What is a "Forward Skip"?

[Gary G]

Hi folks - I'm somewhat new to flying.

I heard references to "forward slip" to get rid of altitude on approach.

Can someone give me the 2 sentence (or how ever many is adequate) to
what a forward slip procedure is?

Thanks!

Gary

[569]

Slip into the wind. Add hard right rudder, turn the yoke hard left,
add some forwad pressure. This exposes more of the surface to the
wind, and you're able to loss more altitude, without a noticable gain
in airspeed. Some aircraft prhobit slips with flaps extended, others
make no mention.

[G.R. Patterson III]

Gary G wrote:
>
> Can someone give me the 2 sentence (or how ever many is adequate) to
> what a forward slip procedure is?

When you drop one wing (let's say the right wing) by using the ailerons and use
rudder to turn the nose in the opposite direction (left, in this case), the
plane will fly sideways. That's a slip. If you fly the plane so that it
continues to fly the same course it was flying, that's a forward slip.

Here's a link to another explanation -
http://www.airliners.net/discussions/tech_ops/read.main/48323

George Patterson
The desire for safety stands against every great and noble enterprise.

[Edwin Johnson]

On 2005-01-06, 569 > wrote:

> wind, and you're able to loss more altitude, without a noticable gain
> in airspeed. Some aircraft prhobit slips with flaps extended, others

Also note that some of the older aircraft and some of the present homebuilts
and experimentals had no flaps, so this was the main method of losing
altitude on landing approach if a steep glide path was needed, such as over
obstacles. A good reason this is needed and should be practiced today is in
the event the flaps become inoperative in the case of an engine out or other
emergency.

....Edwin
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~ Edwin Johnson ....... ~
~ http://www.shreve.net/~elj ~
~ ~
~ "Once you have flown, you will walk the ~
~ earth with your eyes turned skyward, ~
~ for there you have been, there you long ~
~ to return." -- da Vinci ~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[Slip'er]

> I heard references to "forward slip" to get rid of altitude on approach.

Both prior posts pretty much nailed it. A forward slip can be made either
to the left or right. Basically, you intentionally use cross controls
(rudder & aeleron). I believe that a forward slip generally refers to using
a slip to keep the aircraft aligned with the runway for landing in a
crosswind. This could mean landing on one wheel to maintain directional
orientation. This is my preferred approach when flying in a cross wind in a
taildragger.

A side slip is similar but in this scenario, the slip is can be more
aggressive. A side slip is used to shed altitude.

When practicing slips, be careful. Remember, you are intentionally using
cross-controls near the ground where inadvertant spin recovery could be
impossible.

I got my call sign "slip'er" because I thought that they were so fun I
always come in high and slip it in.

[Peter R.]

569 ) wrote:

> Some aircraft prhobit slips with flaps extended,

Which ones?

--
Peter

[569]

The Cessna 172R has a placard, "Avoid Slips with Flaps Extended". Now
it says, "avoid". It does not say that you can't do it. There was a
discussion in Flight Training Mag about 6 months ago that talked about
that same thing. In the Cessna 152 I always have full flaps in a slip.
I don;t truely understand why having flaps is a problem in the 172R.

[Bob Moore]

"Slip'er" > wrote

>> I heard references to "forward slip" to get rid of altitude on
>> approach.
>
> Both prior posts pretty much nailed it. A forward slip can be made
> either to the left or right. Basically, you intentionally use cross
> controls (rudder & aeleron). I believe that a forward slip generally
> refers to using a slip to keep the aircraft aligned with the runway
> for landing in a crosswind. This could mean landing on one wheel to
> maintain directional orientation. This is my preferred approach when
> flying in a cross wind in a taildragger.
>
> A side slip is similar but in this scenario, the slip is can be more
> aggressive. A side slip is used to shed altitude.

I do believe that you have them reversed..........

From http://www.airbum.com/articles/ArticleSlips.html

The old fashioned forward slip is one of those maneuvers that on one hand
would appear to be redundant to modern flap systems. At the same time,
it's one of those basic maneuvers that if understood and practiced gives
the pilot yet another tool enabling him to put the airplane exactly where
he wants it on approach.

Unless we're talking about the so-called side slip in which a slipping
motion to the side is canceled out by the crosswind so the airplane
tracks straight.

Bob Moore
ATP CFI

[Flyin'[email protected]]

Cessna 172M

"Avoid slips with full flap extension"



Peter R. > wrote:
> 569 ) wrote:
>
> > Some aircraft prhobit slips with flaps extended,
>
> Which ones?

--
Mike Flyin'8

PP-SEL

[Jose]

> Can someone give me the 2 sentence (or how ever many is adequate) to
> what a forward slip procedure is?

Previous posters have given you good answers. I'll add that a "side
slip" is exactly the same thing as a forward slip. In both cases, (in
calm air) the aircraft is pointed in a different direction from the
way it's going. We say "side slip" when we are =thinking= about it
with respect to the direction we are pointed, and we say "forward
slip" when we are =thinking= about it with respect to the direction we
want to go. But the maneuver is identical, and the essential
character is that the plane goes sideways =through=the=air= to some
degree.

Note also this is different from "crabbing", which arises from flying
through air that is moving along the ground. The airplane does not
know what the ground is doing, and flies straight ahead through the
air. But if the air moves along the ground, it takes the plane with
it, and the combined motion can make it look like the airplane is
moving "sideways" to some degree. Nonetheless, unless the pilot is
doing something else at the same time, the airplane is going
=through=the=air= straight forwards.

Jose
--
Money: What you need when you run out of brains.
for Email, make the obvious change in the address.

