Freewing 80mm F-5E Tiger II

[MKreun]

well understood, now would be interesting to compare both your and your friend's models side by side to check whether there were indeed some physical distortions regarding wing/elevator positions that might have caused a systematic asymmetric wing lift or roll force to the right. But I guess post-crash rather difficult to proceed?... BTW, out of curiosity, were you flying with a 5000 mAh (rather heavy) or lighter battery?

If I were you, I'd give it another try with a new F5 kit and 4000 battery - instead of an outside dinner with family 😁😁...

The day we did the first maiden, they were literally sitting side by side. Nothing was obvious. First flight was on an Admiral 4000 I borrowed. Second was on a 6000.

Gooniac,

nothing harder than flying a plane that is out of trim.

I agree. I didn't even get the chance to trim. The whole second flight was 3-5 seconds. In addition I was using full aileron to even slow the roll.

I have noticed the nose gear door causing all kinds of issues

I read this in one of your previous posts. I've experienced this in a DA-42 flying full scale. I was able to suck up the gear on the second flight and it didn't seem to change the flight characteristics. If I repair it, I'll fly without.

Another thing to note is that this plane is very touchy with elevator throw. it is really easy to get it in to an accelerated stall without even really knowing what you have done!

I had also previously read your notes regarding this. Second flight I did on low rates specifically to address this. My initial rotation was slow, smooth pitch up. 5-10 deg. I induced a stall in my maneuvering to avoid injury but the initial roll was not caused by a stall. I've been a pilot for 22 years, professionally for 13, I currently fly jets. I've flown aerobatics, practice accelerated stalls, I used to teach accelerated stalls. Not to say all of that translates to RC skill sets, but I've also flown many hours on the sims, specifically with training in mind, and also fly quad copters. I was doing aerobatics on my FW L-39 on the second flight flying RC jets. (I've since crashed goofing around and oh well, part of the hobby.) I openly seek critique and constructive criticism. If it was me causing an accelerated stall on rotation I would happily own that. I just want to have a better understanding of what happened. If I fix this up I wouldn't want to even attempt to fly it again b/c I still don't have a clue what happened. I would expect the same thing to occur at this point.

Thanks for all of your contribution to this thread. It's been very helpful to watch your videos.

[gooniac33]

I was posting another reply at the same time you posted your question that answers this. To paraphrase. It didn't pop on it's own and I didn't have to yank it off. Rotation was smooth. The roll didn't present itself until the wing began to produce lift. I should have added for clarity, both flights were towards the front of the CG envelope but on the first flight the battery shifted as I had to climb rapidly to avoid injuries and CG moved well aft of the limit with ironically is what allowed it to flat spin down to safety. To answer another way. The wing wasn't stalled, speed was high, AOA was low until I had to climb over the pits/people/cars. That exacerbated the problem but was not the cause. In the post crash discussion, no one felt that was an issue. My buddy who built his along with mine didn't even suggest it. He has no problem sharing his opinion or protecting my feelings. I'm assuming it was my rigging but we built them side by side. One flew, one was uncontrollable.

nothing harder than flying a plane that is out of trim... That's what it sounds like to me. And also keep in mind that I have noticed the nose gear door causing all kinds of issues on mine after not having one in place for a while. It causes the plane to yaw right, pitch down and roll right as well. I set up flight modes to combat it but eventually just stopped using the nose gear door. Another thing to note is that this plane is very touchy with elevator throw. it is really easy to get it in to an accelerated stall without even really knowing what you have done! It will just kinda go limp and not respond to controls but the speed will make you think that something else is wrong when its really just a stall. Even with the high performance inrunners you need to let the plane pick up some speed and not use too much elevator on take off or risk getting into trouble. That is my take and hopefully it helps some.

[JP-4203]

well understood, now would be interesting to compare both your and your friend's models side by side to check whether there were indeed some physical distortions regarding wing/elevator positions that might have caused a systematic asymmetric wing lift or roll force to the right. But I guess post-crash rather difficult to proceed?... BTW, out of curiosity, were you flying with a 5000 mAh (rather heavy) or lighter battery?

If I were you, I'd give it another try with a new F5 kit and 4000 battery - instead of an outside dinner with family 😁😁...

[MKreun]

How fast were you going before rotation?.

I was posting another reply at the same time you posted your question that answers this. To paraphrase. It didn't pop on it's own and I didn't have to yank it off. Rotation was smooth. The roll didn't present itself until the wing began to produce lift. I should have added for clarity, both flights were towards the front of the CG envelope but on the first flight the battery shifted as I had to climb rapidly to avoid injuries and CG moved well aft of the limit with ironically is what allowed it to flat spin down to safety. To answer another way. The wing wasn't stalled, speed was high, AOA was low until I had to climb over the pits/people/cars. That exacerbated the problem but was not the cause. In the post crash discussion, no one felt that was an issue. My buddy who built his along with mine didn't even suggest it. He has no problem sharing his opinion or protecting my feelings. I'm assuming it was my rigging but we built them side by side. One flew, one was uncontrollable.

