Alert Height question on B737 NG

[tae9141]

Hello Everyone,

I just finished off my CAT2/3 checkout on simulator session and still getting things mixed up on usage of alert height.
I tried to look up on FCOM and saw explanation on Fail passive system specific to our company's 737 model and it was so clear. However in what ways could I confirm that I can use alert height on B737 NGs if not, then the phrase stating 'not allowed to use alert height' ?

Also, the planes is manufactured and certified in U.S. so that is why the alert height applied to 737 worldwide because of its origin?

I also checked out the AC120 on CAT2/3 approaches and I am not sure where to find out the reference on those mentioned above.

[aterpster]

Hello Everyone,

I just finished off my CAT2/3 checkout on simulator session and still getting things mixed up on usage of alert height.
I tried to look up on FCOM and saw explanation on Fail passive system specific to our company's 737 model and it was so clear. However in what ways could I confirm that I can use alert height on B737 NGs if not, then the phrase stating 'not allowed to use alert height' ?

Also, the planes is manufactured and certified in U.S. so that is why the alert height applied to 737 worldwide because of its origin?

I also checked out the AC120 on CAT2/3 approaches and I am not sure where to find out the reference on those mentioned above.
I don't know anything about the 737, but on the two airplanes I flew that had auto-land, the system had to be fail active to use alert height. If it was degraded to fail passive than decision height was required.

[FlyingStone]

Alert height only applies to fail operational aircraft and it is 200ft on so equipped B737NGs. Your FCOM should tell you whether the aircraft in your company are fail operational.

There's some good content in FCTM on this topic, suggest you have a look.

[Tomaski]

In another thread, you asked about HUD Cat 3 operations. The HUD is a fail-passive system and as such does not use an alert height, only a decision height. Some operators use a dual autopilot autoland system which is fail-operative, and their alert height would be defined by their op specs. One does not mix HUD and dual autopilot procedures during a Cat 3.

Thus the answer to your question is really airline specific. If you are currently employed by a 737 operator, ask your training department. If you are looking to get hired by a 737 operator, they will let you know what procedures they use.

[ImbracableCrunk]

One does not mix HUD and dual autopilot procedures during a Cat 3.


One does. Including this one. 50'DH with HUD or Autoland but 30' with Hybrid.

[Tomaski]

One does. Including this one. 50'DH with HUD or Autoland but 30' with Hybrid.

I stand corrected. Just curious, what is the procedure if the HUD fails inside the FAF but before DH?