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# Rule of thumb in base turns.

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# Rule of thumb in base turns.

30th Nov 2018, 22:21

Join Date: Jul 2016
Location: lisboa
Posts: 55
Rule of thumb in base turns.

Hi there, folks!

I just wonder if there is any rule of thumb to calculare the exact bank angle when it comes to base turns.

This approach can be used as a an example:

Scenario: 170 Kt along radial 145. What would be your exact bank angle?

Thx!
1st Dec 2018, 09:32

Beacon Outbound

Join Date: Mar 2002
Location: "Home is were the answer machine is"
Posts: 646
There is no exact bank angle to calculate as it depends on your ground speed, which changes during the turn depending on wind speed and direction.
1st Dec 2018, 10:04

Join Date: Jul 2016
Location: lisboa
Posts: 55
What about changing the word "exact" for "approximately/zero wind"?

I find myself in times of trouble while carrying out this kind of adjustments -depending on the approach: distance from VOR & radials of separation-.

Any help would be very welcome.

Cheers.
1st Dec 2018, 12:46

Avoid imitations

Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 12,104
I think this might be taking "flying by numbers" a bit too far.
1st Dec 2018, 13:07

Join Date: Jan 2018
Location: Amantido
Posts: 769
Originally Posted by smthngdffrnt
Hi there, folks!

I just wonder if there is any rule of thumb to calculare the exact bank angle when it comes to base turns.

This approach can be used as a an example:

https://www.nav.pt/CD/NAVProtectedDa...PD_12-5_en.pdf

Scenario: 170 Kt along radial 145. What would be your exact bank angle?
Thx!
IFR procedures are predicated on 3°/sec turn or max 25° bank angle. And the rule of thumb is TAS/10+7.

Do you want to take it to an extreme level? The 1:60 rule works for you. 1° degree is approximately 1nm at 60 miles from the station, at 15nm it is 0,25nm, etc... 3°/sec so you know by how many radials you lead in your inbound turn depending on your ground speed.

But this is too complicated, why would you do this? With an HSI keep the bottom of the lubber line touching the top of the CDI as it starts moving. To keep it simple, start your base turn with a 30° intercept angle. On a Boeing aircraft it is more or less the same with the airplane symbol with the EHSI or ND in Full Compass Rose.

Or you cheat, leave it in MAP mode and use the trend vectors with the extended centreline or green dashed radial line and LNAV path.

I do love cheating

Last edited by Banana Joe; 1st Dec 2018 at 23:29.
1st Dec 2018, 15:50

Join Date: Sep 2006
Location: World citizen
Posts: 315
15 % TAS will give you std rate of turn
2nd Dec 2018, 04:02

Join Date: Feb 2000
Age: 55
Posts: 1,513
Originally Posted by dan1165
15 % TAS will give you std rate of turn
So will the rate of rate of turn indicator.
3rd Dec 2018, 02:00

Join Date: Aug 2013
Location: PA
Age: 54
Posts: 36
Radius of turn? It looks to calc about 2.5nm radius, at 4500 feet, at 170 kts (IAS) is about 12 degrees bank angle (assuming no winds)

Following the FAA/ICAO rules, with a 50 Ktw, it would be about 18 degrees bank angle.

Note: CAT C are limited to 25 degrees, CAT D are limited to 20 degrees.

(they are keeping you busy on this one!) Just calculating the two DME radials, the DME points to wildcard a turn radius...jeez 170 at 21 DME?

http://charts.portugal-vacc.org/file...PD_12-5_en.pdf

Last edited by underfire; 3rd Dec 2018 at 03:00.
3rd Dec 2018, 04:52
Gender Faculty Specialist

Join Date: Mar 2002
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TLAR to SHIG.

Nothing else.

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