[Peter R.]

) wrote:

> Cessna 172M
>
> "Avoid slips with full flap extension"

Are the words "avoid" and "prohibited" interchangeable? :)

--
Peter

[Flyin'[email protected]]

In the context it is used, and for my level of flying experience, yes they
are interchangeable. I do not know more about the danger of this than
Cessna, so I would prefer to trust what they say. You level of experience
is certainly different that mine, so your decision may be different than
mine.

That is not say that in the event of emergency I would not perform a slip
to land with full flaps if the need dictated.


Peter R. > wrote:
> ) wrote:
>
> > Cessna 172M
> >
> > "Avoid slips with full flap extension"
>
> Are the words "avoid" and "prohibited" interchangeable? :)

--
Mike Flyin'8
PP-SEL

[BTIZ]

and maintain the same ground track.. like the extended centerline on final..
the longitudinal axis of the glider is not lined up with the runway.. but
the ground track is.. a forward slip..

now.. use left bank, and enough right rudder to maintain the longitudinal
axis parallel to the runway centerline.. and you have a side slip.. the idea
is to have just enough slide slip to counter act the cross wind component..
and you land on centerline without any side loads to the landing gear..

in the absence of any wind.. the maneuver would be a slow drift to the side
of the runway to which banked.. with the fuselage parallel to the runway

BT

"569" > wrote in message
oups.com...
> Slip into the wind. Add hard right rudder, turn the yoke hard left,
> add some forwad pressure. This exposes more of the surface to the
> wind, and you're able to loss more altitude, without a noticable gain
> in airspeed. Some aircraft prhobit slips with flaps extended, others
> make no mention.
>

[BTIZ]

slip'er... you have them reversed..

"Slip'er" > wrote in message
news:sadDd.40751$8e5.1828@fed1read07...
>> I heard references to "forward slip" to get rid of altitude on approach.
>
> Both prior posts pretty much nailed it. A forward slip can be made either
> to the left or right. Basically, you intentionally use cross controls
> (rudder & aeleron). I believe that a forward slip generally refers to
> using
> a slip to keep the aircraft aligned with the runway for landing in a
> crosswind. This could mean landing on one wheel to maintain directional
> orientation. This is my preferred approach when flying in a cross wind in
> a
> taildragger.
>
> A side slip is similar but in this scenario, the slip is can be more
> aggressive. A side slip is used to shed altitude.
>
> When practicing slips, be careful. Remember, you are intentionally using
> cross-controls near the ground where inadvertant spin recovery could be
> impossible.
>
> I got my call sign "slip'er" because I thought that they were so fun I
> always come in high and slip it in.
>
>

[kontiki]

With full flaps its easy to end up real slow in a slip and approach a stall.

wrote:

> In the context it is used, and for my level of flying experience, yes they
> are interchangeable. I do not know more about the danger of this than
> Cessna, so I would prefer to trust what they say. You level of experience
> is certainly different that mine, so your decision may be different than
> mine.
>
> That is not say that in the event of emergency I would not perform a slip
> to land with full flaps if the need dictated.
>
>
> Peter R. > wrote:
>
>> ) wrote:
>>
>>
>>>Cessna 172M
>>>
>>>"Avoid slips with full flap extension"
>>
>>Are the words "avoid" and "prohibited" interchangeable? :)
>
>

[Peter Duniho]

"Gary G" > wrote in message
...
> Can someone give me the 2 sentence (or how ever many is adequate) to
> what a forward slip procedure is?

I guess that's what we get for answering Ramapriya's questions. We're
turning into rec.aviation.student.

[Peter Duniho]

"kontiki" > wrote in message
...
> With full flaps its easy to end up real slow in a slip and approach a
> stall.

Not with the proper control inputs it's not, nor is that in any way related
to the C172 warning to avoid slips with full flaps.

[Peter R.]

) wrote:

> In the context it is used, and for my level of flying experience, yes they
> are interchangeable. I do not know more about the danger of this than
> Cessna, so I would prefer to trust what they say. You level of experience
> is certainly different that mine, so your decision may be different than
> mine.

Sorry, Mike, I was just having some fun with an urban legend, not trying
to come across as some "long in tooth" experienced aviator. I am afraid
I have a long way to go for that title. :)

As a former owner of a late model Cessna 172, I can tell you that the
"Avoid slips with full flaps" is a Cessna recommendation based the
possibility of some oscillation in the yoke, which can be disconcerting
to a pilot not expecting it. (This is a paraphrase of the POH). This
recommendation has nothing to do with the possibility of a resulting
tail-plane stall and nose-over into the ground, which is where the fear
of avoiding slips with full flaps may have originated.

Is there an older model C172 where re-directed airflow actually can
negatively affect the horizontal stabilizer? I don't definitively know
as I certainly do not know the characteristics of a lot of small
aircraft. However, I don't recall reading about a specific example in
this newsgroup the many times this topic surfaced in the past.

I have slipped with full flaps while practicing emergency descents in
the C172SP and have experienced this oscillation of the yoke; it moves
in and out about a 1/2 or so in either direction and was pretty docile.

--
Peter

[Stefan]

Edwin Johnson wrote:

> Also note that some of the older aircraft and some of the present homebuilts
> and experimentals had no flaps,

And even others don't have enough forward view, so flying sideways is
the only possibility to see the runway on final.

Stefan

[AnthonyQ]

I was told many years ago that a full rudder slip in a C172 (especially the
older models with 40deg flaps), it is possible to induce a tail stall....not
good close to the ground....

