X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 31 Jan 2010 23:58:12 -0500 Message-ID: X-Original-Return-Path: Received: from web36902.mail.mud.yahoo.com ([209.191.85.70] verified) by logan.com (CommuniGate Pro SMTP 5.3.2) with SMTP id 4105798 for lml@lancaironline.net; Sun, 31 Jan 2010 11:27:15 -0500 Received-SPF: none receiver=logan.com; client-ip=209.191.85.70; envelope-from=chris_zavatson@yahoo.com Received: (qmail 1318 invoked by uid 60001); 31 Jan 2010 16:26:38 -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=S0zZU8W0gpkPeMeWB3SLfic4UHEYx2SI47jl2/uWsmT6TmlKNDkdJS1uJwPwavAQrX+OM7+G0gScMUjhgVSOwnDSJgL9RVAPHgsT2Oakb2M3KULCQ3BiSpsL85hfCi8ySO+ZKRR/V6130hWt/uGjyqh0Q+CvUzIHPwwu/bwf/LE=; X-Original-Message-ID: <308898.931.qm@web36902.mail.mud.yahoo.com> X-YMail-OSG: 9lvzg.4VM1kGA7CnNXyzDpR4k2s0qV_E5_jbbcvX9P9tF9u0xskFIdmbVhLa8JjtBGUpdOQzBBYYU_p9.AeiojaWVeFHfPKdGEzGhqX7om2TFeD8oe0kYtVFcG6jKrKC8vEhHgYEmgY56eMrhX0axrMMy4vmmxN1gBRfXkr_UZcG5jr6dBoYpKXYmLe33rP9Sx19.feKY5.WFLEpyNwCLAk3.J.hsNyMAKE8ExnOVgaqYv0Ps_zcTuh29K6Jj5YjT7pCPUND0i2ZEUCo4fxKe4uOfJ0ZIlwbjBjYYeDyR3iQmjAaPe4B32WxeIDkaJAZqBc363rOTCGBdlHbQESUMCcRwnlbHg5NzXEeTYNXXiHb60ePNgP_xS7v0NCJRYl8dogUiGfk2Ox.1H3xCMEIYKt8IpthznxQQQzyh.0sDBMyboItqvjsqoEQ Received: from [76.246.35.42] by web36902.mail.mud.yahoo.com via HTTP; Sun, 31 Jan 2010 08:26:38 PST X-Mailer: YahooMailRC/272.7 YahooMailWebService/0.8.100.260964 References: X-Original-Date: Sun, 31 Jan 2010 08:26:38 -0800 (PST) From: Chris Zavatson Subject: Re: [LML] Re: Engine out gear down Issue/The procedure! This was a wake up call for me.. X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1559056293-1264955198=:931" --0-1559056293-1264955198=:931 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable After this discussion I coded some calculation done years ago when a simila= r thread was discussed.=A0 The results show vertical and forward speed over= time given a number of inputs like weight, initial steady state descent ra= te, initial approach speed, and a bunch of aircraft specific parameters lik= e wing area, aspect ratio,etc.=A0 One parameter that turned out to be a big= player was how much of the remaining lift available was used during the fl= are.=A0 That is, hard do you pull back on the stick.=A0 40% seemed to make = the landing profile from a steep descent look right in terms of duration of= the round-out based on observing typical landings.=A0 It is however a vari= able that can make or break a landing.=A0 It stretches or compresses the ti= me in the flare significantly and thus allows more or less decay in air spe= ed.=A0 Induced drag changes were less pronounced than expected, especially = when only using 40% of the available margin to stall.=A0 This is reduced further in ground effect.=0AA typical steep (1,500 fpm) power off flare=A0= is showing a 15 kt decay in airspeed whereas the transition from a 3 degree= ILS (500 fpm) only cost=A03 kts.=A0 The amount deacy is strongly tied to i= nitial speed.=A0 At a higher initial speed the decay is less than for the s= ame approach at a lower speed.=A0 For example a steep approach case entered= at 80 kts lost 18=A0KIAS while the same profile entered at 90 KIAS lost on= ly 9 kts. =A0That makes sense given energy being a squared function of spee= d.=A0 A little more speed gets you a lot more energy.=0A=0AChris Zavatson= =0AN91CZ=0A360std=0Awww.N91CZ.com=0A=0A=0A=0A=0A=0A________________________= ________=0AFrom: Gary Casey =0ATo: lml@lancaironline.= net=0ASent: Sun, January 31, 2010 6:57:44 AM=0ASubject: [LML] Re: Engine ou= t gear down Issue/The procedure! This was a wake up call for me..=0A=0A=0AI= ran through some numbers regarding Michael's comments below. =A0Starting w= ith the sailplane comment, he says that slowing from 135kts to 65 in a zoom= can result in a gain of 800 feet. =A0If all the energy were converted to a= ltitude(no drag) the gain would be 1,276 ft, so a gain of 800 ft seems reas= onable for a very low-drag airframe - 2/3 of the energy can be converted to= altitude. =A0In the case mentioned of 120 kts to 75 kts the number comes o= ut to a gain of 765 ft. =A0How much of that is eaten up by drag? =A0Certain= ly compared to the sailplane, a lot. =A0Would the altitude gain be half? = =A0I doubt it. =A01/4? =A0Maybe, so as a guess you could count on perhaps a= 200 ft altitude gain. =A0How much do you need to flare? =A0Depends on the = descent rate. =A0I calculated it based on 2,000 ft/min - arresting that is = equivalent to an altitude gain of 34.5 ft, much lower than the 200 ft menti= oned above. =A0It would be good if someone measured the actual no-power des= cent rate with gear and flaps down.=0A=0AIn summary, the math suggests that a n= o-power approach speed of 120 kts should leave more than enough energy to f= lare. =A0How much more? =A0I'll bet not a lot, but still more. =A0I don't h= ave an answer to the question, but this is how the numbers work out. =A0I h= ave done a full-flap no-power descent with my ES (gear down, of course :-) = at 105 kts and the descent rate was over 2,000 ft/min with a frighteningly = high negative deck angle. =A0Flaring from that condition would be interesti= ng, to say the least. =A0My conclusion is that Randy's warning is well foun= ded.=0A=0AI would, perhaps, disagree with the admonition that retracting fl= aps when on final will result in a guaranteed disaster. =A0Certainly any ch= ange in configuration at the last second creates a high work load, but at l= east in my airplane, the difference in behavior between 20 degrees and 40 d= egrees of flaps is 90% drag. =A0So, if one were to think he was high for th= e landing, added full flaps and then discovered he was now low, I see no pr= oblem with then retracting the flaps to 10 or 20 degrees. =A0Assuming the s= peed were high (120?) the flaps could even be retracted all the way without= problem except for the pitch change required. =A0And then dropping the fla= ps during the flare is a good way to arrest the descent. =A0I'm a little re= luctant to post this last paragraph as I have no credentials (no military f= ighter jet experience, no instructor rating, no multi-engine jet time, and = no stays in Holiday Inn Express) except for a modest understanding of the engineering principles involved.=0A=0AGary=0A=0A=0A --0-1559056293-1264955198=:931 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
