X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 13 Aug 2005 21:52:37 -0400 Message-ID: X-Original-Return-Path: Received: from smtp105.sbc.mail.mud.yahoo.com ([68.142.198.204] verified) by logan.com (CommuniGate Pro SMTP 5.0c1) with SMTP id 668061 for lml@lancaironline.net; Sat, 13 Aug 2005 12:42:10 -0400 Received-SPF: none receiver=logan.com; client-ip=68.142.198.204; envelope-from=whiskeyb@sbcglobal.net Received: (qmail 72028 invoked from network); 13 Aug 2005 16:41:25 -0000 Received: from unknown (HELO ?192.168.1.102?) (whiskeyb@sbcglobal.net@69.105.200.169 with login) by smtp105.sbc.mail.mud.yahoo.com with SMTP; 13 Aug 2005 16:41:24 -0000 Received: from 127.0.0.1 (AVG SMTP 7.0.338 [267.10.8]); Sat, 13 Aug 2005 09:38:21 -0700 X-Original-Message-ID: <000601c5a025$6ae2a6c0$6601a8c0@PhiPounder> From: "Wally Bestgen" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Torqued to death X-Original-Date: Sat, 13 Aug 2005 09:38:20 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0003_01C59FEA.BDADE120" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0003_01C59FEA.BDADE120 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Most light airplane initial training is accomplished is aircraft that = are underpowered or just adequately powered. Aircraft that fall in to = that category do not pose unsafe flight characteristics with abrupt = throttle movement. I suspect when the Lancair IVP ways initially = designed, 350 HP not 750 was assumed to be the max. I believe Brent is = correct in his analysis of the problem. Is the airplane unsafe? I = don't think so. Does the airplane require additional operational = considerations and training? Absolutely! =20 There are more considerations than excess horsepower and torque at play = here. In addition there is turbine lag. In any jet engine 70% of the = thrust is produced in the last 25% of the RPM. In the late 60's Unites = Airlines was made painfully aware of this fact at SLC. A B727 crashed = short of the runway. The crew transitioning from piston airplanes = pushed the power up from idle to arrest the decent rate. On that = particular engine it can take as long as 7 seconds for the engine to = accelerate. In this case by the time the engines came up to speed the = aircraft had hit the ground. In more modern jet engines the problem = still exists. It has been mitigated by a flight idle (vs. ground idle) = mode in the fuel controller. Depending on the airplane, flight idle is = activated by extension of the flaps or gear. This feature does not = exsist in the 601. The Walter 601 is a free turbine which means there is = no mechanical link between the powered turbine and the turbine that = drives the propeller. The propeller is "free wheeling" and is = controlled by the governor. Thus the propeller RPM does not have a = direct relationship with the speed of the engine. Keeping that in mind, = just because the propeller is turning at max RPM (2080 in the Walter) = turbine lag is not eliminated. We can imagine a scenario with a = aircraft on short finial, power at Idle, prop 2080 rpm. The aircraft = slows and descends below the intended glide path. A small correction is = added and nothing happens. The natural reaction is to add more power by = advancing the throttle. The situation compounds as ground starts to = rise rapidly more throttle movement is applied and as the nose is = pitched up airspeed slows. At some point the power turbine comes up to = speed and now we have horsepower and torque. Lots of horsepower and = torque. The correct reaction would be to retard the throttle, but as = pilots our first job is to fly the airplane and not hit the ground. At = that points every body is a passenger to the point of impact. It is = imperative that turbine pilot understand this concept, train accordingly = and stay ahead of the airplane. Power available. Our community has suffer numerous stall spin accidents = in the IVP. The power and turbine lag exacerbates this problem. It is = critical to use only the power required for these maneuvers and = recoveries. The problem is not specific to our airplanes. In more = complex airplanes, aircraft systems help mitigate the effects of excess = power. In the B777 (with auto throttles) with the first push of the Go = Around button the engines are programmed to produce just enough power = to result in a 2000 feet a minute rate of climb. Push the button a = second time and you get the benefit of 90,000 pounds of thrust from each = engine. The bottom line is training on the use of the throttle and = understanding that this is a different animal than a piston powered = airplane. In the case of the stall recovery the aircraft is in the most = vulnerable condition. High angle of attack and low power setting. A = perfect setup for the use a more power than that amount required. Again = training and education is the solution to the problem. In my airplane I = had initially decided not to put a AOA indicator in the airplane. In = light of our safety record I have I have purchased an AOA with an aural = warning. Part of my 'memory items" will be to think throttle movement = when I here "Stall, Push". Slow airspeed will always reqire something = less that full power. =20 ----- Original Message -----=20 From: Brent Regan=20 To: Lancair Mailing List=20 Sent: Friday, August 12, 2005 7:14 PM Subject: [LML] Torqued to death During a recent post crash investigation of a Walter 601 powered (not = a Lancair) aircraft I was having difficulty understanding what caused a = left roll just before the crash on short final. The roll had an average = rate of 46 degrees per second and corresponded with a power increase. = Given the 745 available horsepower (near sea level) and the 2,067 RPM = prop speed I calculated an engine reaction torque of 1,893 foot pounds, = roughly the same as putting a 200 pound weight about mid span on the = aileron. Factor in that the airspeed was only 120 KIAS and you get that = queasy feeling in the pit of your stomach. The data shows that plane was on short final when the pilot let the = plane get a little low and slow. He drops the nose slightly but doesn't = accelerate because of the drag of the prop and/or he is behind the lift = curve. He punches the throttle and pulls the nose up. The added load = on the left wing due to the torque reaction either stalls that wing or = overwhelms the aileron authority and the plane begins an uncontrolled = left roll. Five terrifying seconds later the plane has rolled 260 = degrees and the right wing is pointing straight down. This is the last = data point and the plane crashes, with two fatalities, less than 5 = seconds later. To all you LIV Turbine guys out there, remember this well. The Walter = is a LOT of motor for those little wings. Low and slow is not a place = you want to be and putting in the power is not always the solution.=20 I would be interested to know what happens (at 10,000 feet) if you = slow to ~120 KIAS and then apply full power. Do you still have any = aileron authority? Regards Brent Regan ------=_NextPart_000_0003_01C59FEA.BDADE120 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Most light airplane initial = training  is=20 accomplished is aircraft that are underpowered or just adequately = powered. =20 Aircraft that fall in to that category do not pose unsafe  flight=20 characteristics with abrupt throttle movement.  I = suspect when=20 the  Lancair IVP ways initially designed, 350 HP not 750 was = assumed=20 to be the max.  I believe Brent is correct in his analysis of the=20 problem.  Is the airplane unsafe?  I don't think = so.   Does=20 the airplane require additional operational considerations and training? = Absolutely! 
 
