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Al Downs

What speed to engage flaps

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I was taught to make sure I am below certain speeds before engaging flap settings, Today some one told me if the flaps were to be engaged at a higher speed, say 95 versus 80, the flaps would not be fully engaged until the speed is reduced and that you may hear it engaging in small steps until fully ingaged as the plane slows down. Is this correct? I don't want to try it and cause some damage.

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Last month I accidentally hit the switch and sent my flaps to 30deg after takeoff and at ~90kts. It took me about a minute to figure it out since I was absorbed in why the plane was mysteriously yawing hard to the right as I climbed. Then I finally noticed the flap indicator blinking 30. It had stalled the motor. The unit would not extend or retract the flaps at all even at slower speed and kept blinking its 'fault' 30 indication. As it turns out, I had to flip the switch over to manual and move the flaps up. Then the unit would repsond normally back in the automatic settings. It is worth mentioning since I also had no idea that this would work and only tried the manual mode since nothing else worked. I suspect cycling power to the flap motor would have cleared it too.

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Kurt, can you clarify? The flaps went to 30 degrees even though you were above speed limit for 30 and then stuck there until you cycled through manual? What causes the motor to stall?

 

Paul

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My guess is they made it to maybe 25deg before stalling the drive motor. The motor will overcurrent when trying to push the flaps down against high airflow. fully stalled would be the highest current. The microcontroller in the flap control unit is apparently coded to then not attempt to move the motor except for manual after an overcurrent fault.

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The force of the wind against the flaps can put a strain on the motor(s) that actuate the flaps. If they sense too much force, they cease operating and cause the indicator to blink (self protection mode). I can't remember what reset mine when that happens, but it was probably just waiting a while, until I slowed down a bit... or maybe Kurt's technique. There may be a heat sensor thing going on, too, which would auto-reset when it cools a bit.

Tim

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dear all CTFliers,

few question after read this;

 

1. so what is right speed knots to apply 15 and 30 flaps?

2. i always put flap 15 during base around 65knots and sometimes 15 indicator bliking (i thot was power not enough) and continue flap will jam a while then fully 15, same things happen to 30 as well during the final ...

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It's definitely trying to tell you that you're going too fast... but 65 kts should be plenty slow. Maybe you should clean up the gears and lubricate things a bit. My flaps have periodically gotten a little noisy and slow (plus the blinking thing), always remedied Roger's cleaning and lube.

Tim

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thanks Tim,

so do you have any idea the correct speed engaging flap 15 and 30?.

i did clean the gears flaps at wings (bolt with lube) as well inside quite ofter but still the indicator blink, i thot was power issue.

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dear all CTFliers,

few question after read this;

 

1. so what is right speed knots to apply 15 and 30 flaps?

2. i always put flap 15 during base around 65knots and sometimes 15 indicator bliking (i thot was power not enough) and continue flap will jam a while then fully 15, same things happen to 30 as well during the final ...

 

Hi Bobby,

 

The recommended flap deploy/operation speed for 15 deg flaps is 80KIAS. For 30 deg flaps and above the recommended speed is 62KIAS. Sounds like you are setting them well below that so you may have some debris clogging the flap mechanism found in the baggage compartment. If you look above the flap motor assembly there is a push rod system that moves the flaps. This can get dirty, dry, or sticky with the wrong lubrication or lack of lubrication. There is also a smaller tube in front of the main pushrod system that actuates the limit switches and the position potentiometer that can suffer the same problems.

 

There is also a current adjustment on the flap control unit that Roger Lee could explain more on.

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I've been experiencing something new with my flap indicator during the last few weeks. I get the usual blinking display while flaps are in motion, but now when moving to -30 or -35, it sometimes shows what looks like a lower-case 'o' on the left side, in front of the number.  This lingers for 5 seconds or so, the the 'o' goes away. The display does not flash during this time. Weather has been relatively cold lately, and perhaps this is a factor (?).    My first thought is that it may be an overload warning, although I've not had the breaker trip.  Has anyone else seen this?

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That's the overload warning. Yes, the cold makes it hard for the jackscrew to move. Basically its a safety cut out. The fuse or breaker is not meant to pop unless there's a SERIOUS issue.

Remember: the purpose of breakers is not to protect the device, it's to protect the wiring. They will be sized to the wires, not the load.

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5 minutes ago, Anticept said:

That's the overload warning. Yes, the cold makes it hard for the jackscrew to move. Basically its a safety cut out. The fuse or breaker is not meant to pop unless there's a SERIOUS issue.

Remember: the purpose of breakers is not to protect the device, it's to protect the wiring. They will be sized to the wires, not the load.