Anthony Q


"Peter Duniho" > wrote in message
...
> "kontiki" > wrote in message
> ...
> > With full flaps its easy to end up real slow in a slip and approach a
> > stall.
>
> Not with the proper control inputs it's not, nor is that in any way
related
> to the C172 warning to avoid slips with full flaps.
>
>

[Happy Dog]

"569" > wrote in message news:
> The Cessna 172R has a placard, "Avoid Slips with Flaps Extended". Now
> it says, "avoid". It does not say that you can't do it. There was a
> discussion in Flight Training Mag about 6 months ago that talked about
> that same thing. In the Cessna 152 I always have full flaps in a slip.
> I don;t truely understand why having flaps is a problem in the 172R.

The aircraft tends to oscillate on the pitch axis. It's never been shown to
be a hazard though. Just feels a bit weird.

le m

[Happy Dog]

"kontiki" > wrote in message
> With full flaps its easy to end up real slow in a slip and approach a
> stall.

It's easy without flaps too. Stalling isn't the real danger though, it's
spinning. With proper elevator input though, there's no danger of either.
And, this has nothing to do with Cessna's warning.

moo


>
> wrote:
>
>> In the context it is used, and for my level of flying experience, yes
>> they
>> are interchangeable. I do not know more about the danger of this than
>> Cessna, so I would prefer to trust what they say. You level of
>> experience
>> is certainly different that mine, so your decision may be different than
>> mine.
>>
>> That is not say that in the event of emergency I would not perform a slip
>> to land with full flaps if the need dictated.
>>
>>
>> Peter R. > wrote:
>>
>>> ) wrote:
>>>
>>>
>>>>Cessna 172M
>>>>
>>>>"Avoid slips with full flap extension"
>>>
>>>Are the words "avoid" and "prohibited" interchangeable? :)
>>
>>
>

[kontiki]

Peter Duniho wrote:
> Not with the proper control inputs it's not, nor is that in any way related
> to the C172 warning to avoid slips with full flaps.
>
>

Well of course. Proper control inputs 100% of the time would eliminate at least
50% of the accidents.

[kontiki]

Spinning requires a stall.

Happy Dog wrote:

> "kontiki" > wrote in message
>
>>With full flaps its easy to end up real slow in a slip and approach a
>>stall.
>
>
> It's easy without flaps too. Stalling isn't the real danger though, it's
> spinning. With proper elevator input though, there's no danger of either.
> And, this has nothing to do with Cessna's warning.
>
> moo
>
>
>
wrote:
>>
>>
>>>In the context it is used, and for my level of flying experience, yes
>>>they
>>>are interchangeable. I do not know more about the danger of this than
>>>Cessna, so I would prefer to trust what they say. You level of
>>>experience
>>>is certainly different that mine, so your decision may be different than
>>>mine.
>>>
>>>That is not say that in the event of emergency I would not perform a slip
>>>to land with full flaps if the need dictated.
>>>
>>>
>>>Peter R. > wrote:
>>>
>>>
) wrote:
>>>>
>>>>
>>>>
>>>>>Cessna 172M
>>>>>
>>>>>"Avoid slips with full flap extension"
>>>>
>>>>Are the words "avoid" and "prohibited" interchangeable? :)
>>>
>>>
>
>

[Stefan]

kontiki wrote:

>> It's easy without flaps too. Stalling isn't the real danger though,
>> it's spinning.

> Spinning requires a stall.

But any properly trained low time student can recover from a stall
without spinning.

Stefan

[kontiki]

I would not necessarily go so far as to say that. Working on my CFI
I had to undergo spin training... actually recovering from spins
multiple times. That training is not nromally a part of student
pilot training.

Remember that a spin requires a stall of one wing... the other
can be flying quite normally. Students are typically tought stalls
under coordinated conditions.

Stefan wrote:

> kontiki wrote:
>
>>> It's easy without flaps too. Stalling isn't the real danger though,
>
> >> it's spinning.
>
> > Spinning requires a stall.
>
> But any properly trained low time student can recover from a stall
> without spinning.
>
> Stefan

[Peter Duniho]

"AnthonyQ" > wrote in message
...
>I was told many years ago that a full rudder slip in a C172 (especially the
> older models with 40deg flaps), it is possible to induce a tail stall

You were told wrong.

[Peter Duniho]

"kontiki" > wrote in message
...
> Well of course. Proper control inputs 100% of the time would eliminate at
> least
> 50% of the accidents.

The point is that flaps don't change the control inputs required to avoid a
stall in a slip. If anything, they make a stall less likely, since they
lower the stall speed.

[kontiki]

In theory of course. In the case of the 172 with 40 degrees of flaps they
contribute more drag than lift.

Peter Duniho wrote:
> "kontiki" > wrote in message
> ...
>
>>Well of course. Proper control inputs 100% of the time would eliminate at
>>least
>>50% of the accidents.
>
>
> The point is that flaps don't change the control inputs required to avoid a
> stall in a slip. If anything, they make a stall less likely, since they
> lower the stall speed.
>
>

[kontiki]

well, let me be more specific: the last 40 degrees contributes
more overall drag than lift.

kontiki wrote:
> In theory of course. In the case of the 172 with 40 degrees of flaps they
> contribute more drag than lift.
>
> Peter Duniho wrote:
>
>> "kontiki" > wrote in message
>> ...
>>
>>> Well of course. Proper control inputs 100% of the time would
>>> eliminate at least
>>> 50% of the accidents.
>>
>>
>>
>> The point is that flaps don't change the control inputs required to
>> avoid a stall in a slip. If anything, they make a stall less likely,
>> since they lower the stall speed.
>>
>

[Peter Duniho]

"kontiki" > wrote in message
...
> In theory of course. In the case of the 172 with 40 degrees of flaps they
> contribute more drag than lift.

