Discrepancy in textbook???

Holocene

Well-Known Member
A review question essentially asks:

"True or False, only the gyroscopic flight instruments can provide bank information".

I claimed this was false, reasoning that the mag compass could technically proivde very crude bank information in straight and level flight.

The book however, claims the appropriate answer to be "true".

Maybe their reasoning is that only the six-pack instruments are "flight instruments"?

but then they would contradict themselves, as they defined "flight instruments" as:

"...those instruments providing information regarding aircraft attitude, direction, altitude, and speed."

:confused:
 

tgrayson

New Member
I claimed this was false, reasoning that the mag compass could technically proivde very crude bank information in straight and level flight.
Not really. Your compass will remain level with respect to the direction of the apparent gravity inside the airplane. During a bank, the apparent gravity will still act "straight down" with respect to the airframe, meaning it will still act perpendicular to the floor, more or less, depending on how coordinated you are. But it will not remain level with respect to the horizon.

The same goes for any of the other devices that people propose to use to maintain level flight, a glass of water, or a pencil hung from a string. None of these things will work.
 

planejay

Well-Known Member
It is also argued that the turn coordinator doesn't provide bank info....which I partially agree with and partially disagree with.
 

tgrayson

New Member
It is also argued that the turn coordinator doesn't provide bank info....which I partially agree with and partially disagree with.
If you are coordinated, then the TC does indirectly provide bank info.

Still, the question wasn't whether all gyro instruments provide bank info, but whether only gyro instruments provide bank info.
 

Holocene

Well-Known Member
Not really. Your compass will remain level with respect to the direction of the apparent gravity inside the airplane. During a bank, the apparent gravity will still act "straight down" with respect to the airframe, meaning it will still act perpendicular to the floor, more or less, depending on how coordinated you are. But it will not remain level with respect to the horizon.

The same goes for any of the other devices that people propose to use to maintain level flight, a glass of water, or a pencil hung from a string. None of these things will work.
My reasoning was that if the ball is centered, and you hold a constant heading with the compass, you cannot possibly be in a bank, you must be wings-level. I view this as "bank information" as it relates to instrument flying.
 

tgrayson

New Member
If I were to do point rolls without changing heading would the TC show anything but wings level?
Well, a turn and bank indicator probably would not, since it measures yaw rate and you just defined away any yaw. ;) However, a TC also shows roll rate, so I would be surprised if it showed nothing.

During a point roll, does the ball remain centered?
 

tgrayson

New Member
My reasoning was that if the ball is centered, and you hold a constant heading with the compass, you cannot possibly be in a bank, you must be wings-level. I view this as "bank information" as it relates to instrument flying.
To this degree, perhaps it might work, but I think it would be difficult to steer the airplane this way, since the compass works in reverse. (The headings on the left side of the current heading require a right bank.) A vertical card compass would work much better.
 

planejay

Well-Known Member
I think "wings level" was not the right choice of words. My point is that it is perfectly coordinated yet the TC would not be showing "indirect" bank information. I agree with the rest though, whatever that is worth.
 

Derg

New Arizona, Il Duce/Warlord
Staff member
A review question essentially asks:

"True or False, only the gyroscopic flight instruments can provide bank information".
True.

I claimed this was false, reasoning that the mag compass could technically proivde very crude bank information in straight and level flight.
Well, if you're accelerating or decelerating, it's going to indicate a turn.
[/QUOTE]
 

Minuteman

“Dongola”
I also say True.

Although they are not common flight instruments, an aircraft's attitude can also be determined from inertial measurements (accelerometers or laser ring 'gyros', which aren't really gyroscopic) or multi-sensor GPS measurements. :buck:
 

tgrayson

New Member
My point is that it is perfectly coordinated yet the TC would not be showing "indirect" bank information.
We haven't established that this maneuver is coordinated. Seems unlikely if you're using the rudder during the maneuver to keep the same heading, but I admit it's possible. The ball measures lateral acceleration and it's conceivable you would experience none in this maneuver.

And what about the roll rate measurement of the TC?
 
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