Brake Pressure .................. Check

[ahramin]

Brake Pressure .................. Check

Should I be doing this before each landing? Is this in any Cessna or Piper factory checklists? Has anyone on this board ever averted a possible incident because of this?

[Big Pistons Forever]

Brake Pressure .................. Check

Should I be doing this before each landing? Is this in any Cessna or Piper factory checklists? Has anyone on this board ever averted a possible incident because of this?

Seneca: Brakes worked fine on departure, 2 hours later on downwind I give the tops of the pedal a push and they go clunk, full travel with no resistance. Made a pan call, then touched down on the numbers and pulled both mixtures. Turned out the brake reservoir had a corrosion pit on the bottom. During the flight all the fluid drained out.

Citabria: Left brake was a bit soft on the taxi. Go to check it for the landing and nothing on the left side, so I went the long way around to take the crosswind from the left. Turned out the pad was worn enough so that it popped the O ring and lost all the fluid on that side.

[iflyforpie]

I do it before every landing. Never had anything go wrong in flight... but I've had tons fail before takeoff. I don't plan on having it surprise me. Takes half a second to do.


I don't believe it's on any official checklist. I don't think checking control sense is either, but that's another thing I always check.

[Redneck_pilot86]

Anybody doing stol work should be. Blind adherence to checklists is ridiculous.

[Jimmy2]

What if there was enough pressure for one application and you just used it checking them?

[teacher]

Saved myself a brake failure on a Cessna 172 by doing a brake check. Can't remember if it was in the air or on the ground. But remember it not feeling right so notified maintainece. Leak found in the system. Brake check in the air means you know what to expect. Doing one on the ground means you didn't have to leave in the first place.

[PilotDAR]

I don't recall ever seeing "check brakes" on a factory checklist. If you feel that you would like to check them before landing, that would be fine. If you don't feel the need, that's probably okay too...

I have experienced brake failure a few times. If prepared, this is not crucial. But, if you're flying an amphibious floatplane, or a taildragger in a strong crosswind, knowing you have no brake on one side before landing can prevent a nasty surprise after touchdown.

Generally, if I'm really going to need something to work while flying, I like to make an effort to check it before I need it...

[PilotDAR]

What if there was enough pressure for one application and you just used it checking them?

The brake pressure on an non assisted system comes from your foot, so running out is low risk. It is possible, and has happened to me several times, that there was a fluid leak, and yes, you could pump the last bit overboard checking them... But then, you could pump the second last bit overboard checking them, and have them still fail next use - which has happened to me. I still check anyway, if it's going to matter to me on the runway...

[ahramin]

I think I'll get into the habit of checking them, but leave it off the checklist.

[torquey401]

GUMPS

[cgzro]

Citabria: Left brake was a bit soft on the taxi. Go to check it for the landing and nothing on the left side, so I went the long way around to take the crosswind from the left. Turned out the pad was worn enough so that it popped the O ring and lost all the fluid on that side.

Had same problem on the ground with my plane (same brakes) fluid just started dripping over the pads after a landing. Turned out the slave cylinder(puck) was installed backpards so that the O ring was closer to the outer face of the puck than the inner and hence became exposed whe then brakes were worm but still had a bit of life left.

[7ECA]

Had a failure on the ground in a tail dragger, after engine start and prior to taxiing. While waiting for ground to get back to me, my left foot slumped all the way forward on the pedal. So, gave it a few pumps to make sure I wasn't imagining it, and then shut down to take a look. Sure enough, hydraulic fluid all over the ground...

Can't remember exactly what failed, but it was nice to catch it on the ground. I don't see any issue with giving the brakes a quick pump before landing, and will continue to do so.

[ba31pilot]

Two things to add:

1. We had a brake failure on final in a JetStream 31 once. The check was in the checklist...was sure good to be able to warn the ground crew we'd be without normal brakes.

2. On the Cessna jets, a brake check IS in the Cessna checklist. I don't believe this holds true though for the small pistons. It is VERY valuable though.

[AOW]

On some aircraft types, the parking brake can be (inadvertently) activated in flight, trapping any pressure one or both of the pilots (depending on design) applies to the brakes after the parking brake handle is engaged. On some of my favourite airplanes, the designers grabbed the parts for "Parking Brake Handle" and "Cockpit Air Control" from exactly the same parts bin, and proceeded to install them directly one above the other, with only a few inches and switches in between. The unfamiliar or complacent pilot could, at some point in flight, decide that there is too much environmental air getting pumped onto his feet, so decide to pull out on the knob that controls this, but accidentally pull out on the parking brake knob. This wouldn't cause any problems, until there was pressure built in the pilot's brake master cylinders, which would then be held trapped. So one could argue that doing a brake check in this machine could cause a problem that not doing one would avoid.

I am not, however, suggesting avoiding brake checks in this type of airplane. There are enough other times that you apply pressure to the rudder pedals in flight that could put some pressure into the brakes, or even if you didn't tap the brakes up until landing, as soon as you touch the brakes after landing, if the parking brake was accidentally applied, you will probably be in for a startle! If you land with the parking brake applied, kiss your tires goodbye, and hope that somebody got to witness the cloud of rubber smoke!

So my advice is: do your brake check, but don't just feel for available pressure, make sure that you feel the brake pressure release as you lift your feet off the brakes. Try intentionally setting the parking brake and feeling the difference (while safely standing still), so you can identify this next time you find yourself in a situation that should be recognizable, and avoid the associated embarrassment!

[oldtimer]

On the Metro series airplanes, we always STOMP on the brakes after gear extension to maybe break the pucks free when we taxi in winter. Do not know if it helps but it makes everone feel better. Metro's are terrible for frozen brakes. If you taxi through snow, nothing helps but very light snow picked up by the props can cause the brakes to freeze. Sometimes the flat spots on landing go all the way to the internal air.

