Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Mon, 29 Nov 2004 11:33:56 -0500 Message-ID: X-Original-Return-Path: Received: from imo-d20.mx.aol.com ([205.188.139.136] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 549664 for lml@lancaironline.net; Mon, 29 Nov 2004 11:31:58 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.139.136; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-d20.mx.aol.com (mail_out_v37_r3.8.) id q.102.5527d50c (25305) for ; Mon, 29 Nov 2004 11:31:23 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <102.5527d50c.2edca8db@aol.com> X-Original-Date: Mon, 29 Nov 2004 11:31:23 EST Subject: Re: [LML] 360 Tail Trim / Stick Force Revisted X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1101745883" X-Mailer: 9.0 Security Edition for Windows sub 1180 -------------------------------1101745883 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 11/29/2004 8:52:33 A.M. Central Standard Time, WarbirdAeroPress@cox.net writes: I'm still searching for some answers, and I just keep coming up with more questions. The basic problem is this: When I lower flaps on my 360, there is not enough pitch trim to take out the nose up stick force required to keep my pitch attitude. Scotty, In general, more information is required - CG, airspeed, flap deflection angle, trim tab size, etc. But first, some observations and comments. If I remember correctly, the flap range is -7* to +45* as measured from faired in to the TE fuselage fillet being -7*. You can check this range on the ground by using a digital level. I am sure you have noticed the tremendous pitch change (nose down) as the flaps are deployed. I think there should be some old e-mails around where I affixed a digital level to the longeron and checked aircraft angles at several speeds and flap angles and the aircraft pitch angle change was as much as 6*. I am also sure that you noticed the pitch change from slowing down to, say, 100 KIAS while the flaps are in full reflex (-7*), resulting in a strong nose up AOA. So, one can consider that the flap position also contributes to aircraft trim at certain airspeeds. Just as wheels down also introduces drag, pitch down and CG moved slightly forward (nose gear). I am sure that you have read here that some almost never go beyond about 30-35* flap extension when landing. This can affect how much nose up trim would be required. If you don't have a flap position indicator, you can position the flaps to various positions on the ground and, using a marking pen, mark the flap position against the wing TE out by an aileron (unless the builder cut off most of the flap leading edge). As to your specific question, another question: At what flap deployment position do you lose the ability to trim for a specific attitude? Please note that some of us could argue that maintaining a fixed descent rate (fixed attitude) and airspeed at say, 100 KIAS with flaps at about +10* (+ 17* from faired in) is very difficult. A little pitch change yields a speed change yields a pitch change........ and the same is true for a speed variation. If you have an AOA indicator and are trying to maintain a steady indication, good luck! Darn persnickety wing if you ask me. If your problem is only at full flap deployment (final approach to landing), don't fully deploy them. Frankly, I can't find a steady state trim position during that flight stage and prefer some feedback to my hand anyway. Of course, that may be because I am using the Reichel trim wheel spring system for the elevator which results in a "dead band" of low force/hi sensitivity - perhaps unlike a tab which has more constant air forces positioning the elevator. Hmmmmm, I guess that speed changes would change the effectiveness of the tab at certain set positions. BTW, is your elevator arm 3" or 4" - this is the length of the bellcrank arm extending down from the elevator to the rearmost elevator pushrod rod end. Oh, how much force is required to overcome the lack of trim? 1#, 2#s...? Anyway, <<<< 1. Is this a simple matter of taking a look at my elevator trim motor and seeing what it's travel limits are? >>>> That's a good thing to know. Maybe the tab isn't quite large enough to handle the elevator's extreme requirements (Your <<<1b. Do I need to modify or increase the size of my trim tab?>>>) - nose up at slow speed and full flaps or nose down at race speeds and flaps at reflex. There are angles at which the tabs only cause drag - that is that the air is separated rather than flowing over the surface. Your could certainly build a longer one if that is indicated. <<<< 1a. Is my aircraft's horizontal incidence set wrong? (I didn't build the plane, how hard is this to screw up?) >>>> Although this is important, it is doubtful that it is set that wrong. Some argue less than -.5*, others (like me) have it accidentally set at -.9* (don't ask) and have no problem. With some fooling around you can measure the incidence of the chord with a water level or making a weird jig from mid horizontal stab leading edge to mid elevator neutral trailing edge....... BTW, what is the upward pitch of the engine? <<<< 2. During cruise flight, and only at aft cg conditions, my elevator does not trail the horizontal stab. It rides down, indicating my tail is heavy. Here are a few examples of my elevator position: >>>>> I can't really see that. Remember that the pitching moment of the wing changes with speed - fast = more nose up. I can't think of anything wrong with unloading the tail (nose down trim) when the back is loaded or you are going fast - Where was the CG? Did you ever carefully reweigh the plane - this can be quite a surprise - and recalculate the CG from the aft of the firewall? Wouldn't we expect the elevator to be at neutral at mid-CG range, 8500" and about 175 KIAS? I think those are pretty close to the design specs. Anything different should require a different trim. Oh, I see you recorded that: <<<>>> <<<< 110 or 120 knots, just me in the plane, don't remember the fuel load. Elevator is slightly up, making me think fwd cg. In the condition I am asking about, the elevator rides this far down, if not a little more. >>>> Where were the flaps? Anyway, hi speed = nose trimmed down, lo speed with flaps = nose trimmed up. <<<<< 3. Have any of you with a O-360 modified the lower intake portion of the cowl, or the oil cooler outlet, to reduce volume, area and drag? I am very interested in your ideas and seeing photos if you have. >>>> While I only have a wee IO320 and NACA oil cooler input air, the small oil cooler output air is dumped into the lower plenum and exits with the rest of the engine cooling air. Call me and we can talk amongst ourselves. hm = 630-655-4811, cell = 630-561-0400 Scott Krueger AKA Grayhawk N92EX IO320 Aurora, IL (KARR) Some Assembly Required Using Common Hand Tools. -------------------------------1101745883 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 11/29/2004 8:52:33 A.M. Central Standard Time,=20 WarbirdAeroPress@cox.net writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
I'm still searching for some answers, and I just keep=20= coming=20 up with more questions. The basic problem is this:
 
