Parking Brake

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jrenwick
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Re: Parking Brake

Post by jrenwick »

bagarre wrote:Are there any STC's out there to replace the parking brake system with another? Perhaps the hydraulic lock method?
If I remember right, one of our members has a field-approved installation of a dual hydraulic valve for parking, but I can't remember who it is. That ought to be pretty straight-forward, and you could even hook up the regular parking brake cable (a longer one, actually) to close and open the valve.
John Renwick
Minneapolis, MN
Former owner, '55 C-170B, N4401B
'42 J-3 Cub, N62088
'50 Swift GC-1B, N2431B, Oshkosh 2009 Outstanding Swift Award, 2016 Best Continuously Maintained Swift
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blueldr
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Re: Parking Brake

Post by blueldr »

A lockout valve would be ok until it happened to be inadvertantly closed when you really needed to use the brakes.
BL
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mccarlie
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Re: Parking Brake

Post by mccarlie »

jrenwick wrote:
bagarre wrote:Are there any STC's out there to replace the parking brake system with another? Perhaps the hydraulic lock method?
If I remember right, one of our members has a field-approved installation of a dual hydraulic valve for parking, but I can't remember who it is. That ought to be pretty straight-forward, and you could even hook up the regular parking brake cable (a longer one, actually) to close and open the valve.
I recently received a field approval for installing a Cleveland dual parking valve 60-5 in my 170. I will be sending a copy of my paperwork to HQ.
Parking Valve 1 pic.jpg
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krines
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Re: Parking Brake

Post by krines »

Had an interesting observation the other day. I had disabled my right parking brake because it had engaged on several occasions while landing due to what I thought was full right rudder deflection causing the locking tab to touch the carpet on the firewall thus engaging it. For some reason I could not duplicate this with the left rudder. It had happened so frequently that I became used to it and also made me quick on my toes. Since disabling the right parking brake I had no further issues for 300 hours. Well the other day while practicing short wheel landings I bounced one nicely without full left rudder. When I returned to the ground the left brake was on. Fortunately I knew what was going on and kept her straight. I think what happened was the bounce induced the parking brake tab to jump up and engage the small amount of break I had been applying. Just a thought. The left parking brake will now be disabled. Steve
King XII
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Re: Parking Brake

Post by King XII »

I really appreciate this forum. I have been wondering, ever since I replaced the pucks on my Cleveland, whether or not the pucks should remain in contact with the disc.
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krines
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Re: Parking Brake

Post by krines »

Brake pads never fully retract away from the rotor when not activated. Thus they remain in contact with the rotor to a small degree. If you think about the weight of the plane and the lever arm associated, the friction caused by this minor contact is negligable. It is a concern when slush water and then ice develops in sloppy conditions and the whole thing freezes together after takeoff. Most of the time it breaks apart on touchdown but not always. Steve
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Bruce Fenstermacher
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Re: Parking Brake

Post by Bruce Fenstermacher »

krines is correct of course with his answer to King XII. Unfortunately I just beheaded the King as he is a spammer. The question was asked verbatim by Robert Eilers on page two of this thread.
Robert Eilers wrote:I really appreciate this forum. I have been wondering, ever since I replaced the pucks on my clevelands, whetehr or not the pucks should remain in contact with the disc. Always thought that maybe I ahd reinstalled them incorrectly. Gahorn just cleared it up for me. I learn a great deal about my 170 just by monitoring this forum.
We've been hit recently with a rash of spammers who take the time to get through our security and join the forum and once here just duplicate old posts. To what end I don't know.

In any case the King is dead. I've deactivated his account but unfortunately his kind will be back. I've left his post only for continuity since krines took the time to answer it and the answer may serve useful for some one else.
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rnealon1
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Re: Parking Brake

Post by rnealon1 »

gahorn wrote:I hope it is appreciated that only the COMPLETE removal of the locking levers from the master cylinders will alleviate the problem. Merely disconnecting the Bowden cable, or disconnecting the yoke-cable will NOT prevent locking levers from locking the brakes.
Hi George,

How do I visually identify if the locking levers have been removed? Or are these internal in the cylinders?

