Ask The Pilot

[Flying Fox]

I've looked at some A380 pics and noticed that the front bottom of the engine cowls there seems to be a sizeable square patch painted grey or not painted the same colour of the engine cowls.

What is the reason for this?

 

[jb747]

I've looked at some A380 pics and noticed that the front bottom of the engine cowls there seems to be a sizeable square patch painted grey or not painted the same colour of the engine cowls.

What is the reason for this?

It's not just on 380 engines...or even Rolls Royce. I think it's the exhaust port for the cowl anti icing system.

 

[flychrisfly]

Before coughpits were as computerised as they are today, during the preflight procedures was every single switch, knob or button in the coughpit checked or set?

If not, why not? And approximately what proportion or how many were?

thanks in advance.

 

[jb747]

Before coughpits were as computerised as they are today, during the preflight procedures was every single switch, knob or button in the coughpit checked or set?

If not, why not? And approximately what proportion or how many were?

If I recall correctly, the classic 747 had a few hundred knobs, switches and dials. The advent of the 747-400 dropped that to about 200, but many functions are still there but hidden under layers of menus on the various screens.

Pretty well everything has to be checked. Some switches, that reside under guards, only need to have the guard checked closed (as the action of closing the guard also moves the switch to its default position). Many of the dials/displays will also need have flags/warnings checked. Of course, many warnings will be present...but they have to be the right ones.

On the digital aircraft it's much easier to get the switches into an acceptable position, but it takes time to go through the layers of functions within the FMC. When well practiced, it was possible to get a 767/747 done in about 10 minutes, so the holdup was always the wait for the IRS to align. The 380 is much slower, easily taking 30 minutes. The holdup there is the depth of functions within the FMC that have to be either checked, or loaded, and then checked again by the other pilot.

 

[harvyk]

If I recall correctly, the classic 747 had a few hundred knobs, switches and dials. The advent of the 747-400 dropped that to about 200, but many functions are still there but hidden under layers of menus on the various screens.

Pretty well everything has to be checked. Some switches, that reside under guards, only need to have the guard checked closed (as the action of closing the guard also moves the switch to its default position). Many of the dials/displays will also need have flags/warnings checked. Of course, many warnings will be present...but they have to be the right ones.

On the digital aircraft it's much easier to get the switches into an acceptable position, but it takes time to go through the layers of functions within the FMC. When well practiced, it was possible to get a 767/747 done in about 10 minutes, so the holdup was always the wait for the IRS to align. The 380 is much slower, easily taking 30 minutes. The holdup there is the depth of functions within the FMC that have to be either checked, or loaded, and then checked again by the other pilot.

Just out of interest, why does it take an IRS 10 minutes to align?

 

[jb747]

Just out of interest, why does it take an IRS 10 minutes to align?

IRS Alignment Question — Tech Ops Forum | Airliners.net

Inertial Reference System

Basically, it takes around that long for the earth to move enough to give it enough motion information.

 

[mjt57]

IRS Alignment Question — Tech Ops Forum | Airliners.net

Inertial Reference System

Basically, it takes around that long for the earth to move enough to give it enough motion information.

Did GPS technologies replace these IRS devices or do they still get used?

 

[jb747]

Did GPS technologies replace these IRS devices or do they still get used?

IRS provides attitude and heading data as well as position. It is the source of our reactive windshear alerts. It's self contained, and not subject to outages. GPS only gives position and speed, and it suffers from the occasional degradation. The two are complementary. You can go flying without GPS, but not IRS.

 

[RooFlyer]

I recall seeing a program where IIRC an aircraft in the USA was given a heading, and more significantly, an altitude by ATC which put it 'going the wrong way' in an established corridor, with disastrous results.

I imagine that after flying a route for several years you would get to know the various holding levels & areas, the corridors / elevations going one direction or another etc.

If ATC were to give you a direction for a course/altitude which didn't seem right, I imagine you would ask them to repeat or confirm.

If they confirmed their instructions and you were still concerned, or lets say convinced in your own mind that the designated course was a mistake and potentially dangerous, what options are open to you? For instance at the extreme, might you declare a 'pan' and ask for a different 'way out', asking tem to confirm that as OK?

 

[Orca]

I recall seeing a program where IIRC an aircraft in the USA was given a heading, and more significantly, an altitude by ATC which put it 'going the wrong way' in an established corridor, with disastrous results.

I imagine that after flying a route for several years you would get to know the various holding levels & areas, the corridors / elevations going one direction or another etc.

If ATC were to give you a direction for a course/altitude which didn't seem right, I imagine you would ask them to repeat or confirm.

If they confirmed their instructions and you were still concerned, or lets say convinced in your own mind that the designated course was a mistake and potentially dangerous, what options are open to you? For instance at the extreme, might you declare a 'pan' and ask for a different 'way out', asking tem to confirm that as OK?

