Using "throttle for GS and stick for AOA" when landing - Page 21 - ED Forums
 


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Old 03-09-2018, 05:07 PM   #201
ttaylor0024
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Quote:
Originally Posted by sc_neo View Post
So; i was not sure whether those changing indexer lights (donut) where indicating ''angle of attack'' or whether they were about the correct true airspeed that the aircraft should fly down the GS and eventually touch down at.
We will ignore TAS here, it varies quite substantially depending on atmospheric conditions and altitude, etc. The only airspeed that really matters to the airframe itself is IAS, as that's what is read out and is the direct indicator of how many molecules of air the wing is seeing at that given instance of time. The doughnut is AOA.

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Originally Posted by sc_neo View Post
Now, if i am not mistaken: the AoA indexer lights really simply measure/indicate only AoA, but AoA is of course the COMBINATION of correct approach angle of the airfoils (as in degrees to the horizon) AND a specific true airspeed for a specific aircraft. Now, if i am not completely off in my physics here, AoA changes with different true airspeeds at the same angle of the airfoils in relation to the horizon and vice versa. If i keep that angle of the airfoils to the horizon rock steady but increase true airspeed, AoA decreases for instance. If i decrease true airspeed and start to descend the airflow comes not straight and level anymore, but comes from foward below thus inceasing AoA.
AOA is explicitly the angle between the chord like and the relative wind, and has nothing to do with airspeed. I can be at 300kts at 15* AOA, or 20kts at 15* AOA. If you're flying level, the relative wind is essentially coming from the horizon level in front of you. While flying level, if you increase your airspeed and maintain level flight, AOA decreases as you have to pitch down in order to reduce the extra lift from increasing your IAS. Without pitching down (decreasing AOA) you will start a climb, as lift is a function of IAS (density and velocity combined) and the coefficient of lift, and the coefficient of lift is essentially for our discussion AOA.


Now lets dissect this into an approach configuration.

If you start a descent by pulling power while on-speed AOA WITHOUT decreasing your pitch angle (you'd actually have to continue to pull back on the stick), you will have a higher AOA (green slow chevron).

If you have the aircraft trimmed on-speed AOA and pull some power back and do not pull back on the stick, the aircraft will naturally want to keep the trimmed AOA and maintain on-speed (the hornet's FCS does this, and even non-FBW aircraft will want to stay at whatever AOA you have it trimmed for, even in a skyhawk).

If you start a level turn you will have to ADD power in order to maintain level flight while on-speed. This is because while turning your lift vector gets cut in two- the horizontal and vertical component. So only the vertical component will be counteracting your weight, so it would have to increase in order to maintain level flight, and doing so would require a power addition in order to increase your total lift vector enough to increase the vertical component enough to keep you level. This is why in a level turn, while on-speed your IAS will actually indicate HIGHER than when you're level.


So now let's look at your normal VFR landing pattern.

You will dirty up and stabilize on-speed, gear flaps out trimmed on the downwind. You do a quick mental calculation depending on your aircraft's weight at the time to get a rough IAS number which is used ONLY to verify your AOA is working correctly. If you're on speed and the IAS reads close to your predicted number, you're good to go and don't look at it anymore. At the 180 (not abeam) you will start your turn and start a gradual descent to meet your altitude targets. Usually about 200-300fpm is your initial rate of descent, increasing to gradually meet ~600 on final depending on the winds. During that initial descending turn you will have to add a touch of power to maintain that initial 200-300fpm because while descending, the turn takes too much of the vertical component of lift for you to pull power, or even maintain power for the descent. You will pull a little power to increase your ROD as you continue your turn, and rolling wings level in the groove you will have to pull power as that vertical component of lift becomes greater and greater during the wings level transition. This entire approach turn you will be flying on-speed, but your IAS will be changing.

