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Kurt.Schumacher(at)schumi
Guest
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 Posted: Fri May 11, 2007 2:53 pm Post subject: Ultimate Load vs. Limit Load |
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Dear friends,
Somewhat wondering about the mentioned +-6G for the CH 601 HDS quoted here
on the list here these hours. Ok, the
http://www.zenithair.com/zodiac/601-hds.html says for the Super ZODIAC CH
601 HDS (lower table, full MTOM)
DESIGN LOAD FACTOR (ultimate) +/- 6 "G"
Here what JAR 23 / FAR 23 define for limit and ultimate load:
..limit loads are the maximum loads to be expected in service [i.e. the
highest load expected in normal operations] and ultimate loads are limit
loads multiplied by a safety factor [of 1.5]. The structure must be able to
support limit loads without detrimental, permanent deformation. At any load
up to limit loads, the deformation may not interfere with safe operation.
The structure must be able to support ultimate loads without failure for at
least three seconds...
Let us now extend ZAC datasheet accordingly:
DESIGN LOAD FACTOR (ultimate) +/- 6 "G"
SUSTAINED LOAD FACTOR (limit) +/- 4 "G"
Aha. This looks different now. The CH 601 HDS is for sure not an aerobatic
category aircraft (starts at +6.0/-4.0 limit load) - despite whatever
maneuvers seen on Youtube. Then, it is cannot qualified to the utility
category, e.g. training aircraft with spin certification (+4.4/-2.2 limit
load). The same is true for other 601 models; the 601 XL comes with similar
numbers. All 601 models are excellent standard category aircraft if operated
well within the limits.
Please review your aircraft OPS manual, Pilot's Manual - and correct
accordingly in case only ultimate numbers are printed.
What does this mean to you as a customer - and then to you as the pilot in
command?
Correct: You never exceed the sustained limit load factor in flight! The
safety factor is _really_ used to cover additional gust loads and is not
available to the pilot control inputs, e.g. when a G meter is available.
Everything beyond limit load can (and often will) lead to detrimental,
permanent deformation. This will not make you falling from the skies yet.
However, if you _are_ going to ultimate load, there are probably just three
seconds left up there, plus some more to follow the other 9.81 m/s2 always
in place. However, in this case you do better arrange a structural engineer
to review your plane.
Then, please keep in mind that the sustained load factor only applies to a
factory new airplane. Any repairs, ageing, unreported and unrecorded abuse,
and poor maintenance - to which an aircraft has been exposed since leaving
the factory - may (and will) decrease the strength, the structural integrity
at least considerably.
This is aviation standard, not related to the pilots age or license - and
not limited to Chris Heintz' designs.
Fly safe!
-Kurt.
SportAviation of Switzerland
www.sportaviation.ch
EAS Webmaster (Experimental Aviation of Switzerland)
www.experimental.ch
PS. On behalf of the EAS we have witnessed the stress test on the new CZAW
SportCruiser, done earlier this year under the engineering guidance of the
British PFA following a CS-VLA process to qualify as a kit plane in the UK,
and subsequently in many other European countries. The same happened to
various extents over the last eight years with the Chris Heintz designed
aircraft - many pictures shown at the ZAC have been taken in the Czech
Republic.
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pilot4pay
Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY
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| Posted: Fri May 11, 2007 5:18 pm Post subject: Ultimate Load vs. Limit Load |
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Thank you for bringing some rational and factual information to this long
misunderstood and misquoted engineering quality.
The other interesting aspect of this thread is how one day certain people
(Not poster Kurt) say they can do anything they want with an experimental
aircraft, a few weeks later and they're all about design standards and
limitations. Now lets try to keep the discussion in the realm of adult
discourse, not childish sarcasm and personal attacks.
CS
--
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_________________
Craig Smith
CH640 builder
SN: 0078
"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin |
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bryanmmartin
Joined: 10 Jan 2006
Posts: 1018
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| Posted: Fri May 11, 2007 7:14 pm Post subject: Ultimate Load vs. Limit Load |
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Technically, the 601 series won't qualify for the normal category either
since it will have either an Experimental Amateur Built airworthiness
certificate or one or the LSA certificates. The normal, utility, and
aerobatic categories only apply to an aircraft with a normal
airworthiness certificate. But it is correct to say that the 601 has
flight load limits somewhere in between those for a normal and utility
category aircraft.
That being said, you make a very good point about the safe operation of
the 601 series. I cringe inside every time I read a post that asserts
that the 601 is rated for 6 Gs and then compares this favorably with
aerobatic aircraft. There is a lot of confusion about this subject
because factory built aircraft operating handbooks generally state the
load limit in terms of the flight load factor but it is common practice
in the homebuilt industry to state the load limit in terms of the design
load factor. I hope your post helps clear up some of the confusion.
Kurt A. Schumacher wrote:
| Quote: |
Dear friends,
...
DESIGN LOAD FACTOR (ultimate) +/- 6 "G"
SUSTAINED LOAD FACTOR (limit) +/- 4 "G"
Aha. This looks different now. The CH 601 HDS is for sure not an aerobatic
category aircraft (starts at +6.0/-4.0 limit load) - despite whatever
maneuvers seen on Youtube. Then, it is cannot qualified to the utility
category, e.g. training aircraft with spin certification (+4.4/-2.2 limit
load). The same is true for other 601 models; the 601 XL comes with similar
numbers. All 601 models are excellent standard category aircraft if operated
well within the limits.
...
|
--
Bryan Martin
Zenith 601XL N61BM
Ram Subaru, Stratus redrive
Do Not Archive
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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive. |
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Martin Pohl
Joined: 30 Jan 2006
Posts: 118
Location: CH-8645 Jona SG, Switzerland
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| Posted: Sat May 12, 2007 3:43 am Post subject: Re: Ultimate Load vs. Limit Load |
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Kurt, thank you for clarification of the difference between limit and ultimate/design load! It seems that not all of the builders are totally aware of this...
Some more thoughts (and a refresher) about structural loads and airspeeds, primarily maneuvering speed (va):
* We all know that - at va - the load on the airframe can just reach limit load (e.g. 4g for CH601XL) before the aircraft stalls (and that is for max weight, lower weights result in lower va!).
* For higher speeds a much higher load can result before the aircraft stalls.
* Example: va = 95kts (common va for CH601XL at MTOW), then fly with v = 120kts, pull very hard on the stick and you will see a load of 6.4g before you get an accelerated stall (well, perhaps you will first hear cracks developing in your spar...). Do the same at v = 130kts and the airplane could aerodynamically make 7.5g!!!
There was a very good article in one of last years' "AOPA Pilot "written by Rod Machado about the importance of maneuvering speed.
Knowledge of maneuvering speed is especially important to us pilots of light sport aircraft, because va is rather low/slow. For comparison the Cessna C-152 has a va = 104kts at MTOW, but its cruise speed characteristics are very similar to (or even worse than) our CH601XL!!! Therefore in a C-152 you would not run that quickly into structural problems even if the air is getting rough...
Cheers Martin
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_________________
Martin Pohl
Zodiac XL QBK
8645 Jona, Switzerland
http://www.pohltec.ch/ZodiacXL/Main.html |
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Terry Phillips
Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT
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| Posted: Sat May 12, 2007 11:43 am Post subject: Ultimate Load vs. Limit Load |
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|
Kurt
Thank you for a very clear concise explanation of 601 design load factors.
That info is really helpful.
Terry
At 12:50 AM 5/12/2007 +0200, you wrote:
| Quote: | Dear friends,
Somewhat wondering about the mentioned +-6G for the CH 601 HDS quoted here
on the list here these hours. Ok, the
http://www.zenithair.com/zodiac/601-hds.html says for the Super ZODIAC CH
601 HDS (lower table, full MTOM)
DESIGN LOAD FACTOR (ultimate) +/- 6 "G"
Here what JAR 23 / FAR 23 define for limit and ultimate load:
...limit loads are the maximum loads to be expected in service [i.e. the
highest load expected in normal operations] and ultimate loads are limit
loads multiplied by a safety factor [of 1.5]. The structure must be able to
support limit loads without detrimental, permanent deformation. At any load
up to limit loads, the deformation may not interfere with safe operation.
The structure must be able to support ultimate loads without failure for at
least three seconds...
Let us now extend ZAC datasheet accordingly:
DESIGN LOAD FACTOR (ultimate) +/- 6 "G"
SUSTAINED LOAD FACTOR (limit) +/- 4 "G"
Aha. This looks different now. The CH 601 HDS is for sure not an aerobatic
category aircraft (starts at +6.0/-4.0 limit load) - despite whatever
maneuvers seen on Youtube. Then, it is cannot qualified to the utility
category, e.g. training aircraft with spin certification (+4.4/-2.2 limit
load). The same is true for other 601 models; the 601 XL comes with similar
numbers. All 601 models are excellent standard category aircraft if operated
well within the limits.
Please review your aircraft OPS manual, Pilot's Manual - and correct
accordingly in case only ultimate numbers are printed.
What does this mean to you as a customer - and then to you as the pilot in
command?
Correct: You never exceed the sustained limit load factor in flight! The
safety factor is _really_ used to cover additional gust loads and is not
available to the pilot control inputs, e.g. when a G meter is available.
Everything beyond limit load can (and often will) lead to detrimental,
permanent deformation. This will not make you falling from the skies yet.
However, if you _are_ going to ultimate load, there are probably just three
seconds left up there, plus some more to follow the other 9.81 m/s2 always
in place. However, in this case you do better arrange a structural engineer
to review your plane.
Then, please keep in mind that the sustained load factor only applies to a
factory new airplane. Any repairs, ageing, unreported and unrecorded abuse,
and poor maintenance - to which an aircraft has been exposed since leaving
the factory - may (and will) decrease the strength, the structural integrity
at least considerably.
This is aviation standard, not related to the pilots age or license - and
not limited to Chris Heintz' designs.
Fly safe!
-Kurt.
|
Terry Phillips
ttp44~at~rkymtn.net
Corvallis MT
Just starting a 601 kit
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings. |
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