X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 05 Aug 2011 10:37:37 -0400 Message-ID: X-Original-Return-Path: Received: from imr-ma01.mx.aol.com ([64.12.206.39] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTP id 5081785 for lml@lancaironline.net; Thu, 04 Aug 2011 10:15:50 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.39; envelope-from=Sky2high@aol.com Received: from mtaomg-ma03.r1000.mx.aol.com (mtaomg-ma03.r1000.mx.aol.com [172.29.41.10]) by imr-ma01.mx.aol.com (8.14.1/8.14.1) with ESMTP id p74EF8Nf032623 for ; Thu, 4 Aug 2011 10:15:08 -0400 Received: from core-mta003b.r1000.mail.aol.com (core-mta003.r1000.mail.aol.com [172.29.234.137]) by mtaomg-ma03.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 241FEE000082 for ; Thu, 4 Aug 2011 10:15:08 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: <9ef57.46e3d07c.3b6c036b@aol.com> X-Original-Date: Thu, 4 Aug 2011 10:15:08 -0400 (EDT) Subject: Re: [LML] Re: Newbie: Help with Weight & Balance X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_9ef57.46e3d07c.3b6c036b_boundary" X-Mailer: AOL 9.6 sub 5004 X-AOL-IP: 24.15.17.119 X-Originating-IP: [24.15.17.119] x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:511763488:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d290a4e3aa96c77f9 --part1_9ef57.46e3d07c.3b6c036b_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en One more point. Reference measurements must be taken with the airplane=20 longitudinally level and are frequently accomplished by dropping a plumb b= ob=20 from the desired point and marking the floor. This includes the center of= =20 each wheel axle. The plane should also be similarly level for weight=20 measurements for concordance. =20 =20 If one must use only positive numbers, it is useful to use the rear of the = =20 spinner (easier to hold the plumb still). Then, the firewall reference=20 adjustment to the one used by Lancair for W&B CG calculations can be made.= =20 Note that in the 320/360 series, the back (aft side) of the firewall is th= e=20 final reference point. =20 Finally, make sure doors/canopies are closed when weighing the aircraft =20 (just like in level flight). In the 320/360 series the mains don't change = =20 the weight whether extended or not (they fold in with no change fwd or aft)= , =20 however the retracted nose gear slightly moves the weight aft. Lancair =20 should have taken that into account when publishing the CG limits. On the = IV,=20 all landing gear moves the weight rearward when retracted - again, Lancair = =20 should have taken that into consideration when publishing the CG limits for= =20 level aircraft weighed on the landing gear. =20 Grayhawk =20 =20 =20 In a message dated 8/4/2011 8:42:24 A.M. Central Daylight Time, =20 marv@lancair.net writes: Posted for "Bill Harrelson" : Hello Dico, Perhaps I can help a bit on some of your W&B questions. 1. The =E2=80=9Cbottom front of firewall=E2=80=9D is nothing more than a s= tarting point=20 for =20 determining where the factory recommended datum is located. The factory =20 recommended datum is the tip of the spinner but since you and I may be =20 using=20 different engines, props and spinners, we=E2=80=99d be calculating from di= fferent=20 points. By computing the datum as 51.25 inches forward of the bottom front= =20 of=20 the firewall we can assure that we=E2=80=99re all measuring our stations r= elative=20 to=20 the same datum (reference plane). There is something wrong with the data= =20 that=20 you are using in your spreadsheet. It looks to me like the datum has been= =20 moved forward 12.625 inches from the factory recommended point yet the=20 arms=20 and CG limits remain the same as factory recommended. Is this spreadsheet= =20 for=20 a turbine where the spinner has been moved forward? If this is the case=20 you=20 have two choices. 1. Use the factory recommended datum, 51.25 inches=20 forward=20 of the bottom front of the firewall or 2. Change your datum to the tip of= =20 YOUR=20 spinner (or any other point that you choose) in which case you MUST adjust= =20 all=20 of your other arms and and balance limits to reflect a reference to this= =20 new =20 datum. =20 2. The =E2=80=9Cmains retracted=E2=80=9D number of 1088 seems to represent= the change in=20 moment (weight x distance) caused by retracting the main gear. I have no= =20 idea=20 why the nose wheel is not similarly accounted for. This moment change is= =20 based=20 on the factory datum. 3. MAC is Mean Aerodynamic Chord. Notice that the =E2=80=9CLE of MAC=E2=80= =9D sometimes=20 simply referred to as LEMAC is listed as 95.125. This means that the=20 Leading=20 Edge of the Mean Aerodynamic Chord is located 95 1/8 inches aft of the=20 datum.=20 =E2=80=9CMAC is 40=E2=80=9D long=E2=80=9D figure is given, which tells us = that the MAC extends=20 from=20 95.125 inches aft of the datum to 135.125 inches aft of the datum (TEMAC).= =20 A=20 balance envelope is commonly defined in terms of =E2=80=9Cpercentage of MA= C=E2=80=9D. =20 The=20 advantage of stating the balance calculation in terms of %MAC is that it= =20 is=20 very similar for any conventional airplane regardless of weight or size.