Ask The Pilot

[markis10]

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Just a timely reminder of the forum guidelines!

 

[QF WP]

I've always wondered about the movement of wind at altitude and how if affects clouds.



This is my view near home this morning. What does this pattern tell pilots about wind movement?

 

[ginnypooch]

Just a timely reminder of the forum guidelines!

Sorry! I guess this was probably aimed at me. I wasn't referring to a specific company but if any incidents occur that need reporting, does the body it is reported to pass on some sort of penalty?

 

[markis10]

Sorry! I guess this was probably aimed at me. I wasn't referring to a specific company but if any incidents occur that need reporting, does the body it is reported to pass on some sort of penalty?

No it was a general reminder of the guidelines, specifically the need for answers from professional pilots in the first instance and the fact there will be some topics that cannot be answered owing to employee contracts etc.

 

[ginnypooch]

JB

Does St elmos fire only occur at altitude, or is it possible to encounter this phenomenon closer to the ground? If it occurs closer to the ground, does it affect the ability to land?

 

[jb747]

Why was this brought to the attention of ATSB in the first place?

QF has a very strong culture of self reporting (which is quite contrary to what some commentators would have you believe).

If you make a mistake, you can be almost certain that you aren't the first, and won't be the last. In situations like this, there can be some ramifications, which whilst not dangerous, can be quite untidy. So, if you self report, and something is actually done, then you might save somebody from doing it.

In the vast majority of cases, things that are self reported would never have been discovered by either QF or the authorities. I can guarantee for you, that this sort of culture does not exist everywhere.

FO accepted an alert/alarm that he had to check the data. So, why does this upgrade need to be done if the alerts are already in place?

Because it's not really an alert. A very small text message appears on the lower part of the FMC. There are no associated noises or actual alerts. Plus, during a flight messages will appear there dozens, and probably hundreds of times...and most simply require deletion. If you do nothing, they just continue to sit there....

Changing procedures doesn't really stop it from happening again. Mistakes will always be made, especially given the complexity of the Airbus procedures...which continue to become more complex (and thus less useful) as they keep adding steps to 'correct' for previous problems. The actual solution is for the system to check for the presence of the numbers at the time the thrust is set for takeoff.

And what is this take off data? Required thrust, airspeed, etc.?

V speeds and thrust derate. Without the derate, it simply defaults to max, which is a safe default. Without the Vspeeds, SRS guidance and flight director won't be available after lift off. V1 won't be called automatically, nor will Vr be displayed. So, you won't have any targets. Because there have always been some ways of losing this data, in both brands of aircraft, I've always either written the data on a piece of paper that I leave within my field of view, or leave the performance calculation page up on the OIT. The upshot is that it can create confusion, and that is bad in itself.

 

[jb747]

Takeoff speeds are far from a little thing, a quick read of the EK report for MEL shows that. When something goes wrong in Aviation, often it's a lot of little things that add up to one big problem, fixing the little things helps make the world safer, even if it is an extra item on a checklist.

I'd consider the lack of take off speeds to be far safer than the EK (or Singair) examples. In both of those cases the numbers were incorrectly calculated, with vastly wrong power and Vspeed settings. My understanding is that in the Singair case, they never actually worked out why they had the tail scrape, and so continued to use the incorrect numbers for the approach as well.....

 

[jb747]

Are there any airports that use the aircrafts right hand side doors as the main entry/exit for passengers and crew? (would give a new meaning to the "turn left upon boarding" directive)

I'm sure there are somewhere. There's no particular reason not to, other than the issue of interference with cargo loading. There was a bay in Melbourne that used a forward right door on the jumbo, but I think that disappeared in the building update.

 

[markis10]

[/COLOR]I'm sure there are somewhere. There's no particular reason not to, other than the issue of interference with cargo loading. There was a bay in Melbourne that used a forward right door on the jumbo, but I think that disappeared in the building update.

The old TWA terminal at JFK had a few:

Photos: Boeing 747-1... Aircraft Pictures | Airliners.net

Also the Comet 4 was designed to board via the Starboard door, and the VZ10 also used the starboard door as well!

http://www.plane-spotter.com/Aircraft/index.htm

 

[jb747]

Waves. Short wavelength rough. Long wavelength, like going up and down a roller coaster.

 

[jb747]

Does this sort of thing therefore result in major ticking off?

In the worst case it might mean a visit to the sim. Mostly, it's "thanks for reporting, please don't do it again". Responsible management is much more interested in knowing what, and why, things happen.

Probably the worst crime, is failure to self report.

