Standard rate turns on kap150 auto pilot

[georgeb]

Greetings all. I have an auto pilot question for all you hard core IFR folks.  I just had my AP adjusted to correct a chasing issue I was having. Anyway, while it turns much smoother and it’s solved my wing rocking issue, I wondered what turn rates I had now that it’s all working. I went out and tested some standard rate turns with the AP and here’s what I got: to the left, I’ve got 2 minute, 15 second turn; to the right I have a 2 minute 40 second turn. 
so my question to the group is 1. Does it really matter for mostly VFR flying?, and 2. Should I leave well enough alone or shall I have them tweak it some more. 
Thank you all

 

[Denver98]

Obviously it’s a little slow. Asked my wife, and she has never thought that an aircraft wasn’t doing a standard rate turn.   As long as the turn will keep you on the protected side of a holding pattern or keep you from over shooting final, you’ll be fine.  That said, if it’s something that can be adjusted without to much trouble it might be worth a try.  If it follows the line,  odds are your fine.  

My opinion, not worth the paper it’s printed on.    

[PT20J]

The KAP/KFC 150 autopilots are attitude based not rate based like the S-TEC and KAP 140.  Max bank angles are limited to 8 to 30 +/-3 degrees depending on what the autopilot is trying to do but neither the KAP 150 Pilots Guide nor Installation Manual specify the turn rate. So long as it follows the heading bug at a reasonable bank angle and captures a course I’d be happy with something designed in 1980. The best way to modernize its performance is to connect it to a GPS with GPSS.

Skip

 

[David Lloyd]

When I was setting up the Dynon autopilot in the RV, I set the max bank to 30 degrees.  As a few years went by I noticed at times the turns weren't always standard rate.  It was pretty good at normal cruise speed but too quick at slow speeds.  A little reading revealed the autopilot was not making a standard rate turn as I thought, it was turning the max bank set, just as designed.  I suspect many other autopilots are this way.

[PT20J]

Autopilots may or may not make turns at a standard rate. But, the standard rate turn is really an archaic concept anyway and of no practical value today. It originated when the turn and bank was the only gyro instrument. The FAA allows removal of the T&B/turn coordinator and substitution with a backup attitude indicator. To quote from AC91-75:

Replacing the rate-of-turn indicator will mean losing an easy reference for standard rate turns. However, in today’s air traffic control system, there is little need for precisely measured standard rate turns or timed turns based on standard rate.

If you want to make turns at approximately standard rate, the bank angle as a function of airspeed is easily approximated by TAS(knots)/10 + 7. I just use 15 degrees at approach speeds and 20 for holding.

Skip

[georgeb]

Thank you all. Leaving it alone.  It’s working great as is. 
 

[jetdriven]

On 2/2/2020 at 9:32 AM, PT20J said:

Autopilots may or may not make turns at a standard rate. But, the standard rate turn is really an archaic concept anyway and of no practical value today. It originated when the turn and bank was the only gyro instrument. The FAA allows removal of the T&B/turn coordinator and substitution with a backup attitude indicator. To quote from AC91-75:

Replacing the rate-of-turn indicator will mean losing an easy reference for standard rate turns. However, in today’s air traffic control system, there is little need for precisely measured standard rate turns or timed turns based on standard rate.

If you want to make turns at approximately standard rate, the bank angle as a function of airspeed is easily approximated by TAS(knots)/10 + 7. I just use 15 degrees at approach speeds and 20 for holding.

Skip

At 100kt it’s ~17 degrees of bank. At 150kt it’s -~22 degrees.  
or, ~20 degrees for everything. 

[kortopates]

I don't know if I would go so far as to say standard rate turns are entirely an archaic concept since every instrument student needs to be able to demonstrate flying a partial panel approach.If their flying a legacy panel it can get important. Although I teach how easy this using their WAAS GPS for TRK for real world IFR, they still should know how to set up a standard rate turn - afterall so many vintage Mooney owners doing their instrument rating don't have a IFR GPS and still need to do it the hard way. I was taught and teach using the attitude indicator to roll into a standard rate turn using the expected degrees bank based on TAS and then use the Turn-bank to confirm or tune. 

