Matronics Email Lists :: View topic - Gear Position vs Elevator authority

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Gear Position vs Elevator authority

Matronics Email Lists Forum Index -> Zenith-List

View previous topic :: View next topic

Author Message

Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Tue Apr 24, 2007 9:07 am Post subject: Gear Position vs Elevator authority

All the recent discussion revolving around gear position, different kinds of landing gear and etc., has been very interesting.....  especially since I haven't gotten to the gear installation part yet.



I see that Zenith has turned the gear around from the original design in the latest plans supposedly to accomodate heavier engines.  I hear comments about the tendancy of the XL to hug the ground on takeoff and slam the nose down on landing with the gear in the flat side back position.  All very interesting.



I owned a Cessna 182 for 7 years.  It tended to be nose heavy and indeed a lot of 182's have suffered firewall damage from hard, nose first landings.  My solution was to carry a little power into the flare to help maintain a proper landing attitude.   That approach made for smooth arrivals without using up too much more runway.  My question is, if the XL with the gear flat side back wants to drop the nose, has anyone found that carrying a little power into the flare gives enough elevator authority to make a nice, mains first arrival or is the problem more extreme than what I found with the 182?



Interestingly enough, after the first year of Cessna 172 production (1956) the gear was moved back a couple of inches to improve ground handling...



Tim



DO NOT ARCHIVE

_________________
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Tue Apr 24, 2007 10:12 am Post subject: Gear Position vs Elevator authority

Making a mains first arrival in my Zodiac isn't a problem at all.  

It's just that as soon as the mains hit, the nose wants to drop  

quickly. As long as you are expecting it, it isn't hard to keep the  

nose from hitting too hard. You have to be ready to give it some back  

pressure as soon as the mains hit. Carrying a little power on  

touchdown will help but it's not really necessary. The Zodiac has a  

lot of elevator authority until you're well below flying speed.



As far as hugging the ground on the takeoff run, I can rotate well  

before takeoff speed but it takes quite a bit of pack pressure. If  

you are used to Cessnas, the main thing you will notice is that  

unlike the Cessna, the Zodiac will not lift off on its own, you have  

to apply some back pressure. This is not uncommon behavior for a low  

wing airplane but with my gear in the aft position, it takes a bit  

more pressure than it aught to. I have to be ready to release some  

back pressure as the mains leave the ground. I don't consider this a  

dangerous behavior, just different. It will get your attention if  

you're not expecting it. A Cessna 150/152/172 will get noticeably  

light on the mains as the speed builds up and will generally lift off  

on its own at around 60 to 70 mph. My Zodiac will stay firmly on its  

gear until I rotate it at around 60 mph. This actually is a good  

behavior for strong crosswinds because the plane won't tend to start  

drifting sideways just before liftoff as I've noticed sometimes in  

Cessnas. Before my first flight in my Zodiac, I had 300 hours of  

flight time, mostly in Cessna 150/152s and Skyhawks with several  

hours in a Cardinal, Cardinal RG and a Cutlass RG and a few hours in  

a low wing Beech.



By my calculations, I could turn my gear around without causing any  

problems with entering from the rear step and this would probably  

greatly reduce the two above behaviors. I will probably do this some  

day, it just isn't a serious enough problem to  make this a high  

priority modification.



On Apr 24, 2007, at 1:08 PM, Tim Juhl wrote:



 	  Quote: 	
		  

 I see that Zenith has turned the gear around from the original  

 design in the latest plans supposedly to accommodate heavier  

 engines.  I hear comments about the tendency of the XL to hug the  

 ground on takeoff and slam the nose down on landing with the gear  

 in the flat side back position.  All very interesting.



 I owned a Cessna 182 for 7 years.  It tended to be nose heavy and  

 indeed a lot of 182's have suffered firewall damage from hard, nose  

 first landings.  My solution was to carry a little power into the  

 flare to help maintain a proper landing attitude.   That approach  

 made for smooth arrivals without using up too much more runway.  My  

 question is, if the XL with the gear flat side back wants to drop  

 the nose, has anyone found that carrying a little power into the  

 flare gives enough elevator authority to make a nice, mains first  

 arrival or is the problem more extreme than what I found with the 182?


	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

tonyplane(at)bellsouth.ne
Guest

Posted: Tue Apr 24, 2007 10:24 am Post subject: Gear Position vs Elevator authority

Tim

  

 Speaking only for my XL 

  

 No problem landing mains first, in fact I do not  believe I have ever landed the XL nose first.  

