Sign in to follow this  
CaptainLars

Approach Minima: Baro or Radio?

Recommended Posts

Hi,

 

the title says it all: When would I use minima as altimeter, and when as height? The Approach Plates indicate barometric minima in bold letters and radio minima in brackets behind and I always ask myself, "what do I use now", and usually I end up using barometric minima. How is it done correctly?

 

Thank you very much!

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Precision Approach = Decision Height = Radio

Non-Precision Approach = Minimum Descent Altitude = Baro

 

The brackets figure on Baro minimums is just your equivalent height AGL.

MDA is "don't go below unless visual"

DH is lowest height to commence go round if visibility does not satisfy minimums

  • Upvote 1

Share this post


Link to post
Share on other sites

Generally you would want to use baro unless noted on the chart.  Usually CAT II and III approaches will use RA because you’ll already be over the runway environment by the time you reach the minimums.  

 

Using RA on a CAT I has the potential to have you descend lower than what’s safe if the airport sits on a plateau or has terrain that sits much lower on approach than the airport.

Share this post


Link to post
Share on other sites

Using RA on a CAT I has the potential to have you descend lower than what’s safe if the airport sits on a plateau or has terrain that sits much lower on approach than the airport.

 

Can you give such an example? A Cat 1 ILS is a precision approach and uses RA

Share this post


Link to post
Share on other sites

Can you give such an example? A Cat 1 ILS is a precision approach and uses RA

 

It doesn't, actually.

 

You only use RA where the approach plate states "RA."

 

While this approach provides an "RA-like metric" in the "200," it's simply letting you know that the min of 512 happens to be 200 AGL:

http://155.178.201.160/d-tpp/1612/05100IL1R.PDF

 

This approach, on the other hand, specifies RA in the metric, so you use radio alt. Note that in this case, DA is provided to let you know that the DH of 94 will put you at 412 MSL. Note the variation of 6' between the DA, and reference DH vs TDZE. This iswhy you do not substitute them for each other. While in this case the variance is only 6', imagine the variance between the runway data plane (based off of the TDZE) and the reading somewhere like KSEZ, which is on a plateau. If it had an ILS, and you flew it to RA mins...

"Tonight! At 11..."

 

http://155.178.201.160/d-tpp/1612/05100I1RC2_3.PDF

(Note the "RA" clearly stated.)

  • Upvote 1

Share this post


Link to post
Share on other sites

I always thought that the number in brackets would be RA! But now I know it's AGL.

 

So it's either RA, and then it is explicitly stated, and if not, it is Baro. Thank you very much for your insights.

Share this post


Link to post
Share on other sites

 

 


So it's either RA, and then it is explicitly stated, and if not, it is Baro. Thank you very much for your insights.

 

Welcome!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this