When I lower flaps on my 360, there is= not=20 enough pitch trim to take out the nose up stick force required to keep my=20 pitch attitude.
Scotty,
 
In general, more information is required - CG, airspeed, flap deflectio= n=20 angle, trim tab size, etc.
 
But first, some observations and comments.
 
If I remember correctly, the flap range is -7* to +45* as measured from= =20 faired in to the TE fuselage fillet being -7*.  You can check this rang= e on=20 the ground by using a digital level.  I am sure you have noticed the=20 tremendous pitch change (nose down) as the flaps are deployed.  I=20 think there should be some old e-mails around where I affixed a digital leve= l to=20 the longeron and checked aircraft angles at several speeds and flap angles a= nd=20 the aircraft pitch angle change was as much as 6*.  I am also sure that= you=20 noticed the pitch change from slowing down to, say, 100 KIAS while the flaps= are=20 in full reflex (-7*), resulting in a strong nose up AOA.  So, one can=20 consider that the flap position also contributes to aircraft trim at certain= =20 airspeeds.  Just as wheels down also introduces drag, pitch down and CG= =20 moved slightly forward (nose gear). 
 
I am sure that you have read here that some almost never go beyond abou= t=20 30-35* flap extension when landing.  This can affect how much nose up t= rim=20 would be required.
 
If you don't have a flap position indicator, you can position the flaps= to=20 various positions on the ground and, using a marking pen, mark the flap posi= tion=20 against the wing TE out by an aileron (unless the builder cut off most of th= e=20 flap leading edge).
 
As to your specific question, another question: At what flap deployment= =20 position do you lose the ability to trim for a specific attitude?  Plea= se=20 note that some of us could argue that maintaining a fixed descent rate (fixe= d=20 attitude) and airspeed at say, 100 KIAS with flaps at about +10* (+ 17*= =20 from faired in)  is very difficult.  A little pitch change yields=20= a=20 speed change yields a pitch change........ and the same is true for a speed=20 variation.  If you have an AOA indicator and are trying to maintain a=20 steady indication, good luck!  Darn persnickety wing if you ask=20 me. 
 
