X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 16 Jul 2010 05:57:11 -0400 Message-ID: X-Original-Return-Path: Received: from web36901.mail.mud.yahoo.com ([209.191.85.69] verified) by logan.com (CommuniGate Pro SMTP 5.3.8) with SMTP id 4394940 for lml@lancaironline.net; Thu, 15 Jul 2010 22:01:24 -0400 Received-SPF: none receiver=logan.com; client-ip=209.191.85.69; envelope-from=chris_zavatson@yahoo.com Received: (qmail 94660 invoked by uid 60001); 16 Jul 2010 02:00:48 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=qnQB0oGZOCENH2NwBFwOYn3ZwGShBigIxwHlaIiuEkRBSpOxkXr+eF//apH0YPuDWPOm5O4Nwo+494QMPYIYOQ3KF6RWvYk7aEskhIphOphKojCXhxzWZKRuf41tJADNGA1lFKdvp1h72g41UX82jfO8lRDJip/zUt1D08cC8zw=; X-Original-Message-ID: <721207.93563.qm@web36901.mail.mud.yahoo.com> X-YMail-OSG: iWgnK6sVM1mi1NsNlm5uc3VpQ4HF9Mu7PFv5WQg86rzzn5Z WFn65LGzVpY0YGmVTdsYDkhRhfHGOx1jhMhFPIt0dOJ8HnWXv7ZFTSigdXpE RsYSXh41Rn8FBIEHltTOEQhIvy5RizsG9BwV3XxLEDLhrAH010YuVzDNT0Hg ICjKqwB6ujEtcjLEzgZ6wBNLoaU45ig0IL6ePEtTx0TCpxVpGhRpDwZYUAuR A5VmxZ4V.lSQ5LmZCYcL6J422NrFUu6CnQOripLKfFLUE_YY0XDpTmmLe8EZ WnnAcOfrYvPpEyQF4Or14dCbPbXduPU6qgTZrlJmoLaGsb2OnHoVSXwo5lXe rstvJIHvwnFUFOOcr96C0cXjifAPoHpL.BLY1VQ-- Received: from [149.32.224.33] by web36901.mail.mud.yahoo.com via HTTP; Thu, 15 Jul 2010 19:00:48 PDT X-Mailer: YahooMailRC/420.4 YahooMailWebService/0.8.104.276605 References: X-Original-Date: Thu, 15 Jul 2010 19:00:48 -0700 (PDT) From: Chris Zavatson Subject: Re: [LML] Re: Small tail, MK II tail, CG range X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1746559858-1279245648=:93563" --0-1746559858-1279245648=:93563 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable =0A=0AThere appear to be different definitions for MAC out there.=A0 I am m= ore familiar =0Awith MAC being used for=A0"mean aerodynamic center".=A0 I s= uppose MAC could =0Aalso=A0refer to "mean=A0aerodynamic chord", as you poin= t out.=A0 My text on stability =0Aand control (Etkin) uses =AFc (with the b= ar over the c) for "mean aerodynamic =0Achord".=A0 It is easy to tell which= definition is meant in diagrams or =0Aequations.=A0=A0It is definitely not= as clear in textual form.=A0 I suppose it is best =0Ato spell out the inte= nded definition.=0A=A0=0AChris Zavatson=0AN91CZ=0A360std=0Awww.N91CZ.com=0A= =0A=A0=0A=0A=0A=0A________________________________=0AFrom: H & J Johnson =0ATo: lml@lancaironline.net=0ASent: Thu, July 15, 201= 0 4:08:18 PM=0ASubject: [LML] Re: Small tail, MK II tail, CG range=0A=0A=0A= Chris, do you have any references as to the Neutral Point being the same as= the =0AMAC [mean aerodynamic chord]?=0AAll the book's I've owned tell me t= he MAC is calculated on the wing =0Aplatform/shape while the NP is derived = from this and the tail volume [which=A0is =0Acomposed of=A0an arm, MAC and = a area value]. =0A=0AJust wanted to confirm what is correct and incorrect. = Also, do you have any =0Afeedback as to how the Aerodynamic Center applies = to all of this?=0A=A0=0AThanks=0AJ. Johnson=0A235/320 55% [and holding]=0A= =A0=0A> Wolfgang, et al =0A> The aircraft MAC (also called neutral point) r= elative to CG is the =0A> key to =0A> evaluating aircraft longitudinal stab= ility.=A0 This is independent =0A> of whether the =0A> tail=A0is providing = an up or down force (either=A0can be stable).=A0 =0A> Longitudinal =0A> sta= bility is defined by the reaction of the entire airframe to a =0A> disturba= nce =0A> from equilibrium.=A0 The size, location and pitching moment =0A> c= haracteristics =0A> of=A0each component factors in (wing, tail, fuselage = =0A> etc.).=A0=A0Evaluating the =0A> behavior of=A0just the wing is not suf= ficient to describe the =0A> response of the =0A> aircraft as a whole and c= ertainly not to quantify the response.=A0 =0A> Actually, a =0A> wing sectio= n alone=A0will be unstable as the pitching moment is =0A> negative.=A0 It i= s =0A> stable when inverted - flying wings have negative camber for this = =0A> reason.=A0=A0=A0 =0A> A stable=A0aircraft must=A0have a=A0positive pit= ching moment when in =0A> equilibrium.=A0=A0In =0A> order to be stable, the= pitching moment coefficient=A0must=A0have a =0A> negative=A0slope =0A> wit= h increasing angle of attack.=A0=A0This provides an increasing =0A> opposin= g=A0moment to =0A> an increasing disturbance.