What's the takeoff trim setting?
Raven
trim setting in a C172 be? I ask this because I've rented two different
172s, and each has a much different reaction to the takeoff trim setting.
The older (1968) aircraft, which is used primarily for low time students
seems to have a rather neutral feel to the elevator at the takeoff
setting. The plane stays on the ground until you apply very gentle
backpressure to lift the nose off.
The other aircraft is a year younger, and it wants to jump off the
runway as soon as you have any speed. It tends to lift off on its own
between 50 and 55 knots without any elevator input. I find I have to
push the nose down to accelerate after liftoff before I can climb out.
With a sample size of 2, I don't know which, if either, are behaving the
way Cessna intended.
Any other experience out there?
-- Raven
Elinsky
>trim setting in a C172 be? I ask this because I've rented two different
>172s, and each has a much different reaction to the takeoff trim setting
Are you setting takeoff trim by the marker next to the trim wheel, or by
looking at the trim tab on the elevator? I set takeoff trim by pulling back on
the yoke so I can see the elevator, and adjusting the trim wheel so the trim
tab is level with the elevator. This aligns the trim wheel marker with the
"takeoff" position on some 172P's, but not on others.
Jay
Paul Laich
A/C is loaded, however. Takeoff trim is not an exact science but rather
there to provide assistance in the backpressure on the yoke during your
takeoff roll and at the point of rotation. I've made my own mark on the
trim wheel setting that is slightly more 'nose down' than the
manufacturer's mark. Maybe that's because of added equipment affecting the
CG. Experiment with different settings, but alway remember to 'fly the
plane, first'.
Elinsky <eli...@aol.com> wrote in article
<19990112134953...@ng-ch1.aol.com>...
less...@aol.com
nospam wrote:
> I hope this is a simple question: What should the effect of the takeoff
> trim setting in a C172 be? I ask this because I've rented two different
>
> The older (1968) aircraft, which is used primarily for low time students
> seems to have a rather neutral feel to the elevator at the takeoff
> setting. The plane stays on the ground until you apply very gentle
> backpressure to lift the nose off.
>
> The other aircraft is a year younger, and it wants to jump off the
> runway as soon as you have any speed. It tends to lift off on its own
> between 50 and 55 knots without any elevator input. I find I have to
> push the nose down to accelerate after liftoff before I can climb out.
>
> With a sample size of 2, I don't know which, if either, are behaving the
> way Cessna intended.
>
> Any other experience out there?
>
> -- Raven
>
I can't authoritatively say what behavior Cessna intended while at takeoff
trim. I try to set the trim so as to produce a climb at Vy. I am not
especially concerned with whether the airplane must be pushed into the air or
whether it jumps into the air. Once it is in the air, it should climb at my
proposed airspeed with only minor adjustments. Of course, the airplane will
need to be fine tuned according to where in the CG envelope the CG is. I
suspect the takeoff trim setting is a stab at the appropriate trim when the CG
is in the middle of the CG envelope. There intentions might have simply been
to keep the pilot from having to arm wrestle the control yoke to keep the
airplane in the air just after takeoff.
Les Sparks
less...@aol.com
http://members.aol.com/woodglider/
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William Watson
>
> I hope this is a simple question: What should the effect of the takeoff
> trim setting in a C172 be? I ask this because I've rented two different
> 172s, and each has a much different reaction to the takeoff trim setting.
I don't know that I can increase your sample size to a statistically
significant level, but the three 172s I've flown (all circa ~1980), the
takeoff trim setting is relatively nose-up. I usually have to hold
foward yoke pressure to keep the plane on the ground towards the end of
the takeoff roll, and ALWAYS have to trim nose-down to maintain Vy after
takeoff.
- bill
bi...@thekid.com
El Yayo.
>
>With a sample size of 2, I don't know which, if either, are behaving the
>way Cessna intended.
>
>Any other experience out there?
>
Mine has a repainted takeoff trimm setting marked in the dial.. when
set that way, it needs a firm pull for takeoff but won't need much trim
during climb...
172B...
--
Eduardo Kaftanski | To put a pipe in byte mode,
eka...@webhost.cl | type PIPE_TYPE_BYTE.
