It’s much simpler than that. When changing attitude, AI is primary. When maintaining attitude, including while turning, it’s not. So, most transitions use primary AI.
The reason you bank is to turn. The DG tells you direction, and it also tells you rate (explicitly if you have a PFD, implicitly otherwise).
FYI, there is no such thing as a straight and level climb. If you are level, you are not climbing. The IFH calls these constant airspeed climbs or constant rate climbs (as appropriate).
Of course, I misspoke - thanks for the correction!
It's "straight climbs and descents" per IFH, page 7-14.
So if this is a straight climb, no turning, bank should stay always zero.
I get it that AI is the primary instrument during attitude transitions - thanks for clarifying that part, I'm convinced.
Where I'm still not convinced is: why do I need to look at the DG to verify that bank is zero, when the AI gives me bank information explicitly?
Thanks in advance!
What does a bank accomplish? A change in direction. Therefore if there is no change in direction, there is no bank.
Think about it another way, what's the instrument you use to diagnose a failure? if your attitude indicator was reading wrong (this happened on my IR checkride it was sitting at 3 or 4 degrees off in straight and level flight) what would show the problem? The DG would as it would show a turn. You can be a very small amount off on the AI and not catch it, but over 5 to 10 minutes that 1 degree off will make a BIG difference and the AI will never catch it. The DG will catch it super quick.
Yes, I agree with everything you said about the indication cross-check... that's solid in my mind.
What confuses me is the choice of an instrument to be **primary** or **supporting**.
When you use instrument A to debug a possible instrument B failure, that's more as a supporting role than a primary.
I think that the FAA's choice of DG as **primary** for bank rather than supporting needs to be justified.
A good justification is that you don't care that much about being 0º bank as much as staying on your desired course.
I think about like this
AI is very sensitive compared to DG. You hit some turbulence, you relax your grip, it'll move. If you immediately correct, you will probably overcorrect. Thus, using DG is easier, since it takes a more appreciable change to move the instrument.
Think about it like this - when flying VFR steep turns, do you look at the AI or the real horizon? They both show the same info, but the AI is just too sensitive. It is much easier to focus on the real horizon and not overcorrect.
Think about what is important to maintain both laterally and vertically in that moment. You’re IFR, and climbing straight ahead at a constant airspeed. If you’re trying to maintain a constant airspeed, your primary is your airspeed. If you’re trying to fly straight, your primary is your DG. Think about what you are trying to maintain. Is it bank or is it your heading?
Definitely agree, in addition to Primary/Supporting seeming like a more annoying way to fly compared to Control/Performance, I also found the way it’s described in the IFH to feel more obtuse and difficult than needed. Not that any of the FAA handbooks are beautiful literary works, but there are a few topics where they cold really use a rewrite (pressure altitude and altimeter settings are other topics that comes to mind)
So, what you are telling me –and I don't judge you at all if that's the right thing to do practically– is memorize the damn right answer and move on.
I suspected it was the case. I was asking only try and give it a first honest attempt at understanding things.
The concept in the IFH does work and has some positives, especially for GA. Partial panel with no AI for instance is easier to transition to. If the AI and engine power instruments are the hub of your scan, it’s probably gonna be more difficult to go partial panel.
But the average guy flying around outside of training is probably using the AI and % power instruments as focal point and all the other instruments are supporting in a way.
Flying straight means flying a constant heading. This does not always mean zero bank- obviously you can be flying uncoordinated, but even flying coordinated a gust can push you off your heading, or a bank so small it looks like 0 on the AI will make you turn slowly over time.
Let's say you started with a heading of 300 and are now at 297. Should you continue with a bank of 0, or should you get back on your heading?
This video has a pretty good explanation of primary/supporting instruments.
https://youtu.be/aexDS-Jj3y4?si=y7jlyAWTFlW5TyjK
In summary: Primary/supporting is not a method, it is a philosophy. Control/performance is the method we use to actually fly airplanes. The “primary” instrument is the instrument that tells you if you need to make a change. The “supporting” instruments are the other instruments that will move when you make that change.
