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I´m sure having its large wing area perpendiculat to the velocity vecotr creates quite some drag.

Drag means force and force means acceleration.

Should be a good bit more then 1 g but how much is hard to say without haveing details.

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Tengu, the pilot would experience more than 1G. the drag force (going from laminar to turbulent, so the drag goes up to the square of the original drag) will drastically slow the aircraft down. that will impart an acceleration on the pilot and squeeze the aircraft towards him. the drastic slowing is probably greater than 9.81m/s^2, meaning it's probably more than 1G.

While not an expert on it, I can give you a educated guess. Those types of manuevers are not hi-G but, like previously mentioned, there is a good amount of g generated from the deceleration. How much is obviously decided upon on how fast the deceleration is & I don't know that answer. Flying at extreme AOA's does not generate G's by itself, just the G that is generated from the radial G in the turn itself (where his actual lift vector is pointed.) I don't know if that makes sense to you but hopefully it helps.

What I don't understand, and maybe its just not clicking, the little piece of flint in my brain isn't lighting.... Is how deacceleration would create positive G's on the pilot? (Force = Mass * Acceleration), right? In this case our net force is the [ (Drag of the A/Cs wings) + (Forward force already aquired from A/Cs forward velocity) ] and the Acceleration should be negative since the drag reacts in the opposite direction of the forward velocity right? Ugh! Im only confusing myself! :p

Polaris, welcome to the board btw!

-Aaron

Right now I wish I could use my hands to show you or at least draw it up for you - std fighter pilot.

Let me see if I can try to explain it (I'm not a tech major, just have a BS in a "fuzzy" degree, so you'll have to forgive if I don't use the exactly correct terminology.) Let's say you are in your hot sports car and you are going 120 mph down the road. Suddenly you see a car wreck in front of you and you hit the brakes. What will happen? You'll get thrown into your seatbelt (or window) in the direction the vehicle is traveling. Now in a jet it works the same way, except now I have AOA & drag to bleed down energy (velocity) instead of my wheel brakes. If I did a high AOA (alpha) maneuver the deceleration would push me towards the direction my jet is traveling, NOT where my nose is pointing. [Which in 90 degrees of AOA would be through my seat/rear end and would feel to me like normal g (except higher based on rate of deceleration.)]

i.e. traveling --> but nose pointing /\ if I were traveling --> but had my nose pointing \/ then the G would feel negative to me (going through my helmet)

Does that make sense?

Ah yes, so I understand then! The forces that would act on the pilot are 1 G straight down, thats constant, and then the ammount of G's created by the deacceleration of the drag of the maneuver, in the direction of the aircrafts velocity...

So in the video Calhoun describes, the F-22 is doing a back flip while maintaining forward velocity. So if we say the plane is heading exactly west and the ammount of area on the wings would create 4Gs of force (just using 4 as an example) then the pilot would feel 1G perpindicular to the earth and 4Gs parrallel to the west at all times during this maneuver! Thanks Smile

I understand now!

Physics is fun! Rolling Eyes

-Aaron

Enthusiast Joined: Apr 19, 2005 Posts: 80 Status: Offline

parrothead,

Quote:

I know the thrust vectoring nozzles are used to increase pitch response as well as control at low speeds and high alpha, but do they help at all with control about the roll axis? It shouldn't be too hard to program them for differential actuation, but do they actually perform in that capacity?

Pat1's post answered your first question. However, the answer to second question is no, they do not act independently.

Last edited by VprWzl on Apr 19, 2005 - 04:08 AM; edited 1 time in total

When I asked, they said the control surfaces are good enough and the flight control computer is smart enough to move the jet in roll and yaw so that the only thing the TV nozzles have to do is change the pitch. The pilots are able to put the jet wherever they want - the flight control computer just tells the controls surfaces/nozzles what to do and when to do it to get the jet to do what the pilot is commanding. Aaahhh, the beauty of fly-by-wire.

VprWzl wrote:

When I asked, they said the control surfaces are good enough and the flight control computer is smart enough to move the jet in roll and yaw so that the only thing the TV nozzles have to do is change the pitch. The pilots are able to put the jet wherever they want - the flight control computer just tells the controls surfaces/nozzles what to do and when to do it to get the jet to do what the pilot is commanding. Aaahhh, the beauty of fly by wire.

There's actually no such thing as a flight control computer on this aircraft. There are 3 VMS racks (vehicle management system) that act similar to a FLCC. Believe it or not, but its much simpler to work than a 16's FLCS in my experience.

Cool, thanks for the welcome, btw.

I'd like to be enlightened on flight control systems.

Polaris wrote:

Cool, thanks for the welcome, btw.

I'd like to be enlightened on flight control systems.

Very simple. A signal is sent from the force transducer that the stick sits on, down to each of the 3 VMS racks. It is recieved by a module that facilitates communications from other remote terminals. The information is passed to another module that handles all communication internal to the rack. These modules are called PICCs, Processor Interface Communication Controller or some such. The signal is then sent to the ADIO (Analog/Digital Input Output) which decides on the amount of dsurface deflection required to point the airplane where the pilot wants to go. The ADIO sends this signal over to one of the 5 AIMs (Actuator Interface Module) which interfaces directly to the actuators for surface positioning. Thats basically it in a nutshell. There are a few more things that get tossed in, such as IRS data, ADSS data, and signals from the gyros.

and all at 5000PSI. Glad I am not chasing leaks on that thing.

4100 psi

Rumors, gotta love um. Thanks for bringing the truth. Still 1100 more than most A/C. Does it use a new fluid?

Enthusiast Joined: Sep 09, 2004 Posts: 26 Status: Offline

What the thrust vectoring does is take work out of the horizontal stabilizers in the pitch regieme such that they're able to be used for more roll inputs at the high alpha, an F-15 has virtually no roll capacity at 30 degrees AoA but the Raptor has generous roll rate. As a consequence in an extreme turning environment the Raptor can roll and pull at the same time, an F-15 has to unload g some before it can roll to evade or chase.

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