Ask The Pilot

[simongr]

And, in the case of the 380 in particular, the aircraft was always quite a bit heavier than what Airbus had wanted/promised, so there is an ongoing weight reduction process happening on the manufacturing line. Having said that, in service aircraft tend to get heavier with time.

Like the rest of us...

 

[MichaelD]

Firstly, thank you for an awesome thread - my favourite here on AFF.

I would like to know what the things that hang down from the wings of some aircraft are - marked by arrows in the photo below of an A320.

 

[The Rok]

Those are wing spoilers, only fitted to the AMG models.....

 

[el_rooto]

All aircraft have weight variations. In fact I recall a comment from the bloke who was responsible for the 747-400 initial deliveries, to the effect that "all of them were the same, until we got OJB".

There are tolerances in everything. Whilst they might be pretty narrow in the more important engineering areas, they will be dramatically less so in items like cabin fittings. So, whilst there will be swings and roundabouts in what items weigh, the end result will never give you the same total weight...even variation in paint thickness will give a measurable result at the end.

The aircraft themselves have different equipment in them. Not just from orders with slightly different options, but the boxes themselves tend to vary as the makers find better or cheaper ways to make things.

And, in the case of the 380 in particular, the aircraft was always quite a bit heavier than what Airbus had wanted/promised, so there is an ongoing weight reduction process happening on the manufacturing line. Having said that, in service aircraft tend to get heavier with time.

Car manufacturers have this sort of thing down to a fine art, but I'll bet that if you take two ostensibly identical cars and weigh them, there will be some level of variation...and they get to make millions of the things, not a paltry few hundred like the aircraft makers.

Are the A380's that QF has taken delivery of from different blocks? EG is there a major revision/update between any of them? Are the later (and I'd assume lighter) ones used on the trans pacific routes and the heavier ones on the kangaroo routes?

 

[jb747]

I would like to know what the things that hang down from the wings of some aircraft are - marked by arrows in the photo below of an A320.

Flap fairings. They normally contain the flap actuators. The flaps both bend downwards (to increase the wing curvature) and also extend backwards (to increase the area). The fairings just contain the drives to make that possible. The outer shells are only there for cosmetic and aerodynamic reasons, and it's quite possible to take the aircraft flying without them.

 

[jb747]

Are the A380's that QF has taken delivery of from different blocks? EG is there a major revision/update between any of them? Are the later (and I'd assume lighter) ones used on the trans pacific routes and the heavier ones on the kangaroo routes?

As far as I know, there are no major differences between the aircraft. There are slight differences between them, though as so much of the aircraft is software, the others tend to eventually catch up.

At this point, any of them can be used anywhere. There are simply too few to try to keep them on any particular route.

Actually, they all have differences in fuel burn anyway (from about .5 to almost 3%) above the book figure, so if you were really trying for max range use, then that would be a more important item to consider. If we ever get Dallas (a rumour we are spreading to worry the 400 guys), then that would almost certainly be part of the planning.

 

[el_rooto]

As far as I know, there are no major differences between the aircraft. There are slight differences between them, though as so much of the aircraft is software, the others tend to eventually catch up.

At this point, any of them can be used anywhere. There are simply too few to try to keep them on any particular route.

Actually, they all have differences in fuel burn anyway (from about .5 to almost 3%) above the book figure, so if you were really trying for max range use, then that would be a more important item to consider. If we ever get Dallas (a rumour we are spreading to worry the 400 guys), then that would almost certainly be part of the planning.

Could the 380 do DFW - SYD with a full pax load?

 

[simongr]

Are any of the differences noticeable to pax?

 

[el_rooto]

Are any of the differences noticeable to pax?

On one of them at least.

 

[jb747]

Could the 380 do DFW - SYD with a full pax load?

That's asking how long is a piece of string. Rough numbers say that it could.

 

[richie9x]

On the subject of A380s and weight, a few weeks ago I saw a BBC documentary called 'How to build a Super Jumbo Wing' BBC Two - How to Build..., Series 2, A Super Jumbo Wing
If anyone gets the chance to see I would recommend it as it was very interesting.

One bit it covered was how they were trying to reduce weight. I think they took 80kgs of the landing gear. It showed them testing to make sure the gravity drop still worked as expected with the lighter landing gear.

Also they were taking some weight out of the structure of the wing while still maintaining the strength. Only little bits here and there. They weighed the wing and all the little savings did add up to quite a bit.

I guess these changes will start to appear in the A380 built in the next few years.

 

[Sprucegoose]

On the subject of A380s and weight, a few weeks ago I saw a BBC documentary called 'How to build a Super Jumbo Wing' BBC Two - How to Build..., Series 2, A Super Jumbo Wing
If anyone gets the chance to see I would recommend it as it was very interesting.

