A/T Use in High Wind Approaches

[wde12 19]

Morning PMDG,

 

Came across an issue this past weekend and figured I would run it by the forums to see what I did wrong / what I can learn. Disclaimer: I have read the intro manuals, pulled FCOMs etc. but no Kyle, I have not dug deep into the manuals on this issue. I am at work and dont have the pdfs stored here. So, if this is something in that wheelhouse, my apologies in advance.

 

So I was flying a routine flight from KATL - EGLL this past Saturday. I had paused it and later restarted in real time early Sat am EST, meaning it was afternoon in London. To my surprise, the winds were insane. Judging by the VATSIM traffic and news stories, I'm guessing many here are aware - I believe winds were something along the lines of 40kts with gusts even higher. It was the windiest I had seen yet. I was pumped.

 

On approach to 27L, I was near fully configured just past the outer marker. I believe I was at around flaps 25 145kts give or take and selecting flaps 30. Due in part to my amateur skills, the winds, and in part to my crappy CH yoke (one screw is stripped so it detaches from the desk easily), I got above G/S. When I tried to correct, the A/T system did not respond in kind. The thrust kept appearing to increase as did my speed. This continued even after I had re-established the a/c on the G/S. I ended up touching down at a brisk 161kts, way down the runway) generating curse words from myself that ended up waking the dogs and the wife). 

 

In short, the A/T was an epic fail on this high wind approach. I watched it over and over on replay. Before the 777, I have always flown manual approaches. The MD-11 was the only a/c where I learned to incorporate the A/T system, and even with that fickle bird I flew many manual a/t approaches. So I admit, I am still uncomfortable with the A/T in general. 

 

Was this an isolated case where I simply should have called a go around? Somewhere where I clearly messed up? Any of you all experience something like this? Any insight on published protocols, or practical tips / procedures to use? Rules of thumb when to call it quits on the a/t, disengage, and go full manual? This forum is closest I got to a line captain, so if I messed up big time, lemme know. Just wanna learn.

 

William

[G550flyer 1,029]

In realworld flying, autothrottles get sloppy during gusty winds and turbulence. They are very reactive. 1st tip is to make your wind additives. 2nd is to turn the AT off. Once you find the power setting that keeps you on vref+ wind addidtives, set it and don't go too far from it. Just remember not to chase the speed like the AT does.

[Tony747-400 44]

We had terrible winds here in the UK on Friday 14th from about 22.00Z. I was listening to my air band receiver and all planes were diverting or had to perform go arounds then diverting. Aer Lingus flights from Dublin to EGLL actually were diverting back to Dublin. So in the real world pilots didn't continue with the approaches in those conditions.

[G550flyer 1,029]

In the real world, it depends on aircraft operating restrictions. During my Air Force time and current civilion ops, i've all ways been restricted to 50 kts head, 10 kts tail and 30 kts crosswind. Crosswind limit will decrease based on runway surface conditions wet, icy, etc. I've landing up to every limit. Lajes and Thule were known for winds right at the limit. High head and tail winds are not difficult, it's the crosswinds that become challenging. In all of my flying, I've only diverted due to crosswinds. Gusts make crosswinds more difficult because of the constant crosswind control adjustments. Gusts during head and tailwinds air simple as long as you properly add the additives. Tailwind gust and additives lead to more runway required due to the higher ground speeds. Most aircraft have a 20kt max additive. Gusts and turbulence as far as the autothrottles are concerned, makes them surge causing pitch instability. When i flew DC10s, the throttles would go to max fwd or aft positions when ever you are more than 5 kts off target speed. This gets very annoying. Clicking them off and finding a good power settings makes things more stable.

[scandinavian13 5,192]

 

 

Disclaimer: I have read the intro manuals, pulled FCOMs etc. but no Kyle, I have not dug deep into the manuals on this issue. I am at work and dont have the pdfs stored here. So, if this is something in that wheelhouse, my apologies in advance.

 

I defer to Rick's knowledge, but I had to post and say I laughed a bit at that.

[777simmer 117]

The 777 AT is not that bad.

Even in gusty conditions.

The lower you get and the larger speed deviations from Vref are, the faster the AT reacts. And the 777 Fly By Wire systems compensates for nose up/down tendency during that all :-)

 

Sometimes it is bit slower in its reaction than you would though, and that causes you to get below Vref sometimes (if you do nothing).

 

But in the real 777 this is not a problem.

You have your hand on the throttles anyway and with the AT of the real 777 working like the "PMDG777 Thrust levers override AT - Allways" mode you can just push/pull on them as you deem necessary. When you relax your grip, the AT keeps working.

(the AT servo motors are real light and easy to overrule).

