Princples of Flight Question

[Wagit]

Who can tell me what the difference is between aerodynamic balancing and mass balancing of flight controls??????

[Blue Hauler]

Wagit

Have a look at a Cessna 152. The horns on the tips of the elevators are aerodynamic balances. Designed to provide aerodynamic leverage forward of the hinge and thereby ease control pressures in flight.

If you raise the aileron on the same aircraft and look along the hinge-line you will see a lead mass balance designed to dampen the effects of flutter.

[Zeke]

If you raise the aileron on the same aircraft and look along the hinge-line you will see a lead mass balance designed to dampen the effects of flutter.

Could be for aeroelastic aileron reversal.

[*Lancer*]

On a 152? :D

[Possum 15]

Mass Balancing
Mass balancing is used chiefly to prevent flutter of the control surfaces. Balancing is carried out by fixing weights to the leading edge of the control surface so that the centre of gravity of the surface is brought closer to the hinge line. Balances can be mounted externally or, in most cases, internally.

Aerodynamic Balancing
Aerodynamic balancing is achieved in several ways, all of which decrease the the force required to move the control in flight. This form of balancing is generally done by hinging the control surface about a line set back from the leading edge. The effort required to move any control surface is determined by the aerodynamic force acting through the centre of pressure of the airfoil multiplied by the distance from the hinge line. This force is known as the hinge moment of the control surface: the smaller the hinge moment the less is the effort required to move the surface through a given angle at a given speed.
:confused:

[Wagit]

Well done possum 15. That was a text book answer. All I need to know is which text book did you get that one out of?

Zeke can you explain "aeroelastic aileron reversal".


Next question is:

Can aircraft designers incorporate mass balance and aerodynamic balance together ? If so can someone give me an example?

[Possum 15]

Sorry Wagit. Can't help you with the text book. From my notes when I took an active interest in my travelling companion's future. These days, during the long hours of cruise, I drink coffee, pee once an hour and read the sports pages.

Mass/Aerodynamic balance
On some control surfaces, instead of an inset hinge line, aerodynamic balance can be achieved by using a horn balance. This has the same effect as an inset hinge type as a proportion of the total area lies ahead of the C.P. (Centre of Pressure). If mass is added, internally, to the horn then the effect is a combined mass/aerodynamic balance. These are used mostly on rudders and elevators.
The use of inset hinge or horn balances is normally limited to comparatively slow aircraft. To obtain the high degree of balance necessary to obtain reasonable stick forces at high speed, balance tabs are required. At still higher speeds, in spite of maximum use of aerodynamic balancing, the loads on control surfaces are prohibitive.
"On the next sector we will discuss hydraulic and other forms of boosted control systems. Please be prepared"
:D

[Tinstaafl]

Wagit

Since Cessna's have been mentioned...

The elevators & rudders of Cessna singles have a combined aerodynamic & mass balance. Lead weights are fixed inside the horn balance.

Most of the common light a/c tend to use this combination.

[Wagit]

Possum 15 thanks for the info. I asked these two questions to see what reaction I would get. I’ve been asking these questions on instructor rating renewals and getting blank looks !!!!!!!!

Interesting on 1 or 2 people responded.

You quite obviously know what you are talking about. I have found a interesting site on the UK CAA website have a look and see what you think.

http://www.caa.co.uk/srg/general_aviation/document.asp?groupid=231

Wagit

[QNIM]

Wagit
I wish that was all I was asked on my renewals.
Cheers Q:D