Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Stall in a side slip
Goto page Previous 1, 2

Matronics Email Lists Forum Index -> Kitfox-List

View previous topic :: View next topic

Author Message

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Jul 29, 2006 5:45 am Post subject: Stall in a side slip

Spins shouldn't be a problem especially if you have altitude on your side.

Just remember to correct with rudder NOT AILERON.  At least you have

experienced a spin...  A lot of trainers today don't even let a student

experience a spin because it isn't in the flight test.  As if the guys who

wrote the flight test considered the repercussions of removing the spin form

the test.



My first spin was totally thrilling!!  When the screen filled with ground

spinning at a fibulas rate of knots... Wow!  I wouldn't have been able to

correct it on the first occurrence. I would have been to busy with bodily

fluids to do much of anything.  



Now because of the spin training that I had if I did an accidental spin

today I would just be upset with myself at letting it happen.  As I said

altitude is your friend if you have enough altitude on approach then you can

sort things out for a nice landing.... But.... You always have to be ready

for ground squalls and wind shears etc.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Jul 29, 2006 5:53 am Post subject: Stall in a side slip

I haven't seen an engine yet that can't quit unexpectedly.  Four stroke, two

stroke or turbine.   Take a queue from the Boy Scouts...."Be Prepared"!!



I read a good one some time back about a fellow who was told to take a 360

while a B52 was doing a precautionary landing with an engine out.  



His answer to the tower was he would do the 360 because there is nothing

quite like the dreaded seven engine landing /;^}



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Sat Jul 29, 2006 12:52 pm Post subject: Stall in a side slip

On Jul 29, 2006, at 3:15 PM, Colin Durey wrote:

 	  Quote: 	
		   Most gliders have "dive brakes" or "speed brakes" (spoilers)


	


Indeed, Colin. But since I don't have speed brakes on my Kitfox, I use 

sideslipping.

incidentally when my son took his Utralight license, last year on my  

Kitfox, after he flew his first solo, I asked him how it was, having 

still in mind my own terrific experience. "Ok," he answered.

- "What? Just ok?"

- "Yes, it was much more exiting when I flew solo in a glider (as you 

say yourself, Colin) 15 years ago, knowing I had only one chance to 

land the bird."



My son had about 50 hours on the club's Blanik and I was a few time up 

with him, as my  only glider experience.

When I started with the Kitfox, three years ago, I became interested by 

a fact: In Norway, your normal insurance doesn't cover you for sports 

like diving, parachuting, mountains climbing and ... ultralight flying. 

But it does for glider flying, which is considered as safe as ... 

sitting in your garden or shopping. So, it became clear to me that if I 

wanted to fly safe, I had to fly ... like a glider pilot, always be 

ready to be in gliding distance to a safe landing.



 	  Quote: 	
		   By all means, after some qualified training, continue to do engine

 failure, stall, spin, and side-slip practice,  but do it up high where

 you've got time to recover, and plan every approach early and well.


	


Well, stalls and spins are not necessary for safe flying, Colin. But, 

IMHO, to be able to do precision landing with no engine, is safety 

training. If I, or my son, ever loose engine power, I want us to do the 

right thing without hesitation. As opposed to sailing, in aviation any 

fraction of a second can make the difference between life and death. 

But as for sailing, I know I need to have a plan. And when I fly, I try 

to note any place I could land on because I think that, if the engine 

starts to go wrong, it is better to land safely on something that is 

right under me, than to try to make it to an airfield that may be 

beyond a forest, a mountain, a stretch of water. The action then is to 

eyeball that emergency field, and fly the plane for a safe landing, as 

trained for, almost as a reflex. Wouldn't you agree?



Cheers,

Michel

_________________
Kitfox 3 - Jabiru 2200

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sat Jul 29, 2006 12:58 pm Post subject: Stall in a side slip

At 12:51 AM 7/29/2006, you wrote:

 	  Quote: 	
		  But, has any of you stalled voluntary, at high altitude, in a forward

slip? I could try myself but I'd rather ask the list first because ...

I don't want to end in a spin!