For rules of thumb for estimating standard rate turns, the FAA has gone to recommending 15% of TAS (or TAS/10+ 5), I assume because it's more accurate at the slower airspeeds used by GA trainers. When you run the numbers comparing computed bank angle you find that using the 10% + 5 method that its spot on between 90-140 kts which covers our Mooney's and virtually any SE trainer. But as you go faster, the 10% + 7 method has a sweet spot in the 130-150 kts, below 130 it over estimates and over 150 it under estimates. 

Here are some numbers, the source from actual computed (supposedly good to 5 digits) comes from: http://www.luizmonteiro.com/Article_Bank_Angle_for_Std_Rate_01.aspx

TAS	Actual Computed	10% TAS + 5	10% TAS + 7
90	14	14	16
100	15	15	17
110	17	17	18
120	18	18	19
130	20	20	20
140	21	21	21
150	22	23	22
160	24	24	23
170	25	26	24
180	26	27	25

 

important? not really, but anal for sure.

Edited February 4, 2020 by kortopates
KIAS, IAS columns -> TAS

[Bolter]

On 2/1/2020 at 9:17 PM, PT20J said:

The KAP/KFC 150 autopilots are attitude based not rate based like the S-TEC and KAP 140.  Max bank angles are limited to 8 to 30 +/-3 degrees depending on what the autopilot is trying to do but neither the KAP 150 Pilots Guide nor Installation Manual specify the turn rate. So long as it follows the heading bug at a reasonable bank angle and captures a course I’d be happy with something designed in 1980. The best way to modernize its performance is to connect it to a GPS with GPSS.

Skip

 

One of the bonuses I got by replacing the HSI with a Garmin G5 slaved to a 430W was getting GPSS.  My point being that if you are planning any modern panel upgrades that were not including the AP, you might end up solving your AP problem that way.  Good reason not to dive into an AP repair now, for what is otherwise working well.   

[PT20J]

15 minutes ago, Dan at S43 said:

One of the bonuses I got by replacing the HSI with a Garmin G5 slaved to a 430W was getting GPSS.  My point being that if you are planning any modern panel upgrades that were not including the AP, you might end up solving your AP problem that way.  Good reason not to dive into an AP repair now, for what is otherwise working well.   

One thing that I miss from the old KI 525 that I'm surprised no one else ever copied was the extended lubber line. It was a neat mechanical trick when intercepting a course manually to keep the top of the CDI needle on the bottom of the lubber line for a perfect intercept. With a flight director and/or GPSS you don't really need it, but it was a great cross check.

[PT20J]

41 minutes ago, kortopates said:

I don't know if I would go so far as to say standard rate turns are entirely an archaic concept since every instrument student needs to be able to demonstrate flying a partial panel approach.If their flying a legacy panel it can get important. Although I teach how easy this using their WAAS GPS for TRK for real world IFR, they still should know how to set up a standard rate turn - afterall so many vintage Mooney owners doing their instrument rating don't have a IFR GPS and still need to do it the hard way. I was taught and teach using the attitude indicator to roll into a standard rate turn using the expected degrees bank based on TAS and then use the Turn-bank to confirm or tune. 

For rules of thumb for estimating standard rate turns, the FAA has gone to recommending 15% of TAS (or TAS/10+ 5), I assume because it's more accurate at the slower airspeeds used by GA trainers. When you run the numbers comparing computed bank angle you find that using the 10% + 5 method that its spot on between 90-140 kts which covers our Mooney's and virtually any SE trainer. But as you go faster, the 10% + 7 method has a sweet spot in the 130-150 kts, below 130 it over estimates and over 150 it under estimates. 

Here are some numbers, the source from actual computed (supposedly good to 5 digits) comes from: http://www.luizmonteiro.com/Article_Bank_Angle_for_Std_Rate_01.aspx

KIAS	Actual Computed	10% IAS + 5	10% IAS + 7
90	14	14	16
100	15	15	17
110	17	17	18
120	18	18	19
130	20	20	20
140	21	21	21
150	22	23	22
160	24	24	23
170	25	26	24
180	26	27	25

 

important? not really, but anal for sure.