=A0=A0 =0A> A=A0larger tail in= creases the response when a disturbance occurs.=A0 =0A> It is a =0A> functi= on of the larger=A0area producing more=A0restoring force for=A0any =0A> giv= en=A0angular =0A> disturbance.=A0=A0The size of the horizontal stabilizer= =A0feeds into=A0a =0A> quantity called =0A> the tail volume ratio -=A0a uni= t-less measure of relating tail area =0A> to wing area =0A> and wing mean= =A0wing chord to distance to the horizontal =0A> stabilizer.=A0 More area = =0A> or=A0a longer tail increase the effectiveness in terms of stability. = =0A> The neutral point=A0is fixed by=A0the configuration of the =0A> aircra= ft.=A0=A0Only =0A> configuration changes will move the neutral point.=A0 Lo= wering the =0A> flaps, for =0A> example, changes the airfoil, relative inci= dence angles, pitching =0A> moment of the =0A> wing and so on.=A0 In all co= nfigurations the neutral point must =0A> remain well behind =0A> the CG.=A0= 10% of the mean chord length is a good starting minimum.=A0 =0A> Once the = =0A> neutral point is known, the incidence angles and CG can be set.=A0 =0A= > What will fall =0A> out is the trim airspeed.=A0 That is,=A0in equilibriu= m the aircraft =0A> will seek out a =0A> specific angle of attack and the c= orresponding airspeed.=A0 One can =0A> play around =0A> with=A0different co= mbinations of=A0incidence angles and CG locations =0A> to achieve both =0A>= a stable aircraft and minimum trim drag at any desired airspeed.=A0 =0A> h= ope that helps, =0A> Chris =0A> =0A> =0A> =0A> Chris Zavatson =0A> N91CZ = =0A> 360std =0A> www.N91CZ.com =0A> =0A> =A0 =0A> =0A> =0A> =0A> __________= ______________________ =0A> From: Wolfgang =0A> To: lm= l@lancaironline.net =0A> Sent: Wed, July 14, 2010 10:37:18 AM =0A> Subject:= [LML] Re: Small tail, MK II tail, CG range =0A> =0A> =0A> I'm not familiar= with MAC as applied to the entire airframe, can =0A> you elaborate? =0A> I= think there may be a problem with that idea since the tail is =0A> typical= ly =0A> providing a down force which would move the "airframe MAC"=A0to the= =0A> front, not the =0A> rear. =0A> =A0 =0A> Wolfgang =0A> =0A> __________= ______________________ =0A> =0A> ----- Original Message ----- =0A> >From: C= hris Zavatson =0A> >To: lml@lancaironline.net =0A> >Sent: Tuesday, July 13,= 2010 8:35 PM =0A> >Subject: Re: [LML] Small tail, MK II tail, CG range =0A= > > =0A> > =0A> >Wolfgang, et al, =0A> >< and a larger =0A> >tail doesn't help much= with that anyway.>> =0A> > =0A> >A=A0larger tail moves the MAC rearward al= lowing the CG to move =0A> farther aft while =0A> >maintaining the same lev= el of stability. =0A> >There has been=A0a lot of discussion about Cm.=A0 We= need to be =0A> careful to =0A> >distinguish between the Cm for the wing, = tail and total =0A> aircraft.=A0 It is the =0A> >later that is critical to = stability and this is where the larger =0A> tail influences =0A> >the situa= tion.=A0 The large tail moves the MAC to the rear approx. =0A> 1.5 inches.= =A0 =0A> >For the same CG, the more rearward MAC produces a greater =0A> re= storing force if the =0A> >plane is disturbed from level flight.=A0 The pra= ctical benefit for =0A> us is that it =0A> >allows=A0a lot more baggage to = be thrown the rear of the plane =0A> before =0A> >suffering=A0stability pro= blems.=A0 You pointed out the other benefit =0A> of increased =0A> >control= authority at slow speed with full flaps. =0A> > =0A> >Chris Zavatson =0A> = >N91CZ =0A> >360std =0A> >www.N91CZ.com =0A> > =0A> > =0A> > =0A> > =0A> __= ______________________________ =0A> From: Wolfgang =0A= > >To: lml@lancaironline.net =0A> >Sent: Tue, July 13, 2010 2:51:23 AM =0A>= >Subject: [LML] Small tail, MK II tail, CG range =0A> > =0A> > =0A> >The q= uest continues. =0A> > =0A> >I'm checking further into the data on these qu= estions and am =0A> coming to question =0A> >the need for a larger tail. I'= m not sure a larger tail by itself =0A> will solve the =0A> >problem. After= doing some static and in flight measurements, it =0A> looks like the =0A> = >tail authority is not a big problem, if a problem at all. =0A> > =0A> >Sta= tic measurements of N31161 have shown "vanilla" parameters. =0A> 2.5=BA inc= idence =0A> >between the wing root at full reflex and the tail and a 1.3=BA= =0A> washout. Put the =0A> >flaps at 0=BA and you get an additional AoA of= 1.8=BA at the root for =0A> a total =0A> >incidence of 4.3=BA . . . . not = radical at all. =0A> > =0A> >What is interesting is the POH (Dec. 1994 pg. = VI-3) gives the CG =0A> range as 24.5" =0A> >to 30.3" aft of the rear face = of the fire wall and the MAC at 15% =0A> to 20% =0A> > =0A> >. . . well . .