Pulse XT 40 ARF
A Second Airplane That Offers Cardiac Thrills.
When the Hangar 9 Pulse XT 40 was brought home, the first thing my veteran of 5-years solo RC but 11-year old pilot asked was, “What’s that airplane supposed to fly like?” It seemed that his first impression of the sport model was that because it didn’t look like an Extra 300 or aK-5000-something what was so interesting about it?”
The fault is mine. Apparently I (the self appointed RC instructor and daddy) taught him that only cool aircraft look like those seen at the Red Bull air races. (Ed. Note: Michael, has he seen a Pattern airplane fly yet? That will change his mind!) My younger son Jacob actually thought the Pulse looked good and agreed to help assemble the model.
The Pulse XT is a very cool looking RC sport model, as far as “sport” models go. Its design, in more ways than one, is a leap beyond the average sport model. It’s designed by Mike McConville (MM) who is well known for developing everything from trainers on up to NATS winning International Miniature Aerobatic Club (IMAC) Giant-scale RC models.
The Pulse features modern appointments like an attractive tinted canopy, an easy-breathing fiberglass cowling, plus a must-have in my book if the model is to be attractive, sleek looking wheel pants. Because it’s an MM design, besides its looking attractive, in the air the pilot can expect treatment also enjoyed by Precision Aerobatic aficionados. “What’s that airplane supposed to fly like,” [pift!] indeed.
In a manner he could comprehend, I simply answered my son’s question by telling him the Pulse XT would be everything he wanted his trainer fly like, but couldn’t make happen due to normal trainer aircraft limitations. To you, the reader and fan of Model Aviation’s Sport Aviator magazine, the Pulse is what I would recommend as the perfect second RC aircraft.
Photo Courtesy of Horizon Hobby
Before you take my word for it (and you shouldn’t, but instead take our success story for what it’s worth), check out the other Pulse aircraft Hangar 9 and E-Flite offers. The various sizes of this model suit the Park Pilot on up to the serious Sunday flyer and fan of the larger 60-class of engines. Wouldn’t it be cool if they offered a larger 1.20 class size of this model? Just in – coming soon is the Pulse 125 from Hangar 9. I called it!
Photo Courtesy of Horizon Hobby
The Pulse XT (I have no idea what the XT stands for – perhaps extra tough?) 40 and 60 are the only models in the series to offer the user the option of either glow or electric power for the job of spinning the propeller. Okay, the 125-size will also. The point is that it’s nice to have options.
We debated quite a bit about how to review this model for you. The short version of the story is that we decided to build the model with a glow engine for everyone out there looking to enjoy the glow engines they already have. Even though the popularity of electric power is growing, it seemed to us that a lot of club members and returning RC hobbyist would consider the practicality and tradition of a two-stroke engine.
Photo Courtesy of Horizon Hobby
Photos Courtesy of Horizon Hobby
The correctly tuned and maintained glow engine is a treasure, and frankly the grunt from the engine sound and smell of the burned fuel captivates this author reminding that the weekends scooting through the air with RC club buddies is still a practice that’s alive and well.
Photo Courtesy of Horizon Hobby
However my sons’ enjoy the plug-n-play features that electric brings. But they explained that they would enjoy seeing how we “old guys” got it done when electric power barely could carry a lightly loaded sailplane for a minute and a half of motor run time. The electric version does make cowl installation easier though. Enough power ranting.
A low wing model is what an accomplished RC pilot moves on to after mastering (gotten board with?) the trainer that saw them through since their first flight. The Pulse XT 40, as I explained to my young son, is everything we wished a trainer model could do, when we learned there was more to RC piloting than just turns and the occasional loop. Not that the typical high wing trainer can fly itself, but we trust it to fly somewhat hands-off, and not to get piqued at the pilot if they should do something drastic like pull hard up elevator in a wide open throttle (WOT) dive. The result of which is sometimes a snap roll or a lock on into a death spiral.
The oversized straight wing of the Pulse series is the main reason why the airplane has forgiving characteristics; like that of an angel (hey, they have wings too!). The model is built light (I don’t know what angels weigh), and because it has lots of wing area (667 square inches to be exact), when you need to pull out of that dive, or just want to see what happens when you point the nose up and bend the sticks like silly string, the Pulse will forgive you after you cease gyrations, and then will show you the return path to straight and level flight. Sounds heavenly doesn’t it?