One bit it covered was how they were trying to reduce weight. I think they took 80kgs of the landing gear. It showed them testing to make sure the gravity drop still worked as expected with the lighter landing gear.

Also they were taking some weight out of the structure of the wing while still maintaining the strength. Only little bits here and there. They weighed the wing and all the little savings did add up to quite a bit.

I guess these changes will start to appear in the A380 built in the next few years.

Yes and don't forget different airlines have different fit out weights. What does a sky bed weigh? Additional galleys etc. Bars? All these configurations have a weight impact.

 

[simongr]

Yes and don't forget different airlines have different fit out weights. What does a sky bed weigh? Additional galleys etc. Bars? All these configurations have a weight impact.

My point earlier was genuine surprise that aircraft from the same airline with the same fit out would have different weights.

 

[bossreggie]

Hey Guys. Here is something I have always wondered.

When flying, when we get to "top of descent" (I think that's the term) there always seems to be a vibration that goes through the aircraft. It seems to coincide with the reduction in throttle to the engines. Can someone tell me what this is please. Or am I just imagining it?

Thanks.


Sent from my iPad using AustFreqFly App

 

[serfty]

Aside from the air breaks being applied causing turbulance, there can be another factor - the terms for what I believe to be the cause include "Heterodyning" or "Harmonic Vibration".

When a multi engined aeroplane is operating the engines operate at different rpms - when in cruise these are almost the same. Each engine introduces a slight vibration through the airframe basically related to its current rpm. These vibrations combine within the airframe to produce a different frequency, which may be perceived as a vibration. The frequency of this perceived vibration (simplistically, on a two engined aeroplane) is the difference between the frequency of the vibrations generated by each engine.

At the "top of decent" the engines are throttled back and may decelerate at different rates. This results in a change to the perceived vibration.

Similar occurs at the "top of climb" when the engines are throttled back to cruise; but generally not as pronounced.

e.g. In cruise, one engine may be rotating at 2003 rpm and the other at 2011 rpm. This produces a dynamic though the airframe of 8 rpm.

When descent is commenced the engine may slow down at different rates, maybe varying by several hundred rpm or more for several seconds. This produces the sort of low frequency 'shudder' experienced through the cabin.

 

[harvyk]

That's asking how long is a piece of string. Rough numbers say that it could.

Well the piece of string would be 8578 mi...

(Sorry couldn't resist)

 

[Cruiser Elite]

So I am booked on SQ237 - dep SIN at 00:45 on Nov 30 - am one of the first on board and park my cough in my seat.

Call little stunner over and ask for champagne - by the time she returns I realise it is way hot - say jeez it's hot in here - one moment Sir - I will check the temperature setting - returns and says YES it is a little hot in here as temperature on ground always a couple degrees warmer than in air. What is temp set at? In air we usually set it at 22 to 23 deg - but always a little warmer on ground.

Question 1 - Why is 22deg on ground warmer that 22deg in air?

I drink my second glass of Champers and then there is announcement from Pilot - good evening passengers - blah blah blah........................sorry to inform you but we will have a brief delay before pushing back tonight - because of prevailing weather conditions flight tonight SIN-MEL will experience very strong tail winds which would put us in MEL 40mins early and Melbourne Airport will not accept us at that time - so please be patient.

Question 2 - Can't the Jelopy Jockey up the tip just drive in 3rd gear? Can't he propel that focker forward with the hand brake on or sumpin' - like depart at designated time and just fly slower - wouldn't that save fuel or whatever and not have pax sitting in sauna like conditions getting totally pissed off at the delay?

 

[meloz]

Hey Guys. Here is something I have always wondered.

When flying, when we get to "top of descent" (I think that's the term) there always seems to be a vibration that goes through the aircraft. It seems to coincide with the reduction in throttle to the engines. Can someone tell me what this is please. Or am I just imagining it?

Thanks.


Sent from my iPad using AustFreqFly App

Speed brake perhaps?

Meloz

 

[Awesom Andy]

Question 2 - Can't the Jelopy Jockey up the tip just drive in 3rd gear? Can't he propel that focker forward with the hand brake on or sumpin' - like depart at designated time and just fly slower - wouldn't that save fuel or whatever and not have pax sitting in sauna like conditions getting totally pissed off at the delay?

I believe there is an optimal airspeed for the aircraft type, and any faster or slower would result in fuel penalty.

Speed brake perhaps?

Don't think it's likely that they would be using the spoilers at the top of descent?

 

[meloz]

Don't think it's likely that they would be using the spoilers at the top of descent?

I believe there is a difference between spoilers and speed brakes even if some aircraft share the same surfaces.

I seem to recall 76's and 330's often using brakes at the beginning of descent.

Meloz