3D RC airplane

3D RC airplane

If you’re looking to fly faster model aircraft, rc jets can give you the ultimate thrill and adrenaline rush!

 

Electric powered ducted fan (EDF) jets have become commonplace on our flying fields in recent years, and they offer an excellent gateway to the more serious gas turbine powered model jets.
But these turbine jets, however, are not for the beginner. They are very serious model aircraft that you have to work up to after gaining a large amount of radio control flying experience, and an equally large amount of cash. They are very serious business.

The good news is that the EDF jets are more affordable and many are stunningly realistic, making them an excellent choice for those who aren’t in a position to fly a turbine model.

The best introduction to flying true rc jets (i.e. with no propeller) are the aforementioned jets which use an electric ducted fan unit as pictured above.

A ducted fan is a small but powerful unit that houses a multi-bladed propeller, or fan, spinning at very high RPM (revs/minute). As it spins, air is sucked into a duct through one or more intakes in the fuselage of the jet, and then forced out the back of the jet at very high speed, pushing the jet through the air. A lot of thrust can be generated by an EDF although this is obviously going to vary from unit to unit.

EDF units are generally powered by high Kv brushless motors (high RPM) and need a high capacity/high discharge rate lithium polymer battery pack (Li-Po) because of the high current that they draw.

As previously mentioned, Ready To Fly foam EDF jets have really taken hold in recent times and the number of good quality RTF EDFs available has increased dramatically, to the point where it’s as common to see such a jet on the flying field as it is a plane or helicopter – that wasn’t the case a few years ago when rc jets were very specialised models.

Some manufacturers have gone all-out to produce striking models with fantastic scale detail,

 

Foamie EDF jets like this aren’t cheap and you do need to be an intermediate pilot to fly one safely – in other words they’re absolutely not for the beginner rc pilot. But definitely something to work towards!

It’s a good testament to the hobby that electric ducted fan rc jets like these have now become so widely available and relatively affordable, in exactly the same way that electric rc helicopters have.

But with that said, it’s important to know that starting out in the radio control flying hobby from scratch with an EDF jet isn’t wise. Gaining flight experience with a conventional trainer airplane is the thing to do; the faster flying speeds of jets can catch out the beginner rc pilot who hasn’t yet developed the reactions and co-ordination needed to fly any rc aircraft type.

Micro RC jets
Like all other model types in the radio control flying hobby, rc jets have shrunk in size in recent times.

Leading the way is the Horizon Hobby brand E-flite with their UMX range. The latest jets feature Horizon’s AS3X™ stabilisation technology which helps fight wind gusts and the natural twitchiness of small model aircraft.

These micro-sized rc jets are excellent fun around the park, and are quite cheap to buy. You don’t really need the same level of flying experience as for a larger jet, but their relatively fast speed does mean you need to have built up the necessary reactions and co-ordination before attempting to fly one.

Gas turbine RC jets – the real deal.
To many fliers an rc jet powered by a true model jet engine represents the pinnacle of radio control flying but, as mentioned earlier, such an rc jet like the F14 Tomcat in the following video is definitely best left alone until you have:

1] lots of confidence…
2] endless hours of rc flying experience and…
3] lots of money!!

Even a smaller size model gas turbine unit can cost a four-figure sum, and that’s before you’ve purchased the jet, radio gear and all the essential accessories. So a twin engine model, like the Tomcat in the video, is going to cost you a lot!

But rc gas turbine jets are the ultimate in radio control flying. Large scale jets look and sound amazingly realistic in the air and a properly built and well flown scale model is very impressive to watch in action.

If you ever get a chance to see some of these on display, then do.
RC events that feature such aircraft are becoming more and more common, and it’s worth trying to locate one if you can. Top UK radio control pilot Ali Machinchy, now living in the USA and working for Horizon Hobby (a big loss to the UK rc scene!), always puts on an amazing display and flies large scale jets – indeed, he’s one of the world’s top show pilots.
If you ever get a chance to watch him, please do! If you don’t, then at least enjoy this video of him flying a large scale (1/5) English Electric Lightning at one of the UK’s top shows…

Here’s the video (reproduced, copyright unknown)…

Model RC jets on a simulator.
If you’re more like me than Ali, then there is a cheaper option for trying your hand at flying proper gas turbine powered rc jets…

Phoenix sim – Red Arrow HawkA good quality rc flight simulator can give you a realistic jet-flying experience, without breaking the bank. I have the Phoenix flight sim which features several turbine jets. A screenshot of the BAE Hawk is shown to the right.
You can learn more about rc flight simulators here.