In practice too. The relative amounts of drag and lift are irrelevant to
the fact that using the flaps lowers the stall speed, and that doing so does
not make it any easier "to end up real slow in a slip".

Your assertion that "With full flaps its easy to end up real slow in a slip
and approach a stall" is just plain nonsense, and certainly has nothing to
do with the *warning* (not prohibition) against slipping while flaps are
extended (even if there were something to your claim about flaps making it
easier to stall).

Pete

[kontiki]

whatever.

Peter Duniho wrote:

> "kontiki" > wrote in message
> ...
>
>>In theory of course. In the case of the 172 with 40 degrees of flaps they
>>contribute more drag than lift.
>
>
> In practice too. The relative amounts of drag and lift are irrelevant to
> the fact that using the flaps lowers the stall speed, and that doing so does
> not make it any easier "to end up real slow in a slip".
>
> Your assertion that "With full flaps its easy to end up real slow in a slip
> and approach a stall" is just plain nonsense, and certainly has nothing to
> do with the *warning* (not prohibition) against slipping while flaps are
> extended (even if there were something to your claim about flaps making it
> easier to stall).
>
> Pete
>
>

[Bob Moore]

"AnthonyQ" wrote

> I was told many years ago that a full rudder slip in a C172
> (especially the older models with 40deg flaps), it is possible to
> induce a tail stall....not good close to the ground....

From the book "Cessna, Wings for the World" by William Thompson,
Manager-Flight Test and Aerodynamics for the Cessna Aircraft
Company where he also served as an Engineering Test Pilot and
other positions for a total of 28 years.

"With the advent of the large slotted flaps in the C-170, C-180, and C-
172 we encountered a nose down pitch in forward slips with the wing flaps
deflected. In some cases it was severe enough to lift the pilot against
his seat belt if he was slow in checking the motion. For this reason a
caution note was placed in most of the owner's manuals under "Landings"
reading "Slips should be avoided with flap settings greater than 30° due
to a downward pitch encountered under certain combinations of airspeed,
side-slip angle, and center of gravity loadings". Since wing-low drift
correction in cross-wind landings is normally performed with a minimum
flap setting (for better rudder control) this limitation did not apply to
that maneuver. The cause of the pitching motion is the transition of a
strong wing downwash over the tail in straight flight to a lessened
downwash angle over part of the horizontal tail caused by the influence
of a relative "upwash increment" from the upturned aileron in slipping
flight. Although not stated in the owner's manuals, we privately
encouraged flight instructors to explore these effects at high altitude,
and to pass on the information to their students. This phenomenon was
elusive and sometimes hard to duplicate, but it was thought that a pilot
should be aware of its existence and know how to counter-act it if it
occurs close to the ground.
When the larger dorsal fin was adopted in the 1972 C-172L, this side-slip
pitch phenomenon was eliminated, but the cautionary placard was retained.
In the higher-powered C-172P and C-R172 the placard was applicable to a
mild pitch "pumping" motion resulting from flap outboard-end vortex
impingement on the horizontal tail at some combinations of side-slip
angle, power, and airspeed."

This is probably as close to the real story as we will get.

Bob Moore
ATP CFI
PanAm (retired)

[Happy Dog]

"kontiki" > wrote in message

> Spinning requires a stall.

Thanks Amelia. A properly trained pilot can recover from a stall during a
slip on final unless they're really close to the ground. (That might happen
on a real forced approach trying to put it down on an impossibly short
rea. - Cue new thread.) A recovery from a spin on final is
near-impossible. OK?

le moo

>
> Happy Dog wrote:
>
>> "kontiki" > wrote in message
>>
>>>With full flaps its easy to end up real slow in a slip and approach a
>>>stall.
>>
>>
>> It's easy without flaps too. Stalling isn't the real danger though, it's
>> spinning. With proper elevator input though, there's no danger of
>> either. And, this has nothing to do with Cessna's warning.
>>
>> moo
>>
>>
>>
wrote:
>>>
>>>
>>>>In the context it is used, and for my level of flying experience, yes
>>>>they
>>>>are interchangeable. I do not know more about the danger of this than
>>>>Cessna, so I would prefer to trust what they say. You level of
>>>>experience
>>>>is certainly different that mine, so your decision may be different than
>>>>mine.
>>>>
>>>>That is not say that in the event of emergency I would not perform a
>>>>slip
>>>>to land with full flaps if the need dictated.
>>>>
>>>>
>>>>Peter R. > wrote:
>>>>
>>>>
) wrote:
>>>>>
>>>>>
>>>>>
>>>>>>Cessna 172M
>>>>>>
>>>>>>"Avoid slips with full flap extension"
>>>>>
>>>>>Are the words "avoid" and "prohibited" interchangeable? :)
>>>>
>>>>
>>
>>
>

[Happy Dog]

"kontiki" > wrote in message

>> But any properly trained low time student can recover from a stall
>> without spinning.
>>
>> Stefan
>
>I would not necessarily go so far as to say that. Working on my CFI
> I had to undergo spin training... actually recovering from spins
> multiple times. That training is not nromally a part of student
> pilot training.

Yeah. Drag that. It is in Canada. Requirement on CPL test.
>
> Remember that a spin requires a stall of one wing... the other
> can be flying quite normally. Students are typically tought stalls
> under coordinated conditions.

Have you stalled in a slip? It's no harder to recover than any other power
off stall. Which wing drops?

