Aerodynamic muslings.

[wonwinglo]

The latest test paper issued by the civil aviation authority has some devious questions,this one caught my eye,I even queried it with them only to be told that it was written by a 20,000 hour pilot,the question is very relevant to large scale models,look at all of the options carefully before making your own decision-

Q3

Why is it that, when an aircraft is flown with an aft C of G

position, it is appreciably less stable in both pitch and yaw?

a. the C of G and C of P are too close together

b. the moment arm of the empennage is reduced

c. C of G makes no difference to stability

d. an aft C of G involves a higher angle of incidence and more

downwash over the tailplane

 

[George]

The latest test paper issued by the civil aviation authority has some devious questions,this one caught my eye,I even queried it with them only to be told that it was written by a 20,000 hour pilot,the question is very relevant to large scale models,look at all of the options carefully before making your own decision-Q3

Why is it that, when an aircraft is flown with an aft C of G

position, it is appreciably less stable in both pitch and yaw?

a. the C of G and C of P are too close together

b. the moment arm of the empennage is reduced

c. C of G makes no difference to stability

d. an aft C of G involves a higher angle of incidence and more

downwash over the tailplane

I think the answer lies in the soil my boy or maybe evn does your chewing gum loose it's flavour on the bed post overnight :coffee:

 

[Glider Guider]

I would say answer a) is correct as the simple plausible answer that makes sense aerodamically (to me). Answer c) is the throw away and the other two sound very technical and could well be correct - but in all honesty I don't really understand them.

 

[wonwinglo]

I would say answer a) is correct as the simple plausible answer that makes sense aerodamically (to me). Answer c) is the throw away and the other two sound very technical and could well be correct - but in all honesty I don't really understand them.

*** Thats fair comment Dave,I dont go for these sort of questions personally as I think they are tactically worded to confuse,typical of the way the CAA complicates things,basically a pilot needs to know his stalling speed,his centre of gravity is correctly calculated,and he has sufficent fuel for flight,the Air Transport Auxiliary delivered all types of high performance aircraft in wartime with little more than a simplified abbreviated 20 page booklet and they followed simple logic ! add to this no navigational aids and poor weather deliveries,but they did a fantastic job delivering front line aircraft.

We will leave it open for a bit for those still trying to work it out.