Hangar 9 New P-51D Mustang ARF
Hangar 9’s New
P-51D Mustang ARF
By: Frank Granelli
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Flight testing and reviewing a WW II fighter airplane ARF may seem unusual for Sport Aviator. After all, this publication is designed for beginners and pilots flying their first, second or third airplanes. Very few WW II fighters would qualify.
Such airplanes have higher wing loadings, how many ounces each square foot of wing must carry, than most second or third airplanes. Scale fighters, a “scale” model is a smaller copy of a full-size airplane, roll very quickly since their “parent” airplane had to be a “fast roller” to stay alive. Being designed for high speed flying, fighters also quickly pick up airspeed once the nose is lowered. Finally, many fighters will snap roll out of a steep turn if too much elevator is applied during the maneuver. This is especially a problem during the approach phase.
Reviewing this advanced airplane is one result of Sport Aviator’s reader poll. The majority of readers requested that we extend our review pool to aircraft that may be harder to fly than our more usual first, second and third aircraft level.
This airplane assembles quickly and easily despite having retractable landing gear because Hangar 9 put a lot of thought and effort into its construction. Most beginners could assemble it correctly and in a short time. But the flying is strictly for the experienced pilot as this is a Mustang after all.
Photo 1A
So, why review this particular Mustang? Because, this airplane is really the Mustang PTS (Progressive Training System) in its final, non-trainer form. Sport Aviator reviewed the Mustang PTS in its Basic Trainer form and found it to be an excellent Basic Trainer. Now we are looking at the sport scale version.
Photo 1
The trainer form features deployed flaps for extra lift, a 3-bladed propeller and landing gear speed brakes that slow the airplane and drooped leading edges that convert the airplane’s symmetrical airfoil to a flat bottomed one for extra lift in the outer wing panels to help prevent unwanted snap rolls.
Photo 2
Photo courtesy of Horizon Hobby
As the pilot’s skills improve, some of these devices, speed brakes first and then raising the flaps, can be removed. Once the pilot is comfortable flying the Mustang PTS in this configuration, (the pilot’s “second airplane”), then the drooped leading edges can be removed. The final step is to exchange the 3-bladed propeller for an APC 11×6 in. design. Airspeed dramatically increases with that last exchange.
With all the “training wheels” removed, the Mustang PTS is now the pilot’s “third airplane” all in one package. This new Hangar 9 ARF aircraft is that “third” airplane. It is the exact same airframe that is used in the P-51 Mustang Mk II PTS version with all the training adaptations removed. (Note: I am not sure if the PTS wings have the retract cutouts under the covering.)
We borrowed the Mustang Mk II PTS photo from Horizon Hobby since Sport Aviator did not review the Mk II version (Amazing Grace). Everything was the same between the Mk I (Marie) airplane except for the MK II’s installed 2.4 GHz radio system and its plug-in wings which lightened the airplane a few ounces. The Mk I used a one-piece wing design. We did not feel there was enough difference between the two versions to warrant the usual very detailed Sport Aviator review.
But we will be looking at this aircraft from the view of a pilot looking for their first scale aircraft or their third sport airplane after graduating from a Basic Trainer and a low wing “second” airplane such as the Hangar 9 Pulse XT, SIG 4-Star or Goldberg Tiger aircraft series. This airplane is definitely not meant as a first or second airplane. But it is a very excellent third or first advanced scale airplane.
Pre-Assembly
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The colorful box contains a Ready-To-Fly (RTF) airplane in its Almost Ready to Fly (ARF) configuration. The entire tail group bolts together just as does the RTF version. The tail wheel is attached and hooked to the rudder. Instead of a one-piece wing, this airplane uses the more modern plug-in two piece wing design. This saves about four ounces of weight over the older wing style.
One great feature that Hangar 9 includes is the clear cowling used for locating the engine cutouts. This is a great aid for making the cowl openings needed for engine clearance and proper operation.
The only “building” required is mounting the engine and its systems, fitting the cowling and installing the radio and landing gear systems.
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As you expect, the hardware package is almost complete and almost all that is needed to get the airplane flying. Why the “almost”? Well, as difficult to believe as it may be, the kit does NOT include a spinner. My guess would be that although the RTF Mustang PTS trainer includes a spinner, it is designed for the three-bladed propeller that airplane uses.
Few more experienced pilots would use the thee-blade propeller as it detracts from a sport aircraft’s performance so a spinner designed for it would not work. Hangar 9 offers a Du-Bro 2 3/4 inch red spinner for this airplane for only about $8. This airplane used a Tru-Turn aluminum spinner and it looked and worked fine.
