Unwanted brake activation

tshort · Post by **tshort** » Sat Mar 10, 2007 2:06 am

In my 170 when I press more than 1/2 or so of R rudder I get braking on the right. It is a little bit of a pain, the other day while taking off in a x-wind I could feel the plane decelerate when I used R rudder. Not to mention I think it could be a little dangerous.

I crawled under there and looked today. For some reason, when the R rudder is applied, the piston goes into the brake caliper a little. This only occurs with more than 1/2 of the travel of the pedal. It is not due to me putting my feet too high (I've heard "feet on the bottom of the pedals" too many times from my CFI!), as it happens if I move the rudders with just the bar that the pedal attaches to. I can't see any way to adjust the geometry so that this doesn't happen. Has anyone experienced this? If so, is there a fix? Any suggestions?

Thanks
Thomas

thammer · Post by **thammer** » Sat Mar 10, 2007 4:14 am

Same thing happened on my 140, shortened the rod a couple turns. Been working fine since.

tye

mit · Post by **mit** » Sat Mar 10, 2007 5:45 am

Look at the bottom of the brake master cylinder where it attaches to the tunnel, for cracks or busted loose.

Hope it isn't... I hate fixing them.

doug8082a · Post by **doug8082a** » Sat Mar 10, 2007 1:27 pm

This would be a good time to check all the linkages associated with the rudder pedals and brakes. After 50+ years, things get worn and/or broken. I had several problems including oblong holes in the rudder pedals where the Link (0411564) attached plus cracked and bent brake cylinder brackets (0411549, 0411550). Fixing/replacing these items made a noticable improvement in steering and brake use. You'd be surprised how much these worn parts can affect the use of the brakes.

Your emergency brake has been deactivated, right?

russfarris · Post by **russfarris** » Mon Mar 12, 2007 11:15 am

Doug meant parking brake, I'm sure!

If you still have the parking brake installed, get rid of it. It can cause all kinds of problems taxiing and landing in a crosswind, as I found out. Russ Farris

doug8082a · Post by **doug8082a** » Mon Mar 12, 2007 11:28 am

oops

Thanks Russ!

Romeo Tango · Post by **Romeo Tango** » Mon Mar 12, 2007 5:41 pm

It is an emergency brake - as in when it engages unexpectedly you have a class-I emergency on your hands(!)

RT

flyer170 · Post by **flyer170** » Tue Mar 13, 2007 2:07 am

I also disconnected the parking break.
But on another issue last year during the annual we found that the brackets that hold the master cylinders to the fire wall were both cracked. One was ready to fall off of the fire wall. I can't remember the exact location that the brackets fastened but I think you know what I'm trying to say. The mechanic that I worked with looked for that problem because of his recent experience with another 170 and his experience working on aircraft especialy 180's for MAF in South America for 20 years. He made new brackets for me out of stronger material and are now better than new. I would bet that there are more that a couple of 170's out there with this issue.
Bob

170Bpilot566 · Post by **170Bpilot566** » Wed Mar 21, 2007 11:26 pm

One of my old time c-170 pilot friends, told me if I ever got
a cessna 170b ,undue the emergeancy brake cables ,Later
this friend passed away, and I bought his cessna 170b ,and
the first thing I did ,was rehook up the cables,well I found
out my friend was right, I flew into a farm field and when
making a full brake all the way down ,the emergency brake
on the right wheel locked ,up swinging me around ,lucky no
damage ,only to my pride on not listning to my old friend ,I
bet I,ll listen closely to information with more concideration from now on., that was about 9 years ago and
its just as clear in my mind as if it were yesterday thanks
for the imput you members put in it is very informative and
may well save someone from having an accident and wrecking
our great cessna 170s and there was no problem with the brackets

Paul.
Member 6849

doug8082a · Post by **doug8082a** » Thu Mar 22, 2007 12:18 pm

I hope you removed the locking plates that fit around the master cylinder shaft as well. This is what actually locks the brakes and is responsible for the unwanted activation. When applying full rudder the lock plate hits the firewall and engages. See B model IPC page 100 - Figure 59 item 7 - p/n 0541141 (or 0541141-1, -2 for s/n 25000 and up).

170Bpilot566 · Post by **170Bpilot566** » Thu Mar 22, 2007 10:24 pm

Doug.,
Ok thanks I never took the clips out but will put the tail up and test the peddal travel, maybee the tops were screwed around but will check and let you know how
I made out. Thanks again

Paul

steve grewing · Post by **steve grewing** » Fri Jun 15, 2007 1:11 am

I have the same situation with my right brake. I had thought it was just my big feet getting in the way when I pressed full right rudder but after reading tshort's posting I checked and found the same problem. I have bottomed-out the adjustment and still have slight brake actuation. I see no problems with the installation. The pillow-block bearings for the rudder torque tubes have wear but not enough to induce a problem. I have noticed that the link for the dual brake pedal mechanism ('48 IPC fig 53 item 7 p/n 0411564, same as 170B IPC fig 60 item 18) at the pilots right pedal has no backlash on it when full right rudder is selected but the left pedal does have backlash remaining when full left rudder is selected. I get brake actuation at the same time I feel the rudder hitting the hardstop. I'm going to investigate this further but was wondering if anyone had any ideas.

Steve

The International Cessna^® 170 Association

Unwanted brake activation

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