Taildragger Tailwheel Springs
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JW Scud
- Posts: 252
- Joined: Sun Aug 14, 2016 12:44 am
Was talking recently to a pilot who has flown a variety of aircraft and he mentioned about a CAP 10 that he did some flying on. He had flown one in the distant past but this particular plane was new to him. He said that during the latter portion of the rollouts, the aircraft became a real handful to control. The problem turned out to be what he called, loose springs. Once they were tightened, everything operated normally. I always check the springs on a walkaround but is there some obvious way to be able to tell if they are loose or when they are not satisfactory. Can they really be tightened?
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Slick Goodlin
- Posts: 721
- Joined: Thu Jun 11, 2015 6:46 pm
If he means steering springs, you just take a link or two out of the chains as required. I’ve also had it where the leaf spring was all floppy and weird, but I forget the fix used there.
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cgzro
[quote author=JW Scud link=topic=9404.msg25993#msg25993 date=1544214580]
Was talking recently to a pilot who has flown a variety of aircraft and he mentioned about a CAP 10 that he did some flying on. He had flown one in the distant past but this particular plane was new to him. He said that during the latter portion of the rollouts, the aircraft became a real handful to control. The problem turned out to be what he called, loose springs. Once they were tightened, everything operated normally. I always check the springs on a walkaround but is there some obvious way to be able to tell if they are loose or when they are not satisfactory. Can they really be tightened?
[/quote]
He may have been getting shimmy. While tightening the springs will help reduce the shimmy its really a tail wheel geometry problem and needs to be addressed with a proper leaf spring curve angle. You can adjust the chains by either rotating them 1/2 turn, or you can add some safety wire a few loops to bring two links a little bit closer together where they mate. I used to be very fussy about it but realistically if the tail wheel pivot axes geometry is correct and the tail wheel is properly inflated and the plane not over loaded a little slack or tight does not make a huge difference in my experience and I've flown planes with full casting, locking and different degrees of springiness in between.
Was talking recently to a pilot who has flown a variety of aircraft and he mentioned about a CAP 10 that he did some flying on. He had flown one in the distant past but this particular plane was new to him. He said that during the latter portion of the rollouts, the aircraft became a real handful to control. The problem turned out to be what he called, loose springs. Once they were tightened, everything operated normally. I always check the springs on a walkaround but is there some obvious way to be able to tell if they are loose or when they are not satisfactory. Can they really be tightened?
[/quote]
He may have been getting shimmy. While tightening the springs will help reduce the shimmy its really a tail wheel geometry problem and needs to be addressed with a proper leaf spring curve angle. You can adjust the chains by either rotating them 1/2 turn, or you can add some safety wire a few loops to bring two links a little bit closer together where they mate. I used to be very fussy about it but realistically if the tail wheel pivot axes geometry is correct and the tail wheel is properly inflated and the plane not over loaded a little slack or tight does not make a huge difference in my experience and I've flown planes with full casting, locking and different degrees of springiness in between.
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Colonel
- Posts: 3450
- Joined: Wed Apr 29, 2015 10:31 am
There are often two sets of springs used for a tailwheel assembly.
The heaviest is the set of leaf springs that are used to connect the
fuselage to the tailwheel bracket. Over time, these springs sag and
instead of the tailwheel pivot being vertical, it changes to trailing and
that promotes shimmy.
[img width=500 height=341]https://glasair-owners.com/wp-content/u ... 64x385.jpg[/img]
Some people try to save $$$ and re-arch the springs but I've had
them break - the big leaf springs - and that's not good, when the
tailwheel falls off. Change them every decade or two. They have
a life cycle limit. From a notable contributor here (one of my two
favorite socialists (really)):
[img width=500 height=281][/img]
Don't do that, even if you're a socialist, ok?
The other set of tailwheel springs is the two light tension springs (for
maximum confusion, Maule compression springs shown) that connect
the steering horn to the tailwheel.
[img]https://secure.steenaero.com/Store/imag ... 20x240.jpg[/img]
Over time these springs stretch and as Peter says, need to have a link
taken out of each side or even replaced, when the spring is done. There's
a bit of a dance to removing links. Hint: zip ties and two pairs of pliers.
Be careful during your pre-flight to ensure that the four spring end connectors
have NOT opened up because when they let go, it's not fun. If you see
them opening up on the pre-flight, give them a squeeze with the water pump
pliers.
[img]https://www.aircraftspruce.com/cache/37 ... 15400a.jpg[/img]
99% of pilots depart the runway when those clips let go. The tailwheel
is fully deflected, and that requires an unusually skilled pilot (probably
less than 10 in all of Canada) to keep it on the runway. I personally like
to replace them with the link type:
[img width=500 height=500]https://images.homedepot-static.com/pro ... 4_1000.jpg[/img]
Forty-seven years of tailwheel flying, and counting, which explains why
TC still won't return my laptop and phone, after nearly three years after
they were seized. I hope Arlo's kids appreciate them.
The heaviest is the set of leaf springs that are used to connect the
fuselage to the tailwheel bracket. Over time, these springs sag and
instead of the tailwheel pivot being vertical, it changes to trailing and
that promotes shimmy.
[img width=500 height=341]https://glasair-owners.com/wp-content/u ... 64x385.jpg[/img]
Some people try to save $$$ and re-arch the springs but I've had
them break - the big leaf springs - and that's not good, when the
tailwheel falls off. Change them every decade or two. They have
a life cycle limit. From a notable contributor here (one of my two
favorite socialists (really)):
[img width=500 height=281][/img]
Don't do that, even if you're a socialist, ok?
The other set of tailwheel springs is the two light tension springs (for
maximum confusion, Maule compression springs shown) that connect
the steering horn to the tailwheel.
[img]https://secure.steenaero.com/Store/imag ... 20x240.jpg[/img]
Over time these springs stretch and as Peter says, need to have a link
taken out of each side or even replaced, when the spring is done. There's
a bit of a dance to removing links. Hint: zip ties and two pairs of pliers.
Be careful during your pre-flight to ensure that the four spring end connectors
have NOT opened up because when they let go, it's not fun. If you see
them opening up on the pre-flight, give them a squeeze with the water pump
pliers.
[img]https://www.aircraftspruce.com/cache/37 ... 15400a.jpg[/img]
99% of pilots depart the runway when those clips let go. The tailwheel
is fully deflected, and that requires an unusually skilled pilot (probably
less than 10 in all of Canada) to keep it on the runway. I personally like
to replace them with the link type:
[img width=500 height=500]https://images.homedepot-static.com/pro ... 4_1000.jpg[/img]
Forty-seven years of tailwheel flying, and counting, which explains why
TC still won't return my laptop and phone, after nearly three years after
they were seized. I hope Arlo's kids appreciate them.
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Slick Goodlin
- Posts: 721
- Joined: Thu Jun 11, 2015 6:46 pm
Every taildragger I’ve flown with a spring-steered tailwheel has had the springs rigged with a little slack in them. I don’t know whether it’s just an age and wear thing but if one were to ever let go the tailwheel shouldn’t go hard over that way. Those steering springs are only there to give a suggestion of steering anyways, I don’t see the harm in having a little slop in the middle.
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