ICQ: 9396717 | (from the Visual C++ help file.)
http://www.webhost.cl |
John Price
I'm not sure what Cessna intended, but a couple of thoughts... You
probably
don't want to set it such that you have to push very hard on the yoke to
climb at VX or VY... You're setting yourself up for a potential stall if
something goes wrong... like maybe the seat pins give way (Na, that
would
never happen on a 172)... Somewhere along the line, I've learned to play
with the trim as I'm starting my takeoff roll... If it feels like the
nose
is trying to come too high too early, then add a little nose down... If
I'm
working too hard to hold weight off the nose wheel add a little nose
up...
I've probably flown 5 or 6 172s now, and the're all different... The
"Takeoff" position marker is almost never right, and on the two that my
club
now owns, we have our own marks where the tab id aligned with the
elevator.
Just my 2 cents worth,
John
Raven wrote:
>
> I hope this is a simple question: What should the effect of the takeoff
> trim setting in a C172 be? I ask this because I've rented two different
> 172s, and each has a much different reaction to the takeoff trim setting.
>
> The older (1968) aircraft, which is used primarily for low time students
> seems to have a rather neutral feel to the elevator at the takeoff
> setting. The plane stays on the ground until you apply very gentle
> backpressure to lift the nose off.
>
> The other aircraft is a year younger, and it wants to jump off the
> runway as soon as you have any speed. It tends to lift off on its own
> between 50 and 55 knots without any elevator input. I find I have to
> push the nose down to accelerate after liftoff before I can climb out.
>
> With a sample size of 2, I don't know which, if either, are behaving the
> way Cessna intended.
>
> Any other experience out there?
>
> -- Raven
Dennis Collin
>Any other experience out there?
I set the trim to neutral by the mark, and then during my walkaround I
confirm it by checking the trim tab ... should be deflected 1/4 to 1/2
inch BELOW the elevator. That usually works out about right ... YMMV
..
Dennis
PP-ASEL (4B8)
"I still know just enough to know that I don't know enough"
Gene Whitt
configurationof the last landing. While this setting can be changed, it will be at Vy under a
specific circumstance of having 1500 rpm, full (40-degrees) flaps, and trimmed for 60-knots on
final. Bringing up the flaps will create the Cessna engineered landing to takeoff relationship
that is designed for the go-around.
When the prior landing has been properly configured on final the next takeoff trim setting will be
for Vy. No changes are required for the Vy go-around or takeoff. I have used this in thousands
of landings. I use this inherent design to to fly hundreds of approaches into the missed.
Knowing the trim, power, and flap settings removes flying the aircraft from the equation as an
area of difficulty.
The original designs of the C-150 and C-172 were idealized with configuration, power and speed on
landings. The C-150 was trimmed level for the next takeoff or go-around because it tends to
protect the student. The C-172 was trimmed for the go-around or climb since it fit best into
its instrument training capablilties.
When the C-150 was changed into a C-152 many of these desirable qualities were lost. Others
were gained. When the C-172 was limited to 30-degrees of flaps to meet go-around performance
requirements a new set of relationships must be created.
Gene
snar...@my-dejanews.com
Gene Whitt <gwh...@ix.netcom.com> wrote:
What a low key entry back to the newsgroup! Welcome back, the newsgroup is all
the more richer...
Sriram
Robert Chilcoat
Gene,
I hadn't noticed before that you were back. Good to see you posting
again. You were missed.
Bob (44 hours and the Written under my belt)
If God had intended for man to fly, he would have given him more money.
Sandy Reutter
away.
Sandy
Dave Mould
> Are you setting takeoff trim by the marker next to the trim wheel, or by
> looking at the trim tab on the elevator? I set takeoff trim by pulling back on
> the yoke so I can see the elevator, and adjusting the trim wheel so the trim
> tab is level with the elevator. This aligns the trim wheel marker with the
> "takeoff" position on some 172P's, but not on others.
I've not though of doing it that way - I'll have to try it.
