T-18 Newsletter

Newsletter No. 143
T-18 Newsletter
FebruaIy 2010
~
N18CH - Charles Hoover
In This Issue:
Acrobats and the T-18
Folding Wing Comments
Safety Issues
N711 SH Engine Update
Rudder Stuff
Aileron Trim
The History of Green Apples
Changing Those Ageing Landing Gear Bushings
Notice: (Standard Disclail1zer) As a/ways, ill the past,prescnf, andjuture newsletters, we wouldlike to makeyoll
aware tlral this newsletter is only presented as a clearing house for ideas and opinions, or personal experiences, lind that
anyone lIsing these ideas, opinions, or experiences, do so at their own discretion and risk. There/ore no respol1sibilty or
liability is expressed 01' implied and is without reCOllrse against anyone.
1
Newsletter No. 143
Acrobats and the T-18
Submitted By: B.C. Roemer
Editors Notes
By: Roy FalTis
Here it is, 2010 already and I still don't have a flying T-18. Wow how time flies. (Pun Intended)
Its been awhile since the last issue of the newsletter.
Its not because I didn't have time to write it, its because of the same old problem that plagues all newsletter editors '" lack of material. I will do my best to
get the newsletters out, but I cannot publish one with
blank pages.
On that subject, for those of you that are not aware
of it, there is now a new T-18 Forum available on the
Web. This new forum is being built and maintained by
Lee Walton. It will eventually replace the old Yahoo
Groups ThorpList. In fact the old ThorpList is mostly
silent with nearly all of the activity being carried out
on the newer forum. If you haven't seen it yet, you can
get to it from the home page of the T-18 web site. In
the upper p011ion of the page click on "Thorp Forum".
Here is the link .. just click here to see the new F mum:
http://tI8.net/forum/
We have covered this subject many times but I need
to revisit it again. With the new forum, it is highly
possible that it could obsolete this newsletter. I have
received many comments from members that want
to keep this written newsletter, so that being said,
how are we going to accomplish this? I simply do not
receive enough material to fill these pages. The new
forum has reduced my input even more. I don't have
an answer, but its something everyone needs to think
about and respond accordingly. The T-18 Newsletter is
in Your Hands.
I will attempt to publish the newsletter with old material that J have saved over the years. We will evaluate the possibilities this year and make some decision
by the end of2010 as to the fate of the written newsletter.
Oh No, Not another know it all who isn't even in
the amateur class. I have done hundreds of aerobatic
maneuvers and need to pass on to all T-18 pilots, some
very impm1ant information.
Background info: "G's" - Ask yom flight instructor. When we visited John Thorp he said the T-18 was
rated 6 neg and 9 pos, which means fi'om 0 to 6 G's
positive things would distort but return to n0l111al. 6 to
9 G's things stay bent up but may be flyable, 9 G's and
above you loose parts. On the negative it is proportionally less. I personally don't like negative anything
and really don't want to test out anything above 4
positive. These ratings are for a well built, according
to plans I-18 flying under the weight restriction (1250
gross). I can hear some of you already, "I built according to plans" - Yeah Right. What type of wing tips do
you have? Fiberglass? (We do too) Well, when John
submitted the plans to the FAA, the tips were aluminum. So what? Well you had better double the screws
that hold them to the wing tip as the hole tear out
strength of fiberglass is about 112 the strength of aluminum. And you sure don't want to loose a wing tip.
Almost for sure, here is what would happen .. The aileron balance weight goes into a hole cut into the bottom
of the tip. If the tip tears off, the weight will almost
assuredly snag in the depar1ing tip and will rip off the
outer aileron hinge, and then the aileron will depart,
and in doing so will bend up the control rods so you
won't have any control of the remaining aileron.
1 suspect this is exactly what happened to a friend
of mine right at Oshkosh. Al Ninetaufer was always
improving his T-18 so as to beat me at the annual
Oshkosh race ofT-18 's. Of course he never did, and
the last year we raced he wanted to take me on "one to
one". We went up again, just the two of us, and he lost
again. After we got down, I happened to look at his
left wing tip. It was clobbered up at the trailing edge,
going towards the front. I asked about it and he said
it was splitting and he used some resin to cement the
cracks together, and it left a messy area.
It being the last day of the convention, he gassed up.
His neighbors daughter wanted a ride so he offered to
take her around the pattem.
cont. pg 3
2
Acrobats and the T-18, cont.
