Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[xviper]

Someone at my club flew his MiG at full throttle while forgetting to "normalizing flaps" (his words) without realizing it. No crash. He was taking video with onboard cameras. Put his MiG through all sorts of maneuvers.

He was using D85MG servos for his tails. Basically the same setup used by "Just Plane Crazy" on YouTube.

Those servos are spec'd out at almost the same torque as the upgraded Freewing ones. Could it be that the HiTec servos meet their specs while the Freewing ones do not?

[xviper]

I am thinking its time to buy one of those how to improve your memory books as that will work for whichever plane you fly

Indeed! I posed a question on the F-14 thread about forgetting to pull up the flaps when sweeping the wings back and how to program it to automatically do it. The answer I got was, "Sometimes, we just have to accept the consequences for our actions and our inability to remember important stuff." (I'm paraphrasing a bit here.) I think something like this applies here.

[GliderGuy]

Indeed! I posed a question on the F-14 thread about forgetting to pull up the flaps when sweeping the wings back and how to program it to automatically do it. The answer I got was, "Sometimes, we just have to accept the consequences for our actions and our inability to remember important stuff." (I'm paraphrasing a bit here.) I think something like this applies here.

I’ve mentioned this before, but it is worth repeating....

My father (WWII flight instructor) told me on more than one occasion when he was teaching me....

“You either think when flying airplanes, or you die when flying airplanes!” He wasn’t one to sugar coat anything.

But automating doesn’t hurt! Beats crashing.


-GG

[fredmdbud]

Indeed! I posed a question on the F-14 thread about forgetting to pull up the flaps when sweeping the wings back and how to program it to automatically do it. The answer I got was, "Sometimes, we just have to accept the consequences for our actions and our inability to remember important stuff." (I'm paraphrasing a bit here.) I think something like this applies here.

At least on Spektrum transmitters, mixes can be programmed to be switched on and off based on a switch position (e.g. turn off steering when gear is raised).

In this case, the flaps can be negatively-mixed to itself (-100%/-100%) if the wing sweep is activated with a switch. Haven't checkd if this is possible with a knob/slider.

[kallend]

Indeed! I posed a question on the F-14 thread about forgetting to pull up the flaps when sweeping the wings back and how to program it to automatically do it. The answer I got was, "Sometimes, we just have to accept the consequences for our actions and our inability to remember important stuff." (I'm paraphrasing a bit here.) I think something like this applies here.

Given that the cost of crashes now attributed (rightly or wrongly) to forgetting to put the flaps up is now running into the $(tens of thousands), it seems that a little effort in programming to avoid the problem may be a good investment of time and effort

[xviper]

At least on Spektrum transmitters, mixes can be programmed to be switched on and off based on a switch position (e.g. turn off steering when gear is raised).

In this case, the flaps can me negatively-mixed to itself (-100%/-100%) if the wing sweep is activated with a switch. Haven't checkd if this is possible with a knob/slider.

I haven't figured that one out yet, but that's a topic for the other thread. Nevertheless, switch position for a wing sweep/flap position is complicated. IE, if you have flaps deployed, at the beginning of the sweep "back", sure the flaps can get sucked up immediately, BUT, when sweeping back out, as soon as that switch position is used, the flaps will deploy immediately, as the wings are still coming slowly out of their resting, swept back position, causing the flaps to force themselves against the fuse as they sweep "out". The flaps deploy while the wings are still in conflict with the fuselage. Like I said, I haven't figured that one out yet and it's something for the other thread.

[kallend]

I haven't figured that one out yet, but that's a topic for the other thread. Nevertheless, switch position for a wing sweep/flap position is complicated. IE, if you have flaps deployed, at the beginning of the sweep "back", sure the flaps can get sucked up immediately, BUT, when sweeping back out, as soon as that switch position is used, the flaps will deploy immediately, as the wings are still coming slowly out of their resting, swept back position, causing the flaps to force themselves against the fuse as they sweep "out". The flaps deploy while the wings are still in conflict with the fuselage. Like I said, I haven't figured that one out yet and it's something for the other thread.

Spektrum flap system allows flap movement to be slowed to accommodate exactly such a scenario. It's a menu option.

[Airguardian]

With gear down you set takeoff flaps as usual. Gear switch (A) then retracts the gear AND brings up flaps. Gear down for landing also sets 1/2 flaps. Only when you want full flaps do you use the normal flap switch, just as you normally would.

Learnt the hard way from experience that it is also a 'more-than-advisable' idea to keep (at least) the option to set flaps retracted when gear is down.

Otherwise, if a flap servo fails you are forced to land with a huge assymetry in lift between wings, causing a lot of rolling, yawing and nasty stuff in general terms.

I do use flaps alongside LG on a single switch in some jets myself, but I'd recommend either to separate them or have an override function to set flaps up with gear down in case of need.

[kallend]

Learnt the hard way from experience that it is also a 'more-than-advisable' idea to keep (at least) the option to set flaps retracted when gear is down.

Otherwise, if a flap servo fails you are forced to land with a huge assymetry in lift between wings, causing a lot of rolling, yawing and nasty stuff in general terms.

I do use flaps alongside LG on a single switch in some jets myself, but I'd recommend either to separate them or have an override function to set flaps up with gear down in case of need.