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Depending on the features you incorporate into your Mustang, this airplane can use from 5 to 8 servos. If you plan to install the flaps (2 servos) and the retractable landing gear (1 servo), then be sure to use a large capacity, 5-cell battery. This is especially important if plans are to use a 2.4 GHz radio system. One great advantage of an ARF aircraft over a RTF is that the pilot can make these choices.
The battery selected for this airplane is the JR 2700 mAh 5-cell Ni-MH battery. Always use a 5-cell battery if you plane to install a 2.4 GHz radio system. The included hardware contains everything needed for either glow engine or electric motor installation.
Opinion: This is a sport ARF aircraft so the choice is yours. But flying experience has proven two things. First, this aircraft much prefers flying with the wheels retracted. Maintaining the line of flight is easier, rolls are more axial and climb performance is much improved. The airplane flies well with the wheels down but performance is not as precise.
Flying with the fixed gear might be better than flying with the retract gear down since the wheel well openings are covered. But if experience serves, the fixed gear Mustang PTS still exhibited tail wagging and flight disturbances at different airspeeds caused by having the gear exposed to the airflow.
I know this as we twice hand-launched the original PTS version (2-bladed propeller) with the landing gear removed. Flight was superb, smooth and without any tail “wiggling”. This was to see if installing retractable landing gear was worth the effort. It was, but then the newer plug-in wing Mk II version appeared making that installation information obsolete. We discontinued the project.
Second, installing working flaps greatly expands this airplane’s slow speed performance. Since their outer wing panels are highly tapered, Mustangs are not noted for their slow speed turning performance. Excess elevator application during turns tends to cause a Mustang to snap roll into the turn. Using the flaps reduces this condition while greatly slowing the approach and landing speeds.
In summary, the flaps cost only two extra servos and do greatly improve the airplane’s performance ands tractability. The optional Robart retractable landing gear does cost $150 plus a servo. But Oh Boy, is the performance improvement worth it! If you must, install the flaps now and then save up for the retractable landing gear.
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The optional retractable landing gear system is an air-operated, all-aluminum system made by Robart. Robart manufactures some of the best retractable landing gear systems available in the modeling world. The cost for this system is more than reasonable at $150.
The landing gear uses the much stronger 3/16- in. diameter wire and has stood up to a few abusive landings without difficulties. Complete instructions are included but hook up is pretty simple. However, there is a minor problem using the system with 2.4 GHz radios. It is minor but present and will be detailed in the flying section.
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I seriously debated the glow vs. electric power choice and couldn’t choose. So, I decided to weigh everything that I intended to include in this airplane. Everything was weighed for the glow version and it totaled around seven pounds. (The final weight was actually 7.07 pounds so I wasn’t too far off initially.)
The electric power version was only 2 ounces heavier but would maintain that extra weight for the entire flight (electrons have mass but not much at ~ 9 x 10 -31 kg) {I looked that up!}. The glow version would start to lose weight as soon as the engine was started. The glow engine, complete, cost only $90. The electric version would cost $330. That would mean that I would have had to forget about getting the retracts.
If you wish to power the Mustang suing electrons, the top hatch makes electric power operation easy. Use the 46 Brushless Outrunner Motor, 670Kv by E-flite (EFLM4046A by E-flite). The recommended ESC is the 60-Amp Pro Switch-Mode BEC Brushless ESC by E-flite (EFLA1060). The recommended battery is the 3850mAh 4-Cell/4S 14.8V Pro Power 30C LiPo by Thunder Power RC.
In the end, I settled on the near- amazing Evolution .52 NX glow engine. This light weight engine is powerful yet user-friendly to the point of silliness. It turns the Evolution 11 x 6 in. propeller at 12,000 rpm and idles at 2,200 rpm. After break-in, the idle needed just 1/4 mixture turn towards lean to sit idling nearly forever.
Of course, using the glow engine means cutting out the cowling but isn’t that what the clear cowling was to be used for? I did not consider using a four-stroke engine because of the $300 price tag and the extra ounce of weight. At 7 pounds, I was trying to keep the weight as low as possible. But the four-stoke engine would have had a great sound. Pilot’s Preference!
Basic Assembly
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Fuselage:
The Mustang uses the popular “clamp-on” aluminum motor mount positioned at a 45-degree angle from the vertical. I considered mounting the engine inverted as was done to the Pulse XT 125. But that would have placed the fuel inlet and needle valve location far too high while inverted for reliable inverted flight. The stock location proved the best after considering all the alternatives. That made engine mounting simple.