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Originally Posted by sc_neo View Post
Thus i would actually conclude that neofighter is correct in stating that you pretty much use the stick for alignment and keeping the correct angle of your ''hook'' towards the flight deck/wires. And you would establish that correct angle early on and fly that till you touch down. GS control and true airspeed control would then soley happen via the throttle. Besides, it makes the apporach procedure somewhat easier i think, because you simply can put you main focus on one control input.
On-speed is calculated for the optimum approach speed in relation to optimum hook point. The hook point is essentially making sure the main gear and hook touch at the same time in order to prevent hook skips or IFEs (in flight engagements, catching a wire without having the gear on deck, makes for a bad day). Again, we ignore IAS, TAS, GS, etc after we do our initial calculations to ensure AOA is working. I'll check GS briefly and calculate a rough VSI as well, but that's it. But again, I can't stress enough, avoid using anything but IAS when discussing approaches if you're trying to talk about the aircraft's airspeed, because any other speed (TAS, CAS, EAS, GS, etc) is not in relation to what the wing is seeing, and will only cause confusion.

Last edited by ttaylor0024; 03-09-2018 at 05:11 PM. Reason: Formatting
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Old 03-09-2018, 09:53 PM   #202
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Speaking of inflight engagements. One of the A-3's in my dad's squadron (stationed in Guam) got a late wave-off call and when they rotated, the hook accidentally caught a wire. The A-3 got slightly airborne and was slapped back down collapsing the landing gear in the process. They had to sit there for a while because you normally get out of the A-3 from the belly.

A couple months later, my Dad (the OIC of the squadron) told everyone they were going back out to the boat. The navigator that had been in the right seat of that incident said: "You can put on a desk if you want but I am never going back to the boat."
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Old 03-10-2018, 03:22 AM   #203
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Quote:
Originally Posted by NoJoe View Post
Just a small correction: that would be an angle of attitude. Angle of attack is entirely separate from the aircraft's attitude relative to the horizon
There is no such thing as an 'angle of attitude'. There's AoA and pitch attitude. Nothing else.

Quote:
Originally Posted by ttaylor0024 View Post
AOA is explicitly the angle between the chord like and the relative wind, and has nothing to do with airspeed.
If it's unaccelerated 1G flight (e.g. during the approach) there is a fixed relationship between AoA and speed and AoA hence has a lot to do with speed.

Since an aircraft stalls due to a too high AoA it would be impossible to determine a 'stall speed' ( or an approach speed with a corresponding AoA) if this wouldn't be the case.

Last edited by bbrz; 03-10-2018 at 05:52 AM.
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Old 03-10-2018, 08:31 AM   #204
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Quote:
Originally Posted by bbrz View Post

If it's unaccelerated 1G flight (e.g. during the approach) there is a fixed relationship between AoA and speed and AoA hence has a lot to do with speed.

Since an aircraft stalls due to a too high AoA it would be impossible to determine a 'stall speed' ( or an approach speed with a corresponding AoA) if this wouldn't be the case.
I think we both know the point I was making. In my post originally was an image of the formula for lift (can't see it on kobile for some reason, maybe I accidentally removed it when I was fixing my formatting), and if any variable is there (Cl) then there is obviously a relationship. The easiest way to understand aoa is to understand that they're not directly (visibly) related for all aspects of flight, because using (the only) example where a certain airspeed produces a stall extreme oversimplification, which is why I went into detail on many parts about the relationship. Vso and Vs1 aren't even published for the hornet, because it references AOA.

Last edited by ttaylor0024; 03-10-2018 at 08:38 AM.
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Old 03-10-2018, 08:31 AM   #205
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bbrz, your misinterpreting the lessons here and have left out some context, this makes it hard to understand what they where explaining and why.

NoJoe is helping sc_neo, explaining the error using his line

(as in degrees to the horizon) I.E. angle of attitude.

"The angle formed between the main plane of projectile and the horizontal ground. Compare angle of attack."

Then NoJoe went on to explain how AOA works.

Your also misinterpreting the lesson ttaylor0024 is trying to make here, it's not that it doesn't have anything to do with airspeed, he was just explaining how you can have different air speeds and achieve the same AOA.

