Ask The Pilot

[mjt57]

Re: Now Boarding ... Chicken or Beef?

That's actually a curious comment, as the thrust levers in the -400 are linked, but electronically. As long as they're fairly close to lined up, the engine FADECs will ensure that the thrust is matched.

When I did the B738 sim to set the required thrust all I needed to do was to set both levers to 60%. On the display each throttle or thrust position is shown as a circular bar graph, I s'pose you'd call it. A 2nd circular bar graph would then rise up to match it, presumably that aircraft's version of FADEC setting the demand for each engine to match the manual setpoint (thrust lever position).

How does the A380 do it?

On another note, often "yaw damper" is mentioned. I looked it up on Wiki but its description is fairly brief so I couldn't really understand how it works or how it's applied. Do you know any links where I can get a better description of it? Or can you explain it better?

Finally, when discussing "alternate law", I presume that it's a mode of control that Airbus uses. Why the term "law" in this regard?

 

[jb747]

Re: Now Boarding ... Chicken or Beef?

When I did the B738 sim to set the required thrust all I needed to do was to set both levers to 60%. On the display each throttle or thrust position is shown as a circular bar graph, I s'pose you'd call it. A 2nd circular bar graph would then rise up to match it, presumably that aircraft's version of FADEC setting the demand for each engine to match the manual setpoint (thrust lever position).

One part of the display is showing the commanded thrust, and the other the actual thrust. We only occasionally use the command part of the display (on the ground setting the initial 30%). After that you tend to just push or pull the levers for effect, not specifically looking for a power number, but just making the speed trend vector 'go away'. Of course, in the 380, it's almost always autothrust.

How does the A380 do it?

In manual thrust, basically the same. In auto, the levers are left in a gate, and don't move with thrust changes.

On another note, often "yaw damper" is mentioned. I looked it up on Wiki but its description is fairly brief so I couldn't really understand how it works or how it's applied. Do you know any links where I can get a better description of it? Or can you explain it better?

Look up Dutch roll. The yaw damper is there to counter that....

Finally, when discussing "alternate law", I presume that it's a mode of control that Airbus uses. Why the term "law" in this regard?

The FBW system is written to obey a set of rules. So calling them 'laws' is as good a term as any. Depending upon the health of the system, it may operate in NORMAL law, ALTERNATE law I, ALTERNATE law II or DIRECT law. In normal law, the flight control computers interpret your control inputs to give you a result. You don't really care which controls are used, or how it does it. If you place the aircraft in a 10 degree bank, it will stay there. Protections exist for bank and pitch limits, overspeed, g limits, angle of attack (i.e. stall). As the system degrades, it might fall back to ALTERNATE I, where most of the protections have disappeared, but the automatics are still available. ALTERNATE II is a bit further down this road, but this time, no automatics are available (flight director, autopilot, auto thrust). In DIRECT law, the controls simply move in concert with any control input. No automatics are available, but the basic flight behaviour is as per a non FBW aircraft (i.e. 747 or 767).

 

[Skyring]

Re: Now Boarding ... Chicken or Beef?

Look up Dutch roll. The yaw damper is there to counter that....

I'm guessing these aren't pastry snacks?

IIRC, the B707 had a lot of problems - including fatalities - with Dutch rolls. ASN Aircraft accident Boeing 707-227 N7071 Arlington, WA

 

[mjt57]

Re: Now Boarding ... Chicken or Beef?

Look up Dutch roll. The yaw damper is there to counter that....

thanks.


On another note who knows why Melbourne airport has closed off the observation deck to the public. I'm waiting for my flight. Meanwhile QF9 to LHR is about to depart and I wanted to watch it.

 

[flyingfan]

Re: Now Boarding ... Chicken or Beef?

On another note who knows why Melbourne airport has closed off the observation deck to the public. I'm waiting for my flight. Meanwhile QF9 to LHR is about to depart and I wanted to watch it.

IIRC it's been closed since 9/11 probably because it was a bit too easy to jump over the barrier and access airside areas. I expect it's a very low priority for the airport owners to build a 'secure' observation deck.

