CTSW flap problems on final

[swedishCT]

Hey guys!

So I have this problem with my CTSW From 2004.

So I was out flying in December and Before flying I cycled though all the flaps positions from -12 to 40 and 40 to -12 and everything worked great.

Upon landing I switch the flaps from -12 > 0 and no problem here
Then 
0 > 15 and it worked great
Then
15 > 30 and this is where things started to go wrong.
The flaps stopped moving for a short while and then the flaps fully retracted! Fortunately, I managed to land safely.

Upon landing I reset the main power and the flaps worked flawlessly again.

----

Then 10h of flightime with no problems

----

Then today something similar happened!

Before flying I cycled though all the flaps positions from -12 to 40 and 40 to -12 and everything worked great.

Upon landing I switch the flaps from -12 > 0 and it worked great
Then 
0 > 15 and same here it worked great
Then
15 > 30 and this is, once again where things started to go wrong.
The flaps stopped moving and the display was only blinking "30".
After landing I selected 40 and the flaps retracted fully!

----

Both of these days the temperatur was below freezing around -5°C

Could someone please help me to troubleshoot this? Any ideas what might be causing this?

Sorry for my poor English! I live in sweden

[tevbax]

There is a topic on here about the flap motor having a difficult time. Some have disassembled to grease, but noted difficulties in doing so. 

We are having the same issue. -6/0 is fine. 0/15 seems to stop/start/stop/start when it is under freezing. 

 

[Madhatter]

Might consider regreasing with a low temp high pressure grease grease like Aeroshell 7. It's designed for gears and screw actuators. 

[Anticept]

These flap actuators are a known issue and they're expensive to replace.

I have one taken apart that can't be put back into service and what I found in its construction is disappointing.

They use a cheap chinese motor that I haven't been able to identify (and probably never will, it's like trying to find a specific needle in a needle stack) that has a pressed case to seal it so there's not even the chance of replacing the brushes, and the actuator tube that rises to move the flaps has several plastic pieces in it that the jackscrew rides in.

I hate these flap actuators, I've had to replace 5 motors so far on several CTs, and I was forced to buy a whole actuator on #5 because there weren't any used motors on the market. Those actuators things are EXTREMELY expensive and the manufacturer refuses to sell them directly.

I have had to regrease the actuators multiple times on each airplane I maintain.

Between all that and the numerous potentiometer failures, I really want to redo the flap system. An American made actuator, and a proper potentiometer that is built to tolerate vibration or even a non-contact potentiometer. The pots keep going bad with dead spots in them.

I know the manual says you can put the flaps down at 80 and 62, but I don't operate them until 70 and 55. You can already hear the motor straining to move the flaps, it sounds a lot better when you take the speed down even more.

[Madhatter]

6 hours ago, Anticept said:

These flap actuators are a known issue and they're expensive to replace.

I have one taken apart that can't be put back into service and what I found in its construction is disappointing.

They use a cheap chinese motor that I haven't been able to identify (and probably never will, it's like trying to find a specific needle in a needle stack) that has a pressed case to seal it so there's not even the chance of replacing the brushes, and the actuator tube that rises to move the flaps has several plastic pieces in it that the jackscrew rides in.

I hate these flap actuators, I've had to replace 5 motors so far on several CTs, and I was forced to buy a whole actuator on #5 because there weren't any used motors on the market. Those actuators things are EXTREMELY expensive and the manufacturer refuses to sell them directly.

I have had to regrease the actuators multiple times on each airplane I maintain.

Between all that and the numerous potentiometer failures, I really want to redo the flap system. An American made actuator, and a proper potentiometer that is built to tolerate vibration or even a non-contact potentiometer. The pots keep going bad with dead spots in them.

I know the manual says you can put the flaps down at 80 and 62, but I don't operate them until 70 and 55. You can already hear the motor straining to move the flaps, it sounds a lot better when you take the speed down even more.

How much is extremely expensive?

There are a huge number of linear screw actuators available for experimental aircraft. I'm sure there are some that could be adapted but for ELSA.

[Anticept]

Over a thousand for a USED one.

Brand new was approaching 2,000 and that was a couple years ago.