[HiLo]

When I did my PPL in a DA20 (where the pedals, not the seats, adjust fore/aft). The first thing I was taught to do after adjusting the pedals is to check the brakes. The day after my first solo, my instructor and I got into the airplane, I adjusted the pedals and tapped the breaks -- the left brake went to the floor. Got out of the airplane: lo and behold, there was a puddle under the left tire.

I think brake tests should be second nature to pilots, especially on the ground. It's like doing a walk-around or a control check: if you need a checklist to remind you of it, you probably shouldn't be flying.

[PostmasterGeneral]

On the same note, what are thoughts on hitting the brakes after takeoff before gear retraction? I've always just let them spin down inside the wheel well, but I've flown with guys who are adamant about making sure the wheels are stopped before retraction. Don't see how it matters either way, there would be enough drag on the brakes and bearings to stop the wheels in a few seconds anyways?

[MrWings]

If your brakes are out, wouldn't you want to know before you needed them?

And from the Cessna retractable POH:

Before retracting the landing gear, the brakes should be applied momentarily to stop
wheel rotation. Centrifugal force caused by the rapidly spinning wheel expands the
diameter of the tire. If there is an accumulation of mud or ice in the wheel wells, the
rotating wheel may rub as it is retracted into the wheel well.

[upintheair_]

Brake Pressure .................. Check

Should I be doing this before each landing? Is this in any Cessna or Piper factory checklists? Has anyone on this board ever averted a possible incident because of this?

Yes, happened about a month ago. Low pressure on the right side. Turned out to be air in the lines, and was able to get pressure by pumping them up. ALWAYS check brake pressure, after the gear is deployed.

[PilotDAR]

Before retracting the landing gear, the brakes should be applied momentarily to stop
wheel rotation. Centrifugal force caused by the rapidly spinning wheel expands the
diameter of the tire. If there is an accumulation of mud or ice in the wheel wells, the
rotating wheel may rub as it is retracted into the wheel well.

Yes, but.... apply the brakes gently while doing this. The same force which expands the outside of the tire also can affect the bead, and thus the fit to the rim. The brakes stop the rim, and then the tire, based upon the fit of the tire bead to the rim. If the rim stops instantly, and the tire not so quickly, you could shear off a valve stem. A few tires actually have "lugs" which lock the tire to the rim, to prevent such slipping.

I do apply brakes before retracting, but I ease in the brakes, not jam them on....

[GyvAir]

As to the original question: Check them.. you have nothing to lose and potentially lots to gain in knowing something is wrong.
I've also heard tales from pilots of knowing or suspecting that they had a frozen brake and proceding accordingly, based on the pedal feel being too firm .

The same force which expands the outside of the tire also can affect the bead, and thus the fit to the rim. The brakes stop the rim, and then the tire, based upon the fit of the tire bead to the rim. If the rim stops instantly, and the tire not so quickly, you could shear off a valve stem. A few tires actually have "lugs" which lock the tire to the rim, to prevent such slipping.

I won't pretend to understand all the physics involved in the different scenarios here, but wouldn't the tire be more prone to slipping on the rim under hard braking on the pavement where the friction between pavement and tire will help keep the tire spinning, along with the tire's inertia? The same rotational speeds would be involved, so I would expect similar expansions of the tire to occur, setting it up for a slip.

[oldtimer]

I rode as a passenger on an Air Canada Express Dash 8 and after take-off, I could feel a bit of vibration from the wheels that stopped in a minute or so as they spooled down. Some airplanes specifically prohibit applying brakes and some suggest you let the wheels slow on their own. Some airplanes had a rubber bumper to slow or stop rotation.
I saw an Airbus A320 depart and climb to well over 1000 feet before retracting the gear so I asked an Airbus knowledgable person why and the answer was that they probabily MEL'd one set of brakes and had to leave the gear down long enough to make sure the wheels stopped rotating before retracting them.
Some Cessna twins had very little clearance between the tires and the wing and if the retreaded tire "grew" due to centrifugal forces, the tire could jam, preventing extension. Most turboprops just let them spin down.

[photofly]

I won't pretend to understand all the physics involved in the different scenarios here, but wouldn't the tire be more prone to slipping on the rim under hard braking on the pavement where the friction between pavement and tire will help keep the tire spinning, along with the tire's inertia? The same rotational speeds would be involved, so I would expect similar expansions of the tire to occur, setting it up for a slip.

I don't believe for an instant the radius of the tire grows significantly under rotation, but regardless of that, it's entirely plausible - even inevitable - that with the wheel coming to a sufficiently sudden stop the stick-tion of the tire against the rim won't be enough to prevent the tire slipping. It's exactly like the tire skidding on a tarmac surface except in this case the skid is happening at the interface between the rubber and the rim.

[photofly]

On the subject of "centrifugal growth", from Aircraft Landing Gear Design: Principles and Practices
By Norman S. Currey

"Clearances between the tire and adjacent parts of the aircraft shall be based upon a 3% growth in tire section width and height from the MIL-T-5041 dimensions. In addition, unless the tire is prevented from spinning during retraction, an extra 2.5% increase in section height should be allowed for centrifugal growth."

[Strega]

Seneca: Brakes worked fine on departure, 2 hours later on downwind I give the tops of the pedal a push and they go clunk, full travel with no resistance. Made a pan call, then touched down on the numbers and pulled both mixtures. Turned out the brake reservoir had a corrosion pit on the bottom. During the flight all the fluid drained out.

Interesting... didnt know brake hyd oil could flow uphill...