Re: PT Brakes

David Stout · Post by **David Stout** » Mon Nov 06, 2017 9:45 am

'It is 1/2” , I used a brass plug...I don’t think the manual tells you to replace the vented plug, because as far as I know the airplane should not have had a vented plug in it to begin with.

ds

On Nov 6, 2017, at 9:59 AM, Steve Link steven_link@msn.com [fairchildclub] wrote:

Dang, I've read and reread the manual.....can't find where it says to replace the plug.
Not that I am doubting you, as it only makes sense to eventually vent the system. Just wondered where they hid it in all the procedures.
I'm going to get a solid plug tonight. Is it 1/2"? I can't remember and the hangar is 30 miles away!!!
Thanks for all the help!!!!!!!!!!!!!!!!!!

From: fairchildclub@yahoogroups.com on behalf of Steve Link steven_link@msn.com [fairchildclub]
Sent: Monday, November 6, 2017 5:47 AM
To: fairchildclub@yahoogroups.com
Subject: RE: [fairchildclub] Re: PT Brakes
Thanks, that is what I thought might be the case…. As stated on my e-mail yesterday I used Rockauto Raybestos MK-190 kits, my Cyl. Are 1”. Thanks so much for the clarification!!!!!!!!!!!!!!!!!!!!!!!!!!!! Steve in OK… From: fairchildclub@yahoogroups.com [fairchildclub@yahoogroups.com]
Sent: Monday, November 06, 2017 5:28 AM
To: fairchildclub@yahoogroups.com
Subject: Re: [fairchildclub] Re: PT Brakes The pressurization is used only to assist bleeding the brakes, it helps especially in getting the air out of the cylinder. After the brakes are bled completely and the bleeder valve is closed, top off the reservoir and replace the pipe plug...this is explained in the Fairchild maintenance manual. The problem I have is finding a rebuild kit....NAPA does not have it or at least could not identify it by the Wagner part number. ds
On Nov 6, 2017, at 6:17 AM, Steve Link steven_link@msn.com [fairchildclub] wrote:
I understand that, like I said the pipe plug is vented so the system cannot be pressurized.
Is that something that is done after pressurization? Swap plugs out? Is it pressurized all the time and I need to put a solid pipe plug in? I could find nothing in the T.O on pressurizing the system AFTER bleeding. From: fairchildclub@yahoogroups.com on behalf of wsknettl@centurytel.net [fairchildclub]
Sent: Monday, November 6, 2017 12:13 AM
To: fairchildclub@yahoogroups.com
Subject: [fairchildclub] Re: PT Brakes The master cylinder reservoir cap should have a pipe plug and a pressure valve stem. Here's a photo: http://willysmjeeps.com/v2/modules/gallery/albums/album535/DSC05645_sm.sized.jpg [url=https://eur03.safelinks..protection.outlook.com/?url=http%3A%2F%2Fwillysmjeeps.com%2Fv2%2Fmodules%2Fgallery%2Falbums%2Falbum535%2FDSC05645_sm.sized.jpg&data=02%7C01%7Csteven_link%40msn.com%7C505ed669e4854495b7ff08d524dd731c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636455455895145372&sdata=v76nHIikIeSFJD2u0Yr%2FuxH5NlCFNhTdFU1Bgld%2F7EM%3D&reserved=0]

[/url] http://willysmjeeps.com/v2/modules/gallery/albums/album5... View on willysmjeeps.com Preview by Yahoo

'

Steve Link · Post by **Steve Link** » Mon Nov 06, 2017 9:54 am

'
OK, Thanks!

From: fairchildclub@yahoogroups.com on behalf of David Stout aviator5@bellsouth.net [fairchildclub]
Sent: Monday, November 6, 2017 9:45 AM
To: fairchildclub@yahoogroups.com
Subject: Re: [fairchildclub] Re: PT Brakes
It is 1/2” , I used a brass plug...I don’t think the manual tells you to replace the vented plug, because as far as I know the airplane should not have had a vented plug in it to begin with.

ds

On Nov 6, 2017, at 9:59 AM, Steve Link steven_link@msn.com [fairchildclub] wrote:

Dang, I've read and reread the manual.....can't find where it says to replace the plug.
Not that I am doubting you, as it only makes sense to eventually vent the system. Just wondered where they hid it in all the procedures.
I'm going to get a solid plug tonight. Is it 1/2"? I can't remember and the hangar is 30 miles away!!!
Thanks for all the help!!!!!!!!!!!!!!!!!!

