REFLECTOR: Brake authority

[Darrell & Nora Kufalk]

I'm about to start my taxi testing.  Could someone give a quick rundown on
how to condition new brake pads and rotors?

 

Darrell

 

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Laurence Coen
Sent: Monday, June 04, 2007 7:12 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Brake authority

 

Hiroo,

 

I have a SE/RG Franklin with Matco brakes.  I do not have the toe brakes.  I
try to make the 1400 ft turn off and if that doesn't work there is a 1600 ft
exit.  If I am high and hot I have to coast to the 3000 ft exit.  If this
happens I have to add power to exit the runway promptly.  The total length
is 4100 feet and I have never had to use that much.  I understand that you
have a Franklin with a fixed pitch prop.  A Lycoming will idle at about 600
RPM but the Franklin has a range of 750-950 RPM so you are turning your prop
as much as 300 RPM faster than a Lycoming driver and are still in the normal
range for your engine.  In addition, a constant pitch prop set to flat pitch
will provide greater drag than your prop.  An experiment that you can try is
to pull the red knob to idle cutoff when the nose gear touches and I think
you will stop about 1000 ft shorter.  I have NEVER had hot brakes during
taxi.  Taxi should be touch and release, never drag a brake to correct for a
cross wind.  Anybody with a Velocity will tell you that starting from a
stand still with a cocked nose wheel is a bear.  That's normal.  Here's why.
Your gear are about 3' from the centerline of thrust and the nose gear is
about 9' from the mains.  For a thrust of 100 LBS there is about 33 LBS side
load on the nose gear because you are at a 3:1 mechanical disadvantage.  On
a Tiger the disadvantage is 1.25:1 which means at the same thrust there is a
80 LBS side load on the nose gear.  That's 2.5 times what you get on a
Velocity.

 

By the way, I have never seen  a Piper with a castering nose gear.  I have
flown a J-3 Cub, Tri-Pacer and flown a Cherokee for 16 years.  Even the Cub
had a steerable tail wheel.

 

The retract has an advantage in that there is good air flow over the brakes.
I hope this is of some help.  I also think that 2500 feet of runway should
be enough if you hit it right.  Don White used to operate out of an airport
in Buffalo NY with a 2600 ft runway.

 

Larry Coen

N136LC

SE/RG Franklin IVO

 

----- Original Message ----- 

From: Hiroo Umeno <mailto:humeno at microsoft.com>  

To: Velocity Aircraft <mailto:reflector at tvbf.org>  Owners and Builders list 

Sent: Monday, June 04, 2007 5:17 AM

Subject: Re: REFLECTOR: Brake authority

 

Scott,

 

Thank you for the insight.  I am starting to think that my brakes might be
"sub-standard" in that perhaps there is a trapped bubble somewhere.  I will
bleed it again and see if that makes a difference.  I will check for glazing
as well while the pants are off.

 

My transition training was done by Steve Murphree, I believe he is a factory
authorized and we did go through the airspeeds quite a bit.

 

Hiroo

 

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Baker
Sent: Monday, June 04, 2007 10:10 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Brake authority

 

Hiroo -

The Matco W600XT brakes are very effective for SUV, SE, LW/173 model
Velocity aircraft.

I don't recall if you have been to the factory flight transition training
program - to learn the importance of airspeed control on during landing.

We recommend an approach speed of 1.3 x Vs ...which translates somewhere
around 85-knots for fully loaded aircraft and around 80-knots when lightly
loaded.

On a 3000' runway plan on touching down within the first 500' to avoid the
need for heavy braking.

Fixed gear aircraft with wheel pants should also consider venting the pants
to allow ram-air cooling of the brake discs.

Also check the engine idle speed - and confirm you are able to pull the
engine power to full-idle during landing.  If the engine idle is high (by
100 rpm or more), this will add a lot to the landing distance.  Failing to
completely close the throttle during landing also places extra demands on
braking.

Make sure the brake were 'broke-in' correctly and that the discs are not
glazed.