On the first south end turn, he crashed, and of course
both were killed, and the airplane with full fuel burnt
up completely, He was at about maximum weight.
Some time after the accident, another airplane following him was reported to see something come off the
airplane, Lots of airplanes were taking off to go home,
and this repOli being old, was never follow up. I personally believe it's possible the tip failed and jammed
everything, It is true he was flying a flawed airplane.
He had used 1/8" rivets in the wing junction instead of
3/16" steel bolts. A failure here would surely separate
the outer wing panel and it would fall separate from
the aircraft and would not have burned up.
Now as to acrobatics -- I feel that the T-18 is a poor
platform, If your into heavy acrobatics - get a Pitts.
The T-18 is just not strong enough. Sure, simple maneuvers such as rolls are easy and great fun, but we do
not do any tumbling, tail slides, spins, snap rolls, high
G pull up's, etc. Bob Dial, who flew just about the inventory of the air force said "A T-18 can do everything
a P-5l ean do". But should you? Definitely NOT!
A while back, a few T-18' ers songht to draw up
some guidelines for new owners and newly flying
T-18's, as well as the complete fleet. They eoncludcd
that it would be safe to do anything that is 3 G's or
less. This is good advice and they should be commended for their effOli. But -- generally is isn't the
maneuver that will give you the G's, its when you fall
out of the maneuver that produces the high G loads
and its usually to late to do anything about it. I once
rode with Bob in an unnamed airplane. He did a loop
with a roll on top and the G meter registered 2 G's or
less! He took instructions, even though he flew fighters.
And now I will tell you about a maneuver that will
register zero G's or close to it, and is very dangerous. Step or Point Rolls, You see P-5l 's do them all
the time, you Imow, 4,8, or 16 points, proving that the
pilot can count. Now to make them look good from
the ground, the points need to be crisp. That means
full stick thrown over then back quickly, Don't Do
Them! I was doing the condition inspection on our
T-18, laying on cardboard looking up at the aileron
and guess what I found? A nice 6" to 8" crack in the
rear spar running right through the hinge, Rolling to
the right means the right aileron goes up about twice
as much as the left one goes down as thus has a higher
Newsletter No. 143
air loading and every "point" loads up the hinge Big
Time. Now if you enjoy drilling out the top wing skin
and repairing the rear spar, re-riviteing, re-painting,
and possibly loosing your life before you get to do all
of this -- go ahead and do point rolls, We were lucky,
and this is a lesson all T-18' ers should know about.
Panel Upgrade
Submitted By: Tom WOlih
I installed the Garmin 430 WASS unit right after the
Arlington PNW EAA show in 2007. I had been flying considerable IMC weather between Tacoma, WA
and McMinnville, OR, I felt it was a good decision
even though both airpOlis have an ILS approach. In
VFR conditions I had flown the TIR R 17 GPS approach on the Garmin 250XL by sequentially setting
the GPS fix points (not legal for IMC). I've flown the
TIR R35 GPS WASS approach with vertical guidance a few times. The minimum is only about 50'
higher than the RI7 ILS, The CDT serves the VOR
en route or approaches (if desired), the LOC/ILS, or
the GPS-WASS. One really should use the simulator
program on a computer and in the airplane to become
proficient. Anyone wanting more information should
contact a Ganllin dealer, or you can contact me if you
have questions,
cont. pg 4
3
Panel Upg:rade. cont.
Newsletter No. 143
this metal. The least strokes you make the better. Now
the windscreen will tuck under the skin and make a
nice smooth fit. As for the trim pieces over the roll
bar. Use about a 18" wide piece of poster paper and
make a template about 1.25" wide. Transfer this to
your metal. As for the final fitting to the canopy,
abtain several thickness of rubber strip
.040,.090,.125 use this to shim the windsield and
canopy to mate at the opening. It's been 10 years
since I did mine. I'm trying to remember all the
details.
Bill Williams
N295RS Panel with Old Gm'min
Folding Wing Comments
I have heard that some S-18 owners have elected to
not use the folding wing feature and substituted bolts
in place of the wing attachment pins. Plans call for pin
diameter as .5615 to .5610 which is. of course. not a
standard AN size. Has anyone heard of a bolt'
that would fit?
Hal Underwood
Panel with new Garmin 430 WASS
l.
-:,,:Builder Question: We are thinkinah of makin"h 3
pieces for the aluminum stl"ip ovel' the windshield/
rollbar to minimize the complex curve required.
Any how-to thoughts on how ,vou made .vour rollbar/windshield cover?