Thanks,

Bob
Bob Nealon

Southbury, CT
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ghostflyer
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Re: Parking Brake

Post by ghostflyer »

What every body has said in this blog is true about parking brake issues. Those serrated shalf brakes have to go . They are dangerous . But when I put my old bag bones [aircraft] together it was fitted with late model brakes /cylinders and a umbrella handle to actuate the parking brake . There wasn’t any paper work. This I thought was a issue when cessna when contacted kept referring to how they changed the system and it was ok to do so . What about the paper work allowing me to do so . I am still waiting ...... I was given a STC put out by Parker authorising change over to the later style brakes cylinders /shalfs . Plus there was a STC for the double puk brakes also. We can get all emotion about it and some AI ,s get tearie eyed about the paper work but what about common sense. While we disconnect the park brake system [and feel good about it] ,you will need a park brake some day . Thanks why every aircraft produced has a park brake . NB. My system is similar to the Cessna 180 with a ratchet handle and cable .
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Bruce Fenstermacher
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Re: Parking Brake

Post by Bruce Fenstermacher »

There where 3 types of original master cylinders installed on 170s. They each have a different parking brake tab.

The first style master cylinder installed 18000 to 19199 had a serrated shaft.
ghostflyer wrote:Those serrated shalf brakes have to go . They are dangerous
The serrated shaft have nothing to do with the accidental parking brake application issue. The tab on those style master cylinder parking brakes is completely different and can not be activated by the firewall. There is an old SL that says the serrated shaft style master cylinders should be removed from service and replaced with the new style master cylinder the issue being the serrations in the shaft might cause shaft failure.
Serrations in shaft in red circle, Arrow points to different parking brake tab which does not have to be removed.
Serrations in shaft in red circle, Arrow points to different parking brake tab which does not have to be removed.
rnealon1 wrote:How do I visually identify if the locking levers have been removed? Or are these internal in the cylinders?

The next style installed serial 19200 to 20266 had a smaller and less prominent tab than the last style to come after it. I believe this style much less of an issue as it is less likely to be activated by the firewall and if clocked away from the firewall, as some are, can not be accidentally activated
Installed ser. 19200 to 20266 this style tab IMO is less likely to be accidentally activated
Installed ser. 19200 to 20266 this style tab IMO is less likely to be accidentally activated
Screen Shot 2020-04-20 at 8.05.26 AM.png (51.41 KiB) Viewed 11760 times
The last style installed, serial 20267 and on have the largest tabs and I believe the most problematic and should be removed or secured. I've colored the parts that must be removed to stop the parking brake from being inadvertently applied. Alternately these tabs might be wired down securely in some fashion to accomplish the same effect.
Tabs to be removed are in yellow.
Tabs to be removed are in yellow.
Tab to be removed in yellow
Tab to be removed in yellow
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rnealon1
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Re: Parking Brake

Post by rnealon1 »

Hi Guys,

Thank you for all the information.

This is what I see:
Brake Cylinder 1.jpg
Brake Cylinder 1.jpg (42.16 KiB) Viewed 11742 times
Brake Cylinder 2.jpg
Brake Cylinder 2.jpg (50.57 KiB) Viewed 11742 times
My serial number is 26181 so I assume the later installation type; it looks like they have been removed.

Thanks,

Bob
Bob Nealon

Southbury, CT
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GAHorn
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Re: Parking Brake

Post by GAHorn »

The question is sometimes asked “How do I document a basis of approval for disabling the parking brake?”... with varying opinions.