With most aircraft types, I set takeoff trim by running it all the way forward,
then winding it back "x" turns (or partial turns), with the "x" having been found
from experience. This seems to translate fairly well from aircraft to aircraft
of the same model, even though it often results in different positions of the
trim indicator. I guess the "stops" are better calibrated than the indicator?
OTOH, I'm not that worried with most aircraft where the stick load is light
enough to easily fly out-of-trim just after takeoff, I just re-trim to relieve
the stick pressure during the early part of the climb.
==========
Dave Mould
Not a QFI
==========
robert a barker
>
>Gene Whitt wrote:
>>
Gene:
Let me add my voice to the WELCOME BACK folks.I for one have missed
your wisdom.
Bob Barker
Roxana Murillo
visually checking the trim tab position aligned with the elevator. I
started doing this after I trimmed one of my school trainers and had to use
a lot of pressure to keep the plane from flying prematurely. I learned
afterwards that a sign near the trimming wheel had felt off. The sign read:
"Trim should be 1 inch above the takeoff trim mark for proper takeoff
trimming".
Francisco
Raven wrote in message <369A3C54...@birdland.sky>...
>I hope this is a simple question: What should the effect of the takeoff
>trim setting in a C172 be? I ask this because I've rented two different
>172s, and each has a much different reaction to the takeoff trim setting.
>
>The older (1968) aircraft, which is used primarily for low time students
>seems to have a rather neutral feel to the elevator at the takeoff
>setting. The plane stays on the ground until you apply very gentle
>backpressure to lift the nose off.
>
>The other aircraft is a year younger, and it wants to jump off the
>runway as soon as you have any speed. It tends to lift off on its own
>between 50 and 55 knots without any elevator input. I find I have to
>push the nose down to accelerate after liftoff before I can climb out.
>
>With a sample size of 2, I don't know which, if either, are behaving the
>way Cessna intended.
>
>Any other experience out there?
>
>-- Raven
Morris Bernstein
In article <369CE3...@erols.com>, Robert Chilcoat wrote:
>Gene Whitt wrote:
>Gene,
>
>I hadn't noticed before that you were back. Good to see you posting
>again. You were missed.
At the risk of making yet another me too post, that was exactly my
reaction. :-)
Morris (who usually tries to post more content than noise)
--
Morris Bernstein mor...@blarg.net
Spammers beware: I may respond in a way you _won't_ like
RANDOM FORTUNE COOKIE:
You can fool all the people all of the time if the advertising is right
and the budget is big enough.
-- Joseph E. Levine
St Stephen Ames
little effect on the ground anyhow and soon as practical I trim to
relieve as I climb...
--
Till the next time,
St Stephen Ames
43.2 Total hrs(26.8hrs dual, 16.4hrs solo, 190 landings!)
http://www.stephenames.com
"When my abilities meet my desire & commitment, I will be one hell of a
pilot!" - S. Ames
Personal flying site:
http://www.stephenames.com/flying/flying.html
Mack Gridley
I guess I have flown about 6 or 7 different C172s during training, and
since gaining my PPL about 18 months ago. Most of them were C172Ns, apart
from one which was brand new - which someone was fool enough to let me
rent.
In all cases, the planes behaved as you described your older (1968)
aircraft, that is with the trim correctly set for take off, a very gentle
backpressure was always needed to lift the nose wheel.
The only time when this did not happen was during an early solo touch and
go, I forgot to raise the flaps! The plane started wollowing along in
ground effect at about 40 knots! Fortunately I remembered not to retract
all my flaps at once.
By the way, how much does a C172 cost to rent over there? Here in
Australia its about $A115 per hr fuel included (about $75 US).
Mack.
Dennis Collin
<ste...@stephenames.com> wrote:
>I always set the wheel to the takeoff position marked since the tab has
>little effect on the ground anyhow and soon as practical I trim to
>relieve as I climb...
Don't you believe it! It's USUALLY ok to set the wheel to the
takeoff position by the mark, but not always!
The elevator trim tab has the same effect on the ground as in the air
... as soon as there's enough air moving over the elevator to give it
authority, the tab will function as it should. A misadjusted trim tab
can either launch you off with a nose high attitude before you and the
plane are ready , or leave you rolling longer than you'd like and
pulling like crazy on the yoke as the runway slips away beneath you.