No, the Pulse doesn’t look like any particular scale model, but what it does have are nice appointments (Ed Note: I don’t know, looks to me like a fine homebuilt or experimental airplane. No matter, it looks great in the air or on the ground.).
The color scheme makes it visible from a long distance away and will help the RC pilot recognize upright from sideways; inverted from a nose-dive. That long tail and long, wide wing offer the RC pilot a lot to look at. Down the road, when you’re ready to try a short-coupled aerobat, the teachings of the Pulse will have offered the sense of confidence to better know how to perform the maneuvers, and not worry so much about what you’re looking at as you put the control sticks in the right spot at the precise moment. You’ll thank the Pulse for teaching the right moves. It is a great Advanced Trainer and aerobatic performer. (Ed Note: Although not designed as a Basic Trainer, I did teach a new pilot how to fly RC using a Pulse 60 last year.)
That long wing, because it offers a ton of area, also offers the drag to go along with it. To counter that sluggish aspect, a semi-symmetrical airfoil helps the model hold on to some of that airspeed. To help spin that long wing around the strip ailerons are made just a bit larger in area (wider actually) so that roll performance is crisp enough for the budding NATS competitor to try out slow and segmented rolls. (Ed. Note: The” NATS” are the National Aerobatic Championships held at AMA in July each year.)
Oh, that long tail; the longer the space between the wing and the tail typically means that the model will have smooth performance through turns, spins and tumbles. If you want break-neck snaps and tumbles, use the Pulse XT to practice. Should the pilot want more aggressive tumbles, then all that need be done is to crank in more movement on the oversized tail surfaces.
The elevator and rudder are sized and aerodynamically balanced to work well inside the performance limits of the standard sport servo. They don’t have double-beveled hinge lines for extreme 3-D rates, but that’s just fine. With what’s there however, a pilot can expect authoritative snap entry, and rudder performance that will help hold the model on a constant heading during a knife-edge pass down the length of the field and full-circle if asked (cause it will, and gladly).
All the above said, the designer plays with the numbers so that electric or glow-engine guys can be happy, and that either way the model balances on the Center of Gravity (CG) without having to figure out a way to bury a cannon ball in the tail or nose for ballast. That’s a tall order. Acting on this quest however, the Pulse finishes out being an attractive model.
The bit of dihedral in the wings will help the model find its own level in a straight pass – which easies a pilot’s work load. Because all airplanes have a pilot, either inside or on the ground, at least the Pulse has an attractive canopy to express the intent.
Just because simple is one of the Pulse’s features, Hangar 9 didn’t skimp on the “pretty.” The fiberglass cowling is sleek yet includes large openings for whatever power system chosen. To polish it off, an oversized spinner closes up the lines and leaves room for the 10-13 inch propeller to clear.
We (me and my sons) assembled the Pulse together over the course of a week. It was fitted with the recommended equipment by Hangar 9. We’ve had excellent experiences with the JR Sport servos and Evolution engines before and had no qualms about using those radio and power systems. In fact, the Evolution .46NT engine we first tested in the Pulse came from a totally worn out Hangar 9 high-wing Alpha trainer. These engines have a long life and that engine runs now as well as it did when fresh out of the box.
Photos Courtesy of Horizon Hobby
For the radio though, we wanted to go with modern technology; plus the safety and convenience of the Spektrum radio is something that’s spoiled us lately. We employed our Spektrum DX6i transmitter and bound it to one of the new AR500 receivers. It’s a tight package that offers full-range, weighs almost nothing compared to the standard receivers offered in the last five years and offers 2.4 GHz reliability.
Photos Courtesy of Horizon Hobby
For the battery we used a JR1100 mAh pack with five cells (6.0 volts). The higher voltage pack would deliver more power to the sport servos (making the output stronger and delivery quicker). The peace of mind an extra cell in the pack offers to prevent accidental brown-out problems and just the “snafu” that can happen sometimes is worth the weight of the heavier pack.
Our inspection of the kit contents revealed no packaging or delivery issues. Since there wasn’t space on the building board to get started right away, what we did was cut open the plastic bags containing all the Ultracote™ covered wood assemblies. What this does is similar to what a contractor would do if you’ve ever wanted hardwood flooring installed in your house. They deliver the flooring early, letting it sit for around a week so that wood can expand or contract (acclimate) to the atmospheric conditions. That way they can put the floor down accurately. In the case of our Pulse, we want the balsa and plywood material to acclimate to the workshop environment.