I do not find it anything other than a “minor alteration” for my own purposes. In my opinion, parking brakes have minimal usefulness in airplanes...and can be hazardous when used as initially intended. As a CFI, I discouraged their use except for the short time needed to find chocks.
I have personally observed pilots use them during pre-take-off checks such as engine run-up.... with their heads down in the cockpit... and their airplane creeping forward nearly into the airplane ahead. On one very memorable occasion I know a pilot who left the cockpit with the engines running because he tried to taxi with the tail tied to the ramp. When the tail was untied the aircraft almost got-away with pax’s on-board and a line of parked aircraft directly ahead.
Parking brakes should never be trusted, and in the case of the 170 they should be disabled and the activating levers removed, (and the system placarded INOP). If you agree this is a minor alteration, then all that is further necessary is a logbook entry. (All other SB’s recommended by Cessna should also be followed including replacing the early serrated shafts. Brakes ARE important and should be the one thing MORE reliable than the engine, IMO.)

The parking brake is not mentioned in the Type Certificate as “required equipment.” However, there is good argument put up by a personal friend (who happens to be an FAA Examiner) that a Form 337 should be generated to document the removal/disabling... his point being that the parking brake was original equipment per Cessna’s Production Certificate.... and therefore he believes it must be operational.
My counter to him is/was .... “unless it’s disabled and properly recorded in accordance with FAR’s.”
He replied, “Hummmpff”

I contacted FSDO-FTW and discussed it with the Maintenance Inspectors who seemed unwilling to address the matter at all. The most vociferous of them suggested getting a MEL approved addressing the matter. He also disbelieved it was possible for the parking brake to be inadvertently activated in-flight.

I’m satisfied with the logbook entry and the Park Brake knob being dis-abled/locked so no one can possibly believe they’ve activated it. YMMV

(PS: How to lock the Park Brake cable? Simply bend the wire back-over the end of the outer sheathing such that the knob cannot be pulled out at all.)
'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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ghostflyer
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Re: Parking Brake

Post by ghostflyer »

Just to throw a little move AVGAS on the fire , what does the insurance company say about disabling a aircraft system. One of my very learnered friends just told me that the serrated shalfs had to be removed that some were breaking [snapping] during application. I inquired where did he get his information and he claimed about 24 years ago he recalled some issues of that nature .
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GAHorn
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Re: Parking Brake

Post by GAHorn »

ghostflyer wrote:Just to throw a little move AVGAS on the fire , what does the insurance company say about disabling a aircraft system. One of my very learnered friends just told me that the serrated shalfs had to be removed that some were breaking [snapping] during application. I inquired where did he get his information and he claimed about 24 years ago he recalled some issues of that nature .
Pretty sure an insurance company would cover any loss as long as the airplane was in current license. (Annual inspection)
There is far too much worry about what an insurance company would or would not cover. They pay in all but the most obvious and deliberate violations of the policy conditions. A good example is in cases of clear “pilot error”. They still pay... and if ever there was a basis for denial it would be an owners error. I know of a guy over in College Station Tx that ran his Bellanca out of gas, and the insurance company bought him another one....THREE DIFFERENT TIMES! Same model. Same fuel problem. He didn’t know how the system worked and continued to do it over and over. They always paid.
'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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cessna170bdriver
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Re: Parking Brake

Post by cessna170bdriver »

Parking brakes may be “minimally useful”, but, like attitude indicators in VFR airplanes, when you need one they’re awfully nice to have. When I lived in California I used to frequent Kern Valley airport, where the parking ramp had about a 10% grade. If I was solo, the parking brake was the only option to give me time to get out and place chocks and tiedowns. Same thing applies if you ever have to park in a strong crosswind. (It would have NEVER occurred to me to use it during run up. :? )

Up until the Airframe rebuild, I kept the mechanical parking brake activated, but regularly checked the clearance between the activating levers and the firewall upholstery at full pedal travel, and never had an issue. During the rebuild I caved in to peer pressure and had the mechanical system removed, but replaced it with a hydraulic parking brake valve. Del called his FSDO about how to document the change, and they told him to do a logbook entry and not bother them with such trivial changes. It was little pricey, but well worth it IMHO. It is second only to the baggage door as my favorite convenience modification.
Miles

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