 

[wafliron]

Re: Now Boarding ... Chicken or Beef?

On another note, often "yaw damper" is mentioned. I looked it up on Wiki but its description is fairly brief so I couldn't really understand how it works or how it's applied. Do you know any links where I can get a better description of it? Or can you explain it better?

To expand slightly on the rather technical description of "dutch roll" on Wikipedia, the "seat of the pants" impression of it occurring (at least in the sim) is that it feels like the plane is "wiggling" around all over the place, even when flying on a straight and level heading. If you've ever sat right up the back of an A380, it's a bit like the "wiggling" you sometimes feel back there (which may in fact be not-fully-damped dutch roll?) but constant and much stronger, and with roll thrown in (the back of the A380 "wiggle" just feels like yaw to me). It was unpleasant, and if I felt it as a passenger I'd probably find it quite disconcerting, probably even concerning. So, hooray for yaw dampers

The Wikipedia article also touches on adverse yaw (https://en.wikipedia.org/wiki/Adverse_yaw) at the end, which is actually how this topic came up during my sim time. A couple of years ago I did one of those brief "try out flying" sessions in a light aircraft, and I remembered having to apply rudder input when turning (and hence rolling). I asked the 747 instructor about the need to do this and he said it wasn't required, because the yaw damper compensated for it.

 

[dodgeyhack]

Re: Now Boarding ... Chicken or Beef?

I noticed that QF93 squawked 7600 (radio failure) on (I presume) the way out of Melbourne today.
This has me curious about what procedures the pilots would follow in that situation?
I've been reading about the situation at small airports with light signals.
But for commercial operations, I imagine there's multiple available communication channels, e.g. radio, text based, etc.
So do you just fall back to the next level down and it's all very routine?

 

[jb747]

Re: Now Boarding ... Chicken or Beef?

I noticed that QF93 squawked 7600 (radio failure) on (I presume) the way out of Melbourne today.
This has me curious about what procedures the pilots would follow in that situation?
I've been reading about the situation at small airports with light signals.
But for commercial operations, I imagine there's multiple available communication channels, e.g. radio, text based, etc.
So do you just fall back to the next level down and it's all very routine?

I pretty much can't imagine how you'd ever have a radio failure. 3 VHF. 2 HF. Data link. 2 sat phones. Plus about 500 smartphones.

What I can easily imagine, and have seen twice, is radio failure at the ground end. Whilst radios are duplicated, there seem to be various 'choke points', and a lightning strike in the right spot has driven Singapore to total silence on a couple of occasions that I've seen. Radio failure procedures when the aircraft loses the radio are straightforward, and basically involve following the flight plan and then flying whatever is the logical approach at destination.

I've also heard of these numbers being selected accidentally (generally for only a short time), i.e. transposing two digits. Also I've seen an instance where the software on the ground (Melbourne ATC) generated spurious 7X00 indications.

 

[SenZubEanS]

Re: Now Boarding ... Chicken or Beef?

Well OQB was the only bird squawking 7600 at the time, so wouldnt think it to be something ground based. So you have not had radio failure requiring this squawk JB?

 

[Ansett]

Re: Now Boarding ... Chicken or Beef?

Well OQB was the only bird squawking 7600 at the time, so wouldnt think it to be something ground based. So you have not had radio failure requiring this squawk JB?

Hi I was on OQB ( Hudson Fych ) this morning as it was operating QF10 from Singapore and did not notice any issues atall

 

[markis10]

Re: Now Boarding ... Chicken or Beef?

Hi I was on OQB ( Hudson Fych ) this morning as it was operating QF10 from Singapore and did not notice any issues atall

I am not sure you would notice radio failure .

 

[jb747]

Re: Now Boarding ... Chicken or Beef?

Well OQB was the only bird squawking 7600 at the time, so wouldnt think it to be something ground based. So you have not had radio failure requiring this squawk JB?

Not in an aircraft which has so many radios, with different power sources. In A4 and Macchi, yes.

I guess we'll find out in the fullness of time, but I'd expect it was either a mistaken selection, or a spurious ground signal generated from ATC's equipment. I saw this when Melbourne ATC started reading a 7500 from my aircraft, even though it was most definitely selected to the appropriate number.