If your problem is only at full flap deployment (final approach to=20 landing), don't fully deploy them.  Frankly, I can't find a steady stat= e=20 trim position during that flight stage and prefer some feedback to my hand=20 anyway.  Of course, that may be because I am using the Reichel trim whe= el=20 spring system for the elevator which results in a "dead band" of low force/h= i=20 sensitivity - perhaps unlike a tab which has more constant air forces=20 positioning the elevator.  Hmmmmm, I guess that speed changes would cha= nge=20 the effectiveness of the tab at certain set positions.
 
BTW, is your elevator arm 3" or 4" - this is the length of the bellcran= k=20 arm extending down from the elevator to the rearmost elevator pushrod r= od=20 end.
 
Oh, how much force is required to overcome the lack of trim?  1#,=20 2#s...?
 
Anyway,
 
<<<<=20
1. Is this a simple matter of taking a look at my elevat= or=20 trim motor and seeing what it's travel limits are?
>>>>
 
That's a good thing to know.  Maybe the tab isn't quite large enou= gh=20 to handle the elevator's extreme requirements (Your <<<1b. Do I nee= d to=20 modify or increase the size of my trim tab?>>>) - nose up at s= low=20 speed and full flaps or nose down at race speeds and flaps at reflex. =20 There are angles at which the tabs only cause drag - that is that the air is= =20 separated rather than flowing over the surface.  Your could certainly b= uild=20 a longer one if that is indicated.
 
<<<<
1a. Is my aircraft's horizontal incidence set wrong? (I=20= didn't=20 build the plane, how hard is this to screw up?)
>>>>
 
Although this is important, it is doubtful that it is set that wrong.&n= bsp;=20 Some argue less than -.5*, others (like me) have it accidentally set at -.9*= =20 (don't ask) and have no problem.  With some fooling around you can meas= ure=20 the incidence of the chord with a water level or making a weird jig from=20 mid horizontal stab leading edge to mid elevator neutral trai= ling=20 edge.......
 
BTW, what is the upward pitch of the engine?
 
<<<<
2. During cruise flight, and only at aft cg conditi= ons,=20 my elevator does not trail the horizontal stab. It rides down, indicating my= =20 tail is heavy. Here are a few examples of my elevator position:
>>>>>
 
I can't really see that.  Remember that the pitching moment of the= =20 wing changes with speed - fast =3D more nose up. I can't think of anything w= rong=20 with unloading the tail (nose down trim) when the back is loaded or you are=20 going fast - Where was the CG?  Did you ever carefully reweigh the= =20 plane - this can be quite a surprise - and recalculate the CG from the aft o= f=20 the firewall?  Wouldn't we expect the elevator to be at neutral at= =20 mid-CG range, 8500" and about 175 KIAS?  I think those are pretty close= to=20 the design specs.  Anything different should require a different=20 trim. 
 
Oh, I see you recorded that: <<<<High speed,= 210=20 mph indicated, mid cg (myself @230, full or nearly full header tank and appr= ox=20 20 gal in wings). Elevator is perfect and trails the stab nicely.=20 .>>>>
 
<<<<
110 or 120 knots, just me in the plane, don't remember t= he=20 fuel load. Elevator is slightly up, making me think fwd cg. In the condition= I=20 am asking about, the elevator rides this far down, if not a little=20 more.
>>>>
 
Where were the flaps?  Anyway, hi speed =3D nose trimmed down, lo=20 speed with flaps =3D nose trimmed up.
 
<<<<<
3. Have any of you with a O-360 modified the lower intak= e=20 portion of the cowl, or the oil cooler outlet, to reduce volume, area and dr= ag?=20 I am very interested in your ideas and seeing photos if you have.
>>>>
 
While I only have a wee IO320 and NACA oil cooler input air, the small=20= oil=20 cooler output air is dumped into the lower plenum and exits with the re= st=20 of the engine cooling air.
 
Call me and we can talk amongst ourselves.  hm =3D 630-655-4811, c= ell =3D=20 630-561-0400=20
 
Scott Krueger=20 AKA Grayhawk
N92EX IO320 Aurora, IL (KARR)

Some Assembly Required=20
Using Common Hand=20 Tools.
-------------------------------1101745883--