Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[Evan D]

I disagree... to a point...

OT discussions are what PM's are for.

That, and "The Lounge".

[themudduck]

Hey I got a little story. I wonder what GliderGuy will think since he flies so much. I made a stupid mistake, and I hope this won't happen to anyone else. I don't know how I did it, but it wasn't really that hard to do.

So I had the MIG at the field today and only got two flights in, because I was helping many other guys with their planes. Beautiful spring day in the mid 50's and very light wind.

During my second flight later in the afternoon I noticed a slightly strange noise like an odd whistle kind of noise coming from the ducts. But everything seemed ok so I kept going... but I was paying close attention. It noticed that it seemed to make the noise when I was going fast.

Towards the end of the flight it seemed kind of sluggish and when I came around a turn it seemed to be yawing... and slowing down... something was wrong.
So I gave it more power and came in to land. Normal procedure - slowing down, flaps down on the final base turn, come down the chute....and then I managed a fairly decent landing on the side of the runway in the grass (by then I was aware something was wrong but didn't know what... and was quite relieved to get it down in one piece.

So I brought the model back to the pits and started looking at it, ran the fans up just to activate both motors to see if something was in the ducts. Everything was working... I noticed a blade of grass in one fan..... but then I noticed that the other fan stopped turning!
So I cut the throttle and tried again. Both fans started, then one stopped after a few seconds. So only one EDF was working!

The sound was because one EDF was windmilling during the flight, I was flying on only one motor! I was amazed because the model actually flew pretty well!
I mean, thinking back, its pretty amazing that it handled so well with only one fan working. Well enough that I couldn't really tell what was going on. The yaw in the final turn gave it away.

So I am scratching my head and I assumed that maybe one of the ESCs had gone bad.
Next step was to take the batteries out and I tested them.
First battery was at around 27% remaining.
The other battery was at 1%. OMG.

I use RoaringTops 6250s and the battery wasn't puffed or hot. Just dead as a brick. The cells were down to about 3.1 volts!!

So what happened was that after the first flight the used batteries were sitting on the table. Later on when I loaded up the batteries for the second flight somehow I accidentally picked up one of the used batteries that were still sitting there from the first flight.
Off I went... I had power for about a minute and then it went dead.

Now it was only complete dumb luck that the dead battery was NOT the one plugged into the BEC powering the receiver! The good battery had that duty and the dead one was only plugged into the other motor.
I think if it were the other way around, the plane would have gone stone dead halfway into the flight (the BEC would have cut the power to the motor first, but who knows) and then I would have a tale of the plane not responding to the elevator, who knows.
As it was, I was able to pull this beast around the air with only one fan working.

The dead battery is on the charger now (carefully at 1 amp) and it seems to be charging back up.

Hope no one else ever has this happen! Flying this big plane on one fan is not recommended, 2 stars would not do again!
A friend gave me a good suggestion, I am going to use a sharpie and number my 6S batteries so I'll use #1 and #2 first, then 3 and 4, etc. That way I'll be able to avoid this aain!

[Hugh Wiedman]

Hey I got a little story. I made a stupid mistake, and I hope this won't happen to anyone else. I don't know how I did it, but it wasn't really that hard to do.


Hope no one else ever has this happen! Flying this big plane on one fan is not recommended, 2 stars would not do again!
A friend gave me a good suggestion, I am going to use a sharpie and number my 6S batteries so I'll use #1 and #2 first, then 3 and 4, etc. That way I'll be able to avoid this aain!

Yes, an incredibly stupid mistake, how can anyone be so dumb, Oh, and it's something which I have also done, so I'm in your club, RC Flying for Dummies!! Happened several years ago when I put a just used battery back in my 60" Beast Bi-Plane (must have gotten distracted by all the BS I was spouting with the other guys-so it's their fault). I was in the middle of a knife edge maneuver without a lot of altitude, but luckily, that aircraft has enough glide ratio that I got it down with only minor damage to the landing gear, but it was dead stick with just enough power to slightly move the servos. Thought the same, ESC gone bad, motor gone bad, nope, stupid maintenance crew installed a used battery (Oh, that's me too). Since then, I got some small green circle stickers from Office Depot and put them on a fully charged battery, then when removing the battery, I take the sticker off. I also number each of my batteries (with a label maker), but more so to keep track of the flights on each and to go into a rotation since I have a number of batteries, including 16 RT 6250's and want to use them equally (sounds like a lot, but they go in several EDF's and sometimes I'm taking all to the field-the A-10 eats 8-10 itself in one day). Since then, I religiously check my batteries as I'm installing them at the field, even with the green stickers!

[xviper]

The cells were down to about 3.1 volts!!

Now it was only complete dumb luck that the dead battery was NOT the one plugged into the BEC powering the receiver! The good battery had that duty and the dead one was only plugged into the other motor.
I think if it were the other way around, the plane would have gone stone dead halfway into the flight (the BEC would have cut the power to the motor first, but who knows) and then I would have a tale of the plane not responding to the elevator, who knows.

