AOA indexer

Currently on the AOA indexer at landing approach the lowest symbol ^ shows that you have to increase speed (and lower AOA). I think in reality it works exactly as in US aircraft, that is exactly in reverse.

The indexer as it is now can't even be called an "AOA indexer". It is more like a speed indexer, the ^ symbol shows that you have to increase something - what you have to increase here to achieve correct conditions is speed, which means to actually lower the AOA.

http://forums.airforce.ru/matchast/4131-reestr-su-33-a-16/

Here on post #305 the MiG-29 AOA indexer is described, it seems like on Su-33 it is principially similar. The ^ symbol here clearly means the AOA must be increased.

its still an aoa indexer. works the same way but the symbols are reversed. its still slow down until donut and hold it (the auto throttle is helpful here as it is on US aircraft. just hold idle until on speed when on final and engage when you have the donut) but its the same idea as any other.

gets you on speed or more precisely on aoa no matter what your current weight is. I point people to fly the aoa instead of a speed whenever I get asked what landing speed to use as this will always be more accurate.

a landing speed will change by weight. but your landing aoa is always the same

I always thought of it as the light was where your speed was and ignored the arrow. bottom light? too slow etc

sorry if I'm missing something but I'm not entirely sure what you are getting at with this post?

works the same way but the symbols are reversed.

Which is not correct as the link I provided clearly shows. Have you even bothered to read that?

About the rest of your post, many thanks for the free lesson but I already knew all that like 2 decades ago ;)

Which is not correct as the link I provided clearly shows. Have you even bothered to read that?

 

About the rest of your post, many thanks for the free lesson but I already knew all that like 2 decades ago ;)

once again.... wasnt sure what you made this post for. one of the reasons I asked. don't see anything specific being asked. but if the thread is here anyway and it was on topic, I added stuff that could help others that read since many people dont think of it that way or just ignore the thing entirely. its for anyone to learn from. not trying to say you dont know things. im putting it there for those who dont know.

when I was referring to different symbols I wasn't talking about the 29-33. not sure why it was in my head at the time but was thinking of a ga system another pilot friend was talking to me about

unfortunately most of the post you refer to talks about the ship board lamps it seems like. which are a little useless since I personally cant see them from farther than +/-.3nm thanks to LOD

once again.... no idea what you made this post for.

I made the post because currently in simulator the AOA indexer lights ARE REVERSED, that is they don't work correctly (don't work like in reality).

Quick example: currently in simulator when the upper light on the indexer burns, actually the lower light on the indexer should burn instead. That is, it should do that in order to work like it does on the real aircraft. Just read the link I provided where the REAL WORLD system is described.

Please return to discuss after reading&understanding the description in the link provided.

I made the post because currently in simulator the AOA indexer lights ARE REVERSED, that is they don't work correctly (don't work like in reality)...

Is the complaint that the colors are reversed or that there are colored up/down arrows that are reversed? Or both? The instrument we have in the sim's cockpit functions much the same, though with different indicators, as the one you linked.

In your link, the lights indicate whether you need to increase your AoA or reduce it. Using those lights, if you increase your AoA, you will have to decrease power to maintain the same 1 G flight path. If you decrease your AoA, you will have to increase power to maintain that flight path. What we have in our pit presents differently than what is shown in your MiG-29 link. But the effect of following either is same--an increase or decrease of power to maintain the required AoA for the 1G flight path. So I guess the real question is: Have you seen anything in the real world Su-33 pit to indicate that what we have differs from the real pit?

^^^ Colours on the AOA indexer in simulator are correct: lowest light is red, uppermost light is yellow. However the lowest light has a ^ symbol on it. The logic behind that is that it tells the pilot that he must increase something. Since this is called an AOA indexer, this means when the red ^ light burns the pilot must increase AOA to be "on speed". But in simulator in this case the red ^ light burning means that the pilot actually has to DECREASE the AOA (and it does that by increasing speed).

Have you seen anything in the real world Su-33 pit to indicate that what we have differs from the real pit?

No I haven't but this is logics and common sense. On all US aircraft of all times and the naval MiG-29 when the lowest symbol ^ burns, this means the pilot must increase AOA to be "on speed". Now how likely is the Su-33 to have that REVERSED? Imagine this dialogue:

One MiG engineer: "Our Su-33 naval pilots are used with the AOA indexer to function in a certain way. How about on the new naval MiGs we make that to work in reverse? You know, just for fun". Another engineer "This makes perfect sense, great idea!"

Long story short: on Su-33 the AOA indexer should work just like in any US aircraft of any era.

One MiG engineer: "Our Su-33 naval pilots are used with the AOA indexer to function in a certain way. How about on the new naval MiGs we make that to work in reverse? You know, just for fun". Another engineer "This makes perfect sense, great idea!"...