Cut top skin ,where the lower part of the windshield
meets the skin over the fuel tank to conform to the
shape of the windscreen. Now tim this skin 3/4" to 1"
larger the the wind screen line. Sand and polish this
edge. Now take a 2X2 about two foot long and put an
end in it that looks like an old fashion c10thspin the
throat about 3/4 to 1". Grease the trimmed skin , now
taking the clothspin and make several pulls around
this skin putting upward pressure as you pull around
I believe that you can get a little tighter, closer
tolerance fit with a 9/16" high-strength bolt. ifit isn't
going to be removed frequently. Also, if you are folding the wing regularly, the fit is going to degrade over
time. The soft cadmium plating is going to wear off
of both male & female parts first. I started building: a
folding wing originally, and made a set of pins ou; of
431 stainless. heat treated to 195,000 psi. A very light
lubric.ant was contemplated (Lu Sunderland suggested
Vaselme). We've had a similar discussion on this forum before, but I'll say it again ... I'll take a joint with
some clamping action over a simple shear pin if given
the choice. Why not? There is little to no
chance of movement of the fastener in the hole.
Also, I believe that there is some additional "hidden"
strength to be had by friction between mating surfaces.
Don't need any additional strength? I agree, but it's
free. I believe that a classic example of this was the
T-18 that was built with it's main spar joint fittings
attached with 1/8" aluminum rivets instead of 3/16"
steel fasteners. T don'l believe that engineers like to
cont. pg
5
4
Folding Wing Comments. cont.
consider this becanse it is something that is not easily /accurately calculated, given the variables (I'm an
engineer by education mysclt). Am I way wrong
here? Any comments are appreciated.
John Evens N7lJE
AMEN John, you put some common sence to the
matter. I folded my wings I 1/2 times just to see if it
workcd. Then installed bolts for the last 650 hrs. of
flight with no problems. It takcs about the samc
amount of time to remove the bolts as the pins. 10
minutes to remove the bolts and 30 minutes to answer
questions. The only time I've removed (or folded) the
wings is when I take it home for major work, which is
seldom. The sister ship to my plane has pins in the
wings, with about 1/8" play at the wing tip. It has
been Iikc that for the past 1200 hrs. of flight.
Bill Williams
Guys ...
Designers NEVER presume any friction (or sealantadllcsive) load-carrying capability in a convcntional
laminated stack-up: ALL load transfer goes thru the
Bolts [rivets, etc]. Torquing nuts (with washers) to a
"standard value" is used to uniformly "pull together
and preload" parts, minimize gapping, and insuring
uniform/consistent bolt-to-bolt-to-bolt installation and
load-sharing.
NOTE: nuts should always be torqued using a crosspattern ("criss-cross pattern") strategy... in stages,
up-to final torque values. I recommend starting fingertight, then going to 33% torque, then going to 66%
torquc and then going to 100% (required) torque. After
the second stage any free-play and joint relaxation
will have occurred... and the final torque will achieve
maximum mechanical tightness and strength [to resist
fatigue cracking and loosening]. If You "step-up to the
final torque value directly [no intermediate torquing],
then the joint WILL loosen slightly (relax), result in a
lower residual torque value ... and increasing potential
Newsletter No. 143
for long-term problems. I have actually seen cases
where poorly installed nuts have loosened in-service
as bolts cycled back/forth in slightly loose holes.
NOTE: For similar reasons, rivets should be installed
between clecoed holes ... insuring a tight joint. This
will minimize possibility for rivet "shanking" (rivetshank bulging) between metal layers ... which degrades
riveted-joint strength.
NOTE: When sealant is introduced between pmis, this
process becomes even more critical, IE: sealant must
be "squeezed-out" for "best" mechanical strength ...
leaving only a fine film in-between parts and in holes.
A good plan is to use the sealant squeeze-out to fillet
along part edges for added fluid-tightness. This is especially critical for riveted joints, to prevent shanking.
CAUTION: NEVER significantly over-torque bolts/
nuts intended for shear only... bolt-head or nut-thread
failure could occur.
ALSO: be careful when installing AN3-AN* bolts ...
the AN spec does NOT require the threads to be
made smaller-in-diameter that the bolt shank. Tighttolerance holes can be scored on installation by the
threads ... then appear loose. Note: Equivalent NAS
bolt specs require threads to be at-least O.OOI-in
LOWER in diameter than the minimum bolt shank
tolerance.
