Autolanding speed

[Richard McDonald Woods 168]

Gentlemen,

 

I understand that I should use flaps 30 and Vref+5 for landing, but what value should the Vref take?

 

Should I use the value shown by the INIT REF or deduct some for the consumption between setting Vref and expected landing time (in my procedure I try to set up for landing around 1 hr prior, so set for 7 tonnes less fuel)?

 

Cheers, Richard

[kevinh 409]

Gentlemen,

 

I understand that I should use flaps 30 and Vref+5 for landing, but what value should the Vref take?

 

Should I use the value shown by the INIT REF or deduct some for the consumption between setting Vref and expected landing time (in my procedure I try to set up for landing around 1 hr prior, so set for 7 tonnes less fuel)?

 

Cheers, Richard

Generally you should set up for landing after commencing descent. Fuel burn after that will be minimal. You should use the speed shown on the APPR REF page. You could do all your other planning and preparation in advance and leave Vref till later. Much better than doing it early and calculating a correction due to fuel used. If you forget to set Vref the system will prompt you to do so later on.

[kevinh 409]

Yeah, it will do so, of course, well.

 

Still.

 

Also, the NO AUTOLAND announced on PFD. That's what I meant.

NO AUTOLAND means the autopilot is not capable of autoland. At around 1500' AGL it does a series of checks to confirm status and annunciates LAND3, LAND2 or NO AUTOLAND. The flap setting at that time might not yet be the final landing flap.

 

The autopilot is capable of auto landing at flap 25, it just isn't certified to do so.

[777simmer 117]

NO AUTOLAND means the autopilot is not capable of autoland. At around 1500' AGL it does a series of checks to confirm status and annunciates LAND3, LAND2 or NO AUTOLAND. The flap setting at that time might not yet be the final landing flap.

.

Yes....so you agree with my initial thoughts that flap setting is not included in those check right?

 

I too cant remember having ever seen the NO AUTOLAND message just because of not being completely configured.

Maybe I have a few minutes later on to see what the PMDG does when you approach with flaps 25....(or even flaps5).

 

There are many things that are not warned for by the 777.

People overestimate how perfect the 777 is.......it is a great aircraft but the PIC still has to know his stuff.

That "fail safes fail safes everywhere" does not allways fly....not even with the 777!

 

Many things rely on local rules and regulations that cant be known to the 777.

For exemple the equipment that is required to fly a NAT track......if something failes there you do not get an UNABLE NAT message or something like that.

The PIC just has to know that NAT is not allowed without certain equipment and act accordingly (fly below NAT or request rerouting or land at enroute alternate).

Examples are:

2 ND

2 PFD

Autopilot

MCP panel

ADIRU

2 FMC

2 CDU

ETC..

 

Or if something of the required ground equipment for autoland fails you dont get a NO AUTOLAND message either.

Examples are:

Runway light system inop

RVR measuring system inop

ILS standby transmitter inop

 

And there is on board equiment that can fail that does not give you a NO AUTOLAND caution.The following are examples of things that do not cause the NO AUTOLAND message to show even though you (or we with our SOPs) can not do an autoland.

Flaps not at 20 or 30

Anti Skid system inop.

Auto callout function (50,30,20,10)

Auto Throttle (required for CatIIIB but not for CatIIIA)

Capt window heat

Capt windshield wipers

etc.

 

Of course we dont have to remember everything.....we just have to remember that when something failes that we look in the tables in the back of our company QRH and see if CATIII or autoland capability is effected.

The autopilot is capable of auto landing at flap 25, it just isn't certified to do so.

I am not sure if that is so.

 

You are definately correct that Autoland is only certified with flaps 20 and 30.

But capable.....or not capable.....I dont know.

 

For example in the FCTM you can read that Autoland is not certified and not recommended when overweight.

But then it mentions that in case of emergency.....if determained the safer course of action.....an autoland can be done even if overweight as long as all systems and instruments are closely monitored during the autoland.

So at least it is mentioned that this can be done.

I dont think it is mentioned anywhere that an autoland could be done (even though not recommended) with flaps 5 for example.

 

As I said previously....I dont think the NO AUTOLAND message comes for a non autoland flap setting. So rollout and flare would arm if you ask me, and the AFDS will attempt to autoland I think.

