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Flight test report - N773PM

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psm(at)att.net
Guest

Posted: Sat Jun 02, 2012 3:28 am Post subject: Flight test report - N773PM

I just finished writing a short summary of the flight     characteristics and my normal piloting practices for my Zodiac XL -     N773PM.  I did this after considering the preliminary NTSB report     about E-AB accidents and comments on other email lists about people     trying to learn to fly a purchased experimental plane without an AFM     or Pilot's Handbook.  Perhaps a short write-up like this one will     help anyone who wants to learn to fly my plane or even me if my     memory gets any worse.  

     

     Paul

     Camas, WA

     

     

     Here it is:

     

          

Flight Test Report -         N773PM     

By Paul Mulwitz -- June       2,       2012     



          

As phase I flight test nears its end I       wanted to record some of the things learned about this airplane.       The       information presented here is not very official, but it might help       me       or some new pilot have an easy time flying the plane in the       future.     



          

Basic flight performance of this       Zodiac       XL is relatively tame. It has plenty of power and cruises easily       over 110 KIAS. With a heavy throttle it will exceed 120. It has       very little or no stability - especially in the yaw domain. There       is       electric roll and pitch trim but this does a poor job of making it       a       stable flying airplane. The pilot must pay attention all the time       to       keep it flying straight and level.     



          

Takeoff is normal. With no flaps the       ground roll is relatively short and performance is OK. I prefer       using 1/2 flaps until clear of any obstacles. This produces a       quicker departure from the ground. Full flaps on takeoff is a poor       choice. It lifts off before there is good response to the flight       controls. Flap setting is judged by the relative position of the       flaps and ailerons. Initial climb at 70 KIAS works well. At 500       feet AGL I start to think about turning crosswind or exiting the       pattern and reducing power.     



          

Initial cruise at 2500 RPM works well       and gives around 100 KIAS. Maneuvering speed, Va, is 90 KIAS.     



          

Stalls are uneventful. The only thing       I have been able to produce is a deep mush.     



          

My preferred setup for the Dynon based       panel is to display HSI on the pilot's EFIS along with the flight       instruments. RPM is displayed on this display from the EMS. Right       seat display varies with the desires of the occupant from       completely       engine information to a full instrument panel with reduced engine       information. HSI navigation data source can be either the GPS or       VOR. Selection of the source and setting of various bugs and track       information is done with the HS-34 knobs just below the pilot's       display. The knobs also act as push button switches to sync the       bugs.     



          

Like all low wing planes, fuel must be       drawn from only one tank at a time. My common practice is to use       1/2       hour fuel from one tank and then to switch to the other one. This       keeps the fuel load somewhat balanced.     



          

When approaching an airport for       landing       I like to reduce speed to 70 KIAS before reaching the traffic       pattern. 2000 RPM is a good power setting for level flight at 70.       I       continue downwind at 70 and reduce power to idle when opposite the       numbers. A glide is set up with speed at 60 KIAS. This is a good       speed for the remainder of the approach. While on base leg I judge       the approach height and apply full flaps if there is enough       altitude. Landings can be made with any flap setting but full       flaps give a       nicer touchdown speed and attitude.     



          

One strange characteristic of the       Jabiru engine is it will not start while windmilling. If it stops       firing in flight the only way to get it going again is by engaging       the starter motor. Similarly, it is claimed it will not fire from       moving the propeller by hand on the ground.     



          

Carb heat is available but I have       never       used it in flight. The relatively warm position of the carburetor       in       the engine compartment suggests it is really not needed. I check       that it is working when running up the engine before flight along       with a quick magneto check. All three checks show only a minimal       reduction in RPM from the 1800 test power setting. There is no       vacuum system for instrumentation.                	 	

      [quote][b]

hallert

Joined: 16 Jun 2009
Posts: 11

Posted: Sat Jun 02, 2012 7:55 am Post subject: Re: Flight test report - N773PM

Paul,

Always find you posts useful! Just a couple of comments from a 300 hr on AMD 601 XLB driver:

1) Do you really want to reduce pwr at 500 ft? Why not wait till safe 180 deg return altitude as many engine problems occur with change of settings.

2) Why not drop flaps before entering pattern to allow more time to check wind, look for traffic, etc.