In any event, I'd be prepared to bet $ on it not being real.

 

[jb747]

Re: Now Boarding ... Chicken or Beef?

I am not sure you would notice radio failure .

I know of 500 people who didn't notice alternate law either.....

 

[SenZubEanS]

Re: Now Boarding ... Chicken or Beef?

In any event, I'd be prepared to bet $ on it not being real.

Ohhh, if only I was flying on an A380 sometime soon and could collect.... (or pay up) Haha

 

[legroom]

Ask The Pilot

Hi JB,

Do pilots have a on-call roster to replace someone who calls in sick at short notice?

How do you ensure then that such roster could cover all aircraft types ?

What happens if a captain has a migraine episode on the way to the airport (yes, he/she would probably not be on the roster with such a medical history . Just an example !).

Further, do pilots have to go through an annual physical in addition to sim tests ?

Cursory or thorough like stress test etc... ?

Thanks

 

[jb747]

Do pilots have a on-call roster to replace someone who calls in sick at short notice?

Out of Sydney, there are generally two standby pilots in each rank for each aircraft type.

How do you ensure then that such roster could cover all aircraft types ?

You just have to have many.....

What happens if a captain has a migraine episode on the way to the airport (yes, he/she would probably not be on the roster with such a medical history . Just an example !).

In that instance...he wouldn't have a medical to start with. But, if, for instance, he was involved in a traffic accident, then the standby would be called out. That would, most likely, delay the flight by an hour or so. Standbys are never at the airport, because that would start the CASA (duty time) clock, and so limit how they could be used.

Further, do pilots have to go through an annual physical in addition to sim tests ?

Very much so, and they get tighter as you get older.

Cursory or thorough like stress test etc... ?

Varies with age, weight, cholesterol, and about a million other things. Basically though, if you're the healthiest person on earth, you do a stress test at 55 and then at 60 and then every year (or perhaps two...I haven't gotten there yet).

 

[mannej]

JB - I am aware that the details are sketchy on this one here, but any idea on what went on here?

http://www.australianfrequentflyer....l-news/ek-has-another-oops-between-47589.html

If there were issues with the door, or it did "open", would the oxygen masks not drop?

I guess there are a few details missing aren't there.

 

[jb747]

JB - I am aware that the details are sketchy on this one here, but any idea on what went on here?

http://www.australianfrequentflyer....l-news/ek-has-another-oops-between-47589.html

If there were issues with the door, or it did "open", would the oxygen masks not drop?

I guess there are a few details missing aren't there.

My wife was just asking me about this. In large part the articles look to be BS.

I'd hazard a guess a the door sealing having small hole in it. Makes noise, but that's about the extent of it.

 

[defurax]

My wife was just asking me about this. In large part the articles look to be BS.

I'd hazard a guess a the door sealing having small hole in it. Makes noise, but that's about the extent of it.

I can confirm it makes a lot of noise! It happened to door U3R in January 2012 on my LHR-SIN flight. A young couple seated at the exit door in the PE cabin got the scare of their life :shock:
But a flight crew member (I guess the SO) came to look at the door. I think he simply used a piece of paper to see if the seal was OK and 30 min later the noise stopped. I'm no expert in aircraft door, but I guess there in an outer and inner seal?

 

[jb747]

I can confirm it makes a lot of noise! It happened to door U3R in January 2012 on my LHR-SIN flight. A young couple seated at the exit door in the PE cabin got the scare of their life :shock:
But a flight crew member (I guess the SO) came to look at the door. I think he simply used a piece of paper to see if the seal was OK and 30 min later the noise stopped. I'm no expert in aircraft door, but I guess there in an outer and inner seal?

No, I don't think so. Aircraft leak air all the time. As long as you pump in at least as much as they lose, then they stay pressurised. Opening (as opposed to fixed) coughpit windows are a real issue with this, because they are very close to the pilots, and if the noise is loud or high pitched enough can cause permanent hearing issues. A wet handcloth could often fix things on the 767....