AC43.13-IB and AC43.13-2A are excellent general
references for mechanics on various "aircraft quality"
working practices and processes. I STRONGLY recommend evelyone get a copy of these documents ... at
least sections applicable to metal aircraft [and composites for those with fiberglass parts]. These are available
for free download from the FAA website. You can go
directly to the down-load site from the following link.
http://www.airweb.faa.l!ov/Regulatorvand.Guidance Librarv/rgAdvisorvCirculaLnsfiMainFrame
Regards
Wil Taylor
5
Saftev Issue - Failed landing Gear
Concerning the operation of a Thorp T-18 aircraft,
N49RT, at Olive Branch, Mississippi, at 1025 Local
time on 9-11-04,
I was the PIC of the accident aircraft. I met the owner/
seller at Olive Branch to facilitate my purchase of the
aircraft. He had flown it in fi'om Virginia the previous
evening and we met on the ramp of the Olive Branch
Airport earlier that day. I flew the airplane from the
right seat several circuits of the pattern. I bought the
aircraft, paid him and received a signed Bill of Sale. I
then flew the aircraft again from the left seat with Mr.
Franklin as a passenger for my fUlther familiarization.
Several landings were completed satisfactorily.
On the last landing circuit I landed the aircraft on the
center line when the aircraft suddenly veered left of
the center line. Violent shaking occurred and the aircraft then veered right uncontrollably, approximately
50 degrees to the center line and departed the runway,
traveled downslope to a deep drainage ditch, struck a
small tree and came to rest in the ditch. It was later
determined that the left main gear had collapsed at its
fastening to the body of the aircraft due to the failure
of the single retaining bolt which held the main gear
leg in its housing.
An exploded sketch of the aircraft illustrates the failed
bolt which secured the gear leg. The FAA Inspector
who investigated the accident found the nut end of the
bolt on the runway. The grip length of the bolt was located in the head of the gear leg when it was removed
by an A&P-IA after I recovered the aircraft. Both bolt
fragments have been submitted to the NTSB for laboratory examination.
The FAA Inspector photographed the wavy lines on
the runway apparently left by the left main tire, and
the tread marks of the hard right turn across the runwayan departure. [ have those, and several other
photo'S I took after the accident to illustrate what
happened. A photograph I took of the left main gear
which was rotated in its fastening apparently illustrates the position of that gear which threw the aircraft
into the hard right turn off the runway.
When the aircraft suddenly veered left and started
Newsletter No. 143
shaking, not knowing what had occurred, I added
power to straighten it up. My first thought was to fly it
out of there. However, when it then suddenly veered
right with the left wing very low J anticipated a ground
loop, there was a prop strike as it tnrned and J pulled
power off. I must say that J did not allow the aircraft
to ground loop; it did not dig in a wingtip and go
invelted and I did not drop the nose or it wonld have
gone inverted. I flew the aircraft all through the accident scenario. The airplane had depmted the runway
to the right and went downslope away from the runway, power off, about fifty to seventy five yards. The
slope was covered with wet grass and braking was
ineffective. As the airplane entered the deep ravine
it struck a small tree with the right wing turning it
around, engaging the left wing in foliage; then it came
to rest with the tail in ben)' vines, bushes and brush.
My passenger and I were not injured.
Mr. Franklin, passenger and seller of the airplane, had
represented to me that the aircraft had been well maintained. The aircraft log reflected an annual inspection
on August 1,2004. Upon my inspection, I thought the
aircraft evidenced a need for TLC. My safety recommendation on my NTSB report related, "more critical
inspection of bolt holding landing gear leg to body of
aircraft, by inspector at annual inspection". It is obvious from the sketch that the bolt which secures the
gear leg cannot be readily observed on a routine preflight inspection; the cowling must be removed and the
engine lifted to examine the single bolt on each side.
When the FAA Inspector initially investigated this
accident the next day, I was at loss to tell him what
caused this accident, but I did tell him essentially what
transpired as above. The failed bolt was discovered
later when the airplane was recovered from the ravine.
The Inspector thereafter retumed to the scene and
found the nut end of the bolt on the runway. I have
fully and candidly cooperated with The FAA Inspector
and evel),one else of interest. So, that's my stm),.
George H. Savord
6
Newsletter No. 143
Updating N711SH Engine
By: Bob Highley
As my original engine reaches TBO, I decided to build up a new one and reap the benefits of the newer technology. Here are some pix ofthe effort:
Who took this crooked picture?
