Lazy Slat causing unstable approach

For general discussion of the Just Aircraft family of aircraft.
Includes: Highlander, Escapade, Summit and SuperSTOL.
Post Reply
User avatar
BDA
Veteran Member
Posts: 707
Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Lazy Slat causing unstable approach

Post by BDA »

Since my first flight I have had the left side inboard slat not come out when the others do.

So the slats on the right come out, and that wing goes up, the left wing does not, so I correct w aileron and the left slat then comes out, and causes over correct.

The first time it happened I was short final 100’ off the ground and thought I was a gonner. Drop a wing when slow ... not good.

So nobody seemed to have any helpful advice (I was told that propwash kept it in) either way, it sucks.

I thought VGs could help, so I put 4 VGs on the outboard end of the lazy slat at 60 mm spacing 5/8” from leading edge.

And just like that - no more lazy slat, it acts just like the other slats now.

Lucky guess works for me!!
SuperStol XL Alaskan With Titan 340
N331AK. Shawn Taplin
Wing extensions,Symetrical Airfoil tail ribs (NACA 21)
Mods in progress: Heavier struts, Double slotted flaps
Goal: 15mph no wind
Clark in AZ
Veteran Member
Posts: 356
Joined: Wed Oct 07, 2015 11:40 am
Location: Cave Creek, AZ

Re: Lazy Slat causing unstable approach

Post by Clark in AZ »

Interesting. So, you only have vgs over that slat?

Clark
Building SuperSTOL Kit 512
Cave Creek, AZ
User avatar
BDA
Veteran Member
Posts: 707
Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Re: Lazy Slat causing unstable approach

Post by BDA »

Yes, and only 4
SuperStol XL Alaskan With Titan 340
N331AK. Shawn Taplin
Wing extensions,Symetrical Airfoil tail ribs (NACA 21)
Mods in progress: Heavier struts, Double slotted flaps
Goal: 15mph no wind
dkshow
Veteran Member
Posts: 114
Joined: Wed Feb 12, 2014 8:19 pm
Location: Anchorage, AK

Re: Lazy Slat causing unstable approach

Post by dkshow »

Sounds strange, like that one is sticky. My slats come out whenever they want, usually the right first then left but it's never made any noticeable difference or dropped a wing ever. I've got VGs on the outboard half of my wings in front of my ailerons, I may add more this summer.
Keith Showalter
More Photos at www.keithshowalter.com
Anchorage, Alaska Superstol N445K
Built in NC with Rob Pedersen, Plane Fun Aircraft
User avatar
BDA
Veteran Member
Posts: 707
Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Re: Lazy Slat causing unstable approach

Post by BDA »

Ya I have checked it for “sticky” about 1,000 times now. Whatever it is, it is def aerodynamic.
I think the wing drop was more overcorrection with the spoiler coming up killing lift then oposite wing slat finally comming out.

They operate normally now. Easy in and out, and deploy at the same time on final.

I just put the covers on my strut attach points, maybe the airflow was weird around those open holes.

You def need VGs in front of the flaps.

When you gonna get that thing out for summer Kieth??
SuperStol XL Alaskan With Titan 340
N331AK. Shawn Taplin
Wing extensions,Symetrical Airfoil tail ribs (NACA 21)
Mods in progress: Heavier struts, Double slotted flaps
Goal: 15mph no wind
dkshow
Veteran Member
Posts: 114
Joined: Wed Feb 12, 2014 8:19 pm
Location: Anchorage, AK

Re: Lazy Slat causing unstable approach

Post by dkshow »

I'm hoping to get back in the air next week. I've got a couple of little things I want to do like replace my turtle deck. Mine has lasted 5 years and it's time for a fresh one.
Keith Showalter
More Photos at www.keithshowalter.com
Anchorage, Alaska Superstol N445K
Built in NC with Rob Pedersen, Plane Fun Aircraft
User avatar
BDA
Veteran Member
Posts: 707
Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Re: Lazy Slat causing unstable approach

Post by BDA »

You can use my brake if you need
SuperStol XL Alaskan With Titan 340
N331AK. Shawn Taplin
Wing extensions,Symetrical Airfoil tail ribs (NACA 21)
Mods in progress: Heavier struts, Double slotted flaps
Goal: 15mph no wind
Clark in AZ
Veteran Member
Posts: 356
Joined: Wed Oct 07, 2015 11:40 am
Location: Cave Creek, AZ

Re: Lazy Slat causing unstable approach

Post by Clark in AZ »

dkshow wrote:I'm hoping to get back in the air next week. I've got a couple of little things I want to do like replace my turtle deck. Mine has lasted 5 years and it's time for a fresh one.
What's wrong with your turtle deck? Scratches, weathering, or something else? Anything you would do differently on the next one?
Building SuperSTOL Kit 512
Cave Creek, AZ
User avatar
BucF16
Veteran Member
Posts: 463
Joined: Sun Mar 23, 2014 11:47 am
Location: Alexandria, Ohio

Re: Lazy Slat causing unstable approach

Post by BucF16 »

Hi Clark, Keith's turtle deck is 100% Lexan that he put on a brake for the sides. My Guess is it is crazing after 5 years.
Bruce Johnson Highlander # 393
"Because I fly, I envy no man on Earth"
Builder web site:
http://www.bruceshighlander.blogspot.com
Clark in AZ
Veteran Member
Posts: 356
Joined: Wed Oct 07, 2015 11:40 am
Location: Cave Creek, AZ

Re: Lazy Slat causing unstable approach

Post by Clark in AZ »

Ah, that makes sense. Thanks for the response.
Building SuperSTOL Kit 512
Cave Creek, AZ
User avatar
CanadianSheepHunter
Veteran Member
Posts: 678
Joined: Thu Feb 26, 2015 1:05 pm

Re: Lazy Slat causing unstable approach

Post by CanadianSheepHunter »

So if im reading this correctly you put 4 VG's on the top side of the slat itself? Do you still have them on that slat?
User avatar
BDA
Veteran Member
Posts: 707
Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Re: Lazy Slat causing unstable approach

Post by BDA »

Yep, outboard end of inner slat, left wing.
Havent got around to re-rig the slat yet.
It works fine now.
User avatar
BDA
Veteran Member
Posts: 707
Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Re: Lazy Slat causing unstable approach

Post by BDA »

Well, I finally got around to taking the slat apart to figure out what was going on.
The outboard end had a little vertical play as installed. So when I took it apart, I found more spacer washers than needed, so there was too much distance between the bearings. So the bearings were not bottomed out in the bracket and allowed the slat to move up and down about 1/8” at the bearing, but that turned out to be much more at the slat.
I remember now, when I installed, putting more spacers in there to stop that movement up and down.
Pretty sure that I had a bearing not seated all the way down - but stuck. So there was more space between bearings than there should have been.
So after some flight time the bearings seated all the way and then there were too many spacers causing the bearings to be too far apart, and sloppy.
User avatar
BDA
Veteran Member
Posts: 707
Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Re: Lazy Slat causing unstable approach

Post by BDA »

Flight test complete
Slat works as new now.
No weird late or delayed opening, no snapping out at the last second.
I did not do much really slow stuff because the wind was blowin 20, I was slow enough already.
Happy with it now.
I Should have made slat tune-up a 20 hour check during the break in period.
Post Reply

Return to “Just Aircraft”