Both are disconcerting when my attention is focused elsewhere (like on
the engine instruments during the early take off roll, or on the end
of the runway during a short field take off.). Neither are inherently
DANGEROUS unless the pilot fails to respond quickly and appropriately.
As you say, once off the ground, I trim immediately to get Vx or Vy
depending on the circumstances.
The fewer surprises I encounter during any flight, the happier I am
.. grin!
Tina Marie
Dennis Collin <dco...@connix.com> wrote:
>Don't you believe it! It's USUALLY ok to set the wheel to the
>takeoff position by the mark, but not always!
Yes. While this discussion is about 172s, there are airplanes
which will not climb if not trimmed correctly. Planes which
trim with a stabilator instead of a trim tab are more suseptable
to this...
Know your plane.
Tina Marie
--
skydiver - PP-ASEL \*\ An apostrophe does not mean, "Yikes!
http://www.neosoft.com/~tina \*\ Here comes an 's'!" - Dave Barry
Brett Rabe
>
> I always set the wheel to the takeoff position marked since the tab has
> little effect on the ground anyhow and soon as practical I trim to
> relieve as I climb...
You may already do this, but it's hard to tell from your
post ...
It's probably wise to give a glance out the back at the
elevator trim to make sure it is in the desired position.
The trim position indicator is often not exceptionally
accurate. Of course, this only makes sense if you can
see the elevator from the pilot's seat in the plane you
fly. :-)
Brett
--
Brett Rabe Email : br...@uswest.net
Systems Administrator - U S West Phone : 612.664.3078
Interact - 3S Pager : 612.613.2549
600 Stinson Blvd. Fax : 612.664.4770
Minneapolis, MN 55413 USA Pager : page-...@uswest.net
I don't have an attitude problem. You have a perception problem.
Raven
Mack Gridley wrote:
>
>
> By the way, how much does a C172 cost to rent over there? Here in
> Australia its about $A115 per hr fuel included (about $75 US).
>
> Mack.
Up my way the C172s are going for $60US/hr wet. I don't know how that
compares with other places. I've really only got one FBO within a
reasonable drive.
Thanks everyone for your comments. For my own comfort I'll probably
trim the second aircraft a little nose low. I don't actually know if
the takeoff trim setting is nose high enough to cause a stall, but it
feels like it. I'll have to check that out sometime at altitude.
-- Raven
Richard L. Watson
where the trim setting needs to be with your normal load so
that the plane will just fly itself off at the correct
airspeed with no pull back on the yoke. At least in the
case of a C-172 that I fly all of the time, this trim
setting will turn out to be just about perfect for the
climb. If you have more weight in the front, roll it back a
bit. If you have more weight in the back seat roll it
forward a bit before your takeoff roll. No surprises this
way and you will need only the slightest adjustment for
climb.
Richard
Roger Halstead
EAA Chapter 1093 Secretary and N.L. Editor
Tina Marie wrote in message <77ldne$19k$1...@Starbase.NeoSoft.COM>...
>In article <369e0b1e...@news.connix.com>,
>Dennis Collin <dco...@connix.com> wrote:
>>Don't you believe it! It's USUALLY ok to set the wheel to the
>>takeoff position by the mark, but not always!
If the trim wheel is not near the mark then something is not quite right, or
as in the POH for my Debonair it states "set trim to take off position or
about 1/4 inch forward if only the front seats are occupied.
Also in mine the take off trim is not neutral, but fairly close.
If you forget and leave it in the landing position it gets really busy on
take off. When I was first getting checked out I was conveniently
interrupted by the instructor and forgot to trim the nose down.
On the Debonair with the 260 HP engine I almost wanted to keep both hands on
the yoke to hold the nose down. It takes a lot of pressure while trying to
reach the trim wheel which is under the instrument panel and completely out
of sight.
Roger
Mackfly
>Australia its about $A115 per hr fuel included (about $75 US).
>
>Mack.
