Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Thu, 09 Oct 2003 11:52:53 -0400 Message-ID: X-Original-Return-Path: Received: from mail-3.tiscali.it ([195.130.225.149] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2630141 for lml@lancaironline.net; Thu, 09 Oct 2003 11:30:02 -0400 Received: from trottolino (62.11.9.251) by mail-3.tiscali.it (6.7.019) id 3F79B03D006A54E6 for lml@lancaironline.net; Thu, 9 Oct 2003 17:29:59 +0200 X-Original-Message-ID: <007b01c38e7a$caf95cc0$fb090b3e@interbusiness.it> From: "Robert Overmars" X-Original-To: "Lancair Mailing List" Subject: LIV wing strength X-Original-Date: Thu, 9 Oct 2003 17:34:11 +0200 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0078_01C38E8B.8D3A1C60" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 This is a multi-part message in MIME format. ------=_NextPart_000_0078_01C38E8B.8D3A1C60 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Salutti tutti, Finally my copy of Martin Hollman's book Modern Aircraft Design has = arrived. Here's some excerpts that are relevant to the recent LML = discussuion about the LIV wing design and strength and G loads. >From Chapter 4, Loads per 14CFR, Part 23, page 61 paragraphs 2&3. "We must make a decision as to what category our aircraft will be = designed to and we have three categories to pick from. For the normal = category, 14 CFR, Part 23 specifies that the maximum g limit load factor = is 3.8gs. For the utility category 4.4gs is specifed, and for acrobatic, = 6.0gs is required however we have been using 8.75gs in the design of = acrobatic aircraft. Pilots in acrobatic aircraft commonly pull 10gs" The positive limit load factor, n1, is the g load that we design the = aircraft to. It is defined as positive if it is pushing the pilot into = the seat. By the way the Ercoupe and Cessna line of aircraft are = designed to the normal category. If we intend to perform mild maneuvers = such as loops and rolls at gross weight we design to the utlity = category. Most composite aircraft such as the Stallion and Lancair IV = are designed to the normal category with n1 =3D 3.8gs" >From Chapter 10, Wing Structural Testing, page 133, paragraph 1. "In my past literature I have advocated using a safety factor of 2.0. = However since the certification of the Starship in which a safety factor = of 1.5 was used by the FAA, I have been using a safety factor of 1.5. = The practice of using a safety factor of 2.0 comes from the Aerospace = industry which requires a safety factor of 1.33 in addition to a factor = of 1.5. Multiplying 1.33 times 1.5 gives 2.0. The factor of 1.33 is used = to account for such things as temperature effects and is normally = thought of as an ignorance factor. If elevated temperature material = properties have been used a safety factor of 1.5 is considered to be = adequate" (elevated temperature material =3D high temperature cured prepregs such = as wing skins, fuselage mouldings etc) >From Chapter 6, Structural Sizing of a Composite Wing, Table 6.4 Lancair = IV Wing design Data, page 106. "Wing Span =3D 30 feet. Tip chord 30 inches. Root chord =3D 50 inches. = Washout =3D 2.0 degrees. Sweep =3D 0 degrees. Airfoil moment coefficient = =3D -0.05. Spar cap width =3D 5.0 inches. Fuselage to wing BL =3D 25.5. = Limit load factor =3D 4.4 gs. Gross weight less wing weight =3D 2,900 - = 310 =3D 2,590 lbs. Limit flight maneuvering speed , Va @SL=3D 200 mph. = Design dive speed, Vd @ SL =3D 360 mph. Safety factor =3D 1.5 for = ultimate loads. (There's more in this chapter but not relevant for this discussion.) >From Chapter 6, Figure 6.13, page 111. This is an engineering drawing reproduction scaled to fit the page. The = notes in the bottom right hand corner read: Notes: 1) Gross wt =3D 3,000 lbs. Less wing panel wt =3D 160 lbs/panel 2) Limit load factor =3D 4.4 gs, Safety factor 1.5. 3) Vd =3D 360 mph, Va =3D 200 mph 4) (....about adhesives, not relevant)=20 Like the wing area you don't have but always thought you did, now you = know the safety factor is 1.5 ONLY for a max gross weight of 2,900 or = maybe 3,000lbs. Be carefull, be safe, Ciao, Roberto d'Italia. ------=_NextPart_000_0078_01C38E8B.8D3A1C60 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Salutti tutti,
 
Finally my copy of Martin Hollman's = book Modern=20 Aircraft Design has arrived. Here's some excerpts that are relevant to = the=20 recent LML discussuion about the LIV wing design and strength and G loads.
 
