Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Mon, 10 Jan 2005 20:38:20 -0500 Message-ID: X-Original-Return-Path: Received: from wind.imbris.com ([216.18.130.7] verified) by logan.com (CommuniGate Pro SMTP 4.2.8) with ESMTP-TLS id 602163 for lml@lancaironline.net; Mon, 10 Jan 2005 13:54:22 -0500 Received-SPF: none receiver=logan.com; client-ip=216.18.130.7; envelope-from=brent@regandesigns.com Received: from [192.168.1.100] (wireless-216-18-135-19.imbris.com [216.18.135.19]) (authenticated bits=0) by wind.imbris.com (8.12.11/8.12.11) with ESMTP id j0AIs1JG094319 for ; Mon, 10 Jan 2005 10:54:02 -0800 (PST) (envelope-from brent@regandesigns.com) X-Original-Message-ID: <41E2CF45.2050306@regandesigns.com> Disposition-Notification-To: Brent Regan X-Original-Date: Mon, 10 Jan 2005 10:53:57 -0800 From: Brent Regan User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 X-Original-To: Lancair Mailing List Subject: Re: Approved Weights for Lancair IVP/IVPTs? Content-Type: multipart/alternative; boundary="------------090000040502040100000007" X-Virus-Scanned: ClamAV 0.80/659/Sun Jan 9 20:21:09 2005 clamav-milter version 0.80j on wind.imbris.com X-Virus-Status: Clean This is a multi-part message in MIME format. --------------090000040502040100000007 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Lynn writes " All one had to do was pay more money to get the higher weight limit. Flying at either weight was safe " Lynn's comments underscore the general misunderstanding about gross weight. Every pound of cargo (extra fuel, passengers, baggage) you load into an airplane makes that plane less safe. Part of the confusion is due to the way an airframe is rated for load in Gs. Wing spars are tested at a certain load and then this load is converted into G's assuming a given gross weight. Increase the gross weight and the wings break off at a lower G load. Given enough horsepower, the correct CG and a long enough runway you could load a IV-p to 28,500 pounds and it would still fly, that is until you pulled back on the stick and saw 1.05 Gs, at which point the plane would get lighter by two wings. It is interesting to note that the stall speed would equal Va at this load and the takeoff speed would exceed the flap and gear deployment speeds. Recently a well loaded IV entered a thunderstorm and fell out the bottom in pieces. Had the plane been lightly loaded or flying below Va this may not have happened. Once you exceed Va, the safety margin is a function of load. More weight, less margin, so while "either weight" may be safe, the lighter weight is safer. Using a higher gross weight does NOT increase the airplanes ultimate load capability. Increasing the gross weight from 2,900 to 3,550 decreases the ultimate G load capacity from 8.8 to 7.2. Weight also increases stall speed, with the attendant bad consequences. Weight also decreases speed, also bad. So, increasing load decreases safety, and we have already seen at least one case of an in-flight structural failure. Unless you laminate the airworthyness certificate to the extreme fiber of the wing it will have NO effect on the ultimate strength of the aircraft. The arbitrary, progressive increases in gross weight will eventually end in death, possibly yours. Engineering lore is fraught with incremental increases that eventually fail catastrophically (e.g. Tacoma Narrows Bridge). It is a pattern and habit that must be resisted even if that resistance is characterized as hysterical by some. Is that enough "information"? Regards Brent Regan --------------090000040502040100000007 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Lynn writes " All one had to do was pay more money to get the higher weight limit. Flying at either weight was safe "

Lynn's comments underscore the general misunderstanding about gross weight. Every pound of cargo (extra fuel, passengers, baggage)  you load into an airplane makes that plane less safe.  Part of the confusion is due to the way an airframe is rated for load in Gs. Wing spars are tested at a certain load and then this load  is converted into G's assuming a given gross weight. Increase the gross weight  and the wings break off at a lower G load.

Given enough horsepower, the correct CG and a long enough runway you could load a IV-p to 28,500 pounds and it would still fly, that is until you pulled back on the stick and saw 1.05 Gs, at which point the plane would get lighter by two wings. It is interesting to note that the stall speed would equal Va at this load and the takeoff speed would exceed  the flap and gear deployment speeds.

Recently a well loaded IV entered a thunderstorm and fell out the bottom in pieces. Had the plane been lightly loaded or flying below Va this may not have happened. Once you exceed Va, the safety margin is a function of load. More weight, less margin, so while "either weight" may be safe, the lighter weight is safer. Using a higher gross weight does NOT increase the airplanes ultimate load capability. Increasing the gross weight from 2,900 to 3,550 decreases the ultimate G load capacity from 8.8 to 7.2.

Weight also increases stall speed, with the attendant bad consequences. Weight also decreases speed, also bad.

So, increasing load decreases safety, and we have already seen at least one case of an in-flight structural failure.  Unless you laminate the airworthyness certificate to the extreme fiber of the wing it will have NO effect on the ultimate strength of the aircraft. The arbitrary, progressive increases in gross weight will eventually end in death, possibly yours. Engineering lore is fraught with incremental increases that eventually fail catastrophically (e.g. Tacoma Narrows Bridge). It is a pattern and habit that must be resisted even if that resistance is characterized as hysterical by some.

Is that enough "information"?

Regards
Brent Regan


 --------------090000040502040100000007--