Originally Posted by Honkozzie
I think you're missing my point somewhat!
If you are trying to make a point using mistaken ideas about aerodynamics, then you are failing to make your point. If your point is well taken, you should be able to make it without using mistaken reasoning. So best to try, no?
Originally Posted by Honkozzie
The other point I was making with regards to TAS was purely one of increased momentum at altitude. For a given gust vector, an increase in TAS (for a given IAS/EAS)will result in a greater resultant displacement vector from the flight path. And we all (hopefully)know what that can result in...
As far as I can interpret it, this statement seems to be misleading as well.
You talk about a "resultant displacement vector". "Resultant" is a technical term in dynamics for what you get by summing two other vectors, in this case they must be distance vectors. But I don't see those in your story so far. There is a velocity vector in the direction of flight path, and an acceleration vector, caused by the gust, normal to it. To get a resultant, you need to sum distance vectors, or velocity vectors, or acceleration vectors, but you have so far only adduced one of each, so there is no "resultant". Maybe you mean "resulting"?
Here is an argument to the exact contrary of your conclusion.
A displacement from the flight path is a function of acceleration normal to the flight path, and duration of the force causing the acceleration (the lift engendered by the gust). The lift engendered by the gust will be dependent upon the coefficient of lift, which itself is functional on the angle of attack. And those goings on are described by EAS, with two exceptions. One exception is the duration of the force, which, for a fixed gust domain, is less when TAS is higher. The other exception is the AoA in the gust, which is the angle of the result
ant vector of the velocity of the airplane and the gust velocity normal to the airplane velocity. (Let us ignore the difference between geometric angle of attack and effective angle of attack for the purposes of this discussion.)
For purposes of aerodynamics, gust velocities are taken to be EAS (see CS 25 for examples). Let us fix the EAS of the airplane and the gust. The resultant velocity vector will have a specific angle to the velocity vector of the airplane, and this is AoA. This will generate a specific lift, which will accelerate the airplane upwards, and of course this acceleration will change the airplane velocity vector, so the AoA will be continually changing during the encounter. The divergence from flight path is a function of this, which one can obtain by double-integrating the acceleration, which is functional upon the continually-changing AoA. The salient point here is that, for a given EAS of airplane and gust, and given initial AoA of the airplane, the displacement from initial FP is a function of the duration of the gust.
Now, for a given lateral gust size, if your TAS is higher, you will be through the gust faster, that is, less duration of exposure. That means, according to the reasoning above, your displacement will be less than if your TAS is lower.
This is the exact opposite of the situation you want us apparently to assent to: you claim the displacement is greater.
So which is right? Is the displacement greater, or less, for a higher TAS but all EAS's the same?
To summarise, I am not yet convinced that
Originally Posted by Honkozzie
we all (hopefully)know what that can result in...
.
BTW, if your "main point" is that weather avoidance is a good thing, I agree, for the paying passengers as well as the pilot. But weather avoidance is a more complicated issue than just not going where the red shows. Consider ice-particle icing, for example. That can ruin your day also.
PBL