= =20 For =20 example, if you calculated the %MAC to be 20 you=E2=80=99d be in the envelo= pe, at =20 least as far as balance, in a Luscombe, a Lancair or a Lockheed. A %MAC of = =20 50=20 would put you far aft of the balance limits whether you are talking about= =20 a=20 Birddog, a Beech or a Boeing. Again, there is a problem with your =20 spreadsheet=20 as it seems to be referenced to a new datum without changing all of the=20 arms=20 to refer to this new datum. The %MAC limits simply do not agree with the= =20 FS=20 limits (86.5 =E2=80=93 94.5) in your spreadsheet. 4. =E2=80=9CWing LE @ BL25.5 =3D 93.875=E2=80=9D is simply a reference poi= nt that may or=20 may=20 not be useful to you in determining the location of various =E2=80=9Cstati= ons=E2=80=9D or=20 points at which weight is applied. In this case it tells us that at 25 1/2= =20 inches from the aircraft centerline (butt line or BL) the leading edge of= =20 the=20 wing is located 93.875 inches aft of the datum. I believe that it=E2=80=99= s fairly=20 safe to assume that we all have our wings mounted at the same location on= =20 the=20 fuselage. I am not sure, however, which datum that this number is=20 referenced =20 from. I urge you to examine your basic W&B numbers carefully and determine what= =20 you=20 want to use as a datum. Once you make that decision, make sure that ALL=20 arms=20 and limits are referenced to that datum. You cannot use factory arms and= =20 limits unless you are referencing the factory datum. =20 In my days as an examiner I would often notice a smile on the applicants= =20 face=20 when I asked for a W&B calculation. =E2=80=9CHere=E2=80=99s an easy one, j= ust a few=20 fourth=20 grade arithmetic calculations and I=E2=80=99ll have the answer=E2=80=9D. R= arely would=20 someone=20 be unable to compute this correctly. The smile would sometimes disappear= =20 when =20 I probed a little further and asked =E2=80=9Cso what?, why do we care?=E2= =80=9D It was a =20 rare=20 applicant who could correctly explain the stability and performance =20 tradeoffs=20 that define the balance limits.=20 Bill Harrelson N5ZQ 320 1,950 hrs N6ZQ IV under construction [I concur, everything Bill says is right on. If you're going to use the= =20 spreadsheet from the LML website (prepared for N540TF) you absolutely MUST= =20 plug in your own stations measured from your aircraft. Since you can't=20 physically measure things like the center of mass for the pilot, passenger= s,=20 and baggage compartment, you can deduct the station for "bottom front of= =20 firewall" from the ones shown on that spreadsheet to determine their respe= ctive=20 deltas, then add those deltas back onto your "bottom front of firewall"=20 station to determine their real stations for your aircraft. You can't=20 shortcut physically measuring the bottom front of firewall (even though it= 's not=20 directly used in the spreadsheet, it's a critical dimension in the grand= =20 scheme of things) and the axle C/L's for the gear. Once your basic number= s=20 are correct the spreadsheet should operate as intended for your aircraft. = =20 ] From: Dico Reijers=20 Sent: Sunday, July 31, 2011 12:07 PM To: lml@lancaironline.net=20 Subject: [LML] Newbie: Help with Weight & Balance Hi All, I'm a newbie LNC4 owner and am just getting familiar with the airplane and= =20 have a couple questions regarding the weight and balance. I used the sample spreadsheet (from Lancair Online's web site) and plugged= =20 in=20 the #s from my weight and balance. The numbers calculated by the spread= =20 sheet=20 are pretty much exacly the same as per my weight and balance, however=20 there=20 are some numbers included in the sample W&B spreadsheet that are "greek"= =20 to me =20 (the areas in red in the PDF link below). I am hoping someone can help me= =20 out I posted a link to my W&B here: http://www.cavendishcorner.com/fqqq.pdf 1.. The "bottom front of firewall" number seems to do nothing to the =20 calculations. Where does this number come from?=20 2.. The "mains retracted" number of 1088... is this the same for all=20 IV-Ps? =20 Adjusting that number does make a difference on the calculations, however= =20 that 1088 seems to make the numbers pretty much match my current W&B. =20 Perhaps=20 just a coincedence.=20 3.. "MAC is 40 inches long".... what does this mean? =20 4.. Wing LE @ BL25.5 =3D 93.875..... what does this mean? Changing this = =20 number changes the percentage outlined in red so I should use a number =20 related=20 to my serial#. My weight and balance is located here:=20 http://www.cavendishcorner.com/fqqq-2.pdf My FS limits are from 86.5 to 94.5 --- how is this range determined? Thanks for any help! -Dico Reijers Lancair IV-P #428 -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html --part1_9ef57.46e3d07c.3b6c036b_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
One more point.  Reference measurements must be taken with t= he=20 airplane longitudinally level and are frequently accomplished by dropping a= =20 plumb bob from the desired point and marking the floor.  This inc= ludes=20 the center of each wheel axle.  The plane should also be similarly lev= el=20 for weight measurements for concordance. 
 