Full instructions on how to mount an engine on this mount and keep it centered are included in the Sport Aviator article “Engines 101 – Part Two”. Just remember to lock the motor mount bolts in place with thread locking compound.
The fuel tank is factory assembled. Make sure that the vent line points upwards when the airplane is upright. Use a red fuel line for the vent line (it goes to the muffler pressure and is there fore “red” hot). The green line goes to the engine’s fuel intake.
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Install the engine on the mount so that the thrust washer, the serrated round thing that the propeller mounts against, is 4 9/16 in. out from the firewall. Make sure the engine is properly aligned in the mount at that distance.
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Use an index card or part of a shirt cardboard or other scrap card stock and tape it to the fuselage so that it extends past the engine head. Mark the engine head’s location on the card as shown. Then cut out the card so that it fits around the engine head. Fold the card back against the fuselage, still taped into position. Remove the engine
Mount the clear plastic cowling onto the fuselage and then unfold the card template over onto the clear cowling. Mark the engine cutout location onto the clear cowling. Remove the template and the cowling.
Photo 15
Reinstall the engine minus the high-speed needle valve. Make sure it is centered and the proper distance from the firewall. This is its final location so take time to make sure it is correct. The clear cowling should now fit over the engine and can be mounted in place. If not, trim the cowl engine opening until it fits.
Photo 16
Center the clear cowling on the engine and tape into place as if it were the final cowl. Mark the areas for the muffler, carburetor, throttle valve, high speed needle valve and remember an opening to adjust the low-speed needle valve. Remove the clear cowling and place it over the painted cowl.
Mark all those cut out areas onto the painted cowling. Remove the clear cowling and cut out the areas just marked. I prefer to cut “small”, well inside the lines, to start. Then gradually enlarge the cutouts using a high-speed rotary tool and a sanding drum.
Here is a hint. Do the engine head cutout first. Once the painted cowl slips over the head, bolt it in place. Make sure the thrust washer, with spinner mounted, is centered against the cowling. If not, check your engine alignment again to make sure it gets centered.
Photo 17
Once the engine is aligned, replace the painted cowling with the clear one and re-check all the cutout marks you made. Make any adjustments needed. Recheck the clear cowling against the painted cowling’s holes you marked previously. Then make all the necessary cutouts. Having that clear cowl is a big help.
Photo 18
The throttle rod servo mounts into the factory installed servo tray. The servo mounting holes are factory drilled. Install the throttle pushrod and hook it up to the servo and engine. Adjust the throttle so that it is fully open at full throttle, just barely closed at low throttle and low throttle trim and slightly open at low throttle with the throttle trim in the “half” position. This final position will be trimmed later at the field.
Install the cowling with the screws provided. Mount the muffler using plenty of thread locking compound in both the engine holes and on the bolts. Install the propeller and spinner. You have purchased a 2 3/4 in. spinner separately as previously detailed, right?
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The final cowling step is to mount the pre-painted exhaust stacks into the screw holes in the fuselage and cowling. The left side stack just screws into position as per the instructions. The right side, the muffler side, stack is supposed to be shorter according to the instructions to allow muffler clearance. But, it is not.
The right side stack is the same length as the left side. So, if you position the right side stack enough rearward to clear the muffler, it extends backwards further than the left side by a noticeable difference.
I cut the stack as indicated in photo 19, saved the front curved piece, and then glued it back onto the front of the right piece I just cut using medium CAA. Photo 20 shows the results. If you do not want to do that work, just locate the muffler side stack further to the rear. Both stacks must be dismounted whenever the cowling needs to be removed.
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Moving rearward, the next step is to install the radio system switch. The Mustang has cutouts for a regular size switch and for the larger combined switch/voltage testing and charging jack. We used the latter, the JR “Chargeswitch” No. JRPA 004. To me, being able to test the flight system’s battery capacity allows extended flight operations and a certain degree of safety. Plus, I can now always recharge the battery at the field. You will want to fly this airplane a lot so recharging is a good thing.
Cut out the covering over the switch opening of your choice. Then fold the reminder towards the interior. Bolt the switch in place.
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The Mustang uses a long, removable top hatch that covers the radio and tank areas. On the exterior, the hatch includes the pilot and canopy. Position the pilot 4.5 inches forward of the rear of the cockpit. Mark the area, remove the pilot and drill two 1/16 in. holes as shown under the pilot area. Glue the pilot in place using epoxy.
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Lightly sand the interior of the canopy edges as shown. Apply canopy glue around the lower edge of the canopy rim just sanded. Use low tack masking tape to hold the canopy in place while the canopy glue dries (about 6 hours).