  

 The problem with the "aft"  gear position,  especially with full flaps and the resulting nose down pitching moment, is once  the mains touch the nose drops and even with the stick full or almost  full aft I can not keep the nose off.   With full flaps, If  there is much speed beyond full stall and a high sink rate, the mains hit and  the nose comes down hard and bounces you back up into the air .   If  I hit a gust when flaring, a little power smoothes things out.   (Be nice to have a hydraulic type shock absorber vice a bungee on the nose  strut)

  

 If I have a good crosswind, or the days are gusty,  I use zero to min flaps.  Without the additional high nose down pitching  moment of full flaps, the nose does not come down as rapidly on touch  down and the airplane tends to stick to the runway.  (I have not tried  it, but I believe I could apply full power and run down the runway and not lift  off without elevator input at zero trim.  My  airplane requires little to no trim in pitch and roll in cruise.  I guess I  lucked out and do not have a heavy left wing as others have  reported).

  

 My CG  is about 360 mm (range is 300 -  450) when I am flying it by myself.

  

 I believe I once read that an XL once used for  training was limited to 10 degrees flaps for the students.

  

  

 Tony Graziano

 XL/Jab3300 :N493TG; 234 hrs

  

 ---------------------

  

             Gear Position vs Elevator        authority        From:              Tim Juhl (juhl(at)avci.net ([email]juhl(at)avci.net?subject=Re:%20Gear%20Position%20vs%20Elevator%20authority&replyto=1177434480.m2f.108949(at)forums.matronics.com[/email]))        Date:              [b]Tue Apr 24 - 10:10        AM[/b] [quote] 	  Quote: 	
		  All the recent discussion revolving around gear position, different kinds of landing

gear and etc., has been very interesting.....  especially since I haven't

gotten to the gear installation part yet.



I see that Zenith has turned the gear around from the original design in the latest

plans supposedly to accomodate heavier engines.  I hear comments about the

tendancy of the XL to hug the ground on takeoff and slam the nose down on landing

with the gear in the flat side back position.  All very interesting.



I owned a Cessna 182 for 7 years.  It tended to be nose heavy and indeed a lot

of 182's have suffered firewall damage from hard, nose first landings.  My solution

was to carry a little power into the flare to help maintain a proper landing

attitude.   That approach made for smooth arrivals without using up too much

more runway.  My question is, if the XL with the gear flat side back wants

to drop the nose, has anyone found that carrying a little power into the flare

gives enough elevator authority to make a nice, mains first arrival or is the

problem more extreme than what I found with the 182?



Interestingly enough, after the first year of Cessna 172 production (1956) the

gear was moved back a couple of inches to improve ground handling...



Tim



DO NOT ARCHIVE



--------

DO NOT ARCHIVE

______________

CFII

Champ L16A flying

Zodiac XL - Jabiru 3300A

Working on wings



	
[b]

p.mulwitz(at)worldnet.att
Guest

Posted: Tue Apr 24, 2007 10:34 am Post subject: Gear Position vs Elevator authority

Hi Tim,



I used a different but similar approach to landing a 182.  I would 

approach with power off, but pop the throttle to flare.  This saved 

me from having to do a "He-Man" tug on the yoke to pull the nose up.



I don't have any time on the XL yet, but I expect this to be a very 

different experience from the 182.  This is because the 182 weighs 

over twice as much as the XL and has a lot more inertia.



There have been many comments and questions regarding the landing and 

takeoff characteristics of the XL.  There have also been at least 

three different elevator trim designs in just the last two years.  I 

must conclude from all this that the differences with different 

weight and power engines on this very light airplane are very significant.



I am using a Jabiru engine which is not as heavy as most engine 

choices for the XL and provides the maximum allowable power.  Still I 

plan to install the gear with the main wheels in the forward 

position.  This should give me the most forward empty CG and lightest 

nose for holding the nose wheel off the ground.  The downside risk 

here is that the tail may drop during loading, but I am not too 

worried about this since it will hit the ground on the rear tie down 

point which is both hard and strong.



Paul

XL fuselage

At 09:08 AM 4/24/2007, you wrote:

 	  Quote: 	
		  



All the recent discussion revolving around gear position, different 

kinds of landing gear and etc., has been very 

interesting.....  especially since I haven't gotten to the gear 

installation part yet.



I see that Zenith has turned the gear around from the original 

design in the latest plans supposedly to accomodate heavier 

engines.  I hear comments about the tendancy of the XL to hug the 

ground on takeoff and slam the nose down on landing with the gear in 

the flat side back position.  All very interesting.



