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1. 01:25 PM - Re: Re: Aerobatics training in the CJ 6 (Walter Lannon)
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| Subject: | Re: Aerobatics training in the CJ 6 |
Hi Marcus;
Have to go with Doug=99s comment on this.
Having restored a few CJ=99s for licensing in Canada over the past 25
years weight and balance was always a concern. I removed all surplus wir
ing, complete radio compass system and a few other surplus items totaling 1
95 lbs. I did not include a battery weight estimate (which I would guess a
t possibly 50 lbs.) since some of that is restored with new batteries. So
I may have removed up to 220 lbs. almost all of which resided well aft of t
he CG.
Part of the ballast was a steel scuba tank (ground reserve air supply) moun
ted on the radio compass receiver rack. 43 lbs. including attach structure
replacing the 50 lb. receiver so no structural change was required.
The primary ballast at the tail compartment (with the access panel and elev
ator trim drum) calculated to bring the forward condition CG within the Chi
nese limit was
45 lbs. In accordance with FAA AC 43.13-2B I installed support structure
to the fwd. and aft bulkheads sufficient to react the required 9g load and
to these a reinforced stainless steel tray to support a stack of 1/8
=9D PB sheets.
The primary danger of an excessively forward CG location is the loss of ele
vator authority in the landing phase so the next step was flight testing wi
th the aircraft loaded in the most forward condition. Fuel was maintained
between 20 to 40 liters total and all landings were at idle power with the
flap in the down position.
Using a grass runway the initial landing showed excellent elevator authorit
y, easily doing a 3 point landing (mains and tail skid). But due to concer
n with that much weight in the tail possibly affecting spin recovery and of
course the expected effect on the fully loaded CG I continued testing with
reducing weight and finished with 28 lbs. of lead (plus 2 lb. of attach s
tructure) and still, in my opinion, adequate elevator authority.
This represented a most forward CG location approx. 20 mm (11/16=9D)
further forward than the actual factory limit and while that was a comforta
ble enough location during testing it could be less so in a worst case scen
ario of forward loading with a very heavy pilot, zero fuel and no power.
Final location of the most aft condition was 1/10=9D less than the fa
ctory limit.
The total balance moment provided by the air tank 43 LB @ 195=9D (838
5 in/lb) plus PB ballast of 30 lb @ 317=9D (9510 in/lb) if reacted by
tail ballast alone would require a weight of 56.5 lbs. which I would consi
der unacceptable. Generally speaking there is usually a Type Certificate Da
ta Sheet specified limit to the amount of ballast weight that can be instal
led in the tail. In the case of the T6 it is 33 lbs. Of course this aircr
aft has no TCDSso it is unknown.
Later flying revealed excellent solo spin recovery and cruise with two
=9Cnormal=9D weight occupants (170 lbs.+/-) with the elevator trim
neutral.
Walt
From: Marcus Bates
Sent: Thursday, February 28, 2019 2:34 PM
Subject: Re: Yak-List: Re: Aerobatics training in the CJ 6
Blitz........remove and pour the tail skid full of molten lead. You will h
ave to repaint it. I removed a measured 500 lbs + of antique radios, exces
sive wiring, instruments, etc. Leaded skid was enough to get CG in limits
=2E
Sent from my iPad
On Feb 28, 2019, at 1:05 PM, Byron Fox <byronmfox@gmail.com> wrote:
To Mark=99s point, I trained briefly with Gennady Elfimov in the UK
15+ years ago in a Yak 52. When I asked him to demonstrate the plane
=99s aerobatic capability, every control movement went from stop to stop an
d my head bounced around the canopy like a pinball. Very, very aggressive i
n true Russian form.
=9CHelps to put arms on canopy rails,=9D he suggested.
It didn=99t.
Blitz Fox
415-307-2405
On Feb 28, 2019, at 8:37 AM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitt
erlich@navy.mil> wrote:
rk.bitterlich@navy.mil>
Absolutely correct that nose heavy aircraft don't spin or snap as well
as those with the CG aft. It was common practice in Russia to add a lead
weight in the tail to bring the CG aft. Pretty far aft actually. This imp
roved how the airplane snapped significantly. Of course they also pulled t
he wings off of early models pulling G's well above maximum. It has been m
y experience that Russian pilots are very serious about winning and persona
lly I admire that about them. Sometimes slightly crazy is a good thing.
Mark
-----Original Message-----
From: owner-yak-list-server@matronics.com <owner-yak-list-server@matron
ics.com> On Behalf Of A. Dennis Savarese
Sent: Thursday, February 28, 2019 7:42 AM
To: yak-list@matronics.com
Subject: [Non-DoD Source] Re: Yak-List: Re: Aerobatics training in the
CJ 6
When the old radio equipment is removed from the rear compartment, most
CJ's I have seen have between 25 and 50 lbs of lead/lead shot installed in
the tail to bring it back into CG.
Dennis
On Wednesday, February 27, 2019, 11:29:08 PM EST, ed.kettler <ed.kettle
r@gmail.com> wrote:
lto:ed.kettler@gmail.com> >
Hi Motoadve,
Welcome to the wonderful world on Changs!
Based on what you are saying about the plane's behavior, you may be nos
e heavy. Taking all of the vacuum tube avionics out from behind the second
seat may have moved the CG well forward. Are you also running out of trim d
uring approach?
I have read where several pilots have installed lead in the tail to rei
nstate the normal CG positions
From one of my RC instructors: "Nose heavy planes fly poorly. Tail he
avy planes fly poorly ... once"
Ed
--------
Ed Kettler
N53HM
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=487844#487844
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