone Sensei FS that will help new pilots not familiar with setting or checking the CG get started with a plane that handles properly.

I also checked control surface throws on both planes and found nothing that needed to be changed on either plane. The linkages are factory installed on both planes with the exception of one end of the aileron linkages on the Apprentice® S 15e. All of the surface throws came out very close to the specs in the respective manuals. Again no changes were needed which is another plus for a new pilot.

Apprentice® S 15e Maiden

By Mike Basmajian

Tom asked me to handle pilot chores for the Apprentice S 15e and handed me the DX5e. I regularly fly with a DX8 so the transmitter that comes with the RTF version felt both familiar and comfortable. Next was pre-flight checks. I looked over the Apprentice S 15e checking for defects and setup errors. Finding all was in order it was time to take to the sky.

Tom had provided four batteries so I worked one into the hatch on the underside of the Apprentice® S 15e fuselage and secured with the Velcro straps. The battery cover had a little difficulty closing but with a little attention to alignment and gentle persuasion it buttoned up and we were on our way to the flight line. I like the fact that the Apprentice S 15e comes with an external switch that arms the radio gear. That means you can load the battery and then move the plane to the flight line without fear of an “accidental” starting. Safety is paramount especially for beginners. At the flight line I turned on the DX5e and flipped the switch on the Apprentice S 15e. The plane went through an initialization sequence for the Sensor Assisted Flight Envelope (SAFE) Technology and armed the Electronic Speed Control (ESC). I checked control directions one last time and flipped the three position switch to Position 2 (experienced mode) and placed the Apprentice S 15e on the runway.

There was little wind to contend to so it was a slow advance of the throttle and in 15 to 20 feet the Apprentice S 15e was up and away gently climbing out. This “maiden” flight was uneventful at all throttle positions with easy turns with a few loops and rolls for fun. I have flown another Apprentice S 15e and this one was as easy and forgiving as the first with no bad tendencies noticed. The end of the first flight was as easy as the start with only throttle management needed to control the decent rate leading to a spot landing and roll out.

For a trainer this plane is really fun to fly. The next three batteries were as fun as the first and I couldn’t help but to play around a bit with the SAFE Technology. It seemed to work flawlessly but we’ll play around with it much more extensively next time.

Flyzone Sensei FS Maiden

By Tom Hintz

Unlike the Apprentice® S 15e the Flyzone Sensei FS has no radio switch so when using radios without a Throttle Cut you have to be very careful to avoid spinning up the motor unexpectedly. I believe a switch should be part of any trainer to make it a little safer for the new pilot.
I put the Flyzone Sensei FS into Advanced mode for the maiden flight and with full power it took a good bit of elevator to get it off of the grass runway. I also noticed that immediately after liftoff releasing the elevator let the nose drop way too much for comfort. Hold the elevator to get more altitude and speed and releasing the elevator produces no attitude change.

I noticed that the Flyzone Sensei FS seems to nose down during roll-out for takeoff and wonder if that nose-down attitude is faking out the stabilization somehow making it think that nose down attitude is level so when the elevator is released it tries to return to that nose down angle. After it flies for several seconds it seems to recognize the new attitude and this nose-down issue does not happen again during the flight. But it does happen on every takeoff. I am going to try a larger nose wheel to get the airframe more level during roll out to see if that helps this.

The Flyzone Sensei FS is very steady in flight at all throttle settings with no bad habits. The stabilization system works well in preventing the new pilot from over controlling the plane when in one of the two “learner” modes. Something I noticed that I like a lot is that the stabilization does not get in the way of using the rudder to assist turns or make corrections during landing descents. I am a big fan of using the rudder and with an instructor who understands rudder use this can be a big factor in favor of the Flyzone Sensei FS.

Landing the Flyzone Sensei FS is as simple as it gets. It slows to a walk without sacrificing control. With the CG in the suggested location the Flyzone Sensei FS needs just a light touch of elevator to settle in on all three wheels. Ground handling is a little bouncy on our grass runway but the Flyzone Sensei FS remains upright and controllable as I drove it back to me after landing. Wind is a much bigger factor in ground handling with the high wing. The Flyzone Sensei FS will fly in much more wind than it will taxi in!

Conclusions

Overall I think the Apprentice® S 15e has shown itself to be the better trainer but not by very much. The Flyzone Sensei FS is a good plane and the stabilization system is close to that in the Apprentice® S 15e. The planes seem very even in terms of power and flying characteristics. Turn off the stabilization and Mike and I were able to make low inverted passes as well as loops and rolls. That means the student pilot can learn more than simple flying before needing another plane.

Though it is a very good flying plane the Flyzone Sensei FS needs a switch to control the electronics and it needs a removable cowl like nearly every other plane out there to allow adjusting and repairing the nose wheel that beginners frequently “abuse” during the learning process.
It is also important to say that neither of these planes is truly crash proof. That is a sales pitch more than reality. The biggest factor is the plane flying away after the stabilization system saves it. Student pilots cannot be expected to bring a plane back after I gets some distance away from them as they almost always do early in the learning process. Also, the student has to recognize the amount of trouble the plane is in quickly enough to hit the rescue switch in time to allow enough altitude to complete the save. Both systems are surprisingly quick at making the save but they do need a little room to complete it.

Both the Apprentice® S 15e and Flyzone Sensei FS can be great trainers when combined with a good instructor. Both benefit from their size for flying characteristics, visibility and getting them to and from the flying field in today’s cars. They both also use reasonable batteries that won’t break the bank when the new pilot craves more flying time.

The Flyzone Sensei FS as shown in this review, no transmitter or receiver, cost us $328.95 (7-10-2016) including 4 battery packs and two extra propellers. The Apprentice® S 15e that came with the transmitter, receiver and a one battery pack cost $417.93 (7-10-2016) including 3 extra battery packs and 3 spare props. In the end, to get both in the air the money is going to be very similar. That still gives the Apprentice® S 15e an edge on the Flyzone Sensei FS.

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