One advantage rc jets have – whether virtual or real – is that they are not so adversely affected by wind like many rc airplanes are, due to the higher airspeeds and sleeker aerodynamics. This is a big plus when you’re flying, although obviously every model has its own limitations and flight characteristics.

A downside is that because of this speed they need extra airspace; a faster flying model requires much more space for turns and aerobatic maneuvers than a slower flying aircraft, and you need to remember this when flying jets of any size. This consequently brings in the problem of your jet being flown at a distance where it’s not always easy to see exactly what it’s doing; that in turn brings the serious risk of disorientation – a proven killer of rc aircraft of all types!

But flying any type of rc jet is always an adrenalin-filled experience and with radio control and electronic technology forever improving and reducing in cost, more and more rc jets will become available still, even for the lesser-experienced amongst us.

So, how does the Freewing F-14 Tomcat fly? In short, pretty darn awesome! The distinguishable shape of the F-14 looks menacing in the air and the flight characteristics are fantastic. As discussed in my assembly review of the airplane, there are some tricks I’d highly recommend in setting the airplane up which at the end of the day, provide a great flying airplane. This comes from not just flying this particular airplane, but also flying the Freewing production prototype (stock and tailerons only) as well as the twin 70mm F-14 I helped design, test, and fly for my folks at JetHangar.com. They have all exhibited similar characteristics and fly very much the same.

In my assembly review, I covered the installation of two 6s 30C 5800 mah batteries that I’m using in the airplane. To maintain the CG, the battery area was modified so that the batteries could be pushed as far back as possible up against the swing wing carry through spar. This maintained the CG well per the manual (87mm measured back from the leading edge of the forward most hatch cut on the overwing fairing hatch) which has shown to be about perfect! Also the manual provides a trim elevator setting (31mm measured from the top of the fuselage to the leading edge of the tail) that is a very good
starting point for flight. Note that there is nothing to worry about regarding CG with wings extended vs wings swept. I found that the airplane could use just a touch more back pressure for flying around, but for me not enough to warrant adding any kind of mix. Also, the CG doesn’t change as a result of the change in wing position either. These have been the case with every F-14 Tomcat I’ve flown and are two of the most common questions I regularly get.

For the control throws, this is where it’s interesting. The control system on the full sized Tomcat uses the tails as the primary surfaces for commanding pitch and roll. The wing has spoilers to augment the roll control with the wings extended which are then disabled with the wings swept. Lastly, there are full span leading edge slats and trailing edge flaps. Now, in the case of the Freewing F-14 in the stock configuration it’s setup a bit differently than the full sized airplane. There are outboard wing ailerons and inboard wing flaps in addition to the taileron surfaces.

All of the servos in the airplane are routed into an electronics board which automatically sets the mixing between the outboard wing ailerons and the tailerons. That’s all well and good and works well for flying with the wings extended, however in this stock configuration the wing ailerons remain active while in the swept wing position and that causes problems. Disabling the ailerons in the wing swept position is absolutely necessary for a good flying model in the swept wing position. So, to get around this, we must program the two aileron servos separately by directly plugging them into the receiver (bypassing the electronics board) and programming their function independently (more discussion on this below). Note that the airplane flies well with the wings extended in the stock configuration, but I found the high rate aileron recommendations much too hot for my liking.

Since we’re programming the wing ailerons independently, I’m using the ailerons more as the function of the turning spoiler like the full size by having them act trailing edge up only to help augment the roll control provided by the tailerons when the wings are extended. Also, since we’re playing with the ailerons in this way, the scale geek in me figured why not set the airplane with full span flaps while we’re at it for a little more scale swag?! By doing this, I was pleasantly rewarded with a beautifully landing airplane that when executed right lands extremely softly! Lastly, having two rates on the tailerons between wings extended and wings swept is an absolute must! I mitigated that through some switch assignments such that the rates change automatically depending on where my wing sweep switch (and subsequently wing position) is. I talk through the radio programming methodology a bit more below. Note that based on the Freewing wing sweep actuators used, the airplane does not have a mid sweep capability, i.e. the wings can only be commanded to fully swept or fully extended.