The bare bones
You need to use an extension block on the back
of the intake manifold to get the fuel pump to clear
the injection unit. http://www.airfiowperformunce.
com/ here in the USA has many different ones of
these if you run out oflocal SA options
After a few beers .. a completed engine
Here are a couple of shots of the motor mount I have used for a rear mounted induction system
7
Newsletter No. 143
Rudder Stuff
By: Bob Highley
1 recall a recent post that indicated the rudder limits were not called out and more is better. The limits are
found in drawings -561 and -567 and are 30 degrees either side of center. More than that and you certainly can
have brake pedal/tank support interference. For those of you that think you can never have too much rudder,
there is such a phenomenon as vertical stabilizer stall.
Not something you really want to mess with.
Now that 1 have your attention by way of the subject, here are a few shots of an addition 1 have made to
N711 SH while she is down for an engine change. lmust
thank Hurant Karibian for the idea which I have shamelessly stolen. As some of you know all too well, if you
break a rudder cable. you will have no brakes! I almost
had this happen to me when a wire shorted to the rudder cable and bmned it two thirds ofthe way tlu·ough.
Hurant's idea is another cable that connects the two sides
through an additional pulley and will give you something
to push against if a cable fails. My addition to this modification is to put a friction devise on the return pulley so
you can "lock" the rudder in flight. This is at the suggestion of Jim Younkin, designer of the TruTrak series of
autopilots. With my feet flat on the floor in the tracking
mode, my plane would hunt as the rudder was free to
move side to side. The "lock" really just puts some drag
in the system and easily ovelTidden even if the pulley is
locked tight. The shaft shown in the top picture, will get
a knob to adjust the tension on the pulley.
The center pictme shows the return pulley and friction lock apart. The two phenolic washers are held from
rotating by the rivets. The shaft screws into a nutplate
under the 601 bnlkhead and applies the squeeze for the
friction lock. The 601 is beefed up to take the strain
should one stomp down on the binders.
The bottom cable is the one that goes to the rudder
lock/safety loop.
Hopefully this will be a valuable safley feature ifI ever
have a rudder cable failme. 1 sure hope I never need to
test it.
8
Newsletter No. 143
Charles Hoover's awesomelv polished T-18
(Cover Airplane)
Isn't this the most beautiful polish job you have
ever seen on a T-18. The finish appears absolutely
flawless and polished like a mirror.
How in the heck is that possible? Hats of to Mr.
Charles Hoover - N 18CH - Oakdale, MN.
9
Newsletter No. 143
Rudder Trim - A different Approach
Submitted by: Gmy Green
I just went out and took some photos of the rudder trim mechanism. Don't get wrapped around the axle thinking it is complicated. It is not. I think you could make them with a drill press and band saw. If you have access
to a mill, it'd make it easier to make the tunnel for the cable to run thru, but I think it could be done with a drill
press. The roll pins fit tight in the lower block and the upper block roll pin holes are drilled large enongh for the
block to slide easily up and down on the pins. I think the white plastic material is lI2" nylon, Teflon, or some
kind of material like that. Phenolic block would be excellent also. This mechanism was developed by Charlie
Hooper. He is president of our EAA Ch 775 mld has built several experimental airplanes. I certainly can't take
credit for the invention. I explained that to the Oshkosh judges, but they gave me the Stan Dzik Award anyway.
I thinl, they considered the bonded windshield & canopy, removable floorboard, folding seat backs, and no forward tunnel as design innovations also. Anyway, I ain't sending it back even if I didn't use annealed rivets.
By the way, you can land with the rudder cable trim brake fully applied. I have done it two or three times
(some use a checklist to avoid things like that). It is no problem. You just notice a little stiffiless in the rudder.
The cable only has enough drag on it to keep it from moving on its own and it doesn't have a self centering actioll. You can oven-ide the braking action easily by using the rudder pedals.
Friction Set
Friction Lock in "Free" position
Engine Alignment Ouestion
In preparing for first flight, I have had a few comments here about the engine position to the center line. Being
an engineering "Dummy", I haven't really thought that much about it. So a good "engineering" explanation of
John's ideas would be appreciated. What would happen if the engine were aligned on center line? I have a
mouse 111otor so there isn't a lot of zoom up front. Is the TI8 engine alignment unusual or are there other similar designs? I ask this because I really believe there are no dumb questions (because I have so many). Anyway,
this came up for discussion the other day.
Bob Clayton
cont. pg 13
10
Newsletter No. 143
Hurant Karibian's rotary engine installation. I wonder if he ever got this thing flying? Hurant, could you
give us an update?