If one must use only positive numbers, it is useful to use the rear of= the=20 spinner (easier to hold the plumb still).  Then, the=20 firewall reference adjustment to the one used by Lancair for W&B C= G=20 calculations can be made.  Note that in the 320/360 series, the back (= aft=20 side) of the firewall is the final reference point.
 
Finally, make sure doors/canopies are closed when weighing the aircraf= t=20 (just like in level flight).  In the 320/360 series the mains don't ch= ange=20 the weight whether extended or not (they fold in with no change fwd or aft)= ,=20 however the retracted nose gear slightly moves the weight aft. Lancair= =20 should have taken that into account when publishing the CG limits.  On= the=20 IV, all landing gear moves the weight rearward when retracted - again, Lanc= air=20 should have taken that into consideration when publishing the CG limits for= =20 level aircraft weighed on the landing gear.
 
Grayhawk
 
 
In a message dated 8/4/2011 8:42:24 A.M. Central Daylight Time,=20 marv@lancair.net writes:
=
Posted for "Bill Harrelson"=20 <n5zq@verizon.net>:

 Hello Dico,
 
 Per= haps=20 I can help a bit on some of your W&B questions.
 
 1.= The=20 =E2=80=9Cbottom front of firewall=E2=80=9D is nothing more than a startin= g point for=20
determining where the factory recommended datum is located. The facto= ry=20
recommended datum is the tip of the spinner but since you and I may b= e=20 using
different engines, props and spinners, we=E2=80=99d be calculat= ing from=20 different
points. By computing the datum as 51.25 inches forward of t= he=20 bottom front of
the firewall we can assure that we=E2=80=99re all mea= suring our=20 stations relative to
the same datum (reference plane). There is somet= hing=20 wrong with the data that
you are using in your spreadsheet. It looks = to me=20 like the datum has been
moved forward 12.625 inches from the factory= =20 recommended point yet the arms
and CG limits remain the same as facto= ry=20 recommended. Is this spreadsheet for
a turbine where the spinner has = been=20 moved forward? If this is the case you
have two choices. 1. Use the= =20 factory recommended datum, 51.25 inches forward
of the bottom front o= f the=20 firewall or 2. Change your datum to the tip of YOUR
spinner (or any o= ther=20 point that you choose) in which case you MUST adjust all
of your othe= r=20 arms and and balance limits to reflect a reference to this new=20
datum.  
 
 2. The =E2=80=9Cmains retracted= =E2=80=9D number of=20 1088 seems to represent the change in
moment (weight x distance) caus= ed by=20 retracting the main gear. I have no idea
why the nose wheel is not=20 similarly accounted for. This moment change is based
on the factory= =20 datum.
 
 3. MAC is Mean Aerodynamic Chord. Notice that t= he=20 =E2=80=9CLE of MAC=E2=80=9D sometimes
simply referred to as LEMAC is = listed as 95.125.=20 This means that the Leading
Edge of the Mean Aerodynamic Chord is loc= ated=20 95 1/8 inches aft of the datum.
 =E2=80=9CMAC is 40=E2=80=9D lon= g=E2=80=9D figure is given,=20 which tells us that the MAC extends from
95.125 inches aft of the dat= um to=20 135.125 inches aft of the datum (TEMAC). A
balance envelope is common= ly=20 defined in terms of =E2=80=9Cpercentage of MAC=E2=80=9D.   The =
advantage of=20 stating the balance calculation in terms of %MAC is that it is
very= =20 similar for any conventional airplane regardless of weight or size. For= =20
example, if you calculated the %MAC to be 20 you=E2=80=99d be in the = envelope, at=20
least as far as balance, in a Luscombe, a Lancair or a Lockheed. A %M= AC of=20 50
would put you far aft of the balance limits whether you are talkin= g=20 about a
Birddog, a Beech or a Boeing. Again, there is a problem with = your=20 spreadsheet
as it seems to be referenced to a new datum without chang= ing=20 all of the arms
to refer to this new datum. The %MAC limits simply do= not=20 agree with the FS
limits (86.5 =E2=80=93 94.5) in your=20 spreadsheet.
 