= . no . . . that range is more like a MAC range of =0A> 15% to 30% - - =0A>= >- a good range made touchy only by the small size of the air frame. =0A> = > =0A> >After going over the plan view kit drawings, I come up with a CG = =0A> range of =0A> >23-1/4" to 29-1/4" for a MAC range of 15% to 30% =0A> >= That range is about 1-1/4" forward of the book and fits better =0A> with fi= rst hand =0A> >flight experience. =0A> > =0A> > =0A> >Any more to the rear = and you get negative stability at cruise and =0A> a larger tail =0A> >doesn= 't help much with that anyway. =0A> > =0A> >Negative stability makes pitch = control a real chore. As Scott K. =0A> has indicated, =0A> >going to 0=BA f= laps helps under that loading condition. =0A> > =0A> >Too far forward and l= anding becomes "interesting". A larger tail =0A> can help there =0A> >. . .= or don't use as much flaps. =0A> > =0A> >I think understanding these condi= tions can help everyone. =0A> > =0A> >. . . The quest continues . . . Comme= nts welcome. =0A> > =0A> >Wolfgang =0A> > =0A> >=A0 =0A> > =0A> ___________= _____________________ =0A> =0A> >From: "Wolfgang" =0A>= >Sender: =0A> >Subject: Small tail, MK II tail, C= G range =0A> >Date: Sat, 10 Jul 2010 21:01:11 -0400 =0A> >To: lml@lancairon= line.net=A0=A0 =0A> >The LNC2 uses the NLF(1)-0215F airfoil. A lot can be f= ound by =0A> doing a Google =0A> >search on that number. =0A> >More detail = can be found by=A0going to Google for "NASA Technical =0A> Paper 1865". =0A= > > =0A> >I have not taken the time to reverse engineer the CG range of the= =0A> LNC2 but let =0A> >me offer some observations. =0A> > =0A> >The airfo= il used has long been touted as "the greatest thing =0A> since sliced bread= " =0A> >for General Aviation and it definitely has some advantages. But =0A= > it's not new. =0A> >Compare this airfoil to the P-51 airfoil and you will= see some =0A> close =0A> >similarities. The LNC2 being composite construct= ion instead of =0A> aluminum lets the =0A> >airfoil show more of it's theor= etical advantages. =0A> > =0A> >It's a laminar shape with a good drag bucke= t. That bucket can be =0A> made to move to =0A> >the lower Cl (lift coeffic= ient) ranges with reflex allowing =0A> noticeably lower =0A> >drag at highe= r cruise speeds. Along with reflex, the Cm (moment =0A> coefficient) =0A> >= goes positive, the center of lift of the wing travels forward =0A> giving a= nose up =0A> >force requiring down trim. This is in addition to the usual = nose =0A> up force that =0A> >goes with most all airfoils=A0at high speed b= efore considering flaps. =0A> > =0A> >With down flap, the drag bucket will = move to higher Cl's making =0A> slower flight =0A> >more efficient. And, of= course, the Cm goes negative giving a =0A> nose down force =0A> >requiring= up trim. =0A> > =0A> >. . . and appropriate variations in-between . . . = =0A> > =0A> > =0A> >So, the rear CG limit is determined by high speed fligh= t and =0A> available control =0A> >authority, =0A> >and the forward CG is d= etermined by low speed / landing flight =0A> and available =0A> >control au= thority. =0A> > =0A> >What is becoming clear here is that the center of lif= t does quite =0A> a bit of =0A> >traveling fore and aft which is exaggerate= d by allowing negative =0A> or "cruise" =0A> >flaps. Since you can't shift = the CG during flight, you need a =0A> large amount of =0A> >pitch authority= from the tail to cover that range of lift travel. =0A> >=A0 =0A> >You have= two choices in the LNC2, live with the limitations or =0A> install a large= r =0A> >tail to give that extra pitch authority. =0A> >. . . A larger tail = area can also help with=A0abnormal =0A> attitude=A0recovery.> =0A> >Wolfgan= g =0A> > =0A> =0A> =0A>=A0=A0=A0=A0=A0 =0A-- For archives and unsub http:/= /mail.lancaironline.net:81/lists/lml/List.html=0A=0A=0A --0-1746559858-1279245648=:93563 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
 