I had one photo of my canopy cover in the computer. I have posted it in the pictures section of the web site.
It covers the fuel door and the static ports on the side of the fuselage and comes with a handy bag to keep the
cover in when flying. It's nice and tight and does not flap in the wind. The web site for the manufacturer is
www.aerocovers.com They used 111y plane as a pattern so they should be able to turn one out in a couple of
days.
Jim Mantyla
Ed Ludtke still makes the best fitting canopy covers. He and Nettie live here at "the Valley" now. Ed's cell
phone is 605-940-9420.
Gary Green
Bmce's Custom Covers (www.aircraftcovers.com)inSunnyvale.CA. They will even customize it with the
colors of your paint sceme and/or include your N number. The fit is excellent and it has a shock cord around the
perimeter to keep everything tight and not flap in the wind.
Bmce Finney - N18JF T-18C #262
II
Newsletter No. 143
Aileron Trim As installed on T-18CW, N711SH
Submitted By: Bob Hie-hley
Trim tab is about the size of a dollar bill. The general layout is the same as the antisel\10 tab on the stab. As
you can see, my aileron has folded trailing edges that keep the high speed forces light. The tab is folded out of
one piece of .0202024 T-3. There is a small sub-spar that the hinge is riveted to and the pin can be pulled from
the end.
The lower shot
shows the underside.
The clevis is from
a model airplane.
The stock one from
Richard Allen is a bit
fat for my taste. The
panel gives access
to the servo, which
is mounted on the
panel. The wires lead
out of the aileron spar
to a plug on the rear
of the wing. That's
about it. Put the trim
on the left side so you
don't have to look
around your passenger to see it.
I have had over 1700 trouble free hours with this setup.
12
Newsletter No. 143
Engine Alignment Onestion. cant.
If the engine is aligned directly on the centerline,
the plane wiII jnst fly in left-tnrning circles. Prepare
for flight accordingly... ;-)
Saftev Issue - Canopv Rollers
How serendipitous the Bob Highley writes about
canopy separation in the most recent NL as I sat down
to compose my thoughts about what transpired a few
OK, the full answer is that the RH (dcscending) prop
days
ago.
blade makes more "thrust" and tends to yaw the airI was flying back from Bar Harbor Maine at about
craft to the left. (Garrison did a whole column about
2500'
and 150mph when suddenly 1 hear a pop and
this last month in Flying magazine) So offsetting the
the left front side of the canopy is out in the airstream
engine slightly to the right helps to offset this tendency. I'm guessing that if the engine is bolted on straiaht about 3". Needless to say that'll get your attention
~
'"
quick, I thought the canopy was coming off in flight
then you might need a bit of rudder trim for straight
and level flight. Some of our more seasoned mCI~1bcrs, and taking my vert. stab. with it. Fortunately, the over
head locking device held until landing.
particularly the ones that are flying, might bc able to
I write this not so much to share the experience, as
tell whether or not they have noticed any difference
with or without offset. My guess is that if you bolt the to warn ilie Thorp fleet (if it's not already being done)
about what I've concluded the cause to be.
engine on straight, you bend the rudder tab just a bit
The top and bottom rollers on the forward pilots
morc, forget about it and go flying.
side after being opened and closed for the last 35 years
where
fine, turns out the outboard section of aluminum
As usual, all technical advice here is subject to adbetween the top and bottom roller had been slowly
mendment and worth just what you paid for it. ;-)
"sawed" by the aluminum angle behind it, until there
was only a 1/32 of an inch left and when that pressure
Andrew
built it let go (See pics). So, if it's not alreadv being
done check the outboard section of the cano;y that nms along the aluminum angle beside it for ware.
The Ercoupe is rigged the same way. Fred Weik
(Spn Ercoupe designer, collaborated on the Cherokee
Chuck Kincer
with J. T. Van's CUlTent batch of airplanes also has an
N575CK
offset engine. One member (Carlyle Dean) built his
with no offsets. I don't recall it being improved over
the stock design. My T-18 climbs, cruises, and descends almost feet fi·ee. I wouldn't change the design,
it works.
Bob Highley
N711SH
SN 835
Any Engineer types out there wish to comment on
the above discussion?
j
-$.Looks like a definete item to add to that condition
inspection.
13
Newsletter No. 143
T-JS's Need Love Too !!
Is this a sad site or what? It has an N number visable on the vertical fin .. I wonder is she ever flew.
cont. pg 15
14
Newsletter No. 143
T-18's Need Love Too 11, cont.