[MKreun]

but could easily control and stabilize while simultaneously reducing its climb rate. Unfortunately, I still operate it with the weaker outrunner motor. For my subsequent flights, I allowed it for more ground speed prior to rotation and this clearly helped to get it better under control after take-off (always used half flaps and felt comfortable with it, still some right roll tendency but controlled through trim).

This wasn't subtle at all. It wasn't as if though it was trying to roll on the ground as if I was going too fast with ailerons. It tracked well on the ground as soon as I rotated and the wing really began producing lift there was a huge asymmetry. I'm familiar with high wing loading aircraft. I was using the T/O flaps setting and CG was towards the front of the envelope. I didn't feel as thought it were trying to bounce off or conversely I didn't feel like I was yanking the nose off. During my initial rotation I only pulled my nose 5-10 deg up but it rolled so fast and headed towards the pits I had to pitch up harder to avoid injury.

Thanks for your reply.

[Mizer67]

Thanks. We took our time and did a ton of double and triple checking. I tested the servos for a few min w/ a servo tester. There was clearly asymmetric lift. I know it's more likely that it was installation/assembly error on my part but with the number of checks we did I wonder if the wing didn't have a degree or two of mismatched AOA between the wings or the vertical stab not perfectly centered. I'm mostly frustrated that I don't have a clue where to start if I were to spend the money to repair. The two flights were nearly identical if the battery shift is left out from the first. Immediately after rotation on both flights it rolled hard right and ended up facing 180deg downwind within about 3-5 seconds after of rotation. I had high rates for the first flight which allowed me to fight a bit longer. The second was low rates. Both rotations were smooth until I had to take evasive action and climb more aggressively. As I slowed on the second the ailerons became less effective and I couldn't stop the roll any longer. I left my thumbs on my transmitter after impact and showed my buddy I had full left aileron and rudder. Still rolled right and impacted right wing/nose low. My assumption is even if I did fix it, I wouldn't know what to change to correct the roll issue because I have no idea of the cause.

How fast were you going before rotation?

The F-5 needs more speed to fly than most, even flown light. It's one jet that early after re-entry into the hobby after a 20-year hiatus that I crashed also. This was about the 2016 timeframe in my case. My experience sounds similar, but I was able to get it up and trimmed, but stalled on base to final with full flaps trying to get it slowed down to land on our short field. It will stall on you fairly easily.

[JP-4203]

I noticed similar right roll behavior with my F5 right after take-off, thought it was 1) some gust or thermal wind influence or 2) wrongly trimmed ailerons but could easily control and stabilize while simultaneously reducing its climb rate. Unfortunately, I still operate it with the weaker outrunner motor. For my subsequent flights, I allowed it for more ground speed prior to rotation and this clearly helped to get it better under control after take-off (always used half flaps and felt comfortable with it, still some right roll tendency but controlled through trim). Second optimization was Gooniac33's advise to reduce weight by changing from a 5000mAh to a 4500mAh lipo which further helped, well accepting a flight time reduction of some 30 secs. Still, the F5 remains a lively beast in my view which needs to be disciplined by its pilot, personally I feel much more relaxed when flying e.g. Freewing FA18 90mm...

[MKreun]

MKreun Sorry for the loss.

Thanks. We took our time and did a ton of double and triple checking. I tested the servos for a few min w/ a servo tester. There was clearly asymmetric lift. I know it's more likely that it was installation/assembly error on my part but with the number of checks we did I wonder if the wing didn't have a degree or two of mismatched AOA between the wings or the vertical stab not perfectly centered. I'm mostly frustrated that I don't have a clue where to start if I were to spend the money to repair. The two flights were nearly identical if the battery shift is left out from the first. Immediately after rotation on both flights it rolled hard right and ended up facing 180deg downwind within about 3-5 seconds after of rotation. I had high rates for the first flight which allowed me to fight a bit longer. The second was low rates. Both rotations were smooth until I had to take evasive action and climb more aggressively. As I slowed on the second the ailerons became less effective and I couldn't stop the roll any longer. I left my thumbs on my transmitter after impact and showed my buddy I had full left aileron and rudder. Still rolled right and impacted right wing/nose low. My assumption is even if I did fix it, I wouldn't know what to change to correct the roll issue because I have no idea of the cause.

[SanExup]

MKreun Sorry for the loss. It's probably too late to check for squareness and alignment on the stabilizers, or a stripped servo that actuates but not consistently, doesn't recenter? but it sounds like you have looked over everything. I don't know how bad it is, but I do have a plane that saw a few cartwheels, torn wing, broken fuse. I left it alone for months and then glued it back together. I fly it still, in all it's ugliness. It's my warmup plane, because it can't look any worse.