I owned a Cessna 182 for 7 years.  It tended to be nose heavy and 

indeed a lot of 182's have suffered firewall damage from hard, nose 

first landings.  My solution was to carry a little power into the 

flare to help maintain a proper landing attitude.   That approach 

made for smooth arrivals without using up too much more runway.  My 

question is, if the XL with the gear flat side back wants to drop 

the nose, has anyone found that carrying a little power into the 

flare gives enough elevator authority to make a nice, mains first 

arrival or is the problem more extreme than what I found with the 182?



Interestingly enough, after the first year of Cessna 172 production 

(1956) the gear was moved back a couple of inches to improve ground handling...



Tim

Ben52425(at)aol.com
Guest

Posted: Tue Apr 24, 2007 1:31 pm Post subject: Gear Position vs Elevator authority

HI TIM

  I HAD A 182 FOR 35 YRS AND MADE POWER ON LANDING, S. NOSE HIGH

  TOOK 3 HOUR, S, IN A 601XL  (NEW EXPERIENCE) NO TROUBLE DRAGGING THE TAIL. NOT MUCH FORWARD VIEW. GOT TO TRY LOOKING DOWN THE RUNWAY SO MORE PRACTICE FOR ME

                                                                  BEN

**************************************

 See what's free at http://www.aol.com.  [quote][b]

passpat(at)aol.com
Guest

Posted: Tue Apr 24, 2007 2:27 pm Post subject: Gear Position vs Elevator authority

Ben

 

 Sounds like you understand adding a

 little power keeps you from banging the nose wheel at landing.

 

  

 Pat  

 

  

 --

amyvega2005(at)earthlink.
Guest

Posted: Tue Apr 24, 2007 2:35 pm Post subject: Gear Position vs Elevator authority

when i put my mains on 1 year ago i notice what al you have noticed, that the plans are different than the book.   Brian is correct. if you put the mains either way, it won't matter for the ecception of pulling back on the yoke to take off, versus, trimming for auto take off.  Originally the zodiac had lighter engines such as the 912  85 hp.  hence the mains facing "back".

with the heavier Continental or Jabirus, the "flat side forward is fine", just don't have two people standing on the wing step, to get in at the same time.  I have flown both positions and it is tougher to hold the nose up at touch down or in grass field takeoffs.  other than that, thats it.

Juan Vega



--

Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Wed Apr 25, 2007 10:28 am Post subject: Re: Gear Position vs Elevator authority

For those with flight experience in an XL - with the Flat back gear, is there a significant difference in takeoff and landing performance when you have have both seats occupied compared to flying solo?



Tim

_________________
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Wed Apr 25, 2007 10:52 am Post subject: Gear Position vs Elevator authority

With both seats full the CG is a bit farther aft and it's a little  

bit easier to rotate and pitch authority increases some. Considering  

that adding a "standard sized" passenger will increase takeoff weight  

by about 15%, you  should expect a significant difference in takeoff  

roll and climb rate.

On Apr 25, 2007, at 2:28 PM, Tim Juhl wrote:



 	  Quote: 	
		   



 For those with flight experience in an XL - with the Flat back  

 gear, is there a significant difference in takeoff and landing  

 performance when you have have both seats occupied compared to  

 flying solo?



 Tim


	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

gfmjr_20(at)HOTMAIL.COM
Guest

Posted: Wed Apr 25, 2007 11:07 am Post subject: Gear Position vs Elevator authority

"is there a significant difference in takeoff and landing performance when 

you have have both seats occupied compared to flying solo?"



Tim--

   I do not see or feel any difference solo or loaded to gross, other than 

dropping faster in altitude as would be expected.  I still have to pull the 

plane off the runway and as soon as the mains touch on landing the nose 

comes down.  By the use of flaps and a little power you can slow the plane 

down such that when the nose gear does come down the impact is rather light. 

Of course this iswith the use of a Rotax.



George May

601XL  912s---67 hours



_________________________________________________________________

Need a break? Find your escape route with Live Search Maps. 

http://maps.live.com/default.aspx?ss=Restaurants~Hotels~Amusement%20Park&cp=33.832922~-117.915659&style=r&lvl=13&tilt=-90&dir=0&alt=-1000&scene=1118863&encType=1&FORM=MGAC01

MaxNr(at)aol.com
Guest

Posted: Wed Apr 25, 2007 12:28 pm Post subject: Gear Position vs Elevator authority

Do not archive

 The question that comes to mind if you have difficulty holding the nose off is: " What is the actual computed CG when landing?" Is it near the fwd limit? It must be. CG can be brought under control by moving the battery or adding ballast in the tail. When solo, I carried 50 lb. of sand bags in the baggage compartment of my Beech Musketeer. Gave it a real personality change. Somebody told me years ago that after you locate the ready for flight CG, drop a plum bob. Then swing it aft about ten (no more than fifteen) degrees and that's where the MLG axle should be. Go the other way for tailwheels. You really have to locate the CG in its "3D" position. It will be some distance up from the belly into the interior of the A/C. This is called a "wetted line" or "water line" (W/L on the drawings). Not practical to do without some approximation. 