3) Puzzled by yaw instability comment. Notice nothing unusual in mine based on flying Cesnas, Pipers, Mooneys, T-Craft, Gliders.

4) You engine produces at least 6 kts. more than I get with the O-200.



Ted Haller

psm(at)att.net
Guest

Posted: Sat Jun 02, 2012 8:22 am Post subject: Flight test report - N773PM

Hi Ted,



I agree with you about engine failures.  My point was to not touch the 

engine controls before 500 AGL rather than suggesting it was necessary 

at that point.  The Jabiru likes to climb at full power in all cases.  

This gives a richer mixture for improved engine cooling.  Keep in mind 

the Jabiru doesn't have mixture control but instead has a self 

controlling carburetor - much like the Rotax.



I like to fly without flaps unless they are called for.  I think you can 

get a better glide with no flaps if needed to reach the runway without 

adding power.  This is just a style point, and I don't see anything 

really wrong with using flaps before reaching base leg.  I do think it 

is a great idea to slow down before entering the pattern to avoid 

running over Champs, Cubs, and other planes that can't go 100 knots.



The yaw stability problem has plagued me for a while now.  I think it is 

inherent in the XL design.  If you are flying straight and kick the nose 

to either side a little bit (less than 11 degrees) I think you will find 

it doesn't return to center.  It just stays where you leave it and flies 

a bit sideways.



It doesn't surprise me my Jabiru powered XL is faster than a Continental 

O-200 powered AMD XL.  This is true even though I don't have wheel pants 

and you probably do.  The Jabiru weighs about 100 pounds less than the 

Continental as installed and produces about 30 percent more power.  I 

also don't have much of an interior - no insulation.  I'd rather pay for 

Bose headphones than carry the weight of all that insulation to reduce 

noise.  (On the other hand, if you need engine maintenance on the road 

you will find it a lot easier to get experienced mechanics and parts 

than I will.)



I'm glad I decided to publish my little pilot's information page.  I 

think it helps us all.



Paul



On 6/2/2012 8:55 AM, hallert wrote:

 	  Quote: 	
		   



 Paul,

 Always find you posts useful! Just a couple of comments from a 300 hr on AMD 601 XLB driver:

 1) Do you really want to reduce pwr at 500 ft? Why not wait till safe 180 deg return altitude as many engine problems occur with change of settings.

 2) Why not drop flaps before entering pattern to allow more time to check wind, look for traffic, etc.

 3) Puzzled by yaw instability comment. Notice nothing unusual in mine based on flying Cesnas, Pipers, Mooneys, T-Craft, Gliders.

 4) You engine produces at least 6 kts. more than I get with the O-200.



 Ted Haller





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 http://forums.matronics.com/viewtopic.php?p=374538#374538

sabrina

Joined: 15 Jun 2009
Posts: 170

Posted: Sun Jun 03, 2012 10:40 am Post subject: Re: Flight test report - N773PM

Do Not Archive

Last edited by sabrina on Thu Jun 28, 2012 10:11 am; edited 1 time in total

psm(at)att.net
Guest

Posted: Sun Jun 03, 2012 11:05 am Post subject: Flight test report - N773PM

Hi Sabrina,



Thanks for the advice.  Unfortunately, I've already tried all of that 

stuff.  I did need to extend the nose gear column by 1/8 inch but that 

had little impact on the yaw stability.  I noticed the column on another 

XL at my home field had about 4 inches extending above the firewall 

shelf while mine didn't get above it at all.



After taking a close look at the whole airplane I came to the conclusion 

that this design has no inherent yaw stability.  View of the fuselage 

from the top presents a diamond shape that has no vertical surface that 

runs parallel to straight flight.  The closest it gets is a 22 degree 

included angle presented by the tail end of the fuselage.  The full 

flying rudder depends on the V-blocks in the nose gear column assembly 

to make it straight when there is no rudder pressure applied in flight.  

(I don't have wheel pants that might give a little stability.)



I did learn on early flights that the V-blocks made my plane pull a 

little to the left in flight.  I fixed that by adjusting the rudder 

cables so the rudder is straight.  I have always had my rudder cables 

tensioned according to CH's requirements.



