Instruments

[Clear-&aMillion]

Obviusly if you are flying a single-engine aircraft, a failure of that engine will render most of your gyroscopic instruments useless. Perhaps this is why many people consider single-engine IMC risky bussiness.

But why is it that the turn-coordinator is usually electrically powerd, whereas the AI is vacuum driven? If your engine fails in IMC, wouldn't you want your IA to continue working, rather than the TC???

 

[masedogg19]

The FAA now allows the turn coordinator to be replaced with an electrically driven AI. Sporty's sells one for around $2000. It's made better than most and is around $1000 cheaper than the nearest competitors.

 

[ePilot22]

The first reason is redundancy, with the AI and DG vacuum driven and the TC electrically driven there is a back-up in case one system fails.

Second. If your AI is electric (I’m assuming you then have a vacuum driven TC, if not, then your putting all your eggs in one basket) and the TC is then vacuum and you have an engine failure, you’re going to lose the DG and TC. The AI provides pitch and bank, but not rate of turn. Since compass turns require a standard rate of turn (3° per second) the only way the get good reliable information would be from the TC.

Plus pitch information can be obtained from the Airspeed Indicator, Altimeter and VSI, so the only real item missing without the AI would be bank. And again without a DG, you’d be required to make compass turns. It would be much easier and safer to do that with a known rate of turn, instead of just a bank angle.

The AI is a good instrument for a quick understanding of what the aircraft is doing, but it can become relied upon too much. Vacuum pumps are built to fail. The shaft the drives the pump is about as thick as a pencil and if something where to jam the pump, the shaft is designed to shear.

Hope this helped.



eP.

 

[Donsa320]

Obviusly if you are flying a single-engine aircraft, a failure of that engine will render most of your gyroscopic instruments useless. Perhaps this is why many people consider single-engine IMC risky bussiness.

But why is it that the turn-coordinator is usually electrically powerd, whereas the AI is vacuum driven? If your engine fails in IMC, wouldn't you want your IA to continue working, rather than the TC???

Why do you say that? Unless the engine siezes up, you'd have everything. The vacuum pump would keep vacuuming and the battery and alternator would keep the rest going for the time it would take you to arrive at Earth, no? <g>

DC

 

[Clear-&aMillion]

Why do you say that? Unless the engine siezes up, you'd have everything. The vacuum pump would keep vacuuming and the battery and alternator would keep the rest going for the time it would take you to arrive at Earth, no? <g>

DC

I supposed you'd be correct. I didn't consider that the prop would likely remain windmilling.

 

[paulsalem]

Here is my question.

Why do faster aircraft have Turn & Slip indicators as opposed to the turn & bank?

It seems lot easier to keep an a/c upright using a turn and bank.

 

[wmuflyguy]

My guess would be cost.

Eventually once yuou get going too fast the TC becomes useless, as a 3 degree a sec turn would require too much bank (greater than 30 degrees). The "ball" then is incorporated in with the AI somhow.

 

[DC8 Flyer]

Here is my question.

Why do faster aircraft have Turn & Slip indicators as opposed to the turn & bank?

It seems lot easier to keep an a/c upright using a turn and bank.

Not bashing at all, but could you list the "faster" aircraft that you have seen a T&S in as opposed ot just and inclinometer?

 

[MauleSkinner]

Here is my question.

Why do faster aircraft have Turn & Slip indicators as opposed to the turn & bank?

It seems lot easier to keep an a/c upright using a turn and bank.

A little history lesson may be in order here...

The Turn & Bank instrument (the one with the vertical needle) was the original style of instrument. It shows rate of change in yaw (heading), with the inclinometer ball providing "quality of turn" information.

Then, somebody came up with the bright idea of using the same instrument as a reference for the autopilot, probably because the complexity of the attitude indicator didn't lend itself to an inexpensive autopilot installation. But since the autopilot directly controls bank, not yaw, it needed some kind of bank input. The solution was to incline the turn gyro's axis so that it also shows rate of roll information. This became the Turn & Slip instrument (the one with the little airplane wingy thingy that says "no attitude information", or something like that).

So, your answer doesn't have to do with the speed of the airplane, so much as the potential for an autopilot.

Fly safe!

David

 

[paulsalem]

Not bashing at all, but could you list the "faster" aircraft that you have seen a T&S in as opposed ot just and inclinometer?

Sure:

BE-350
http://www.airliners.net/open.file/805486/L/

CE-500 (fast is a relitive term)
http://www.airliners.net/open.file/207653/L/


It's not so much a big deal in those planes but in a piston twin (the twin cessna's seem to have T&B) when you only have one A/I, if that fails, personally I'd rather have a Turn Coodinator over a T&B for roll information.

I had just noticed that you don't see turn coodinators in faster aircraft. Usually you just see an inclonometer on the attidude indicator, but those they do have a rate of turn device, you have a T&B, as seen in the aircraft pics above.

But I guess those "faster" a/c have better autopilots like Maul said, and the designers don't see the need for a more expensive Turn Coodinator over a T&B.