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rparigoris
Joined: 24 Nov 2009
Posts: 792
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 Posted: Wed Oct 09, 2019 12:53 pm Post subject: Help needed understanding uncoordinated flight |
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Hi Group
I was wondering if someone could help me understand an aspect of uncoordinated flight I just can't seem to get my head around 
I was reading in October 2019 EAA a Commentary from Charlie Precourt titled " Loss of control - a survivors story". In short a Kitfox stalled and spun in having too much bottom rudder in the process. He didn't have a stall warning indicator.
What I can't get my head around is a commentary of recalling the aerodynamics of uncoordinated flight that states a slip has the fuse generating lift and in a skid the fuse generating negative lift forcing the wing having to create more lift than in coordinated flight exasperating things and raising the stall speed.
Can anyone perhaps better explain to me specifically lift generated by the fuselage? Here's the paragraph that has me confused:
"At this point, it might be helpful to recall the aerodynamics of uncoordinated flight and why a slip is okay but a skid is dangerous in the pattern. When we fly a side-slip, for example, to help lose altitude on approach, the fuselage is generating lift because the top rudder puts the relative wind on the lower part of the fuselage. This added lift unloads the wings and reduces our stall speed. On the other hand, in a skidding turn, the relative wind acts on the upper side of the fuselage, creating down force in the direction of weight, loading up the wings, and increasing our stall speed. Just the act of adding the skidding rudder can induce an immediate stall if the speed we are flying in the turn is close to stall.'
This is exactly what happened to Nikk, the poor sole with the Kitfox.
I just can't picture how the fuse in a skid has higher pressure air on the top of the fuse.
Thx.
Ron P.
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jan_de_jong(at)casema.nl
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| Posted: Wed Oct 09, 2019 1:55 pm Post subject: Help needed understanding uncoordinated flight |
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Hi Ron, my 2 cents.
In turning descent or level flight the inside wing will stall first.
I remind myself of:
1. top rudder, in order to lead with the inside wing - slip, not skid
2. apply progressively, not suddenly - do not yank a wing back
I understand that in a turning climb the outside wing may stall first
though.
The fuselage decreases the airflow over the inner part of the wing that
is pulled back, decreasing lift of that wing, compensated with aileron.
I don't think there is fuselage lift involved in explaining anything.
Jan
On 9-10-2019 22:53, rparigoris wrote:
| Quote: |
Hi Group
I was wondering if someone could help me understand an aspect of uncoordinated flight I just can't seem to get my head around
I was reading in October 2019 bEAA a Commentary from Charlie Precourt titled " Loss of control - a survivors story". In short a Kitfox stalled and spun in having too much bottom rudder in the process. He didn't have a stall warning indicator.
What I can't get my head around is a commentary of recalling the aerodynamics of uncoordinated flight that states a slip has the fuse generating lift and in a skid the fuse generating negative lift forcing the wing having to create more lift than in coordinated flight exasperating things and raising the stall speed.
Can anyone perhaps better explain to me specifically lift generated by the fuselage? Here's the paragraph that has me confused:
"At this point, it might be helpful to recall the aerodynamics of uncoordinated flight and why a slip is okay but a skid is dangerous in the pattern. When we fly a side-slip, for example, to help lose altitude on approach, the fuselage is generating lift because the top rudder puts the relative wind on the lower part of the fuselage. This added lift unloads the wings and reduces our stall speed. On the other hand, in a skidding turn, the relative wind acts on the upper side of the fuselage, creating down force in the direction of weight, loading up the wings, and increasing our stall speed. Just the act of adding the skidding rudder can induce an immediate stall if the speed we are flying in the turn is close to stall.'
This is exactly what happened to Nikk, the poor sole with the Kitfox.
I just can't picture how the fuse in a skid has higher pressure air on the top of the fuse.
Thx.
Ron P.
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peterz(at)zutrasoft.com
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| Posted: Wed Oct 09, 2019 2:15 pm Post subject: Help needed understanding uncoordinated flight |
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Description makes sense to me, but the it is not the top of the fuse, but rather the right side of the fuse with inside left rudder, and with the bank that puts a percentage vector of the right side fuse pushing downward due to the flow against it, adding to the effective weight, angle of attack etc.
Cheers,
Pete
| Quote: | On Oct 9, 2019, at 5:01 PM, rparigoris <rparigor(at)hotmail.com> wrote:
Hi Group
I was wondering if someone could help me understand an aspect of uncoordinated flight I just can't seem to get my head around
I was reading in October 2019 bEAA a Commentary from Charlie Precourt titled " Loss of control - a survivors story". In short a Kitfox stalled and spun in having too much bottom rudder in the process. He didn't have a stall warning indicator.
What I can't get my head around is a commentary of recalling the aerodynamics of uncoordinated flight that states a slip has the fuse generating lift and in a skid the fuse generating negative lift forcing the wing having to create more lift than in coordinated flight exasperating things and raising the stall speed.
Can anyone perhaps better explain to me specifically lift generated by the fuselage? Here's the paragraph that has me confused:
"At this point, it might be helpful to recall the aerodynamics of uncoordinated flight and why a slip is okay but a skid is dangerous in the pattern. When we fly a side-slip, for example, to help lose altitude on approach, the fuselage is generating lift because the top rudder puts the relative wind on the lower part of the fuselage. This added lift unloads the wings and reduces our stall speed. On the other hand, in a skidding turn, the relative wind acts on the upper side of the fuselage, creating down force in the direction of weight, loading up the wings, and increasing our stall speed. Just the act of adding the skidding rudder can induce an immediate stall if the speed we are flying in the turn is close to stall.'
This is exactly what happened to Nikk, the poor sole with the Kitfox.
I just can't picture how the fuse in a skid has higher pressure air on the top of the fuse.
Thx.
Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=491716#491716
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jan_de_jong(at)casema.nl
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| Posted: Thu Oct 10, 2019 7:43 am Post subject: Help needed understanding uncoordinated flight |
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Resending (disappeared yesterday).
Hi Ron, my 2 cents.
In turning descent or level flight the inside wing will stall first.
I remind myself of:
1. top rudder, in order to lead with the inside wing - slip, not skid
2. apply progressively, not suddenly - do not yank a wing back
I understand that in a turning climb the outside wing may stall first
though.
The fuselage decreases the airflow over the inner part of the wing that
is pulled back, decreasing lift of that wing, compensated with aileron.
I don't think there is fuselage lift involved in explaining anything.
Jan
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Fri Oct 11, 2019 7:08 am Post subject: Re: Help needed understanding uncoordinated flight |
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Thanks Group. I think I got it. A powerful aeroplane can fly knife edge with no wing at all doing the lifting if the fuse is at a positive angle of attack. Go negative angle and it creates negative lift. Because of vector, more bank angle will equate to positive or negative lift in uncoordinated flight. Ron P.
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