Wow, Paul, and I thought I was anal. But, then I can't hold a bank angle better than +/- 3 degrees anyway, so I'd have to include some sort of averaging function into my calculations 

When I flew Cirrus SR22s for a while we didn't have a turn coordinator in the panel (there was one out of sight behind the panel to drive the S-TEC autopilot). The Avidyne PFD had the same sort of standard rate indication as the G1000, but we never used it. The Cirrus transition instructors all taught partial panel by using the GNS 430 nav page with the compass card-like depiction of TRK and the standby attitude indicator and altimeter.

I don't find much use anymore for timed approaches, NDB approaches (I removed my ADF) or standard rate turns. I have fond memories of hand flying a C-172 with a hand mike while holding at an intersection and trying to copy a clearance with a single Nav/Com. But, if I may quote Richard Collins, "The good old days: May they never return." I would like to have flown a four course range though ._  _.

Best,

Skip

[jetdriven]

I think it’s actually true airspeed that determines the bank angle. KIAS varies due to altitude, anyway. 

[N201MKTurbo]

I’ve never adjusted a KAP150, but the CIib has two adjustments for the turn limits. I don’t think you can accurately adjust them on the bench top. 

I get the plane stabilized at 90 KTS, turn off the radio coupler, turn the roll knob all the way to the right and adjust the roll limit for a standard rate turn. Then do the same to the left.

[Bolter]

3 hours ago, PT20J said:

One thing that I miss from the old KI 525 that I'm surprised no one else ever copied was the extended lubber line. It was a neat mechanical trick when intercepting a course manually to keep the top of the CDI needle on the bottom of the lubber line for a perfect intercept. With a flight director and/or GPSS you don't really need it, but it was a great cross check.

Some wise instructor taught me that trick, but I had since forgotten.  Had to look it up to remember what it was.  I always appreciate a good mechanical solution, even if I prefer the modern solution day-to-day.  Like the linkages of a steam engine that feed just the right amount of oil to a bearing or slide with each stroke.  

[Andy95W]

3 hours ago, PT20J said:

One thing that I miss from the old KI 525 that I'm surprised no one else ever copied was the extended lubber line. It was a neat mechanical trick when intercepting a course manually to keep the top of the CDI needle on the bottom of the lubber line for a perfect intercept. With a flight director and/or GPSS you don't really need it, but it was a great cross check.

I was taught that, too, but never thought it was unique to the KI-525, it seems to work with every HSI I've ever used (though I'll admit to being partial to the KI525 display- it just seems to be intuitive).

[kortopates]

On 2/3/2020 at 1:30 PM, PT20J said:

Wow, Paul, and I thought I was anal. But, then I can't hold a bank angle better than +/- 3 degrees anyway, so I'd have to include some sort of averaging function into my calculations 

When I flew Cirrus SR22s for a while we didn't have a turn coordinator in the panel (there was one out of sight behind the panel to drive the S-TEC autopilot). The Avidyne PFD had the same sort of standard rate indication as the G1000, but we never used it. The Cirrus transition instructors all taught partial panel by using the GNS 430 nav page with the compass card-like depiction of TRK and the standby attitude indicator and altimeter.

I don't find much use anymore for timed approaches, NDB approaches (I removed my ADF) or standard rate turns. I have fond memories of hand flying a C-172 with a hand mike while holding at an intersection and trying to copy a clearance with a single Nav/Com. But, if I may quote Richard Collins, "The good old days: May they never return." I would like to have flown a four course range though ._  _.

Best,

Skip

Its really not that hard to hold bank accurately in smooth air. My instrument students have all gotten good at it but these anal details have been very helpful in determining the accuracy of the turn coordinator with each new IR student. Knowing exactly what to expect we can quickly tell if we have a lazy turn coordinator that needs servicing and if its the turn coordinators fault for the 2 minute turn not taking 2 minutes etc. and we can confirm where exactly to hold the needle on the TC to precisely keep it at standard. Unfortunately this is still very relevant today because of the many plane owner pilots doing an instrument rating without an IFR GPS.  

