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The A-10's AoA indicator is wrong.


Reticuli
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It reads too high in level flight, like 10 or 11 degrees. Wow. That's what you should have at low speed when landing with flaps. The real hog also has a limiter that prevents you from going past like 20-15 degrees, depending on the loudout weight programmed in. That doesnt' really bother me, or the fact I have to manually trim...which you shouldn't (the engine angle and SAS compensate enough most of the time). But the alpha indicator dial needs fixing. In fact, I don't think it's the dial but the flight model. Because the aircraft does begin to stall at just over 10 degrees additional alpha, or around 20. So it's not like it thinks it's 2-5 degrees in level flight. So a simple cockpit fix wouldn't be enough.

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Never heard of those special units. how does the pilot porcess the information that way?

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There are special ticks as you can see for several special AoA. For cruise flight, for approach, stall, etc.

The pilot is informed what AoA in units is suitable for certain flight mode.

By the way, though in Su-25 AoA gauge indicates in "degrees" it's not a real AoA in degrees so you can consider this "degree" as Russian "units'. :)

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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I'm getting a bit confused. So the AoA indicator in the Hog tells the pilot what AoA to fly, in not the current AoA of the plane?

 

Another thing, the real A-10 has Autotrim like the F-15?


Edited by pauldy

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I'm getting a bit confused. So the AoA indicator in the Hog tells the pilot what AoA to fly, in not the current AoA of the plane?

 

Another thing, the real A-10 has Autotrim like the F-15?

 

I do not understand what you mean. What for the real AoA of the plane for the pilot?

It could be in degrees, in radians, in litres.... it has no sense what units is used.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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The real hog also has a limiter that prevents you from going past like 20-15 degrees, depending on the loudout weight programmed in.

 

 

Where did you read about this feature for the Hog? Can you point me the FM page where it is meant?

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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OK, just to satisfy your curiosity (that as everyone knows killed the cat :) ) the quotation from the FM

The scale is calibrated from 0-30 arbitrary units... at 15.6 scale units a rectangular maximum range index, at 17.5 scale units a triangular max endurance index, at 20 scale units a T-shaped approach index....

etc, etc.

I think it's enough.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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The real hog has neither limiters nor automatic trim AFAIK - but I may as well re-check the -1 and see about the latter anyway.

 

What is DOES have, is WRITTEN prohibitions against stick throw, exceeding g, or AoA based on IAS/Payload/Weight, but AFAIK there's zero automation to prevent you from breaking your plane. Wanna pull 10g's? Go for it.

 

EDIT: I was just informed that SAS trims rudder/yaw for turn coordination.

 

 

It reads too high in level flight, like 10 or 11 degrees. Wow. That's what you should have at low speed when landing with flaps. The real hog also has a limiter that prevents you from going past like 20-15 degrees, depending on the loudout weight programmed in. That doesnt' really bother me, or the fact I have to manually trim...which you shouldn't (the engine angle and SAS compensate enough most of the time). But the alpha indicator dial needs fixing. In fact, I don't think it's the dial but the flight model. Because the aircraft does begin to stall at just over 10 degrees additional alpha, or around 20. So it's not like it thinks it's 2-5 degrees in level flight. So a simple cockpit fix wouldn't be enough.

Edited by GGTharos

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OK, just to satisfy your curiosity (that as everyone knows killed the cat :) ) the quotation from the FM

The scale is calibrated from 0-30 arbitrary units... at 15.6 scale units a rectangular maximum range index, at 17.5 scale units a triangular max endurance index, at 20 scale units a T-shaped approach index....

etc, etc.

I think it's enough.

Any chance you guys know what sends this information to the AOA gauge and why used "units" instead of degrees?

Does the lift transducer on the left wing does this (send info to the gauge) or is transducer only used for the leading edge slats operation?

 

pauldy:

Another thing, the real A-10 has Autotrim like the F-15?