[BravoFoxtrot]

34 minutes ago, Anticept said:

Brand new was approaching 2,000 and that was a couple years ago.

Insert heart attack here!

[Madhatter]

8 hours ago, Anticept said:

Over a thousand for a USED one.

Brand new was approaching 2,000 and that was a couple years ago.

That's one reason I went ELSA. Because all parts must be approved by the manufacturer, it opens up abusive pricing policies. I always knew this would be a problem with SLSA.

[Roger Lee]

I always lube the large black rod and the smaller aluminum rod with a lot of Inox and let it run down the rods and then run the flaps all the way down and up to lube those rods so they don't drag being dry and metal to metal. I haven't had any issues since 2006.

[airhound]

Is there an age/hours kind of MTBF usage baseline? For example 2004 - 19 years of occasional over speeding flap actuations….

[Anticept]

I haven't been able to establish a pattern yet. I suspect it's people putting flaps down too early and straining the hell out of the system, ESPECIALLY in cold weather.

There is an O-ring in between the inner and outer shaft that I found hard as a rock on my 14 year old flap actuator and it was creating a lot of friction.

The reality is, these motors just seem to overheat and the overcurrent protection does a terrible job of protecting them (on the old flap controllers).

On failing flaps, the motors will run fine one direction, but run like trash in the other direction even on the bench.

I still have the motor that burned up that I last removed, I am going to cut it open one of these days to look at what is happening.

[Madhatter]

Already looking at substitute options. Talked to Airtime yesterday about getting an old failed assembly to use for dimensional analysis. There might have to be some modification but if you can't get the part there may not be a choice. I'm sure the flap board will no longer be valid. 

[Anticept]

I'll do you one better. Attached.

The model is MT10D-150

Hub size 150mm (not sure what the hub is, but I think it is the stroke length)

It also says

Nach: MT-30004

Fab.-Nr.MS.1458-251

ADE_MS-Katalog_Leichte-Baureihe_100624 bis 141231-1.pdf

[GrassStripFlyBoy]

On 2/9/2023 at 2:42 PM, Anticept said:

the manufacturer refuses to sell them directly.

I wonder if a legit manufacturing business (I'm owner of), inquired about purchasing in qty (say 10 or 12), they might accept that.  I understand businesses not wanting to sell piece items to general public, but MOQ as B2B might clear that hurdle?  I'll reach out to them, share the model number.

[Anticept]

They immediately told me to call flight design, and I didn't even mention that this was for aircraft. So I suspect the exact model is produced under contract.

A friend who works industrial engineering in Germany said that's common.

I updated my post above with the model number.

[Anticept]

P.S. the flap actuators are the same on CTSW, the LS with the lateral flap mixer (only a few were made), and the LS with the vertical one, with ONE exception: the top post where the rod end bearing screws into is different with the lateral flap mixer.

All flap control boards, old and new, work with all flap motor systems. The thing that changes between the old and the new revision of the controllers is the control board and the harness that goes to the flaps.

The old style flap board uses a controller on the panel, which controls a relay board mounted to the firewall.

The new style integrates everything on the board.

[FredG]

On January 17, 2022, I posted several photos of a disassembled CTsw linear actuator and described the procedure I used to disassemble and reassemble it.  My flaps actuator was slow and made a loud grinding noise in cold weather.  After disassembly, cleaning and lubrication, it works like new.  BTW, if you look at the photos I posted, you will see that it is not possible to spray lubricant on any external part of the linear actuator and expect that lubricant to reach the speed reduction gears nor the lead screw (jack screw) that moves the actuator shaft.  

Similarly to what Corey wrote, I deploy flaps at slower speeds than the maximum permitted by FD.  This puts less load on the linear actuator.  

I have also had two relay board failures on my plane (2006 CTsw with over 4000 landings).  Overall, in my opinion, the flap actuation system is overly complicated and too reliant on proprietary electronics.  When it works, it's very pilot friendly.  But, between unreliable electronics and a temperamental linear actuator (which is a PIA to access), the system leaves something to be desired.  

[Anticept]

I also had 2 relay failures on 2 different aircraft. It required reflowing the same joint. Another mechanic had to do the same on a third aircraft.

