Brake Failure: Are You Prepared?

Aircraft Brake Failure

So, “there I was” …taxiing out to depart KHSP Sunday morning from the annual Twin Cessna Convention headed home to Hickory, NC (KHKY) when it happened.  Nice weather prevailed for a short, 45-minute flight from what can only be characterized as a terrific four days at the convention in Hot Springs, VA. 

Before engine start, and with feet on “hard” brake pedals, I fired ‘em up.  As I initiated the taxi, another quick brake check per SOP was normal, and I continued toward runway 7.  Approaching the hold short line, I applied the brakes, and my left brake went slam to the travel stop!  With both engines turning, the resultant differential braking began to quickly pull the aircraft to the right, setting me up for an excursion off a narrow taxiway.  Enter Rick McGuire and the training I received at AST. 

“Where’s the emergency brake on your 421”, Rick asked.  With a curious grin, and certain it was a trick question, “I don’t have one”, I replied.  Then I went to school.  We trained.  We practiced high-speed aborts on short runways in the simulator where braking alone was inadequate to avoid a potentially disastrous overrun.  Then he showed me the “emergency brake”.  He noted that if you pulled the mixture levers to idle cutoff, that stopping distance was significantly reduced.  We practiced some more.  It worked.  I never forgot it, and on Sunday, when I was about to run off the taxiway because my left brake failed, I pulled both mixture levers to idle cutoff and my plane stopped in its tracks on the right edge of the taxiway, avoiding an excursion.  But wait, there’s more…

During my ground training, Rick encouraged me to go online and buy a $9 plastic bottle on Amazon, and a $4 bottle of 5606A hydraulic fluid.   ( and a The bottle comes with an arched flex tube, and a tip that fits nicely into the filler plug of the master cylinder (located at the brake pedals). “Buy this stuff.  Keep it in your plane.  It will keep you from being AOG one of these days”, he insisted.   

The problem: apparently, it is not uncommon to find yourself with an individual brake failure due to the inherent design of the system.  Given the master cylinder reservoirs are so small, normal brake pad wear results in the caliper piston travel increase.  This “draws down” hydraulic fluid from the tiny reservoir, and can result is loss of hydraulic pressure, and thus braking.  There is such a small quantity of fluid in the system, that it doesn’t take much to deplete it.  Add some 5606 hydraulic fluid to your newly minted plastic bottle and fill the master cylinder; it doesn’t take much.  These are independently located at each brake/rudder pedal and are curiously the size of a roll of quarters on steroids.  There is a tiny plastic fill plug in the top.  Unscrew it, add the fluid, and replace the plug.  A few key notes here:  place rags or paper towels on the floor around the rudder pedals.  This prevents the fluid overflow during the filling process from getting onto the floor, and through the opening.  More importantly, it prevents that little plastic fill plug from falling into that abyss, never to be found if you drop it.   It’s a tiny little devil, so don’t drop it.  Did I say not to drop it?  This is the procedure Rick McGuire teaches.  This is what I did, and I was on my way after testing a newly functional and hard brake pedal. 

Naturally, a visual inspection of the brakes and master cylinders would be prudent to insure there are no obvious system leaks beforehand.  Better yet, if maintenance is on the field, you may want to get it checked first.   

While all owners may not be comfortable doing this, and should assess each situation with a critical eye, these are the types of tips and tricks that can prevent a costly and inconvenient AOG situation, or worse.  Had I run off into the bumpy turf, collapsed my right main, and ended up with a prop strike, I’d be facing six-figure repairs, and a seven-figure divorce.    Instead, the excursion was averted, and the issue was resolved in 15 minutes. 

I suppose most all knowledge gained in life is borrowed from others.  I find it infrequent that folks pioneer their ways forward solely on the shoulders of original thought.  The best of us trains often and seek to exceed insurance company and FAA minima, and I’m glad I elected to visit AST; two crises averted in one day courtesy of Rick and his bunch.  I want to be clear I am not an A&P.  This story is simply a factual account of how I was trained, what transpired, and the resulting outcome.

A special thanks to Bill Whiteford for “hanging around” to lend support and make sure I got safely on my way.  This is a fine group of brethren, these Twin Cessna owners…if you’re not a member of the organization, you’re missing out.  Here’s to staying teachable no matter your level of experience.

Blue skies…   

Eric Yeargain is an ATP, Gold Seal CFI/CFII/MEI, and a former 121 Captain and Check Airman.

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