REFLECTOR: grass strips

Sun May 26 07:05:51 CDT 2013

Gary,

Maybe adding VGs to the canard will help you rotate a little earlier from
the grass and avoid the dreaded 'bog down'!  I don't think you've put the
VGs on yet, correct?  They should lower your stall (rotate) speed as much as
5 kts.  Maybe you could also add a few extra washers above the nose gear
yoke and get a few fractions of a degree more nose up attitude...  

Beautiful plane when I saw it -- nice work on the build!  

But worrying about an (apparently) unpredictable 'bog down' on takeoff would
concern me, too!  And I would think the uneven-ness and little ruts in the
sod field would also make it bumpier, not smoother than asphalt.  One thing
I don't like about hard runways is that I can feel the hardness being
'reflected' back into the gear and plane during take-offs and especially
landings.  We may have more of that because of our extra-stiff NG motorcycle
strut.  But that makes a grass strip more attractive if it's actually
smoother, less bumpy and easier on the gear.

The other two things I would worry about permanently operating out of a
grass field are being grounded (unable to come or go) when it's wet, and
also the erosion of the prop leading edge from the sand that you mention.
As your hours build, I think that will be a problem in terms of longevity of
at least the MT prop.

All best regards!

Bob Jackson

N2XF

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of gapax2000 at juno.com
Sent: Saturday, May 25, 2013 6:27 PM
To: reflector at tvbf.org
Subject: Re: REFLECTOR: grass strips

Doug, 

  I am currently based at a well maintained 3300x150 foot grass field. There
are approx 75 planes based here and I have always wanted to keep the option
available of remaining at this strip where I have based an American Yankee
for the past 20 years. When I originally purchased my SEFG kit in 2003, the
first question I asked Scott Baker was "what do I need to do to keep the
option open of operating off a grass field?". Although he nor the Velocity
Factory endorsed flying off grass, Scott did give two recommendations in
order to even have a chance of operating off grass. The 1st was to install
the larger XL nose wheel and the 2nd was to install a 3 blade MT CS
propeller, both of which I did. 

  Now, 10 years later, the 1st flight of my SEFG was on 2-1-13 and I'm 25
hrs into the 40 hr test phase. Although limited, I hope I can offer what
experience I have gained so far. I am trying to break-in a 0SMO lycoming
IO360 with chrome cylinders so my main flights have been to take off, fly
greater than 75% power for one or two hrs maintaining acceptable engine
temps and then return to the field and land. The landings on grass have been
a pleasure being easy on the gear, tires, breaks, and the airframe as a
whole. I have only had to apply the brakes once on roll out. I've always
thought that landing would be the difficult part to master but on grass it's
the takeoff that's the real challenge. To date I've aborted 3 takeoff
attempts due failure to rotate. It feels like the nose is being pushed into
the ground and all acceleration stops at around 50 kts. It feels like you
just ran into a sand pit and everything bogs down. Once this happens you
know there's no way the nose is going to rotate no matter how long the
runway. I've had this occur with W&B in the 1st flight box and at the aft CG
limit ( tire pressure at 45 psi in nose / 55 psi in mains, trim set, and
2700 RPM at start of takeoff roll ). Aggressively "pumping" the elevator
sometimes helps and or backing off the throttle a couple hundred RPM's seems
to help lighten the nose. I believe this is all due to the nose tire drag on
the turf surface. The faster you go the more nose wheel drag is generated
and the more the thrust drives the nose down which causes more drag. My
plane actually sits about 1.5 degrees nose high after installing the Mishler
nose wheel lock which should actually make it easier to rotate. I had always
heard that the main negative concern with pushers operating off grass was
from FOD to the prop. Well so far after 25 hrs my prop is showing moderate
leading edge erosion from sand and only one 1"x1/8" ding toward the tip of
one blade (has been repaired) that was received while making a fuel stop at
a hard surface runway. This doesn't seem to be isolated to just me as I have
recently read several other pusher pilots relating similar experiences with
difficulty rotating on grass. 

  Anyway, as much as I'd love to stay at my grass strip, I don't enjoy
struggling with the physics of taking off on grass and will be moving to a
hard surface runway where not only the landings but the takeoffs have been
an enjoyable experience.   

Garry Paxton

SEFG flying 25 hrs

321-354-5109

Bob White Field X-61

Zellwood, Florida 

---------- Original Message ----------
From: "Douglas Holub" <douglas.holub at gmail.com>
To: <reflector at tvbf.org>
Subject: REFLECTOR: grass strips
Date: Sat, 25 May 2013 00:16:27 -0400

There's a cool little airport just three miles from where I live and I'm
thinking about hangaring the Velocity there.  But it's a grass strip, just
2700 feet long.  Is there a special technique for taking off from grass?
Maybe I should take some weight off the nose by pulling back on the stick a
little while I'm accelerating?

Of course, I'm worried about FOD to the prop.  I know some of you regularly
fly out of grass strips. Any advice?  (We have this discussion every now and
then, but I guess I don't pay that much attention unless it applies to me.)

Doug Holub

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