	


It doesn't matter what you call it, stalling cross controlled results in 

the trailing wing stalled, and the leading wing not. (It's actually worse 

than what we do for a normal spin entry, because the trailing wing aileron 

is down, which increases that wing's angle of attack.) This can result in a 

variety of things, depending on subsequent control input, but typically 

results in a spin. (Steady state control input.) Yes, if you get too slow 

during your slip to final you will spin, with predictable results.



There is no reason, however, that you should get slow during a slip. 

Remember that drag varies with the square of the velocity. If you want to 

bleed LOTS of energy, get draggy and go FAST. (Meaning: point it down with 

the power off.) Though I'm sure it's possible to slip all the way to the 

ground, with a dramatic flare at the end, you will, by definition, have to 

carry more speed into that flare than if you stabilized at just above stall 

on your approach. (Slipping stall speed is higher.) The higher speed will 

make your subsequent float and ground roll longer. Ideally the slip is only 

used to lower the aircraft to the intended glide slope. I have, like you, 

done weak slips all the way to the ground, thereby increasing the angle of 

the glide slope, but the preferred method for increasing the angle of glide 

slope is to go slower. I've done it by slip when there were people behind 

me who wouldn't appreciate my 50 knot approach speed. Usually I slip hard 

until I get to the proper glide slope, then straighten and continue a 

conventional stabilized approach.



The big question with short field operations is what gust factor you use. 

It's possible to land a Cessna 152 at about 45 knots, however, if the wind 

velocity decreases by five knots as you enter your flare, guess what? You 

just stalled. It makes for one hell of a short roll-out, but you have to 

leave the field by truck! Our Kitfox's are the same. I suppose you could 

make an approach at 45 MIAS, and drop like the proverbial rock, but it's 

just too easy to have a 5 knot wind variation on the deck ruin your whole 

day. I suppose it depends on how desperate you are. I'm guessing it's 

better to land at 55 MIAS and hit the trees at 25 than stall on approach at 45.



Do yourself a favor Michel. Go find an aerobatic aircraft and instructor. 

I'm not implying you need the education! Do it because it's one hell of a 

lot of fun, teaches you how to really control your aircraft, and answers 

all these questions. In a Decathlon you can do practically anything, get 

wildly out of shape, then recover and fly away casually. It's a great 

feeling. Budget about 10 hours.

Guy Buchanan

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Sat Jul 29, 2006 1:45 pm Post subject: Stall in a side slip

On Jul 29, 2006, at 10:52 PM, Guy Buchanan wrote:

 	  Quote: 	
		   It's actually worse than what we do for a normal spin entry, because 

 the trailing wing aileron is down, which increases that wing's angle 

 of attack.


	


Hang on because I am not following, Guy.

When I do a side slip on final (with engine on or not) I always do it 

with left stick and right rudder so that, from the left-hand seat, I 

get a better view of the runway. My right wing is high, my left is low. 

Which is the trailing one? The right wing?

I think I read (as I write in my previous email) that a stall and slip 

was less dangerous than a stall and skid. Do you mean it is the 

opposite?



Of course, when I side slip, it is well above stall speed, adjusting 

for turbulence. It usually happens like this: I am on final, feel how I 

will land if I keep the attitude and speed, then I may feel I need to 

sink faster to land on the mark. If I put the nose down, I'll increase 

speed and will float far down the runway, so I put the nose down but 

reduce the speed increase by side slipping. I would always get the ball 

in the center before I need to lift the nose again. But I'd like to 

know how dangerous it is.



 	  Quote: 	
		   Do yourself a favor Michel. Go find an aerobatic aircraft and 

 instructor.


	


I intent to, Guy. I even know the pilot and the Bellanca plane that can 

do that. But ... I am a husband, a father, a grand-father, an employee 

and ... time, you know! Plus that the pilot is mostly at a nearby 

airfield and only visits us occasionally.