This whole line of thought started when another list member pointed out 

that forward slips do not do anything to cause the plane to have a 

steeper approach path.  I then learned from my own plane that if I 

kicked the nose to one side or the other it didn't return to center as 

required by F2245.  At least in the case of my plane it clearly doesn't 

meet the LSA spec for stability.  I wonder what other owners find when 

trying this test.



Best regards,



Paul



On 6/3/2012 11:40 AM, Sabrina wrote:

 	  Quote: 	
		   



 Dear Paul,



 If I were to hazard a guess, your Yaw stability issue is likely due to improperly tensioned rudder cables, slightly misaligned nose gear bearings and aft CG loading.  Nothing a little adjustment, lubrication and full fuel load won't cure.



 Dear Ron,



 Congrats!



 Sabrina



 P.S. CERN has welcomed me with open arms, not to mention my best birthday party in a decade. I have accomplished a lot in just one week.  My sophomore year at MIT finished strong: http://sabrinaaerospace.com/index.php?news&nid=42





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hallert

Joined: 16 Jun 2009
Posts: 11

Posted: Sun Jun 03, 2012 1:53 pm Post subject: Re: Flight test report - N773PM

Paul,

On the yaw issue my plane is different in one regard from anything I have flown before - it has a stiff nose gear bearing that tends to stay where I push it with noticeable friction. At first I fund this somewhat annoying but now I consider it an advantage as sort of a "poor man's rudder trim". On climb out I push enough right rudder to center the ball and can then remove pedal pressure while remaining rudder trimmed. After climb out a little nudge on the left pedal corrects rudder trim for cruise.



Ted

psm(at)att.net
Guest

Posted: Sun Jun 03, 2012 2:21 pm Post subject: Flight test report - N773PM

Hi Ted,



That sounds like mine too.



You are calling that stiff rudder, I am calling it lack of yaw 

stability.  Both are true.



Paul



On 6/3/2012 2:53 PM, hallert wrote:

 	  Quote: 	
		   



 Paul,

 On the yaw issue my plane is different in one regard from anything I have flown before - it has a stiff nose gear bearing that tends to stay where I push it with noticeable friction. At first I fund this somewhat annoying but now I consider it an advantage as sort of a "poor man's rudder trim". On climb out I push enough right rudder to center the ball and can then remove pedal pressure while remaining rudder trimmed. After climb out a little nudge on the left pedal corrects rudder trim for cruise.



 Ted





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=374624#374624

DaveG601XL

Joined: 27 Oct 2006
Posts: 351
Location: Cincinnati, Oh

Posted: Mon Jun 04, 2012 8:25 am Post subject: Re: Flight test report - N773PM

Paul,



Just digging deeper into a comment you passed on about another 601XL pilot who thinks this design lacks in the forward slip arena.  What has been your experience? Personally mine drops like a rock when a forward slip is properly applied (i.e. not one of those hesitant student pilot 1" of rudder pedal slips). In fact, I usually like to come in a bit high to ensure I can make the field and then slip it to the numbers.  It's kind of fun.  



I am a midwest flat-lander and about 90% of my landings are on good sized paved runways so I rarely use flaps on approach or landing.  This means my slips are more for my own benefit as opposed to necessity.  I thought you said you were on a short strip in mountainous terrain so I figured you would have a better appreciation for slipping capabilities and steep approaches.



Just wondering...the list is a little slow so why not kick this one around,

_________________
David Gallagher
Cincinnati, OH area

psm(at)att.net
Guest

Posted: Mon Jun 04, 2012 9:10 am Post subject: Flight test report - N773PM

Hi David,

     

     Yes, I took a long hard look at slipping the XL.

     

     The first thing I found (and mentioned in a recent message) is that     there is no natural tendency for the XL to fly straight.  Put     another way there is no part of the fuselage that runs parallel to     straight flight.  The closest thing is the 22 degree angle formed by     the fuselage sides at the aft end.  This ignores any tendency for     the full flying rudder to be aligned straight ahead by the plastic     v-blocks at the bottom of the firewall.

     

     So it seems the cross section the wind sees is just about the same     when the fuselage is aligned straight ahead or +/- 11 degrees from     straight.  This suggests a slip that is less than 11 degrees to one     side or the other has no noticeable effect.  My findings in flight     test agree with this theory.  If you do a deep slip where the nose     is more than 11 degrees off center then you will see increased drag     - just as you indicated.