Canopy glue, or RC 56, is used for two reasons. First, it sticks to plastic coverings and the canopy when many adhesives, including epoxy, will not. Second, the glue applies as white; making it easy to see missed areas. But then it turns totally clear when fully dried and will not yellow over time.
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Back at the tail, the rear flying surfaces betray their RTF heritage inherited from the H-9 Mustang PTS. The stabilizer and vertical fin/rudder assembly (even the tail wheel is mounted) bolt together into the fuselage. Two long threaded “bolts” extend from the vertical fin through the stabilizer, rear fairing and fuselage; exiting the bottom of the fuselage. Two lock nuts secure the assembly in place.
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This attachment method has proven itself over time. Still, there can be some problems with it after several hundred flights. If you wish, it is NOT required, you can use some epoxy here. This is an ARF after all, not an RTF, so you are allowed to use adhesive without being struck done with lightning from the modeling gods! Install the fin and stabilizer and then mark the stabilizer covering where it meets the fuselage.
Tape those lines and cut the covering, a heat knife works best here, about 1/16 in. inside the lines.
Photo 30A
Remove that covering. Note the hardwood insert for the bolt-on system. This is a far more durable bolt-on mount system than the older balsa systems once used in RTF aircraft.
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Install the fairing and do the same for the top of the stabilizer and the bottom of the vertical fin.
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Lightly brush some 30-minute epoxy onto the now bare surfaces, then bolt everything firmly in place and allow to cure. Make sure that the elevator horn is on the lower left side.
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Install the rudder and elevator servos into their positions in the fuselage servo tray. Note their alignment as per the instructions. Photo 35 shows a neat way to insert the brass grommet protectors into the rubber servo grommets. Use a 2/32 in. nail set and insert from the bottom.
The brass inserts are important but are many times omitted by many modelers because they can be difficult to install. They serve an important function as they prevent the grommet from being crushed by the servo mounting screw. A crushed grommet does not provide the vibration protection needed to protect against servo failure.
Precut elevator and rudder control rods are included. The shorter control rod is for the elevator and the longer moves the rudder. Install the pushrods, clevises and hook the inside ends to their respective servos. Adjust the clevises so that the rudder is centered and the elevator neutral when the transmitter is switched on and the trim tabs in the centered positions.
The fuselage is basically complete except for the retractable landing gear mechanism. Now it is the wing’s turn.
Wing:
Photo 36
Four of the five servos in photo 36 go into the wing. The fifth servo mounts inside the fuselage retractable landing gear servo tray. There’ll be more on that one later.
The black pieces still inside the plastic bag are for fixed gear installation as are the black landing gear legs. The legs slip into the mounts and are held in place with Allen locking bolts. The mounts bolt into the same recesses designed for the retract gear. If you want to settle for fixed gear, then do this installation.
But here is a word of caution first. We have flown the Mustang with the gear down. We did not try the fixed gear installation so the wheel well openings were exposed during our tests. The airplane was not very happy with this arrangement at medium airspeeds. There was a good deal of yaw instability but nothing that the airframe could not handle on its own. But a little yaw “hunting” was apparent. Yaw instability decreased as the airplane flew faster or slowed down.
The Mustang PTS does have fixed gear and no wing openings. Its slight yaw instability became apparent only at high airspeeds; probably because of its giant wheels. The conclusion is that using the fixed gear without wing openings will most likely not affect the airplane’s handling.
But who wants to fly a Mustang with the gear down? Not me! However, there is a caveat here. Ground handling, especially potential nose-overs, is poorer when using retracts than with the fixed landing gear.
Photo 37
Use a modeling heat iron to seal the covering around the aileron and servo openings.
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The servos mount to two hardwood blocks that you epoxy onto the aileron hatch cover to fit your servo. This is a common system in many ARF aircraft. I have never had a problem with this system nor heard of one but… It still makes me a little nervous. After mounting the servo blocks with epoxy, I always drill a small hole through the hatch cover as shown in photo 38 and then screw the blocks down using a spare servo screw. This is probably overkill but it makes me feel better.
Mount the servo to the hatch as shown, install a 12-in. servo extension wire onto the servo wire, tie it together, and then use the factory installed string to pull the wire through the wing and out the top of the center section.
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Clamp the aileron in the neutral position as shown. Then install a clevis and nylon keeper on an aileron pushrod. Adjust the pushrod length so that the aileron remains centered when the clamp is removed and the radio system switched on. Note in photo 41 that there are two pushrod lengths. The longer pushrods are for flap control and the shorter ones work the ailerons.
