Ask The Pilot

[PointyEnd]

Noticed a few (4) Google Baloons floating by....
Given that they're relatively high (62000' according to flightradar24) would they be a feature of any NOTAMS for flights that would pass nearby?


For more info Google 'Project Loon'

 

[mjt57]

Having a generator that can't feed the instrument buss probably didn't seem an issue with three others than can. And what about an APU with two generators of its own...that you can't start in flight.

With my electrical background I have difficulty in understanding this philosophy.

I wonder why Boeing (and presumably AB too) don't have bus ties so that you can do some switching to supply essential services from whatever remaining generators you've got running and if load is a problem to strip the other buses (I'm sure that the pax wouldn't mind not having an in-flight entertainment system for the time being).

I realise that an aircraft has strict weight limits, so there's only so much redundancy that can be built in. But I would've thought that it'd be aimed at maintaining essential supplies.

What would happen in the 380, if power is lost to the valves which transfer fuel between tanks that these valves have a fail-safe open set up? ie. lost power would de-energise solenoids to allow a spring loaded valve to operate to its open position?

I understand, when reading RdC's book, that a major issue was that he couldn't transfer fuel from the rear tanks. Are they able to gravity feed to other tanks?

 

[jb747]

With my electrical background I have difficulty in understanding this philosophy.

I wonder why Boeing (and presumably AB too) don't have bus ties so that you can do some switching to supply essential services from whatever remaining generators you've got running and if load is a problem to strip the other buses (I'm sure that the pax wouldn't mind not having an in-flight entertainment system for the time being).

I realise that an aircraft has strict weight limits, so there's only so much redundancy that can be built in. But I would've thought that it'd be aimed at maintaining essential supplies.

I expect that they felt that there was adequate redundancy, without using every possible permutation. Passenger systems are load shed very early in any failure sequence. There are bus ties, but if your instrument transfer bus only gets it's power from 1, 2 and 3, if at least one of them isn't tied to the transfer bus, then 4 can't directly power the instrument bus. (I probably have the numbers wrong, but it was something like that.)

What would happen in the 380, if power is lost to the valves which transfer fuel between tanks that these valves have a fail-safe open set up? ie. lost power would de-energise solenoids to allow a spring loaded valve to operate to its open position?

If you end up in the 'emergency electrical configuration' (i.e. no generators, and just the RAT) the only fuel available is whatever is in the feed tanks, and it is gravity fed only.

I understand, when reading RdC's book, that a major issue was that he couldn't transfer fuel from the rear tanks. Are they able to gravity feed to other tanks?

All fuel transfers were inhibited, as was jettison. I don't think the actual CofG ever became an issue, but the ECAM lost the plot with regard to it, and kept coming up with a procedure that could not be followed.

 

[mjt57]

All fuel transfers were inhibited, as was jettison. I don't think the actual CofG ever became an issue, but the ECAM lost the plot with regard to it, and kept coming up with a procedure that could not be followed.

That would be terrifying if you lose your control and indication systems. Systems telling you stuff that isn't happening, or not displaying things which are or are not happening as they should, that sort of thing. Watching the 4 Corners version of that incident (Nein's was rubbish, I thought) and reading the book, I could relate to what he and the rest of the guys went through, sort of.

Something similar happened to a friend of mine recently at work. Had a runaway boiler on his hands with partial control and indication til the computers were rebooted. Difference here was that no lives, at least not within 5km were at risk and he wasn't faced with the quandary of "I'd rather be down here wishing that I was up there, than being up there wishing that I was down here..."

At least this sort of thing doesn't happen with old technology (eg. 747 classics) where it's all analog...

Well, you'd hope not...

But aviation engineering is several levels above that of what I'm used to, but sometimes I wish that we had that sort of level...

 

[jb747]

That would be terrifying if you lose your control and indication systems. Systems telling you stuff that isn't happening, or not displaying things which are or are not happening as they should, that sort of thing. Watching the 4 Corners version of that incident (Nein's was rubbish, I thought) and reading the book, I could relate to what he and the rest of the guys went through, sort of.

If anything it put the lie to the Airbus dumbing down, let the computers do the thinking, mindset....which only exists to allow for less qualified, and cheaper, pilots. The ECAM was basically useless once it went past two problems. Its solution was often to turn back on a system it had just told you to turn off. The issue was simple...the engineers who designed it did so with the philosophy "it will not happen". It always will...

As I think RdC says in his book, when it became too confusing trying to sort out what the ECAM was saying, it's actually easier to look at the systems and see what actually still works. I did the same thing on the 30. We couldn't work out why we were seeing what we were, so at one point I went through all of the major systems and ticked off what was working...and as the major ones were mostly healthy, that meant I could ignore much of what was happening.

At least this sort of thing doesn't happen with old technology (eg. 747 classics) where it's all analog...

The flight engineers were digital...they had two states, awake and asleep.

 

[Himeno]

How often have you had to perform emergency landings? For what sort of reasons?

 

[jb747]

How often have you had to perform emergency landings? For what sort of reasons?

I suspect that your version of an emergency landing, and mine, are probably rather different. Using my definition, only once, when I went to Manila.

I've shut down a couple of engines over the years, and had various system failures (hydraulics, etc), and whilst they might require a different landing procedure, they're quite straight forward.

 

[Himeno]

I suspect that your version of an emergency landing, and mine, are probably rather different. Using my definition, only once, when I went to Manila.

