REFLECTOR: Brake authority

Mon Jun 4 19:11:43 CDT 2007

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 
  To: Velocity Aircraft 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.

  From your note describing trouble keeping the aircraft stopped during static-runup, it sounds to me like the glazed brakes or contamination of the brake pads.

  SB

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

    From: Hiroo Umeno 

    To: Velocity Aircraft Owners and Builders list 

    Sent: Monday, June 04, 2007 11:57 AM

    Subject: REFLECTOR: Brake authority

    I had a situation this weekend that heightened the "pucker factor" a bit.

    It was a rather warm day (80 or so at sea level) and I landed at a 3400ft long.  Upon touchdown, I braked more firmly than normal since it was a bit shorter a strip than normal.  About mid-way down the strip, I noticed that the rate of deceleration has decreased a bit.  I used the full length of the 3400ft to get it stopped and turned off the active.  The parking was at the other end of the field so I taxied back.  It was probably about 5 minutes in taxi and after getting to the other end of the 3400ft strip, I suddenly realized that I could only turn left.  To make matter worse, once I got the nose cocked left, I could not straighten it out, either.  I had to shut down, push the plane to the ramp, let the brakes cool off, then taxi.

    Now, I've always had an impression that the braking on my plane was "softer" than other planes I have flown in the past.  For example, on the Pipers with castering nose gears, I could make a "pin-point turn" by locking one wheel or another by standing on the brake.  Not on my plane.  I have the let the plane start rolling and then nudge the nose over gradually.  Also at run-up, I can barely keep it from creeping forward at higher RPMs.

    As I have the standard wing and fuselage (SUV), I have the Matco brakes.  My understanding is that the Cleveland upgrade is only necessary on the XL class aircraft.

    How much brake effectiveness should I expect on these Matcos?  I am starting to think I might have an air bubble or two in my lines.

    Hiroo

----------------------------------------------------------------------------

    _______________________________________________
    To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector

    Visit the gallery!  www.tvbf.org/gallery
    user:pw     Check new archives: www.tvbf.org/pipermail
    Check old archives: http://www.tvbf.org/archives/velocity/maillist.html

------------------------------------------------------------------------------

  _______________________________________________
  To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector

  Visit the gallery!  www.tvbf.org/gallery
  user:pw   Check new archives: www.tvbf.org/pipermail
  Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.tvbf.org/mailman/private/reflector/attachments/20070604/61e6c966/attachment-0001.htm 