Warbird help

[sklecanda]

Hello, I'm new to the Flite Test forum, but have been flying rc planes for about three-four years. First I would like to thank Josh and Josh with the beginner series. It was very helpful to get me where I am today.

I'm hoping someone could give me some advise on flying one of my warbirds. I have three warbirds, two are UMX planes which I have flown for some years and can do just about any stunt with no issues. I recently purchased a mid-size (650mm) BF 109, which I thought would be fairly easy to fly, since I have flown my UMX warbirds for almost four (4) years. I was quite surprised how difficult it was just to hand launch this new model and get it to fly. Every attempt resulted in left downward roll over and crash. (almost like a bad torque roll and tip stall. I'm using the same transmitter I use for all my other planes, but still had a very difficult time to get this model to fly. In fact, the first nine (9) attempts resulted in immediate crashes. I had performed all my checks several times before each flight attempt, checked CG, battery condition, motor thrust etc... to see if there was anything that I was unaware of that would cause this plane to not fly. I began to think that maybe it is my experience, or lack of, and this was not a plane I should have. I checked several reviews by many who have purchased this same aircraft, to see if others are experiencing the same issues as I.

Many people said this aircraft has a tendency to torque roll on take off, but were still able to compensate and successfully launch. After reading some detailed reviews, I decided to try a launch into a decent headwind, to help with lift and possibly get a successful fight. (up to this point, I was only attempting to fly on completely calm days) At first it appeared to have helped, but I was having difficulty keeping the plane level and after about 40 ft, it rolled over and crashed. It almost appeared like it was under-powered and was not providing enough thrust. I kept thinking that maybe it is me, since other pilots fly the same plane battery/motor setup with no issues.

I decided to remove the factory 2S lipo and go with a three 3S. I even changed the ESC from the stock 10A to a 20A as a precautionary measure to prevent a brownout or ESC damage. I picked up a 3S as close to the size and weight as the factory 2S, so to keep the CG as close to spec as possible. On my first launch with the 3S lipo, it actually flew and I was able to get it trimmed and flying. Although it flew like a rocket and was extremely sensitive. I landed and re-tried the 2S lipo to see if I could fly it since I was able to trim the aircraft and get a feel for its flight characteristics. Re-launched with a high output (turnigy bolt) 2S lipo and she immediately rolled left and crashed.

What am I doing wrong? is this normal or am I just in need of more experience. Why can't I get this model to fly on a 2S battery. All the crashes started to take a toll on the model, so I ordered all new airframe parts. I have since finished assembly of the new replacement airframe and have everything ready to fly. It is like a brand new aircraft. i afraid to try to lauch it in fear of crashing and destroying the new airframe. Any advise would be much appreciated.

Thank You.

Below are the specs on this model.

Length
580mm
Width
650mm
Weight
230g approx. (when using 450mAh Li-Po)
Motor
AF400 BLS B/07/15 Brushless Motor
Battery
7.4V-450-600mAh Li-Po (sold separately) (size: up to 30.5 x 54 x 12mm)
Wing Area
7.2dm2
Wing Load
31.9g/dm2 (when using 450mAh Li-Po)
Wing Type
S3010
R/C System
4-channel, 3-servo 1-ESC
Propeller
D7×P6（3 blade)
Scale
1:15 Scale
Flight Time
5 minutes approx. (when using 450mAh Li-Po)

 

[fixnfly]

What does the trim look like on this aircraft? You need right aileron trim to counteract the torque of the motor. If the aircraft pitches down and rolls left you will need some right aileron and up elevator trim.

If you are used to flying UMX planes with flight stabilization, the controller will have a tendency to automatically adjust the trim. Without a stability controller, it is all up to the pilot to trim and fly the aircraft. Once the aircraft is properly trimmed it should fly pretty much hands off in straight and level flight under calm conditions.

 

[Hai-Lee]

I fly a number of smaller models and the catch is the lack of aerodynamic forces at low speed. If hand launching they require a hefty throw and sadly a throttle setting which is about 75% of max. Whilst they still wobble for a little while when the speed builds they become quite responsive and show none of the low speed issues apparent at launch. Full throttle leads to a snap roll to the left and a rapid landing which is normally on either the nose or wing tip.

The launch with the 3S would have shown some tendency to swing initially but because the extra power gave greater acceleration and a rapid rise in speed the aerodynamic controls became effective a lot sooner. For my most difficult to launch model, (a funfighter spitfire), I eventually built a ground run trolley which has a servo mounted in the trolley for tail wheel steering. When the speed is high enough I just apply up elevator and it lifts out of the trolley, disconnects the steering servo lead and climbs away.

