Matronics Email Lists :: View topic - A Note About Moding G's instead of Weight

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

A Note About Moding G's instead of Weight
Goto page 1, 2 Next

Matronics Email Lists Forum Index -> Zenith-List

View previous topic :: View next topic

Author Message

Gig Giacona

Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA

Posted: Fri Jul 10, 2009 12:48 pm Post subject: A Note About Moding G's instead of Weight

The following was written by Andy Elliot and posted on the Zenith Aircraft Builder's & Flyer's forum. Since he doesn't post to this list any more he gave me permission to post this here.



Planes obey the laws of physics like nearly everything else. It is not just the weight of the plane that produces flight loads, it is the weight x G loading. So if the plane's design somehow suddenly became weaker (which seems illogical), and now is limited to +4 G's at 1255#, you could still safely fly it at 1320# if you limit yourself to just +3.8 G's. Not so bad, eh?



In fact, I certified my 601XL (non-LSA) to 1450# max gross weight, but at reduced G limits of +3.6, -1.6. Not much of a restriction in my book, and I tested the gear (Grove) at the higher weight during Phase 1 and found it acceptable. A PDF copy of the flight load limit diagram that appears in my POH is attached.



For reference, I am also attaching the CG most forward and max aft limit pages from my POH, which show how the CG range also changes at various weights. You should have, or will be, required by your DAR to produce similar diagrams for your plane for certification.



As for the 140 MIAS VNE change, well if that effects you directly, Congratulations!



The net result is that if you fly the plane within its limits, either old or "temporarily recommended" you still have a highly useful machine.



Andy Elliott

N601GE/ TD / Corvair

_________________
W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR

ihab.awad(at)gmail.com
Guest

Posted: Fri Jul 10, 2009 1:09 pm Post subject: A Note About Moding G's instead of Weight

On Fri, Jul 10, 2009 at 1:48 PM, Gig Giacona<wrgiacona(at)gmail.com> wrote:

 	  Quote: 	
		   Planes obey the laws of physics like nearly everything else. It is not just the

 weight of the plane that produces flight loads, it is the weight x G loading.


	


Yes, but gusts and turbulence may impose a G loading on your aircraft

that is independent of your control inputs. For example, would you

also not need to reduce your Va?



Ihab



ps "Nearly" everything? *Nearly*? Hmmm.... 



-- 

Ihab A.B. Awad, Palo Alto, CA

craig(at)craigandjean.com
Guest

Posted: Fri Jul 10, 2009 1:37 pm Post subject: A Note About Moding G's instead of Weight

Things which do not obey the laws of physics:



- Wile E. Coyote

- my bank account

- nearly everything in Sci-Fi movies



-- Craig



Do not archive



--

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Fri Jul 10, 2009 1:47 pm Post subject: Re: A Note About Moding G's instead of Weight

I asked Andy about changing limit speeds and he agreed there should be a reduction to Va

Actually this subject is more complicated dependent on which category of operation the aircraft is registered for.



In New Zealand CH601, HD and XL  and CH701 are only eligible to be registered as a microlight if they comply with the design rules of Canadian Advanced Ultralight spec. TC10141E (now DS10141E) or the British BCAR-S which is a more stringent rule. Both these design rules require flutter testing which it seems the LSA (ASTM) does not.

These aircraft cannot be modified without designer approval and must continue to comply with the design rules subsequent to any modification.

The DS10141E spec includes a clause requiring design limit load of not less than 4G. I have no idea what the ASTM allows for LSA because that information is not publicly available.

Therefore if you were to operate over the design gross there would need a restriction on the various limit airspeeds Vfe, Vc, Va, Vne ?  

Most countries would only allow operations above design gross wt. if the aircraft was being operated in Experimental category and the test pilot had proved it safe.

Ralph

_________________
Ralph - CH701 / 2200a

psm(at)att.net
Guest

Posted: Fri Jul 10, 2009 2:43 pm Post subject: A Note About Moding G's instead of Weight

Hi Ralph,



Oddly, it has been common practice in my flying experience to nearly 

always fly some planes over the MTOW.  I don't know the formal 

treatment of this question, but the informal treatment I have heard 

from several instructors suggests the FAA's version of MTOW is 

ultra-conservative and should only be considered a serious limit at 

high density altitudes.



