X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 16 Aug 2007 21:40:53 -0400 Message-ID: X-Original-Return-Path: Received: from mis005-2.exch005intermedia.net ([64.78.61.113] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTP id 2267610 for lml@lancaironline.net; Thu, 16 Aug 2007 21:34:53 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.78.61.113; envelope-from=johnwcox@pacificnw.com Received: from ehost005-2.exch005intermedia.net ([64.78.21.103]) by mis005-2.exch005intermedia.net with Microsoft SMTPSVC(6.0.3790.3959); Thu, 16 Aug 2007 18:34:17 -0700 X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C7E06E.B05E3FF6" Subject: RE: [LML] Re: Apologies to the farmer's daughter X-Original-Date: Thu, 16 Aug 2007 18:34:01 -0700 X-Original-Message-ID: In-Reply-To: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [LML] Re: Apologies to the farmer's daughter Thread-Index: AcfgbK7/QERg+U/HS+2piI3BqPRkogAAZBEA References: From: "John W. Cox" X-Original-To: "Lancair Mailing List" X-Original-Return-Path: johnwcox@pacificnw.com X-OriginalArrivalTime: 17 Aug 2007 01:34:17.0411 (UTC) FILETIME=[B9F36930:01C7E06E] This is a multi-part message in MIME format. ------_=_NextPart_001_01C7E06E.B05E3FF6 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable As a former DPE who used to test Terminal Velocity Descent to students of Commercial LTA certificates, I can attest that the rate can range from 700 fp minute to as much as 1300 fp minute. If the canopy streamers then all bets are off after 1500 fp minute =3D 25fps. I had = one applicant ask what would happen if....., and only quick action saved both our lives. =20 The FAA no longer allows Terminal Velocity Descent maneuvers. Something about Old Bold Pilots. =20 John Cox =20 ________________________________ From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Mark Sletten Sent: Thursday, August 16, 2007 6:19 PM To: lml@lancaironline.net Subject: [LML] Re: Apologies to the farmer's daughter =20 =20 =20 I believe the analogy describing the impact by referring to falling or jumping from a particular height doesn't account for the attitude of a BRS-equipped aircraft on impact with the ground following chute deployment. Since the aircraft descends in a nose-low attitude, the nose hits first (assuming level ground) absorbing a great deal of the impact energy -- the rest of the airframe would rotate downwards behind the nose until coming to rest (upright hopefully). Assuming the main gear hits after the nose, this would dissipate even more energy as it (the landing gear) is designed to absorb landing energies. =20 In short, landing under a BRS would be more like two smaller impacts instead of a single large one. =20 During jump training in the USAF we learned to do the same thing with our bodies; the Air Force calls it a Parachute Landing Fall - I don't know what the other services call it. Essentially you land into the wind - feet first - then roll forward while rotating your body so as to dissipate the impact energy. Instead of keeping your feet and legs rigid so as to absorb the full impact - as the Cirrus would if it pancaked flat onto the ground - you roll sideways allowing your knees, hips and shoulders to take their share of the beating. If done properly, one can easily jump from 8 feet without (permanent) injury. =20 Mark =20 ________________________________ From: rtitsworth [mailto:rtitsworth@mindspring.com]=20 Sent: Wednesday, August 15, 2007 5:47 PM To: lml@lancaironline.net Subject: RE: [LML] Apologies to the farmer's daughter =20 Rob, etal, =20 FYI: 25fps ~=3D 17 mph. About like running (full sprint) into solid wall. Perhaps survivable, by OUCH. =20 More math... Gravitational acceleration is approx 32ft/sec^2 (drag-less freefall at the Earth's surface) Doing some algebra to solve for the time to reach 25 fps results in: (25/32)^.5 =3D 0.88 seconds Doing some integral calculus (not shown) results in a distance traveled of approx 7.5 feet Thus, 25 f/s is about the impact speed from falling off the top step of an 8' step ladder Be careful when cleaning your gutters out there :-) =20 Or another analogy (in case you haven;t fallen off the top of a 8' step ladder lately), terminal velocity from the top of a 34" bar stool would be approximately 12.5 fps (note: 1/2 speed =3D 1/4 of the impact = energy). =20 Rick =20 ------_=_NextPart_001_01C7E06E.B05E3FF6 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

As a former DPE who used to test = Terminal Velocity Descent to students of Commercial LTA certificates, I can = attest that the rate can range from 700 fp minute to as much as 1300 fp = minute.  If the canopy streamers then all bets are off after 1500 fp minute =3D = 25fps.  I had one applicant ask what would happen if….., and only quick = action saved both our lives.

 

The FAA no longer allows Terminal = Velocity Descent maneuvers.  Something about Old Bold = Pilots.

 

John Cox

 

From: Lancair Mailing List = [mailto:lml@lancaironline.net] On = Behalf Of Mark Sletten
Sent: Thursday, August = 16, 2007 6:19 PM
To: = lml@lancaironline.net
Subject: [LML] Re: = Apologies to the farmer's daughter

 

 

 

I believe the analogy describing the impact = by referring to falling or jumping from a particular height doesn’t = account for the attitude of a BRS-equipped aircraft on impact with the ground = following chute deployment. Since the aircraft descends in a nose-low attitude, = the nose hits first (assuming level ground) absorbing a great deal of the impact = energy -- the rest of the airframe would rotate downwards behind the nose until = coming to rest (upright hopefully). Assuming the main gear hits after the nose, = this would dissipate even more energy as it (the landing gear) is designed to = absorb landing energies.

 

In short, landing under a BRS would be more = like two smaller impacts instead of a single large one.

 

During jump training in the USAF we learned = to do the same thing with our bodies; the Air Force calls it a Parachute Landing = Fall – I don’t know what the other services call it. Essentially = you land into the wind – feet first – then roll forward while = rotating your body so as to dissipate the impact energy. Instead of keeping your = feet and legs rigid so as to absorb the full impact – as the Cirrus = would if it pancaked flat onto the ground – you roll sideways allowing your = knees, hips and shoulders to take their share of the beating. If done properly, = one can easily jump from 8 feet without (permanent) = injury.

 

Mark

 

From: rtitsworth [mailto:rtitsworth@mindspring.com]
Sent: Wednesday, August = 15, 2007 5:47 PM
To: = lml@lancaironline.net
Subject: RE: [LML] = Apologies to the farmer's daughter

 

Rob, = etal,

 

FYI:  25fps = ~=3D 17 mph.  About like running (full sprint) into solid wall. =  Perhaps survivable, by OUCH.

 

More = math…

Gravitational acceleration is approx 32ft/sec^2 (drag-less freefall at the = Earth’s surface)

Doing some = algebra to solve for the time to reach 25 fps results in:  (25/32)^.5 =3D 0.88 = seconds

Doing some = integral calculus (not shown) results in a distance traveled of approx 7.5 = feet

Thus, 25 f/s is = about the impact speed from falling off the top step of an 8’ step = ladder

Be careful when = cleaning your gutters out there J

 

Or another = analogy (in case you haven;t fallen off the top of a 8’ step ladder lately), = terminal velocity from the top of a 34” bar stool would be approximately = 12.5 fps (note: 1/2 speed =3D 1/4 of the impact energy).

 

Rick

 

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