Nether the A-10 nor the F-15 have automatic trim. Not even the F-16 nor the F-117 have automatic trim. All aircraft that I know about still required the pilot to trim them.

To whom it may concern,

I am an idiot, unfortunately for the world, I have a internet connection and a fondness for beer....apologies for that.

Thank you for you patience.

 

 

Many people don't want the truth, they want constant reassurance that whatever misconception/fallacies they believe in are true..

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AFAIK units are used because they take onto account additional factors and thus they better represent the AoA. You could actually make your units be equal to degrees, but then you have to also know that you're dealing with 'Corrected AoA' like you deal with 'Calibrated IAS'.

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But even the old low-tech A-10A needs little or no trim most of the time due to the angle of the engines, even with its more rudimentary SAS shot out...assuming the control surfaces and weight distribution are kosher. Just because it's there doesn't mean it's needed. It shouldn't pitch down like a normal aircraft when untrimmed manually and the CoG is right.

 

And the newer F-15's and all the F-16's & F-117's AFCS control the aircraft to 1g standard and near-zero alpha, which effectively is "autotrimming" but they still have trims. Ditto with the Hornet, Superhornet, Raptor, and JSF. Even the last versions of the Tomcat did. In the case of the viper, the pitch trim is used to increase the flight computer's demand AoA at lower speeds. Otherwise there's little point in touching it with normal operation. The early F-15A/B/C/D needed normal trimming. You cannot pilot an F-117 without that AFCS, by the way, which itself cannot work without either attitude-command, g-command, alpha-command, or a combination.

 

And all Airbus 300 series and the newest Boeing airliners essentially "autotrim". The former also being hard limited, while the latter is soft that you can override with extra input force. But I digress. Again, they all have trims available but that's mostly for compensating for engine loss or other malfunction.

 

On the A-10's limits, I may have read that wrong. I thought the site used the term limiter, but they may have meant written limits. I assumed the SAS was g and alpha limiting from the way it was termed.

 

On the indicator: so it sounds like it's more a monochrome callibrated stall threshold indicator than a normal AoA dial. There were a couple compaints on the forum previously when I searched and this didn't appear mentioned. Clearly from the other posts here, this needed repeat for those of us who skimmed over that paragraph in the manual. Thanks!


Edited by Reticuli

X65 and X52, Glide, Winx3D, and GlovePIE Profiles http://library.avsim.net/search.php?SearchTerm=reticuli&CatID=miscmisc

 

http://library.avsim.net/register.php

 

X52 + Silicone Grease = JOY stick

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But the A-10 needs little or no trim most of the time due to the angle of the engines, even with the SAS shot out...assuming the control surfaces and weight distribution are kosher. Just because it's there doesn't mean it's needed. It shouldn't pitch down like a normal aircraft when untrimmed manually and the CoG is right.

 

My -1 says otherwise. Not ONLY do you have to manually trim, but you have to be careful when disengaging the autopilot to ensure it hasn't trimmed out into something less than safe. If the SAS is shot out, there are a LOT of limitations on flight, and the very FIRST thing you check is if you're trimmed right - that's after the huge nasty roller coaster ride is put under control when you switch to manual reversion.

 

And the newer F-15's and all the F-16's & F-117's AFCS control the aircraft to 1g standard and near-zero alpha, which effectively is "autotrimming" but they still have trims. Ditto with the Hornet, Superhornet, Raptor, and JSF. Even the last versions of the Tomcat did. In the case of the viper, the pitch trim is used to increase the flight computer's demand AoA at lower speeds. Otherwise there's little point in touching it with normal operation. The early F-15A/B/C/D needed normal trimming.
Nothing trims to 'near zero alpha'. There's no such flight condition at one gee ;)

F-15's never needed much trimming. The design of the SAS on those is public.

The only F-15 model that may use FBW is F-15E or later, but I don't recall if it does. Earlier F-15's all use the Control Augmentation system which, while not really an FBW, certain can and will do interesting things for you. I believe the MiG-29 uses a similar system.

