FPV P-51D Mustang - 960mm

Details

About

This is a Park Flyer grade airframe most popularly enjoy by VLOS flying around the club field or designed to fly around small park. Mini size frame wing spanned at 960mm powered using small 1300mah 3s 35c max.  Originally manufactured by ART-TECH  sold the model as "P-51D Mustang" as RTF.  Re-branded version available at HobbyKing.com as PNF which slash the price by half making it more affordable but some nice scale decals are missing and extra Hobby King label are stamped on the back fuselage which user can manually removed easily by peeling.  By late 2013 the latest batch at HK site include optional retract bay and flaps ready.  The inspiration to fly it as scale FPV platform came from my childhood dream: "I love Mustang and i dream to fly one someday".

As a normal park flying VLOS its a fun and floaty plane to fly.  Enough power to do radical aerobatic maneuver almost 70% what my PITTS SPECIAL can do and both came from the same manufacturer with completely the same flight hardware setup (except Pitts have single 1x servo for 4x ailerons as opposed to 2x servo on Mustang).

p51d 7

 

 

Model specification & setup

Airframe type: Scale low winged- War-birds
Branding/Manufacturer: ART-TECH
Model name variant: P-51D Mustang
Material build: EPS foam
Wingspan: 960mm
Length: 840mm
Stock airframe weight: 500 gram
Full FPV flying weight: 715 gram
Aileron: 2x 9g servo
Elevator: 1x 9g servo
Rudder: 1x 9g servo
ESC: 30A
Motor: DAT700/700kv (3s)
External BEC: 5A/5V
Propeller: 4 blade 10x8" scaled "HAMILTON STANDARD" replica
Radio receiver: Frsky telemetry 8ch
Radio receiver antenna: diversified DIY di-pole antenna
Battery: 1x 2200mah 2s~3s 25c
Center Gravity: 1/3 from the front leading edge of the wing.

 

 

My DIY FPV specification

Camera: 808 #16 V2 HD with live video out
Secondary camera: None
Camera pan/tilt mechanism: 9g HXT900 (180 deg mods)
OSD: Arkbird OSD/RTH/GPS V2
Flight Control board: Arkbird OSD/RTH/GPS V2
Video transmitter: Boscam 5.8ghz
Video antenna: DIY tuned Clover Leaf
Battery: Shared with main.

 

Building

Its not easy to build and setup FPV inside such a narrow and slender fuselage.  Getting the right CG (Center Gravity) placement to avoid "Pendulum effect" is a cautionary where builder should not ignore.  The airframe by manufacturer specification only allow fitting of max 1300mah 3s lipo, however further research through on-line r/c community the airframe able to accept bigger more capacity lipo pack at optimal 2200mah 3s 35 size on its nose cavity thus the power provide 1.2kg of thrust through its upgraded huge 4 bladed scale propeller.  The remaining sensitive electronic hardware are located at further rear tail to compensate the overall CG, to distance RF interference and placed almost lower baseline of axial roll CG.  Unwanted RF interference are lowered by removing unwanted metal or solid object and uses thin wire to reduce current wastage, light weight and RF influences.  Most of my build works concentrating removing redundant wires, pin, plugs and remove other unnecessary weight to make the total flying weight of the airframe lighter, floaty, less weight inertia during dive 29aimpact and improve overall motor thrust stamina.  Since i like to keep my plane looks as scale as possible, all hardware and modules are well hidden inside fuselage & away from normal external view to preserve the original looks of a real P-51D Mustang  without looking ugly with protruded cameras, antenna and etc like typical FPV glider setup that ruin the ecstatic looks of genuine War-birds, at the same time keep things aerodynamic for the airflow.

Just like my Drifter Ultralight this mustang also installed with ARKBIRD OSD/GPS/RTH as my fail safe and insurance against signal loss or anything beyond my control since i like to fly long distance.  This system will take control autonomously or autopilot mode if radio and video signal are lost and make a "U-turn" back to my control.

FPV building level difficulty/rating: Hard/Advanced (1/10)
FPV equipment setup grade: Professional
Building hours required: 52 hours
Skill required: Soldering/Foam cutting
Critical issues during installation: Keeping the weight to minimal and crampy/narrow fuselage.
Required additional mods/must do improvement: Beef up the motor mounting and propeller balancing.