I may be mistaken in this idea but ........................... Although the ESC may have hit the LVC, the battery would have still had about 18V, which is plenty to power the BEC and provide the necessary voltage to the RX to keep all the servos going. On single battery, single motored planes, I've hit the LVC, the motor quit but I still had the ability to do a "dead stick" landing. Whatever voltage is going INTO the BEC gets scaled down to output ~6V. Whether battery was putting out a full 25.2V or a mere 18V, it would still output 6V.

[crxmanpat]

Glad you got it back OK, and good to hear it will fly on one fan. And yes, I've done it too (in my Mig-21). Now I have 3D printed caps that fit on the EC5 connector. I have 3 colors; green, yellow and red. Green is for charged, Yellow is for storage charged, and Red is for discharged. As soon as I take batts out of my plane, I put the red cap on them to ensure I don't accidently pick them up and put them back in thinking they are charged.

[kallend]

Now I have 3D printed caps that fit on the EC5 connector. I have 3 colors; green, yellow and red. Green is for charged, Yellow is for storage charged, and Red is for discharged. As soon as I take batts out of my plane, I put the red cap on them to ensure I don't accidently pick them up and put them back in thinking they are charged.

Great idea!

[Airguardian]

I use numbered batteries (mostly to keep track of their number of cycles and know if one is bad, which one it is, etc), and even then you can make that mistake. It's not that I have yet... but I've found myself pretty close to doing it a few times.
And may have taken off with a used batt on a single-batt plane too, lol...

Point is, the mistake is almost always made when you are talking with others at the same time you are prepping the flight.
Not to say you gotta be rude and send your buddies away when preparing for a flight (or maybe yes) but to be self-conscious that it is a huge distracting factor and to remember to triple-check things in that kind of scenarios. Also one thing I often do is to touch batteries before closing the canopy. If one is warm, I know I messed up, wouldn't be the first time :)

As for the MiG flying acceptably well on just one fan, that's great to know, and bet it's mostly due to the fact that the nozzles are canted outwards (This reduces their yawing moment around CG).

BTW, already repaired the 'loose leg' and flew 3 more flights with the MiG today with some air to air footage.
I couldn't take it away from the fuselage without making a huge mess so I ended up gluing it in place and adding a balsa wood square strip to distribute the loads and block the thing in place. Ended up using epoxy... may regret later but so far so good. :)

[DCORSAIR]

Hey I got a little story. I wonder what GliderGuy will think since he flies so much. I made a stupid mistake, and I hope this won't happen to anyone else. I don't know how I did it, but it wasn't really that hard to do.

So I had the MIG at the field today and only got two flights in, because I was helping many other guys with their planes. Beautiful spring day in the mid 50's and very light wind.

During my second flight later in the afternoon I noticed a slightly strange noise like an odd whistle kind of noise coming from the ducts. But everything seemed ok so I kept going... but I was paying close attention. It noticed that it seemed to make the noise when I was going fast.

Towards the end of the flight it seemed kind of sluggish and when I came around a turn it seemed to be yawing... and slowing down... something was wrong.
So I gave it more power and came in to land. Normal procedure - slowing down, flaps down on the final base turn, come down the chute....and then I managed a fairly decent landing on the side of the runway in the grass (by then I was aware something was wrong but didn't know what... and was quite relieved to get it down in one piece.

So I brought the model back to the pits and started looking at it, ran the fans up just to activate both motors to see if something was in the ducts. Everything was working... I noticed a blade of grass in one fan..... but then I noticed that the other fan stopped turning!
So I cut the throttle and tried again. Both fans started, then one stopped after a few seconds. So only one EDF was working!

The sound was because one EDF was windmilling during the flight, I was flying on only one motor! I was amazed because the model actually flew pretty well!
I mean, thinking back, its pretty amazing that it handled so well with only one fan working. Well enough that I couldn't really tell what was going on. The yaw in the final turn gave it away.

So I am scratching my head and I assumed that maybe one of the ESCs had gone bad.
Next step was to take the batteries out and I tested them.
First battery was at around 27% remaining.
The other battery was at 1%. OMG.

I use RoaringTops 6250s and the battery wasn't puffed or hot. Just dead as a brick. The cells were down to about 3.1 volts!!

So what happened was that after the first flight the used batteries were sitting on the table. Later on when I loaded up the batteries for the second flight somehow I accidentally picked up one of the used batteries that were still sitting there from the first flight.
Off I went... I had power for about a minute and then it went dead.

Now it was only complete dumb luck that the dead battery was NOT the one plugged into the BEC powering the receiver! The good battery had that duty and the dead one was only plugged into the other motor.
I think if it were the other way around, the plane would have gone stone dead halfway into the flight (the BEC would have cut the power to the motor first, but who knows) and then I would have a tale of the plane not responding to the elevator, who knows.
As it was, I was able to pull this beast around the air with only one fan working.

