Ask The Pilot

[Wingin..it]

Diverting the topic a bit but the 787-9 has the raked wings like the 777.Do they have an advantage (handling etc )over the winglet? Thanks for any comments if a silly question .

 

[Boris spatsky]

RAM, I don't think I see a question there...what would you like me to comment on?

In relation to EK521 and go arounds, is it something forefront in your mind during landing or does it stay toward the back of your mind? To give context to my question, i'm thinking about the at least 12 seconds (i think) of time from the GA call to throttles being pushed forward.

I'm no doubt being simplistic in my thoughts here as i have no idea the amount of information to process when landing a 777 (or any large commercial) but I would think that a GA would always be a very real possibility and i personally would be ready with those thoughts especially if i wasn't the flying pilot.

As always, look forward to and thank you for your insight!!

We have a designated touchdown zone; if you land outside it you are required to go around provided that reverse thrust has not been selected. On top of that, below 1000 feet there are a number of criteria to meet such as rate of descent limits, speed bands and tracking - outside of these limits below 1000 feet, you are also required to go around. So yes, it is generally considered throughout the landing.

 

[andmiz]

We have a designated touchdown zone; if you land outside it you are required to go around provided that reverse thrust has not been selected.

Alternatively, full reverse thrust and max braking should be used if landing if landing long. I believe the RAAS "landing long" calls that they received didn't necessarily mean they had to go-around but that could vary between operators.

Diverting the topic a bit but the 787-9 has the raked wings like the 777.Do they have an advantage (handling etc )over the winglet? Thanks for any comments if a silly question .

In essence, winglets are quite efficient in the climb, and while reducing wingtip drag, at high angles of attack such as during climb they also assist in producing 'some' lift. Implemented over short haul routes, the benefit by having an improved climb instead of a more efficient cruise makes sense to the coneheads designing this stuff.
On the other hand, raked wingtips don't improve lift, but minimise wingtip drag by moving it further outboard along the wing, which helps improve the efficiency of long cruise segments and more suitable for long haul aircraft.

So both designs reduce drag, but in different ways, making their application more specific to the range the aircraft is designed for. The winglet on the A350 is probably the closest hybrid between the two designs. We've got a raked supercritical wing on the 747-8 (similar to the 777's), and it's very impressive and performs noticeably different to the wing design from the 747-400 which has winglets.

 

[Skyring]

We have a designated touchdown zone; if you land outside it you are required to go around provided that reverse thrust has not been selected. On top of that, below 1000 feet there are a number of criteria to meet such as rate of descent limits, speed bands and tracking - outside of these limits below 1000 feet, you are also required to go around. So yes, it is generally considered throughout the landing.

This may be the wrong audience to ask, but all this talk of numbers and limits makes me think that we're getting ever closer to autonomous aircraft. In military drone applications, the pilots for quite large aircraft are remotely located.

Are we going to see Boeing or Airbus come out with a robot cargo plane that has zero onboard crew, do you think?

 

[jb747]

This may be the wrong audience to ask, but all this talk of numbers and limits makes me think that we're getting ever closer to autonomous aircraft. In military drone applications, the pilots for quite large aircraft are remotely located.

Are we going to see Boeing or Airbus come out with a robot cargo plane that has zero onboard crew, do you think?

At some point the technology will become reliable enough. It is nowhere near that right now. Firstly you have to assume that the programmers will make no errors (!), and secondly, that they'll think of everything (!!).

The problem is that you hear of events that are described as pilot error, and so the assumption is that you could reduce the overall incidence by reducing the pilots' input. But, every day there would be thousands of events around the world where the automatics run amok, and it's simply fixed by the pilots. If you stopped those fixes, it would start raining aluminium.

 

[jb747]

Every take off is a potential abort, and every landing a potential go around. It's not over until you're at the terminal.

 

[RAM]

RAM, I don't think I see a question there...what would you like me to comment on?

No, no question.

Providing some answers to previously asked questions that you and others replied to with words to the effect, "We won't know until we see what the investigation reveals."

 

[jb747]

It has certainly confirmed some of the theories that we held. There was just no way that, given the conditions, a 777 wouldn't have had enough power to fly away. It should have been able to do so with an engine out.

 

[Wingin..it]

At some point the technology will become reliable enough. It is nowhere near that right now. Firstly you have to assume that the programmers will make no errors (!), and secondly, that they'll think of everything (!!).

The problem is that you hear of events that are described as pilot error, and so the assumption is that you could reduce the overall incidence by reducing the pilots' input. But, every day there would be thousands of events around the world where the automatics run amok, and it's simply fixed by the pilots. If you stopped those fixes, it would start raining aluminium.

I think the supposed pilot error can often be changes with lack of communication etc.Also on ground mistakes ie/fuel mixups etc and inadequate training when sudden changes come in .Would this be right?So pilot error can be other human error down the line as well.
Don't think I would be keen on a unpiloted A/C no matter how technological.

 

[petercr]

JB, having watched City in the Sky and Airport Dubai, I notice that the fuselage around the horizontal stabilizer seems to curve inwards slightly in both the horizontal and vertical planes. Is this an aerodynamic feature designed to keep the airflow 'sticking' to it as it approaches and goes over/under the stabilizers?

 

[jb747]

JB, having watched City in the Sky and Airport Dubai, I notice that the fuselage around the horizontal stabilizer seems to curve inwards slightly in both the horizontal and vertical planes. Is this an aerodynamic feature designed to keep the airflow 'sticking' to it as it approaches and goes over/under the stabilizers?

