Sorry about the immediate edit, Carl. I realised you were speaking in those terms, and that is why I withdrew that part! 😉

Thank you DD, that’s an interesting aspect of the graph that I hadn’t noticed :), as I was focussing on the sub-1G region. What you say of course makes a lot of sense! Does it follow that as G decreases, critical angle increases such that it cannot be reached at the theoretical ‘zero G’ point? It doesn’t ‘feel’ right, although the theory suggests it – that’s why it’s bugging me 🙂

P51 seems very likely, but out of interest I did find this:

http://www.flightglobal.com/pdfarchive/view/1942/1942%20-%200234.html

James, my instrument comment was another good reason, meant in a lighthearted way, and not the main reason! Give a man a break :rolleyes: It was a vain attempt to get the thread back on track (as one of the chief diversionists I thought I owed it to the thread). You are the last contributor I’d accuse of not looking and thinking, but.. there seems a lot of it about on this thread (me included).

However, on sober reflection (and contrary to my semantic ramblings) I like the ‘long barrel roll’ solution 🙂

hehe – those two (my amendment, your post) definitely crossed!

Cheers mate 🙂

Matt

hehe – FIGHT! 😀

Seriously though – in a strict aileron roll the aircraft will describe a narrow corkscrew as the wings generate a lateral ‘lift’ component – think of the first quater of the roll – the wing’s lift is not countered by gravity but given increasingly free rein on an increasingly tilted aircraft.. the rest follows.. after all, this is how aircraft turn (in fact – ironically enough – to keep the aircraft on an imaginary straight heading during a roll would require Henshaw-esque ‘down’ elevator inputs.. 😉 ) It is this force, imparted by the wings’ lift, that maintains a degree of positive G throughout where there is no other input in this plane relative to the aircraft.

What I am getting at is that a ‘corkscrew, positive G’ roll can be an aileron roll, and this manouver is misdescribed frequently as a ‘barrel roll’. It should (sorry James) produce lower G loadings (as it is a ‘ballistic’ manouver with no extra inputs) than a barrel roll, making it a more natural candidate for a non-aerobatic aircraft – Douglasdriver, what do you reckon to this?

Thanks chaps for your clarifications – Peter, I was wondering about that :), and Douglasdriver, thanks too.

Perhaps the missing element in discussing aerofoils/lift/incidence is the line of thrust? Not introducing it as a new concept (it has been implied from the off), but another way of looking at the same thing that negates the concern (post 148) about an aircraft assuming an angle to present a zero angle of attack as a natural tendency. It may well do this in a glide, however! Thoughts from gliding experten?

A surface ‘angled’ to the line of thrust by definition is not symetrical along that line, whether it maintains an internal symetry or not, and thus generates a net aerodynamic force perpendicular to thrust as well as drag – but I may be way off beam here. After all, I wasn’t even aware of internally-symetric lifting surfaces until a couple of days ago! That’s why I like it here 🙂

James, is the ‘in between’ one you are after sometimes called a ‘ballistic roll’ (but only as distinct – as a form of aileron roll – from a ‘slow roll’ which implies negative G)? It conforms to the definition ‘a barrel roll that does not require the flightpath divergence or G load that the official descriptions of the barrel roll do’ although it is often synonymous with ‘aileron roll’ too. Google would imply something like this, but Google is not the Oracle, of course, as you ably demonstrated with the t-time theory!

I am not stating this, I’m asking people..

Yes, fascinating stuff to me, certainly – I’m re-creating a Clarke YH profile at the moment – re-assuringly asymetric! No prizes for guessing/working out/recognising the aircraft 😉

Fascinating about the symetrical aerofoils. Done a bit of digging – For anyone interested: Extra 300 = Ma15 to Ma12s, F86 = NACA 0009.5 to NACA 0008.5. and L-1649A = NACA 0015 to NACA 0011

I see your point, Fanavion. Essentially, with that system in balance (ie level flight) the forces are indeed the same. The only variation is the sense of the force of gravity relative to the aircraft structure – positve one way up, negative the other way up. Similarly the applied lift/weight stress is reversed as it applies to the structure.