Cheers,

Michel



do not archive

_________________
Kitfox 3 - Jabiru 2200

mike
Guest

Posted: Sat Jul 29, 2006 4:40 pm Post subject: Re: Stall in a side slip

When I do a forward slip, I reduce to the proper airspeed, generally 60 then I'll slip twards the cross wind if there is one, if not, always a right rudder slip.  Now, I have slipped all the way down to 5 ft off the runway, in fact, when I did my check ride a few years ago, the examiner told me to demonstrate a slip to land, I slipped and cut out at 20ft from the runway, he said, I told you to slip to landing, so we did it again, this time I waited until about 5 ft. off the ground, recovered and flaired to land at the same time, his response, good one. I think it's very important to slip into the wind, think about it, we do the same cross control for cross wind correction, if you always slip with left wing down and you have the cross coming from the right, I feel this can bring desaster.

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sun Jul 30, 2006 7:17 am Post subject: Stall in a side slip

At 02:43 PM 7/29/2006, you wrote:

 	  Quote: 	
		  When I do a side slip on final (with engine on or not) I always do it

with left stick and right rudder so that, from the left-hand seat, I

get a better view of the runway. My right wing is high, my left is low.

Which is the trailing one? The right wing?


	


Yes.



 	  Quote: 	
		  I think I read (as I write in my previous email) that a stall and slip

was less dangerous than a stall and skid. Do you mean it is the

opposite?


	


The reason a skid is worse IN A TURN is because in a stabilized turn the 

inside wing is slower than the outside wing. Thus the inside wing ALWAYS 

has a higher angle of attack than the outside. Now it gets a little 

complex. When you skid or slip an aircraft with dihedral, the leading 

wing's angle of attack increases, and the following wing's angle of attack 

decreases, all along the length of the dihedral. (This is why you can turn 

with rudder only.) In a skid, with rudder into the turn, the outside wing's 

angle of attack increases. To prevent roll to the inside you apply outside, 

(cross-controlled,) aileron. In a typical aircraft with a short, attached, 

aileron out near the wing tip, this means the angle of attack over the 

inside aileron is higher than that just inboard of the aileron and MUCH 

higher than that of the opposite wing. Therefore the flow over the inside 

aileron stalls first, resulting in a terrific rolling moment to the inside. 

If the skid is extreme enough to actually blanket some of the inside wing 

then the cross-control must be increased to offset the reduction in 

effective area. The situation is reversed in a slip. With outside rudder 

you lift the outside wing with aileron, increasing the local angle of 

attack, but the outside wing has a lower angle of attack to begin with 

because it's going faster. Therefore the slip can be considered "safer" 

than the skid. (Note, however, you CAN spin out of a slipped turn, it just 

takes a little more work. You flip over the top rather than dropping to the 

inside giving you a little more time, as I think Dave already mentioned.)



With our flaperons I'm not sure we run the risks that normal ailerons do, 

since our flaperons are really fully flying "wings". I don't know whether 

we roll because we change the angle of attack of the wing, or if we roll 

because our "little wings" push the "big wings" around. If the latter, we 

may be much less sensitive to slip / skid spins. (Unless the flaperon stalls.)



The other way a slip or skid can ruin your day is more dynamic. If you 

begin a sharp turn with your wings very close to the critical angle of 

attack and then kick in an abrupt dose of inside rudder to tighten the turn 

the inside wing slows dramatically, increasing its angle of attack. As it 

begins to drop due to the resulting decrease in lift, (remember lift is 

proportional to the velocity squared,) the angle of attack increases still 

more resulting in a stall of that wing. (If it hasn't stalled already.) You 

snap into a spin even before you've had time to react with any 

cross-control aileron. (Of course, any aileron you might apply merely 

exacerbates the problem.) I think gliders are particularly prone to this 

type of skid-spin because of their long spans.



Clear as mud?

Guy Buchanan

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

morid(at)northland.lib.mi
Guest

Posted: Sun Jul 30, 2006 11:39 am Post subject: Stall in a side slip

Great explanation Guy.  Thanks!

Deke

do not archive



---

MichaelGibbs(at)cox.net
Guest

Posted: Sun Jul 30, 2006 12:55 pm Post subject: Stall in a side slip

Michel sez:



 	  Quote: 	
		  I think I read (as I write in my previous email) that a stall and 

slip was less dangerous than a stall and skid. Do you mean it is the 

opposite?