It was springtime in the mid-west when the Pulse was opened, so we expected the materials to shrink just a bit as the model was likely built in a more humid environment. If this is news to you, now you can understand why there are times why a model needs covering touch-up, and why sometimes it doesn’t. Models we assemble in the summer almost never need covering wrinkles removed, but in the winter they’ll inevitably “prune” up. Ultracote is a remarkable material and even if a wrinkle the size of Mt. Everest appears, it can be removed, usually never to be seen again.
Our Pulse developed a few wrinkles that were easily touched up. While going at it with the covering iron, some time was taken to inspect the straightness of the parts. On one wing panel, the aileron (solid strip material) had a bit of a twist to it. When the inside root portion of the strip was aligned with the trailing edge, out at the tip its end was low. This indicated a wash-in condition, which more obviously would make trimming the Pulse for level flight difficult. At slow speed we’d see that wing panel (the left one in our case) stalls first. There was about a 3/16-inch twist; not something I wanted to ignore, especially since it’s so easy to fix and so important to the flight predictability we were expecting from the Pulse.
With the aileron temporarily hinged, a clamp was used to hold the tip of the aileron at the root (I call it the home position). The clamp has soft grips and wouldn’t harm the surface. If you don’t have a clamp, borrow the hands of your favorite 12-year old son, or buddy that came over to check out your new model. At the wing tip, twist the aileron past its home position and with a hot covering iron gently apply heat up and down the length of the aileron; on both top and bottom surfaces. The heat will slowly loosen the grip of the covering and allow the twist you’re holding in the wood strip to reverse. Allow the surfaces to cool before releasing the pressure of the twist, otherwise the unwanted shape will return. It took me about 10 minutes of working the material before I was satisfied that the aileron was straight and would not twist back.
In the same regard as the ailerons, it would be good for the builder of any model to inspect the surfaces for warps and such. The covering iron is your friend. Even though you didn’t apply the fabulous covering job to your Pulse model, it is up to you to service and maintain the material that protects and beautifies it. I don’t recommend the use of a heat gun here as that broad application of heat can be difficult to control, and since the security of the seams is vital to the above twist correction technique, save the heat gun for shrinking insulation tubing around solder connections.
We found that the 40-page assembly manual was an excellent piece of literature and beautiful in illustrative form. Okay, it’s no Hemmingway or graphic novel from Marvel, but very little in the form of complaints were recorded. The only real issue I had was with the pushrods.
On the control surfaces’ pushrods, about half the area of the rolled threads needed to be trimmed away to prevent jamming against the control horns. This actually “cleaned up” the installation of the pushrods for a better appearance. Almost no threads are exposed on my pushrods, which makes them look custom made.
On the throttle however, I wished for just 10mm more rod material for comfort’s sake. The pushrod was just long enough, leaving only five threads biting the clevis at the carburetor and not a squint of slack at the EZ-connector. I’m whining aren’t I? (Ed. Note: Yeah, you are Michael. Most quality manufacturers try to make their pushrods to the exact length so the builder does not need to cut them. That is the case here as five rounds of thread on a throttle is more than enough).
I have a technique for preparing the hinge slots. Hangar 9 does an excellent job of accurately cutting the slots for the CAA-style hinges – not a one was found out of alignment. The slots are made after the model is covered, and whatever tool is used to create that slot leaves a slit in the covering showing the builder that the correct slot thickness was made. I’ve found that the sharp edge of the covering around the hinge slot makes it difficult for even thin CAA to travel past and into the wood material we want holding onto the hinge material. So what I do is dress the slot.
Besides following the manual for hinge installation and before fitting the hinges inside the slots, I take a MonoKote Trim-seal tool, fitted with the flat shoe, and point the edges of the covering inside the hinge slot. Just one pass of the iron’s tip is enough to do the job. The effect is that now the direction of the covering actually guides the thin CA into the slot, when before it acted more like a barrier. Knock on wood; I’ve not had a hinge failure. (Ed. Note: Good Tip!)
Assembly of the Pulse XT begins with the wings. These all-wood structures are strong with an aluminum tube inside fiberglass sockets for center support. They join together with wood dowel pins for alignment; no glue is necessary accept for the leading edge pins which are soaked with thin CAA after mounting the wing to the fuselage for the first time.
The pins fit very tightly inside the wing, and inside the receiving holes in the fuselage. We want the joint between the wing panels to stay tight so the lack of clearance in the pin fit was actually desired. Do not open up the holes in the fuselage to adjust for the placement of the wing dowel pins. Fit the pins into the wing without glue. The balsa leading edge is soft enough that compressing the pins is possible so that an exact fit can be obtained.
