Locking tailwheel release

Alan George · Post by **Alan George** » Sat Oct 15, 2011 10:09 am

Hello All,

I am involved in a Pitts S-1 rebuild project that has a Haigh(?) locking tailwheel but no release mechanism. I am thinking of using Bowden cable for the connection but I am looking for ideas/advice/photos on the cockpit control. Something that defaults to the locked position, is clear to operate, looks professional and is either mounted on the panel or on the steel tube fuselage frame.

Thanks, Alan.

Alan George · Post by **Alan George** » Mon Oct 24, 2011 10:32 pm

Surely we cannot have the only locking tailwheel in the LAA fleet?

I will re-phrase the question, does anyone know anyone who has a locking tailwheel whatever the release mechanism?

Thanks, Alan.

Ian Melville · Post by **Ian Melville** » Tue Oct 25, 2011 8:34 am

Hi Alan,
I expect there are quite a few locking tail wheels, but most I have seen are the type that have a detent, and just require sufficient side force on the wheel to break out, no levers or controls in sight. Scott tail wheel is one of the best known.

I found this reference to a Haigh tail wheel is a Steen Skybolt article.

I'm not a fan of locking tailwheels on little airplanes, but this one worked quite well. Wallace had used the throttle assembly off a lawn mower as the engage mechanism which was located under my left hip. With the tailwheel locked,

Some lawnmowers just use friction, others have a gated throttle

Rob Swain · Post by **Rob Swain** » Tue Oct 25, 2011 10:58 am

As Ian says, many tailwheels are locked and can break out to free castor when required.

If such a tailwheel, like the Scott or the much cheaper Maule, is fitted then the way to make it castor out is NOT to just apply lots of side force, you should pull the actuating arms round using the rudder to steer in the normal way, and when the wheel steering pivot is around far enough it will break out into free castor.
Just expecting the wheel to break out because you have one of the main wheels locked and one not so dragging the tail sideways is being very unkind to the tailwheel, tail spring, chains, rudder horns, rudder hinges and the tail of the aircraft generally.

Taking such a tailwheel off the aircraft, or lifting the tail, and having a play with the mechanism should demonstrate how it works and such understanding should enable you to control the aircraft on the ground much more easily.

Ian Melville · Post by **Ian Melville** » Tue Oct 25, 2011 1:59 pm

Rob is quite right, I over simplified the set up

Scott tail wheels are steered, Haigh are not IIRC

Alan George · Post by **Alan George** » Tue Oct 25, 2011 9:22 pm

Yes I am familiar with steerable tailwheels that become free castoring when you steer pass a detent. I normally fly an RV-4 that has the Vans version of this, easy handling and useful for tight manoeuvres.

However the Pitts has a tailwheel that is locked in the straight ahead position, then when you pull the release it is free castoring. Apparently you want locked for take off and landing and castoring for low speed taxi turns.

Thanks Ian, I am now googling for cool lawnmower throttles - the glamour of aviation!

Mark A · Post by **Mark A** » Wed Oct 26, 2011 12:01 am

I think that the Raven tailwheel has effectively taken over from the Haigh one now: http://www.ravenaircraft.com/cat_airframe.html
I guess a push-pull bowden wire, similar to those used on carb heat/cabin heat flaps would suffice.

Normally the preserve of larger tailwheel types, but I guess it tames the pedal dancing on the Pitts to some degree.

I recall what happened when the Bristol Freighter attempted a take off at Enstone with the tailwheel unlocked - http://www.airliners.net/photo/Bristol- ... 77be4d1f5b

NickChittenden · Post by **NickChittenden** » Wed Nov 09, 2011 1:38 pm

The AAIB accident report makes no mention of failure to lock the tail wheel. The accident was attributed to loss of control during take-off. The link to the AAIB report is below. The Bristol 170 series had a reputation for being a bit of a handful in a crosswind, even in the day when large tail wheel aircraft were more prevalent. The control system of the 170 included an interlock between the aileron and rudder control. The interlock did not allow more than a modest amount of cross control, which could be problematic in a cross wind. For instance, were one to roll the control wheel fully to the left, it would be impossible to deflect the rudder to the right; decreasing the roll input would allow a modest amount of opposite rudder, and vice versa. Those of use lucky enough to be brought up on a diet of Dakotas find this whole concept of limiting control input quite ghastly, no doubt the interlock was fitted to avoid tailplane ‘blanking’ with side slip.

The Bristol 170 tail wheel lock is also worthy of mention. Instead of a cable and spring arrangement which served so well on the Dakota, Mr Bristol fitted a solenoid in the tail, complete with 5 minute usage limit. After 5 minutes the solenoid was apt to burn itself out! I heartily recommend the cable and spring arrangement on a homebuilt.

http://www.aaib.gov.uk/cms_resources.cf ... 502112.pdf