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1. 07:05 AM - Re: Dive Tests (flyv35b)
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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 0.9V
d (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 cur
rently 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 th
en you request a higher Vne based base on the higher Vd=3F
Cliff
----- Original Message -----
From: teamgrumman@aol.com
To: teamgrumman-list@matronics.com
Sent: Monday, January 07, 2008 8:44 PM
Subject: Re: TeamGrumman-List: Dive Tests
Remember how when we were in grade school and the teacher whispered somet
hing into one person's ear and then that person whispered it into another p
erson's ear and then the last kid was asked to repeat what was said=3F
Where did True Airspeed come from=3F
Vne has nothing to do with TAS.
The FAA wants a dive test to Vne + 20%. We've petitioned for Vne + 10%.
-----Original Message-----
From: Gil Alexander <gilalex@earthlink.net>
To: teamgrumman-list@matronics.com
Sent: Fri, 4 Jan 2008 7:35 am
Subject: Re: TeamGrumman-List: Dive Tests
Ned... the FAA might only use IAS for testing, but they can change Vne wi
th 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, Exhibitio
n and Racing is better...
gil A
At 07:50 AM 1/4/2008, you wrote:
Gary,
Will an FAA representative be in teh plane with you when you dive it 24
0 mph
Are you concerned a little about it=3F We don't want to lose you over som
e insidious FAA CYA program.
Here are some comments Fred Kokaska made to me about his dive testing:
=22.....
In CFR Part 23 certification the term TAS is never defined, recognized
or addressed. They have V speed numbers for everything but all testing, st
ructural flight testing, climb/cooling flight testing are all related to IA
S.
They will require a correction chart be developed for installation erro
r of the pitot tube so that test result data is really based on CAS after o
bserved temp and installation errors are accounted for.
A manufacturer of a new design must define and demonstrate (Vd) (Dive s
peed 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 aw
ay 10% as a safety factor) . I went through the Vne part of certification a
t 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 o
verspeed (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 p
itch prop this can be a show stopper and require reducing Vne to prevent th
e overspeed. The other was pitch and roll control and airframe vibration. T
he test pilot started at 10 K feet and pushed over at full power to establi
sh 174 KIAS, did some 30 degree left and right rolling maneuvers. He commen
ted (and I looked out the right side) on the fact the ailerons were both ab
out 2 inches above the normal even with the flap position in level flight f
rom airloads. While this looks spooky, he noticed no binding or control inp
ut problems that he did not like.
So, to answer your question .... I have never seen any reference to the
term =22TAS=22 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=22
Stay safe,
Ned
For-what-it's-worth: B The FAA is making me do carb heat rise tests o
n my new
cowling. B My cowling has in no way affected the source, path, or ope
ration of
the carb heat. B Their argument: B Since I =22MAY=22 have changed the air
pressure
in the lower cowling, I =22MAY=22 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 degr
ees).
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 s
tory. B
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