Sideslip
Jonkster, I have had a little difficulty visualising your spinning scenerio. To me yaw is rotation around the vertical axis, this may be as a result of rudder application, wings level, a normal turn, or a combination.
For your spin resistant aircraft I would add that some certification requirements specify stalling at up to 5 degrees of sideslip with no marked deterioration of stall handling qualities. They also require a similar result stalling in rain.
I would be loath to comment on your experience without viewing a time history of all parameters relevant to spinning. The problem is that this is a highly dynamic situation and even an experience TP may have difficulty assessing cause and effect without instumentation and data recording.
Wingman, no, I don't use the term skid - a sideslip is a sideslip!
However you are correct in that the terminology seems to be national in origin - my TP training was at Boscome Down, so I guess that there is a good bit of British influence in the terminology I use. Also, when looking at a flight regime such as sideslip I will be invariably assessing the aircraft handling qualities and the compliance with various stability and control requirements.
I note that FAR 23 directional static stability test require that the aircraft recover from a "skid", rudder free. There is no requirement to recover from a "slip" - very strange. Luckily both "slip" and "skid" are just sideslip, so directional static stability demonstrated in one will guarantee compliance in the other.
For your spin resistant aircraft I would add that some certification requirements specify stalling at up to 5 degrees of sideslip with no marked deterioration of stall handling qualities. They also require a similar result stalling in rain.
I would be loath to comment on your experience without viewing a time history of all parameters relevant to spinning. The problem is that this is a highly dynamic situation and even an experience TP may have difficulty assessing cause and effect without instumentation and data recording.
Wingman, no, I don't use the term skid - a sideslip is a sideslip!
However you are correct in that the terminology seems to be national in origin - my TP training was at Boscome Down, so I guess that there is a good bit of British influence in the terminology I use. Also, when looking at a flight regime such as sideslip I will be invariably assessing the aircraft handling qualities and the compliance with various stability and control requirements.
I note that FAR 23 directional static stability test require that the aircraft recover from a "skid", rudder free. There is no requirement to recover from a "slip" - very strange. Luckily both "slip" and "skid" are just sideslip, so directional static stability demonstrated in one will guarantee compliance in the other.
Last edited by zzuf; 7th Apr 2017 at 04:59.
I was going to stay out of this...
No. They are not. They are opposites.
An airplane has a stick. And rudder pedals. They move independently of each other. If the stick is to the left and the rudder to the right, that's a slip. The ball will be well to the inside of the turn.
If the stick is to the left and you have too much left rudder, that's a skid. The ball will be to the outside of the turn.
In both cases "step on the ball" will correct the situation.
Regardless of what prefix you put in front of slip, sideslip, forward slip, etc. it's the same "crossed control" combination. Only the purpose has changed. I can barely remember which is which, but I can slip to lose altitude, and I can slip to correct for a cross wind (prefer to crab, but that's a different topic).
"The dreaded stall spin on the base to final turn" is a skid. Skids are inherently more dangerous as the inside wing stalls first.
Terry
An airplane has a stick. And rudder pedals. They move independently of each other. If the stick is to the left and the rudder to the right, that's a slip. The ball will be well to the inside of the turn.
If the stick is to the left and you have too much left rudder, that's a skid. The ball will be to the outside of the turn.
In both cases "step on the ball" will correct the situation.
Regardless of what prefix you put in front of slip, sideslip, forward slip, etc. it's the same "crossed control" combination. Only the purpose has changed. I can barely remember which is which, but I can slip to lose altitude, and I can slip to correct for a cross wind (prefer to crab, but that's a different topic).
"The dreaded stall spin on the base to final turn" is a skid. Skids are inherently more dangerous as the inside wing stalls first.
Terry
LTCTerry, Thanks for the egg sucking lesson.
Perhaps you could explain what is the opposite of sideslip, bearing i mind that sideslip is simply a velocity along the aircraft lateral axis, what is the opposite?
The two examples you give are indeed opposites, the first the sideslip is to the left, the second the sideslip is to the right.