	


Michel, my friend, do not kid yourself.  Any time the rudder and 

ailerons are badly uncoordinated and the aircraft stalls you are 

setting yourself up for a spin.  There is no such thing as a "less 

dangerous" spin or a "less dangerous" way to impact the ground with 

the aircraft essentially out of control.  When the airplane stalls, 

that powerful Kitfox rudder will be doing it's job out there and the 

plane will roll to the side the rudder is on.



The weekend before my accident I was up practicing stalls and spins. 

My Model IV was a very docile spinner--it would usually just fly out 

of the spin in less than one turn unless I aggressively held the 

stick full back and the rudder full into the spin.  Even then I could 

not get a full turn to the left under any conditions.



Spins are not something to fear, they are something to be well 

understood and, in my opinion, practiced and perfected.  I believe 

that had I not been sharp on stall/spin recovery at the time of my 

accident, things would have been much worse.  By the time the 

airplane hit the ground, we were recovered from the stall and 

climbing out again (too bad the terrain was climbing even faster!).



 	  Quote: 	
		  I never use flaps on landing! It is, IMHO useless. I only use flaps 

to get fast out of a long, wet grass short field and that's all.


	


I don't know how the Model III compares with the Model IV, but my IV 

was a wonderful performer with the flaps down.  A half-flap takeoff 

gave me the shortest ground rolls and the steepest climb-outs for 

those short field situations, while full flaps on landing provided an 

extra measure of drag and very low touch-down speeds.  With full 

flaps and a little effort, I could touch down before the numbers and 

turn off into the run-up area on the local field's short runway!



Of course, my 'fox had a nose wheel and the flaperons were rigged for 

22 degrees of full deflection.  Your mileage will vary, of course.



 	  Quote: 	
		  About spins, I have done two, with my instructor, enough for me to 

understand that it is forbidden and that I will probably never be 

able to recover from one.


	


I'm sure that's not true, Michel.  Others may disagree but I find 

spin recovery easier than planting a perfect 3 point landing in a 

tail dragger.  Many light airplanes, such as the Cessna 152, will 

simply fly out of a spin if you let go of the controls (this leaves 

you in a descending spiral that will still require some pilot action 

to return to straight and level flight).  My Model IV was like 

that--let go of the controls and she would just start flying again.



As for slips, I've seen a lot of interesting theories advanced on the 

list this last week.  Not that the difference matters much, but a 

side slip is what you do to maintain your ground track when a wind is 

trying to push you left or right of the runway.  A forward slip is 

what you do when you are high on final approach and need to get down 

faster.  You aren't slipping to one side of your ground track, you 

are slipping forward along it.  What would you call a day when both 

happen?  I have no idea.



Just my two cents worth.



Mike G.

N728KF

janderson412(at)hotmail.c
Guest

Posted: Sun Jul 30, 2006 1:58 pm Post subject: Stall in a side slip

Out of interest Mike, would you be will to share the details of your accident, for learning purposes. John A.

 

 [quote]   

From:  Michael Gibbs <MichaelGibbs(at)cox.net>

Reply-To:  kitfox-list(at)matronics.com

To:  kitfox-list(at)matronics.com

Subject:  Re: Stall in a side slip

Date:  Sun, 30 Jul 2006 13:52:48 -0700

--> Kitfox-List message posted by: Michael Gibbs <MichaelGibbs(at)cox.net>



Michel sez:



 	  Quote: 	
		  I think I read (as I write in my previous email) that a stall and 

slip was less dangerous than a stall and skid. Do you mean it is the 

opposite?


	


Michel, my friend, do not kid yourself.  Any time the rudder and ailerons are badly uncoordinated and the aircraft stalls you are setting yourself up for a spin.  There is no such thing as a "less dangerous" spin or a "less dangerous" way to impact the ground with the aircraft  essentially out of control.  When the airplane stalls, that powerful Kitfox rudder will be doing it's job out there and the plane will roll to the side the rudder is on.



The weekend before my accident I was up practicing stalls and spins. My Model IV was a very docile spinner--it would usually just fly out of the spin in less than one turn unless I aggressively held the stick full back and the rudder full into the spin.  Even then I could not get a full turn to the left under any conditions.