The prime example of this issue is the Cessna 150.  Many of us 

learned to fly with dual instruction in this humble plane.  When it 

carries two adult males it is almost certainly a couple of hundred 

pounds over gross weight.  It still flies just fine, but the climb 

rate is very low.  Even solo with a teenager at the controls the 

climb rate on this fine old plane is not very impressive.



Historically, I have always considered CG to be a much more important 

specification than gross weight.  Of course this thinking only works 

if you fly the plane gently.  (On the other hand, all the aerobatic 

maneuvers I learned were done with two adults in a C-152 . . .).



I don't know about Vne, Va or other performance limits.  From my 

point of view these only come into play when you fly the plane in 

very harsh conditions or with a very heavy hand on the stick or throttle.



Paul

XL grounded

At 02:47 PM 7/10/2009, you wrote:

 	  Quote: 	
		  Most countries would only allow operations above design gross wt. if 

the aircraft was being operated in Experimental category and the 

test pilot had proved it safe.

Ralph

Juan Vega Jr

Joined: 13 Jan 2009
Posts: 157

Posted: Fri Jul 10, 2009 2:54 pm Post subject: A Note About Moding G's instead of Weight

Paul,

Ignoring MTOW is playing Russian roullette.  PLay at your own peril. 

Juan



--

psm(at)att.net
Guest

Posted: Fri Jul 10, 2009 3:06 pm Post subject: A Note About Moding G's instead of Weight

OK, Juan.  I'll bite.



What outcome would you expect from flying over gross weight?



We all know it will reduce the climb rate.  We also know that Va 

increases with increased weight.  This would seem to suggest that 

structure failures are less likely with excess weight rather than 

more likely (the plane is more likely to stall than sustain high G's).



So, what is the big problem with excess weight?



Paul

do not archive



At 03:52 PM 7/10/2009, you wrote:

 	  Quote: 	
		  Paul,

Ignoring MTOW is playing Russian roullette.  PLay at your own peril.

Juan

n801bh(at)netzero.com
Guest

Posted: Fri Jul 10, 2009 3:25 pm Post subject: A Note About Moding G's instead of Weight

My Zenith is an" EXPERIMENTAL".. I can make my MTOW 10,000  lbs if I want. 

do not archive. 

Ben Haas

N801BH

www.haaspowerair.com



--------

Juan Vega Jr

Joined: 13 Jan 2009
Posts: 157

Posted: Sat Jul 11, 2009 5:39 am Post subject: A Note About Moding G's instead of Weight

Paul,

your shitting me right?

Juan



--

Juan Vega Jr

Joined: 13 Jan 2009
Posts: 157

Posted: Sat Jul 11, 2009 6:09 am Post subject: A Note About Moding G's instead of Weight

Ladies,



I am headed to Wickee Wachee SPrings with the Kids,  in the Mean Time,  chew on this piece from a n article from Mr. McGee. It starts on the basics of Overweight  issues on a lite  wing loaded aircraft.  Very Basic info but to the point. 

ASk your self  the questions after you read it,"do I want to deal with an over maxed aircraft, and do I have the hours flown to understand how the plane will behave at manuvering speeds at over gross"  "WHat is my new stall speeds?".

As quoted from an article by Art Mcgee;



Aside from building a light plane, there is another option to achieve a reasonable useful load. Under the FAA's Amateur Built Experimental aircraft guidelines, the manufacturer (the builder) sets the gross weight of the aircraft. With this flexibility you can increase the maximum gross weight to more than 800lbs. Although the builder can assign any weight he feels appropriate, when doing so he should keep in mind the original design load and the G load factor used to determine the designed gross weight.



As you increase your gross weight, you must decrease the G rating of the aircraft to keep from going over the design load of the aircraft. With this in mind, let's go back to the information provided earlier about G rating, gross weight and design load.



If you are willing to reduce your G ratings and use more precautions in rough conditions, then you can increase your gross weight. Let's look back to the example airplane. The gross weight was 800 lbs. and the empty weight was 472-lbs. and left room after pilot fuel, and oil for 117.2 lbs. of passenger. If I were to increase the gross weight to 900 pounds that would give me room for a 217.2-pound passenger, which would give more flexibility in passengers. 



I knew that if I lowered the maximum G ratings for my plane, that would increase my gross weight. If you take the positive design load of 4800 lbs. and divide it by the new maximum G rating of +5, that would give a gross weight of 960 lbs. If you take the negative design load of 2400 lbs. and divide it by 960lbs, you get a G rating of -2.5G's.