 4. =E2=80=9CWing LE @ BL25.5 =3D 93.875= =E2=80=9D is simply a=20 reference point that may or may
not be useful to you in determining t= he=20 location of various =E2=80=9Cstations=E2=80=9D or
points at which wei= ght is applied. In=20 this case it tells us that at 25 1/2
inches from the aircraft centerl= ine=20 (butt line or BL) the leading edge of the
wing is located 93.875 inch= es=20 aft of the datum. I believe that it=E2=80=99s fairly
safe to assume t= hat we all=20 have our wings mounted at the same location on the
fuselage. I am not= =20 sure, however, which datum that this number is referenced=20
from.
 
 I urge you to examine your basic W&B num= bers=20 carefully and determine what you
want to use as a datum. Once you mak= e=20 that decision, make sure that ALL arms
and limits are referenced to t= hat=20 datum. You cannot use factory arms and
limits unless you are referenc= ing=20 the factory datum.  
 
 In my days as an examin= er I=20 would often notice a smile on the applicants face
when I asked for a= =20 W&B calculation. =E2=80=9CHere=E2=80=99s an easy one, just a few four= th
grade=20 arithmetic calculations and I=E2=80=99ll have the answer=E2=80=9D. Rarely= would someone
be=20 unable to compute this correctly. The smile would sometimes disappear whe= n=20
I probed a little further and asked =E2=80=9Cso what?, why do we care= ?=E2=80=9D It was a=20 rare
applicant who could correctly explain the stability and performa= nce=20 tradeoffs
that define the balance limits.
 
 Bill=20 Harrelson
 N5ZQ 320 1,950 hrs
 N6ZQ  IV under= =20 construction


[I concur, everything Bill says is right on. = ; If=20 you're going to use the spreadsheet from the LML website (prepared for N5= 40TF)=20 you absolutely MUST plug in your own stations measured from your=20 aircraft.  Since you can't physically measure things like the center= of=20 mass for the pilot, passengers, and baggage compartment, you can deduct t= he=20 station for "bottom front of firewall" from the ones shown on that spread= sheet=20 to determine their respective deltas, then add those deltas back onto you= r=20 "bottom front of firewall" station to determine their real stations for y= our=20 aircraft.  You can't shortcut physically measuring the bottom front = of=20 firewall (even though it's not directly used in the spreadsheet, it's a= =20 critical dimension in the grand scheme of things) and the axle C/L's for = the=20 gear.  Once your basic numbers are correct the spreadsheet should op= erate=20 as intended for your aircraft.   <Marv>  =20 ]
 
 
 
From: Dico Reijers
 Sent: Sun= day,=20 July 31, 2011 12:07 PM
 To: lml@lancaironline.net
 Subje= ct:=20 [LML] Newbie: Help with Weight & Balance
 
 Hi=20 All,
 
 I'm a newbie LNC4 owner and am just getting famil= iar=20 with the airplane and
have a couple questions regarding the weight an= d=20 balance.
 
 I used the sample spreadsheet (from Lancair= =20 Online's web site) and plugged in
the #s from my weight and=20 balance.  The numbers calculated by the spread sheet
are pr= etty=20 much exacly the same as per my weight and balance, however there
are = some=20 numbers included in the sample W&B spreadsheet that are "greek" to me= =20
(the areas in red in the PDF link below).  I am hoping some= one=20 can help me out
 
 I posted a link to my W&B=20 here:  =20 http://www.cavendishcorner.com/fqqq.pdf
 
 
  1..= The=20 "bottom front of firewall" number seems to do nothing to the=20
calculations.  Where does this number come from?
 = 2..=20 The "mains retracted" number of 1088... is this the same for all IV-Ps?= =20
 Adjusting that number does make a difference on the calculation= s,=20 however
that 1088 seems to make the numbers pretty much match my curr= ent=20 W&B.  Perhaps
just a coincedence.
  3.. "MAC i= s 40=20 inches long".... what does this mean?  
 
  4..= Wing=20 LE @ BL25.5 =3D 93.875..... what does this mean?  Changing this= =20
number changes the percentage outlined in red so I should use a numbe= r=20 related
to my serial#.
 
 My weight and balance is lo= cated=20 here:
 =20 http://www.cavendishcorner.com/fqqq-2.pdf
 
 
 My= FS=20 limits are from 86.5 to 94.5 --- how is this range=20 determined?
 
 Thanks for any help!
 
 -D= ico=20 Reijers
 
 Lancair IV-P #428

--

For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html=
--part1_9ef57.46e3d07c.3b6c036b_boundary--