I was going by how wiki defines it.
Emergency landing - Wikipedia, the free encyclopedia

As for the QF30... how far out of HKG were you when it happened? Why not go back to HKG? I was under the impression it happened only a short time after take off.

 

[jb747]

As for the QF30... how far out of HKG were you when it happened? Why not go back to HKG? I was under the impression it happened only a short time after take off.

Manila was closer than HK. I think we were about 250nm from Manila. We did consider returning to HK, because the runways there are slightly longer, but none of us were interested in flying any further than we had to...

 

[jb747]

I was having a play with some numbers for the Barcelona video, and wrote this on another site. Whilst probably not exact, I think it gives a little more context to the video.

"Whilst compression from a long lens is part of this, the 767 is at about roughly one wing span of height at the point where the 340 enters the runway. That would put him somewhere around half a nautical mile from his aim point (300' per nautical mile), so approximately 1,000 feet prior to the threshold. If I have the geometry of it right, the 340 is crossing about 4,200 feet down the runway...so they are separated by roughly 5,200 feet. The 767 would be approaching at about 220 feet per second, but he's about to land and slow dramatically, so let's say he were to average 150 feet per second. That would take him 34 seconds to reach the position of the 340. The 340 is moving at about 25 feet per second (15 knots), and so it will take him about 16 seconds to get his tail clear on the other side. So, they miss by about 18 seconds."

In my own flying, we often see aircraft cross in front of us, or take time to clear a runway after landing. ATC will also often advise you to 'expect late landing clearance', which is basically them telling you to keep going. The non flying pilot is normally watching this traffic, and will keep up a commentary of how things are going. The point at which you'll self initiate the go around is a variable target, but in round figures, about 100'.

So, the upshot of it all is that the 340 should not have crossed/been cleared to cross, but there was never any danger of a collision.

 

[under the radar]

just posting a general comment...reading the 'Ask The Pilot' thread is such a breath of fresh air for me.. just want to say thank you to jb747, and others, who contribute/enlighten me to their 'world', the real world, of flying ... I often 'run' to this thread to read sensible posts/answers....which gives me a break from all the other 'problems' that people have on this website... helps put things in perspective...and keeps me sane

happy and safe flying to all

 

[harvyk]

How early do you find out exactly which gate you will be using at the arrival airport? Is it something which is known before departure or is it something which is assigned whilst in the air / after landing?

 

[jb747]

How early do you find out exactly which gate you will be using at the arrival airport? Is it something which is known before departure or is it something which is assigned whilst in the air / after landing?

We generally find out around 200 miles out via ACARS....but, it's common for the first transmission to ATC 'ground' to give you a new gate.

 

[Awesom Andy]

We generally find out around 200 miles out via ACARS....but, it's common for the first transmission to ATC 'ground' to give you a new gate.

If that's the case, why do they still bother sending it via ACARS?

 

[Boris spatsky]

How early do you find out exactly which gate you will be using at the arrival airport? Is it something which is known before departure or is it something which is assigned whilst in the air / after landing?

On our short haul ops, we find out just prior to top of descent or sometimes on descent, normally via VHF radio. The gate is allocated before we depart on short sectors, but can easily change due to congestion, even after landing.

 

[jb747]

If that's the case, why do they still bother sending it via ACARS?

It doesn't always change, and ATC would end up massively congested if they had to tell every aircraft, every time. And also because the ACARs message contains other information (gates for transit passengers, next loading, water requirements, next operation of the aircraft, and anything else you can thing of).

 

[smeacs]

That would take him 34 seconds to reach the position of the 340. The 340 is moving at about 25 feet per second (15 knots), and so it will take him about 16 seconds to get his tail clear on the other side. So, they miss by about 18 seconds."

So in terms of time is there a Minimum time clearance between aircraft (similar to trainstations i believe) or is it measured in distance not time ?

 

[jb747]

So in terms of time is there a Minimum time clearance between aircraft (similar to trainstations i believe) or is it measured in distance not time ?

It's not really time or distance, but rather, position.

Standards vary around the world, but basically, when the landing aircraft actually lands, the runway must be clear. So, ATC (depending upon the country) may actually predict that the crossing aircraft will be clear, and issue a clearance on that basis. In the USA you're often issued with a landing clearance miles out, whilst the runway is very much occupied. In Oz, ATC wait until it's actually clear. There are downsides to either system. The US method may involve a clearance being revoked, whilst the Oz system can have an aircraft reach the point at which the crew initiate the go around, or have the late clearance over transmitted by other traffic.

Playing with the numbers from the other day again...if the 767 was 2,500 feet from his touchdown point (and I think he was most likely another 1,000 feet further out), then he was about 11 to 16 seconds from touchdown. So, at the shorter time, the runway would not have been clear for landing, but at the longer, it would have been fine. And if the 340 was actually going faster than the 15 knots that I used (and he could have been up to 30 knots), then the he would have been clear in either case.

Looking ahead, and making sure the runway is actually clear, is pretty basic airmanship. In IMC, ATC won't allow aircraft to cross the runway with traffic on the ILS (I forget the distance), as it can/will affect the ILS beam.

 

[alieninperth]

After a day in the 'office' are you more tired physically or mentally? Likewise after a period of leave do you find yourself more tired than usual?

 

[markis10]

It's not really time or distance, but rather, position.

In the case being discussed that's correct, but in the context of landing vs landing or take off preceding there are wake turbulence standards that need to be taken into account which are time based or in some cases distance, unless your in a super