Ask The Pilot

[jb747]

There have been a few crashes that have occurred due to wrong turns on taxiways (The Milan Linate collision and SQ006 are two examples).

Milan was a runway incursion, and is a good example. SQ...perhaps not. They knew where they were...it's just that it wasn't where they were supposed to be.

 

[Sprucegoose]

Ask The Pilot

Milan was a runway incursion, and is a good example. SQ...perhaps not. They knew where they were...it's just that it wasn't where they were supposed to be.

And it was all rush rush rush! Some ex Asian airforce pilots can be very gungho !

 

[mannej]

Ask The Pilot

And it was all rush rush rush! Some ex Asian airforce pilots can be very gungho !

I think there were more issues then just pilot issues with the SQ crash.

 

[markis10]

I think there were more issues then just pilot issues with the SQ crash.

Not really, the runway was partially lit (centreline only) and there were 6 signs passed by SQ006 that indicated the path they were travelling was to the wrong runway, and there was no markings indicating the runway was US as it was being used for taxing aircraft to get to the correct runway

File:SA600 Runway.png - Wikipedia, the free encyclopedia

 

[jb747]

I think there were more issues then just pilot issues with the SQ crash.

Runways are marked out of service all of the time. There was nothing unusual about Taiwan. And I don't think it had anything to do with ex air force pilots.

 

[RooFlyer]

Many thanks jb747 and others.

 

[Flying Fox]

Question about flight controls.

On some planes (I think 737s) on either side of the thrust levers there are two vertical wheels (I think that they have black stripes painted on them). What do these wheels control and why/when do they spin 'automatically'?

Sorry if my description is inaccurate, I hope it makes sense.

Thanks

 

[jb747]

Question about flight controls.

On some planes (I think 737s) on either side of the thrust levers there are two vertical wheels (I think that they have black stripes painted on them). What do these wheels control and why/when do they spin 'automatically'?

Sorry if my description is inaccurate, I hope it makes sense.

Pitch trim wheels.

They move when the pitch trim buttons are selected. I presume that they could also be moved directly without using the button, but you'll need to find an even greyer pilot than me to answer that. Disappeared from Boeings around the time of the 767. Not in the 380 or 747-400.

 

[Flying Fox]

Thanks for the speedy reply.

Can you please describe what the Pitch Trim Wheels do on the aircraft?

 

[mjt57]

Pitch trim wheels.

They move when the pitch trim buttons are selected. I presume that they could also be moved directly without using the button, but you'll need to find an even greyer pilot than me to answer that. Disappeared from Boeings around the time of the 767. Not in the 380 or 747-400.

When I did the Flight Experience sim (B737-800) earlier this year, when the wheel started spinning it alarmed me a bit. They are not small and if your hand was anywhere near it you could sustain an injury. Poor ergonomics, in my view.

During the sim I didn't get enough time to experiment or to learn its function more fully (as was the case with most other aspects of operating the aircraft). And when I asked the instructor about it his answer was somewhat vague. I didn't know if that was because he didn't want to get into a technical discussion about it because he thought it beyond my capability to understand or whether he didn't know himself.

 

[markis10]

I noticed there is the occasional circumstance where an aircraft goes US and is then ferried back to the nearest port for repairs/service. I wonder what sort of faults occur that prevent passengers being taken onboard but allow the aircraft to be flown back to a facility such as what happened with VXS on the 8th ex Broome where it got back to Perth a day before the rescue flight!

 

[simongr]

Not sure if this is a question or observation but I had what I think was my scariest flight on QF last week. I was doing the 7AM flight SYD-MEL on the A330. I am fairly used to this flight and m used to the quietening of the engine noise not long after take off. We usually get advised of this by the Captain. On this occasion though the engines died down then back up a few times whilst at the same time things got a little bumpy. It was almost like the aircraft was struggling to keep going (obviously it wasn't) - the pax next to me looked at each both somewhat quizzically.

It all went back to normal shortly after that but it was the first time I was genuinely worried by the actions of the aircraft. Strange take off certainly - anything that would cause the "truggling" sensation?

 

[jb747]

Thanks for the speedy reply.

Can you please describe what the Pitch Trim Wheels do on the aircraft?

What you really need to know about is trim. The wheels, buttons, etc are just a way of correcting the trim.

When an aircraft is in flight (no autopilot....manual flight), at any given angle of attack (or speed), you want to be able to let go of the controls, and have it stay in the same position. You don't want to have to continually apply any control input to make it stay where you want. I'm sure you've all driven a car with a poor wheel alignment, that constantly wants to pull one way or another...imagine in you could correct that 'pull' with the flick of a switch.

Aerodynamically, a stable, in trim aircraft, can be disturbed (be it a little bit of bank, or a pitch or yaw change) and it should, with no pilot intervention correct itself back to its original situation.