Once the wing is completely bolted in place, soak the leading edge pin joints with thin CA – it’s all that’s needed to hold them securely.
The aileron servos are installed semi-exposed into each wing panel. The elevator or rudder metal pushrod is temporarily employed here to help fish the servo lead plus its secured extension through the wing and out the hole through the center area sheeting. Kind ‘a neat idea when you think about it.
To ensure the alignment of the elevator halves to the stabilizer, I temporarily hinged the surfaces while the JB-Weld holding the heavy-duty joiner wire cured into place. Both right and left elevator halves were done at the same time so that equal gaps between the stab and elevator balances could be assured.
The coolest part about the tail is that once hinged, the entire assembly bolts into place. Not that I’ll be taking the tail off every time, but for assembly ease and maintenance, this feature is most welcome. I put safety caps on the exposed threads of the studs.
The alignment of our stabilizer and fin to the fuselage and wing were about as perfect as I’d want. If alignment adjustments were required, strips of covering or paper shims would do the job neatly.
Like the tail, the sturdy (where the XT comes from?) painted aluminum landing gear just bolts onto the fuselage (use thread-lock on these screws). Hefty 8-32 axles are mounted so that the grass field-friendly tires will center-up inside the wheel pant. The builder must locate and install the blind nuts that secure the bolts in place.
Be sure to follow the instructions and align the tear-drop shaped wheel pants with the thrust line of the fuselage. Mine are aligned with ground so it looks like they sag – my bad. Do the best you can pulling the blind nuts into the glass reinforced plywood plate. The reinforcement is very necessary, so I’m not complaining. You’ll be able to leave these wheel pants on when flying from grass.
I won’t bore you with the radio and fuel tank installations accept to write that the instructions won’t fail you. I did however make sure the fuel tank was padded enough to ensure it wouldn’t move around inside its compartment.
Since I was going glow with this model, I took the precaution of painting the fuel tank compartment and firewall with a light coat of epoxy resin. Any other area inside the radio compartment got a quick brush of fuel proofing to be on the safe side also. In doing this, I noted how thorough Hangar 9 was with the joinery and gluing. Don’t feel that the glue being used to fuel proof is also needed to add strength. I’ve probably done that, but it wasn’t needed.
I installed a small plate to mount the AR500 receiver with Velcro. As shown in the manual, it could have been wrapped with foam rubber and stuffed into the prepared compartment. I wanted to show off the receiver, and think the soft hook-n-loop fastener is good enough for vibration isolation. The battery was traditionally wrapped in foam and stuffed into the compartment located over the CG area.
Insert photos 40 and 41 here, centered
Engine installation is about the only non-ARF part of the project. The engine mounting part isn’t hard at all as every measurement is in the manual regarding its proper location. It’s the cowling that took some time to mount neatly. Actually, this issue is typical with all ARF models, but the bolt-on features and prefabricated aspects of the Pulse spoiled me quickly. I had to force myself to slow down and work out the cutout shape and location on the cowl professionally.
I made a cardboard template that loosely matched the outline of the engine. Every time the paper was brought to the engine the shape was modified until clearance and shape dictated the result. Making the mistakes on cheep paper rather than on a pretty painted cowl seemed logical to me.
The paper template was transferred to the cowling as accurately as possible, then the fitting process repeated for real. It takes some squeezing and careful twisting to get the cowling over the engine head and around the protruding needle valve. Thank goodness the fiberglass in the cowling is so flexible. What I have to do is almost pull the cowl over the engine head like a shower cap. Once it’s on though, lots of the engine is exposed so getting to the fuel line for filling and making carburetor adjustments won’t be an issue.
Right thrust is built into the Pulse to counter the engine’s torque forces during throttle transitions. This means that the engine’s crankshaft is pointed to the right and likewise so is the spinner’s position on the cowling. That is, it should be. On the Pulse XT 40, the cowling aligns perfectly with the position of the spinner. I was able to get the cowling nice and close to the spinner for that professional look.
Instead of using the metal screws provided in the hardware pack, I installed the cowl and canopy with nylon 4-40 screws. The nylon doesn’t chafe against the delicate surfaces of the clear canopy or painted cowl. I drill the mounting holes just like for the metal screws, but then I run a tap to cut threads. I can color dye the nylon to match, but that’s another article.