 A friend of mine who is a retired Marine used to instruct on T-34C's at the Navy Primary Flight school at nearby NAS Whiting Field. He described a technique that was used to land real short. It was likely not in the syllabus. When in the flare or even prior, apply full nose down trim. The tab goes up. It augments the full up elevator and gives you more authority and a shorter, slower landing. Control pressure is manageable at slow speed. I'm sure that it is not an approved NATOPS maneuver, but just something the manual writers never thought of. But then again, there are not supposed to be tire marks on the top of water tanks on the downwind leg of various Navy fields in the Pensacola area either. 

 

 Bob  

 601XL/Lyc  Do not archive

**************************************

 See what's free at http://www.aol.com.  [quote][b]

gfmjr_20(at)HOTMAIL.COM
Guest

Posted: Wed Apr 25, 2007 12:49 pm Post subject: Gear Position vs Elevator authority

do not archive



My CG is actually more reaward than I'd like, so I do not believe it is just 

a matter of CG location.  I believe it is a function of the landing gear 

placement and angle of attack of the wing.



George May

601XL 912s--67 hours

 	  Quote: 	
		  From: MaxNr(at)aol.com

Reply-To: zenith-list(at)matronics.com

To: Zenith-List(at)matronics.com

Subject: Re:Gear Position vs Elevator authority

Date: Wed, 25 Apr 2007 16:27:54 EDT



Do not archive

The question that comes to mind if you have difficulty holding the nose off

is: " What is the actual computed CG when landing?" Is it near the fwd 

limit?

It must be. CG can be brought under control by moving the battery or adding

ballast in the tail. When solo, I carried 50 lb. of sand bags in the 

baggage

compartment of my Beech Musketeer. Gave it a real personality change. 

Somebody

told me years ago that after you locate the ready for flight CG, drop a 

plum bob.

Then swing it aft about ten (no more than fifteen) degrees and that's where

the MLG axle should be. Go the other way for tailwheels. You really have to

locate the CG in its "3D" position. It will be some distance up from the 

belly

into the interior of the A/C. This is called a "wetted line" or "water 

line"

(W/L on the drawings). Not practical to do without some approximation.

A friend of mine who is a retired Marine used to instruct on T-34C's at the

Navy Primary Flight school at nearby NAS Whiting Field. He described a

technique that was used to land real short. It was likely not in the 

syllabus. When in

the flare or even prior, apply full nose down trim. The tab goes up. It

augments the full up elevator and gives you more authority and a shorter, 

slower

landing. Control pressure is manageable at slow speed. I'm sure that it is 

not

an approved NATOPS maneuver, but just something the manual writers never

thought of. But then again, there are not supposed to be tire marks on the 

top of

water tanks on the downwind leg of various Navy fields in the Pensacola 

area

either.



Bob

601XL/Lyc  Do not archive

**************************************

  See what's

free at http://www.aol.com.


	


_________________________________________________________________

Exercise your brain! Try Flexicon. 

http://games.msn.com/en/flexicon/default.htm?icid=flexicon_hmemailtaglineapril07

amyvega2005(at)earthlink.
Guest

Posted: Wed Apr 25, 2007 1:21 pm Post subject: Gear Position vs Elevator authority

Obviously YES, the plane with one body is 220 lbs (approx) lighter, big difference.Longer landing roll longer take off roll, that is why there is a weight limit. They typically have two sets of numbers when quoting performance, two person and one person.

I am sure someone on this web will say the other wise, just think with common sense.two people are heavier than one, thus more mass to push  around.

Juan



--

Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Thu Apr 26, 2007 7:33 am Post subject: Re: Gear Position vs Elevator authority

I guess I should have been more precise in my question concerning the performance difference in an XL with one versus two aboard.  What I wanted to know is whether filling both seats reduced or increased the reported nose heaviness with the gear flat side back.



I fly a 85 HP Champ with tandem seating and both a nose and a wing tank.  I am well aware of the behavior differences between one or two occupants and where the fuel or baggage is carried in such a light aircraft  (gross wt. 1220).  Since I fly it solo mostly, when I got a field approval to install a rudimentary electrical system I installed the battery behind the rear seat which helps a bit with the CG.



Sorry if I confused the issue.

TJ

_________________
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!

Display posts from previous:

	Matronics Email Lists Forum Index -> Zenith-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum