 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
Discover
Joined: 26 Feb 2007
Posts: 429
|
 Posted: Fri Jan 04, 2008 6:52 am Post subject: Dive Tests |
 |
|
Gary,
Will an FAA representative be in teh plane with you when you dive it 240 mph
Are you concerned a little about it? We don't want to lose you over some
insidious FAA CYA program.
Here are some comments Fred Kokaska made to me about his dive testing:
".....
In CFR Part 23 certification the term TAS is never defined, recognized or
addressed. They have V speed numbers for everything but all testing,
structural flight testing, climb/cooling flight testing are all related to
IAS.
They will require a correction chart be developed for installation error of
the pitot tube so that test result data is really based on CAS after
observed temp and installation errors are accounted for.
A manufacturer of a new design must define and demonstrate (Vd) (Dive speed
as part of the overall envelope) After demonstrating a dive at Vd the FAA
established Vne (AA5B 174 KCAS) as 90% of demonstrated Vd (FAA takes away
10% as a safety factor) . I went through the Vne part of certification at
100% of Vne for an AA5B (174 KIAS), There were two Part 23 objectives in
this flight test (flown by FAA test pilot) of verifying the prop does not
overspeed (above 2700 RPM) at Vne. This was easy as the back stop in the CS
prop would probably allow 220 KIAS before it ran out of pitch. On a fixed
pitch prop this can be a show stopper and require reducing Vne to prevent
the overspeed. The other was pitch and roll control and airframe vibration.
The test pilot started at 10 K feet and pushed over at full power to
establish 174 KIAS, did some 30 degree left and right rolling maneuvers. He
commented (and I looked out the right side) on the fact the ailerons were
both about 2 inches above the normal even with the flap position in level
flight from airloads. While this looks spooky, he noticed no binding or
control input problems that he did not like.
So, to answer your question .... I have never seen any reference to the term
"TAS" in any certification requirement.
Sombody ought to follow up with the FAA to get the right A/S marking in the
2400 Lb Cheetahs that have the AA5B spar installed. They approved AA5B
airspeed markings for the spar upgrade in Peter Otten's IO-360 STC so you
have an approved example.
Cheers Fred Kokaska"
Stay safe,
Ned
| Quote: | For-what-it's-worth: B The FAA is making me do carb heat rise tests on my
new
cowling. B My cowling has in no way affected the source, path, or
operation of
the carb heat. B Their argument: B Since I "MAY" have changed the air
pressure
in the lower cowling, I "MAY" have changed the operation of carb heat. B
SO .
. . B I tested a stock Tiger. B It doesn't pass the test. B I tested a
stock
Tiger with a Power Flow. B It doesn't pass the test either (by 4 degrees).
B Testing on my new cowling starts as soon as it stops raining.
I also have to dive the plane to 240 mph. B But, that's a different story.
B
|
| | - The Matronics TeamGrumman-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?TeamGrumman-List |
|
|
|
| Back to top |
|
 |
az_gila
Joined: 17 Jun 2006
Posts: 99
Location: Tucson, AZ
|
| Posted: Fri Jan 04, 2008 7:37 am Post subject: Dive Tests |
|
|
Ned... the FAA might only use IAS for testing, but they can change Vne with altitude (essentially correcting it back to TAS).
The FAA paperwork to certify my Mini-Nimbus sailplane shows this...
Page 4 of the pilots manual supplement has a Vne correction for altitude...
http://www.schempp-hirth.com/fileadmin/tmdocs/328-6-1427.pdf
The correction reduces the IAS for Vne from 135 kts to 120 kts at 19,700 ft
I never bothered certifying my glider (only one in the US did, and it's a rental) since my operating limitations are so lax, Experimental, Exhibition and Racing is better...
gil A
At 07:50 AM 1/4/2008, you wrote:
[quote]--> TeamGrumman-List message posted by: "923te" <923te(at)cox.net>
Gary,
Will an FAA representative be in teh plane with you when you dive it 240 mph
Are you concerned a little about it? We don't want to lose you over some insidious FAA CYA program.
Here are some comments Fred Kokaska made to me about his dive testing:
".....
In CFR Part 23 certification the term TAS is never defined, recognized or addressed. They have V speed numbers for everything but all testing, structural flight testing, climb/cooling flight testing are all related to IAS.
They will require a correction chart be developed for installation error of the pitot tube so that test result data is really based on CAS after observed temp and installation errors are accounted for.
A manufacturer of a new design must define and demonstrate (Vd) (Dive speed as part of the overall envelope) After demonstrating a dive at Vd the FAA established Vne (AA5B 174 KCAS) as 90% of demonstrated Vd (FAA takes away 10% as a safety factor) . I went through the Vne part of certification at 100% of Vne for an AA5B (174 KIAS), There were two Part 23 objectives in this flight test (flown by FAA test pilot) of verifying the prop does not overspeed (above 2700 RPM) at Vne. This was easy as the back stop in the CS prop would probably allow 220 KIAS before it ran out of pitch. On a fixed pitch prop this can be a show stopper and require reducing Vne to prevent the overspeed. The other was pitch and roll control and airframe vibration. The test pilot started at 10 K feet and pushed over at full power to establish 174 KIAS, did some 30 degree left and right rolling maneuvers. He commented (and I looked out the right side) on the fact the ailerons were both about 2 inches above the normal even with the flap position in level flight from airloads. While this looks spooky, he noticed no binding or control input problems that he did not like.