This change leaves a fairly large margin of safety in turbulence and also gives some increased utility since there is now a higher gross weight. This change would now give me room for a passenger who weighed 277.2 pounds and would allow me to carry anyone that I know who would want to fly. Increasing the gross weight does not come without its drawbacks though. 



The Down Side to Increasing Gross Weight

Like anything else in aviation, a gain in one place means a loss in another place. There are some things to consider when raising the gross weight. Among those things are decreased performance, increased fuel consumption, possible center of gravity problems, and, of course, decreased G ratings.



Because of the higher gross weight, the take-off distance, landing distance and stall speed will be increased and the climb rate will decrease. The pilot will have to be aware of the G ratings when flying in turbulence and when doing â€œyank and bankâ€ flying. The pilot will have to remember when flying at the increased weight to slow down more in turbulence and be easier on the controls. He will also need to remember that stall speed will be higher and it will take more distance to take off and land.



He will also have to pay more attention to the center of gravity. The Challenger has a wide center of gravity envelope, but all of the weight that is placed in the cockpit moves the CG forward. With higher payloads, you may go past the forward limit for center of gravity. The good news is that if you are flying solo, then you are most likely below 800 pound gross weight flying a plane with a designed +6 and -3G range.





--

rene(at)felker.com
Guest

Posted: Sat Jul 11, 2009 6:15 am Post subject: A Note About Moding G's instead of Weight

Juan, I don't think he is.....



For my RV-10, I added 100lbs to my gross weight after looking at the numbers.  Had an AE look at it and in the end had to reduce my max G loading by .2 G's at the new gross weight.  I tested at that weight to include aft C/G....could not test forward CG "limit" since there is no way of getting up on the forward with that much weight.  The only real concern I had was with the gear and what affect the 100 lbs would have.  But since I would not be landing at the gross weight and since in almost all scenarios it is nearly impossible to load to max and keep it there, I accepted that risk. 



Rene' Felker

RV-10 N423CF Flying

801-721-6080

--

psm(at)att.net
Guest

Posted: Sat Jul 11, 2009 6:17 am Post subject: A Note About Moding G's instead of Weight

Hi Juan,



No.  I am being completely serious.  I really believe the impact of 

being over gross weight is predictable and reasonably safe.  There 

are obvious impacts to required runway length and climb rates, but 

for the most part a small excess of weight results in a small 

reduction in performance.



Of course, this assumes that the CG for the plane is still within 

normal limits.



My understanding of the FAA regs on this matter is that the pilot is 

required to be aware of the weight situation but he is not required 

to remain within the weight specified on the aircraft 

documents.  Indeed the MTOW specified in the documents is totally 

arbitrary - based on a set of conditions that may or may not be the 

ones faced for a given flight.



I still await your answer about what happens if you are over gross 

weight.  (Keep in mind that this happens every day on some aircraft 

like the C-150, and will probably also happen on most dual flights of 

the new C-162).



Paul

XL grounded

do not archive

At 06:37 AM 7/11/2009, you wrote:

[quote]



Paul,

your shitting me right?

Juan



--

jmaynard

Joined: 27 Feb 2008
Posts: 394
Location: Fairmont, MN (FRM)

Posted: Sat Jul 11, 2009 6:25 am Post subject: A Note About Moding G's instead of Weight

On Sat, Jul 11, 2009 at 07:13:34AM -0700, Paul Mulwitz wrote:

 	  Quote: 	
		   My understanding of the FAA regs on this matter is that the pilot is 

 required to be aware of the weight situation but he is not required to 

 remain within the weight specified on the aircraft documents.


	


..except for an LSA, which may not be operated contrary to the

amnufacturer's instructions. The POH carries the force of law for an LSA.

-- 

Jay Maynard, K5ZC, PP-ASEL, CFI-SP   http://www.conmicro.com

http://jmaynard.livejournal.com       http://www.tronguy.net

Fairmont, MN (KFRM)                        (Yes, that's me!)

AMD Zodiac CH601XLi N55ZC http://www.tronguy.net/N55ZC.shtml

_________________
Jay Maynard, K5ZC
AMD Zodiac XLi N55ZC

psm(at)att.net
Guest

Posted: Sat Jul 11, 2009 6:39 am Post subject: A Note About Moding G's instead of Weight

Hi Juan,



I agree with everything said in your quoted article except for the 

turbulence comment.  I'm afraid the author got this point backwards.