My understanding is that this gal lived to fly again.
Cool Tool
r III like Bill Gates. I find some ones great idea and I pass it on as my
haven't. I just got home from an EAA project showing. The gentleman (Ron Jennings) built a beautiful
Zenith 70 L but like a TI8 he did it all from plans.
His ribs were beautiful including the lightning holes.
I asked what kind of tool he used to chamfer the
holes. I pictured a couple male female wood blocks.
He pulls out the little dogleged bolt and proceeds to
attach it to the fly cutter in his drill press. After you
cut the holes you replace the blade with this tool.
You put a little grease around the lightning hole and
use this tool to flare the hole. The finished product
looked perfect.
OW11.
Have you seen a tool like this. I
BobMO
15
Newsletter No. 143
An Interesting Note On Electronic Ignitions
The reports and tumors about electronic ignition
systems affecting propeller stresses have merit. Some
systems we've tested increase stresses more than
others. We've tested one propeller with three different systems on the Lycoming (1)0-360 180 Hp series
engine. This engine is probably the worst case, small
crank-pin journals, no countelweight dampers. We are
working here at Hartzell to better understand this issue. We are talking to manufacturers of these systems
to understand how they operate and affect the prop. It
appears advanced ignition timing is the biggest contribntor. I've also talked to Lycoming and they are
planning to look at crankshaft stresses (remember, Lycoming didn't develop most of the systems available
to us and they don't have all the answers either).
This situation is similar to any other mods people
make to the Lycoming (1)0-360 to enhance performance. Higher compression ratio pistons, different
cams, trick exhaust systems, etc., if they increase
horsepower, they increase crankshaft and propeller
blade stresses, possibly above fatigue allowable levels.
We cannot endorse the use of all electronic ignition
systems until we test and determine if the application
is safe. Unfortunately, the (1)0-360 is the worst case
even though its the most popular among our community.
A wood fixed-pitch should be safe with these systems. However, I caunot vouch for the crankshaft
with a wood propeller. If you are flying a metal
prop and have specific questions, please contact your
propeller manufacturer. It's better to be safe and have
peace of mind in my opinion.
Les Doud
Propeller Integration Engineer
Hm1zell Propeller Inc.
CHANGING THE LANDING GEAR BUSHINGS
ON YOUR VINTAGE THORP
There comes a time in your T-18's life when things
that you or the builder lovingly put in service when the
plane was originally assembled need to be replaced.
The rubber isolator bushings in the main gear fit this
category. These are the v." neoprene washers and tube
that serve to provide some shock mount to our rather
stiff gear.
When the plane was assembled, the gear was most
likely put on the fuselage before the engine was
installed. We all look forward to the time when the
plane is "up on the gear." It is a real pain to remove
the engine for such a small thing as replacing these
bushings. I looked at the job for a long time before
I could not put it off any longer. The bushings had
mushed out from between the gear and the firewall
washer. The gear was hanging loose in flight and
tracked poorly. Look at yours next time the cowl is
off.
My solution to the replacement goes like this: Obtain the use of an engine hoist and a hydraulic jack.
Lift one wing with the hydraulic jack until the wheel
is off the ground. Now put tension on the engine with
the hoist. This is a jack one/lift the other operation.
The idea is to take the compression off of the gear
mount. I built a removable floor in my Thorp, so the
next pm1 was relatively easy. With the floor removed,
I was able to take the main gear mounting bolt loose
and slip the rubbers out and put the new ones in. You
will need the help of a small friend to get the bolts out
if your floor is per the plans. Then you repeat with the
other side. Doing it one side at a time keeps the gear
aligned and things don't get too far out of hand.
Of course, you need to chock the non-raised main
wheel and the tail wheel while all of this is going on.
I also had chocks to control the movement of the frce
wheel.
I found the rubber at a local sheet rubber supply
house. 11 is called gasket material in the trade and
shore ratings and durometer numbers don't mean
much to these guys. The kind I used has two layers of fabric fused into it. The original material that
met Thorp's specs didn't hold up in compression and
squeezed out.
You will be surprised at how the replacement of
those bushings helps the handling.
Bob Highley
N711SH
16
Newsletter No. 143
A BRIEF HISTORY OF THE AIRCRAFT KNOWN AS GREENAPPLES (N23GA)
First, to avoid confusion, this aircraft has no relationship to another Green Apples, a Mustang Two, which
some may have seen at Oshkosh. The christening of Greenapples N23GA predates the Mustang II, and has to
do with the initials of its designer and builder, Gale Abels. In 1974 Richard gave Gale his first Thorp Tl8 flight
in om 125HP standard model sin 176. Gale had already begun construction on his project, which evolved into
Greenapples.
