ADI Dilema

[Piloto]

I noticed that planes with a vacuum ADI (IFR certified) do not have (or require) a backup ADI like those with the Aspen or Gamin ADI. Is a vacuum ADI more reliable?

José 

Edited October 18, 2018 by Piloto

[PaulM]

The electric turn and bank (or Turn Coordinator) was considered the backup instrument of that era.  Since it was electric and not vacuum that gave the systems redundancy,  it was already installed and the TC+compass was considered enough... In the plane pictured the HSI is all electric, where previous generations would have been pneumatic, so you would lose the AI and the DG/HSI. 

Now with the new systems  you need a backup for the Aspen/Garmin it is considered that another electric AI is better than putting in a TC. 

Many people with electric TC's also put in backup Electric AI's.. as the AI is considered a better backup in real IFR.   I suspect that this trend was firmly established by the start of the PFD era, so the STC's say "backup AI" rather than backup device, AI, or TC..  

[KSMooniac]

Most of our planes were originally certified under CAR3 rules. FAR Part 23 is more stringent, and even newer updates to old CAR3 planes (like Mooney) sometimes need to step up to the latest rules even though the original Type Certificate remains under the old rules.

All new STC products have to meet the latest regs, even if installing on old planes. Hence the rampant backup requirements for new stuff...

Sent from my LG-US996 using Tapatalk

[Steve W]

I have to say, that's one of the best equipped pre-glass panels I've ever seen.

 

[Piloto]

1 hour ago, PaulM said:

The electric turn and bank (or Turn Coordinator) was considered the backup instrument of that era.  Since it was electric and not vacuum that gave the systems redundancy,  it was already installed and the TC+compass was considered enough... In the plane pictured the HSI is all electric, where previous generations would have been pneumatic, so you would lose the AI and the DG/HSI. 

Now with the new systems  you need a backup for the Aspen/Garmin it is considered that another electric AI is better than putting in a TC. 

Many people with electric TC's also put in backup Electric AI's.. as the AI is considered a better backup in real IFR.   I suspect that this trend was firmly established by the start of the PFD era, so the STC's say "backup AI" rather than backup device, AI, or TC..  

You are  right Paul but TCs never tumble, good for spin recovery in IFR. Altimeter and VSI are also good for pitch control. 

Spirit of St Louis panel. Good for IFR flight across the Atlantic, No ADI.

José

 

 

Edited October 18, 2018 by Piloto

[steingar]

55 minutes ago, Piloto said:

You are  right Paul but TCs never tumble, good for spin recovery in IFR. Altimeter and VSI are also good for pitch control. 

Spirit of St Louis panel. Good for IFR flight across the Atlantic, No ADI.

José

 

 

Yeah yeah yeah, and he did it on a night with no sleep looking out a periscope.  But lets not forget that a bunch of guys died trying to do the same thing.  Indeed, the next pilot to make it in one gulp over the Atlantic was years later and named Amelia Earhart.  We don't all have to operate like that.

Having my six depend on a little fragile machine that can and will break now and again gives me the willies.

[takair]

An accident just this weekend, with one of our locals, emphasizes that having a backup ADI is better than a backup TC.  Took off out of DXR and had the ADI fail soon after.  He fought it for a while before losing it on the south side of Long Island.  Experienced CFI.  Very unfortunate.  Just last year, a Bonanza had an accident under similar conditions, also near Long Island.  Ultimately, it is best to have three ways to detect your attitude, this is the level of redundancy expected in part 25 aircraft and not a bad thing to have in our Mooney’s, especially with modern glass.  

[carusoam]

The oddity of the TC...

They can appear healthy and operate normally for decades...

But...

As they wear? They start to get really jumpy in turbulence... so jumpy they would be hard to follow if that is all you have to keep the wings level...

so... next time you fly in the bumps... check that TC... See if it’s worthy...

 

PP experience I got training for the IR in north Jersey... cold winter bumps in the dark over bumpy terrain... in a C172...

odd things one does when between Mooneys....

Best regards,

-a-