 

[jb747]

There is a report on AV Herald Accident: Hawaiian B763 near Pago Pago on Dec 2nd 2010, turbulence injures 4 about turbulence and it mentions "gravity waves"

Satellite images showed no convective activity in the area, meteorologists assessed the aircraft was climbing through a boundary defined by significant decrease in atmospheric pressure. These boundaries are conducive to gravity waves.

Are these gravity waves a common occurence ?

Actually I thought the physicists were still trying to find 'gravity waves'. I've never heard the term used before.

The report also says that over a 10 second period there was a strong change in wind direction and speed. Straight away that will give an instantaneous change in lift...and there's your turbulence.

I find the procedure used by most US airlines, of having the seat belt sign on, and the cabin crew blithely going about their business to be a recipe for disaster. If it's not safe for the passengers, then it's equally unsafe for the cabin crew...especially if they might be getting carts out. It also teaches people to ignore the signs. It's amazing how often in turbulence events, when the signs have been on for quite some time, passengers are still unrestrained. There will be NO warning. A nice smooth ride can go to a 2 g jolt instantly....

 

[jb747]

Does St elmos fire only occur at altitude, or is it possible to encounter this phenomenon closer to the ground? If it occurs closer to the ground, does it affect the ability to land?

I've only ever seen it close to the ground once, and that was the best display I've ever seen. It was probably also the worst weather I've ever flown in....a departure from Taipai in the middle of the wet season. In that case the arcing was off the whole aircraft. It looked like someone was shining a flashlight from the radome.

St Elmos itself has no effect upon the aircraft. But, the weather that it's associated with does, and if near the ground, I'd probably not be wanting to land anyway. I think you could be certain that its big brother (lightning) wouldn't be far away.

 

[day-heg]

JB,
Firstly, may I add my thanks for your hugely informative and oft-witty responses to the myriad questions that we've all posed to you on this thread.

You may not be able to answer my question, as I don't think you've ever flown A330 metal, but here goes nonetheless...

I was on a flight from LHR to CAN a few weeks ago. About an 90 minutes in, we hit some fairly strong and sustained (over a good 5-7 minutes or so) of turbulence. At the same time, the noise of the engines increased significantly and quickly; it wasn't a gentle increase, more like opening the throttles right up when you commence the take off roll. However, there was no corresponding increase in thrust that I noticed, or change in pitch or nose up attitude.

It lasted for 10 minutes or so - longer than the turbulence - and then returned to a lower volume that I'd more associate with the cruise. It happened a couple of times more in the first half of the flight, once at the same time as more turbulence. Each time when the noise reduced, I didn't feel any slowing down of the aircraft.

Any ideas what/why that might have been?
Cheers,
D-H

 

[jb747]

JB,
Firstly, may I add my thanks for your hugely informative and oft-witty responses to the myriad questions that we've all posed to you on this thread.

You may not be able to answer my question, as I don't think you've ever flown A330 metal, but here goes nonetheless...

I was on a flight from LHR to CAN a few weeks ago. About an 90 minutes in, we hit some fairly strong and sustained (over a good 5-7 minutes or so) of turbulence. At the same time, the noise of the engines increased significantly and quickly; it wasn't a gentle increase, more like opening the throttles right up when you commence the take off roll. However, there was no corresponding increase in thrust that I noticed, or change in pitch or nose up attitude.

It lasted for 10 minutes or so - longer than the turbulence - and then returned to a lower volume that I'd more associate with the cruise. It happened a couple of times more in the first half of the flight, once at the same time as more turbulence. Each time when the noise reduced, I didn't feel any slowing down of the aircraft.

Any ideas what/why that might have been?
Cheers,
D-H

I assume you were sitting at the rear of the aircraft. Engine power changes are often more readily heard back there.

A common response to turbulence is to try to climb above it. Very often it's a relatively thin layer, and even a couple of thousand feet will get you clear of it. If the aircraft is already operating near max altitude, the climb rates available are very low, so that two thousand foot climb could easily take five minutes or more.

Wind changes will also throw up power changes. If the wind switches to a tail wind, the aircraft's instantaneous response is to lose airspeed, and autothrust will respond by increasing the power until it gets back to the target speed. If the change is great enough (and the airspeed loss big enough), it's actually possible that full power would not be enough to ever recover the speed. Obviously that's the extreme case, but, it could take some minutes to regain speed lost in seconds.

