Brake Inspections

How to keep the Cessna 170 flying and airworthy.

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GAHorn
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Brake Inspections

Post by GAHorn »

I have Cleveland brakes on my B-model and when I replace brake linings/pads I prefer the Rapco brand not just because they are less expensive, but also because they include an easily-observed wear-indicator on their linings. (Typical is .100” or one-tenth of inch remaining). The linings have small “divots” at each end and when those divots disappear from wear…. IT’s TIME to replace them.
BE899B2D-CA7A-4FB5-B48F-3F7BAF873506.jpeg
I’m posting this info/discussion-thread because one of our Members emailed me recently about some brake issues he’s having…. which prompted some of my sleeping brain-cells to wake-up and recall a learning event I experienced in my early/young flying which I shared with him.

Now that I’ve let the cat out of the bag I might as well share it for everyone’s entertainment…. here’s part of what I replied in my email to him:

I'm very picky about brakes.
Back as a younger aviator (1970, had maybe 200 hrs) I rented a previously-unknown-to-me C-175 from an A&P mechanic to fly to Western Texas for aerial inspection of a hunting lease one of the airport workers wanted to evaluate for his family. (side-note: It’s been my experience that, not all, and no offense intended to any of “Our” guys who may be reading this, but many A&P types, like plumbers, electricians, and auto-mechanics, might take considerable literary-license with mx records and be more willing to defer or accept mx items more readily than most owners. I have learned to take especial care when reading the fiction often contained in logs of airplanes being offered for-sale by those types. This particular episode may have been the first time I witnessed this hazard.)

When I rented it, the A&P owner mentioned that when I brought it back (the C-175) he intended to overhaul the brakes. I suppose that was his hint.... Which didn't sink in…

(Anyway, I rented the plane and picked up my line-man friend and we took off out of Houston for an unpublished strip near Boerne, Tx.)

We landed on this short grass strip at the base of a steep hill on the threshold which one had to negotiate at landing... And the only hangar on the strip was at the base of the hill.. which also had to be overflown at threshold. I'd never been there before and being a private strip (in those days) there was no prior info available on it... The discovery being made upon arrival.

To add to the challenges of the inexperience of which I was afflicted.... For the hunting-land-inspection flight, upon arrival My principal passengers' scarecrow thin uncle and "carnival fat lady wife" climbed aboard the back seats for the flight over the hunting area.
The high density altitude take off ran out of runway length so yours-truly just yanked back on the yoke and the airplane staggered into the air with stall warning screaming... And we listened to that noise for the next half mile as tree top branches scraped the bottom of both wings. Eventually sufficient speed was obtained to make the stall Horn shut up... And we slowly gained about 1K feet AGL .... And I finally summoned the courage to actually bank the airplane into a turn to go look over the property in-question.

When we came back to land, over the hill, scrape the top of the hangar,. And plop it down onto the grass...I applied brakes as I retracted the flaps for better wheel contact and braking... Only to feel the pedals have excellent, firm pressure... But the wheels behaved as if on ice.... The pedals were firm but the airplane seemed to actually SPEED UP!
It became evident we were not going to be able to stop before the departure end and the forest of trees rapidly growing larger in the windshield... There's was only a deep ravine / gully on the right,….full of car-sized boulders.... On the left were more trees and bystanders interested in this outcome... So that was out of the question... There was only an 8-foot pile of rocks at the far-left corner at the departure end which had been removed when the landing strip had been created years previously.... So that's where I headed.
With butt up off the seat cushion and full body weight applied to the useless brake- pedals we headed for the rock pile and to protect the nose gear as much as possible as the pile arrived I pulled full aft on the yoke... And THAT is where the fat lady gave her assistance... her weight forced the tail cone with it's tie-down ring to dig down into the earth and slowed us sufficiently such that we arrived at the rock pile with the mains and nose gear simply kissing the rocks as we dragged to a stop!! It looked as if I’d simply parked the airplane on the side of a huge pile of rocks!

My knees were shaking and it was damned difficult to get out of that thing with it's tail sitting on the ground held down so firmly by the combination of the rock pile and that huge woman, but we finally managed to get out and with considerable effort to extract her also.
When we examined the brakes it turned out that there was Zero lining material on the steel backing plate of those pucks. They were plain steel burned blue from heat.