:) Logic, unfortunately, has little to do with it. Two different design bureaus. If all decisions were determined by logic, the Su-27's FBW system would not have an overriding program designed to make it function like an aircraft with positive stability. Without it, the FBW system would behave much more like that of the F-15. But it's there, anyway, because that's how those making the decisions wanted it.

You could very well be right. OTOH, you could also be wrong. Which was why I was asking if you'd seen some indication of something different in the real pit.

^^^ Let's looks at it differently, let's pretend we don't know anything about other aircraft and all we have is Su-33. Right now in simulator on the AOA indexer the lowest red light has a ^ symbol on it that clearly tells the pilot he has to increase something. Now you tell me what the pilot has to increase and how you see the logic of it.

Let's say the current implementation in simulator is correct. Now you please describe how you see the logic behind it.

^^^ Let's looks at it differently, let's pretend we don't know anything about other aircraft and all we have is Su-33. Right now in simulator on the AOA indexer the lowest red light has a ^ symbol on it that clearly tells the pilot he has to increase something. Now you tell me what the pilot has to increase and how you see the logic of it.

 

Let's say the current implementation in simulator is correct. Now you please describe how you see the logic behind it.

Increase your airspeed (power setting) to lower your AoA. Every AoA for a particular weight has its required airspeed in 1 G flight.

Let's say the current implementation in simulator is correct. Now you please describe how you see the logic behind it.

Ivan has not had a good day, for 9 hours he's been stuck in the cockpit doing a ferry flight. When he finally reaches the carrier it's dark and he's straining to stay focused on the landing. His attention lapses for a few seconds and when his eyes return to the HUD the little red arrow is lit up. He quickly advances the throttles to increase power and get back on glide slope.

Seems like a pretty logical solution to me. Do we even know what Sukhoi calls it? Maybe it's an on-speed indicator and not an AoA indexer.

Do we even know what Sukhoi calls it? Maybe it's an on-speed indicator and not an AoA indexer.

This makes sense, and that's what I was trying to say. The current AOA indicator in simulator is obviously controlled by the AOA value. However, because the red ^ means you have to increase speed, this is actually not an AOA indexer. It is rather a speed indexer or if you like a speed director.

This makes sense, and that's what I was trying to say. The current AOA indicator in simulator is obviously controlled by the AOA value. However, because the red ^ means you have to increase speed, this is actually not an AOA indexer. It is rather a speed indexer or if you like a speed director.

Unfortunately, Vladinsky's story doesn't make as much sense as it seems at first blush. The up arrow only tells you to increase airspeed to reduce your AoA. It makes no difference whether or not you are on glideslope. In fact, it works the same in straight and level flight or even in a climb. All it's helping you to correct is your AoA. It's putting you at the airspeed required by the landing AoA.

The AoA and aircraft weight dictate the necessary airspeed to maintain that AoA as I'm sure you know. If you start going too fast, the down arrow appears indicating that you need to slow down. Not doing so will reduce you AoA. If you start going too slow, the red up arrow appears indicating that you need to speed up. Not doing so means that your AoA will continue to be too high. So, yes, in a sense, it's a speed indexer. But being at the right speed for your weight means that you'll be at the correct landing AoA.

So, if your head is up as it should be during a landing, you have, in your line of sight, the HUD displaying the director circle along with the ILS deviation circle with the indexer just to the left of the HUD telling you whether to increase your airspeed, decrease your airspeed, or hold your current airspeed to maintain the correct landing AoA for when you slam onto the deck.

EDIT: So, to revise Vladinsky's story:

Ivan has not had a good day, for 9 hours he's been stuck in the cockpit doing a ferry flight. When he finally reaches the carrier it's dark and he's straining to stay focused on the landing. His attention lapses for a few seconds and when his eyes return to the HUD, he's relieved to see that the large and small circles are still centered. But the little red arrow to the left of the HUD is lit up. He nudges the throttles forward to increase power so that he doesn't tail strike when he slams onto the deck.

It was more of a he's below glideslope because the speed is too low and the sinkrate is getting dangerously high kind of scenario I was imagining.

It was more of a he's below glideslope because the speed is too low and the sinkrate is getting dangerously high kind of scenario I was imagining.

Yes, I know. :) That's how I understood your expalnation. Then I thought about it and realized that those lights have nothing to do with sinkrate because they work the same way in a climb and/or level flight. They only direct you to the right airspeed for the correct AoA given your landing weight.

I need to spend more time in this pit comparing enroute and landing modes. Things seem slightly different than in the -27.

:) Logic, unfortunately, has little to do with it. Two different design bureaus. If all decisions were determined by logic, the Su-27's FBW system would not have an overriding program designed to make it function like an aircraft with positive stability. Without it, the FBW system would behave much more like that of the F-15. But it's there, anyway, because that's how those making the decisions wanted it.

