Jump to content

Sign in to follow this  

Decision height

Recommended Posts

HiI have recently been learning more and more about flying different aircraft, different types of approaches etc. With the PMDG 737 series there are two options when setting the decision height, barometric and Radio. How do I know which one to set for the decision height and what is the difference between the two?Thanks

Share this post

Link to post

This is a good source of info: http://www.faa.gov/library/manuals/aviatio...lying_handbook/Depends on your approach... you can shoot a normal precision approach (CAT I ILS) with baro minimums, but I think the required equipment for a CAT II/III includes radar altitude and you use it per the charted approach. I'm not certified for these so I'm just making a qualifed guess.The difference is two-fold. The baro reading would agree with the radar only if the terrain on final maintained the same elevation as the landing zone; secondly, the radar is much more accurate than the baro.

Dan Downs KCRP

Share this post

Link to post

For CAT I approach, Desision Altitude (DA) is referenced to MSL height and determined by the BARO altimter, refer to the approach plate. The 737NG is certifided for CAT II/IIIA approaches using Decision Height (DH). Set the desision height using the RADIO MINS selector on the EFIS control panel. All CAT IIIa approaches must use autoland in normal ops. CAT II is not an autoland.For CAT II (DH), set approach plate minimums or 100' (which ever is higher) RAIDO MINS. For CAT IIIA (DH), always set 50' RADIO MINS.Good luck,John Floyd

John Floyd

Share this post

Link to post

Mr. Floyd is correct. The mins selector is set to BARO for ILS CAT I and all Non-ILS approaches. The mins selector is set to RADIO for CAT II and CAT III approaches. Many 737 operators use HUD for approaches below CAT I mins. I know of one airline where the autopilot must be disengaged by 1000'AFL and mins selector set to 50ft for a HUDCAT III approach. The approach is hand flown. For airlines that dont use HUD, CAT II approaches can be autoland or autopilot used to DH then disconnected. Some airlines reccomend autoland for CAT II but its not required. And as John said, CAT IIIa without HUD must be an autoland. Fail Operational approach is an option for the B737ng. In this case, the aircraft is certified to CAT IIIb approaches with an Alert height of 100' agl. In this case, set the mins selector to 100'. Maybe the new PMDG 737 will have HUD or fail operational autopilot as options.A. Cole

Share this post

Link to post

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  
  • Tom Allensworth,
    Founder of AVSIM Online

  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.

    $540.00 of $25,000.00 Donate Now
  • Create New...