Photo 42
If you choose not to have working flaps, install the fixed “flap stay” into the wing as shown using epoxy. You still have to make up flap “pushrods” to keep the fixed flaps fixed in place. Except, now the pushrods don’t push, only hold.
To be honest, install the flaps if you can. In fact, my own opinion is that if you do not plan to use flaps, do not build this aircraft. The flaps not only increase the Mustang’s lift and improve slow speed control; they help prevent “snap outs” caused by excessive elevator application during slow speed turns. Landings are slower, easier to control while lift off from grass is much better using half flaps. Even the instruction manual agrees on that last point.
Photo 43
Hook up the flap system exactly as done with the ailerons except a servo extension wire is not needed nor is the factory installed draw string. The wing should now look like this one.
The next step is the retract installation. This is the first time Sport Aviator will be discussing retractable landing gear installation, but certainly not the last. If this is your first retractable landing gear installation, use the retracts specified by the manufacturer as modifications during your first installation pose too many complications.
The gear chosen for this airplane is the Robart HANP51 system. This is a compressed air operated system so you will need to get a model air pump. I suggest getting one with the air gauge. Be sure it can pump up to at least 100 psi pressure.
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Hangar 9 includes a retract Template that is unique. The Template greatly simplifies cutting the wing openings for the retracing gear leg and wheel. Bolt the template into the retract mount as shown. Make sure the small bump, actually the clearance required for the gear’s spring loop, faces rearward. Then use a felt tip pen and trace around the template.
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Use a hot knife or sharp hobby razor blade and cut down the middle of the covering inside the lines you have drawn. Gently peel back the covering and tape in place out of the working area as shown using low-tack masking tape. Cut out the wheel well area leaving about a 1/4 in. overlap into the well. Re-install the template, bump rearward, and again trace out the template on the wood itself.
Photo 48
Remove the template. Use a sharp hobby razor knife to cut out the wood along the lines you drew. Install a landing gear and, using your hands to release the down lock, retract the gear and slip it into place. The gear leg should easily fit inside the opening.
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Remove the gear and the masking tape. Cut the covering around the wheel well every 1/8 in. or so (photo 49). Use a model covering trim iron or the tip of a standard modeling covering iron and attach the covering overlap, now cut into tiny “pie” pieces, over the wood and onto the bottom of the wing skin inside of the wheel well. Continue installing the covering back over the openings you cut out until the covering is sealed inside as shown.
Photo 51
If this airplane is glow powered, purchase some fuel proof paint in black, aluminum or Chromate Green color. Coat the bare wood inside the wheel and gear leg openings with 5-minute epoxy thinned about 50%. After that dries, paint it with the fuel proof paint. This seals the area from fuel and oil damage. Exhaust residue will get into the wheel wells so don’t forget this step.
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The retract servo, air inlet valve and the actuating switch are all mounted onto a plywood tray that bolts into the fuselage. Before installing all the equipment, reinforce the glue joints where the valve mount joins the tray with medium CAA filets. The actuating rod shown in photo 53 is provided with the Mustang.
However, the directions suggest using a ball link on the valve end and this airplane will be switched. A ball link will protect the valve against side loads that might cause uneven wear and leakage.
Photo 54
Special Note: If you are planning on using a 2.4 GHz system, there is a special precaution you might have to take. Some 2.4 GHz radio systems, including the Spektrum DX 7 used in this aircraft, often send a few servos all the way to their end travel points during the switch on procedure. This occurs regardless whether the transmitter is turned on before or after the receiver.
Normally this is not a problem as the affected control surfaces then immediately return to their neutral positions. But this system requires that the retract servo be restricted to only about 25% of its possible total travel distance during normal operations because the actuating valve can travel only a very short distance.
Unfortunately, this particular receiver-transmitter combination sends the retract servo and one flap servo to the ends of their possible travel, regardless of their programmed travel end points, during the switch on period. The result is that the retract servo pulls the valve mount out of the tray leaving the gear in the extended position.
Photo 55
Photo courtesy Du-Bro Products
To prevent this, use one of the “throttle protectors” sold by Du-Bro (Control Over-Ride Servo Saver) originally sold to make throttle setup easier in the days before computer transmitters (http://www.dubro.com/hobby). Use both springs.
Now the retract servo can travel all the way in either direction during the switch on procedure without damaging the valve or its mounting tray.
The only additional precaution you now have to take, if your servo travels to the retract position, is to remember to raise the nose of the Mustang so the wheels are off the ground before you turn on the receiver. This last precaution may not be totally necessary as the gear seems to have a safety that prevents it from retracting when the wheels are on the ground.