Remember, the responsibility for the safety of an aircraft lies ultimately with the PIC.

If I (as an ATC) gave an obviously incorrect heading or altitude clearance the pilot would question it. Usually that should be enough to make me realise my mistake and issue an appropriate corrective instruction. If not, the aircrew have to ensure the safety of the aircraft and if that means deviating from an ATC clearance then that's what they'll do.

 

[jb747]

I recall seeing a program where IIRC an aircraft in the USA was given a heading, and more significantly, an altitude by ATC which put it 'going the wrong way' in an established corridor, with disastrous results.

I imagine that after flying a route for several years you would get to know the various holding levels & areas, the corridors / elevations going one direction or another etc.

If ATC were to give you a direction for a course/altitude which didn't seem right, I imagine you would ask them to repeat or confirm.

If they confirmed their instructions and you were still concerned, or lets say convinced in your own mind that the designated course was a mistake and potentially dangerous, what options are open to you? For instance at the extreme, might you declare a 'pan' and ask for a different 'way out', asking tem to confirm that as OK?

Be a bugger to have a tombstone that read "followed instructions without thinking".

Nominally one way airways are often used by ATC in the other direction. Same with altitudes. You hear such clearances queried all the time. Many times you hear aircraft knock them back, saying they'll stay at the standard altitude, but often they'll be accepted.

Ultimately though, ATC can't reach out and actually fly the aircraft, so if you really don't like it, it's up to you to decide on an outcome you can accept. Having said that, I've heard, and seen, more mistakes at the aircraft end than I've seen from ATC.

Sometimes, these discussions become rather interesting. An aircraft from a very large middle eastern airline, when flying over India, wanted a clearance to deviate about 50 nm to the north of track to avoid weather. It was denied on the basis that that would take it into a live missile firing area. The crew persisted, and ATC replied that there was no way a clearance would be given. They declared an emergency, and proceeded to the north. Sadly we didn't hear the final outcome. As I saw it, flying into the firing area was the worst possible thing to do. So, his remaining options were to transit the weather, or turn around. He had TCAS, and on it would have seen that numerous aircraft were successfully negotiating the line of weather (we were right in the middle of it when the conversation started, and it wasn't bad). He basically abused the whole emergency concept...it was very unprofessional.

On another occasion, an aircraft from a European operator, was instructed by ATC (again in India) to descend due to traffic at the Afghan border. He replied that he had a clearance through Afghanistan at F350, and no, he would not be descending. The conversation continued, and he was eventually passed to the Pakistani controllers who told him the same thing...and got the same reply. He, in fact, DID NOT have such a clearance. Departing Asia for Europe, a system called Bobcat would allocate times and altitudes for overflight of Afghanistan, but it only sequenced for take off time, and after that was subject to change by the controllers. It did have the effect of spacing the aircraft out, so that the controller had a chance. Ultimately the Pakistanis sent him off the airway, and told him to hold at an off track waypoint. As far as I know, he's still there.

 

[mikenz]

Why do ATC use airways? It sounds as though it increases congestion, where there doesn't really need to be congestion.

 

[Orca]

Why do ATC use airways? It sounds as though it increases congestion, where there doesn't really need to be congestion.

Not sure I understand your question... More info?

 

[mikenz]

JB mentions that aircraft can be asked to fly in an airway in the wrong direction. And it seems that flights generally flow through a designated 'lane', particularly in certain areas.

I guess my question is why do aircraft generally fly one behind the other, increasing congestion?

 

[Orca]

Airways are used to segregate traffic flows. For instance between SYD and BNE aircraft fly along a more coastal route (roughly speaking) and going the other way, BNE to SYD, they fly a more inland route. This is much more preferable to having aircraft flying nose to nose all the time (thus increasing risk of collision)

Broadly speaking, using airways allows us to better manage and plan separation between aircraft and leads to much increased capacity. Having a "free for all" would be much too risky.

 

[jb747]

JB mentions that aircraft can be asked to fly in an airway in the wrong direction. And it seems that flights generally flow through a designated 'lane', particularly in certain areas.

I guess my question is why do aircraft generally fly one behind the other, increasing congestion?

Really more for an air traffic controller, but...

Placing the aircraft into airways gives them predictable paths. Free tracking (which is used in some low density airspace) makes it much harder to keep track of exactly where the aircraft will be... They know where the are, but where will they be in danger of collision at some future point. Whilst computer software is getting better at this sort of thing, the density levels in some parts of the world pretty much preclude it. And remember that when the computers fall over, which they invariably do, controllers have to have some way of manually picking up the pieces.

 

[markis10]

JB mentions that aircraft can be asked to fly in an airway in the wrong direction. And it seems that flights generally flow through a designated 'lane', particularly in certain areas.