Spins are not something to fear, they are something to be well understood and, in my opinion, practiced and perfected.  I believe that had I not been sharp on stall/spin recovery at the time of my accident, things would have been much worse.  By the time the airplane hit the ground, we were recovered from the stall and climbing out again (too bad  the terrain was climbing even faster!).



 	  Quote: 	
		  I never use flaps on landing! It is, IMHO useless. I only use flaps 

to get fast out of a long, wet grass short field and that's all.


	


I don't know how the Model III compares with the Model IV, but my IV was a wonderful performer with the flaps down.  A half-flap takeoff gave me the shortest ground rolls and the steepest climb-outs for those short field situations, while full flaps on landing provided an extra measure of drag and very low touch-down speeds.  With full flaps and a little effort, I could touch down before the numbers and turn off into the run-up area on the local field's short runway!



Of course, my 'fox had a nose wheel and the flaperons were rigged for 22 degrees of full deflection.  Your mileage will vary, of course.



 	  Quote: 	
		  About spins, I have done two, with my  instructor, enough for me to 

understand that it is forbidden and that I will probably never be 

able to recover from one.


	


I'm sure that's not true, Michel.  Others may disagree but I find spin recovery easier than planting a perfect 3 point landing in a tail dragger.  Many light airplanes, such as the Cessna 152, will simply fly out of a spin if you let go of the controls (this leaves you in a descending spiral that will still require some pilot action to return to straight and level flight).  My Model IV was like that--let go of the controls and she would just start flying again.



As for slips, I've seen a lot of interesting theories advanced on the list this last week.  Not that the difference matters much, but a side slip is what you do to maintain your ground track when a wind is trying to push you left or right of

colind

Joined: 10 Jan 2006
Posts: 32
Location: Sydney, Australia

Posted: Sun Jul 30, 2006 6:14 pm Post subject: Stall in a side slip

Micahel,

I did most of my early gliding training in a Blanik, over South-East

Queensland (Australia). Its a great aircraft to learn in as it is very

forgiving to novice pilots. All the same, 80 - 90kts cross-country without

an engine is not bad, eh? I still remember the puzzled radio call from a

152 pilot after we passed him at 9000ft one day. One memorable glider we

flew(?) was the Kookaburra. It was wood and fabric construction and it had

an open cockpit... you really knew you were flying. Unfortunately, it had

a glide angle only slightly better than a streamlined brick, so flights

tended to be fairly short. We could get 1200-1500 ft off the end of the

wire in it, but the nearest regular source of lift was about 1 mile from

the end of the strip so, on marginal days, you had to be good to get there

with enough height so that if you couldn't "get away", you could get back

to the strip with a comfortable margin.

I have only one problem with what you said in your reply, namely:

  "Well, stalls and spins are not necessary for safe flying, Colin. But,

 IMHO, to be able to do precision landing with no engine, is safety

 training."

The second part - yes...  the first part, absolutely NO!

A key principle of pilot training, in this part of the world at least, is

that pilots need to be proficient in all aspects of flight control, and

competent in recognising and responding to anything which might cause a

danger to the continued safe operation of the aircraft. Your second remark

aligns with that concept. Up until 1985, Abinitio pilot training here

included incipient stalls, full stalls, incipient spins and full spins.

After that time, for a few years, full stalls and spins were not part of

training. As a result, there was a whole bracket of pilots who had not

experienced a fully developed stall or spin, and thus had no experience in

recovering from them. I recall flying with a young lady who had recently

obtained her PPL. We flew to the training area near Brisbane and I asked

her to do a stall. When she got to the point of the pre-stall buffeting,

she lowered the nose and applied power. After a sarcastic remark from me,

I asked her to do another stall... same procedure. I then proceeded to put

the aircraft into a full stall and told her to do the recovery. She

couldn't. Despite her ashen face, we went on to spins. Same thing with the

spin. Interestingly, on approach back into Archerfield, she came in high

(probably a little shaken from what had happened), and proceeded to do a

perfectly good side-slip to lose height.