From: fairchildclub@yahoogroups.com on behalf of Steve Link steven_link@msn.com [fairchildclub]
Sent: Monday, November 6, 2017 5:47 AM
To: fairchildclub@yahoogroups.com
Subject: RE: [fairchildclub] Re: PT Brakes
Thanks, that is what I thought might be the case…. As stated on my e-mail yesterday I used Rockauto Raybestos MK-190 kits, my Cyl. Are 1”. Thanks so much for the clarification!!!!!!!!!!!!!!!!!!!!!!!!!!!! Steve in OK… From: fairchildclub@yahoogroups.com [fairchildclub@yahoogroups.com]
Sent: Monday, November 06, 2017 5:28 AM
To: fairchildclub@yahoogroups.com
Subject: Re: [fairchildclub] Re: PT Brakes The pressurization is used only to assist bleeding the brakes, it helps especially in getting the air out of the cylinder. After the brakes are bled completely and the bleeder valve is closed, top off the reservoir and replace the pipe plug...this is explained in the Fairchild maintenance manual. The problem I have is finding a rebuild kit....NAPA does not have it or at least could not identify it by the Wagner part number. ds
On Nov 6, 2017, at 6:17 AM, Steve Link steven_link@msn.com [fairchildclub] wrote:
I understand that, like I said the pipe plug is vented so the system cannot be pressurized.
Is that something that is done after pressurization? Swap plugs out? Is it pressurized all the time and I need to put a solid pipe plug in? I could find nothing in the T.O on pressurizing the system AFTER bleeding. From: fairchildclub@yahoogroups.com on behalf of wsknettl@centurytel.net [fairchildclub]
Sent: Monday, November 6, 2017 12:13 AM
To: fairchildclub@yahoogroups.com
Subject: [fairchildclub] Re: PT Brakes The master cylinder reservoir cap should have a pipe plug and a pressure valve stem. Here's a photo: http://willysmjeeps.com/v2/modules/gallery/albums/album535/DSC05645_sm.sized.jpg [url=https://eur03.safelinks..protection.outlook.com/?url=http%3A%2F%2Fwillysmjeeps.com%2Fv2%2Fmodules%2Fgallery%2Falbums%2Falbum535%2FDSC05645_sm.sized.jpg&data=02%7C01%7Csteven_link%40msn.com%7C505ed669e4854495b7ff08d524dd731c%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636455455895145372&sdata=v76nHIikIeSFJD2u0Yr%2FuxH5NlCFNhTdFU1Bgld%2F7EM%3D&reserved=0]

[/url] http://willysmjeeps.com/v2/modules/gallery/albums/album5... View on willysmjeeps.com Preview by Yahoo

'

tomatotruck993 · Post by **tomatotruck993** » Mon Nov 06, 2017 10:15 am

'Steve,
The original filler plug was an AN895-72. I cannot find any listing for this old AN spec. It was most likely a drilled brass pipe plug. The original valve stem was a Schrader #1954 which I believe is 1/8" pipe, but these are common today and are called air tank valves. Here's a link for them: http://www.rusindustries.com/valves-accessories/
I am using 01-115GA-2 dated Apr 43 & revised Sept 44 for maintenance manual and I don't see the references you are calling out the bleeding top air pressure requirement for. What manual are you using and what page are you on?'

cagog · Post by **cagog** » Tue Nov 07, 2017 10:11 pm

'I have an old set of AN standard books. Just for information purpoese AN895-72 is a sqare headed drilled iron pipe plug. the Brass version is a -b72. '

tomatotruck993 · Post by **tomatotruck993** » Tue Nov 07, 2017 11:08 pm

'Drilled horizontally for lock wiring or vertically for venting?'

cagog · Post by **cagog** » Wed Nov 08, 2017 12:27 am

'Drilled horizontally, post an email me at cagog@yahoo.com and I will replywith a scan of the two pages. Its one of the stranger AN standards I have seen. It covers about 8 different pipe fittings.'