There are more considerations than = excess=20 horsepower and torque at play here.  In addition  there = is=20 turbine lag.   In any jet engine 70% of the thrust is produced = in the=20 last 25% of the RPM.  In the late 60's Unites = Airlines was made=20 painfully aware of this fact at SLC.  A B727 crashed short of = the=20 runway.  The crew transitioning from piston airplanes pushed the = power up=20 from idle to arrest the decent rate.  On that particular engine it = can take=20 as long as 7 seconds for the engine to accelerate.  In this case by = the=20 time the engines came up to speed the aircraft had hit the ground.  = In more=20 modern jet engines the problem still exists.  It has been = mitigated by a flight idle (vs. ground idle) mode in the fuel=20 controller.  Depending on the airplane, flight idle is = activated=20 by extension of the flaps or gear.  This feature does not = exsist in=20 the 601. The Walter 601 is a free turbine which means there is = no=20 mechanical link between the powered turbine and the turbine that drives = the=20 propeller.  The propeller is "free wheeling" and is controlled by = the=20 governor.  Thus the propeller RPM does not have a direct = relationship with=20 the speed of the engine.  Keeping that in mind, just because the = propeller=20 is turning at max RPM (2080 in the=20 Walter) turbine lag is not eliminated.  We can imagine a = scenario with=20 a aircraft on short finial, power at Idle, prop 2080 rpm.  The = aircraft=20 slows and descends below the intended glide path.  A small = correction is=20 added and nothing happens.  The natural reaction is to add more=20 power by advancing the throttle.  The situation compounds as = ground=20 starts to rise rapidly more throttle movement is applied and as the nose = is=20 pitched up airspeed slows.  At some point the power turbine comes = up to=20 speed and now we have horsepower and torque.  Lots of horsepower = and=20 torque.  The correct reaction would be to  retard the = throttle, =20 but as pilots our first job is to fly the airplane  and not hit the = ground.  At that points every body is a passenger to the point of=20 impact.   It is imperative that turbine pilot = understand this=20 concept, train accordingly and stay ahead of the airplane.
 