It seems a strange aircraft in the second example, too much left rudder implies sideslip to the right, in a normal aircraft which has conventional lateral static stability, sideslip to the right will require right aileron to balance the rolling moment due to side slip.
In your case of left stick and (excessive) left rudder, a normal aircraft will be rolling left - one component of the rolling manoeuvre will be the rolling moment due to aileron deflection (left), the other component will be the rolling moment due to sideslip (dihederal effect). That is a left rolling moment due to right sideslip.
I don't use prefixes, so please don't verbal me.
If you seriously believe that the ball is always a proxy for sideslip angle all I can say is that your education is lacking somewhat.
Perhaps you could explain what is the opposite of sideslip, bearing i mind that sideslip is simply a velocity along the aircraft lateral axis, what is the opposite?
The two examples you give are indeed opposites, the first the sideslip is to the left, the second the sideslip is to the right.
It seems a strange aircraft in the second example, too much left rudder implies sideslip to the right, in a normal aircraft which has conventional lateral static stability, sideslip to the right will require right aileron to balance the rolling moment due to side slip.
In your case of left stick and (excessive) left rudder, a normal aircraft will be rolling left - one component of the rolling manoeuvre will be the rolling moment due to aileron deflection (left), the other component will be the rolling moment due to sideslip (dihederal effect). That is a left rolling moment due to right sideslip.
I don't use prefixes, so please don't verbal me.
If you seriously believe that the ball is always a proxy for sideslip angle all I can say is that your education is lacking somewhat.
Moderator
I thought for a minute that this discussion was going to be about 'sideslipping'
You got it in one .. even if it might challenge some of your fondest thoughts on the subject ...
You got it in one .. even if it might challenge some of your fondest thoughts on the subject ...
This should explain the general tendency for an aggressive spin entry from a skidding turn:
http://apstraining.com/traffic-pattern-stalls/
Especially refer Diagram C which is from Rich Stowell.
If you redraw Diagram C in a steady, straight slip you should see why the general tendency for it to be spin resistant.
I've been training instructors in these exercises over the last 15 years or so, mostly in a Decathlon and some in a Cessna Aerobat. Managed to catch a lot of trainee instructors unaware of the approaching stall/spin as the usual symptoms of an approaching stall are not present (or at least nowhere near as obvious as the common straight stall) in a skidded turn stall.
I regard Rich Stowell's book as the best on this subject:
http://www.richstowell.com/shop/book...pin-awareness/
Thoroughly recommended.
http://apstraining.com/traffic-pattern-stalls/
Especially refer Diagram C which is from Rich Stowell.
If you redraw Diagram C in a steady, straight slip you should see why the general tendency for it to be spin resistant.
I've been training instructors in these exercises over the last 15 years or so, mostly in a Decathlon and some in a Cessna Aerobat. Managed to catch a lot of trainee instructors unaware of the approaching stall/spin as the usual symptoms of an approaching stall are not present (or at least nowhere near as obvious as the common straight stall) in a skidded turn stall.
I regard Rich Stowell's book as the best on this subject:
http://www.richstowell.com/shop/book...pin-awareness/
Thoroughly recommended.
Last edited by djpil; 8th Apr 2017 at 00:34. Reason: made the links work - did it on mobile version of the site initially
So, playing instructor, I'll use the term skid per Rich Stowell. I try to keep my engineering life separate.
djpil
How remiss of me quoting an out of date FAR! Of all people I should know better! Somewhere along the line "skid" has been amended to "sideslip" in both the FAR and AC. How perceptive of the authors!
How remiss of me quoting an out of date FAR! Of all people I should know better! Somewhere along the line "skid" has been amended to "sideslip" in both the FAR and AC. How perceptive of the authors!
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Forces In A Turn - Free CFI Tool | Boldmethod
click on this, its an interactive gif , click on the slip, skid and coord buttons and see what happens to the forces.
click on this, its an interactive gif , click on the slip, skid and coord buttons and see what happens to the forces.