Using the photos in the manual as a guide for control linkage geometry, 100% travel on the end points of the rudder; elevator and ailerons produced better than the recommended high rate throw. No binding at all was apparent. I left this condition as the high rate. But to tame the sticks a little, about 20% Expo was added on all the surfaces so that small movements in the center area of the stick didn’t feel jittery. If this honestly is your second airplane, take the time to change the linkage connection points on the control horns so that high rate delivers exactly what it reads in the book. Their recommendations offer plenty of control movement for sport aerobatics.
I like the metal pushrods for tail and wing controls. They’re correctly located also in that no bends in the wire were needed for proper alignment. Not only did this make setup quick and easy, but most appreciated is the slop-free setup the effort produced. What I did have to do on the servos though is open up the linkage hole for the Z-bend with a #51 drill. Doing so removed very little material, but it was enough so that no binding was evident, which helps the servo work more efficiently.
I was happy to find that the Pulse XT 40 balanced smack dab in the middle of the recommended CG range. That usually never happens to me. There’s room to play with the CG if desired as the battery pack can be moved aft three inches, or forward inside the fuel tank compartment. As for lateral balance, the wing on the muffler side consistently fell softly that way; a condition left alone until after flight trimming progressed.
Running an Evolution engine is a treat. They start and run easily. The limiters on the SetRight™ needles narrow the adjustment area down so that the operator only needs to fine tune the engine and not worry that any needle change might bring harm (run too lean). You just can’t set it wrong – only better. Our well broken-in engine liked the high speed needle set in about the middle of the range, and the low speed needle against the aft stop, a rich setting. The goal being to set the engine for optimal power at full throttle and for smooth transition from low speed through the mid-range.
The APC 11x 5 in. propeller is our favorite as it provides the thrust of the popular 10×6 in., but its lower pitch permits the engine to transition more quickly. We haven’t tried the Evolution line of propellers yet, but they look like excellent performers as well. The recommended 11x 6 in. propeller would run more quietly. There’s enough ground clearance at the nose to practically accommodate a 13-inch propeller. Our normal sport fuel contains 15% nitromethane so that’s all that was tested. Evolution engines like less expensive 10% fuel also. Be sure to properly balance your propeller before final mounting.
Instead of sanding the rear of the propeller blade to achieve proper balance, I like to add a thin film (film, not a coherent drop) of thin CAA along the lighter blade tip. Spread the film with a towel before it sets.
What I don’t like about the glow burning Evolution engines is the amount of oil that blows through the front bearing. I suppose this condition is the reason I’ve never had to change a bearing in an Evolution engine; however the engine is a bit messy. Just another good reason the firewall and fuel tank compartment were coated with epoxy resin.
I didn’t take the time to pack foam around the gaping hole in the firewall for cooling air (if electric powered) and the fuel tank lines to pass through. To prevent problems down the road, good advice would be to plug those holes with scrap balsa wood, or film covering. Another smart thing to do (for you glow-power guys) would be to open up a vent hole in the bottom of the cowling for air to exit. Doing so will permit the crank case to run cooler.
Range testing the AR500 receiver proved beyond minimal. My only concern about the unit is the “boot” speed, six to eight seconds is about the time waited for the radio system to acquire (link). Relocating the long antenna had no effect on this condition. So far, after 30 or so flights, no problems have been noted. Just thought I’d mention it. (Ed Note: Actually the link or “boot” speed is a function of the transmitter. Spektrum transmitters require 3 -7 seconds to search all available 2.4 GHz frequencies and then select two to use for transmission. Then the 10-digit code is transmitted to the receiver which analyzes it and then accepts the transmitter’s commands. This process requires about 5 to 8 seconds to complete.) The 5-cell flight pack will provide plenty of voltage to the receiver so it should virtually never see a battery failsafe condition, as long as I do my part and keep an eye on the pack voltage.
Not many trainers are sold as a tail dragger, so getting used to the Pulse XT 40’s ground handling might be your first concern. A comfort to you should be the position of the main gear, and spacing between the wheels. Both of these dimensions enhance the stability of the model while rolling on the ground. What you’ll need to train yourself to do is to hold full up elevator while during the first half of the ground roll to prevent the nose from tipping forward.
This same preventive technique is used for take-off. With our healthy Evolution .46NT engine, I think a downwind take-off would be as smooth as the correct procedure which would be to take-off into the wind. Our model finished up with a dry weight of 5 pounds, 3.3 ounces – roughly a quarter pound under the weight range. That somewhat explains the 20-foot takeoff roll experienced on the first flight. Low rates were used.