As a competition sailplane pilot, Gale was keen on reducing drag in every aspect of any aircraft he ever flew.
He also was a talented architect, and a perfectionist. He decided to apply his knowledge of aerodynamics, and
his design and drafting skills to the modification of his Thorp project. As each modification ripened in his mind,
he created formal drawings which enabled him to consult with John Thorp. These plans, along with correspondence between Gale and John, provide us with an interesting and valuable record of their insights on this
aircraft, which came to be known as an AT-19. In 1979 he was awarded the EAA Custom Aircraft Outstanding
Workmanship Award in addition to the below mentioned Stan Dzik Award.
The following is quoted from Jane's All the World Aircraft 1980:
Mr. L. Gale Abels, an architect of Boulder, Colorado, has designed and built a two-seat light monoplane
known as the Greenapples AT-I 9. Construction took seven years, the aircraft beginning as a modified Thorp
T-18. Constant redesign during construction led to only the landing gear and cockpit canopy of the finished aircraft being of Thorp type. First flight was made on 23 May 1979. It has been reported that the modified wing,
of increased span and higher aspect ratio, using thicker skins and fitted with plain flaps, provides a slower landing speed and increased rate of climb compared with the Thorp T-18. The AT-19 received the Stan Dzik Memorial Award for 'Outstanding Design Contribution' at the 1979 EAA Fly-in.
cont. pg 18
17
Newsletter No. 143
A BRIEF HISTORY OF THE AIRCRAFT KNOWN AS GREENAPPLES (N23GA). cont.
TYPE: Side-by-side two-seat light aircraft.
POWERPLANT: (l80hp Avco Lycoming 0-360-AIA flat-four engine. Fuel capacity 33 US gallons.
DIMENSIONS, EXTERNAL
Wing span: 24 ft 4 in
Wing chord (at root): 4 ft. 2 in. (at tip): 2 ft 6 in
Length overall: 21 ft 0 in
WEIGHTS
Empty: 1,040 lb.
Max T-O weight: 1700 lb.
PERFORMANCE
Cruising speed: 186 knots (214 mph)
Landing speed: 61 knots (70 mph)
Max rate of climb at S/L: 2,500 ft/min
Range with max fuel, 30 min reserves: 600 miles
In 1995, Gale lost his battle with cancer. Before his illness he had proved the viability of his design by flying
Greenapples over 900 hours. In early 1996, we had the opportunity to acquire this beautiful aircraft from his
daughters, and enjoyed it for many hours as we flew around the country. Its speed and feather light controls
make it fun to fly, and its one-of-a-kind aspect drew interest wherever we went. The V tail readily identifies
Greenapples as something unusual to even the most casual observer, and the long tapered wings are a graceful compliment to the extended Thorp-like fuselage. Gale's craftsmanship was impeccable; he countersunk and
filled each rivet to create a glass-smooth surface.
It became apparent tllat Greenapples required some repairs and retrofit, which we began that summer. The fuse-
lage is currently in our home shop, the wing at our hangar at Rapid City Regional Airport. We have reinforced
the instrument panel bulkhead, and rewelded the fuel tank, these two essential repairs having led us into this
project. Our plans also include a new tail wheel, refurbished interior, and new radio, as well as adjustments to
the main gear. Eventually, we would like to update the panel as well, but our intentions are to get Greenapples
back into the air, for she is a true joy to fly'
RICHARD AND KATHY BRANDIGER
Aiation Truisms
Basic Flving Rules:
1. Try to stay in the middle of the air.
2. Do not go near the edges of it.
3. The edges of the air can be recognized by the appearance of ground, buildings, sea, trees and interstellar
space. It is much more difficult to fly in the edges.
It's better to break ground and head into the wind than to break wind and head into the ground.
It only takes two things to fly: airspeed, and money.
18
Newsletter No. 143
Our Members Thorps
John Groth - VH-IXI - Tannum Sands, Australia
Chris & Brent Schultz - N6CM - Corona, CA
19
T-18/S-18 Thorp Newsletter
Roy Farris
1220 Stellar Drive
Franklin, IN. 46131
Phone: (317)736-8903
email: [email protected]
Newsletter No. 143
February 2010
20