Thanks, Corey.  Any suggestions on corrective action?  This has been occuring while airspeeds are within limits for the flap selection. 

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So long as you are slow enough to engage your 35 flaps (50-60 knots) then before I got carried away I would go into the luggage compartment and lube the two flap rods. The large black one and the small aluminum one. Lube them well. No grease it's too thick. Use a spray like INox or something. Lube those rods well and then run the flaps full up and full down. Then go try and see if the flaps give you an issue. This could also be a low voltage issue, but try the lubing first. Very few mechanics lube these rods and they should each annual.

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12 hours ago, Roger Lee said:

So long as you are slow enough to engage your 35 flaps (50-60 knots) then before I got carried away I would go into the luggage compartment and lube the two flap rods. The large black one and the small aluminum one. Lube them well. No grease it's too thick. Use a spray like INox or something. Lube those rods well and then run the flaps full up and full down. Then go try and see if the flaps give you an issue. This could also be a low voltage issue, but try the lubing first. Very few mechanics lube these rods and they should each annual.

Thanks, Roger.  I plan to go out to the hangar today & try to figure this out. The maintenance manual doesn't help at all - is this area easily accessible, & can I do this myself?  In INox available at auto parts stores?  

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It's very easy to do yourself and the access is easy. Inox I get at Ace Aviation (Ace Hardware or True Value). Some here couldn't get it there so they get it online. 

Big can like I use. I spray all my rodends and hinges with this. It can't hurt the windshield or plastics if you over spray and has not solvents or distillates to cause harm. I can hear the difference on many CT's because after the spray the flaps are faster and don't drag down. Not all CT's have this issue though. I think some just get a dry rub. I spray the flap controls every annual.

http://www.guntherguns.com/product-p/inox-000017.htm

or small can.

https://www.ebay.com/itm/INOX-MX3-Spray-Lubricant-100gm-3-5-oz-Aerosol-Can-/320645925953

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Hi John.  Inox isn't available in Michigan so I go to Ohio to buy it.  I've been told that the Harley Davidson motorcycle shops carry this (but not in Michigan!).  I bought the gallon container and then use a small atomizer bottle to spray it.  The spray can of Inox is maybe best to just buy and use the red tube for accurate spray.  Interesting that you see a small "o" on the display.  Never saw this on my or Phil's CT but then we haven't had our flaps stall out.  I'm thinking it isn't a voltage problem.  You seem to have enough voltage to set off the "o".  My guess is lubrication is needed.

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The jackscrew is not exposed, it's inside a sleeve.  Do you just spray the exposed guide rod, and  spray at the top of the sleeve so it drips into the jack screw?

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Inox is not common but I found a local garage door company that carries it.  I'm fairly certain that I just need a lube, since my charging system and battery are both working nicely after a recent regulator replacement.   

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Update:

I got a hold of a jack screw and took it apart.

It uses Molybdenum disulfide paste. I do not recommend using any substitutes, that's a top shelf grease meant for EXTREME pressure and extreme temperature operation. Seriously it's the best stuff you can buy that's isn't some super specialty grease. The reason we don't use this everywhere is it's also super expensive, it's measured in grams when you buy it...

Be careful where you buy it too. That cheap stuff you can find on amazon for a big tube or can for 20 bucks only has a tiny amount of moly in it. A good grease will have a pretty high concentration, like Molykote M-77.

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You can't get grease down inside the flap screw jack that would do any good. Grease is a long term lube. Since you can't take your CT flap rod apart then something like Inox does work and when used on a regular annual basis it keeps things lubed. I've used it on a  hundreds of CT annuals since 2007 without any ill affects and has helped cure and or speed up flap deployment issues.

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You can't get the lubricant into the jackscrew itself spraying from the top. The jackscrew is surrounded by the actuator arm (it screws into the center of it). The actuator arm, in turn, is guided by the outer sleeve, which is what you see when you look at it assembled.

Basically you're lubricating the sleeve and that's fine. This is probably going to have the largest effect on the operation. But to lubricate the screw, disassembly is required.

Since it uses a moly paste, you're probably never going to need to lubricate the jackscrew directly. Moly is a lubricant is designed for the carrier fluid to disappear and the mechanism to run dry; the moly dust is a solid lubricant.

Now that said, the lubricant you spray WILL run down into the gearbox. The gearbox has two sets of roller bearings at the bottom of the jackscrew. The gearbox itself uses grease. Whatever lubricant you use, it needs to be robust for both sliding, roller, and gear surfaces.

image.thumb.png.c8c37747ede91c5cedaf59647aec5c33.png

 

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