Up elevator was carried on the ascent, along with left aileron and a touch of right rudder. The amount of up elevator trim needed to maintain a level cruise seemed somewhat excessive; between five and 10 clicks of trim. The elevator was level at the time of preflight. For some reason, the airplane needs up elevator trim. Later on, the CG was moved aft which reduced the amount of elevator trim required. The manual notes the CG range has ½-inch of latitude.
The Pulse can cruise neatly at about 55% throttle, yielding much the same airspeed as a typical trainer. So, the Pulse is easy to become familiar with if your only previous piloting experience has been with a flat-bottom, high-wing airplane. Race track patterns and figure-eights over the field should be the first goal of the new Pulse Pilot. Turns with just the aileron and elevator are smooth, just like a trainer. The Pulse is very good at showing the pilot how nice a coordinated turn looks. What will be noted is how a little rudder input wants to roll the wings, also like a trainer. The Pulse will teach exactly what the rudder is used for, pointing the nose.
Rolls were a bit barrel like, probably because the initial setup was nose heavy and the up elevator trim was being carried. Low-rate rolls were “trainer-esque” and looked better if the pilot pulled the nose up slightly so the entry into the roll gained the model some altitude first.
A half-roll to inverted required a quick input of down elevator to catch the nose from falling. Once the down input was in place, holding the inverted attitude was easy; a confidence builder for a pilot looking to get a better look at the top of his Pulse XT more often. There’s plenty of low-rate elevator travel to hold the Pulse inverted and maintain altitude through the “push” of the inverted turns.
One thing we enjoyed doing frequently was practicing rudder turns while inverted. When the model is upside down, rudder is reversed so brain training is required – to make a coordinated right turn, for example, left rudder directs the nose properly along with left aileron input. The Pulse will teach you lots of lessons like this.
Tracking through the loops, the Pulse drives pretty straight. It’s up the pilot to nudge the rudder in as needed to keep the path straight. Going back to the point about lateral balance, some attention there can improve loop and corner tracking. Still, on low-rate, there is enough rudder authority to keep the Pulse pointed straight on vertical climbs. The further toward the top, when the Evolution .46 tells you it can’t pull the model up any higher, the pilot will have just about all the right rudder available put to the stops. At that point, a stall turn to the left looks almost picture perfect when all the pilot need do is bring the rudder stick back to neutral. On high-rate, there is enough rudder movement to vector the Pulse through a right-hand stall turn.
Abrupt elevator input won’t hurt the Pulse; as commanded it will follow the pilot’s wishes. Some right rudder will dress up these inputs so the direction changes from horizontal to vertical look straight. On high-rates, full elevator input will stall the wing. Our model predictably broke to the right. The stall break was never experienced in a violent way exhibiting the designer’s intent to teach the aerobatic student good habits with as little risk to the airplane as possible. When the stall break occurs, the nose will drop, while the airplane hunts for airspeed to get the wing flying again. The experienced pilot can rudder and power the Pulse though the stall reaction. We’re learning all kinds of good things with this aircraft.
The more comfortable we became with the Pulse, the less often low rates were selected. Part of this is because higher Expo was programmed into the flight controls. Our final settings have 30% Expo in the ailerons, 40% Expo in the elevator, and 45% Expo on the rudder.
During normal flight, not much of the transmitter stick is moved – that’s our comfort level. Without having a rate switch to activate in this setup though, to perform an abrupt maneuver just takes the right stick input, not the flip of a switch first. It’s like automatic dual rates. On high, the aileron roll rate is about one roll per second, but that’s a guess.
With the CG moved back closer to the aft point (almost 3-inches from the leading edge) some of the up elevator trim could be removed which helped to straighten the rolls. Less down elevator was needed to maintain inverted flight. This seemed like a good safe spot for the CG – 2 7/8-inches from the leading edge to be exact.
Before getting into the more advanced abilities of the Pulse XT 40, let’s get the landing discussion out of the way. Right away the new pilot is going to find the landing speed a little faster than experienced with a trainer. This is normal, and perhaps the Pulse does carry speed a little longer than a flat-bottom trainer. The clean cowling, canopy and wheel pants make the model slippery to the air. The pilot has to plan the approach somewhat differently than with a trainer.
I’ve seen some pilots combat the fast-flight model landing by making landing approaches to the field way too far out from the landing zone. They use that time and distance to bleed off airspeed but the trouble is, with the model so far away it can be hard to see. Plus, what happens if you travel to a field that has only short approaches?
