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Re: Europa-List: Aerodynamicist question - Bud Yerly

Subject: Re: Europa-List: Aerodynamicist question - Bud Yerly
From: Pete <peterz@zutrasoft.com>
Date: Mon, 18 Jan 2021 12:08:59
Hi Bud,

Thx for the info as always!

I have never noticed the stab/ground effect deminishing authority..... ill h
ave to feel for it in the future :)

I luv the handling of my mono. EZPZ compared to my hummelbird lol.

https://youtu.be/1Wmep_9O5QU

Cheers,
Pete

> On Jan 18, 2021, at 10:53 AM, Bud Yerly <budyerly@msn.com> wrote:
> 
> =EF=BB
> Pete,
>  
> Years ago I looked and we are geometrically at the leading edge of the tri
angle.
> It is controllable, longitudinal wise.
>  
> Not unlike the early Maule and Pilatus with their forward placed gear, the
 planes were reluctant to wheel land nicely.
> The mono I have discussed before.  There are problems with a low stance fu
lly flapped plane approaching ground effect so as one would expect just look
ing at the aircraft.  It will be reluctant to wheel land easily as the CG to
 gear to MAC places the gear a bit forward.  At a point where the downwash o
n the tail plane is diminished by the runway, this causes the nose to drop (
many folks just never see this effect), the main wheel  then contacts the su
rface first.  As the main wheel contacts, the tail drops due to momentum of t
he CG to main wheel distance, the tail drops increasing the angle of attack a
nd the springiness of the gear shoots the plane back to a flying attitude ag
ain and the prudent pilot will go around.  My reflexes aren=99t quick e
nough to stop this near landing speed.  With a lot of speed it can be done b
ut then there are other problems being at speed on the ground in the mono.
>  
> The mono will delightfully obey a tail wheel first landing if the pilot an
ticipates the stab unloading due to downwash.  It is not happy being stalled
 and dropped in, especially if slightly askew to the alignment.  I=99v
e written how I land the mono.  That method works for me.  I have access to a
 long runway and use it to slow flight my way to feel my way to a nose high t
hree point (two point) landing tail wheel first.  Others, on short runways, c
ome in slow I=99m told (at about 55 Kts) and are able to round out tai
l wheel first and as the plane =9Csettles=9D they hold the nose u
p and stick it.  This requires deft skill and comfort in their aircraft.
>  
> In testing with the stall strips, this was an irritant to me as the wing w
ould unzip and quit flying just as I needed a bit more lift to stick the tai
l wheel first.  Lee Ohlmernick was patient with me and allowed me to work on
 my slow flight down the runway until I could see the point where the stab l
ost its power due to ground effect causing the nose to drop.  Keeping the pi
tch attitude for landing (not allowing the nose to drop) then was just a slo
w flight technique in ground effect to be mastered.  Once I had the motor sk
ill to add the right amount of stick just as ground effect took away a bit o
f stab authority (keep the landing attitude) touchdowns suddenly became rout
ine. I still go through a ritual on downwind of warming up my toes by quickl
y adding small amounts of rudder back and forth to prepare my stiff old ankl
es for the small amounts of movement necessary to maintain precise direction
al control.
>  
> I am not a gifted pilot.  It took practice.  It took flying often.  It too
k patience.
>  
> Do not neglect the importance of takeoff control either.  I have sat throu
gh a number of hair raising events in the Mono.  All on takeoff.  Tail wheel
 control is essential.  Keep the stick back on power application and be disc
iplined on directional control.  Do not allow any deviation from the centerl
ine.  Once above 35-40 Kts relax the death grip on the aft stick and concent
rate on the takeoff attitude (landing attitude) and maintain the pitch attit
ude until safely slow flighted off the runway and accelerating.  Never allow
 the nose to rise quickly as a stall may occur, maintain the pitch attitude.
  One can bring the tail up on the main above about 35 Kts, but remember, yo
u are now in a not quite ready to fly airplane and you will need all your fl
ight controls to maintain pitch and alignment until flight speed.  I prefer t
o just slow flight the plane off the ground.  Just as the main wheel begins t
o extend, hold that pitch attitude and it is delightful even with an 80HP en
gine and fixed prop.  Once off the ground, simply lower the nose a bit to in
crease acceleration.  Never put in full aileron on crosswind takeoffs as the
 plane will roll quite quickly at the stall.  Practice your slow flight at a
ltitude and see for yourself.  Cross winds in the Europa Mono are a bit stra
nge to most because it takes virtually no aileron to kick out the crab on la
nding.  Hence on takeoff, full aileron into the wind gives the pilot no feel
 of the speed and once the nose comes off the ground, the down aileron wing c
an stall.  Slow flight is the key for me.  Practicing slow flight at altitud
e and then again down the runway is how I relearn my mono feel.  If I can fl
y 1000 feet down the runway in the slow flight attitude and speed, I can lan
d.
>  
> Keep it straight, and the stick back.
> Bud Yerly
>  
> From: owner-europa-list-server@matronics.com <owner-europa-list-server@mat
ronics.com> On Behalf Of Pete
> Sent: Monday, January 18, 2021 9:30 AM
> To: europa-list@matronics.com
> Subject: Re: Europa-List: Aerodynamicist question - Bud Yerly
>  
> Bud,
> Do you know where the mono stacks up in these params?
> Cheers and thx,
> Pete
> 
> 
> On Jan 18, 2021, at 9:27 AM, Bud Yerly <budyerly@msn.com> wrote:
> 
> =EF=BB
> =46rom history Paul.
>  
> Raise the popular tail wheel aircraft and note the position in level attit
ude of the main axle to the leading edge of the mean aerodynamic chord.
> If you drop a plumb bob from the leading edge of a say a 7AC Champ or Cita
bria (rectangular wing so the mac is the leading edge)  the string goes thro
ugh the axle.
>  
> There are many aerodynamic effects as well as geometry effects to position
ing landing gear for a delightful conventional setup.
> As you push the stick forward, the main wing begins to go negative prevent
ing nose over as the tail cannot overpower the wings negative lift.
> The gear length allows a very near stall attitude at touchdown.
> The elevator position is such that it is above the wing downwash at touchd
own for stalled landings.
> Rudder area is such that the rudder can control the aircraft below stall s
peed.
> Fuselage area vs tail area and sideslip capability for crosswinds.
>  
> Geometry is important also.  Much has been written:
> The angle of the gear to the CG to the vertical CG axis longitudinally.
> The angle of the gear to the CG laterally for stability.
> Tail volume and length in relation to the gear. (AKA short coupled)
> Tail wheel to main gear distance in relation to gear width.
> Main gear movement in relation to touchdown forces (splay, compression, sp
ringiness etc.).
>  
> All these things determine whether a conventional gear aircraft is delight
ful or a handful to land.
>  
> Best Regards,
> Bud Yerly
>  
> From: owner-europa-list-server@matronics.com <owner-europa-list-server@mat
ronics.com> On Behalf Of Paul McAllister
> Sent: Sunday, January 17, 2021 10:16 PM
> To: europa-list@matronics.com
> Subject: Europa-List: Aerodynamicist question - Bud Yerly
>  
> Hi Bud (and anyone else who is knowledgeable on the topic)
>  
> I was once told l that there is an ideal front wheel position for tail drg
gers, something like 100mm in front of the MAC and that wheel placement of t
he mono was not ideal.  I can't remember where I heard this or if it was fro
m a knowledgeable source.
>  
> Would you happen to know if there is any validity in this?
>  
> Thanks and regards, Paul


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