I am sure that there will be a myriad of suggestions as to what you are doing wrong and what you need to do so do not take my comments as a solution to your problem but rather what worked and still works for me.:black_eyed:

 

[sklecanda]

Hello,

Thanks for the reply. Yes, my UMX warbirds do have stabilization. I had thought about getting a stabilization kit for this aircraft, but was hoping to get more flying time first, before adding additional weight.

Initially I started with all control surfaces in absolute neutral position. I was only able to trim the aircraft, when I finally had a successful launch, with the 3 cell battery. I found the trim adjustments to be extremely sensitive, which only required one (1) click of right aileron and one (1) click down elevator to obtain a level and stable flight trim set-up. I flew for about four (4) to five (5) minutes just to get a good feel for the aircraft and even performed a vertical roll and stall test. Prior to using the three (3) cell, I tried launching with aileron compensation, to counter-act the left torque roll, but was unsuccessful.

It just seams like the 2S battery is too close to the low end of the trust scale, for the wing load of this aircraft. Also, prior to trying the three (3S) cell, I checked the motor amp draw and motor thrust, just to rule out any possible ESC or motor issue, with the two (2) cell. No problems found.

I have researched this aircraft and others brands of warbirds around the same size (600-800mm) and have found many pilots having similar torque roll at launch issues. Most say the power from the two (2) cell battery set-up to be flyable, but slightly underpowered.

Thank you for your advise.

 

[makattack]

That seems a little heavy/big for a 2S power system, but I suppose it would still fly ok. I have a few warbirds in the 560mm/100g size that fly on 2S (the discontinued Aircore series) that fly great and have good performance on small 2S batteries (250mAh).

The other 2S powered plane I have is a low wing trainer from Horizon Hobby (also discontinued) called the Archer. It's heavier and larger at 935mm/466g but also flies great with a 2S battery that's also quite beefy (1300mAh).

It's hard to say. I would suggest as others indicated that you try launching at higher throttle, with a much harder throw. Maybe even have someone who knows how to hand launch a plane help you do that.

I know the UMX planes, as light as they are, can be flown practically out of your hands. Not so with larger planes.

 

[sklecanda]

Thank You, I agree. I believe you are spot on about the aerodynamics and tendencies when launching with a 2 cell, and agree about the three (3) cell thrust, causing a much quicker response to level off after launch. Since this aircraft does NOT have gear I have often thought if I could somehow create a launch system, that would allow the aircraft to get sufficient air speed, prior to lift off. Maybe my issue may be resolved. Not sure how to make one though. Thanks for your thoughts and advise.

 

[sklecanda]

Hi,

Thank you for your post. The two UMX warbirds that I fly quite often are the Parkzone P40, (1S battery) which I have installed a higher performance motor that installs in the same factory motor mount, no mods. It increased the airspeed and gave the plane greatly improved performance. Vertical rolls and loops, no problem.
The second (and my favourite) is the e-flite UMX P47. (280mah 2S) All stock, with the exception of adding different decals. That aircraft has unbelievable performace for a UMX! I absolutely love that plane! Makes the P40 seam like a slow flying trainer.

And yes, you are right, they just about will launch right out of your hands. So my thoughts are very much the same as yours, maybe this aircraft is a bit heavy for a 2 cell. But on the other hand, there are others who have flown this model with the factory two (2) cell without crashing.
I have tried different power settings (2/3 to full throttle) when using the two (2) cell, with no success. I wish I had a second person to assist with launching, but for now I will only launch with a head wind to increase lift during launch.

Thanks again.

 

[fixnfly]

I always find it funny how all the flite test guys just give aircraft a light toss to take off. My first airplane we had to either take off from a paved surface, or run and give it a strong throw and it was considered powerful. That said, overpowered aircraft are fun.

It definitely sounds like you are trying to take off with a the aircraft in a stalled condition and the motor isn't able to accelerate it fast enough. That is a pretty small prop to be using with that size airplane unless it is turning relatively fast. The 2S pack would probably work with a larger prop, but then it may pull to much current for that motor. The actual thrust is determined by a combination of prop, motor kv, and battery. You just need to make sure the current isn't so high it overheats the motor, puffs the battery or burns the ESC with any new combination.

 

[makattack]

So the question all this begs is: how are you launching this warbird?

If I were to hand-launch a heavy 2S, low-wing warbird, I would hold the airplane roughly over the CG from the fuselage with my hand sort of making an upside-down/inverted U. I would do this with my left hand, as I fly Mode-2 with the aileron/elevator stick on my right hand. I would have my right hand on the aileron/elevator stick, and use my mouth or chin to throttle up to about 75%, then I would launch with a vigorous/hard swing of my arm from the lowest position to about eyelevel, releasing just before eyelevel, and continue rotating my arm around to clear the tail. I would end up launching it at about a 30-40 degree up angle, but would try to level it out with my fingers on the elevator/aileron stick.

