Hi Gentreau, thanks for your response!
I'm confident that I understand the principle of angle of attack versus attitude. So for example in a normal glide, the angle of attack will be steeper than the attitude.
The statement in question is in chapter 2, (page 31 in my version), under the subheading "The Mushing Glide" he says:
Having just read that again, I notice he says "slightly" which I thought might be the key.
I think I need to summarise some of his definitions in order to be precise about the aerodynamics of a nose-up glide; at least for me to refer to:
"Chord is the line from the frontmost to the rearmost point of the wing section".
Angle of attack is "the angle between the chord and the relative wind".
Absolute angle of attack: "The angle that the no-lift line makes with the oncoming air".
"[therefore] a wing can develop lift at zero or even at negative Angle of Attack".
Angle of incidence is "the angle at which [the] wings are set with reference to the lengthwise axis of [the] airplane". (I don't know if this refers to the chord or the no-lift line".
So if I try to step through this problem:
Assume the aircraft is moving forwards. It will have drag opposing this motion.
For forward velocity to be constant, there must be a forward force opposite and equal to the horizontal drag force.
Assume that the fuselage and stabilisers and everything but the main wings create no forward force. (?)
Sub-conclusion: therefore, the wings must apply a forward force to the aircraft. (?)
I tried sketching a few diagrams of relative wind and lift. As per point (4), I conclude that the lift has to have a forward component.
If I then assume that lift is perpendicular to the no-lift line, then if the aircraft is nose-high (or even perfectly horizontal), I believe the lift would actually generate a negative horizontal component.
I'm digging a hole for myself here!!
If his statement about nose-up gliding is correct, and my arguments 1-4 are valid, then the lift is significantly forward of the no-lift perpendicular. Perhaps that's the quesiton I should be asking, but my brain is now stalled, this is going to need a lot of coffee to get my head round!!!