 

In our PMDG777 most of us fly with "TL override AT - in HOLD only" which is a problem in gusty conditions because you cant do anything then.

 

So I am inclined to say that in real life I prefer to ALLWAS have the support of the AT.

But in the PMDG777 case, combined with our TL without feed back and in "override in HOLD only mode" I think in such conditions it is better to just disengage the AT from the start of the approach.

 

What to do with the AT in real life is pretty much up to the airlines SOP.

Some have the rule of AP off requires AT off.

Others allways leave the AT on.

There is no right or wrong.

 

What is ofcourse wrong, is to allow the automatic system to do something you dont want.

For example, AT adding thrust, even while above Vref, as you dive down to get back on the GS.

That looks more like a simulator screw up but if that would happen in real life you would disconnect the AT and take over.

In this case sice you were quite low already (below 1000ft I guess?) this warrents a go around. You dont dive down at that low an altitude to get back on the GS!

 

Many airlines these days have in their SOP that you have to be established from 1000ft AGL (gear down, flaps set, speed and thrust stable and set, checklist complete) or a go around shall be initiated.

 

Boeing recommends to only add wind additives when you have the AT disengaged.

With AT engaged, the additive is Vref + 5kt under all (normal, no defects) conditions.

 

Better luck next time ;-)

[re84uk 0]

If my memory serves me correct, I believe the FCOM also states that you can go with VREF +10 if the wind is particularly strong.

[Boeing or not going 578]

And land with flaps 20 or 25.

[EGLL77W 1,508]

And land with flaps 20 or 25.

 

Flap 20 is a non-normal landing flap only. 25 is the minimum. 

 

Rob pretty much cleared it up. I've started using the "Override ALWAYS" option and now prefer it. 

[scandinavian13 5,192]

Flap 20 is a non-normal landing flap only. 25 is the minimum. 

 

Rob pretty much cleared it up. I've started using the "Override ALWAYS" option and now prefer it. 

 

25 is the minimum normal flap.  You could land flap 5 in the 777 if you wanted to (not that it would be particularly smart).

 

Very high, gusty winds could definitely be a non-normal situation.  I may be wrong, because I'm no Piper guy, but I believe the PA28 calls for 40 for all landings.  If it's gusty, I'm surely not leaving 40 degrees of flap out there for the gusts to play with.

 

I think a lot of people associate non-normals with emergencies because they're handled by the same book of checklists.

[777 340]

Just to add...... does the A/P - A/T have a limit within it can operate??? In regards to wind speeds???

[johnsturm 22]

Any time you are interesed in finding information about aircraft limitations, the appropriately named "Limitations" section of FCOMv1 is a good place to start.

 

As far as I know there is no wind limitation on a/p - a/t use. There is an operating limitation for a maximum takeoff and landing tailwind component of 15 knots. See FCOMv1 pg 179.

 

There are also limitations on wind speeds for automatic landings on FCOMv1 pg 184:

Headwind 25 knots

Tailwind 15 knots

Crosswind 25 knots

 

These limitations are recommendations by Boeing, individual opeators can have a company SOP that adjusts these limitations.

[IAF747 8]

If I am PF I disconnect AT if doing a manual land which is often.

 

If you don't have manual control over the AT you might as well be doing an auto land.

 

You need the throttles to help you control your descent path.

 

I think the passengers on your flight must have experienced some uncomfortable Gs if you were going too fast and got the a/c back on GS.

 

YPPH is one of the windiest airports in the world and constant corrections are needed because of the many variables.

 

If you are lazy and landing in no or light winds then you could get away with AT on landing but it has caused more problems than it has solved.

 

Automation is nice but it also creates many hazards that often are not thought of beforehand.

 

A basic principle of flight must be reiterated here:

 

Control your GS with throttles(power) and control your speed with attitude(elevators).

[g_precentralis 191]

Flap 20 is a non-normal landing flap only. 25 is the minimum. 

 

Rob pretty much cleared it up. I've started using the "Override ALWAYS" option and now prefer it. 

How that works for you assuming you do not have motored levers?

[777 340]

Any time you are interesed in finding information about aircraft limitations, the appropriately named "Limitations" section of FCOMv1 is a good place to start.

 

As far as I know there is no wind limitation on a/p - a/t use. There is an operating limitation for a maximum takeoff and landing tailwind component of 15 knots. See FCOMv1 pg 179.

 

There are also limitations on wind speeds for automatic landings on FCOMv1 pg 184:

Headwind 25 knots

Tailwind 15 knots

Crosswind 25 knots

 

These limitations are recommendations by Boeing, individual opeators can have a company SOP that adjusts these limitations.

 

Thanks for the info - im a manual lander/ taker-offer lol, never knew flaps 20 was non-normal ...good to know these limitations...