 

p51d 9 

 

FPV flight characteristic and performance

If flying an FPV glider is like driving a TOYOTA PRIUS then i must say  flying this P-51D Mustang is like driving a LAMBORGHINI DIABLO of the skies.  Rare and exotic FPV airframe ever to grace over the clouds.  It has surplus of power and endurance to travel far places and easily climb at any altitude at will, survived the most harsh humid weather condition ever encounter by any platform and the smallest airframe to gain the same flight characteristic and achievement of common bigger sized FPV/UAV platform in the market.  Yet it uses only smaller amount of power supply to sustain throughout the flight when compare against bigger platform that uses more than 3300mah >> 6000mah at 4s configuration wing spanned at minimal 1.4 meter at 1.5~2kg.  This platform break the common traditional FPV beliefs that smaller non-glider like plane not able to FPV longer range, this airframe proved the opposite.

When i first time fly FPV in scale War bird behind the cockpit, the aura of FPV flying is completely different than conventional FPV glider like platform.  Since i'm flying like what real pilot does in cockpit seating position; the view are very restricted especially the frontal nose obstruction, ground viewing is limited,  judging the AOA level is difficult, difficult to take-off & land, unpredictable "sink-rate" and ground proximity flight is very challenging.  Recommended FPV pilot to pilot this plane are the ones that have experience flying a low winged FPV plane or at least experienced on a "Super Cub" like platform.    When it comes to long range flight and ability to bail out from harsh weather condition the P-51D Mustang took 1st place among my fleet of FPVs with ES Drifter in 2nd and Pitts comes in 3rd.  Its the Jack of all trades.


Minimum level of VLOS flight experience required/flight-hours: Advance(420 hour)
Minimum level of basic FPV flight experience required/flight-hours: Intermediate (215 hour)
Nature of platform handling experience/skill required: Glider, scale and acrobatic flight(Professional)
Self leveling capability in thumbs-off stick situation: No
Take-off & landing difficulty: Medium
Hand launch: No
Max speed: 90~110~km/h
Min speed before stall: 15~32km/h
FPV flight/radius: 4~12km max (given above FPV spec/setup)
Max altitude: -
Bail-out/fail safe recovery altitude limit: 30~50m
FPV safe distance range for testing: 800~1000m (Open field)
High angle of attack (AOA) tolerance limit before stall: 30 degree (32km/h)
Ground "STOL" (Short Take Off and Landing) capability/thrust%: Takeoff 20m (65%)/ Landing 20m (25%)
Altitude climbing power/thrust%/AOA angle: 1 sec/per-meter at 75% thrust/45 degree
360 degree turning radius clearance/holding pattern: 15m
360 barrel roll/loop acro flight: Yes (Aerobatic)
Control expo - aileron: 45% (low to high)
Control expo - elevator: 45% (low to high)
Control expo - rudder: 45% (low to high)
Control end point - aileron: 75% (low to high)
Control end point - elevator: 100% (low to high)
Control end point - rudder: 100% (low to high)
Flight time: 25~35 min
Ground spotter visibility (LOS): 400~500m

 

 

Safety issue

11The only cautionary tips i can give is FPV pilot must aware of "negative pendulum effect" where the axial CG point is mostly above the wings which it is very typical for this war-bird model. It will tends to go upside down if roll countering is not constantly monitored and controlled. Usually happens when pilot lost "horizontal reference view" of the environment horizon especially inside the fog, haze, clouds, cockpit wet condensation or anything that blocked the VFR visual range from inside the cockpit.  AP assisted flight using gyro or any form of stabilization is only temporal counter measure regardless if its at RATE MODE or HEAD LOCK.  Still FPV pilot manual flight skills is highly compulsory especially if intended to fly further beyond visual range.  AOA and Sink Rate must also added to the cautionary list.

Caution also required that this platform best to be flown in open area away from urban population; best flown over huge bodies of ocean, open rivers and big open field and forest cleared from aviation traffic.