I then remount the board on vibration isolators. Never had a repeat.

The relay board is fine aside from the mounting on the firewall choice.

I can program an arduino to control these flaps no problem. I would choose one with a watchdog timer too, and program it not to move flaps on power up until the user chances the position switch.

[FredG]

I reflowed a failed solder connection on the first failure.  That board failed a second time some six years later but had no obvious failed connection.  So, I installed a new board I had on the shelf.

I would like to see an arduino controller for the flaps.  No matter how much I study the wiring diagram, I can't understand the circuit or the logic.

[Anticept]

On the old flap system, there are two discreet boards: the controller and the relay board.

On the controller, two wires power the board, three wires for the potentiometer acting as a voltage divider to sense position, and 3 more are the control wires (one common) to actuate the power relays on the relay board that move the motor. It also has a programming port for programming the flap positions and some pigtails for a position override to move the flaps manually for programming.

The common goes straight to the relays. The up and down control wires first go to the normally closed limit microswitches on the flap actuator (when depressed they open the circuit), then to the flap relay board. This allows the limiters to disconnect the signal to the relays and stop the motor even if the controller is calling for more flaps.

The relay board has power wires coming in, and two wires that go out to the motor terminals. Two more wires are for carrying the control signals for the relays, and one wire that is the common back to the control board. It also has some overcurrent protection on it that can be adjusted with a little onboard pot.

There are two relays on the relay board. Depending on if the signal for up or for down is sent, it triggers the relays in a way to send power either in normal or reverse polarity to the flap motor.

It would be trivial to control the old style flap system with an arduino. Arduinos are capable of sensing voltage, and the heavy lifting is done by the relay board, so bot much voltage is required.

In the new style board, it has power, ground, 3 wires for the potentiometer, and 2 wires for the motor, and some programming pigtails, and an onboard overcurrent protection pot. What eas 2 separate boards are instead one single board that costs something like 3000-4000 dollars now. This is much more difficult to replace because arduinos cannot handle the switching load and would require a more extensive replacement to install switching equipment somewhere that can.

[GlennM]

I thought there was a potentiometer on the flap control board that would adjust the maximum force the actuator could produce.  If the force was too low for the aerodynamic load, it would stop until the load lessened.  If it was set too weak, you would have trouble getting the flaps down under normal or slower speeds.  Try finding that potentiometer and increase the force allowed by the actuator. 

[Madhatter]

This flap system is way too complex, the result of some engineer that over designs things. I used to know with some of them and one I spoke to a few days ago. Most of the time simple is better but that doesn't impress the boss.

[FredG]

Glenn, yes there is a potentiometer on the flap relay board on the cabin side of the firewall (on my 2006 CTsw).  It controls the current (I believe) to the actuator (the current required varies according to the aerodynamic load).  Set it too low and the flaps will stutter as they deploy or not deploy until the airplane is slowed sufficiently.  Set it too high and the actuator may draw too much current (and either trip a breaker or damage wires or the motor, I am not sure).  

[Anticept]

That OCP (overcurrent protection) potentiometer exists on both the old and the new style flaps. It is supposed to stop the current supply if it takes too much current to move the motor. The new board style will actually display an overload warning for a few seconds before re-attempting movement. However, either the OCP is poorly set, or the circuit design's tolerances drift with time.

Motors have a maximum safe current draw. At rated speed with no load, a motor will draw almost no power at all because the movement of the motor also acts like a generator and generates a back EMF to oppose the incoming power. As you load it down, it wants to slow down, and the current will increase to try to keep it at rated speed. If you overload a motor, overcurrent protection will reach a tripping point and shut the power off.

However, I can really hear the motors straining if i put 15 flaps in at 80 knots. It sounds absolutely awful, and this is in several CTs.

A lot of chinese motors though way overstate their capability. They might run at that current for a bit but they're still damaging the coils or brushes.

The A&P school in my area has a growler. I should take the old weak motor there and test it...

[swedishCT]

Thxxxx alot for all the useful info! This forum is gr8. If you're ever in Sweden and would like to go flying, don't hesitate to contact me!