As you probably know, the Su-27 flight control system can function in the following modes:

1. Takeoff and landing mode - position of the horizontal stabilizer is a function of stick position and pitch rate of the aircraft.

2. Flight mode - position of the horizontal stabilizer is a function of stick position, pitch rate of the aircraft and G.

3. "Rigid connection" mode - this is the exact name of it in Russian. In this mode position of the horizontal stabilizer is a function of stick position only.

This is all from the flight manual of the real aircraft, it is not "my opinion".

What you are referring to as an "overriding program" is the Rigid connection mode (the ЖEСTК СВЯЗЬ switch). The purpose of this mode is to give the pilot an elementary way to control the aircraft if, despite the multiple redundancy built into the system for whatever reason the flight control system goes completely nuts. Who knows, maybe a bullet goes right through it.

In this Rigid connection mode, where the position of the horizontal stabilizer is directly proportional with stick position, flight is still possible because the Su-27 is not a truly unstable aircraft. In fact the aircraft has slightly positive, close to neutral stability.

If an aircraft has positive or negative stability is determined by the position of the center of pressure of the lifting surfaces in relation to the center of gravity of the aircraft. So NO, you don't change the aircraft from negative stability to positive stability with a switch. Positive or negative stability is an aerodynamic property of the aircraft, you can't change that with a switch.

If the F-16 had an Rigid connection mode, switching it you would lose control of the aircraft in seconds (or less). That is because, unlike the Su-27, the longitudinal static stability of the F-16 is waaaaaaay negative. You can't fly that aircraft without computer aid.

In Su-27, flying in Rigid connection mode is not allowed at speeds greater than 600Km/h and AOA greater than 10 deg (check real flight manual, emergency procedures chapter). That is, because increasing the AOA above 10 deg, the combined center of pressure of the wing and the LERX naturally will move forward, making the aircraft first neutral then statically unstable (negative stability). Control of the aircraft will most likely be lost. The simulator might differ from that.

The main point is: flying an aircraft with negative stability in Rigid connection mode is not possible. It is possible on Su-27 because it has slightly positive stability.

If all decisions were determined by logic, the Su-27's FBW system would not have an overriding program designed to make it function like an aircraft with positive stability. But it's there, anyway, because that's how those making the decisions wanted it.

The inclusion of the Rigid connection mode was a sane decision for the safety of the pilot and the aircraft. If that was a logical or not-so-logical decision I'll let you judge.

^^^ Let's looks at it differently, let's pretend we don't know anything about other aircraft and all we have is Su-33. Right now in simulator on the AOA indexer the lowest red light has a ^ symbol on it that clearly tells the pilot he has to increase something. Now you tell me what the pilot has to increase and how you see the logic of it.

 

Let's say the current implementation in simulator is correct. Now you please describe how you see the logic behind it.

Logic I see is "You are too low, get up in the glide path" or "Your nose is too low, raise it"

Aoa indexer is about AOA not the glidepath. The AOA indexer tells you if you are fast or slow. It stops you having to work out your approach speed for the weight of the Aircraft .

I could fly on speed green donut but be below the glidepath all the way to touchdown.

Sent from my SM-G955U using Tapatalk

Aoa indexer is about AOA not the glidepath. The AOA indexer tells you if you are fast or slow. It stops you having to work out your approach speed for the weight of the Aircraft .

 

I could fly on speed green donut but be below the glidepath all the way to touchdown.

Throttle controls your altitude, stick controls your speed.

So where it places you then?

When you hit in Su-33 a auto-throttle for landing, you only use stick.

So where it places you?

On carrier landings your glide path as your speed are both as important.

Throttle controls your altitude, stick controls your speed.

So where it places you then?

 

When you hit in Su-33 a auto-throttle for landing, you only use stick.

So where it places you?

 

On carrier landings your glide path as your speed are both as important.

Fighter Pilots dont use the autothrottle where I come from. We fly the Aircraft down the glidepath and the indexer tells us if we are fast or slow and we adjust the throttle to correct our AOA.

Sent from my SM-G955U using Tapatalk

F18 Navy Pilot quote about stick and throttle control:

In the hornet I typically nudged the stick forward to start my descent once I started my turn from the abeam point (at the 180). But that was it after that it was all throttle and the stick was never considered for glideslope.

 

To do otherwise was to start a bad habit that would get you washed out of the program eventually. It was as notorious as spotting the deck. Seasoned LSOs could tell when pilots were spotting the deck (using the hud to aim the plane to the point of landing) and once they saw enough of it from a given pilot, that pilot was on a COD back to the FRS for remedial training and one more chance at keeping his job.

