AS Next with 777

[abbaabb 0]

Hey guys, anyone noticed how AutoThrottle works during turbulence on the approach phase? I have to disengage it and operate thrust levers manually. If not, than it's impossible to reach Vref. AT holds ~Vref+30kt. 

Any thoughts of it? Wondering how it happens in real life with AT of 772 

[Don t moderate me this way 882]

The T7 will not slow down to Vref on automation.

 

You have to speed-intervene, with A/T engaged, just like in the real thing.

[Knippi 0]

Have you set the speed to VREF+5 in the MCP but AT holds the speed at at VREF+30?

I believe this is some kind of safety feature in the AT to prevent the plane from low IAS due to changing wind speeds.

[willultra99 8]

If the throttle is in hold mode on your PFD the engines will only throttle back or ahead to where your throttle is positioned. I had a problem with slowing the plane down but when I looked into it it would descend in hold mode and where ever I had my throttles located that would be as far as the engines would throttle back. Could never get the plane down in time.

[FLEX1978 373]

If the throttle is in hold mode on your PFD the engines will only throttle back or ahead to where your throttle is positioned. I had a problem with slowing the plane down but when I looked into it it would descend in hold mode and where ever I had my throttles located that would be as far as the engines would throttle back. Could never get the plane down in time.

 That shouldn't happen (in the sim) unless you actually move your throttle.  At TOD for example, I can leave my physical throttle in the forward range, once HOLD engages the A/T will still go to IDLE.

 

One of the options in the PMDG FMC setup menu will activate that behavior.  Anyway, always a good idea to move your throttle to match the A/T movement during large power changes.

 

@Nameless  I was practicing Missed approaches due to ASN windshear a few day's ago.  A/T was struggling but still maintained Vref+5 

 

Regards

[abbaabb 0]

olli4740, it slows down when it's calm

 

Knippi, exactly. Seems like safety feature indeed. As olli4740 said we have to speed-intervene but anyway +30kt seems a lot to me. 

[FLEX1978 373]

So what is the target speed on the PFD? Vref+5?  Are you saying the engines are spooling to maintain Vref+30 even though target seed is Vref+5?

 

That is not a safety feature...

 

The safety feature is low speed  A/T wake up

[abbaabb 0]

So what is the target speed on the PFD? Vref+5?  Are you saying the engines are spooling to maintain Vref+30 even though target seed is Vref+5?

 

That is not a safety feature...

 

The safety feature is low speed  A/T wake up

Yes  but only when the turbulence exists. When it's calm AT holds Vref+5 perfectly 

[FLEX1978 373]

Yes  but only when the turbulence exists. When it's calm AT holds Vref+5 perfectly 

 

In this case it seems like you should post a video or screenshot's. As mentioned I have been flying approaches in pretty dodgy weather using ASN.

 

btw, stick your name at the bottom of the post. Will avoid having this topic deleted by the forum staff.

 

Cheers

[Knippi 0]

 

 

Yes but only when the turbulence exists. When it's calm AT holds Vref+5 perfectly

 

Yes.

 

On approaches with gusting winds and turbulences AT quickly increases thrust and slowly decreases.

So the speed is higher than the speed set in the MCP.

 

I don't use AT that much on approaches, so I have seen this case maybe 3 or 4 times.

[Don t moderate me this way 882]

I agree with Sebastian here: Your "average thrust" will be higher in turbulence.

 

But I've never witnessed an approach speed increased by 25 kts ... (30 kts minus 5 kts, on top of Vref)

[FLEX1978 373]

Yes.

 

On approaches with gusting winds and turbulences AT quickly increases thrust and slowly decreases.

So the speed is higher than the speed set in the MCP.

 

I don't use AT that much on approaches, so I have seen this case maybe 3 or 4 times.

GS MINI exists on the Airbus, nothing like that exists on Boeing aircraft.  A/T will react to gusts but it 'wont' increase and hold Vref+30 on the glide slope.  The A/T on the 777 is designed to stay on from TOGA push right down to landing.

 

Something else is up with the op's setup. this has nothing to do with the real aircraft.  

 

Do you really think Boeing would design an A/T system that lands way above Vref? Your landing performance data would be meaningless.

 

Regards

[abbaabb 0]

I'll try to make a video. Hope i'll catch this moment  :Whistle:

 

Rob, thanks for a hint with the name  :im Not Worthy:

[Knippi 0]

 

 

The A/T on the 777 is designed to stay on from TOGA push right down to landing.

 

I know, but it's more fun to fly approaches manual.

[abbaabb 0]

Ok guys, i've made it. This time Vref was fluctuating between  +15-30kt.