From Chapter 4, Loads per 14CFR, Part = 23, page 61=20 paragraphs 2&3.
 
"We must make a decision as to what = category our=20 aircraft will be designed to and we have three categories to pick from. = For the=20 normal category, 14 CFR, Part 23 specifies that the maximum g limit load = factor=20 is 3.8gs. For the utility category 4.4gs is specifed, and for acrobatic, = 6.0gs=20 is required however we have been using 8.75gs in the design of acrobatic = aircraft. Pilots in acrobatic aircraft commonly pull 10gs"
 
The positive limit load factor, n1, is = the g load=20 that we design the aircraft to. It is defined as positive if it is = pushing the=20 pilot into the seat. By the way the Ercoupe and Cessna line of aircraft = are=20 designed to the normal category. If we intend to perform mild maneuvers = such as=20 loops and rolls at gross weight we design to the utlity category. Most = composite=20 aircraft such as the Stallion and Lancair IV are designed to the normal = category=20 with n1 =3D 3.8gs"
 
 
From Chapter 10, Wing Structural = Testing, page 133,=20 paragraph 1.
 
"In my past literature I have advocated = using a=20 safety factor of 2.0. However since the certification of the Starship in = which a=20 safety factor of 1.5 was used by the FAA, I have been using a safety = factor of=20 1.5. The practice of using a safety factor of 2.0 comes from the = Aerospace=20 industry which requires a safety factor of 1.33 in addition to a factor = of 1.5.=20 Multiplying 1.33 times 1.5 gives 2.0. The factor of 1.33 is used to = account for=20 such things as temperature effects and is normally thought of as an = ignorance=20 factor. If elevated temperature material properties have been used a = safety=20 factor of 1.5 is considered to be adequate"
(elevated temperature material =3D = high=20 temperature cured prepregs such as wing skins, fuselage mouldings=20 etc)
 
From Chapter 6, Structural Sizing of a = Composite=20 Wing, Table 6.4 Lancair IV Wing design Data, page 106.
 
"Wing Span =3D 30 feet.  Tip chord = 30 inches.=20 Root chord =3D 50 inches. Washout =3D 2.0 degrees. Sweep =3D 0 degrees. = Airfoil moment=20 coefficient =3D -0.05. Spar cap width =3D 5.0 inches.  = Fuselage to wing BL=20 =3D 25.5.  Limit load factor =3D 4.4 gs. Gross weight less wing = weight =3D 2,900=20 - 310 =3D 2,590 lbs. Limit flight maneuvering speed , Va @SL=3D 200 = mph. =20 Design dive speed, Vd @ SL =3D 360 mph.  Safety factor =3D 1.5 for = ultimate=20 loads.
(There's more in this chapter but not = relevant for=20 this discussion.)
 
From Chapter 6, Figure 6.13, page = 111.
 
This is an engineering drawing = reproduction scaled=20 to fit the page. The notes in the bottom right hand corner = read:
 
Notes:
1)  Gross wt =3D 3,000 lbs. Less = wing panel wt =3D=20 160 lbs/panel
2) Limit load factor =3D 4.4 gs, Safety = factor=20 1.5.
3) Vd =3D 360 mph, Va =3D 200 = mph
4)  (....about adhesives, not=20 relevant) 
 
 
Like the wing area you don't have but = always=20 thought you did, now you know the safety factor is 1.5 ONLY for a max = gross=20 weight of 2,900 or maybe 3,000lbs.
 
Be carefull, be safe,
 
Ciao,
 
Roberto d'Italia.
 
 
 
 
 
 
 
 
 
 
 
 
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