If you are using a 72 MHz system, forget all of the above as servos do not usually move during switch on.
Plumb the rest of the retract system as shown in the instructions. A nice feature about this system is that air pressure is used only to raise the gear. Strong springs and a mechanical lock hold the gear in the “down” position when air pressure is either lost or released.
Most tail wheel model designs insure that the main gear’s axle position be located under the wing’s leading edge. This helps to prevent nose-overs on grass runways.
When using the fixed gear, the large tires are located in front of this location making nosing over and poor ground handling impossible. However, like the Hangar 9 Pulse XT 125, the retractable landing gear’s wheels on the Mustang are located behind this position. Ground handling is poor and frequent nose-overs are possible regardless of how much “up” elevator is used during taxi and takeoff. The airplane can even nose over at the end of a landing run as the speed drops to near zero when flown on grass runways.
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To solve this problem, make a 1/16 inch plywood shim as shown. Position it under the rear landing gear mounting block as shown. This shifts the landing gear axle forward by 1/2 inch and does not bother the retracted positioning. Taxiing on grass is now possible. Landings and takeoffs are far easier to fly and do not exhibit serious nosing over problems. This is the same fix used on the Pulse XT 125 and it proved very successful there as well.
The flight battery and receiver mount in the “hatch” just forward of the servo tray. Install the plywood tank “lock” once the receiver and battery are installed. Hangar 9 provides a foam “tray” to protect these components.
Finish up all the little pre-flight tasks such as installing the landing gear doors, labeling the aileron/flap wires and placing the air line connections outside the fuselage through the holes provided. Depending on the size of the air connectors, their exit holes might need to be enlarged just a little. Follow the manual; it proved an excellent guide throughout the entire construction.
Setup
Balance the Mustang at the 3.5 inch point back from the leading edge. The manual allows for the Center of Gravity (CG) point to be as far rearward as 3 7/8 inch. For the first flights, no matter your experience level, do not go that far back. Stay at the 3.5 point. You might even consider a 3 3/8 inch CG point for the fixed-gear Mustang for the first flight but we have not tried that. If you do, increase the elevator travel to 9/16 inch up from the 1/2 inch suggested in the manual.
Laterally balance this airplane. If you have not done this before then read the Sport Aviator article “Ready To Fly? … Maybe” in the Flight Tech Section. How to laterally balance an airplane is explained on page 5.
Lateral balance here is very important. The Mustang’s outer wing panels are highly tapered and have a reduced area. Without the Mustang PTS’s drooped leading edge tips that convert this section of the wing to a flat-bottom airfoil while increasing wing area, the Mustang does not well tolerate a “heavy” wing. Loops are far off track and the airplane even tends to drop the heavy wing at slow airspeeds.
Three 3 inch finishing nails in the left wing tip were needed to balance this airplane as the muffler and part of the engine head is on the right side. Once balanced, flying qualities greatly improved.
All control surface movements were set as follows.
Control Surface Manual Actual Exponential
Aileron 7/16 in. 1/2 in. 45%
Elevator 1/2 in. 9/16 in. 40%
Rudder 1 1/8 in 2 in. 75%
The Manual recommends using high and low rates. I stopped doing that years ago as I always seemed to have the rate switch in the wrong place at the wrong time. Instead, I use exponential to quiet things down around center and during gentle maneuvers like slow and point rolls and during takeoffs. But full travel is always there when needed for spins, stall turns, snaps, emergencies and ground steering.
The Evolution .52 engine, a great choice for this scale fighter, idled at just 2,200 rpm and turned the Evolution 11 x 6 inch propeller at 12,400 rpm richened after break in to 12,000 rpm at the top end. The idle mixture on this engine needed only about 1/4 turn lean to make the engine sit there barely ticking over without end. Fuel used was Powermaster (sadly now passed from the modeling scene) 15% nitromethane sport fuel with 18 % oil (castor/synthetic blend).
At The Field and In The Air
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This is a great looking airplane. The red tail and wing tips do help pilot visibility but be careful flying on those silvery, early spring days if you are in the colder parts of the country. The airplane is always visible regardless of sky conditions but you may have to waggle those silver wings once in a while on light, cloudy days.
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Hold full up elevator when taxiing on grass. Taxiing is possible in short to medium length grass. If the grass is long, carry the airplane to the takeoff spot.
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Takeoffs are easy but do not try the gentle, slow acceleration technique. Apply just less than half throttle while holding full up elevator. The airplane will move forward.