"AOA is explicitly the angle between the chord like and the relative wind, and has nothing to do with airspeed. I can be at 300kts at 15* AOA, or 20kts at 15* AOA"

It works seen altogether right, by itself you would add....

(AOA is explicitly the angle between the chord line and the relative wind, and has nothing to do with a particular or given airspeed.)

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Old 03-10-2018, 10:05 AM   #206
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Quote:
Originally Posted by David OC View Post
bbrz, your misinterpreting the lessons here and have left out some context, this makes it hard to understand what they where explaining and why

1. ...he was just explaining how you can have different air speeds and achieve the same AOA.
2. (AOA is explicitly the angle between the chord line and the relative wind, and has nothing to do with a particular or given airspeed.)
I'm not misinterpreting anything or leaving anything out. This discussion is not about maneuvering or ACM.

1. Not in the approach (1G) case. It's exclusively about unaccelerated 1G flight. Using terms that don't exist in aviation like 'angle of attitude' certainly doesn't help in understanding and/or clarifying this discussion.

2. And again this is only valid during maneuvering and not during the approach or straight and level flight, which is what we are talking about.

Last edited by bbrz; 03-10-2018 at 10:12 AM.
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Old 03-10-2018, 11:29 AM   #207
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I think some of the confusion in the topic is also related to not knowing that not all a/c have the same control laws.
For example you cannot directly compare landing experience of pitch rate command vs AoA command pilot stick which is activated with flaps and gears down in F18.

As a side line... first a/c I learned to fly were gliders. And I learned there exactly the same procedure ... Stick for "AoA" and airbrake as "power" - glideslope.
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Old 03-10-2018, 04:03 PM   #208
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NAME OF THE GAME : STAY ON SPEED PERIOD.

It's just an AOA thing:

Rules:

-1)Pulling on stick or lowering the throttle will increase AOA.
-2)Pushing on stick or adding throttle will lower AOA.
-3)Do what you got to do to stay "Onspeed", you can climb descent turn but do it "onspeed"!
-4)Take a bolter like a man.

So it's not only stick to descend or throttle for speed or the opposite.

It's all at the same time to be as quick as possible.

For the landing/trap, the correction amplitude need to be small and the correction frequency need to be high.

Exemple: below flypath/Onspeed?

there are 2 way to climb.

if you pull the stick you will increase AOA so you need to add power.
or
if you add power your AOA will decrease so you need to pull on stick.


A guy that anticipate will add first a shot of power (deacrease AOA) then pull on stick one millisec after. (so throttle for glide path/stick for speed, good one)
A guy with no anticipation will pull first, (thus increase AOA) then add throttle. (stick for glide path/ throttle for speed in this case)

The first one is the most common and explained, but the second will work as well.

That was what i was doing when landing on boat.

Last edited by plaiskool; 03-10-2018 at 04:10 PM.
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Old 03-10-2018, 08:18 PM   #209
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Quote:
Originally Posted by plaiskool View Post
there are 2 way to climb.

if you pull the stick you will increase AOA so you need to add power.
or
if you add power your AOA will decrease so you need to pull on stick.
If u are trimmed correctly when adding power, the nose will raise by itself and there is no reason or need to pull on the stick.
i/e Stick/trim for AoA and throttle for glideslope.
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Old 03-11-2018, 05:08 AM   #210
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Quote:
Originally Posted by addde View Post
If u are trimmed correctly when adding power, the nose will raise by itself and there is no reason or need to pull on the stick.
That's not the way to fly any aircraft and it doesn't apply the every plane either.

You never let an aircraft fly you. E.g. apply power and wait for the pitch attitude to change. You always actively control e.g. pitch and power.

Furthermore you are talking about long term flight path changes which can occur (depending on the aircraft) but that's not active aircraft control.

There are aircraft which do exactly the opposite when applying power and aircraft which don't change the pitch attitude at all when applying power, not even in the long term.
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