[MKreun]

What receiver are you using? Gyro?

AR620, DX8e, no gyro. Control surfaces were all moving properly and set to factory rates/throws. It responded to control inputs, and responded properly, but they were not enough to overcome the roll. It felt like asymmetric flap deployment but I checked prior to the flight.

[SanExup]

What receiver are you using? Gyro?

[MKreun]

I've got a question for the F5 brain trust. Unfortunately I crashed again on my second maiden. The aircraft was completely uncontrollable. I'm wondering if anyone has had similar experience.

To start the story off, I'm recently getting back into RC after about 20 years out. My buddy and I both purchased the Swiss F5 with the HP inrunners in hopes to have some formation fun. Purchased them the same day, built them together, and set them up identically. Aileron, flap, elevator, all triple checked. He maidened his with little trouble. As I began my maiden, it pulled hard right and veered towards our pits. I pulled up hard to avoid damage and the battery shifted aft. As I fought for control I ended up in a flat spin and helicoptered my way down to soft landing in deep grass. I had to use full left aileron on full rates to over come the roll. After fixing some damage to the gear and verifying all my control throws I had the guys at the field look things over. Everything seemed in order. I attempted the second maiden and again immediately after rotation the aircraft veered towards the pits with full left aileron unable to overcome the roll this time I rolled inverted and crashed.

The forward nose and gear is destroyed and the right wing was ripped from the fuselage. It would be fixable. Considering the prior performance I don't know that I have the desire to bother. If it was uncontrollable before then how would it perform being cobbled back together. In my mind this was an aerodynamic issue, not mechanical. That said, I have zero idea what would have caused this. I'm ready to strip the airframe and dump it in the trash. I've got an L39 that performs like a dream.

[JP-4203]

thx much appreciated, 4500 in my mind,... and maybe later also an afterburner 😉

[gooniac33]

Thx Gooniac, will maybe try with less heavy lipo, I m sure that would offer more jet feeling pleasure... though I could always take-off with a 5000 but feeling like a lawn mower and felt ashamed about climbing rate...

will keep your afterburners in mind, saw videos on em, was quite impressed!

The 30c 4500s are a good choice as well and mine flew great with those on the stock set up. It was fast and climbed just fine without being overly heavy and still allowing good flight times! Just make sure that the CG is not nose heavy! That kills climbing performance after take off. A shallow climb initially until you build up some speed is always good with the stock. When you upgrade to the inrunners you can go vertical straight from take off!! Contact me direct when ready for a burner!

[5280 RC]

Did you already fly it with the afterburner? Wonder whether the extra weight has any impact on flight characteristics; with the standard outrunner EDF mine is already at take-off limit with a 5000mAh lipo...

This particular F5 has been upgraded with an inrunner motor 3658-1920kV. It rips. Inrunner setup stays out of the airflow of the motor. Check out the video on fiftytwoeightyrc.com. Thanks.

[JP-4203]

Thx Gooniac, will maybe try with less heavy lipo, I m sure that would offer more jet feeling pleasure... though I could always take-off with a 5000 but feeling like a lawn mower and felt ashamed about climbing rate...

will keep your afterburners in mind, saw videos on em, was quite impressed!

[gooniac33]

Did you already fly it with the afterburner? Wonder whether the extra weight has any impact on flight characteristics; with the standard outrunner EDF mine is already at take-off limit with a 5000mAh lipo...

the outrunner is a little hard to get off the ground with anything over 4500mah. My battery of choice to keep weight down was a 30c 4000 and it worked really well! Be sure to get the CG right with the heavy pack or you will struggle to get off the ground too. If you use an aerodynamic burner it won't hurt your take off performance at all. With the one that I make for the outrunners its actually better than the stock set up with more airflow going around the motor but an aerodynamic shape that cleans up the airflow after the fan.. Some people have noticed an increase in performance when adding mine and its the brightest most realistic out there as of now too! Although the full scale F-5 has a really dim burner in real life that is also more blue in color...

[JP-4203]

Finished up this afterburner for the F5. Looks killer as it flickers. $45.

fiftytwoeightyrc.com - lots of info on the site.

Did you already fly it with the afterburner? Wonder whether the extra weight has any impact on flight characteristics; with the standard outrunner EDF mine is already at take-off limit with a 5000mAh lipo...

[5280 RC]

Finished up this afterburner for the F5. Looks killer as it flickers. $45.

fiftytwoeightyrc.com - lots of info on the site.

[JP-4203]

Here you go with the two emblems 😉😉, both worn on the Hawker Hunter sqdn. 7 and sqdn 4.... since 1993 no longer in service...