After about 5 or 6 years, full stalls and spins were re-included in pilot

training. While I don't have any official data to refer to, the anecdotal

evidence is that the number of un-intended stall/spin incidents increased

significantly during that period, and persisted for a while thereafter.

The problem was that, these pilots never really understood what a fully

developed stall or spin was like, and did not go through the actual entry

sequence and process of recover and thus have true experience. While an

explanation of the process, "complete with pictures", was provided, the

truth really is that "Showing is better than telling".

Close to ground manouvers, ie: landing and take-off, are when un-intended

stall/spin incidents are most likely to occur, and usually have the most

dramatic (tragic) outcomes. Slipping (forward, inward, outward, or

whichever way) on approach is a flight condition which puts you close to

the edge of the safe flight envelope. Practical experience in how the

aircraft feels, responds, and is tending to act, is vital for a pilot to

be able to manage the continued safe operation of the aircraft.

Especially, to be able to predict, and respond quickly and correctly to

what happens, or, is about to happen.

Practicing, on a regular basis, engine failure (on t/o and landing), steep

decents, stalls, spins, and side/forward slips, etc, etc, are all, I

believe, vital for for every pilot. After all, "Practice makes perfect"

(well, nearly). Just do the practice in a way (ie: in a location and at an

altitude) that is least likely to cause a major problem if things don't go

the way you planned. Practice engine outs and side-slips in the circuit

every once in a while. However, don't make it a habit to use side-slips as

a standard approach procedure, nor make high approaches standard, which

will set you up to do side-slips.

I hope I haven't rambled on too much for you, its just that this is a

subject particularly close to me. I really envy the great scenery you fly

over Michael, and have enjoyed looking at the photos you have posted. I

hope to have my 'Fox in the air in the next couple of months, so will be

able to send you some of the area around here. I would love to come and

visit one day.

Regards

Colin Durey

Sydney - Australia

+61-418-677073 (M)

+61-2-945466162 (F)

 	  Quote: 	

 On Jul 29, 2006, at 3:15 PM, Colin Durey wrote:

> Most gliders have "dive brakes" or "speed brakes" (spoilers)

 Indeed, Colin. But since I don't have speed brakes on my Kitfox, I use

 sideslipping.

 incidentally when my son took his Utralight license, last year on my

 Kitfox, after he flew his first solo, I asked him how it was, having

 still in mind my own terrific experience. "Ok," he answered.

 - "What? Just ok?"

 - "Yes, it was much more exiting when I flew solo in a glider (as you

 say yourself, Colin) 15 years ago, knowing I had only one chance to

 land the bird."

 My son had about 50 hours on the club's Blanik and I was a few time up

 with him, as my  only glider experience.

 When I started with the Kitfox, three years ago, I became interested by

 a fact: In Norway, your normal insurance doesn't cover you for sports

 like diving, parachuting, mountains climbing and ... ultralight flying.

 But it does for glider flying, which is considered as safe as ...

 sitting in your garden or shopping. So, it became clear to me that if I

 wanted to fly safe, I had to fly ... like a glider pilot, always be

 ready to be in gliding distance to a safe landing.

> By all means, after some qualified training, continue to do engine

> failure, stall, spin, and side-slip practice,  but do it up high where

> you've got time to recover, and plan every approach early and well.

 Well, stalls and spins are not necessary for safe flying, Colin. But,

 IMHO, to be able to do precision landing with no engine, is safety

 training. If I, or my son, ever loose engine power, I want us to do the

 right thing without hesitation. As opposed to sailing, in aviation any

 fraction of a second can make the difference between life and death.

 But as for sailing, I know I need to have a plan. And when I fly, I try

 to note any place I could land on because I think that, if the engine

 starts to go wrong, it is better to land safely on something that is

 right under me, than to try to make it to an airfield that may be

 beyond a forest, a mountain, a stretch of water. The action then is to

 eyeball that emergency field, and fly the plane for a safe landing, as

 trained for, almost as a reflex. Wouldn't you agree?

