Piper Arrow PA-28R-201?

[jordane93]

So I'm studying for my Commercial ASEL oral and looking at the systems for the Arrow in the POH. In Section 7.23 Instrument Panel, it says that "the turn indicator, on the left side, is electrically operated. So does the TC rely fully on electric power to operate normally or is it vacuum based as well? I checked in the Vacuum System section and it says "the vacuum system is designed to operate the air driven gyro instruments. This includes the directional and attitude gyros when installed"

 

[EdFred]

TC is electric. I'm 99% sure ALL TCs are electric. When you turn on the master and hear the whirrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr. That's the TC spinning up.

 

[jordane93]

TC is electric. I'm 99% sure ALL TCs are electric. When you turn on the master and hear the whirrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr. That's the TC spinning up.

I think I was mixing electric gyros with vacuum based gyros up. I get it now. Just had a brain fart

 

[EdFred]

It happens.

 

[Frank]

I think the idea is to have some reference should the vacuum system fail,in which case you have the TC. If only the electric system fails, you lose the TC, but have vacuum instruments. There may be common mode failures for both vacuum system and electrical system, but they are relatively rare. Once you have either failure, it is a good idea to get on the ground.

 

[tmyers]

TC is electric. I'm 99% sure ALL TCs are electric. When you turn on the master and hear the whirrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr. That's the TC spinning up.

I always wondered what that sound was!!!!

 

[Ted]

I always wondered what that sound was!!!!

I always thought it was the engine spooling up.

 

[tmyers]

My turbine spools all the way to 2700 RPM WooooHooooo

We need to pick a day for lunch this week!!!!

 

[mondtster]

TC is electric. I'm 99% sure ALL TCs are electric. When you turn on the master and hear the whirrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr. That's the TC spinning up.

Not all TCs are electric. Some are vacuum driven.

The majority of the ones I've seen are electric however, so it is a good assumption that it is until you know differently. I've seen a number of them that even say they're electric right on the face of the instrument.

 

[poadeleted20]

Not all TCs are electric. Some are vacuum driven.

I've never seen a vacuum TC, although I have seen vacuum turn-and-bank instruments (the old style needle-and-ball T&B's) installed in planes that had venturi-driven vacuum instruments. They all had separate venturis for each of the three IFR-required gyro instruments (AI, HI, T&B ) because you could not get approval for IFR operations with all three required gyros running off the same vacuum source. Don't think any manufacturers have built a plane like that for at least 50 years, although there are no doubt some more recent E-AB's built that way.

 

[mondtster]

I've never seen a vacuum TC, although I have seen vacuum turn-and-bank instruments (the old style needle-and-ball T&B's) installed in planes that had venturi-driven vacuum instruments. They all had separate venturis for each of the three IFR-required gyro instruments (AI, HI, T&B ) because you could not get approval for IFR operations with all three required gyros running off the same vacuum source. Don't think any manufacturers have built a plane like that for at least 50 years, although there are no doubt some more recent E-AB's built that way.

Good point, I wasn't really thinking about that. All the vacuum driven instruments I've seen were turn and bank not coordinators.

Also, as you noted, nearly all of them I've seen have been in vintage aircraft using venturis but I have seen a few installed in '70s era Citabrias with VFR panels that were running off of a vacuum pump.