Very much agreed - that when we introduce a WAAS GPS with TRK updating at 5x a second, we forget about the compass and timed turns and use the GPS! (Non-waas gets by but at only 1x sec update we can't rely on GPS TRK alone in the turn and still want to supplement.) its really a life saving technology that makes it easy to still fly partial panel to ATP standards. The only thing tricky or difficult about it is bringing in the GPS to the pilots scan but I maintain that's essential to fly with any precision anyway. A good instrument pilot will notice they're diverging by seeing their TRK diverge long before they need to see their CDI diverge off course.  Modern glass brings that GPS info to the PFD as well and makes it even easier. 

[kortopates]

21 hours ago, Andy95W said:

I was taught that, too, but never thought it was unique to the KI-525, it seems to work with every HSI I've ever used (though I'll admit to being partial to the KI525 display- it just seems to be intuitive).

Indeed it does and honestly I thought all of us were teaching that very thing. It works identically on the King HSI as well as G1000, or any glass HSI.

Just last night was the first night of my Advanced IFR class at the local college and that was exactly where I begin, entering a GPS flight plan, using OBS to track a GPS radial (like on a ODP) and how to properly intercept a radial using the HSI CDI to set up the intercept. Once you understand the concept you can apply it to legacy OBS as well.

Edited February 4, 2020 by kortopates

[kortopates]

23 hours ago, jetdriven said:

I think it’s actually true airspeed that determines the bank angle. KIAS varies due to altitude, anyway. 

You're so right! I used TAS in the writeup, but I mislabeled the columns as KIAS and IAS - I'll correct those to TAS as well. Thanks

[PT20J]

3 hours ago, kortopates said:

Indeed it does and honestly I thought all of us were teaching that very thing. It works identically on the King HSI as well as G1000, or any glass HSI.

I'm not sure we are talking about the same thing. Here's the 525 with the extended lubber line:

Here is the depiction of the G5 and G1000.

[kortopates]

3 minutes ago, PT20J said:

I'm not sure we are talking about the same thing. Here's the 525 with the extended lubber line:

Here is the depiction of the G5 and G1000.

True the others don't have the "extended" longer lubber line, you're right - and that does make it obvious to someone first learning the technique. But does its absence really interfere with you seeing what the CDI is point too without it? Once you know the concept you can apply just as well to each of the examples you give above. Which are all good examples BTW. Thanks for clarifying as I wasn't placing importance on the "extended" aspect - just the concept.

[PT20J]

37 minutes ago, kortopates said:

True the others don't have the "extended" longer lubber line, you're right - and that does make it obvious to someone first learning the technique. But does its absence really interfere with you seeing what the CDI is point too without it? Once you know the concept you can apply just as well to each of the examples you give above. Which are all good examples BTW. Thanks for clarifying as I wasn't placing importance on the "extended" aspect - just the concept.

OK, Paul, I'm with you. Yep, I can visualize the intercept without the extended lubber line. (But then I used to be able to visualize my position in space long before moving maps!) I think we all just like whatever visual aids are available. I used to live in the SF Bay area and most of my IFR flying was punching through a coastal stratus layer. Now my most often flown IFR flight is 0S9 and KPAE in crappy weather. (Today was 2 miles viz in snow showers with a 30 knot, 30 deg crosswind down to an 800 foot ceiling). This 20 minute flight involves two TRACONs, at least two altitude changes and often a couple of changes in routing (sometimes Whidbey clears me to CVV before handing me off to Seattle approach; sometimes to PAE; sometimes just a heading). Talking, getting ATIS, turning to assigned headings and climbing to assigned altitudes, while programming the GNS 430W makes this really busy. I don't think I could fly this well without an autopilot. The last thing on my mind is standard rate turns. 

Skip