=0A
There appear to= be different definitions for MAC out there.  I am more familiar with = MAC being used for "mean aerodynamic center".  I suppose MAC coul= d also refer to "mean aerodynamic chord", as you point out. = My text on stability and control (Etkin) uses =AFc (with t= he bar over the c) for "mean aerodynamic chord".  It is easy to tell w= hich definition is meant in diagrams or equations.  It is definit= ely not as clear in textual form.  I suppose it is best to spell out t= he intended definition.
=0A
 
=0A
Chris Zavatson=
=0A
N91CZ
=0A
360std
=0A= =0A

 
=0A

=0A
=0A=
=0AFrom: H &am= p; J Johnson <hjjohnson@sasktel.net>
To: lml@lancaironline.net
Sent: Thu, July 15, 2010 4:08:18 PM
Subject: [LML] Re: Small tail, MK II tail= , CG range

=0A

=0A

=0A

=0A

Chris, do you have any references as to the Neutral Point being the same a= s the MAC [mean aerodynamic chord]?

=0A

All the book'= s I've owned tell me the MAC is calculated on the wing platform/shape while= the NP is derived from this and the tail volume [which is composed of=  an arm, MAC and a area value].

=0A

Just wanted= to confirm what is correct and incorrect. Also, do you have any feedback a= s to how the Aerodynamic Center applies to all of this?

=0A

<= STRONG> 

=0A

Thanks

=0A

J.= Johnson

=0A

235/320 55% [and holding]

= =0A

 

