Hi Everyone,

 

I've got a question that I'm hoping someone with real-world experience flying the 737NG's might be able to answer.

 

Should the A/P and A/T be disconnected upon reaching minimums or as soon as the runway is in sight?

 

Thanks.

Disconnect it when ever you feel like hand flying even before runway in sight, most pilots like to hand fly and with the HGS you can even hand fly cat III condition approaches if you wish.

That depends on a couple of things including company limitations, aircraft limitations (listed in the Limitations chapter of the FCOM), the type of approach you're flying and your workload.

 

A good rule of thumb is to have both disconnected at any time in the approach, but before stable altitude (1,000ft RA/500ft RA) or before the minima for the runway on which you intend to land.

 

The decision is ultimately yours, but it must be done before the specified limit(s).

 

Michael McKenna.

OK thanks for that. I usually disconnect both at around 1000ft RA or less but I was a bit confused as chapter 5 in the FCTM seems to indicate that A/P and A/T are disconnected at DA(H) or MDA(H) for approaches using VNAV which I normally use.

You can even hand fly cat III condition approaches if you wish.

 

I don't want to put words in your mouth, so can you elaborate on that please?

 

Bert Van Bulck

I don't want to put words in your mouth, so can you elaborate on that please?

 

Bert Van Bulck

 

With the HGS (you left it out of the quote)

 

http://www.rockwellc...nce_System.aspx

AS does Cat 3A with AIII HUD hand flown to 50ft.

OK thanks for that. I usually disconnect both at around 1000ft RA or less but I was a bit confused as chapter 5 in the FCTM seems to indicate that A/P and A/T are disconnected at DA(H) or MDA(H) for approaches using VNAV which I normally use.

 

I would venture a guess that this should be interpreted as "at latest" disconnection, not "precisely now".

Should the A/P and A/T be disconnected upon reaching minimums or as soon as the runway is in sight?

Whether or not it is OK to disconnect at the minimum depends on the very altitude or hight of that minimum. Imagine disconnecting at a CAT I minimum of 200ft, this would be way too late as it is difficult to get a "feel" for the aircraft in the time remaining. This might work in still air, but is quite difficult with gusty or turbulent weather.

Now obviously if your MDA is between 500 and 1000ft AGL then things look much better.

 

Disconnect rather sooner than later, especially if you need to get some practice for hand flying. There are different SOPs with airlines or even aircraft types. Some state that AT MUST be off whenever AP is off during approach, others say that the use of AT is required whenever possible. So you may construct your own SOP on that ;) However AT off when AP is off is the best method to get good practice.

And remember, when landing a big airliner the idea is to find the right thrust setting when at full flaps so that you don't have to touch the throttles anymore until over threshold. Or in other words, having the numbers in your head for how many % N1 you need (approx.) at which weight and flap setting to maintain Vapp... This helps a lot!

 

Cheers,

Markus

Disconnect rather sooner than later, especially if you need to get some practice for hand flying. There are different SOPs with airlines or even aircraft types. Some state that AT MUST be off whenever AP is off during approach, others say that the use of AT is required whenever possible. So you may construct your own SOP on that ;) However AT off when AP is off is the best method to get good practice.

 

I tend to always disconnect both A/T and A/P as I've also read that this is the best way to do things. It also makes it easier when reducing to idle and flaring as I don't have to worry about disconnecting it then.

 

And remember, when landing a big airliner the idea is to find the right thrust setting when at full flaps so that you don't have to touch the throttles anymore until over threshold. Or in other words, having the numbers in your head for how many % N1 you need (approx.) at which weight and flap setting to maintain Vapp... This helps a lot!

 

Great advice! I tend to sometimes find myself battling with the throttles to maintain speed especially when the winds make it a bit more challenging.