Turn coordinator question for a CFII

[Lance Link]

I posted a while back about the need and/or desirability of having a turn coordinator in addition to a Castleberry.  I understand now that the turn coordinator is not necessary for flight, and may not add much benefit in that regard.

But....I am now being told that a turn coordinator is required for IFR training, and that it is something I will want just the same for IFR training.  (I find this hard to believe).

Is it true?

Thanks for any help!

[carusoam]

Lance, There is an FAA bulletin around here that I came across recently... probably what you have mentioned...

Essentially, the TC is an antiquated device that hasn't worked very well for a few pilots when the chips were down... ref. to a NY Bonanza pilot that lost his vacuum above the clouds... and descended into the clouds under control, then came out the bottom in pieces....

A spare AI can technically replace a TC... a few things to look for...

• it has to have a ball for coordination... and
• the pilot needs to be trained to calculate a two minute 360...
• Knowing the relationship of bank angle and air speed really works... 17° seems to work for most Mooneys for that one common speed...
• a secondary source of power helps... one AI that is electric, and the other vacuum... or two batteries, or two alternators that kind of thing...

As far as training goes... compass and turn coordinator... is kind of like going out in your underclothes... not a very likely scenario, but if you get through the night... you are better for it...  

If you are training to be a pro pilot... some planes you will fly may be pretty ancient and TCs are really common for plan B... and standard rate turns... and keeping the clean side up after the vac pump fails in IMC...

If you are a PP and only fly one plane... go with three AIs because you can...

To get past today’s challenge... there are a bazillion used TCs available... the only thing they required is a 12v line...

Install it... get on with your training...

You spent more time writing about it already than it would take to install one... 

List of not very useful devices... once you have a WAAS GPS....

• mag compass... the real one suffers from ANDS, and Gaussian challenges... in metal cages...
• TCs
• Real VSI... the real one lags terribly, by design... and isn't very precise either...

Discuss this with your CFI with some detail... See what his real reasons are to mandate use of the TC?

Glad you asked the question... See if we can get some Mooney CFI responses...

PP thoughts only, my first attempt at the IR ended with mag compass problems... it took another decade to start again.

Don’t get bogged down... we can help you find the answer...

Best regards,

-a-

 

 

[201er]

Better yet to have both for when this happens:

 

[kortopates]

16 hours ago, Lance Link said:

I posted a while back about the need and/or desirability of having a turn coordinator in addition to a Castleberry.  I understand now that the turn coordinator is not necessary for flight, and may not add much benefit in that regard.

But....I am now being told that a turn coordinator is required for IFR training, and that it is something I will want just the same for IFR training.  (I find this hard to believe).

Is it true?

Thanks for any help!

No Its not true, but you do have to follow the guidelines of the AC 91-75 attached below which also requires you have to slip/skid indicator/ball mounted with your backup Attitude indicator which of course has to be powered by a different source such as electric if your primary if vacuum. But you are golden if you meet the requirements given in the AC.

And you should know how to accurately set up for standard rate turn using bank and airspeed which is as simple as establishing a bank angle of 15% of your true airspeed in knots. But rather than try to compute 15% in your head, I teach take 10% and then add 1/2 of the 10% for the least brain power solution. (I find us instrument pilots have very little brain power left after using most of it to just fly level and straight!) So if your doing 100 knots, its 10 + 5  = 15%. Doing 120 knots, its 12 + 6 = 18% If you do the math its very accurate approximation. 

Heck, here is the math for next example at 140 kts verifying the expected 14+7= 21 degrees bank:

2.99/sec =DEGREES(9.8 *TAN(21*3.14/180)/72)

Result is 2.99 or 3 deg/sec which equals standard rate based on:

9.8 = g (gravity)

21 is bank angle in degree then converted to radians by * pi/180

72 is 72 m/sec = 140 kts.

IMO the precise instrument pilot uses the attitude indicator to setup a standard rate turn and then uses glances at TC, or these days the glass rate of turn indicator, to keep it at standard rate while turning - rather than somewhat hunting for the proper rate with just the TC. But that's not something expected of a instrument student. 

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC91-75.pdf 

[201er]

40 minutes ago, kortopates said:

IMO the precise instrument pilot uses the attitude indicator to setup a standard rate turn and then uses glances at TC, or these days the glass rate of turn indicator, to keep it at standard rate while turning - rather than somewhat hunting for the proper rate with just the TC. But that's not something expected of a instrument student. 

Haven’t thought about this before but since you brought it up, that’s a great way to put it! Exactly how I do it. This is yet another reason I opted to keep the TC and add an AI.

[Jim Peace]

inclinometer tons of value

Turn and bank indicator, not so much....

I only kept mine because it is how my Stec30 works......

[Lance Link]

Thanks everyone for the feedback.  I suspected a turn coordinator could not possibly be required for IFR instruction, if the plane is IFR legal without it.  That would not make any sense at all.  But, even though I don't really need it, and have three other back-ups, given how much money this machine has costs and continues to cost, not putting in the TC while doing the other humble panel work is probably just too nickel and dime, even for me.  Unless I can find a better use for that 2" hole.  An AV-20 maybe?  Darn, something else to obsess about.    

[PT20J]

Much better to have a backup AI than a turn coordinator especially for IFR training. The examiner cannot ask you to do anything that the airplane is not equipped to do. So... no pesky partial panel timed turns. BTW the early Cirrus SR22 had an Avidyne glass panel and a backup AI and an S-TEC autopilot with the turn coordinator required for the rate-based autopilot mounted behind the panel out of sight.

Skip

[carusoam]

People are often surprised to find various instruments operating behind the panel...

PP thoughts only,

-a-

[mike_elliott]

On 6/16/2019 at 12:44 AM, PT20J said:

BTW the early Cirrus SR22 had an Avidyne glass panel and a backup AI and an S-TEC autopilot with the turn coordinator required for the rate-based autopilot mounted behind the panel out of sight.

i believe this is true for the G1000/stec Mooneys as well. Can you confirm @Deb ?

[Deb]

Yes; it’s behind the MFD.