The best landing method is learned by first learning to fly the Pulse at a slow speed. Remember that the Pulse is designed to have friendly characteristics, which means that slow flight is inside its repertoire. Find out what that slow speed feels like to fly by doing a few laps around the field with the throttle in about the ¼ position. Hold enough back pressure on the elevator to keep the nose up and maintain altitude. You’ll note that banking through the turns wants to drop the nose quickly, so keep the turns shallow and help it out with rudder.
Banking the wings always dumps the lift so in slow-flight, don’t do it. Sometimes the throttle needs to be worked in order to maintain altitude (especially during banked turns), which is fine because what you’re practicing is keeping the model flying at a slow speed. Fly patterns over the field this way much like the landing pattern you’ll perform.
When you’re comfortable with slow-speed flight, then it’s time to land your Pulse XT the proper way. Establish slow flight before entering the landing pattern. Once there, guide the model through the landing approach being careful to manage the decent without gaining airspeed. Once the Pulse is over the runway, complete the landing, with wing’s level and nose a little high to prevent a propeller strike. That’s the three-point approach technique, but if you’re the hot-dog type, the Pulse is sturdy enough to handle high speed landings. In fact, if you fly from grass then you’ll find the authority of the controls with the Pulse a comfort as the large control surfaces remain affective even when ground speed is at a crawl.
I consider the Pulse to be a good entry into the aerobatics realm. It’s not really meant to excel at any one maneuver when compared to a high-end competition model, but it can perform all the tricks in the book in a recognizable fashion. (Ed. Note: And, it doesn’t cost 5-10,000 dollars either as a high-performance competition model does!) Its loops are probably the best of its tricks which can be performed inside three or four times the fuselage length, or about as tall as desired.
Outside loops need to be done with a little more finesse and with the engine speed at about half throttle. We found that the engine would quit during outside maneuvers when the throttle is below half – we’re likely pulling the fuel from the feed line which is a condition of the fuel tank position; it’s a little low. Nothing can really be done about that point accept perhaps to consider the position of the engine. (Ed. Note: What about removing the foam from under or over the tank. That would improve things.)
If the engine were mounted sideways or at a 45-degree angle, then the carburetor would be lowered in relation to the location of the fuel tank. In respect of this review project and convenience of the pre-located blind nuts in the firewall, we left our engine as recommended.
Because our carburetor is higher than the fuel tank, the needle setting has to be on the rich side to make up for the gravity draw lag. Even during full power inside and outside maneuvers an audible sound change can be heard – meaning that the fuel draw isn’t consistent. But with the right needle setting and flying style, the issue can be overlooked.
Advanced aerobatics are fun with the Pulse XT. It really is the trainer I always wanted because it’s super stable when I want, and aerobatically potent when I ask. This statement was made clear when we started testing the knife edge capability of the Pulse. Normally, sport models are disappointing in this aspect, especially when the average output sport servo is employed. I’m used to scale aerobatic models being very healthy when it comes to knife-edge flight, but find the overwhelming capabilities of those models stressful at times to fly. I just don’t always want to fly “all out” all the time. Every now and then a knife-edge pass is just pretty to see, and then I’ll want to go back to lazy rolls and looping around.
The Pulse is a non-stress performer.
Flying at high speed and up wind, only about half of full rudder input is necessary to hold altitude. Some proverse roll is apparent, but it can easily be cancelled by the pilot with cross aileron control. Using a Spektrum DX7 transmitter or above allows the roll coupling to be eliminated by mixing opposite aileron with rudder input.
The Pulse has the normal habit of pushing toward the landing gear with rudder input, so a little bit of up elevator is needed in the knife edge as well. Sounds like a lot of work just for one pass down the runway, I know, but none of the heading correction needs are sudden or violent. They appear softly which allows time for the pilot to find the correction system for the given condition. I’ll say it again; the Pulse XT 40 sure is a good teaching airplane. What’s better is that should the pilot input the wrong correction, the Pulse won’t violently react, but merely show the pilot in a calm manner those consequences. (Ed Note: The most effective control on any airplane is wrong rudder!)
The Pulse XT 40 isn’t much of a snapper. The snap entries look more like tumbles around a beer keg, and a large keg of beer at that. This is the consequence of designing a friendly airplane – it just doesn’t want to stop flying. Barrel rolls are pretty though and high speed tumbles, both positive and negative, are reminiscent of a gymnast twirling though the air. That includes a finish once the sticks are relaxed that will have the judges in your head offering 10s.