I guess my question is why do aircraft generally fly one behind the other, increasing congestion?

Aircraft fly on routes that are preplanned and optimised for the conditions, as most airlines use similar tools that often means they do the same thing. Because the self loading cargo has certain preferences, like wanting to fly Monday morning and Friday nights, airlines naturally schedule aircraft to make the most of those preferences.

Why have preplanned routes or highways? They are there to help separate the aircraft, while tools such as radar and ADSB make life easy, they can fail, and when they do procedural separation is used which allows for much greater errors. By having everyone on a similar or well defined path, believe it or not, they are easier to separate. Under procedural separation, two aircraft 200 nautical miles apart could technically be in conflict, and have a breakdown of lawful separation.

 

[jb747]

Simulator time again. I've been away on fairly extended leave, so I spent about a week with my head in the books prior to this exercise.

Firstly, in relation to a question about Virgin's sim sequences a while back, QF is changing the system they use, so that we'll now do two sims very close together (apparently they have to be within two months, but will try to make them within a couple of days), followed by a longer break. Still four sims a year.

The exercise that I've just done was around Hong Kong. Windshear warnings occurred throughout the exercise, and appeared to be almost randomly inserted, so some on approach, and others on departure. Just to welcome me back, the very first take off resulted in a low speed abort, when the aircraft failed to give the annunciations that we expect at the start of the take off roll (related to nav, pitch, and auto throttle modes).

Then took off from 25L. Manually flew part of the departure, and then both FO and I did some flying on the standby instruments (all of the fancy screens turned off). Given that the display is only about 2 inches across, it's hard to see, much less fly accurately, but it can be done. To get to that point though, you would need at least six other full sized screens to have failed, so not likely.

After that, we flew up to the north and set up for a VOR approach to 25R. Became visual at the bottom, but got a windshear warning at about 400 feet. Once we'd sorted that out, IP back to just before the shear started, and completed a visual landing. One of the aims of this exercise was to do a bunch of landings at config 3 instead of the normal full...basically less flap. It's more floaty in the flare, but it's a safer configuration to use in expected windshear (as it has less drag).

Because there were a lot of small items to be done, this exercise included a lot of IPs...jumps to a spot in space and different configurations. They can be disconcerting, and it's easy to lose track of what is going on, so it really relies on the instructor making sure you're on top of the position and configuration before releasing the sim. But, they allow multiple looks at procedures without having to go through setting them up each time.

Back to the other runway, and this time, just after V1, I drop dead. When the FO got no response to 'rotate' he quickly took over. Exercise over once he has the a/p engaged, and has completed the clean up and checklist.

IP back to the runway. This time we take off, and fly straight into a windshear event. These aren't mild either, going from somewhere around 20 knots of headwind, to up to 40 tail. Once that is sorted out, IP back and fly an ILS to 25R. Then IP back again, and fly in visual conditions but without any approach slope guidance. Land.

Now the FO has a go. Takes off on 07, and comes back for the VOR 07L. Windshear again. Sort it out and IP back for an ILS 07L, and land.

Time for a coffee break. When we come back, it's all low vis sequences. These are always flown by the captain. So, start with a take off in 175 metres vis. Engine failure, and abort. Exercise stops once you complete the checklist and PAs. IP back to the start of the runway, and go again. This time an engine fails just after V1. Continue take off. Because of the high terrain all around HK, there are special procedures to be flown instead of the SIDs. Once sorted out, for the purpose of the exercise, restart the engine. Carry out a Cat IIIA approach to 25 (50' minima). Go around at about 200' as the reported crosswind is outside limits. Carry out the full go around procedure (which is quite complex) and then another approach. Land off that.

FO now flying. IP to about 150 miles SE of HK, inbound at FL350. Bang...simultaneous engine failure, giving hull breach, and depressurisation. The plan (as of course we knew it was going to happen) was for the FO to be pilot flying and to manage to multiple problems. But, in the sim things don't always go quite to plan. As I dropped the oxygen mask over my face and it retracted, it snapped my glass's frame. So, now I really couldn't see (close up) all that well, certainly not well enough to be able to quickly read the ECAMs that we needed to do. So, I took over control, and got the FO to take that role. The idea in the sim is that you always just deal with issues as best you can...and fractured glasses at an inconvenient time, is just one of those issues. Problems sorted out, and back at 10,000 feet. IP back to HK for the FO to fly a couple of visual approaches. Exercise over.

 

[por930]

Thanks JB for such a detailed rendition of one of your sessions in the simulator. Lots of hard work, but wonderful to see....Is it "pot luck" who the FO is on these occasions?

 

[jb747]

In general it's just an FO who is due for his own session. You never get to pick who you do them with. Same as the flying.