Then apply full throttle while still holding full up elevator. The nose will dip ever so slightly and then pull back to level as the airplane accelerates. With this engine, acceleration is very brisk. Once the nose starts back up to level, reduce the up elevator input back to a normal takeoff setting; about 1/4 or so.
There is very little pull to the right meaning almost no right rudder is required for a straight takeoff using this technique. The Mustang fairly leaps off the ground in about 50-75 feet on grass. Taking off with half flaps deployed reduces the ground run to about 40-50 feet.
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The Mustang can hold an extremely steep climb angle; possibly as steep as 60 degrees, and still accelerate. But one of the magic moments with this airplane occurs right after takeoff as those wheels tuck themselves up and into the wing.
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Then the Mustang seems to leap ahead and steadies down into a solid tracking airplane. As the airspeed increases, the Mustang just becomes more solid in the air. Rolls are fast. Depending on airspeed, the roll can be completed in a second, maybe less.
But the roll remains almost axial and controllable. Minor down elevator is required while inverted to keep the nose up during that part of the maneuver. But the airplane is certainly not nose heavy at the 3.5 in. balance point.
Here are some thoughts about airspeed and maneuvers. This is an advanced airplane; it is a scale fighter in its truest form although its “trainer” heritage does sometimes show through. Still, its maneuvering abilities depend upon its airspeed to a greater extent than does the usual Sport Aviator aircraft.
This is a fast airplane. How fast is fast? While we have not yet “clocked” this airplane, the original Mustang PTS with all the training gear removed and an APC 11 x 6 in. propeller mounted on its Evolution 46, not the more powerful 52 as in this airplane, was clocked at 106 mph in level flight.
Even for an experienced pilot, 106 mph is on the fast side if not truly fast. This airplane seems to fly in the same top speed range and may even be quicker. As you can surmise, rolls can be fast and axial, loops large and well tracked, inverted flight rock steady, verticals long and high at these fast speeds.
This is an exciting and capable airplane to fly but it is meant for more experienced pilots. Remember that this is the “third airplane” version, the graduation edition, of the Hangar 9 PTS. Once those leading edge droops are removed, this airplane flies like a Mustang, both very, very well and also a little bad.
Photo 67 |
Photo 68 |
Inverted flight is rock steady at speed. Outside loops can top 200 ft. in diameter and track fairly well needing only a little rudder correction in the first half of the loop. Outside snap rolls and avalanches are clean and easy to control.
Photo 69 |
Photo 70 |
Whether coming or going, this airplane seems to bring its grounded pilot up into the air with it. Old, faded movies come back to life with each steep Chandelle. Tight climbing rolls invoke images of desperate battles fought over strange, cloud-shrouded lands far, far away in time and space. The airplane is an icon brought back to life for many pilots to enjoy by Hangar 9.
Photo 71
But, stay awake! At slower airspeeds, mistreating the elevator during a steep turn will cause the Mustang to roll into the turn and drop its nose into a near graveyard spiral. Recovery is easy and the ailerons are effective at even the slowest airspeeds. But, as with almost all scale, single-engine fighters, too much elevator at slow airspeeds can cause headaches.
At cruise, about half throttle, even full up elevator application with the wings banked about 90 degrees results in no wing drop, snap roll or tuck under. The airplane just flies the too-tight turn waiting for the pilot to notice it is not happy in this situation. The tail may hunt a little but the Mustang’s trainer origin allows such mishandling without penalty.
The stall is gentle and very predictable. The wing wiggles a little then the nose drops straight ahead. Releasing up elevator immediately stops the stall. Recovery is then also immediate and does not require power. During prolonged deep stalls, aileron control is fully effective and the airplane just sinks rapidly. Recovery requires only releasing the excessive elevator input.
Upright spin rotation is, well, is fast using both ailerons and rudder. But leave out the ailerons at the stall and use rudder only. The spin slows to a very pretty slower rotation with the nose down only about 35 degrees. Right spins recover by just releasing rudder and elevator. Left spins need half a turn to recover. Opposite rudder application to stop the rotation is not required.
Photo 72
Inverted spins must be made using both rudder and ailerons. The inverted spin rate is about half that of upright spins. Although the inverted rotation speed is slow with the nose pointed downwards around 70 degrees, the airplane needs a half turn to stop the rotation.
This airplane can fly any maneuver you can plan for it. From cruise, applying full throttle in the climb arc results in 4-500 ft. verticals. Rolling verticals from the same start can reach 300 or more feet high. Rolling verticals to the left are nearly axial. But right rolls upwards have some adverse yaw. This will have to be trimmed out during future flights.