Hey Mack we rent Ces 172s for $52.00 an hour wet at CBF--Council Bluffs
Iowa--Mack
Dennis Collin
>If the trim wheel is not near the mark then something is not quite right, or
>as in the POH for my Debonair it states "set trim to take off position or
>about 1/4 inch forward if only the front seats are occupied.
Sure ... it could be mis-rigged. I rented a 172 like that last
weekend ... and didn't check it visually on the walkaround. I found
myself pushing the nose down as I accelerated through 40 knots until I
was ready to rotate at 60 ...
A couple of weeks ago, I flew a 172 that I had to "yank" off the
runway ... I had better than 70 knots goin' before I decided to be
more decisive.
I like the 172 trimmed at takeoff so a slight back pressure on the
yoke will result in rotation at 60 knots and liftoff at 65-70 knots.
>Also in mine the take off trim is not neutral, but fairly close.
>If you forget and leave it in the landing position it gets really
>busy on take off.
Interesting ... in the C172, I find that the position of the trim
after landing (with flaps) is most nearly the correct trim for
takeoff, regardless of the mark on the trim wheel ... must be a quirk
of the C172 airframe.
In any case, unless the trim is WAY off, or the indicator mark is WAY
off, a slight mis-trim at takeoff just means that I have to feel the
plane and give it what it needs ... and I'm finding more and more
that's what differentiates the pilot from the student. At 80+ hours,
I'm in that gray in-between area ... grin!
>On the Debonair with the 260 HP engine I almost wanted to keep both hands on
>the yoke to hold the nose down. It takes a lot of pressure while trying to
>reach the trim wheel which is under the instrument panel and completely out
>of sight.
For us very low-timers, even a 160 hp C172 can be a handful.
Snowbird
> Interesting ... in the C172, I find that the position of the trim
> after landing (with flaps) is most nearly the correct trim for
> takeoff, regardless of the mark on the trim wheel ... must be a quirk
> of the C172 airframe.
Not quirk...full flaps landing trim designed to be ~takeoff trim
without flaps, said to be designed in by Cessna. Also true
of C150.
Watch out for landing without flaps (as in power-off landing).
Climb-out will require significant forward pressure until trim
is adjusted.
Snowbird
Dennis Collin
>Not quirk...full flaps landing trim designed to be ~takeoff trim
>without flaps, said to be designed in by Cessna. Also true
>of C150.
Didn't know it was by design. Ideal for trainers often used in touch
and go operations!
>Watch out for landing without flaps (as in power-off landing).
>Climb-out will require significant forward pressure until trim
>is adjusted.
Yep ... BTDT ... takes a lot of nose up trim to slow a C172 to 65
knots for landing without flaps. During training my instructor
demonstrated by having me do a go-around with full flaps and then with
no flaps. While both required me to keep the nose down, it was
tougher after the no flaps approach.
dion.m...@pobox.com
dco...@connix.com (Dennis Collin) wrote:
...
> Interesting ... in the C172, I find that the position of the trim
> after landing (with flaps) is most nearly the correct trim for
> takeoff, regardless of the mark on the trim wheel ... must be a quirk
> of the C172 airframe.
>
> Dennis
> PP-ASEL (4B8)
>
I've noticed the same thing on Piper Warriors, anyone else?
Dion
Brett Rabe
> Not quirk...full flaps landing trim designed to be ~takeoff trim
> without flaps, said to be designed in by Cessna. Also true
> of C150.
Huh. I've never noticed that; I will have to check the
next time I fly one. Thanks for pointing it out.
Brett
--
Brett Rabe Email : br...@uswest.net
Systems Administrator - U S West Phone : 612.664.3078
Interact - 3S Pager : 612.613.2549
600 Stinson Blvd. Fax : 612.664.4770
Minneapolis, MN 55413 USA Pager : page-...@uswest.net
The older you get, the better you realize you were.
mike schreiner
forward pitching moment. The mark on the trim wheel IS the correct setting
for takeoff (+/- about one needle width depending upon CG) so either you are
not trimming properly or you are driving the airplane onto the runway in a 3
point attitude.
--MS
dion.m...@pobox.com wrote in message
<77o3lg$o72$1...@nnrp1.dejanews.com>...