 

It was even easier to see when pilots were using the stick to control glideslope, not only could an experience LSO see the nose movement but they would see the AOA repeater in the nosewheel confirming the behavior. This too was another way pilots eventually washed out.

 

If you are using the stick and throttle to maintain glideslope you are doing it wrong, period regardless of platform. The stick is used for alignment to centerline and maintaining a constant AOA. That is what the pilots are doing in the videos when moving the stick, they are trying to keep that green donut lit and rock steady on the AOA indicator while using the throttle to maintain glideslope by keeping the meatball lined up with the datum lights. That's how it works, period.

F18 Navy Pilot quote about stick and throttle control:

Excellent info, this has been a real issue for me trying to understand the whole process of carrier landing.

• To keep the AOA indexer donut green, do you use throttle, do you change Angle of attack with stick or do you use both.
  
• I take it is the same procedure for standard ILS landing on carriers and runways, but instead of following meatball, you are following the ILS beam.
  

So answer is:

1. Set your required AOA with stick before line up with carrier and maintain.
   
2. Adjust only throttle to to stay on glideslope with meatball centered with datum lights.
   

Thank you so much

Regards, Ian.

As you probably know, the Su-27 flight control system can function in the following modes:

 

1. Takeoff and landing mode - position of the horizontal stabilizer is a function of stick position and pitch rate of the aircraft.

 

2. Flight mode - position of the horizontal stabilizer is a function of stick position, pitch rate of the aircraft and G.

 

3. "Rigid connection" mode - this is the exact name of it in Russian. In this mode position of the horizontal stabilizer is a function of stick position only.

 

This is all from the flight manual of the real aircraft, it is not "my opinion".

 

What you are referring to as an "overriding program" is the Rigid connection mode (the ЖEСTК СВЯЗЬ switch). The purpose of this mode is to give the pilot an elementary way to control the aircraft if, despite the multiple redundancy built into the system for whatever reason the flight control system goes completely nuts. Who knows, maybe a bullet goes right through it.

I think all he's actually referring to is that the Su-27's FCS is set up to mimic the behaviour of a 'normal' aircraft (with positive stability, and where the only 'FCS' is the pilot) in that if you speed up, the nose comes up & you climb, if you slow down the nose will drop. ( Presumably you've noticed how much more the pilot has to trim in the Su-27 when compared to the F-15 (?) )

This is the philosophical difference between the two design bureaus he was alluding to - in the F-15 the FCS takes care of trimming, in the Su-27 the pilot takes care of trimming. It's not about logic, it's about design bureau preferences, so your One MiG engineer: "Our Su-33 naval pilots are used with the AOA indexer to function in a certain way. How about on the new naval MiGs we make that to work in reverse? You know, just for fun". Another engineer "This makes perfect sense, great idea!"... might make sense to you, but is no guarantee that two design bureaus will arrive at the same response to a problem.

I think all he's actually referring to is that the Su-27's FCS is set up to mimic the behaviour of a 'normal' aircraft (with positive stability, and where the only 'FCS' is the pilot) in that if you speed up, the nose comes up & you climb, if you slow down the nose will drop. ( Presumably you've noticed how much more the pilot has to trim in the Su-27 when compared to the F-15 (?) )

:doh:

You are probably right, he was talking about "positive stability with speed" and I thought he was talking about "positive stability on G" !!!!!!!

might make sense to you, but is no guarantee that two design bureaus will arrive at the same response to a problem.

Have you thought that the first operational pilots on new naval MiG-29 are actually the most experienced former Su-33 pilots?

Imagine the naval MiG-29 landing on carrier at night. It is flown by a very experienced pilot who has flown Su-33 for 10 years. When he is really close to the ship with like 2-3 seconds left, suddenly a light burns on the AOA indexer, when a moment ago all seemed fine. In the stress of the moment his mind involuntarily switches back to the habit aquired during years and years of practice flying the Su-33, he makes the wrong actions that leads to accident.

This is an important indicator for carrier landing approach and is used under high stress conditions. A hypothesis of CONTINUITY from Su-33 to MiG-29 in how the indicator should be interpreted is A LOT more plausible than discontinuity. Who manufactures the aircraft makes no difference whatsoever, they implement the instrumentation like the customer wants.

I am saying that fully aware that there is the possibility that the way the indicator works on MiG-29 was indeed changed from how it worked on Su-33. If that is indeed the case and the indicator in simulator works correctly, all I can say is that I am more than surprised and I really don't get it.

 

You are probably right, he was talking about "positive stability with speed" and I thought he was talking about "positive stability on G" !!!!!!!

I decided to continue scrolling down the thread as I was formulating my reply and saw that Weta got here before I did. Thank you for taking the time, though, to respond in length.