Regarding Pierre sprey's claims about BVR and F-35

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basher54321

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Unread post14 Jun 2014, 22:00

uclass wrote:
johnwill wrote:Turn rate in a loop is zero at all times.

Depends which axis you're measuring turn rate in.



Isn't the nose rate still zero because the G is constant - as per the original question.
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uclass

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Unread post14 Jun 2014, 23:19

basher54321 wrote:
uclass wrote:
johnwill wrote:Turn rate in a loop is zero at all times.

Depends which axis you're measuring turn rate in.



Isn't the nose rate still zero because the G is constant - as per the original question.

That's not how g is measured. In level flight your g is 1.0. When falling it's zero.
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basher54321

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Unread post14 Jun 2014, 23:53

uclass wrote:That's not how g is measured. In level flight your g is 1.0. When falling it's zero.



hmmm - Specifically pitch acceleration is zero if G is constant - that's at any constant G turn. isn't that what Johns getting at?
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johnwill

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Unread post15 Jun 2014, 05:19

"Turn rate" is flight path heading change in a constant altitude turn. I'm just jabbing uclass a little bit because he mistakenly applied turn rate terminology to a loop, not exactly a constant altitude maneuver.
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basher54321

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Unread post15 Jun 2014, 12:13

He's probably thinking - yeah but my loops go all over the place :D
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quicksilver

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Unread post15 Jun 2014, 13:08

Sounds like engineers talking, not pilots.

'Plane of motion', and whatever rate of nose movement is being generated in a given plane of motion is fundamental to understanding aircraft performance in BFM.
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uclass

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Unread post15 Jun 2014, 20:42

johnwill wrote:"Turn rate" is flight path heading change in a constant altitude turn. I'm just jabbing uclass a little bit because he mistakenly applied turn rate terminology to a loop, not exactly a constant altitude maneuver.

That's true but I was sort of seeing it as a turn about a different axis. Probably not common terminology though.

I am right in thinking that g is 1.0 in level steady flight, or am I?????

Or if you fly an SR-71 at 90,000ft, does it reduce to 0.99g? :mrgreen: :mrgreen:
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cola

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Unread post15 Jun 2014, 21:15

uclass,
if you do the turn in a vertical plane using constant stick input, you don't have constant g, even if FCS/FADEC can keep the plane at constant speed.
If you vary stick input to keep g constant (on top of an already constant speed), you will get exactly the same turn rate throughout the entire turn, even in vertical plane.
Cheers, Cola
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quicksilver

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Unread post16 Jun 2014, 00:02

cola wrote: If you...keep g constant (on top of an already constant speed), you will get exactly the same turn rate throughout the entire turn, even in vertical plane.


Not so. You forget the effect of radial G.

If you view a constant G loop in cross section, it will look like an egg due to the effects of radial G.
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cola

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Unread post16 Jun 2014, 00:33

quicksilver wrote:If you view a constant G loop in cross section, it will look like an egg due to the effects of radial G.

Yes, but that's because your speed changes.
On constant g/speed (providing FCS/pilot can compensate for Earth's 1g), it still looks like a circle.
Cheers, Cola
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quicksilver

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Unread post16 Jun 2014, 02:20

cola wrote:
quicksilver wrote:If you view a constant G loop in cross section, it will look like an egg due to the effects of radial G.

Yes, but that's because your speed changes.
On constant g/speed (providing FCS/pilot can compensate for Earth's 1g), it still looks like a circle.


Riiight... :roll:
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count_to_10

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Unread post16 Jun 2014, 02:22

cola wrote:
quicksilver wrote:If you view a constant G loop in cross section, it will look like an egg due to the effects of radial G.

Yes, but that's because your speed changes.
On constant g/speed (providing FCS/pilot can compensate for Earth's 1g), it still looks like a circle.

Earth's 1g makes it look "egg shaped" even at constant velocity if you pull constant g's.
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Unread post16 Jun 2014, 03:56

Last time I looked this VULTURE RN FAA ACM info was no longer at URL below. The USN T-45C Goshawk training program for ACM has some good info and probably better graphics. I'll go there next....

Here is the USN Basics ACM PDF: https://www.cnatra.navy.mil/pubs/folder5/T45/P-1289.PDF

NOW the USN and RN FAA ACM Basic Maneuvers have been combined into one PDF with extra USN T-45C amendments & additions to the basics - 185 pages of ACM GOODNESS PDF now ATTACHED.
Vulture's Fleet Air Arm "Air Combat Manoeuvring"

"...2) Air combat takes place in a three dimensional environment and a pilot should appreciate the effect of gravity on his manoeuvring performance, and the inter-relationship of kinetic and potential energy. The manoeuvring envelope can be likened to the surface of an egg, with the pointed end uppermost. The turning rate (or pitch rate) of an aircraft is dependant on the radial 'G' as distinct from indicated 'G'. Thus when gravity is assisting the turn by providing an increment of radial 'G' the turning performance is enhanced and accounts for the pointed end of the ovoid. Figure 1 illustrates the indicated 'G' to radial 'G' relationship for a constant speed loop in the vertical plane.

3) When an aircraft is manoeuvring in the vertical plane the turning (or pitch) rate is increased when the lift vector is below the horizon, and vice versa. Figure 1 illustrates the idealised situation of a constant speed loop in the vertical plane whereas in practise, manoeuvring takes place in all three dimensions and the speed is rarely constant; the tendency being to accelerate in dives and to decelerate when climbing. For maximum turn rate, a pilot should always manoeuvre so that gravity is favourably affecting the thrust and lift vectors. Figure 2 shows the effect on three dimensional manoeuvring as the plane of the manoeuvre moves from the horizontal to the vertical ie. from a true circle to the most pointed ovoid shape. The concept of maximum performance manoeuvring within an ovoid forms the basis of the subsequent discussion on individual aircraft manoeuvring...."

Source: http://www.vulch.clara.co.uk/acm.html
Attachments
EffectGravityACM.gif
T-45CacmVertManeuverEGG.gif
ACM VULTURE & T-45C USN+AddsAmends.pdf
(4.11 MiB) Downloaded 646 times
A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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cola

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Unread post16 Jun 2014, 06:17

quicksilver wrote:Riiight... :roll:

Yes QS...riiight.
However, I see what confuses you, so add 'radial' to 'constant g' (as opposed to indicated) in my previous posts and there you go.
Cheers, Cola
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johnwill

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Unread post16 Jun 2014, 17:36

cola wrote:
quicksilver wrote:Riiight... :roll:

Yes QS...riiight.
However, I see what confuses you, so add 'radial' to 'constant g' (as opposed to indicated) in my previous posts and there you go.


QS confused? Not likely. Cola, you might want to reconsider that. There is confusion here, but it is on those who use "g" as acceleration, when in fact it means "load factor", or lift / weight.

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