=0A

> Wolfgang, et al
> The aircraft MAC (also = called neutral point) relative to CG is the
> key to
> evalua= ting aircraft longitudinal stability.  This is independent
> of= whether the
> tail is providing an up or down force (either&nb= sp;can be stable). 
> Longitudinal
> stability is define= d by the reaction of the entire airframe to a
> disturbance
>= from equilibrium.  The size, location and pitching moment
> ch= aracteristics
> of each component factors in (wing, tail, fusel= age
> etc.).  Evaluating the
> behavior of jus= t the wing is not sufficient to describe the
> response of the
&= gt; aircraft as a whole and certainly not to quantify the response.  <= BR>> Actually, a
> wing section alone will be unstable as th= e pitching moment is
> negative.  It is
> stable when in= verted - flying wings have negative camber for this
> reason.  &nb= sp;
> A stable aircraft must have a positive pitching= moment when in
> equilibrium.  In
> order to be st= able, the pitching moment coefficient must have a
> negati= ve slope
> with increasing angle of attack.  This pro= vides an increasing
> opposing moment to
> an increasing= disturbance.  
> A larger tail increases the respons= e when a disturbance occurs. 
> It is a
> function of th= e larger area producing more restoring force for any
>= ; given angular
> disturbance.  The size of the horiz= ontal stabilizer feeds into a
> quantity called
> t= he tail volume ratio - a unit-less measure of relating tail area
&= gt; to wing area
> and wing mean wing chord to distance to the horizontal
> stabilizer.  More area
> or a = longer tail increase the effectiveness in terms of stability.
> The = neutral point is fixed by the configuration of the
> aircr= aft.  Only
> configuration changes will move the neutral p= oint.  Lowering the
> flaps, for
> example, changes the = airfoil, relative incidence angles, pitching
> moment of the
>= ; wing and so on.  In all configurations the neutral point must
&g= t; remain well behind
> the CG.  10% of the mean chord length i= s a good starting minimum. 
> Once the
> neutral point i= s known, the incidence angles and CG can be set. 
> What will f= all
> out is the trim airspeed.  That is, in equilibrium t= he aircraft
> will seek out a
> specific angle of attack and = the corresponding airspeed.  One can
> play around
> with different combinations of incidence angles and CG = locations
> to achieve both
> a stable aircraft and minimum t= rim drag at any desired airspeed. 
> hope that helps,
> = Chris
>
>
>
> Chris Zavatson
> N91CZ > 360std
> www= .N91CZ.com
>
>  
>
>
>
>= ________________________________
> From: Wolfgang <Wolfgang@MiCo= m.net>
> To: lml@lancaironline.net
> Sent: Wed, July 14, 2= 010 10:37:18 AM
> Subject: [LML] Re: Small tail, MK II tail, CG rang= e
>
>
> I'm not familiar with MAC as applied to the en= tire airframe, can
> you elaborate?
> I think there may be a = problem with that idea since the tail is
> typically
> provid= ing a down force which would move the "airframe MAC" to the
> front, not the
> rear.
>  
> Wolfgang <= BR>>
> ________________________________
>
> ----- O= riginal Message -----
> >From: Chris Zavatson
> >To: lm= l@lancaironline.net
> >Sent: Tuesday, July 13, 2010 8:35 PM
&= gt; >Subject: Re: [LML] Small tail, MK II tail, CG range
> > <= BR>> >
> >Wolfgang, et al,
> ><<Any more to= the rear and you get negative stability at cruise
> and a larger > >tail doesn't help much with that anyway.>>
> > <= BR>> >A larger tail moves the MAC rearward allowing the CG to mo= ve
> farther aft while
> >maintaining the same level of st= ability.
> >There has been a lot of discussion about Cm.&nbs= p; We need to be
> careful to
> >distinguish between the C= m for the wing, tail and total
> aircraft.  It is the
> >later that is critical to stability and this is where the lar= ger
> tail influences
> >the situation.  The large ta= il moves the MAC to the rear approx.
> 1.5 inches. 
> &g= t;For the same CG, the more rearward MAC produces a greater
> restor= ing force if the
> >plane is disturbed from level flight.  T= he practical benefit for
> us is that it
> >allows a = lot more baggage to be thrown the rear of the plane
> before
>= ; >suffering stability problems.  You pointed out the other be= nefit
> of increased
> >control authority at slow speed wi= th full flaps.
> >
> >Chris Zavatson
> >N91CZ=
> >360std
> >www.N91CZ.com
> >
> >=
> >
> >
> ________________________________
= > From: Wolfgang <Wolfgang@MiCom.net>
> >To: lml@lancaironline.net
