c-152 rudder???

wrote:

There was an accident here in Canada that resulted in a Canadian
AD forcing modification of the stops. A student and instructor were
killed when the rudder locked hard over when entering a practice spin
and they couldn't stop the rotation, thereby preventing spin recovery.

That was already posted on this thread. However, that aircraft had lots
of unrepaired and mismaintenance with regard to the tail that exacerbated
the problem. Still getting back to the original assertion, had they not
been in a spin already when it locked up, it probably wouldn't have been
an issue.

No, it wouldn't, but it's still not safe. If things are that
worn and beat up, what else on the airplane is waiting to bite someone?
Further, if a pilot inadvertently enters an incipient spin because of
mishandling, he will, if trained properly, use opposite rudder to
recover, and he might do it fast and hard and get rudder lockup and
control loss.
In Canada spin training is mandatory for Commercial students. The
airplanes have to be maintained properly, like they should be anyway. I
see lots of horror stories when I look at some neglected airplanes that
are still being flown, and wonder why there aren't more accidents.
Dan

wrote:
No, it wouldn't, but it's still not safe. If things are that
worn and beat up, what else on the airplane is waiting to bite someone?

Much indeed. Did you read the report? That aircraft had other
serious problems: eppenage structural damage repaired with tape,
rudder cable tension problems, etc...

wrote:
AD forcing modification of the stops. A student and instructor were
killed when the rudder locked hard over when entering a practice spin
and they couldn't stop the rotation, thereby preventing spin
recovery.

btw, according to the accident report (you should be able to find it
somewhere
on www.tsb.gc.ca), the student didn't die, but did sustain serious
injuries,
since they spun into a lake.

And if you haven't read the accident report, there was a bunch of
stuff,
including a rudder return spring missing, that contributed to the
rudder
jamming hard over. They couldn't get the rudder to jam over when it was
just
a worn stop bolt, but they recommended an SB for the stop bolt anyhow.
It's well worth the read, rick
ps: And it was a C150, not C152.

A broken rudder return spring won't contribute much, if any, to
the stop-locking problem, but it will make the airplane fly cockeyed
unless you hold pedal pressure against the good spring. We used to run
two 150s, and had (and still do have) springs break at various times
both in the 150s and 172s. The pilot complains of really bad rudder
trim. The rudder cable tension is determined by the springs, and isn't
very high at any time.
As I said earlier, the stop bolts don't wear that much. It's worn
hinges and loose bellcranks that allow the little hook on the stop to
ride past the bolt head and get caught. Ironically, it's the same
little hook that's supposed to prevent the override. Seeing a good stop
doesn't mean there's no problem. There are likely very few 150/152s
like this, but it's worth getting it checked at annual. The new stops
have no hook and are much longer and wider, and the stop bolt has a
larger head.

Dan

Losing the rudder cleanly would probably be survivable as students have
been ignoring it for years. However, I contend that losing both the
rudder and the vertical fin would almost certainly cause a crash. Any
use of the ailerons in that circumstance would create a slight amount
of adverse yaw moment that would have almost no reaction surface. The
fuselage rear cone (especially on a later small tailcone diameter 150s)
would not be very effective restoring moment just at the time when you
would want to use a lot of the ailerons to get a semblance of steering.


There is redundancy in the aileron system. There is no redundancy in
the rudder/fin system.

I do recall a picture in Aviation Week many years ago though that
showed a B-52 with the whole vertical fin and rudder gone from a
thunderstorm. Otherwise it would be the Sioux City DC-10 accident all
over again but without the possibilities of differential engine thrust.
No thanks.

The Cessna's aileron control system uses bellcranks in
the wings, with pushrods from the bellcranks to the aileron, and cables
from the bellcranks to the control wheels. A departed aileron would
hopefully take the rod off and leave the airplane, and the bellcranks
should continue to operate. If the rod didn't fail, or iff the
bellcrank was damaged, the whole system would be fouled up. An airplane
such as a Cub, or my Jodel, that has cables directly to the ailerons,
would have no aileron control at all if one aileron failed. All the
cable tensions are gone. You might have control in one direction, and
not the other.

Dan

The issue on the 150/152 is the vertical stabilizer attachment and not
the rudder. See http://www.cessna150-152.com/acs-vtab.htm



Posted Via Usenet.com Premium Usenet Newsgroup Services
----------------------------------------------------------
** SPEED ** RETENTION ** COMPLETION ** ANONYMITY **
----------------------------------------------------------
http://www.usenet.com

Well, there we are. The FAA isn't concerned about the rudder stops;
only Cessna and the Canadian Government are. The fin attach is what the
FAA wants looked at, and it seems to be age-related as the rate of SDR
reports comes up. They also mention horizontal stab spar cracking,
which has been an issue in 172s for years and is (in the 172, at least)
often caused by folks pushing down on the stab to turn the airplane on
the ground.
I would anticipate many more issues arising as the fleet ages.
Our older 172s are beginning to show the odd crack here and there, and
Cessna sends out Service Bulletins that we take seriously and we often
find problems where they tell us to look. There are 172s here in Canada
with almost 20,000 hours on them, still flying, but they require
watching. I don't think Cessna ever intended them to last so long. I
wish new ones cost less.

Dan

wrote:
A broken rudder return spring won't contribute much, if any, to
the stop-locking problem, but it will make the airplane fly cockeyed
unless you hold pedal pressure against the good spring. We used to
run
two 150s, and had (and still do have) springs break at various times
both in the 150s and 172s. The pilot complains of really bad rudder
trim. The rudder cable tension is determined by the springs, and
isn't
very high at any time.

Well, the report is at
http://www.tsb.gc.ca/en/reports/air/...4/a98q0114.asp
and it clearly states that they were only able to reproduce the case
where the rudder jammed past the stop bolt by removing the rudder
return
spring. It's about 2/3rds of the way through the document, after all
the
stuff about CARs violations. (It sounds like slackness of the rudder
cable
was the deciding factor.) It also required up elevator to allow it to
go
past the stop bolt(but of course that would be the case when doing an
intentional spin).

Interesting reading. Oh, and I was incorrect before, it was a C152,
rick