Jeremy=0AIt's a well known phenomenon called "putting the aircraft on the s
tep". I think it's explained by the reduced power required when the aircraf
t slows down=0Acompared to that required to accelerate to cruise speed.=0AW
hen "on the step" the slightest clumsyness with the controls will cause a l
oss of a good 5 knots (with a monowheel) Noticed this when handing over to
the right hand seat man=0Awho kept the stick moving continouously, " that's
how I was taught to fly!"=0AGraham=0A=0A=0A_______________________________
_=0A From: Jeremy Fisher <jffisher@gmail.com>=0ATo: europa-list@matronics.c
om =0ASent: Saturday, 6 October 2012, 3:06=0ASubject: Re: Europa-List: Fwd:
isher@gmail.com>=0A=0AFrans,=0A=0AI will probably regret this, but I will m
ake some guesses as to why climbing and then diving causes the speed to inc
rease.=0A=0AIt sounds to me as though you are seeing the airflow boundary l
ayer detaching early somewhere on the airframe at lower speed.- Then when
you accelerate after climbing then diving the flow is staying attached.-
I cannot think of anything else that would explain what you are describing
.- Early airflow separation can cause a considerable increase in drag.=0A
=0AThere may be another clue when you say that when you move the CG back, t
he speed increases to a point.- By doing this, you are decreasing longitu
dinal static stability, but also reducing the download on the tailplane (or
horizontal stab), causing a reduction in drag.- Once the tailplane is al
igned with the airflow, you have minimum drag from it.- Move the CG back
further the effect will taper off.=0A=0ASo it just could be that the airflo
w is detaching early on the lower surface of the tailplane in level flight
at your initial cruising speed, increasing drag.- By climbing, then accel
erating in a dive, you may be allowing the airflow to stay attached later o
n the tailplane, reducing the drag.- Then the reduced drag would allow yo
u to maintain the increased speed.- That is only a guess, and I have not
flown a Europa so am free to speak through ignorance!- You can check if I
am right by carefully measuring the fore and aft position of the stick bef
ore you start the climb, then again once it is back in level flight after t
he dive.- If it is slightly further forward after the dive, then this wou
ld confirm my guess.=0A=0AIf this does turn out to be the case, you might b
e able to delay the airflow separating by using small vortex generators on
the bottom of the tailplane.- An example for a different reason can be se
en on the Zenith STOL aircraft (to allow earlier rotation on take off).-
You can see this at http://www.zenithair.com/stolch701/pic09/vg701elevator.
jpg .=0A=0ANow you can all tell me that I am wrong, and why!!- Not many G
A aircraft use an all-moving tail, and this may just be a side effect of th
at.=0A=0AJerry=0AOn Oct 5, 2012, at 3:57 PM, Frans Veldman wrote:=0A=0A> --
=0A> On 10/05/2012 07:56 PM, Jeremy Fisher wrote:=0A> =0A>> Thanks for pos
ting the photos.- That is an impressive scheme that you=0A>> created, esp
ecially as it obviously works.- As a matter of interest,=0A>> what differ
ence do you see in aircraft performance?- Your cooling=0A>> drag must be
well down on the standard scheme.=0A> =0A> I think it is, but of course it
is hard to measure and judge. We also=0A> have an efficient prop and Fred K
lein's wing root fairings. On the other=0A> hand the aircraft is a tri-gear
, hi-top, and quite heavy. We never flew=0A> with the stock cooling configu
ration, or without the wing root fairings,=0A> etc.=0A> We usually cruise w
ith 27" to 28" of manifold pressure, and see an IAS=0A> of about 130 knots
at MTOW. At 100% we see a speed of 157 knots.=0A> =0A> Usually at FL95 or s
o we see cruise speeds of 140-160 knots.=0A> =0A> Measuring speeds drive me
nuts. The aircraft seems to stick to a certain=0A> speed, but pull up, div
e down, and after the dive the aircraft maintains=0A> a much higher speed t
han before the dive. I have heard this from more=0A> people. Anyone who kno
ws the cause? And then it looks like more weight=0A> in the back is benefic
ial, but only to a certain point. I'm still at a=0A> loss about how to get
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