So, after many flights, here’s what I have converged on for control throws. They suit my style of flying and should be a good starting point to tune to your desired feel. Keep in mind these are purely linear with NO exponential (I’m not a big fan of expo typically). Also, there is plenty of authority running tailerons only, I’ve flown the airplane in that configuration and it works very well. However, the roll stick input requires just about max deflection for a decent 360 degree roll.

Wings Extended:
Roll – tailerons 1-1/4″, wing ailerons mixed with 3/16″ trailing edge up only
Pitch – elevator 1-1/4″
Full span flaps
Partial Flap – 5/8″ with a 3/16″ up elevator mix
Full Flap – 2″ with a 1/2″ up elevator mix

Wings Swept:
Roll – tailerons 1/2″ (no wing aileron throw)
Pitch – elevator 1-1/4″

DOWNLOAD THE SPEKTRUM DX FILE HERE!

f14-dual-2

RADIO PROGRAMMING METHODOLOGY
My go to radio system is the Airtronics SD-10G which is an excellent radio at an excellent price. It’s a 10 channel radio with a ton of capability which made programming the F-14 Tomcat fairly easy. Since radio systems vary, I figure it best to talk through the methodology I used here which should work across most systems I would hope. In order to do what I’ve done exactly, a minimum of 9 channels are required so that the ailerons can be programed individually to function with the flaps as well as act like a turning spoiler. If limited on channels, then it limits the functionality of the ailerons to work only as ailerons (2 servos connected with a y-harness) or as flaps (flying airplane tailerons only and connecting the aileron servos through a y-harness with a reverser on one side). I’ve flown the airplane tailerons only and it flies very well, so if channel limited and you want the full span flap, that is a very good option. That said, I do like the addition of the outboard aileron functionality as it adds a little more roll responsiveness with the wings extended that you don’t get flying with tailerons only.

So, utilizing the 9 channel setup (I have a 10 channel receiver in the airplane) the aileron servos were plugged directly into the receiver using 2 available auxillary channels (bypassing the stock electronics board, all other channels are plugged in and remain in the stock setup). This maintains everything essentially stock with the exception of the aileron servos only.

Ailerons as Flaps
f14-flapI first setup the ailerons to work in conjunction with the flaps. This was done by assigning the two aileron channels to the flap switch and simply adjusting the servo direction and the servo position (using the end point adjustments) at each switch position to match the flaps in each down position.

Ailerons as Turning Spoilers
f14-ailTo actuate the ailerons as a turning spoiler, I used two separate channel mixes, one for each aileron servo aux channel), that were mixed to the standard aileron channel. This channel mix was then assigned to my swing wing switch such that the channel mix is active with the wings extended and then inactive when switched to the wings swept position (disables the ailerons in the swept wing config). Within the channel mix is where the deflections of the aileron servos are set and adjusted. Since I’m using them acting trailing edge up only, it required only adjusting a single end point for each mix/servo (approximately 25%). Again, this is within the channel mix only. Note that since this is outside the traditional aileron setup and aileron channel, these channel mixes do not work in combination with the traditional aileron dual rates. However, some creative switch assignments and an additional channel mix or two could probably create this. I didn’t find this necessary since I only wanted the ailerons active with the wings extended and tuned the rates to the desired feel I wanted with my tailerons on high rate.

Taileron Rates with Wing Position
In addition to the above, I assigned my aileron dual rates to the swing wing switch (in addition to the normal dual rates switch) so that with the wings swept, the tailerons automatically reduce to low rates. This is important as the airplane will otherwise be extremely touchy in roll with the wings swept if the tailerons remain at high rate. The airplane will be on its back if you simply breath on the stick!

ESC Calibration
The last item of business before flight is to calibrate the speed controllers to the transmitter (procedure is available here). By following the procedure, the ESCs will tune themselves to the transmitter settings and ensures that each fan is producing the maximum amount of thrust each time it’s powered on. If you change the transmitter at anytime, then the ESCs should be recalibrated. I didn’t do this calibration on the production prototype but did on this airplane and this airplane has notably better performance! So, this is an important step!

One thing to note, I noticed some thrust robbing openings in the exhausts around the taileron servo cutouts and where the motor wires exit into the fuselage. I sealed these up by removing the fan hatches and adding some packing tape f14-sealsinternally over the taileron servo and using hot glue to seal up around the motor wire exit. After placing the fan hatches back onto the fuselage, I used a long dowel to completely seal the packing tape over the hatch areas too. Any leaks in the exhaust ultimately reduce thrust and performance. Though it may be small, every little bit helps for maximum efficiency of the system.