     

     This is one of two flight characteristics resulting from the poor     combination (in my opinion) of having no vertical stabilizer and no     straight ahead sections of the fuselage.  The other one is there is     little or no yaw stability in straight and level flight.  Within the     +/- 11 degrees of straight this design has no natural tendency to     straighten out when the yaw position is upset (as required by ASTM     standard F2245).  This is only a problem for S-LSA or E-LSA planes     that are supposed to conform to this standard.  E-AB planes can be     anything the builder wants, but the claim I heard when I chose this     design was that it conformed to the standard.

     

     I added strakes to the fuselage bottom on my plane in an attempt to     deal with this problem.  It helped a little but didn't reach the     point of making it stable in yaw.  However, it did make it a little     happier when flying straight and also had the effect of making small     slips effective in making small increases in approach angle.  I have     found I like to use small slips either with or without flaps     deployed to make the touchdown point a little shorter when my     approach is a bit long.

     

     I circulated pictures of my strakes a few months ago, but here are     some pictures:

     

     

     [img]cid:part1.06000205.04040605(at)att.net[/img]

     

     

     [img]cid:part2.07010304.04020000(at)att.net[/img]

     

     The single piece is made from .050 aluminum and the sides are     misaligned (but balanced) so the air flowing over them keeps them     pressed against the air flow.  That way a small change in airflow     increases the drag rather than causing the strakes to bend at     first.  The piece is attached to the bottom longerons using     pre-existing rivet holes.

     

     Let me point out that I am not a qualified aviation engineer.  That     means you can copy my design but you should not think it is properly     engineered.  You do so at your own risk.

     

     My home field is reasonably long but has threshold displacements at     both ends.  The surrounding terrain is hilly so the winds are always     swirling.  We have three wind socks - one at each end and one in the     middle of the runway - and they never point in the same direction.       I almost miss those consistent cross winds that always seem to be     haunting those mid-west runways.  I spent several years flying in     that area when I was stationed at SAC HQ near Omaha, Nebraska.

     

     Best regards,

     

     Paul

     

     On 6/4/2012 9:25 AM, DaveG601XL wrote:      	  Quote: 	
		          	  Quote: 	
		  --> Zenith601-List message posted by: "DaveG601XL" <david.m.gallagher(at)ge.com> (david.m.gallagher(at)ge.com)



Paul,



Just digging deeper into a comment you passed on about another 601XL pilot who thinks this design lacks in the forward slip arena.  What has been your experience? Personally mine drops like a rock when a forward slip is properly applied (i.e. not one of those hesitant student pilot 1" of rudder pedal slips). In fact, I usually like to come in a bit high to ensure I can make the field and then slip it to the numbers.  It's kind of fun.  



I am a midwest flat-lander and about 90% of my landings are on good sized paved runways so I rarely use flaps on approach or landing.  This means my slips are more for my own benefit as opposed to necessity.  I thought you said you were on a short strip in mountainous terrain so I figured you would have a better appreciation for slipping capabilities and steep approaches.



Just wondering...the list is a little slow so why not kick this one around,



--------

David Gallagher

Zodiac 601 XL-B: flying, 200+ hours now

Next project under construction: Aircamper

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Mon Jun 04, 2012 1:56 pm Post subject: Flight test report - N773PM

I found on my plane that there is a significant decrease in rudder cable tension with weight on the nose wheel as apposed to no weight on the nose-wheel. The attachment point for the nose-wheel steering rods moves a bit closer to the tail as the bungee is compressed due to the geometry of the firewall. I now make sure to set the tension with the nose jacked up just enough to take the weight off. This is the "in-flight" condition and results in the highest cable tension. This noticeably reduced the force needed on the rudder pedals.



-- 

Bryan Martin

N61BM, CH 601 XL, 

RAM Subaru, Stratus re-drive.

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

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Mon Jun 04, 2012 1:58 pm Post subject: Flight test report - N773PM

As does mine.



On Jun 4, 2012, at 11:25 AM, DaveG601XL wrote:



 	  Quote: 	
		   

 

 

 Personally mine drops like a rock when a forward slip is properly applied (i.e. not one of those hesitant student pilot 1" of rudder pedal slips).


	




-- 

Bryan Martin

N61BM, CH 601 XL, 

RAM Subaru, Stratus re-drive.

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

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