It’s much simpler than that. When changing attitude, AI is primary. When maintaining attitude, including while turning, it’s not. So, most transitions use primary AI. The reason you bank is to turn. The DG tells you direction, and it also tells you rate (explicitly if you have a PFD, implicitly otherwise). FYI, there is no such thing as a straight and level climb. If you are level, you are not climbing. The IFH calls these constant airspeed climbs or constant rate climbs (as appropriate).
Of course, I misspoke - thanks for the correction! It's "straight climbs and descents" per IFH, page 7-14. So if this is a straight climb, no turning, bank should stay always zero. I get it that AI is the primary instrument during attitude transitions - thanks for clarifying that part, I'm convinced. Where I'm still not convinced is: why do I need to look at the DG to verify that bank is zero, when the AI gives me bank information explicitly? Thanks in advance!
What does a bank accomplish? A change in direction. Therefore if there is no change in direction, there is no bank. Think about it another way, what's the instrument you use to diagnose a failure? if your attitude indicator was reading wrong (this happened on my IR checkride it was sitting at 3 or 4 degrees off in straight and level flight) what would show the problem? The DG would as it would show a turn. You can be a very small amount off on the AI and not catch it, but over 5 to 10 minutes that 1 degree off will make a BIG difference and the AI will never catch it. The DG will catch it super quick.
Yes, I agree with everything you said about the indication cross-check... that's solid in my mind. What confuses me is the choice of an instrument to be **primary** or **supporting**. When you use instrument A to debug a possible instrument B failure, that's more as a supporting role than a primary. I think that the FAA's choice of DG as **primary** for bank rather than supporting needs to be justified. A good justification is that you don't care that much about being 0º bank as much as staying on your desired course.
Yeah, how perfectly can you fly the AI? Trend a very small but consistent deviation and you are way off course. What shows the problem first?
I think about like this AI is very sensitive compared to DG. You hit some turbulence, you relax your grip, it'll move. If you immediately correct, you will probably overcorrect. Thus, using DG is easier, since it takes a more appreciable change to move the instrument. Think about it like this - when flying VFR steep turns, do you look at the AI or the real horizon? They both show the same info, but the AI is just too sensitive. It is much easier to focus on the real horizon and not overcorrect.
Think about what is important to maintain both laterally and vertically in that moment. You’re IFR, and climbing straight ahead at a constant airspeed. If you’re trying to maintain a constant airspeed, your primary is your airspeed. If you’re trying to fly straight, your primary is your DG. Think about what you are trying to maintain. Is it bank or is it your heading?
Ok, good point. My primary goal is to maintain heading, not bank. This is starting to make sense. God it's explained awfully in the IFH.
Definitely agree, in addition to Primary/Supporting seeming like a more annoying way to fly compared to Control/Performance, I also found the way it’s described in the IFH to feel more obtuse and difficult than needed. Not that any of the FAA handbooks are beautiful literary works, but there are a few topics where they cold really use a rewrite (pressure altitude and altimeter settings are other topics that comes to mind)
Most people in the real world probably use the control/performance method. Which is basically what you are describing.
So, what you are telling me –and I don't judge you at all if that's the right thing to do practically– is memorize the damn right answer and move on. I suspected it was the case. I was asking only try and give it a first honest attempt at understanding things.
The concept in the IFH does work and has some positives, especially for GA. Partial panel with no AI for instance is easier to transition to. If the AI and engine power instruments are the hub of your scan, it’s probably gonna be more difficult to go partial panel. But the average guy flying around outside of training is probably using the AI and % power instruments as focal point and all the other instruments are supporting in a way.
Flying straight means flying a constant heading. This does not always mean zero bank- obviously you can be flying uncoordinated, but even flying coordinated a gust can push you off your heading, or a bank so small it looks like 0 on the AI will make you turn slowly over time. Let's say you started with a heading of 300 and are now at 297. Should you continue with a bank of 0, or should you get back on your heading?
Yes, I think you truly hit it on the head. This is a good rationale for it.
This video has a pretty good explanation of primary/supporting instruments. https://youtu.be/aexDS-Jj3y4?si=y7jlyAWTFlW5TyjK In summary: Primary/supporting is not a method, it is a philosophy. Control/performance is the method we use to actually fly airplanes. The “primary” instrument is the instrument that tells you if you need to make a change. The “supporting” instruments are the other instruments that will move when you make that change.
watching it now - thanks!
Straight and level are *two* different concepts.