F-16s I don't know much about except that they do indeed get trimmed in-flight by their pilots. There's lots of reasons: Airframes get slightly bent over time, and no two aircraft will trim the same for example - same for F-15's.

 

 

And all Airbus 300 series and the newest Boeing airliners essentially "autotrim". The former also being hard limited, while the latter is soft that you can override with extra input force. But I digress. Again, they all have trims available but that's mostly for compensating for engine loss or other malfunction.
The Airbus is flown by autopilot - when it isn't you get as much carefree handling as safely possible. On the other hand, I have no idea what the design of those is - I've no doubt that you can take a modern FBW aircraft, point it in a direction, and it'll fly there.

 

On the A-10's limits, I may have read that wrong. I thought the site used the term limiter, but they may have meant written limits. I assumed the SAS was g and alpha limiting from the way it was termed.
There are graphs which indicate safe flight limitation, as well as stated g limitations lateral and longitudinal for given payloads and weights (some payloads might limit you more than the weight would). These limits are enforced by the meat stick actuator only.

 

On the indicator: so it sounds like it's more a monochrome callibrated stall threshold indicator than a normal AoA dial. There were a couple compaints on the forum previously when I searched and this didn't appear mentioned. Clearly from the other posts here, this needed repeat for those of us who skimmed over that paragraph in the manual. Thanks!
No, that IS a normal AoA dial :)

It is this way because there's more factors to AoA/safe flight than just the difference between your flight path and the nose.

 

For example you're more likely to stall out in a bank when flying slow - then again, I'm not certain that the AoA computations take this into account, I don't have this information.

 

Also keep in mind that the units are arbitrary - as mentioned before, the only important thing to the pilot is 'what AoA am I allowed full authority at' and so on down the line.

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I used to play flight sims like you, but then I took a slammer to the knee - Yoda

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Reticuli

But even the old low-tech A-10A needs little or no trim most of the time due to the angle of the engines, even with its more rudimentary SAS shot out...assuming the control surfaces and weight distribution are kosher. Just because it's there doesn't mean it's needed. It shouldn't pitch down like a normal aircraft when untrimmed manually and the CoG is right.

 

And the newer F-15's and all the F-16's & F-117's AFCS control the aircraft to 1g standard and near-zero alpha, which effectively is "autotrimming" but they still have trims. Ditto with the Hornet, Superhornet, Raptor, and JSF. Even the last versions of the Tomcat did. In the case of the viper, the pitch trim is used to increase the flight computer's demand AoA at lower speeds. Otherwise there's little point in touching it with normal operation. The early F-15A/B/C/D needed normal trimming. You cannot pilot an F-117 without that AFCS, by the way, which itself cannot work without either attitude-command, g-command, alpha-command, or a combination.

 

And all Airbus 300 series and the newest Boeing airliners essentially "autotrim". The former also being hard limited, while the latter is soft that you can override with extra input force. But I digress. Again, they all have trims available but that's mostly for compensating for engine loss or other malfunction.

 

On the A-10's limits, I may have read that wrong. I thought the site used the term limiter, but they may have meant written limits. I assumed the SAS was g and alpha limiting from the way it was termed.

 

On the indicator: so it sounds like it's more a monochrome callibrated stall threshold indicator than a normal AoA dial. There were a couple compaints on the forum previously when I searched and this didn't appear mentioned. Clearly from the other posts here, this needed repeat for those of us who skimmed over that paragraph in the manual. Thanks!

06-17-2009 05:01 PM

 

First, I never heard of this terminology after working on the F-16 since 1997, what is a "SAS" and a "AFCS" Nether the F-16 nor the F-117 have this.

 

The F-16 flight control do correct to one g of flight AFAIK, but you can do many things at one G (climb, dive, roll, yaw) So I ask you; How do you stay on course without trimming?