But capable in the sence of a safe landing (no structural damage...no long long flare etc)......I am not so sure about that.

Gentlemen,

 

I understand that I should use flaps 30 and Vref+5 for landing, but what value should the Vref take?

 

Should I use the value shown by the INIT REF or deduct some for the consumption between setting Vref and expected landing time (in my procedure I try to set up for landing around 1 hr prior, so set for 7 tonnes less fuel)?

 

Cheers, Richard

We allways enter the expected landing weight on the CDU APPROACH page.

This is true for normal landings (early descend preparation) but also when we have to do a non normal checklist that results for example in Vref30+15 or so. Even if we do this hours before landing.....the estimated landing weight is used.

 

I Just take a look at landing fuel (progress page) and present fuel on board.

The difference is our estimated burn till landing.

On the APPROACH page you overwrite the current weight with your estimated weight and then you select the resulting calculated Vref30.

(this weight overweight is temporary.....if you leave the APPROACH page and go back to it you will see that your actual weight is in there again, but Vref30 is still as you selected previously).

Shortly before landing (on final usually) I take a quick look if my estimated weight and Vref was correct or has changed (holding).....and update Vref (even if only 1kt different) if required..

[Richard McDonald Woods 168]

Hi Rob,

 

I shall alter my 'habit' to:

 

"I Just take a look at landing fuel (progress page) and present fuel on board. The difference is our estimated burn till landing. On the APPROACH page you overwrite the current weight with your estimated weight and then you select the resulting calculated Vref30".

 

Many thanks

[777simmer 117]

You are welcome Richard :-)

 

I guess there are different ways of doing it (company SOPs).

 

The thing that matters in the end is that you fly the correct Vref speed for your weight.

When you set it really does not matter as long as you dont forget to update Vref if required (for example if you just select the current Vref for your current weight a coule of hours before landing....lthen that is not wrong per se. But you do have to remember to update that before you land later).

[scandinavian13 5,192]

Still...in most cases where I've selected VREF at T/D, it's only changed by a knot at the most by the time I'm closer in. If you think about it, VREF increases with weight and the fuel load only decreases the weight, so if you're a knot on the high side, you're just adding distance from the stall margin. In other words, it's not unsafe to not update it, or forget it. You just might float a little bit.

 

I actually use the method Rob outlined earlier by using the PROG page to help get a more VREF, but even without it, it's generally only a knot or two off on the high side.

[777simmer 117]

Still...in most cases where I've selected VREF at T/D, it's only changed by a knot at the most by the time I'm closer in. If you think about it, VREF increases with weight and the fuel load only decreases the weight, so if you're a knot on the high side, you're just adding distance from the stall margin. In other words, it's not unsafe to not update it, or forget it. You just might float a little bit.

 

I actually use the method Rob outlined earlier by using the PROG page to help get a more VREF, but even without it, it's generally only a knot or two off on the high side.

yes correct.

 

The biggest discrepancy is usually caused by a non normal that requires fuel dumping to not land overweight. If you enter Vref at present weight as per non normal checklist and then dump fuel....then the updating becomes more important.

[Driverab330 74]

For your info, some of the latest 773ER is certified for flap 25 autoland, due to the increase use of flap 25 landing as part of the fuel saving measures. As far as I know for Cathay airplanes it starts from B-KQO, so I assume airplanes being made around the same time should have the same certification provided it is not an airline option.

 

Like Kyle had already mentioned, it's not that the airplane can't do it, it just the amount of certification work involved to get it done.

[kevinh 409]

Yes....so you agree with my initial thoughts that flap setting is not included in those check right?

 

I too cant remember having ever seen the NO AUTOLAND message just because of not being completely configured.

Maybe I have a few minutes later on to see what the PMDG does when you approach with flaps 25....(or even flaps5).

 

There are many things that are not warned for by the 777.

People overestimate how perfect the 777 is.......it is a great aircraft but the PIC still has to know his stuff.

That "fail safes fail safes everywhere" does not allways fly....not even with the 777!

 

Many things rely on local rules and regulations that cant be known to the 777.

For exemple the equipment that is required to fly a NAT track......if something failes there you do not get an UNABLE NAT message or something like that.

The PIC just has to know that NAT is not allowed without certain equipment and act accordingly (fly below NAT or request rerouting or land at enroute alternate).