Increasing actual gross weight increases Va rather than decreasing 

it.  So, in theory, you could fly faster in the same turbulence with 

more gross weight rather than needing to fly slower.



OK, it is a small point.  The simple answer for most pilots in most 

conditions is to keep under gross weight specified in the airplane's 

documents.  However, I still believe flying over gross weight can be 

done safely, and legally, in some planes under some conditions.



Paul

do not archive

At 07:08 AM 7/11/2009, you wrote:

 	  Quote: 	
		  The pilot will have to remember when flying at the increased weight 

to slow down more in turbulence

carlossa52(at)gmail.com
Guest

Posted: Sat Jul 11, 2009 6:39 am Post subject: A Note About Moding G's instead of Weight

Folks, there is a pertinent article in Flying (July 2009), page 32, by Peter Garrison: "Aftermath / the myth of gross weight", which you can read here: 

http://www.flyingmag.com/accidents/1593/the-myth-of-gross-weight.html

 



Carlos



2009/7/11 Paul Mulwitz <psm(at)att.net (psm(at)att.net)>

[quote] --> Zenith-List message posted by: Paul Mulwitz <psm(at)att.net (psm(at)att.net)>

 



 Hi Juan,

 

 No.  I am being completely serious.  I really believe the impact of being over gross weight is predictable and reasonably safe.  There are obvious impacts to required runway length and climb rates, but for the most part a small excess of weight results in a small reduction in performance.

 [b]

psm(at)att.net
Guest

Posted: Sat Jul 11, 2009 6:47 am Post subject: A Note About Moding G's instead of Weight

Hi Jay,



This is a very interesting distinction.



I wonder how the C-162 will be certified.  It seems if it is 

certified under part 23 you can do dual instruction in it but if it 

is certified as S-LSA you can't do dual legally.  If I remember 

correctly from my original calculations with full fuel and a normal 

adult in one seat the other one will have to weigh 50 pounds or so to 

stay under MTOW.



Paul

do not archive

At 07:24 AM 7/11/2009, you wrote:

 	  Quote: 	
		  



On Sat, Jul 11, 2009 at 07:13:34AM -0700, Paul Mulwitz wrote:

 > My understanding of the FAA regs on this matter is that the pilot is

 > required to be aware of the weight situation but he is not required to

 > remain within the weight specified on the aircraft documents.



...except for an LSA, which may not be operated contrary to the

amnufacturer's instructions. The POH carries the force of law for an LSA.

--

arno7452(at)bellsouth.net
Guest

Posted: Sat Jul 11, 2009 7:05 am Post subject: A Note About Moding G's instead of Weight

Over time, it has been proffered that inane speculation often subtracts from 

the sum total of human intelligence.



Regards,

Ken



do not archive

vayuwings

Joined: 12 Dec 2008
Posts: 16
Location: arizona

Posted: Sat Jul 11, 2009 1:10 pm Post subject: Re: A Note About Moding G's instead of Weight

'Over time, it has been proffered that inane speculation often subtracts from 

the sum total of human intelligence.'



Hmm... making the assumptive leap that 'human intelligence' is not a conflict in terms, and those doing the proffering are proven by all to be the Wise, methinks speculation of any sort can be classified either as inane or not - praytell, whom dost say whether inane or not?

  

so as the river winding to the sea is never direct, but flows inanely across the land to the ocean.....



Let it flow and enjoy the shore a bit, eh? just might find a cove of great surprise



Dave

601XL 

building temporarily frozen in the phoenix heat

jlatimer1(at)cox.net
Guest

Posted: Sat Jul 11, 2009 1:43 pm Post subject: A Note About Moding G's instead of Weight

 	  Quote: 	
		   Dave

 601XL 

 building temporarily frozen in the phoenix heat


	


My garage temperature was over 120.  Outside temp just over 113.

Also waiting for heat to subside.

Jerry

Juan Vega Jr

Joined: 13 Jan 2009
Posts: 157

Posted: Sat Jul 11, 2009 2:58 pm Post subject: A Note About Moding G's instead of Weight

Dave,

Put down the Bong and get back to building:)



Juan



--

Display posts from previous:

	Matronics Email Lists Forum Index -> Zenith-List	All times are GMT - 8 Hours Goto page 1, 2 Next
Page 1 of 2

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