You mean the flat section in front of the A380 horizontal stab leading edge? I think that's just a mechanical issue. That leading edge can move up and down a few feet as the trim is changed.

 

[petercr]

Thanks JB, that's it - possibly just appears to be curved inwards relative to the outward curve of the fuselage. What you describe would also explain why it appears to be unpainted in some instances.

https://upload.wikimedia.org/wikipedia/commons/d/d1/A380-tail.JPG

(the area that looks a slightly different shade of white to the rest)

 

[jb747]

Thanks JB, that's it - possibly just appears to be curved inwards relative to the outward curve of the fuselage. What you describe would also explain why it appears to be unpainted in some instances.

https://upload.wikimedia.org/wikipedia/commons/d/d1/A380-tail.JPG

(the area that looks a slightly different shade of white to the rest)

The grey area at the back is actually fillers fitted to the tailplane, that move with it to fill in the huge holes that would otherwise exist. The greyish section in front is where the leading edge may move. The overall shape behind will be a structural issue...need an engineer to explain that.

 

[jasejman2000]

Whoot. After a couple of years reading your wonderful posts and explanations I get to fly with you on the 21st.

 

[Tortuga]

Can an A380 perform a move like this safely? What is stopping the plane from stalling with such a high angle of attack?

https://www.youtube.com/watch?v=FxmFfq3w8pM

 

[straitman]

Can an A380 perform a move like this safely? What is stopping the plane from stalling with such a high angle of attack?

https://www.youtube.com/watch?v=FxmFfq3w8pM

I fear you are mixing up aircraft pitch angle with angle of attack.

 

[Major]

There was an incident earlier this year where an incorrect flaps setting was selected during a landing.

Incident: Wizz A320 at Sofia on Jan 3rd 2016, inadvertently retracted flaps on final approach

Is this an example of design automatics overruling the pilot's ability to actually fly the aircraft after a problem or is it something else ?

Hungary's KBSZ reported that initial investigation results suggest, that due to the selection of flaps 0 the Go Around Mode was no longer armed, the Flight Directors therefore still were following the LOC and Glidepath indications with the active mode still being APPROACH. This had resulted in automatic thrust setting at IDLE thrust​

 

[jb747]

Can an A380 perform a move like this safely? What is stopping the plane from stalling with such a high angle of attack?

https://www.youtube.com/watch?v=FxmFfq3w8pM

Firstly he's very light. Almost certainly accelerates for longer than necessary on the runway, so he has some excess speed. The lens is quite long, so there's an element of foreshortening, which makes it difficult to work out the actual pitch attitude...my guess is about 45º. Perhaps more, but nowhere near vertical.

The pitch attitude is the attitude in relation to the surface of the earth. The angle of attack is the attitude in relation to the airflow. The aircraft is fly by wire, and would have some form of angle of attack protection. So he pulls up, the angle of attack will increase as the speed is lost, than then he pitches down whilst sitting more or less on the AoA limit.

The 380 is limited to 30º pitch up, but, if AB were to remove that limit, it would be able to do something similar, though probably not quite as extreme.

If you do a search on the net you can find a video of a C17 doing similar...but it eventually goes wrong.

 

[jb747]

There was an incident earlier this year where an incorrect flaps setting was selected during a landing.

Incident: Wizz A320 at Sofia on Jan 3rd 2016, inadvertently retracted flaps on final approach

Is this an example of design automatics overruling the pilot's ability to actually fly the aircraft after a problem or is it something else ?

Hungary's KBSZ reported that initial investigation results suggest, that due to the selection of flaps 0 the Go Around Mode was no longer armed, the Flight Directors therefore still were following the LOC and Glidepath indications with the active mode still being APPROACH. This had resulted in automatic thrust setting at IDLE thrust​

It's an interesting read. I wonder about the bloke in the right hand seat. He's moved the flap lever in the wrong direction twice, and there's a stop he's had to overcome along the way.

99% of the time when TO/GA is selected, you're either on the ground taking off, or on an approach, with some level of flap extended. In those cases, the thrust will be TO/GA, and the autopilot/flight director pitch mode with be SRS (speed reference system). Basically it gives you a pitch attitude to control the speed at whatever it is at the moment. In this instance though, because go around mode wasn't armed by the flap position, the system hasn't gone to SRS, but has instead remained in approach mode. The F/D commands would all have been related to staying on the glide slope. The power would have remained in TO/GA until the levers were moved back to climb, at which point it would have reduced to try to get the approach speed. So that's why the reduction to idle. In the meantime, I'm not sure what pitch target is being used, as the F/D would have been commanding 'down' to get back on the slope. Presumably he was ignoring that and holding a go around attitude. Pulling 'open climb' would have solved the issue, and so would turning off the F/D, or the A/T.

The automatics have actually done what they are supposed to, but they've not been forced into the correct mode. The issue, I guess, is that sometimes they behave in unexpected ways, especially when it's going off the rails. Jetstar did something similar in Melbourne a few years ago, and it got very messy.

Some of the discussion about the EK 777 has been about some possible similar A/T behaviour.

 

[Himeno]

Can an A380 perform a move like this safely? What is stopping the plane from stalling with such a high angle of attack?

https://www.youtube.com/watch?v=FxmFfq3w8pM

That's something Boeing tends to do for airshows.
https://www.youtube.com/watch?v=rgEsdHO94pI shows clips of NH and VN 787s doing similar (before delivery to the airline) while practicing for an airshow.
https://www.youtube.com/watch?v=jLPCqFC1IJ0
https://www.youtube.com/watch?v=GZRKm6PG918