At altitude you're unlikely to pick the pitch attitude change for a climb. It's very small...less than a degree. At cruise altitudes, the aircraft operate in a very narrow margin. There could be only a few knots between the maximum and the minimums speeds that you have available. Power requirements aren't quite what people expect. Whilst there is a power margin (so we aren't cruising at max thrust), reducing speed more than that few knots will take you below min drag speed, and so flying slower will also require more power.

The extreme case of the above is called 'coffin corner'. At that part of the flight envelope, your stall speed actually equals your maximum speed....so you can go neither faster or slower.

 

[mannej]

The extreme case of the above is called 'coffin corner'. At that part of the flight envelope, your stall speed actually equals your maximum speed....so you can go neither faster or slower.

How does coffin corner relate to AF447?

 

[ChrisGibbs]

JB747 - far too many years ago learning to fly a C150 at the Airport Flying School in Canberra we were told to gently dab the brakes as you commenced taxiing to ensure your brakes were working and you could stop if needed. In the years of flying as a passenger on various types of Airbus (irrespective of airline) you can notice the brakes being applied at the start of the taxiing. Is this part of the standard Airbus checklist as I don't notice it when flying on a Boeing?

One other difference I've noticed when flying on an Airbus is the chimes are activated and the exit signs flash when the gear is either retracted or extended. Is this other feature specific to Airbus?

Thanks

 

[Skyring]

At altitude you're unlikely to pick the pitch attitude change for a climb. It's very small...less than a degree.

But I can just about always, in the seat of my pants, detect when descent has begun. I guess that means it's more than a degree in pitch. What exactly is happening when you begin your descent? Haul back on the throttles, do something with the control surfaces, punch the autopilot button that says "Sydney"?

 

[jb747]

How does coffin corner relate to AF447?

Coffin corner isn't actually a fixed position in the flight envelope. It varies with angle of attack (amongst other things). So, if you're flying at (or close to) the corner, just getting to a turning point and having the autopilot roll on 20 degrees angle of bank will have the effect of taking you outside the envelope.

AF447 is difficult to explain, simply because what was done is so alien to the entire flying environment. I truly doubt that the FSX people could have done a worse job, and they aren't even pilots.

Normally, in an Airbus, f you pull, and hold, full aft stick the aircraft will pitch up. It will decelerate, and the angle of attack will increase. The engine power will be increased by the autothrust, in what will be a vain attempt to control the speed. At some point it will reach the maximum available angle of attack, and the flight control system will start pitching it down. Because you will have decelerated so much, you will have to descend to regain your airspeed, so you will end up with an excursion in height both above, and below, your planned altitude. Extremely untidy, but it shouldn't be dangerous....unless those heights happen to be occupied.

But, in alternate or direct law, pulling and holding aft stick will simply stall the aircraft. The recovery requires forward stick, and then a gentle pull back towards a stable attitude. There is nothing odd about this...it's how aircraft have always flown.

The stall is an aerodynamic event. The engines really don't have anything to do with it. You can stall at full power or idle. Upside down or right way up.

 

[jb747]

JB747 - far too many years ago learning to fly a C150 at the Airport Flying School in Canberra we were told to gently dab the brakes as you commenced taxiing to ensure your brakes were working and you could stop if needed. In the years of flying as a passenger on various types of Airbus (irrespective of airline) you can notice the brakes being applied at the start of the taxiing. Is this part of the standard Airbus checklist as I don't notice it when flying on a Boeing?

In an Airbus, virtually every action that is made is simply the moving of a switch. The brakes may look like normal pedals, but they are just large switches. Everything is electric. So, with the failure of a switch, items like the brakes can be rendered unworkable. History says that most of those switches are pretty reliable, but they aren't within an order of magnitude as reliable as a duplicated cable/hydraulic system. So, to improve that reliability, there must be backup systems. The brake check at the start of taxi ensures that they work, and that they're in the correct mode.

The Airbus has a memory procedure for 'loss of braking'. The Boeings (747/767 anyway) don't.....

One other difference I've noticed when flying on an Airbus is the chimes are activated and the exit signs flash when the gear is either retracted or extended. Is this other feature specific to Airbus?

I just noticed that myself. I paxed twice on a 330 this week, and noticed the 'ding', so I asked about it. I think Microsoft would describe it as an 'undocumented feature'. I don't know whether the 380 does it or not.

Correction to that...thinking about something else. When in auto mode, the seat belt signs are activated by either flap or gear selections. What I was distracted by, was that I'd noticed on two 330 flights that the 'ding' happened just after take off. It may have been associated with the up selection of the gear, but as the signs didn't change, and it was barely after lift off, it had to be spurious.