 

 

FLYING THE FREEWING F-14 TOMCAT
Flying the F-14 Tomcat is an absolute blast and with the 5800 mah packs, I can get about 5 minutes of pretty hard flying if I want to push it. Currently, I keep the timer at 4 minutes and fly the airplane as hard as I like and the packs measure out at about 3.78v/cell. Every F-14 I’ve flown has been a great flyer and the Freewing F-14 is no exception. The F-14 configuration as a whole is just a great platform for an awesome flying airplane. Plus, you can’t beat the shape of the F-14 in the air. It’s one of those iconic airplanes that is unmistakable…though it always seems to conjure up quotes from the movie “Top Gun” whether you want them or not…”No my ego doesn’t write checks…I have an ATM card!” 😉

Here’s a full flight video from a fun flying day at the PVMAC Prado Air Park. Thanks Brent Hecht for manning the camera for this flight.

With the wings extended, the airplane is a wonderful flying machine that flies easily and will handle most of what you throw at it (rudders are very effective though, so be aware). The airplane is plenty fast enough and the vertical is quite good. To give you an example, I’m able to perform a 1/2 cuban 8 return from takeoff just like the full size which is a great deal of fun! Recently I’ve gotten into performing a roll on takeoff followed by a 1/2 cuban 8 return and the airplane handles it like a champ! The slow speed handling is excellent as well and the airplane will visually give you an indication of the onset of stall. As you get slow, the wings will start to rock as you approach the stall speed which is your indication to apply power and increase the speed. This is another characteristic of all F-14s I’ve flown. Note that this is less prevalent when slow and with full span flaps.

f14-flt-1

 

 

 

The airplane flies just as easily with the wings swept too. Flying circuit after circuit in the swept wing configuration is easy with low rate taileron and the airplane carries speed well overall in that configuration. Pulling hard tight turns does bleed the speed off in this configuration, which is a characteristic of a delta type platform so keep that in mind.

 

 

Overall, the trickiest part I have found is managing the transition time from wings extended to wings swept and visa versa. Once you’re aware of it though, it’s easy enough to plan for. As noted in the radio setup, the tailerons are automatically set to switch to high and low rates during wing transition. However, this does not occur proportionally to the speed of the wing transition (I wasn’t sure I could program this into the radio). As a result upon hitting the swing wing switch, the wings transition over a second or two, but the taileron rates immediately change. So, when the wings sweep back, the taileron rate will initially start out sluggish (they switch to low rate) and become increasingly more effect as the wings transition aft. Conversely, when sweeping forward, the taileron rates are immediately high and touchy and then become less sensitive as the wings transition forward. It’s really not a big deal, but is something to keep in mind. You’ll quickly become aware of it when you experience a quick roll response as the wings sweep forward. It’s easily manageable…in fact, my favorite maneuver has become rolling while the wings transition like they used to do as part of their airshow demos.

Call the Ball!
At last, the world can rest easily as there is a nicely done F-14 Tomcat ARF that is affordable for most folks. The $580 price tag is an excellent value and you get a well engineered and great flying model. It’s foam which has it’s limitations (if you’re a builder, my folks have a kit at JetHangar.com), but even so it’s pretty nice. I can’t help but think how awesome this airplane would be after stripping it down and refinishing it…but for now, we’ll keep it stock. Now guys, remember, as these become more prevalent and more Freewing F-14 flight videos come online, remember to post responsibly…the internet really doesn’t need another RC jet video featuring the “Top Gun Anthem” or “Danger Zone” playing underneath it…it’s hard to believe, I know! Although, if you’re up for a challenge, how about a few videos featuring “Take my Breath Away” or “Heaven in Your Eyes.” 😉 I mean, they are from the Top Gun soundtrack afterall!

Here are a few more videos I’ve captured of some friends flying their Freewing Tomcats. It really is a very cool foam jet and we’ve been having a lot of fun with them!

 

 

BONUS! Here’s video of the last F-14 Tomcat demo at NAS Oceana in case you’re looking for some maneuvers. 🙂 Who doesn’t love the Tomcat?! I remember the Tomcat demos being one of my favorites when I was a kid at air shows. The full size airplane was an absolute beast!