 Cheers,

 Michel

_________________
Colin Durey
Sydney
+61-418-677073

Graeme Toft

Joined: 09 Jan 2006
Posts: 123

Posted: Sun Jul 30, 2006 7:03 pm Post subject: Stall in a side slip

There good points you make Colin and unfortunately for today's pilots coming 

through the RAAust, those skills of recovery from unusual attitudes will 

most likely never be learnt. Its unfortunate that other than stalls, the 

basic spins, stall turns, wing overs etc are illegal in our aircraft. We all 

know that structurally most will take them in their stride but for a person 

to hold a pilots license and yet never experience those basic manuovourses 

is a real shame. As you rightly pointed out, how many of the pilots who lost 

there lives in the mid 80's would be alive today if these basics skills had 

be taught to them. A sedate stall can very quickly turn into something we 

generally try to avoid and it is inexcusable for people to be unprepared for 

such an event.



Regards

Graeme ---

msm_9949(at)yahoo.com
Guest

Posted: Mon Jul 31, 2006 8:50 am Post subject: Stall in a side slip

So clear I've developed a headache. 

   

  do not archive



Guy Buchanan <bnn(at)nethere.com> wrote:

  [quote]--> Kitfox-List message posted by: Guy Buchanan 



At 02:43 PM 7/29/2006, you wrote:

 	  Quote: 	
		  When I do a side slip on final (with engine on or not) I always do it

with left stick and right rudder so that, from the left-hand seat, I

get a better view of the runway. My right wing is high, my left is low.

Which is the trailing one? The right wing?


	


Yes.



 	  Quote: 	
		  I think I read (as I write in my previous email) that a stall and slip

was less dangerous than a stall and skid. Do you mean it is the

opposite?


	


The reason a skid is worse IN A TURN is because in a stabilized turn the 

inside wing is slower than the outside wing. Thus the inside  wing ALWAYS 

has a higher angle of attack than the outside. Now it gets a little 

complex. When you skid or slip an aircraft with dihedral, the leading 

wing's angle of attack increases, and the following wing's angle of attack 

decreases, all along the length of the dihedral. (This is why you can turn 

with rudder only.) In a skid, with rudder into the turn, the outside wing's 

angle of attack increases. To prevent roll to the inside you apply outside, 

(cross-controlled,) aileron. In a typical aircraft with a short, attached, 

aileron out near the wing tip, this means the angle of attack over the 

inside aileron is higher than that just inboard of the aileron and MUCH 

higher than that of the opposite wing. Therefore the flow over the inside 

aileron stalls first, resulting in a terrific rolling moment to the inside. 

If the skid is extreme enough to actually blanket some of the inside wing 

then the cross-control must be increased  to offset the reduction in 

effective area. The situation is reversed in a slip. With outside rudder 

you lift the outside wing with aileron, increasing the local angle of 

attack, but the outside wing has a lower angle of attack to begin with 

because it's going faster. Therefore the slip can be considered "safer" 

than the skid. (Note, however, you CAN spin out of a slipped turn, it just 

takes a little more work. You flip over the top rather than dropping to the 

inside giving you a little more time, as I think Dave already mentioned.)



With our flaperons I'm not sure we run the risks that normal ailerons do, 

since our flaperons are really fully flying "wings". I don't know whether 

we roll because we change the angle of attack of the wing, or if we roll 

because our "little wings" push the "big wings" around. If the latter, we 

may be much less sensitive to slip / skid spins. (Unless the flaperon stalls.)



The other way a  slip or skid can ruin your day is more dynamic. If you 

begin a sharp turn with your wings very close to the critical angle of 

attack and then kick in an abrupt dose of inside rudder to tighten the turn 

the inside wing slows dramatically, increasing its angle of attack. As it 

begins to drop due to the resulting decrease in lift, (remember lift is 

proportional to the velocity squared,) the angle of attack increases still 

more resulting in a stall of that wing. (If it hasn't stalled already.) You 

snap into a spin even before you've had time to react with any 

cross-control aileron. (Of course, any aileron you might apply merely 

exacerbates the problem.) I think gliders are particularly prone to this 

type of skid-spin because of their long spans.



Clear as mud?

Guy Buchanan

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

Display posts from previous:

	Matronics Email Lists Forum Index -> Kitfox-List	All times are GMT - 8 Hours Goto page Previous 1, 2
Page 2 of 2

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum