Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Sun, 15 Aug 2004 11:00:20 -0400 Message-ID: X-Original-Return-Path: Received: from imo-d23.mx.aol.com ([205.188.139.137] verified) by logan.com (CommuniGate Pro SMTP 4.2) with ESMTP id 365433 for lml@lancaironline.net; Sun, 15 Aug 2004 08:58:41 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.139.137; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-d23.mx.aol.com (mail_out_v37_r3.4.) id q.1d8.28ee5298 (3858) for ; Sun, 15 Aug 2004 08:58:07 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: <1d8.28ee5298.2e50b7df@aol.com> X-Original-Date: Sun, 15 Aug 2004 08:58:07 EDT Subject: Re: [LML] 360 Small Tail Flight Characteristics X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1092574687" X-Mailer: 9.0 for Windows sub 5000 -------------------------------1092574687 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 8/14/2004 1:59:16 PM Central Standard Time, WarbirdAeroPress@cox.net writes: 1. I got what I thought was a good checkout by the previous owner, and didn't really see a problem with flying the airplane. I am using half flaps for landing to limit the aft stick pressure I need to maintain a good approach. There is not enough nose up trim from the elec mac servo to compensate for this. Thoughts, ideas and background? I do know about the Mk II tail, but that is probably not an option. Is there some sort of bob-weight I can install to lower the pitch sensitivity? Scotty, First, everything Mark said is absolutely correct. Second, every wee Lancair 235/320/360 (hereafter 360) is somebody's custom airplane. You may need to adjust some things to your liking and pilot style. 1. Most 360's have stayed with the mechanical friction/spring elevator trim system. There may be some limits if your servo operated system is moving a trim tab that is not effective enough (not large enough?) to meet the requirements of elevator forces at low speeds and certain CG limits. However, a larger trim tab may exceed the ability of the servo (I have seen stripped gears in MAC servos) and alter the balance of the control surface. Your elevator linkage should have been built with a bob-weight (just behind the baggage bulkhead) to add proper feed back during G-loaded maneuvering - make sure it is rigged exactly as Lancair calls out in the construction manual. Small tail 360s are renowned for pitch sensitivity - stay alert. Here is some further discussion of pitch trim: Many, if not most, 360 builders shortened the elevator bellcrank hole location from a 4" arm to a 3" arm. This was first proposed by a girth-challenged builder and results in a 25% reduction in stick movement for the same elevator movement. Another benefit is the that the force necessary to move the elevator is increased by 25% , thus reducing the "lightness." Of course, pitch control is a system - all the consequences must be considered. This change required stronger springs be used for the trim and that required the friction holding the manual trim control be increased so that it became quite an effort to make trim adjustments. Dick Reichel then invented the gear driven spring loaded trim system (with a walnut wheel, no less) that works very well with the increased trim spring forces. I have such modifications and trim system and it is adjusted so that I also run out of nose down trim when fully loaded at race speeds, that is up until about half the fuel is burned off. I have never run out of nose up trim at full flaps even though I have biased my airplane to a more forward CG. My W&B notes that the minimum solo pilot weight is 150 pounds since the CG will be too far forward if the only fuel remaining is in the header tank and the baggage compartment is empty. As you may have noticed, flap deployment has a great effect on the pitch of the airplane. Ergo, half-flaps leaves you with relevant nose up "trim." That is, you are not pitched nose down as much as you would be at full flaps. In the example you gave, the flaps are participating in the trim of your airplane. That is OK if you realize the limits (and options) imposed by their use. Maybe you could examine the range your trim tab moves thru and see if it would be useful to change the range to give more nose up trim? The "big" tail is good but moves the CG aft - not good in airplanes already built with an aft CG bias. The long engine mount moves the engine forward 3" and the CG forward about 1.5". This option is frequently chosen for those with rear CG problems and/or the big tail. It is not so good in an airplane with nose-up trim problems. <<< 2. What should I look for with the stock (Non-Outback) gear? The plane pulls left a bit during taxi, and the rudder is a bit biased to the left. Is this a landing gear issue or a rudder spring tension issue? The nosegear seems pretty fragile and shimmies if I don't keep the nose light with elevator. (It does appear to be serviced properly.) >>> 2. The 360 left-turning tendency is well known - P-factor, small tail lack of control below 40 Kts, weather vaning, even from the prop circulation, etc. Right brake tapping is useful when taxiing and sometimes, even at the start of the take-off roll - especially with a left cross wind. Slow application of throttle during take-off runs and go-arounds is very important. Do some 720 degree steep turns and notice the difference in the force required to hold altitude in left and right turns. The nose gear shimmy should be fixed before the next flight! I have seen cracked and broken engine mounts from operation with shimmy. Contact Lancair since they can re-build the strut or, if it is trash, re-place it. In aviation, nothing that's broken ever fixes itself. Consider the self-centering option if you don't already have it. <<< 3. Blew out both nylo seal brake lines today... got the plane stopped Fred Flintsone style before I ran into anything. The lines in the cockpit are still pliable and flexible, but the portion of the lines in the gear wells are brittle and broke easy when we tore it apart. There appeared to be some heat damage/discoloring there, even though it was within the black plastic cover. Thoughts? Parts already on order from AC Spruce. >>> 3. There are some options. Some people have replaced a foot or so of line at the brake with something more substantial than nyla-flow because of the heat/pressure problem. Some have replaced the lines completely. Others have had the wheel-well brittleness problem - others have not? Some must use their brakes (short runways), others avoid use as much as possible. I was concerned with the fragile look of Nyla-flow, so mine run thru clear Tygon tubing all the way to the brake fitting. The brake line is supported by an adele clamp fastened to the rear of the casting and is tie wrapped to the gear leg in several places so it doesn't flap in the wind. There is a gentle curve from the front of the gear leg to the rear of the wheel well to avoid stress on the line when the gear comes up. I avoid all heavy braking. These are the original circa 1989 lines with 700 landings (701 takeoffs, don't ask). Scott Krueger AKA Grayhawk Sky2high@aol.com II-P N92EX IO320 Aurora, IL (KARR) Opinions and results may vary! -------------------------------1092574687 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 8/14/2004 1:59:16 PM Central Standard Time,=20 WarbirdAeroPress@cox.net writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
1. I got what I thought was a good checkout by the pre= vious=20 owner, and didn't really see a problem with flying the airplane. I am usin= g=20 half flaps for landing to limit the aft stick pressure I need to maintain=20= a=20 good approach. There is not enough nose up trim from the elec mac servo to= =20 compensate for this. Thoughts, ideas and background? I do know about the M= k II=20 tail, but that is probably not an option. Is there some sort of bob-weight= I=20 can install to lower the pitch=20 sensitivity?
Scotty,
 
First, everything Mark said is absolutely correct. 
 
Second, every wee Lancair 235/320/360 (hereafter 360) is somebody's cus= tom=20 airplane.  You may need to adjust some things to your liking and pilot=20 style.
 
1.  Most 360's have stayed with the mechanical friction/spring=20 elevator trim system.  There may be some limits if your servo operated=20 system is moving a trim tab that is not effective enough (not large=20 enough?) to meet the requirements of elevator forces at low speeds= and=20 certain CG limits.  However, a larger trim tab may exceed the ability o= f=20 the servo (I have seen stripped gears in MAC servos) and alter the bala= nce=20 of the control surface.  Your elevator linkage should have been built w= ith=20 a bob-weight (just behind the baggage bulkhead) to add proper feed back= =20 during G-loaded maneuvering - make sure it is rigged exactly as Lancair call= s=20 out in the construction manual.  Small tail 360s are renowned for pitch= =20 sensitivity - stay alert.
 
Here is some further discussion of pitch trim: 
 
Many, if not most, 360 builders shortened the elevator bellcrank hole=20 location from a 4" arm to a 3" arm.  This was first proposed by a=20 girth-challenged builder and results in a 25% reduction in stick movement fo= r=20 the same elevator movement.  Another benefit is the that the force=20 necessary to move the elevator is increased by 25% , thus reducing the=20 "lightness."  Of course, pitch control is a system - all the consequenc= es=20 must be considered.  This change required stronger springs be used for=20= the=20 trim and that required the friction holding the manual trim control be incre= ased=20 so that it became quite an effort to make trim adjustments.  Dick Reich= el=20 then invented the gear driven spring loaded trim system (with a walnut wheel= , no=20 less) that works very well with the increased trim spring forces. 
 
