VOR Station at 5000ft or Above!

[New on NG]

Hello Everybody.

I´ve been told that you cannot fly with autopilot in VOR/LOC mode ENGAGED in a B-737-300 when the station selected is at or above 5000ft MSL. Two questions : Is it true and if it is, where is it written ?? Vol. I, II FCTM or somewhere eslse??? Thanks in advance!!!!

[LEM]

I remember such a limitation " Don't use VOR for a flight director APPROACH if the station elevation is higher than 5000ft and there is no co-located DME" .

I'm really pi**ed off I couldn't find it in the 737 books, so I suspect we are confusing with another airplane!

Let me know if you find the answer, I promise not to forget looking for it... :ugh:

[New on NG]

Thanks LEM!!! i SEARCHED ALL MY MANUALS OF THE B-737-300 AS WELL AND COULD NOT FIND ANITHING. MY SUSPECTS ARE ALSO THAT I AM READ IT ON 737-200 MANUALS. HOWEVER I´M STILL WAITING OK???

I forgot to mention the reason of my question. We have a flight to La Paz 13100ft above sea level and the procedure starts over vor paz at 18000ft and we are suposed to fly manually all the way to touchdown.

[LEM]

Hi New on NG.

Found it!!!!!!!!!!!!

You are right, I was so mad at not being able to remember where I had seen that limitation, that I forgot to check in my -200 manuals!

It's not in the limitations, but in the Supplementary Normal Procedures, Automatic flight, Non precision approach:

Except as noted, do not use the VOR/LOC AFDS mode when conducting VOR approaches if any of the following conditions exist:
No co-located DME transmitter available at the VOR station to be used or when the DME is invalid for any other reason.
The VOR/DME station elevation is more than 5000 feet MSL.

Then they add that these problems exist only if you are gonna overfly the station during the approach.


Problem (and headache) solved!

Happy landing with the mask on in La Paz!

:ok: LEM

[New on NG]

OUTSTANDING!!!!!!!!!!!!!!

[LEM]

:O :O :O

I must apologize, I found the same note (not really a limitation) in the -300 Supplementary Procedures - Automatic Flight (SP.4.6).

I definitely need new spectacles :ugh: :{

[New on NG]

LEM, I really appreciated your effort. I have one more question: Why one cannot fly with AFDS engaged in VOR/LOC mode when the station is at or above 5000ft?:oh:

[LEM]

I've got no idea.

I can only guess, but my guess could be total rubbish: I can only think of the increased TAS (roughly 2% every 1000 feet) for the same approach IAS, that might make the capture and tracking function not accurate enough for a critical phase of flight.



Now it's my turn to ask you something:

why are you required to hand fly the whole approach into La Paz?

LEM

[New on NG]

I explain: we have a flight to La Paz and we must have to comply wiht a operations bulletin that states that a pilot must hand fly after we pass over PAZ vor and, like it is written in the manual manually fly the airplane if there is NO DME CO-LOCATED. And PAZ VOR DO HAVE DME. That´s what i am trying to prove.

[LEM]

it is written in the manual manually fly the airplane if there is NO DME CO-LOCATED.

Hi, New on NG, I think when they say "do not use the VOR/LOC AFDS mode " they mean do not arm VOR/LOC mode.

That doesn't mean you have to fly manually.

You can still fly with autopilot ON and track your radial in heading mode, as if it were an NDB approach, or you can track LNAV (in this case one of the pilots must monitor Raw data, if update 10 is not loaded in the FMC).

What d'you think?

[New on NG]

Hello LEM!!! Sorry for the delay. I really appreciated your words. I think that is about autopilot certification at high altitudes inside an approach procedure. It´s just a guess ok?? Best regards.

[LstCnt]

A
gree with LEM , may use autopliot in HDG mode ANYTIME!