If, for instance, I'm in level flight at 250 knots, and I reduce the power to that required for 200 knots. The aircraft will start to slow. The tail will no longer be providing sufficient down force to hold the pitch attitude, and it will pitch down. It will no longer be in level flight, but will try to give that same angle of attack, so it should end up in a stable 250 knot descent. Now, if that's not what I wanted, but rather level flight at 200 knots, as it slows I'll have to slowly pull the nose up until it stops decelerating and I reach the pitch attitude required for 200 knots. If at any point, I relax the back pressure, it will again head back to that 250 angle of attack...and as I don't want that, I'll have to trim the nose up. That's accomplished by the pitch trim, which in most larger airliners is done by moving the entire tailplane to a new angle of incidence.

Roll and pitch trimming is generally accomplished by putting a bias into the ailerons and rudder.

All of these only work at one particular speed and power setting. Change anything, and the aircraft will need to be trimmed back to that hands off situation. In an airliner, roll and pitch trim are not used all that much, unless you have an engine shut down, and which case any change will require large trim changes in all axes.

FBW aircraft automatically pitch trim, so it isn't something we use at all until back in reversionary laws.

 

[jb747]

Well, for a start, anything to do with the oxygen, airconditioning, or pressurisation systems. Power systems to the cabin. Toilets. Quite a list if you think about it.

The Emirates aircraft that had the tail scrape in Melbourne was ferried out after temporary repair. I expect it flew at relatively low level, unpressurised.

 

[jb747]

I very much doubt that there was anything to be scared of. Off 34R in the 767 the very large power changes are always a bit of an eye opener, but the 330 is almost as powerful. You've probably had a number of small climb steps, coupled with a speed limit, and then most likely removal of that limit. You always run into this off 34R, but it can be almost as bad off 34L. The other runways tend to be less of an issue.

 

[yohy?!]

Well, for a start, anything to do with the oxygen, airconditioning, or pressurisation systems. Power systems to the cabin. Toilets. Quite a list if you think about it.

The Emirates aircraft that had the tail scrape in Melbourne was ferried out after temporary repair. I expect it flew at relatively low level, unpressurised.

Indeed (well according to wiki anyway!):

via Perth, Singapore, Dubai and Cairo with the crew flying below 12000 feet.

Imagine it would've been a bumpy couple of days.

 

[simongr]

I very much doubt that there was anything to be scared of. Off 34R in the 767 the very large power changes are always a bit of an eye opener, but the 330 is almost as powerful. You've probably had a number of small climb steps, coupled with a speed limit, and then most likely removal of that limit. You always run into this off 34R, but it can be almost as bad off 34L. The other runways tend to be less of an issue.

Thanks - I wasn't really scared but it was the first time I was unnerved. The extra clarity around small climb steps is useful.

 

[lc_461]

Hi JB,

I have a question about domestic 'add ons' to international flights from a crewing perspective. For example QF8 obviously gets a fresh crew for the BNE-SYD sector... would that duty be all you have to do that day or would there be other duties following the short domestic hop?

Also for positioning flights (eg BNE-SYD for the 747s every now and again) does there need to be any cabin crew onboard?

Cheers

 

[markis10]

Indeed (well according to wiki anyway!):

Imagine it would've been a bumpy couple of days.

Would have been an interesting flight mixing it with aircraft in uncontrolled airspace when your that big a bird! And the fuel consumption must have been a shocker.

 

[Boris spatsky]

Ask The Pilot

What you really need to know about is trim. The wheels, buttons, etc are just a way of correcting the trim.

When an aircraft is in flight (no autopilot....manual flight), at any given angle of attack (or speed), you want to be able to let go of the controls, and have it stay in the same position. You don't want to have to continually apply any control input to make it stay where you want. I'm sure you've all driven a car with a poor wheel alignment, that constantly wants to pull one way or another...imagine in you could correct that 'pull' with the flick of a switch.

Aerodynamically, a stable, in trim aircraft, can be disturbed (be it a little bit of bank, or a pitch or yaw change) and it should, with no pilot intervention correct itself back to its original situation.

If, for instance, I'm in level flight at 250 knots, and I reduce the power to that required for 200 knots. The aircraft will start to slow. The tail will no longer be providing sufficient down force to hold the pitch attitude, and it will pitch down. It will no longer be in level flight, but will try to give that same angle of attack, so it should end up in a stable 250 knot descent. Now, if that's not what I wanted, but rather level flight at 200 knots, as it slows I'll have to slowly pull the nose up until it stops decelerating and I reach the pitch attitude required for 200 knots. If at any point, I relax the back pressure, it will again head back to that 250 angle of attack...and as I don't want that, I'll have to trim the nose up. That's accomplished by the pitch trim, which in most larger airliners is done by moving the entire tailplane to a new angle of incidence.

Roll and pitch trimming is generally accomplished by putting a bias into the ailerons and rudder.

All of these only work at one particular speed and power setting. Change anything, and the aircraft will need to be trimmed back to that hands off situation. In an airliner, roll and pitch trim are not used all that much, unless you have an engine shut down, and which case any change will require large trim changes in all axes.

FBW aircraft automatically pitch trim, so it isn't something we use at all until back in reversionary laws.

As they say, 'Trim or Die' (or Trim or Fail )