Slow rolls at speed are easy to fly and can extend 300 or more feet with no change in flight path. Knife-edge flight pulls strongly towards the canopy using left rudder while opposite knife-edge flight requires very little elevator mixing.
Photo 73
Once trimmed, point rolls are nearly impossible to fly incorrectly. The final test flights, the total is 20 so far, were spent using the Mustang to practice 8-point rolls for this year’s upcoming Pattern Competition season. With the knife-edge walking trimmed out, the Mustang’s 8-pointers helped me improve my timing and positioning. The point rolls need to be flown at nearly high speed but near-level knife-edge flight is possible for about 200 feet using top rudder.
The Mustang is a sport scale aircraft and not a Pattern model. It is nearly 50% faster and all the maneuvers are smaller, but its flight characteristics are exact enough (though not truly precise) that it could be competitive in Sportsman.
It can fly any non-3D routine its pilot desires except prolonged knife-edge flight starting from level. But raise the nose first and then roll into knife-edge and the airplane will hold that angle for as long as required in any set maneuver.
I couldn’t find a non-3D, recognized maneuver the Mustang could not perform. The airplane may require rudder input on some of the more exotic routines, but they are flyable. Surprisingly, the Mustang will hold a high speed vertical without right rudder until nearly the very top. But it exhibits a torque yaw when accelerating from low to high cruise.
I mixed in about two points right rudder at mid-throttle only to remove this slight yaw tendency. The airplane will pull out of vertical dives but only very slightly. 1 point of down elevator mixed with low throttle quickly solved this tendency. If you are only sport flying the Mustang, you will not need or even notice such fine point trimming.
Photo 74 |
Photo 75 |
With the flaps and gear extended, the Mustang will comfortably fly at around 30 mph. Slow speed flight without the flaps deployed can show a few weak spots but always remains controllable and honest. A few approaches were flown with only the gear extended and the flaps raised.
At the base-to-final turn, excessive “up” elevator was applied. The nose first moved too quickly into the turn but the wings remained level, an honest warning signal every experienced pilot will recognize, and then dove down and into the left turn. But, the Mustang gave more than enough warning allowing the pilot to release the excessive elevator.
Both ailerons and rudder remained effective during this intentional Accelerated Stall. Recovery was immediate and the airplane did not lose more than 10-20 feet of altitude. With flaps deployed, the Mustang was as gentle and predictable as its trainer sibling. The wings remained in their position even with elevator application approaching “full up”.
Applying full up elevator in the turn did result in an Accelerated Stall, even a Basic trainer will stall with this abuse, but the wings stayed “in the turn” and the airplane refused to snap or do anything “unfriendly”.
Photo 76
Fly the final approach, flaps deployed, keeping the nose about 15 to 20 degrees below horizontal. Keep a few “clicks” of power in. Let the airplane descend using throttle to control altitude and elevator for airspeed management. Do not use elevator alone to control the glide path. Approach speed is about 25 mph.
Photo 77
As the airplane reaches the 3-foot high point and is still gently settling, raise the nose to just above level. Gradually reduce throttle and the Mustang will gently begin to reach for the ground
Photo 78
The main gear will touch first in this attitude. But the tail drop follows almost immediately as up elevator is still held in. Once the airplane settles into the three-point and starts to slow, gradually input up elevator until holding it fully up. This prevents the nose over tendency.
This nearly 5-foot wingspan airplane performs very well and is a value at only $200 for the kit. It is attractive and will expand any pilot’s abilities. While this airplane works as a “Third” airplane, even the most experienced pilots will enjoy exploring its performance envelope and pushing it right to the limit.
The Hangar 9 P-51 Mustang ARF is also attractive and will turn many heads at the field. Use the Evolution .52 for the best vertical performance. I have heard that Evolution has just introduced a .60 engine in the same crankcase size so that could be stuffed into this airplane. But the high speed and vertical performance is already astounding and the bigger engine could produce too much torque and then need to be trimmed out. Still…
For more information about this great looking and superb flyer, go to: http://www.horizonhobby.com/Products/Default.aspx?ProdID=HAN4440
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Notable PositivesExcellent aerobatic abilities Extremely fast assembly Very good looks Fast flyer Great 3rd airplane Descended from a trainer Notable NegativesRetract wheels too far rearwards Retract mechanism must be adapted for some 2.4 GHz systems |
Short URL: http://masportaviator.com/?p=1051
Posted by Frank Granelli
on Filed under Featured, Sport, What's New.
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