I admit I am quite ignorant when it comes to alot of aspects of aircraft anatomy. I could use some help.
I’m building a Sopwith Snipe and I have a reference that tells me the late model Snipe that I am building had horn-balanced ailerons on the upper wings as opposed to just plain vanilla ailerons that were on the early types. I have several photos of late and early types and I cannot see any noticable difference in the appearance of the upper wing ailerons or the little arms that stick out of the top of them where the actuating wires attach.
Is a horn-balance something that is visible ? Or modelable ? (Is that a word ?)
I think it’s a counter balancing technicque used by some old manufactures of aircraft. It like the Ju-52 type aircraft that had small “horns” on the ailerons. They could be internal or external.
At first I thought the horn balances were just the little arms that are attached to the top of the ailerons. But those little arms are in photos of Snipes that are of both the early and late types. (?)
I started the rigging for this little bugger today. There are around 34 or 36 little pieces of stretched sprue rigging that I’ve got on it so far. I think I’m done - but there are a few control surface actuation wires that I’m not sure whether I’m going to apply. I was hoping for a resolution to this question before I took on that project. Oh well.
I think that’s right as well, but I wouldn’t swear to it. I’ve seen flight control surfaces with a counterbalance on them that had a somewhat aerodynamic shape to them. Presumably the shape changed the amount of balance at different airspeeds.
A horn balance is usually an arm that has a tear-drop shaped ball on the end. Although some were just a plain round ball. You could balance out an aircraft design according to where it was placed on the aileron or elevators. A good example would be the P-38, look at the elevator surfaces on it and you will find one on both sides. Kelly swore to the last of his days that they had no effect whatsoever and only added unneccassary weight to the airframe.
And if you notice, they are placed at the leading edge of the particular control surface, either aileron or elevator. They are angled forward with the little ball, heaviest mass, ahead of the hinge line. The primary purpose of these thingies is to stop or reduce the onset of control surface flutter. Flutter is an aerodynamic anomaly that occurs at high speed where the surface moves in opposite directions at high frequency. If you don’t get it stopped within a couple of seconds, it will destroy the moveable surface and maybe the fixed surface it is attached to. In severe cases, where speed is increasing radily and the plane gets to flutter speed and goes beyond quickly, the whole works can self destruct in less than one second.
In other words, if you are in a high speed aircraft, such as a P-38 in a steep dive and flutter occurs, before you even realize what is happening, you are already SOL. I have seen this phenomena destroy a number of RC planes. Sometimes, if it is not too severe you can get it stopped before catastrophic failure occurs. The only thing to do is immediatel chop the throttle and pull up, so as to bleed off speed quickly.
The balancing of aircraft control surfaces is very critical. An unbalanced or improperly balanced control surface can develop flutter (especially as higher airspeeds are attained) and under worst case scenerio will depart the aircraft (ref V-tailed Beech Bonanzas - aka “Doctor Killers”). The earliest method of achieving balance during manufacture was the “Horn Balanced” surface (aileron, rudder or elevator). To properly balance a surface, a certain amount of weight must be placed forward of the hinge line to counteract the weight of the surface aft of the hinge line. On early, low speed aircraft the easiest way was to extend the control surface beyond the end of the fixed surface it was attached to and extend it forward of the hinge line. This added weight forward and also created a location where more weight could be added if needed. WW I Fokker fighters have excellent examples of this.
As airspeeds went higher and metal structures became more common, the horn balance fell out of favor because of other factors that came into play. If you think about it, there is a heck of a lot more air pressure on a horn balance if it is fully deflected at 400 kts than on one which is fully deflected at 110 kts. This would lead to the failure of the surface. Someone figured out that you could balance the surface by either placing weights inside the leading edge of the control surface forward of the hinge point or adding a weight to one or both sides of the surface which consisted of a tube which extended outwards and forwards of the hinge line (usually attached to the surface’s spar) and placing a weight at the end (ala P-38 and Bf 109). These are known as Mass Balances and are used to this day (although most are now internal).
The difference between mass ballancing and horn ballancing is that mass ballancing is sitting forward of the control surface to reduce flutter eg p38 lightning tail elevator and Halifax ailerons, where as mass ballancing is primarally used to reduce control wheel pressure, and works in the opposite direction of the control surface also reducing flutter. Well thats what i learned in commercial pilots theory…
sorry i meant where as HORN ballancing is primarally used to reduce control wheel pressure, and works in the opposite direction of the control surface also reducing flutter. Well thats what i learned in commercial pilots theory…
As speed increased and systems and aircraft became more advanced, aircraft flight controles were dampened by gyros. With electronics, a flutter could be dampened before the pilot even knew there was a problem.
Aircraft now no longer have to have mass balancers installed because sensors detect a flutter and correct problems in a micro second. The old F-4 series of aircraft, the flight control gyros and servos would cycle several times a second to maintain steady flight controles. When the system malfunctions, the crew will have their hands full flying the aircraft.