Moo

PS Try not to top post.


>
> Stefan wrote:
>
>> kontiki wrote:
>>
>>>> It's easy without flaps too. Stalling isn't the real danger though,
>>
>> >> it's spinning.
>>
>> > Spinning requires a stall.
>>

[Happy Dog]

"kontiki" > wrote in message news:t%hDd.

>> Peter Duniho wrote:.
>>
>>>Well of course. Proper control inputs 100% of the time would eliminate at
>>>least 50% of the accidents.
>> The point is that flaps don't change the control inputs required to
>> avoid a stall in a slip. If anything, they make a stall less likely,
>> since they lower the stall speed.

> In theory of course. In the case of the 172 with 40 degrees of flaps they
> contribute more drag than lift.

In reality.

moo

[Happy Dog]

Top posting idiot. If you have no interest in actually discussing aviation,
go elsewhere. Or, at least, thank the other poster for correcting your
misinformation for the benefit of others who might be learning. (Hopefully
more successfully than you.)

moo

"kontiki" > wrote in message
...
> whatever.
>
> Peter Duniho wrote:
>
>> "kontiki" > wrote in message
>> ...
>>
>>>In theory of course. In the case of the 172 with 40 degrees of flaps they
>>>contribute more drag than lift.
>>
>>
>> In practice too. The relative amounts of drag and lift are irrelevant to
>> the fact that using the flaps lowers the stall speed, and that doing so
>> does not make it any easier "to end up real slow in a slip".
>>
>> Your assertion that "With full flaps its easy to end up real slow in a
>> slip and approach a stall" is just plain nonsense, and certainly has
>> nothing to do with the *warning* (not prohibition) against slipping
>> while flaps are extended (even if there were something to your claim
>> about flaps making it easier to stall).
>>
>> Pete
>

[Happy Dog]

"Bob Moore" > wrote in

> "AnthonyQ" wrote
>
>> I was told many years ago that a full rudder slip in a C172
>> (especially the older models with 40deg flaps), it is possible to
>> induce a tail stall....not good close to the ground....
>
> From the book "Cessna, Wings for the World" by William Thompson,
> Manager-Flight Test and Aerodynamics for the Cessna Aircraft
> Company where he also served as an Engineering Test Pilot and
> other positions for a total of 28 years.

Thanks for that. I note, though, that it doesn't mention a tail stall
anywhere.

moo
>
> "With the advent of the large slotted flaps in the C-170, C-180, and C-
> 172 we encountered a nose down pitch in forward slips with the wing flaps
> deflected. In some cases it was severe enough to lift the pilot against
> his seat belt if he was slow in checking the motion. For this reason a
> caution note was placed in most of the owner's manuals under "Landings"
> reading "Slips should be avoided with flap settings greater than 30° due
> to a downward pitch encountered under certain combinations of airspeed,
> side-slip angle, and center of gravity loadings". Since wing-low drift
> correction in cross-wind landings is normally performed with a minimum
> flap setting (for better rudder control) this limitation did not apply to
> that maneuver. The cause of the pitching motion is the transition of a
> strong wing downwash over the tail in straight flight to a lessened
> downwash angle over part of the horizontal tail caused by the influence
> of a relative "upwash increment" from the upturned aileron in slipping
> flight. Although not stated in the owner's manuals, we privately
> encouraged flight instructors to explore these effects at high altitude,
> and to pass on the information to their students. This phenomenon was
> elusive and sometimes hard to duplicate, but it was thought that a pilot
> should be aware of its existence and know how to counter-act it if it
> occurs close to the ground.
> When the larger dorsal fin was adopted in the 1972 C-172L, this side-slip
> pitch phenomenon was eliminated, but the cautionary placard was retained.
> In the higher-powered C-172P and C-R172 the placard was applicable to a
> mild pitch "pumping" motion resulting from flap outboard-end vortex
> impingement on the horizontal tail at some combinations of side-slip
> angle, power, and airspeed."
>
> This is probably as close to the real story as we will get.
>
> Bob Moore
> ATP CFI
> PanAm (retired)

[Dave]

This the best explanation I have seen yet..

I have tried it, 1974 172 m, 40 deg., all the rudder we had,
.....

Pitched for 55 knts...no prob.

Reversed the slip..solid , no prob..

2 people on board, 2/3 tanks...

Beware, it comes down like a parachute!..Could come in handy
sometime.

Straight decent resumed instantly upon relaxing the slip
input.

YMMV.....

Dave



On Thu, 06 Jan 2005 22:11:07 GMT, Bob Moore >
wrote:

>"AnthonyQ" wrote
>
>> I was told many years ago that a full rudder slip in a C172
>> (especially the older models with 40deg flaps), it is possible to
>> induce a tail stall....not good close to the ground....
>
>From the book "Cessna, Wings for the World" by William Thompson,
>Manager-Flight Test and Aerodynamics for the Cessna Aircraft
>Company where he also served as an Engineering Test Pilot and
>other positions for a total of 28 years.
>
>"With the advent of the large slotted flaps in the C-170, C-180, and C-
>172 we encountered a nose down pitch in forward slips with the wing flaps
>deflected. In some cases it was severe enough to lift the pilot against
>his seat belt if he was slow in checking the motion. For this reason a
>caution note was placed in most of the owner's manuals under "Landings"
>reading "Slips should be avoided with flap settings greater than 30° due
>to a downward pitch encountered under certain combinations of airspeed,
>side-slip angle, and center of gravity loadings". Since wing-low drift
>correction in cross-wind landings is normally performed with a minimum
>flap setting (for better rudder control) this limitation did not apply to
>that maneuver. The cause of the pitching motion is the transition of a
>strong wing downwash over the tail in straight flight to a lessened
>downwash angle over part of the horizontal tail caused by the influence
>of a relative "upwash increment" from the upturned aileron in slipping
>flight. Although not stated in the owner's manuals, we privately
>encouraged flight instructors to explore these effects at high altitude,
>and to pass on the information to their students. This phenomenon was
>elusive and sometimes hard to duplicate, but it was thought that a pilot
>should be aware of its existence and know how to counter-act it if it
>occurs close to the ground.
>When the larger dorsal fin was adopted in the 1972 C-172L, this side-slip
>pitch phenomenon was eliminated, but the cautionary placard was retained.
>In the higher-powered C-172P and C-R172 the placard was applicable to a
>mild pitch "pumping" motion resulting from flap outboard-end vortex
>impingement on the horizontal tail at some combinations of side-slip
>angle, power, and airspeed."
>
>This is probably as close to the real story as we will get.
>
>Bob Moore
>ATP CFI
>PanAm (retired)

[Dave]

It is required student training in Canada.

Lotsa spins... :)

Dave

On Thu, 06 Jan 2005 21:05:17 GMT, kontiki >
wrote:

That training is not nromally a part of student
>pilot training.
>
Snip
>>
>> But any properly trained low time student can recover from a stall
>> without spinning.
>>
>> Stefan

[Mike Rhodes]

On Thu, 6 Jan 2005 13:34:48 -0800, "Peter Duniho"
> wrote:

>"kontiki" > wrote in message
...
>> In theory of course. In the case of the 172 with 40 degrees of flaps they
>> contribute more drag than lift.
>
>In practice too. The relative amounts of drag and lift are irrelevant to
>the fact that using the flaps lowers the stall speed, and that doing so does
>not make it any easier "to end up real slow in a slip".
>
>Your assertion that "With full flaps its easy to end up real slow in a slip
>and approach a stall" is just plain nonsense, and certainly has nothing to
>do with the *warning* (not prohibition) against slipping while flaps are
>extended (even if there were something to your claim about flaps making it
>easier to stall).
>
>Pete
>

Odd, but interesting thread. I haven't heard of tail stall before.
But if I've got the basics correct, don't flaps allow the aircraft to
fly at slow airspeeds with a lower angle of attack, including both
wing and tailplane? So flaps should reduce the likelihood of any
stall, provided enough power is applied to those draggy 40 deg
settings. The wing stalls at a specific angle of attack, and I don't
think the flaps change that characteristic; not that it has been
suggested anywhere.

I may be wrong, but isn't this one reason why airliners need flaps at
landing? So they don't bounce the tail on touchdown? Or more likely
so the pilot can see the landing area; aside from just reducing
required runway length.
--
Mike

[Slip'er]

Drat!! Well, some brain matter must have slipped out of my cranium
somewhere along the way. I'm sure that it doesn't help that I haven't been
current in 6 years...my god, how have I let that happen?

Thanks for the correction.

Slip'er

"Bob Moore" > wrote in message
. 121...
> "Slip'er" > wrote
>
> >> I heard references to "forward slip" to get rid of altitude on
> >> approach.
> >
> > Both prior posts pretty much nailed it. A forward slip can be made
> > either to the left or right. Basically, you intentionally use cross
> > controls (rudder & aeleron). I believe that a forward slip generally
> > refers to using a slip to keep the aircraft aligned with the runway
> > for landing in a crosswind. This could mean landing on one wheel to
> > maintain directional orientation. This is my preferred approach when
> > flying in a cross wind in a taildragger.
> >
> > A side slip is similar but in this scenario, the slip is can be more
> > aggressive. A side slip is used to shed altitude.
>
> I do believe that you have them reversed..........
>
> From http://www.airbum.com/articles/ArticleSlips.html
>
> The old fashioned forward slip is one of those maneuvers that on one hand
> would appear to be redundant to modern flap systems. At the same time,
> it's one of those basic maneuvers that if understood and practiced gives
> the pilot yet another tool enabling him to put the airplane exactly where
> he wants it on approach.
>
> Unless we're talking about the so-called side slip in which a slipping
> motion to the side is canceled out by the crosswind so the airplane
> tracks straight.
>
> Bob Moore
> ATP CFI
>

[Slip'er]

I could lose my call sign for this! Don't tell anybody. That was a nice
article Bob.

> slip'er... you have them reversed..
>

[Happy Dog]

"Mike Rhodes" >
> On Thu, 6 Jan 2005 13:34:48 -0800, "Peter Duniho"
> <
>>Your assertion that "With full flaps its easy to end up real slow in a
>>slip
>>and approach a stall" is just plain nonsense, and certainly has nothing to
>>do with the *warning* (not prohibition) against slipping while flaps are
>>extended (even if there were something to your claim about flaps making it
>>easier to stall).
>>
>>Pete
>>
>
> Odd, but interesting thread. I haven't heard of tail stall before.

Very uncommon and very serious. Weight and balance (forward C of G) and
icing can cause it. It's just a wing.

> But if I've got the basics correct, don't flaps allow the aircraft to
> fly at slow airspeeds with a lower angle of attack, including both
> wing and tailplane?

Wing.

> So flaps should reduce the likelihood of any
> stall, provided enough power is applied to those draggy 40 deg
> settings. The wing stalls at a specific angle of attack, and I don't
> think the flaps change that characteristic; not that it has been
> suggested anywhere.