High rate input is needed to get the Pulse to spin. Again, it just doesn’t want to stop flying. Spin rates to the right and left, upright or inverted are all about the same; maybe inverted spins being slightly faster. Getting the Pulse to enter a flat spin was an exercise in futility.
Tail slides are fun to fly with the Pulse. Heck, just tooling around the field low and slow inverted with the Pulse is a kick-and-a-half. As mentioned early on in this story, the attitude of the Pulse is easy to recognize, plus the bright color scheme helps out a whole bunch also. I think the cockpit needs a pilot.
Quickening the Pulse:
I know, I know; Hangar 9 doesn’t recommend any two-stroke engine in the Pulse XT 40 larger than a .48, but I think they wrote that before Evolution came out with their new .52NX engine. Plus, in the four-stroke engine recommendations, up to a .82 Cu. in. displacement engine is allowed. So what’s the big deal about using a slightly larger two-stroke engine?
My two boys and a few friends all had the chance to fly the Pulse XT 40 and commented that the .46 engine was plenty of engine for the model. I couldn’t help but agree. The airplane has plenty of speed, climbs without argument and takes off from pavement or grass like a slingshot. So, what good would more power be for the Pulse?
Is that laughing I hear out there? More power is never an insult to the intention of any aircraft design. Normally the upgrade comes at a cost, typically in the form of added weight which changes the wing loading affecting the low speed performance handling. Luckily for us, replacing the Evolution .46NT with the new .52NX came with almost no penalties at all.
In fact, the .52NX weighs just an ounce heavier than the .46NT, and that ounce still didn’t bring our Pulse XT 40 to the minimum weight range. Installing the .52NX would be all benefit. Okay, maybe the .52 would drain the tank faster, but frankly the .46NT took longer than 12 minutes to drain the tank past the 1/3rd mark, at which point we’d land the airplane needing a break from all the fun. The stock tank on the Pulse would carry plenty of fuel for the .52 engine.
The only dimensions that vary between the .46 and .52 Evolution engines are the cylinder height, and length past the rear mounting lugs. The larger engine’s being longer in the back didn’t pose any problem; there was space to accommodate that extra length. The taller cylinder head worried me that the tight fitting cowling might not want to stretch over it during mounting. The mounting holes truly are an exact match, and the thrust washer, carburetor and needle valves all fit in the same place as the .46. I didn’t even have to adjust the throttle pushrod. As for the cowling, it just barely fit over the top, but I didn’t have to modify that either. Total time to upgrade the engine system: 30-minutes.
Since the APC 11x 5 in. propeller theories worked so well on the .46, for the .52 an APC 12 x 5 in. propeller was fitted. Again, this would offer good thrust at the lightest possible loading to the engine so that throttle response would be optimal. The CG was double checked before flying. To lighten the nose a little more, we went to a smaller 700 mAh 4.8V battery; a fresh one that does well under load, but one that will probably get field charged every third flight. That change put us back to our original flying weight, but now with more power. That sound is me giggling].
Call me crazy, but no break-in procedure was followed on the Evolution .52NX engine. It started running on the first flip, and idled smoothly. Slight adjustments were made to the high and low speed needles, then a short flight was performed; which I guess you could call the run-in phase. Upon landing the engine was noted as barely warm and no abnormal behavior from its running was noted.
On the subsequent flights the engine was peaked, and the fun really started. From a grass field the take-off run was the same short 20-foot run the Pulse needed to break from a paved runway with the .46NT running wide open. If that performance note wasn’t enough, the coolest thing was that just 20 more feet after breaking ground the Pulse XT “52” could be pulled to a vertical up line to a climb whose only limit was my eyesight. No joke.
With the extra power came the ability to not just fly the knife edge pass I enjoyed so much, but now I can climb in knife-edge. With a good headwind, even a knife-edge loop was possible. The larger engine also gave me the option to vary the speed of the Pulse, and not just drive it around with the throttle wide open all the time. The extra authority the throttle now had allows a pilot to point and drive the Pulse through maneuvers that have more defined lines, and a larger presence. And because there was no weight penalty, slow speed handling quality was maintained.
The Evolution .52NX engine is truly a gift to the sport model glow-engine enthusiast. If the Pulse is waiting in your shop to be built because of engine availability, do yourself a favor and put the .52 on your wish list. If the Pulse XT is not waiting in your shop, get one! You will love it.
For more information on 5this airplane, go to: http://www.horizonhobby.com/Products/Default.aspx?ProdID=HAN4100
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