If you intend to use HK HEXTRONIK HXT900 9g servo or TOWER PRO equivalent servo on your aileron be sure a small amount of aileron countering control doesn't "peak spiked" the current (A)  from BEC/UBEC into "Brown-out"  because this popular budget servo known to be heavy duty and uses high amount of current to actuate the servo movement especially small increment turn because low winged plane like this P-51D mustang need more active servo movement and current flowing to the servo thus increase core-less brushed motor wear and tear during constant roll countering.  Stock low powered servo once worn out or "Locked" it will likely to soft center back to 0 degree on its aileron, high powered budget servo would likely or 70% possibility locked outside 0 degree angle on the aileron causes the plane to roll which happens a lot on my glider with upgrade powerful budget servo such as HXT/TOWER PRO so be careful on your servo selection.  Unlike the Drifter and Pitts, Mustang have one servo per-aileron which results that the aileron forces only countering the servo horn one way only and there's no natural load countering to oppose the other side.  The analogy is; like you got pull by two girlfriends from both side with same amount of force on the arm but remains stationary position on the ground,.. instead of one girlfriend pull on one side only ended you sway and fall into her side.  So be calculative about the servo load before you going to invest into long range goal.  Any high or spiked current load will trigger to BEC to shutdown into "Brown-out" and put your plane into "Dead stick", always do some calculation and reserve as much current reserved for overall FPV operation on board the Mustang.

 

 

Pros and Cons

Here are list of pros and cons about this platform. Some of this are needed to take seriously if you are going deep into long term FPV ambition

Pros:

  1. Extremely lightweight airframe.
  2. Fast altitude climber and diver.
  3. Excellent power to weight ratio.  1.2kg worth tractor pull/acceleration/thrust power.
  4. Straight line stability undeterred by wind turbulence.
  5. Anti "Spiral of Death", quick stall bail out.  Good flat spin control.
  6. Flexible control, aerobatic and maneuverability.
  7. Excellent undercarriage clearance for L.O.S antenna placement.
  8. Small, portable and easy to dismantle the wings for packaging/travelling portability.
  9. Excellent fast long range platform in comparison to size ratio.
  10. Highly endurance and floatability of P-51D Mustang airframe when compare against other similar airframe design in the market.
  11. Tractor type propeller viewable from behind allow better visual throttle timing adjustment and trimming to synchronize required endurance and reserve power.

Cons:

  1. Pilot will need more VLOS and FPV flight experience  compare to normal FPV flight before flying this airframe. IFR also a huge importance.
  2. Does not glide well nor self leveling the wings and nose angle regardless even if artificially or electronically assisted, will need constant pilot control and flight judgment.
  3. Confusing nose AOA (Angle Of Attack) due to airframe layout.
  4. OSD with AHI indicator and Altimeter are highly recommended.
  5. Un-noticeable "Sink-rate".
  6. Originally a tail heavy frame.
  7. Sensitive aileron control for trade with maneuverability.
  8. Low visibility flight inside the cockpit.  35~50% of useful in flight FPV view, especially during low altitude flight, ground tracking and landing.  Need to see where you going through side windows which is awkward for general FPV pilot.  However this FPV  is fall in the category of "Scale FPV piloting"... fly it like a real plane.
  9. In some situation where visibility is bad IFR flight play a vital role, your pocket burner OSD is going to be your best friend throughout the flight.
  10. Putting a Go-pro is equivalent of putting a concrete brick, Go-pro is a no Go.
  11. Airframe have negative or inverted  "Pendulum CG", you're more likely to roll more during lost orientation or moment of low visibility when there no horizon to indicate your axis leveling.

 p51d 12

 

Current status & flight history

The P-51D Mustang is most challenging FPV platform to fly even in the hands of seasonal FPV pilot.  Most people like me wanted to fly this War-bird it is because i like to appreciate the beauty of scale models and the joy being partial part of real aviation experience.  Flying inside the cockpit simulating the real flying experience with cockpit view, dashboards, wings and moving mechanism replicating like real planes is the reason why  R/C modelers fly them, love  and exhibit them in the hangar and most importantly reasons become an R/C pilot modeler enthusiast.
Its take lots of patient, time, effort and lots of learning curve, building experience and flying skill sets  to perfecting my "scale" flying because the skills set of flying a scale model behinds a cockpit versus a stable glider with full un-obstructed view are completely two different worlds just like riding a bicycle versus driving a truck.  One thing for sure once you get the hang of it and successfully flown hours of flights through various altitude, height, climate, perfect landings and all the rough challenges you're more likely to reach the Pinnacle of FPV flying.  "Scale" FPV flying is the top of R/C FPV food chain.