Examples are:

2 ND

2 PFD

Autopilot

MCP panel

ADIRU

2 FMC

2 CDU

ETC..

 

Or if something of the required ground equipment for autoland fails you dont get a NO AUTOLAND message either.

Examples are:

Runway light system inop

RVR measuring system inop

ILS standby transmitter inop

 

And there is on board equiment that can fail that does not give you a NO AUTOLAND caution.The following are examples of things that do not cause the NO AUTOLAND message to show even though you (or we with our SOPs) can not do an autoland.

Flaps not at 20 or 30

Anti Skid system inop.

Auto callout function (50,30,20,10)

Auto Throttle (required for CatIIIB but not for CatIIIA)

Capt window heat

Capt windshield wipers

etc.

 

Of course we dont have to remember everything.....we just have to remember that when something failes that we look in the tables in the back of our company QRH and see if CATIII or autoland capability is effected.

Yes, the LAND3 logic checks the autoland system itself. Three A/Ps engaged, each with isolated power supplies. Each channel cross-checked with the others and within tolerance. Three valid independent sources for ILS and Rad Alt, etc. Things like flap setting aren't important to that logic, which is about fail operational performance. As you said, the A/P will attempt to land even with no flap.

 

Just to be sure this is how PMDG modelled it, I tried a flap 25 autoland earlier, setting flap 25 and Vref25 well before 1500' AGL. It annunciated LAND3 and landed without any problem.

 

I am not sure if that is so.

 

You are definately correct that Autoland is only certified with flaps 20 and 30.

But capable.....or not capable.....I dont know.

 

For example in the FCTM you can read that Autoland is not certified and not recommended when overweight.

But then it mentions that in case of emergency.....if determained the safer course of action.....an autoland can be done even if overweight as long as all systems and instruments are closely monitored during the autoland.

So at least it is mentioned that this can be done.

I dont think it is mentioned anywhere that an autoland could be done (even though not recommended) with flaps 5 for example.

 

As I said previously....I dont think the NO AUTOLAND message comes for a non autoland flap setting. So rollout and flare would arm if you ask me, and the AFDS will attempt to autoland I think.

But capable in the sence of a safe landing (no structural damage...no long long flare etc)......I am not so sure about that.

The autopilot is a closed loop system. As such it is self-compensating. It doesn't usually need specific control laws for a given flap configuration. So if it can autoland at flap 30 and flap 20 it's highly likely it can do it at flap 25. What hasn't been done is any certification testing to demonstrate that it performs within FAA/EASA tolerances. Hence flap 25 wasn't certified for use. According to the post before this it has now been certified on some -300ER aircraft. This is basically an economic issue. Boeing won't spend money testing both normal flap configurations if one will suffice. Now the additional certification work has done due to economic pressure. Presumably any operator who wants to use flap 25 will have to pay Boeing for the privilege. There may be an FCC software update as well (to fine tune performance as necessary).

[Michael Moe 495]

Hmm, 

 

I always get LAND 3 with Rollout and flare using Flaps 25 all though i do cutoff the A/P at 1000 feet when weather allows it.

 

Michael Moe

[Mike777 163]

Thanks to Kevin, Rob, DriverAB330 and Michael for very interesting info on why the 777 does not normally allow flaps 25 Autoland (except new -300ERs) and the best time and method for entering final approach speed.

 

Mike

[patrico 5]

ditto Mike some very valuable information

[777simmer 117]

Yeah I think this thread has become very informative as well :-)

 

Thx Kevin and DriverAB123 for your info as well!

 

 

I have another example how Boeing aircraft CAN often do more than what they are certified for.

When it comes to weight (max TOW, Max LDW,etc) it seems you are paying for all the testing that took place to certify an aircraft at hight weights.

We have 772s that are certified to land at 208T and others at 213Tons. (KG).

But they are otherwise the same aircraft.

I am pretty sure that the 208T version could be easily "upgraded" to 213T if you just pay for the certification.

[kevinh 409]

 

 

I am pretty sure that the 208T version could be easily "upgraded" to 213T if you just pay for the certification.

That is indeed all it takes. However the certification flights are a significant cost for Boeing so it's fair enough they get revenue from it.

 

This kind of thread is what makes the forum worthwhile. We all learn something new.