Flaps change the shape of the wing and allow it to fly at a higher angle of
attack before stall. A higher angle of attack before stall allows a higher
coeiffcient of lift. Stall speed is reduced. Drag is increased. Forward
visibility is improved at slow airspeeds. Drag increases. Top speed is
reduced (white arc). Trim is affected noticibly. That's all the practical
stuff you need to know. But:

http://www.aerospaceweb.org/question/aerodynamics/q0008.shtml
http://www.aerospaceweb.org/question/aerodynamics/q0005.shtml
http://www.av8n.com/how/htm/vdamp.html#sec-effect-of-flaps

Actually, read all of this:

http://www.av8n.com/how/

>
> I may be wrong, but isn't this one reason why airliners need flaps at
> landing? So they don't bounce the tail on touchdown? Or more likely
> so the pilot can see the landing area; aside from just reducing
> required runway length.

No.

moo

[Dave Stadt]

"Slip'er" > wrote in message
news:s1oDd.43020$8e5.10796@fed1read07...
> I could lose my call sign for this! Don't tell anybody. That was a nice
> article Bob.

You are OK A slip is a slip is a slip. The airplane knows no difference.


>
> > slip'er... you have them reversed..

[Dave Stadt]

"Happy Dog" > wrote in message
...
> "kontiki" > wrote in message
>
> >> But any properly trained low time student can recover from a stall
> >> without spinning.
> >>
> >> Stefan
> >
> >I would not necessarily go so far as to say that. Working on my CFI
> > I had to undergo spin training... actually recovering from spins
> > multiple times. That training is not nromally a part of student
> > pilot training.
>
> Yeah. Drag that. It is in Canada. Requirement on CPL test.
> >
> > Remember that a spin requires a stall of one wing... the other
> > can be flying quite normally. Students are typically tought stalls
> > under coordinated conditions.
>
> Have you stalled in a slip? It's no harder to recover than any other
power
> off stall. Which wing drops?

In a lot of planes neither.

[houstondan]

only some of the 172s have 40deg. and it's like a parachute if you want
to lose some altitude quick. it was explained to me that, on that ac,
up to 20degrees you were getting lift and drag...beyond 20degrees, it's
all drag. i'll believe it.

dan

[Ramapriya]

Peter Duniho wrote:

> I guess that's what we get for answering Ramapriya's questions.
We're
> turning into rec.aviation.student.

Yes mate, I know what you want to say.
And I didn't even start this thread :(

[Ramapriya]

Bob Moore wrote:

> I do believe that you have them reversed..........
>
> From http://www.airbum.com/articles/ArticleSlips.html

Nice article. Nice runway shots, though in the last pic I'd have
captioned 'flare' instead :)

Ramapriya

[Happy Dog]

"Dave Stadt" > wrote in
>> Have you stalled in a slip? It's no harder to recover than any other
> power
>> off stall. Which wing drops?
>
> In a lot of planes neither.

Idiot.

moo

[Cub Driver]

On Thu, 6 Jan 2005 09:40:06 -0500, "Gary G"
> wrote:

>Can someone give me the 2 sentence (or how ever many is adequate) to
>what a forward slip procedure is?

Hold left rudder and right aileron, or vice versa. Somehow I always
find it easier to slip to the left.

It's what Cub drivers have instead of flaps.

[Cub Driver]

>> off stall. Which wing drops?
>
>In a lot of planes neither.

I did my first couple of flights in a Colt, which the airport then
sold and put me ijn a 172. I hated it when the 172 wing dropped!

Cubs don't drop a wing, either.

[Dave Stadt]

"Happy Dog" > wrote in message
...
> "Dave Stadt" > wrote in
> >> Have you stalled in a slip? It's no harder to recover than any other
> > power
> >> off stall. Which wing drops?
> >
> > In a lot of planes neither.
>
> Idiot.
>
> moo
>

Coming from you that is a compliment. Thanks!

[Thomas Borchert]

Gary,

as other have said, the distinction between side and forward is more
confusing than helpful, IMHO. Same thing, only difference is movement
relativ to the ground.

--
Thomas Borchert (EDDH)

[Mike Rhodes]

On Thu, 6 Jan 2005 23:26:05 -0500, "Happy Dog" >
wrote:

>"Mike Rhodes" >
>> On Thu, 6 Jan 2005 13:34:48 -0800, "Peter Duniho"
>> <
>>>Your assertion that "With full flaps its easy to end up real slow in a
>>>slip
>>>and approach a stall" is just plain nonsense, and certainly has nothing to
>>>do with the *warning* (not prohibition) against slipping while flaps are
>>>extended (even if there were something to your claim about flaps making it
>>>easier to stall).
>>>
>>>Pete
>>>
>>
>> Odd, but interesting thread. I haven't heard of tail stall before.
>
>Very uncommon and very serious. Weight and balance (forward C of G) and
>icing can cause it. It's just a wing.

I meant in the context of this thread. I'm aware of icing, and that
the tailplane is an airfoil.

>
>> But if I've got the basics correct, don't flaps allow the aircraft to
>> fly at slow airspeeds with a lower angle of attack, including both
>> wing and tailplane?
>
>Wing.

Meaningless retort. You said "it's just a wing." So you've conquered
the wing? And are looking for other nothings to walk on? Do you have
something against the wing, and other nothings?

>
>> So flaps should reduce the likelihood of any
>> stall, provided enough power is applied to those draggy 40 deg
>> settings. The wing stalls at a specific angle of attack, and I don't
>> think the flaps change that characteristic; not that it has been
>> suggested anywhere.
>
>Flaps change the shape of the wing and allow it to fly at a higher angle of
>attack before stall.