With no way to make any repairs, my 200 flying-hours superior judgement was to return to our point of origin (Houston Hobby airport) to hand this plane back to it's owner.
Aware now of it's braking deficiency...I made certain to touch down ON the threshold of that 5,000' concrete Runway 35 at minimum speed... And even then, had to pull the mixture and turn off AT THE FAR END still traveling about 20 mph with the Brakes Applied!

I have ever since insisted on careful evaluation of braking action on any airplane flown over the next 13,745 hrs I've managed to cheat.

(I also make damned certain to look at the brake puck lining thicknesses when preflighting.)

Again, here’s where to look on Rapco’s
BE899B2D-CA7A-4FB5-B48F-3F7BAF873506.jpeg
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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c170b53
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Re: Brake Inspections

Post by c170b53 »

I'm was sweating just reading that. Last time I was at Oshkosh, several vendors were giving out Cleveland go, no-go gauges on a key chain.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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cessna170bdriver
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Re: Brake Inspections

Post by cessna170bdriver »

You know a post is too long when you have to reiterate the original thought at the end of the post in case the reader forgot what it was. :lol:

BTW, this reminder is a couple of months late for me. I use Rapco linings and had forgotten about those wear indicators. It was February, so I did the preflight before opening the hangar. I have translucent panels on the south-facing door so I didn’t bother to turn on the lights and missed the shiny spot on the painted floor indicating that fluid had leaked out of the right brake due to worn pucks. Fortunately the right pedal went to the floor when I attempted to hold the brakes for engine start, so I didn’t have to figure out how stop a taildragger with one brake. 8O (I’d rather be lucky than good any day…)
Miles

“I envy no man that knows more than myself, but pity them that know less.”
— Thomas Browne
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johneeb
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Re: Brake Inspections

Post by johneeb »

Jim, can you post a picture of the Cleveland go no-go brake wear gauge?
Last edited by johneeb on Sun May 01, 2022 2:08 am, edited 1 time in total.
John E. Barrett
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c170b53
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Re: Brake Inspections

Post by c170b53 »

I’ll try to post, next time I’m out at the hangar, I think I’ve left it on my aircraft’s key chain.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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GAHorn
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Re: Brake Inspections

Post by GAHorn »

The Technician Service Guide is useful for most Owners who don’t wander beyond disc, lining and O-ring replacements and have no interest (or capability/authorization) for detailed overhaul of components.
AWBTSG0001.pdf
Cleveland Technicians Service Guide
(2.36 MiB) Downloaded 95 times
One of the more useful illustrations contained in it:
9A6BDA08-47E9-4DB9-A897-9CCB000C5F9C.png

The Complete Component Overhauls Manual is contained in our Members-Only Mx Library: viewtopic.php?f=40&t=12047
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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GAHorn
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Re: Brake Inspections

Post by GAHorn »

Karl Towle wins the “Stump the Chump” Award by pointing out the first illustration I posted above indicating over-all thickness of back-plate, min-linings and disc …was using the PN: 164-0206 or 164-3206 Piper Aztec Disc……. NOT the PN: 164-02601 or 164-12601 discs (min thickness 0.205”) our 170s commonly use . The Technicians Guide provides the measurements for each model and part-number and should be followed during inspections. (Actually, the disc PN approved and installed on YOUR airplane should be consulted, especially if your brake system was installed using salvage parts or other than the STC’d Kit.).

(I have since edited/replaced the illustration to correct the error..)

Bad on Parker/Cleveland for publishing that like they did and Bad on me for copying the error.

Bottom line is that the Minimum Lining Thickness remains at 0.100”

Thanks, Karl!
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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c170b53
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Re: Brake Inspections

Post by c170b53 »

7C94A8C7-C1A8-4464-861F-72EFF6B4CC82.jpeg
Found it hanging on the cabin heat knob
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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johneeb
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Re: Brake Inspections

Post by johneeb »

Thanks Jim, couldn't get much simpler than that!
John E. Barrett
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Bruce Fenstermacher
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Re: Brake Inspections

Post by Bruce Fenstermacher »

c170b53 wrote:
7C94A8C7-C1A8-4464-861F-72EFF6B4CC82.jpeg
Found it hanging on the cabin heat knob
8O

I have one of those in my tool box. I inspect brake thickness several times a week and have never thought of using it. To convenient I guess. :(
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Bruce Fenstermacher, Past President, TIC170A
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