I have such modifications and trim system and it is adjusted so that=20 I also run out of nose down trim when fully loaded at race speeds,= =20 that is up until about half the fuel is burned off.  I have never run o= ut=20 of nose up trim at full flaps even though I have biased my airplane to a mor= e=20 forward CG.  My W&B notes that the minimum solo pilot weight is 150= =20 pounds since the CG will be too far forward if the only fuel remaining is in= the=20 header tank and the baggage compartment is empty.
 
As you may have noticed, flap deployment has a great effect on the pitc= h of=20 the airplane.  Ergo, half-flaps leaves you with relevant nose up=20 "trim."  That is, you are not pitched nose down as much as you would be= at=20 full flaps.  In the example you gave, the flaps are participating in th= e=20 trim of your airplane.  That is OK if you realize the limits (and=20 options) imposed by their use.  Maybe you could examine the range=20= your=20 trim tab moves thru and see if it would be useful to change the range to giv= e=20 more nose up trim?
 
The "big" tail is good but moves the CG aft - not good in airplane= s=20 already built with an aft CG bias.
 
The long engine mount moves the engine forward 3" and the CG forward ab= out=20 1.5". This option is frequently chosen for those with rear CG problems and/o= r=20 the big tail.  It is not so good in an airplane with nose-up trim=20 problems.
 
<<<
2. What should I look for with the stock (Non-Outback) g= ear?=20 The plane pulls left a bit during taxi, and the rudder is a bit biased to th= e=20 left. Is this a landing gear issue or a rudder spring tension issue? The=20 nosegear seems pretty fragile and shimmies if I don't keep the nose light wi= th=20 elevator. (It does appear to be serviced properly.)
>>>
 
2. The 360 left-turning tendency is well known - P-factor, small tail l= ack=20 of control below 40 Kts, weather vaning, even from the prop circulation,=20 etc.  Right brake tapping is useful when taxiing and sometimes, even at= the=20 start of the take-off roll - especially with a left cross wind.  Slow=20 application of throttle during take-off runs and go-arounds is very=20 important.  Do some 720 degree steep turns and notice the=20 difference in the force required to hold altitude in left and right=20 turns.
 
The nose gear shimmy should be fixed before the next flight!  I ha= ve=20 seen cracked and broken engine mounts from operation with shimmy.  Cont= act=20 Lancair since they can re-build the strut or, if it is trash, re-place it.&n= bsp;=20 In aviation, nothing that's broken ever fixes itself.  Consider the=20 self-centering option if you don't already have it.
 
<<<
3. Blew out both nylo seal brake lines today... got the=20= plane=20 stopped Fred Flintsone style before I ran into anything. The lines in the=20 cockpit are still pliable and flexible, but the portion of the lines in the=20= gear=20 wells are brittle and broke easy when we tore it apart. There appeared to be= =20 some heat damage/discoloring there, even though it was within the black plas= tic=20 cover. Thoughts? Parts already on order from AC Spruce.
>>>
 
3.  There are some options.  Some people have replaced a= =20 foot or so of line at the brake with something more substantial than nyla-fl= ow=20 because of the heat/pressure problem.  Some have replaced the lines=20 completely.  Others have had the wheel-well brittleness problem - other= s=20 have not?  Some must use their brakes (short runways), others avoid use= as=20 much as possible.
 
I was concerned with the fragile look of Nyla-flow, so mine run thru=20 clear Tygon tubing all the way to the brake fitting.  The brake li= ne=20 is supported by an adele clamp fastened to the rear of the casting and is ti= e=20 wrapped to the gear leg in several places so it doesn't flap in the wind.&nb= sp;=20 There is a gentle curve from the front of the gear leg to the rear of the wh= eel=20 well to avoid stress on the line when the gear comes up.  I avoid all h= eavy=20 braking.  These are the original circa 1989 lines with 700 landing= s=20 (701 takeoffs, don't ask). =20
 
Scott Krueger=20 AKA Grayhawk
Sky2high@aol.com
II-P N92EX IO320 Aurora, IL=20 (KARR)

Opinions and results may=20 vary!
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