So, to answer your question .... I have never seen any reference to the term "TAS" in any certification requirement.
Sombody ought to follow up with the FAA to get the right A/S marking in the 2400 Lb Cheetahs that have the AA5B spar installed. They approved AA5B airspeed markings for the spar upgrade in Peter Otten's IO-360 STC so you have an approved example.
Cheers Fred Kokaska"
Stay safe,
Ned
| Quote: | For-what-it's-worth: B The FAA is making me do carb heat rise tests on my new
cowling. B My cowling has in no way affected the source, path, or operation of
the carb heat. B Their argument: B Since I "MAY" have changed the air pressure
in the lower cowling, I "MAY" have changed the operation of carb heat. B SO .
. . B I tested a stock Tiger. B It doesn't pass the test. B I tested a stock
Tiger with a Power Flow. B It doesn't pass the test either (by 4 degrees).
B Testing on my new cowling starts as soon as it stops raining.
I also have to dive the plane to 240 mph. B But, that's a different story. B
|
===========
TeamGrumman-List Email Forum -
http://www.matronics.com/Navigator?TeamGrumman-List
===========
; - MATRONICS WEB FORUMS -
http://forums.matronics.com
===========
; - List Contribution Web Site -
; -Matt Dralle, List Admin.
http://www.matronics.com/contribution
===========
[b]
| | - The Matronics TeamGrumman-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?TeamGrumman-List |
|
|
|
| Back to top |
|
|
flyv35b(at)minetfiber.com
Guest
|
| Posted: Fri Jan 04, 2008 8:04 am Post subject: Dive Tests |
|
|
Vne on a Tiger is 200 mph. Vd would be 222 mph or 200/.9=222. Why the 240 mph. Don't think I would be inclined to go that high!
Cliff
[quote] ---
| | - The Matronics TeamGrumman-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?TeamGrumman-List |
|
|
|
| Back to top |
|
|
GrummanDude
Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA
|
| Posted: Mon Jan 07, 2008 8:50 pm Post subject: Dive Tests |
|
|
Remember how when we were in grade school and the teacher whispered something into one person's ear and then that person whispered it into another person's ear and then the last kid was asked to repeat what was said? Â
Where did True Airspeed come from?
Vne has nothing to do with TAS. Â
The FAA wants a dive test to Vne + 20%. Â We've petitioned for Vne + 10%
| | - The Matronics TeamGrumman-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?TeamGrumman-List |
|
_________________
Gary
AuCountry Aviation
Home of Team Grumman |
|
| Back to top |
|
|
az_gila
Joined: 17 Jun 2006
Posts: 99
Location: Tucson, AZ
|
| Posted: Mon Jan 07, 2008 9:45 pm Post subject: Dive Tests |
|
|
Gary... I have an old, but very interesting FAA document "Basic Glider Criteria", a 140 page book.
It's one where the FAA slipped up and published all of the design (aero/structure) and testing criteria for a sailplane....
Enough data to actually design and certify a glider...
It details how to meet the older CAR Part 5 standards.... Were our Grummans designed to this standard too?
They have a Vd as Design speed, and set Vne as 0.9*Vd.
The flight testing section (yes, they defined that too...) under flutter testing describes how to do the tests, and says testing only needs to be done to the Vd speed.
This is essentially the +10% you are asking for... well actually 11.1%
Perhaps you can use this in your justification..... gil A
At 09:44 PM 1/7/2008, you wrote:
[quote]Remember how when we were in grade school and the teacher whispered something into one person's ear and then that person whispered it into another person's ear and then the last kid was asked to repeat what was said? Â
Where did True Airspeed come from?
Vne has nothing to do with TAS. Â
The FAA wants a dive test to Vne + 20%. Â We've petitioned for Vne + 10%.
--
| | - The Matronics TeamGrumman-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?TeamGrumman-List |
|
|
|
| Back to top |
|
|
flyv35b(at)minetfiber.com
Guest
|
| Posted: Tue Jan 08, 2008 7:05 am Post subject: Dive Tests |
|
|
Take a look at FAR Part 23.335 and 23.1505 (Grummans were certified under Part 23).
Vd (design dive speed) is based on Vc (design cruise speed) and Vne is 0.9Vd (actually a little more complicated than that but essentially that).
Vc min is W/S*1/2 (33) = 2400/140(approx)*1/2(33) = 136.6 kts
Vd min is 1.4Vc for normal category aircraft Vd = 1.4(136.6) = 192.2 kts. (220 mph)
Based on this and Part 23.1505 Vne = 0.9(192.3) = 173 kts (close to the currently established Vne for a Tiger.
I would think the FAA would be very hard pressed to justify or require a Vd any higher than this. If they did and the test is successful could you then you request a higher Vne based base on the higher Vd?
Cliff
[quote] ---
| | - The Matronics TeamGrumman-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?TeamGrumman-List |
|
|
|
| Back to top |
|
|
|
|
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
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