All the fly by wire (FBW) aircraft I have work on need to be trimmed and I could see that in the cockpit every time, if not; Why non of the trim where ever centered?

 

The Newer F-15, are you referring to the F-15K and SG? AFAIK, all F-15 have the same flight control system and non are FBW. Granted I have never work on F-15, but I have to know general information on them and I do not see them getting FBW, to much money and time for conversions. They do have Hydromechanical computers (ARI, PRCA)for a "semi-fly-by-wired control system"

http://www.f-15estrikeeagle.com/navigation/index_technology.htm

Meaning they do some automatic controls but still have a mechanical connection to the Stick as oppose to the F-16,and F-117 which do not.

 

Also, nether the F-16 nor the F-117 fly at "zero alpha" It is impossible with many jet fighter because of the aerodynamic designs. Look at any HUD video on the F-16, Flight path marker will always point to a different place than the bore sight cross during flight.

 

In term of the AOA indicator, I was looking around for more info on why use a unit of measurement instead of just degrees, I have not found it yet but I did find this informative website, have not read the whole thing, but seems interesting enough.

http://www.av8n.com/how/htm/aoa.html


Edited by mvsgas

To whom it may concern,

I am an idiot, unfortunately for the world, I have a internet connection and a fondness for beer....apologies for that.

Thank you for you patience.

 

 

Many people don't want the truth, they want constant reassurance that whatever misconception/fallacies they believe in are true..

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2 msvgas

Please explain me why for I must know EXACT angle IN DEGREES if I have all directions relative to UNITS? There is no difference indeed.

I have only one idea why units but not degrees are used - if we use units less than 1 deg it is more accurate to point certain angle. Instead of 12.72 grad I can use 22 or 22.5 units.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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2 msvgas

Please explain me why for I must know EXACT angle IN DEGREES if I have all directions relative to UNITS? There is no difference indeed.

I have only one idea why units but not degrees are used - if we use units less than 1 deg it is more accurate to point certain angle. Instead of 12.72 grad I can use 22 or 22.5 units.

I have no Idea why some use degrees and some don't, I do not why or if you need to know exact degrees, just wandering about the semantic. I not saying one way is better than another just trying to understand the difference between them both and the benefits.

 

P.S.

The only reason I ask you Yo-Yo about the gauge is mere mechanic curiosity. You are very knowledgeable on the KA-50 and I was wandering if you knew what send that information to the AOA gauge.


Edited by mvsgas

To whom it may concern,

I am an idiot, unfortunately for the world, I have a internet connection and a fondness for beer....apologies for that.

Thank you for you patience.

 

 

Many people don't want the truth, they want constant reassurance that whatever misconception/fallacies they believe in are true..

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  • 7 years later...

AOA.docx?dl=0

It's not degrees. It is special units:

AoA[units] = 0.7728*AoA[Degrees] + 12.22[/quote

 

Where you have this formel source ?

 

I have a diferent math formel as you have.

True AOA(UNITS)=TRUE AOA(DEGREES)+8.93/1.025

B+NHweda8r1NAAAAAElFTkSuQmCC

 

B+NHweda8r1NAAAAAElFTkSuQmCCSource is P-1259 (REV. 10-99) PAT Page 9-5

 

a good test pilot is always in training

Thomas


Edited by Thomas Loeffelmann
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My -1 says otherwise. Not ONLY do you have to manually trim, but you have to be careful when disengaging the autopilot to ensure it hasn't trimmed out into something less than safe. If the SAS is shot out, there are a LOT of limitations on flight, and the very FIRST thing you check is if you're trimmed right - that's after the huge nasty roller coaster ride is put under control when you switch to manual reversion.

 

Nothing trims to 'near zero alpha'. There's no such flight condition at one gee ;)

F-15's never needed much trimming. The design of the SAS on those is public.

The only F-15 model that may use FBW is F-15E or later, but I don't recall if it does. Earlier F-15's all use the Control Augmentation system which, while not really an FBW, certain can and will do interesting things for you. I believe the MiG-29 uses a similar system.