Power available.  Our community = has suffer=20 numerous stall spin accidents in the IVP.  The power and turbine=20 lag exacerbates this problem.  It is critical to use only = the=20 power required for these maneuvers and recoveries.  The problem is=20 not specific to our airplanes.  In more complex airplanes, = aircraft=20 systems help mitigate the effects of  excess power.  In the = B777 (with=20 auto throttles) with the first push of the Go Around  button = the=20 engines are programmed to produce just enough power to result in a 2000 = feet a=20 minute rate of climb.  Push the button a second time and you = get the=20 benefit of 90,000 pounds of thrust from each = engine.  The bottom line is training on the use of the = throttle and=20 understanding that this is a different animal than a piston powered=20 airplane. In the case of the stall recovery the aircraft is in = the=20 most vulnerable  condition.  High angle of attack and low = power=20 setting.  A perfect setup for the use a more power than that amount = required.  Again training and education is the solution = to the=20 problem.  In my airplane I had initially decided not to put a AOA = indicator=20 in the airplane.  In light of our safety  record I have I = have=20 purchased an AOA with an aural warning.  Part of my 'memory items" = will be=20 to think throttle movement when I here "Stall, Push".  Slow = airspeed will=20 always reqire something less that full power.  
----- Original Message -----
From:=20 Brent=20 Regan
Sent: Friday, August 12, 2005 = 7:14=20 PM
Subject: [LML] Torqued to = death

During a recent post crash = investigation of a=20 Walter 601 powered (not a Lancair) aircraft I was having difficulty=20 understanding what caused a left roll just before the crash on short = final.=20 The roll had an average rate of 46 degrees per second and corresponded = with a=20 power increase.  Given the 745 available horsepower (near sea = level) and=20 the 2,067 RPM prop speed I calculated an engine reaction torque of = 1,893 foot=20 pounds, roughly the same as putting a 200 pound weight about mid span = on the=20 aileron. Factor in that the airspeed was only 120 KIAS and you get = that queasy=20 feeling in the pit of your stomach.

The data shows that plane = was on=20 short final when the pilot let the plane get a little low and slow. He = drops=20 the nose slightly but doesn't accelerate because of the drag of the = prop=20 and/or  he is behind the lift curve.  He punches the = throttle and=20 pulls the nose up.  The added load on the left wing due to the = torque=20 reaction either stalls that wing or overwhelms the aileron authority = and the=20 plane begins an uncontrolled  left roll. Five terrifying seconds=20 later  the plane has rolled 260 degrees and the right wing is = pointing=20 straight down. This is the last data point and the plane crashes, with = two=20 fatalities, less than 5 seconds later.

To all you LIV Turbine = guys out=20 there, remember this well. The Walter is a LOT of motor for those = little=20 wings. Low and slow is not a place you want to be and putting in the = power is=20 not  always the solution.

I would be interested to know = what=20 happens (at 10,000 feet)  if you slow to ~120 KIAS and then apply = full=20 power.  Do you still have any aileron = authority?

Regards
Brent=20 Regan
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