 

[sklecanda]

Hello Hai-Lee,

I did some research into the trolley you suggested and found several pilots who do just that for the same class size warbird's made by other manufactures. Many reviews and articles about why they started to use a trolley launch, are for the same issues when hand launching, that I'm experiencing. I have decided to build one and will give it a try. I can see how it is beneficial, since it increases the take-off speed way above any hand launching. Thank You very much for the suggestion. I will keep you posted.

Thanks again.

 

[fixnfly]

A little cart could help if this is actually the problem. If it does, you can work on your throwing technique also. I have seen jets and other fairly large aircraft hand launched that weren't designed to be. Sometimes you need to run, other times you just need a steep hill to throw it off of. Always throw from the center of mass or slightly in front of it and let the aircraft leave your hand while it is traveling up slightly. We used to sometimes launch a 64" 6 lb bird. It did take two hands and 30' of running, obviously done by an assistant not the pilot.

 

[sklecanda]

Hi Fixnfly,

Yes, I agree, it does appear to stall during launch, due to lack of airspeed. I checked into a larger prop, but as you mentioned the amp draw is too high. I have noticed during my research on this plane and other models by the same manufacture (Kyosho rc or Tex rc) all have a tendency to drop two-three feet and bank left during launch and slowly recovers to flying speed. Also, every video review of this aircraft, has everyone just flying in circles and not performing any aerobatic stunts. It as if they know with the two (2) cell battery, the thrust is insufficient for aerobatics.

The prop and motor are stock (7 x 6 three blade and a 1620kv outrunner)

As for now, I plan on using the three (3) cell. I have changed the stock 10A ESC to a 20A FMS ESC from the FMS 800mm BNF 109. I may try the two (2) cell again, after I complete the trolley launch, since the trolley will allow increased air speed for better take-off.

Thanks again

 

[fixnfly]

More power is always nice, but I just had an idea... If the airplane is stalling on launch, try throwing the aircraft at a lower angle with a little less up trim. Depending on how tall you are you have at least 4-5 ft to descend and let the motor pick up speed before you must point it up. Also anything you can do with the prop that will increase thrust should help. That usually means larger blades with less pitch, or just more blades.

 

[sklecanda]

Hello Makattack,

I launch holding the aircraft on the bottom of the fuselage, at the trailing edge of the main wing. Holding the plane with a very slight nose up angle (barely noticeable), slightly above my head. (I'm 6'1") This is the same method I use for my two other (UMX) warbirds. I only have one plane I launch with gear, a 48" high wing trainer, that I have flown for several years and have increased the thrust enough to perform loops. I have never hand launched the trainer.

 

[fixnfly]

The CG of the aircraft is hear the leading edge of the wing. When you throw from behind the CG it is easy to impart a pitching motion that either causes the aircraft to pitch up or down as it leaves your hand.

 

[sklecanda]

One other note:

One of my launch attempts with the two (2) cell, was with a 2-4 mph headwind. Although the launch was unsuccessful with a crash, the overall launch was greatly improved, over a launch in calm conditions. I felt this was more evidence of a lack of prop thrust and the headwind just increased the lift.

I have also read several reviews on the FMS 800mm BF109 warbird. That plane is almost double the weight of mine, yet only four (4) inch larger wingspan. FMS also uses a two (2) cell battery and a 1700kv outrunner, with the exact same size prop my plane uses. Almost every review recommends a three (3) cell to get that plane to fly correctly, especially for hand launching.

 

[sklecanda]

Hi Fixnfly,

Yes, I have watched both the video's you posted. That was initially my thought, was my launching technique was not good at all. I thought the second video (Horizon Hobby) was very interesting. All the aircraft seamed to launch without dropping at all, as if they had a substantial amount of prop thrust. That is completely the opposite of my model. I had thought about trying to launch from the top of the fuselage, with the plane along my side as Makattack suggested, but I believe that it may be impossible. The best place to hold it is at the canopy, which is only held in by magnets. Any other position just seams too awkward and risky of causing a crash.

 

[Hai-Lee]

Hello Hai-Lee,

I did some research into the trolley you suggested and found several pilots who do just that for the same class size warbird's made by other manufactures. Many reviews and articles about why they started to use a trolley launch, are for the same issues when hand launching, that I'm experiencing. I have decided to build one and will give it a try. I can see how it is beneficial, since it increases the take-off speed way above any hand launching. Thank You very much for the suggestion. I will keep you posted.