> >Sent: Tue, July 13, 2010 2:51:23 AM > >Subject: [LML] Small tail, MK II tail, CG range
> > > >
> >The quest continues.
> >
> >I'm= checking further into the data on these questions and am
> coming t= o question
> >the need for a larger tail. I'm not sure a larger t= ail by itself
> will solve the
> >problem. After doing som= e static and in flight measurements, it
> looks like the
> &g= t;tail authority is not a big problem, if a problem at all.
> > <= BR>> >Static measurements of N31161 have shown "vanilla" parameters. =
> 2.5=BA incidence
> >between the wing root at full reflex= and the tail and a 1.3=BA
> washout. Put the
> >flaps at = 0=BA and you get an additional AoA of 1.8=BA at the root for
> a tot= al
> >incidence of 4.3=BA . . . . not radical at all.
> >
> >What is interesting is the POH (Dec. 1994 pg. VI-3) give= s the CG
> range as 24.5"
> >to 30.3" aft of the rear face= of the fire wall and the MAC at 15%
> to 20%
> >
>= >. . . well . . . no . . . that range is more like a MAC range of
&= gt; 15% to 30% - -
> >- a good range made touchy only by the smal= l size of the air frame.
> >
> >After going over the pl= an view kit drawings, I come up with a CG
> range of
> >23= -1/4" to 29-1/4" for a MAC range of 15% to 30%
> >That range is a= bout 1-1/4" forward of the book and fits better
> with first hand > >flight experience.
> >
> >
> >Any = more to the rear and you get negative stability at cruise and
> a la= rger tail
> >doesn't help much with that anyway.
> > > >Negative stability makes pitch control a real chore. As Scott K.
> has indicated,
> >going to 0=BA flaps helps un= der that loading condition.
> >
> >Too far forward and = landing becomes "interesting". A larger tail
> can help there
&g= t; >. . . or don't use as much flaps.
> >
> >I think= understanding these conditions can help everyone.
> >
> &= gt;. . . The quest continues . . . Comments welcome.
> >
>= >Wolfgang
> >
> > 
> >
> ____= ____________________________
>
> >From: "Wolfgang" <Wol= fgang@MiCom.net>
> >Sender: <marv@lancaironline.net> > >Subject: Small tail, MK II tail, CG range
> >Date: Sat,= 10 Jul 2010 21:01:11 -0400
> >To: lml@lancaironline.net &nb= sp;
> >The LNC2 uses the NLF(1)-0215F airfoil. A lot can be found= by
> doing a Google
> >search on that number.
> >More detail can be found by going to Google for "NASA Te= chnical
> Paper 1865".
> >
> >I have not taken t= he time to reverse engineer the CG range of the
> LNC2 but let
&= gt; >me offer some observations.
> >
> >The airfoil = used has long been touted as "the greatest thing
> since sliced brea= d"
> >for General Aviation and it definitely has some advantages.= But
> it's not new.
> >Compare this airfoil to the P-51 a= irfoil and you will see some
> close
> >similarities. The = LNC2 being composite construction instead of
> aluminum lets the > >airfoil show more of it's theoretical advantages.
> > <= BR>> >It's a laminar shape with a good drag bucket. That bucket can b= e
> made to move to
> >the lower Cl (lift coefficient) ran= ges with reflex allowing
> noticeably lower
> >drag at higher cruise speeds. Along with reflex, the Cm (moment
> coeffi= cient)
> >goes positive, the center of lift of the wing travels f= orward
> giving a nose up
> >force requiring down trim. Th= is is in addition to the usual nose
> up force that
> >goe= s with most all airfoils at high speed before considering flaps.
&= gt; >
> >With down flap, the drag bucket will move to higher C= l's making
> slower flight
> >more efficient. And, of cour= se, the Cm goes negative giving a
> nose down force
> >req= uiring up trim.
> >
> >. . . and appropriate variations= in-between . . .
> >
> >
> >So, the rear CG = limit is determined by high speed flight and
> available control > >authority,
> >and the forward CG is determined by low s= peed / landing flight
> and available
> >control authority.
> >
> >What is becoming clear here is that = the center of lift does quite
> a bit of
> >traveling fore= and aft which is exaggerated by allowing negative
> or "cruise" > >flaps. Since you can't shift the CG during flight, you need a > large amount of
> >pitch authority from the tail to cover t= hat range of lift travel.
> > 
> >You have two cho= ices in the LNC2, live with the limitations or
> install a larger > >tail to give that extra pitch authority.
> >. . . A la= rger tail area can also help with abnormal
> attitude reco= very.>
> >Wolfgang
> >
>
>
>&nb= sp;    

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