After this discussion I coded some calculation done years ago whe= n a similar thread was discussed.  The results show vertical and forwa= rd speed over time given a number of inputs like weight, initial steady sta= te descent rate, initial approach speed, and a bunch of aircraft specific p= arameters like wing area, aspect ratio,etc.  One parameter that turned= out to be a big player was how much of the remaining lift available was us= ed during the flare.  That is, hard do you pull back on the stick.&nbs= p; 40% seemed to make the landing profile from a steep descent look right i= n terms of duration of the round-out based on observing typical landings.&n= bsp; It is however a variable that can make or break a landing.  It st= retches or compresses the time in the flare significantly and thus allows more or less decay in air speed.  Induced drag changes were le= ss pronounced than expected, especially when only using 40% of the availabl= e margin to stall.  This is reduced further in ground effect.
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A typical steep (1,500 fpm) power off flare is showing a 15 kt de= cay in airspeed whereas the transition from a 3 degree ILS (500 fpm) only c= ost 3 kts.  The amount deacy is strongly tied to initial speed.&n= bsp; At a higher initial speed the decay is less than for the same approach= at a lower speed.  For example a steep approach case entered at 80 kt= s lost 18 KIAS while the same profile entered at 90 KIAS lost only 9 k= ts.  That makes sense given energy being a squared function of speed.&= nbsp; A little more speed gets you a lot more energy.
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Chri= s Zavatson
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N91CZ
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360std
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&n= bsp;
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= =0AFrom: Gary Casey <cas= ey.gary@yahoo.com>
To: lml@lancaironline.net
Sent: Sun, January 31, 2010 6:57:44 AM
Subject: [LML] Re: Engine out gear down Issue/The procedure!= This was a wake up call for me..

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I = ran through some numbers regarding Michael's comments below.  Starting= with the sailplane comment, he says that slowing from 135kts to 65 in a zo= om can result in a gain of 800 feet.  If all the energy were converted= to altitude(no drag) the gain would be 1,276 ft, so a gain of 800 ft seems= reasonable for a very low-drag airframe - 2/3 of the energy can be convert= ed to altitude.  In the case mentioned of 120 kts to 75 kts the number= comes out to a gain of 765 ft.  How much of that is eaten up by drag?=  Certainly compared to the sailplane, a lot.  Would the altitude= gain be half?  I doubt it.  1/4?  Maybe, so as a guess you = could count on perhaps a 200 ft altitude gain.  How much do you need t= o flare?  Depends on the descent rate.  I calculated it based on = 2,000 ft/min - arresting that is equivalent to an altitude gain of 34.5 ft,= much lower than the 200 ft mentioned above.  It would be good if someone measured the actual no-power descent rate with gear and= flaps down.
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In summary, the math suggests t= hat a no-power approach speed of 120 kts should leave more than enough ener= gy to flare.  How much more?  I'll bet not a lot, but still more.=  I don't have an answer to the question, but this is how the numbers = work out.  I have done a full-flap no-power descent with my ES (gear d= own, of course :-) at 105 kts and the descent rate was over 2,000 ft/min wi= th a frighteningly high negative deck angle.  Flaring from that condit= ion would be interesting, to say the least.  My conclusion is that Ran= dy's warning is well founded.
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I would, perha= ps, disagree with the admonition that retracting flaps when on final will r= esult in a guaranteed disaster.  Certainly any change in configuration= at the last second creates a high work load, but at least in my airplane, = the difference in behavior between 20 degrees and 40 degrees of flaps is 90= % drag.  So, if one were to think he was high for the landing, added f= ull flaps and then discovered he was now low, I see no problem with then re= tracting the flaps to 10 or 20 degrees.  Assuming the speed were high = (120?) the flaps could even be retracted all the way without problem except= for the pitch change required.  And then dropping the flaps during th= e flare is a good way to arrest the descent.  I'm a little reluctant t= o post this last paragraph as I have no credentials (no military fighter je= t experience, no instructor rating, no multi-engine jet time, and no stays = in Holiday Inn Express) except for a modest understanding of the engineering principles involved.
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Gary

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