Thanks again.

Just a little note of info! To connect to your trolley steering mechanism you will need to connect to your Rx's rudder output. You will need a "Y" harness if you have a rudder servo or a servo extender lead if there is no rudder servo.

On my spitfire I ran a servo extender lead from the Rx through a small hole to the bottom of the fuselage where It was fixed with hot melt. The servo lead for the trolley steering had its connector sides sanded down so that it was very easy to disconnect it with a gentle tug on the lead,

The servo is plugged in when the plane is placed in the trolley, (the servo wire is cable tied to the trolley with a little slack). Upon lifting off the plane climbs away and the servo lead, (which is permanently connected to the trolley), is pulled and easily disconnects leaving the plane to fly and the trolley to roll to a stop. :black_eyed:

 

[sklecanda]

Hello Hai-Lee,

It has been quite some time since I last posted anything about the hand launching issue with my 750mm BF-109 Warbird. Since my last post, I have built a launch dolly for this plane and have done some initial testing. ( I have yet to attempt a launch) I found that the only way I can use the dolly, is on asphalt. I tried a few different wheel configurations, in attempt to find a way that would work on grass, with no success. I believe the thrust of this aircraft, even with the three (3) cell battery, is insufficient for grass launching on a dolly since it does not have enough pull to obtain a good enough take-off speed. In most test, the dolly would stop moving or just move too slow thru the grass. I tried a variety of different diameters, thickness’s and weights of wheels, with very little improvement. Another issue I found is if the ground isn’t smooth enough, the dolly bounces too much when moving thru grass, causing the aircraft to begin to bounce too much. If the grass is like a golf course green, then I believe it would work just fine. On asphalt, the dolly with the plane picks up speed very quickly. I did a lot of research and almost everyone who has used a dolly, has modified the plane with a bigger motor, prop and/or battery to increase thrust or launches from asphalt.

Unfortunately, I cannot change anything to increase the thrust. If I go to a bigger and more powerful motor, then the battery size would have to increase which cannot be done due to the airframe design. Also, I cannot locate a better propeller, that would increase thrust and still stay within the motor amp draw range. In other words, the configuration I have is as good as it gets.
My research has also found, if you go with smaller planes, the two (2) cell set-up is just fine. Good power to weight ratio. If you go to a bigger size aircraft, then the availability of powerful motors and batteries for larger aircraft are very good to give you that great power to weight ratio. Plus larger wings with more lift.

I have not flown this plane at all this year, but hope to so soon. I'm currently looking for a place to launch from asphalt, then fly over grass and belly land on grass. Also, I have done some power and battery testing, which if all my calculations are correct, I will only have about 3-3 1/2 minutes of flight time. (not very good) I have decided never to pursue this size aircraft in the future, unless technology greatly improves performance and flight time. As for now, I will continue my search for a good asphalt launch site and hope to get some nice (but quick) flights.

On another note, I have purchased a Flyzone Aircore micro BF 109 airframe, and installed the entire electronics package from my first eflite UMX P47 thunderbolt plane. ( no worries, I have a second one that I fly all the time) Everything is complete and I'm just waiting for the weather to clear, so I may do some initial testing and maiden flight.

Thanks again for your post and advice.

 

[sklecanda]

Hello Everyone,
I thought I would send an update since it has been three years since my last. Shortly after my last post on this model, I was injured and have spent the last 2 1/2 years going thru multiple surgeries, procedures and a ton of rehab. During that time, I was able to do some additional testing and with the help from other members, I was able to get a recommended hand launch technique that enabled me to fly this model without crashing at take-off, Finally!
I have since then flown this model several times with great success! The performance is outstanding with upgrading to a 3s 500 mah Zippy battery, 20 amp ESC and an 8 x 6 3 blade propeller from FMS. The brushless motor is stock. The power to weight ratio is exactly where it should be for a warbird. Once I was able to perfect my hand launching, I was able to perform great aerobatics and still get great flight time, 5-6 minutes! That is much better than expected. This model is very fast and extremely agile, which from what I have read is exactly how the real BF-109E was in WWII.
Stall speed is where you expect it to be and with the motor/propeller torque it is a very quick tip stall, if you try to fly too slow. One thing is you must launch in low rates, as the model is very sensitive and almost impossible to control correctly in high rates during launch. One the aircraft has leveled out and flying well, then I place it in high rates for great flying fun.

As for the flyzone aircore 109, that did not work at all and became a destroyed model and scraped. (minus the electronics)

Thanks to everyone and their suggestions,
Happy Flying!