Lifespan operation: 3 years (updated on 19 June 2015)
Start operation: mid 2012
Maintenance priority check: Motor mounting
Constant critical issue: None
Maintenance cost per-lifespan: $3.00 - aileron servo replacement (updated on 19 June 2015)
Flight hours accumulated per-lifespan: 284 hours (updated on 19 June 2015)
Best L.O.S distance record: 18km (updated on 19 June 2015)
Est. distance covered per-lifespan: 11,930km (Odo) (updated 19 June 2015)
Best height record: -
Best flight time record per-session: 40min (2200mah 3s 35C) (updated on 19 June 2015)
Best low hovering speed record: 15km/h
Best record  for zero thrust landing distance/power failure glide recovery distance: None
Activity status: Still active.

 

 

Latest Log:

(updated: 17/4/2015)

  • Medical check-up and diagnostic flight at medium range completed after 204 hours of total flight hours for almost 3 years of FPV flight operation to check the health condition of the plane. Reveals left aileron servo twitching randomly which sign of worn out.  Immediate replacement has been done with the same servo specification.  Tail landing gear loose but minor effect on ground handling. Transparent canopy fade slightly yellow sign of old material aging.  Video as shown here: FPV P-51D Mustang - 2015 diagnostic & maintenance day.

 

 

Summary

FPV on P-51D Mustang is a huge head turner, not only it an exotic air frame but also attract War-birds enthusiast and make the crowds goes ohhh!! and ahhh!!  Flying a piece of history not only epic but its brought all the glider based FPV competitor down to its knees with its beautiful scale colorfully decorated airframe both range and performance records, you get to have a cool selfie up in the air too.  But the epicness will end if you put a Go-Pro on it because it doesn't tolerate extra weight nor have enough space to put serious HD cams. Even a MOBIUS HD camera could bog its performance down.  Just like the PITTS SPECIAL this P-51D Mustang is extremely small and narrow airframe so setup can be very tricky for intermediate FPV builder.  This platform is best to be flown only by experience FPV pilot and with proper FPV system on board to guarantee flawless and safe flight.  Unlike flying an FPV glider, the performance of scale airframe such as the Mustang is defined by how the pilot handles the plane not by automation system of sophisticated AP system or airframe alone; too high AOA will increase the drag causes power wastage, too slow will have unnoticeable "sink rate" and pilot need high level of alertness & readiness to counter yaw and roll since its a "negative" pendulum CG. Inexperience FPV pilot will likely to have 'upside down' incident after exited out from the fog, clouds or low visibility incident regardless if your OSD have AHI, gyro assisted  or not.   So if you have high intention to fly a low winged scale War-bird make sure you don't skip your homework. Earn some basic flight both VLOS and FPV medals first, experiences and researches before entering Pro zone. The next level is the Pitts Special.

 

 

Videos/Medias
MediasHere are some of my video and gallery related to the above topics:

 


















 

 

Shopping list

Here i've listed some raw material, hardware and stuff where you can start building your own FPV platform.  The list contain the above hardware and also include some compatible ones which you can pickup what suits best for your need and your budget.  So come dig around and start your tech flying ambition:

  1. Platform/Airframe:
  2. Radio set/combo:
  3. Motor/ESC/BEC:
  4. Servo:
  5. Camera/HD/DVR:
  6. Flight controller/AP System/OSD:
  7. Video transmitter/combo:
  8. Battery:

 

 

 

Building threads/Referral

If you don't know where to begin with i recommend you to start reading some guides, wikis and building tips from popular online resources as listed below.  You might find me hanging around some popular R/C and FPV forum below.

 

 p51d 5

 

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