The dead battery is on the charger now (carefully at 1 amp) and it seems to be charging back up.

Hope no one else ever has this happen! Flying this big plane on one fan is not recommended, 2 stars would not do again!
A friend gave me a good suggestion, I am going to use a sharpie and number my 6S batteries so I'll use #1 and #2 first, then 3 and 4, etc. That way I'll be able to avoid this aain!

It happens to all of us, stickers are a good idea, but one way is the best that it don't happen again, lay them in the jet or plane and check them with your battery checker before or after you strap them in.......

[GliderGuy]

TMD - Glad she got down safely!

Lots of good ideas presented here. Numbered batteries are good, stickers help....but I do one more thing for added assurance.....used batteries ALWAYS go in one location (my truck’s floor) and full batteries ALWAYS go somewhere other than the floor...,Ex: the dash or the center console, the seats, etc. Used batteries ALWAYS are put in one location ONLY. LOL and if I get to visiting, I do not hesitate to put the battery checker to good use.

When I am in the cockpit, and a distraction happens, RED FLAGS of mental alertness start waving. Checklists are re-done, etc.

-GG

And....yes, I have done this same mistake, too. P-38 and she survived.

[GliderGuy]

BTW, already repaired the 'loose leg' and flew 3 more flights with the MiG today with some air to air footage.
I couldn't take it away from the fuselage without making a huge mess so I ended up gluing it in place and adding a balsa wood square strip to distribute the loads and block the thing in place. Ended up using epoxy... may regret later but so far so good. :)

Yep.... That’s what I determined, too. Gonna be tough to remove the plastic main gear blocks w/o making a mess of that area. Best to repair and brace in place as we have both done.

Hint: For all.... I got a scratch in my MiG’s canopy. I was able to take it out with a Mr Clean Magic Eraser....which is a VERY fine abrasive. Took a lot of effort and time (always work in circles), but the scratch came out, and no haze was added to the canopy. A final application of a good polish, and it looks like new.

-GG

[themudduck]

Thanks guys, appreciate the comments.

XViper is certainly right, the BEC would have kept working since that big battery pack has far more that 6 volts even when its fully discharged. So in either harness position (BEC or non-BEC side) the same result would have happened (one motor stopped working).

I do check the batteries right before I install them. Usually one battery is slightly higher than the other one and that one goes to the BEC side of the harness.
Anyway I did check the new batteries (the second set) before the flight, but both sets of batteries were sitting on the table and somehow I grabbed one of the used ones when I was sticking them in.

Like DCorsair said, doing a final voltage check after the newly installed batteries are sitting in the plane, right before going up, will be a great habit to get into.

And GG I'll make sure that the used ones never are placed near the good ones next time! There's no way to tell how "full" they are by looking at them, of course! Wouldn't it be nice if you could!

[Airguardian]

but I do one more thing for added assurance.....used batteries ALWAYS go in one location (my truck’s floor) and full batteries ALWAYS go somewhere other than the floor.

Yep... do that too.
Bring them in a sort of briefcase and all spent ones I leave in the outside so they cool down and far away from the rest in case one decided to go poof!

[Hugh Wiedman]

Yep... do that too.
Bring them in a sort of briefcase and all spent ones I leave in the outside so they cool down and far away from the rest in case one decided to go poof!

I always check my batteries as I pull them out after a flight to make sure each cell is somewhat consistent with no potentially "bad cell" in the making and verify that I haven't drained them below my preferred level of 25% and then put the used batteries in an ammo box labeled "Discharged" as I take them out of the plane. This keeps them separate from charged ones and can go directly to the storage charger when I get home.

[fredmdbud]

Hope no one else ever has this happen!

I make it a point to segregate used batteries from unused. Habit learned early. :)

And since I have my batteries running parallel to share the current load, I also test with a cell checker before plugging them in.

[kallend]

It happens to all of us, stickers are a good idea, but one way is the best that it don't happen again, lay them in the jet or plane and check them with your battery checker before or after you strap them in.......

I have pack voltage telemetry in all my EDFs, and it gives me a voice call out as soon as I disengage throttle cut. I know immediately if there's a problem.

[wvrcdude]

I use these. They are very inexpensive and work like a champ!

[GliderGuy]

Pretty slick! Tiny, too. 2cmx1cmx0.2cm

Link follows....ordered some!

https://www.amazon.com/dp/B06Y6JM98R...V0PQ7GJVGJAB39

-GG

[Airguardian]

Cool flight scenes, enjoy!

[wvrcdude]

Pretty slick! Tiny, too. 2cmx1cmx0.2cm

Link follows....ordered some!

https://www.amazon.com/dp/B06Y6JM98R...V0PQ7GJVGJAB39

-GG

That's where I usually get them. If I'm ordering from Bang Good I'll order some as they are a bit cheaper there.

[Sky Wolf]

Cool flight scenes, enjoy!

Love the SLO-Mo AirGuardian! You’ve gotten very comfortable with this jet...nice going!