Steve Link · Post by **Steve Link** » Wed Nov 08, 2017 4:51 am

'
Why not post it in the pictures folder so everyone can see it if they want?

From: fairchildclub@yahoogroups.com on behalf of cagog@yahoo.com [fairchildclub]
Sent: Wednesday, November 8, 2017 12:27 AM
To: fairchildclub@yahoogroups.com
Subject: [fairchildclub] Re: PT Brakes
Drilled horizontally, post an email me at cagog@yahoo.com and I will reply with a scan of the two pages. Its one of the stranger AN standards I have seen. It covers about 8 different pipe fittings.
'

Michael Kelly · Post by **Michael Kelly** » Wed Nov 08, 2017 7:55 am

'
I've been around the Fairchild PT's for over 40 years now. I've never seen a pipe plug in the reservoir drilled for venting. Remember! These planes were used for training and they did some inverted maneuvers back then. The 5 lbs of pressure is just for bleeding of the brakes, then it is released.

Keep 'Em Flying!

Mike Kelly
Fairchild Club

From: fairchildclub@yahoogroups.com on behalf of Steve Link steven_link@msn.com [fairchildclub]
Sent: Wednesday, November 8, 2017 5:51 AM
To: fairchildclub@yahoogroups.com
Subject: Re: [fairchildclub] Re: PT Brakes

Why not post it in the pictures folder so everyone can see it if they want?

From: fairchildclub@yahoogroups.com on behalf of cagog@yahoo.com [fairchildclub]
Sent: Wednesday, November 8, 2017 12:27 AM
To: fairchildclub@yahoogroups.com
Subject: [fairchildclub] Re: PT Brakes
Drilled horizontally, post an email me at cagog@yahoo.com and I will reply with a scan of the two pages. Its one of the stranger AN standards I have seen. It covers about 8 different pipe fittings.

'

tomatotruck993 · Post by **tomatotruck993** » Wed Nov 08, 2017 8:44 am

'For the same reasons that fuel tanks are vented on all gravity feed systems the brake reservoir requires the same venting for the same reason. As the system uses up fluid it will draw more until the vacuum/suction at the top of the reservoir starts restricting the flow of fluid to the master cylinders. The fact that these master cylinders can be pressurized for bleeding means the cap of these brake reservoirs must not be vented. If what you say is true then the the only way to ensure positive fluid supply in an un-vented reservoir is to maintain a pressure differential at least 1 or 2 pounds above ambient outside pressure. There are currently dozens of brake system reservoirs, both remote like this one or built into the master cylinders like most that all come with a fixed vent. At least 1/3 of these aircraft are routinely capable of inverted flight.
Now I too have spent over 50 years maintaining aircraft and no matter how many times I review TO 01-115GA-2 it remains unclear weather this reservoir must be pressurized all the time or only during bleeding. But simple physics dictates if it is not vented then it must always maintain a positive pressure differential at the top of the reservoir to endure uninterrupted fluid supply to the master cylinders.'

Francis Cox · Post by **Francis Cox** » Wed Nov 08, 2017 10:00 am

'I have vented plugs on the reservoirs in my Argus (UC61K) which have ball valves in them for inverted flight - work that one out!!!
Frank Cox

On 8 November 2017 at 14:44, wsknettl@centurytel.net [fairchildclub] wrote:

For the same reasons that fuel tanks are vented on all gravity feed systems the brake reservoir requires the same venting for the same reason. As the system uses up fluid it will draw more until the vacuum/suction at the top of the reservoir starts restricting the flow of fluid to the master cylinders. The fact that these master cylinders can be pressurized for bleeding means the cap of these brake reservoirs must not be vented. If what you say is true then the the only way to ensure positive fluid supply in an un-vented reservoir is to maintain a pressure differential at least 1 or 2 pounds above ambient outside pressure. There are currently dozens of brake system reservoirs, both remote like this one or built into the master cylinders like most that all come with a fixed vent. At least 1/3 of these aircraft are routinely capable of inverted flight.
Now I too have spent over 50 years maintaining aircraft and no matter how many times I review TO 01-115GA-2 it remains unclear weather this reservoir must be pressurized all the time or only during bleeding. But simple physics dictates if it is not vented then it must always maintain a positive pressure differential at the top of the reservoir to endure uninterrupted fluid supply to the master cylinders.

'