F-16s I don't know much about except that they do indeed get trimmed in-flight by their pilots. There's lots of reasons: Airframes get slightly bent over time, and no two aircraft will trim the same for example - same for F-15's.

 

 

The Airbus is flown by autopilot - when it isn't you get as much carefree handling as safely possible. On the other hand, I have no idea what the design of those is - I've no doubt that you can take a modern FBW aircraft, point it in a direction, and it'll fly there.

 

There are graphs which indicate safe flight limitation, as well as stated g limitations lateral and longitudinal for given payloads and weights (some payloads might limit you more than the weight would). These limits are enforced by the meat stick actuator only.

 

No, that IS a normal AoA dial :)

It is this way because there's more factors to AoA/safe flight than just the difference between your flight path and the nose.

 

For example you're more likely to stall out in a bank when flying slow - then again, I'm not certain that the AoA computations take this into account, I don't have this information.

 

Also keep in mind that the units are arbitrary - as mentioned before, the only important thing to the pilot is 'what AoA am I allowed full authority at' and so on down the line.

 

Well, to be fair, just because it's an airliner doesn't mean its meant to be flown on autopilot all the time. I've flown many trips by hand.

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AOA.docx?dl=0
It's not degrees. It is special units:

AoA[units] = 0.7728*AoA[Degrees] + 12.22[/quote

 

Where you have this formel source ?

 

I have a diferent math formel as you have.

True AOA(UNITS)=TRUE AOA(DEGREES)+8.93/1.025

B+NHweda8r1NAAAAAElFTkSuQmCC

 

B+NHweda8r1NAAAAAElFTkSuQmCCSource is P-1259 (REV. 10-99) PAT Page 9-5

 

a good test pilot is always in training

Thomas

Both are correct. The difference is in the scale of the instruments. The first is formula to convert degrees to a 45 unit scale. The second is to convert degrees to a 30 unit scale.

 

It's no surprise your reference is a US Navy document. The US Navy has historically used 30 degree scales in it's aircraft. With the face rotated so that the landing approach AOA is at 3 o'clock.

 

The first formula is for a 45 unit indicator which is used in the F-15. The US Air Force has had less standardization in it's AOA displays than the US Navy historically. It was a very hot topic on what and how it should be presented during the time the F-15, F-16 and A-10 were designed. So it's not unusual that all the systems vary a bit.

 

There is a nice NASA document about the history of AOA. While it doesn't say directly why the armed forces adopted the unit of AOA. It seems to imply that displaying units provides the pilot with pertinent information in the easiest to read fashion. Hence the Navy's 30 degree 3 o'clock AOA gauges.

 

Here's a link to that NASA doc.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011419.pdf

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AOA.docx?dl=0

Both are correct. The difference is in the scale of the instruments. The first is formula to convert degrees to a 45 unit scale. The second is to convert degrees to a 30 unit scale.

 

It's no surprise your reference is a US Navy document. The US Navy has historically used 30 degree scales in it's aircraft. With the face rotated so that the landing approach AOA is at 3 o'clock.

 

The first formula is for a 45 unit indicator which is used in the F-15. The US Air Force has had less standardization in it's AOA displays than the US Navy historically. It was a very hot topic on what and how it should be presented during the time the F-15, F-16 and A-10 were designed. So it's not unusual that all the systems vary a bit.

 

There is a nice NASA document about the history of AOA. While it doesn't say directly why the armed forces adopted the unit of AOA. It seems to imply that displaying units provides the pilot with pertinent information in the easiest to read fashion. Hence the Navy's 30 degree 3 o'clock AOA gauges.

 

Here's a link to that NASA doc.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011419.pdf

 

Thank you for the information, this make sens to me. I know the NASA dokument as well.

 

Is good to know for my project and unterstand, the NAVY and Air Force different procedures.

 

Thank you very much.

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