That is one of my flight modes. I described all of them previously.

[xviper]

Spektrum flap system allows flap movement to be slowed to accommodate exactly such a scenario. It's a menu option.

Yes, I'm aware of this, but in this particular case, it must be VERY slow or the flaps will hit the bottom of the wing housing. The wing sweep is very slow. The flaps cannot move more than 1/8" until the wings are almost fully extended. Even the slowest deployment may not be slow enough. I haven't checked yet. Then again, if they are that slow to deploy, they will be that slow to retract and may not be all the way up before they strike the housing.

[kallend]

Yes, I'm aware of this, but in this particular case, it must be VERY slow or the flaps will hit the bottom of the wing housing. The wing sweep is very slow. The flaps cannot move more than 1/8" until the wings are almost fully extended. Even the slowest deployment may not be slow enough. I haven't checked yet. Then again, if they are that slow to deploy, they will be that slow to retract and may not be all the way up before they strike the housing.

Set the delay you need in the sequencer. Can be different in the two directions.

[xviper]

Set the delay you need in the sequencer. Can be different in the two directions.

Thanks, I'll look at it over the winter. For the time being, I'll have to "live with the consequences of my actions".

[Airguardian]

That is one of my flight modes. I described all of them previously.

Just wanted to be sure and highlight the point! ;)

[viper1gj]

Keith and I flew our Mig-29 turbine conversions several times this weekend. The jet is great and my favorite of the conversions I have done. Getting 8.5 min flight times with all the wing stores on and landing with 2-3 min reserve fuel. The sweet spot seems to be around 65-85 mph. Final turn and approach is about 45mph and touch down at 35mph. Slow flight and high AOA is awesome. The jet will park in high AOA and is very stable. It can be held at about 70-80 degree pitch with thrust and will even start to tail slide if thrust is reduced. I did see the deep stall a few times and entry into a flat deep stall spin a couple of times. Recovery was prompt with lots of thrust, down elevator, and anti spin rudder. Not sure where the CG is now since I did several adjustments. It's probably around 160mm now. I started the weekend at 165 but it was a little too close to the edge for me as the nose wanted to hold a higher than desired pitch on final. Its really fun and easy to fly and I'm impressed with how tough the gear and airframe is. I has some turbine shutdown problems and did several dead stick landings before I got it sorted out. Two were hard high AOA tail first with nose slam down that stuffed the nose in the dirt. Each time the there was no damage except for a crumpled nose cone. New one on order. Over all a great fun jet to fly with some simple mods.
Gary

[GliderGuy]

No response yet from “Duke” to a PM requesting additional details about his configuration/setup/flaps which could provide more info about his crash.

Update: Flying with the MKS HV69 servos + Futaba SR-10 servo reverser continues with good results. About 50 flights with this set-up, so far. I’ve flown in conditions down to 40F/4.5C, and the SR-10 has not shown to be temperature sensitive (as related to position) at all. Color me happy!

-GG

[Evan D]

Current info from the poll I created on RCG.

14 have answered the poll
11 had the upgraded FW servos, 2 had the stock FW servos, 1 didn't say
1/3 bypassed the MCBe/ BB
1/3 upgraded the elevator pushrods
All had no mods to the elevator horns
1/3 had balanced the stabs
1/3 had a different BEC
2/3 used the factory balance marks
All believe their crash was loss of elevator control

[leithalweapon]

Current info from the poll I created on RCG.

14 have answered the poll
11 had the upgraded FW servos, 2 had the stock FW servos, 1 didn't say
1/3 bypassed the MCBe/ BB
1/3 upgraded the elevator pushrods
All had no mods to the elevator horns
1/3 had balanced the stabs
1/3 had a different BEC
2/3 used the factory balance marks
All believe their crash was loss of elevator control

How many had the flaps down?

[Captain MoMo]

Those servos are spec'd out at almost the same torque as the upgraded Freewing ones. Could it be that the HiTec servos meet their specs while the Freewing ones do not?

Xviper -that is exactly what I am concluding. Or perhaps some of the Freewing upgraded 23g servos are not meeting their specs (or are mixed up with 17g servos as they look the same with no markings) while others are just fine. I just flew two Migs - all built with the same mods except the servos. One had the Hitec D85MGs and the other the Promodeler DS100. The one with the Hitec servos at 5.1V performed fantastic and flew 8 flights of excruciating abuse (including full throttle with flaps) and survived. The one with the Promodeler DS100 servos almost crashed on flight no 2 - NO ELEVATOR ! The issue is the servo. The DS100 is a HV servo and operating it at 5.1V is on the lower end of the performance (speed and torque). I have the footage below FYI..

https://youtu.be/LATWowGFfrI

https://youtu.be/Hq2pKcHg3U4

https://youtu.be/z6S1EonBIcQ

https://youtu.be/sxxQ47QejXs

[xviper]

How many had the flaps down?

I think that this is too embarrassing to answer, as I believe we've already seen.

[Captain MoMo]

How many had the flaps down?

Good question to ask for sure - but I think that flaps are not the root cause. The root cause is most likely the inability of the elevator servos to handle the extra load due to flaps down at high speed. If the servos are replaced with a more powerful and capable set you will probably not crash due to loss of elevator - you may crash still but due to some other issue 😉