No they don't. Are you thinking of slats? This was the point I was
trying to get at in my post. Flaps actually increase the stalling
nature of the wing (though from the safer wing root area) when
referenced to AOA, but not airspeed.

>A higher angle of attack before stall allows a higher
>coeiffcient of lift.

I have my fluids book in front of me. It has a graph of coefficient
of lift versus angle of attack, and various plots of wings with and
without flaps. In general, the more substantial the flap then the
greater the coefficient of lift (and that coefficient can more than
double; from ~1.5 no-flaps to 3.5 double-slotted). Also, the more
substantial the flap then the _lower_ angle of attack at which the
_wing_ will stall, though only a relatively small (10-25%?) of the
original stall angle.

> Stall speed is reduced. Drag is increased. Forward
>visibility is improved at slow airspeeds.

Ha! You just proved my point, which you still deny!

> Drag increases. Top speed is
>reduced (white arc). Trim is affected noticibly. That's all the practical
>stuff you need to know. But:

But are you sane?

>
>http://www.aerospaceweb.org/question/aerodynamics/q0008.shtml
>http://www.aerospaceweb.org/question/aerodynamics/q0005.shtml
>http://www.av8n.com/how/htm/vdamp.html#sec-effect-of-flaps

>
>Actually, read all of this:
>
>http://www.av8n.com/how/

You read it.

>
>>
>> I may be wrong, but isn't this one reason why airliners need flaps at
>> landing? So they don't bounce the tail on touchdown? Or more likely
>> so the pilot can see the landing area; aside from just reducing
>> required runway length.
>
>No.

(see my Ha! above)

>
>moo

Are you a cow? with a bullish facade?

[[email protected]]

Dave wrote:
> This the best explanation I have seen yet..
>
> I have tried it, 1974 172 m, 40 deg., all the rudder we had,
> ....

You have to work a little harder than that. The phenomenon you were
looking for depends a lot on the CG. Many years ago when I used to fly
Cessnas of various vintage, I discovered the phenomenon after much
trial and error. It was most likely to occur near the rear CG limit in
a (early '70s)172 near gross. Frankly, I don't know what all the fuss
was about. It produced a fairly mild pitch oscilation that I couldn't
distiguish from the usual convective turbulence we get here in the
desert. If it wasn't for the instructor in the back seat pointing it
out, I would have missed it.

John Galban=====>N4BQ (PA28-180, slips with flaps and got the T-shirt!)

[Happy Dog]

"Mike Rhodes" >
>>>
>>> Odd, but interesting thread. I haven't heard of tail stall before.
>>
>>Very uncommon and very serious. Weight and balance (forward C of G) and
>>icing can cause it. It's just a wing.
>
> I meant in the context of this thread. I'm aware of icing, and that
> the tailplane is an airfoil.

You said "I haven't heard of tail stall before" without any conditions.
>
>>
>>> But if I've got the basics correct, don't flaps allow the aircraft to
>>> fly at slow airspeeds with a lower angle of attack, including both
>>> wing and tailplane?
>>
>>Wing.
>
> Meaningless retort. You said "it's just a wing." So you've conquered
> the wing? And are looking for other nothings to walk on? Do you have
> something against the wing, and other nothings?

I said "wing" because your statement is incorrect WRT the tail. On T Tail
airplanes, flaps have no effect on tailplane performance.
>
>>
>>> So flaps should reduce the likelihood of any
>>> stall, provided enough power is applied to those draggy 40 deg
>>> settings. The wing stalls at a specific angle of attack, and I don't
>>> think the flaps change that characteristic; not that it has been
>>> suggested anywhere.
>>
>>Flaps change the shape of the wing and allow it to fly at a higher angle
>>of
>>attack before stall.
>
> No they don't. Are you thinking of slats?

Yes. My mistake. Lower angle of attack.

> I have my fluids book in front of me. It has a graph of coefficient
> of lift versus angle of attack, and various plots of wings with and
> without flaps. In general, the more substantial the flap then the
> greater the coefficient of lift (and that coefficient can more than
> double; from ~1.5 no-flaps to 3.5 double-slotted). Also, the more
> substantial the flap then the _lower_ angle of attack at which the
> _wing_ will stall, though only a relatively small (10-25%?) of the
> original stall angle.
>
>> Stall speed is reduced. Drag is increased. Forward
>>visibility is improved at slow airspeeds.
>
> Ha! You just proved my point, which you still deny!

If your point was that "The wing stalls at a specific angle of attack, and I
don't think the flaps change that characteristic", then, yes, I still deny
it.
>
>> Drag increases. Top speed is
>>reduced (white arc). Trim is affected noticibly. That's all the
>>practical
>>stuff you need to know. But:
>
> But are you sane?

You disagree with any of the above?

m

[Trent Moorehead]

> wrote in message
ups.com...
It produced a fairly mild pitch oscilation that I couldn't
> distiguish from the usual convective turbulence we get here in the
> desert. If it wasn't for the instructor in the back seat pointing it
> out, I would have missed it.

Once, on approach, I was slipping heavily with full flaps and it felt like
the elevator was blanked out. When I slip in a 172, I apply forward pressure
to the yoke and this time, the yoke lost all resistance to my pushing. The
thing kind of went "limp" and went all the way to the console. I relaxed the
rudder and the yoke shot back into my hand. Mind you, this happened in the
span of a second, but it really got my attention!

I think that this could have been caused by turbulent winds that day
perhaps, but I can't be sure. Either way, I'm a little more careful now.

-Trent
PP-ASEL