Ask The Pilot

[harvyk]

Whilst I can see these being move to it's own thread.

The bag most likely exists so that pressure building up during an exhale doesn't push up against the oxygen generator / bottle. So it's likely to simply be a safety device to protect the system against excessive pressure building up which could cause the system to fail (eg via a burst pipe)

 

[Major]

I was watching a 738 being refuelled this morning and wondered how the operator acknowledges that has loaded the required quantity.
I assume he has some sort of spreadsheet of what is required for each aircraft but does he then have to notify someone of what he actually pumped in for it to be added to the loadsheet ?

 

[petercr]

Doesn't it work the other way round? I know JB has said previously that he'll ask for a certain amount of fuel to be loaded and then wouldn't it just be just a matter of watching the flow and stopping when it got there?

 

[ChrisGibbs]

JB747 - was on Sunday evening 31/5 QF1 service from Sydney - Heathrow via Dubai. We got away on time taking a very southerly track just to the north of Adelaide and crossing the West Australian coast just north of Geraldton then over Columbo, Sri Lanka the southern tip of India and on up to Dubai. At the top of descent the Captain gave the PA that we were expecting an on time arrival and that ATC had not given us any holding into Dubai. We descended from FL400 down to FL200 then entered into the hold where we did 6 iterations of the hold descending down to FL140. All up the hold added another 45+ minutes to the flight landing into Dubai at around 1:15am. A couple of questions for you:

- During the winter months I was under the impression the jet stream was stronger across Australia at the southerly latitude with the routes to Asia and the Middle East initially taking a more Northerly track then turning more westerly once out of the jet stream. Does Operations pick the most optimum track for you based on known winds or can you change that depending on forecasts, etc?
- What sort of fuel holding do you have to take into Dubai (something around 60+mins based on last night) as well as fuel for an alternate as needed? How far off MTOW would you be leaving Sydney for Dubai in the winter months with the additional requirements for fuel?
- Flying into Heathrow this morning at their peak (around 6:55am) seemed to be "normal" compared to Dubai which always seems to throw in at least 25-45 minutes of holding. I recognise they are completely different airports however are there any procedures that make Dubai more complex than Heathrow which would have a similar number of movements at its peak?

Thanks in advance....

 

[jb747]

I was watching a 738 being refuelled this morning and wondered how the operator acknowledges that has loaded the required quantity.
I assume he has some sort of spreadsheet of what is required for each aircraft but does he then have to notify someone of what he actually pumped in for it to be added to the loadsheet ?

On modern aircraft, the required fuel load is entered into the aircraft refuelling panel, and it will then cut off the refuelling at the required load, as well as controlling the distribution to the various tanks. The refuelling paperwork is then brought to the coughpit, and the pilots will sign off on it. The actual loading is transmitted by the aircraft, so load control can interrogate it directly.

 

[jb747]

JB747 - was on Sunday evening 31/5 QF1 service from Sydney - Heathrow via Dubai. We got away on time taking a very southerly track just to the north of Adelaide and crossing the West Australian coast just north of Geraldton then over Columbo, Sri Lanka the southern tip of India and on up to Dubai. At the top of descent the Captain gave the PA that we were expecting an on time arrival and that ATC had not given us any holding into Dubai. We descended from FL400 down to FL200 then entered into the hold where we did 6 iterations of the hold descending down to FL140. All up the hold added another 45+ minutes to the flight landing into Dubai at around 1:15am. A couple of questions for you:

I don't think I've been to Dubai from Australia and not held. The norm is about 4 runs around the pattern...and that's with no weather issues at all.

- During the winter months I was under the impression the jet stream was stronger across Australia at the southerly latitude with the routes to Asia and the Middle East initially taking a more Northerly track then turning more westerly once out of the jet stream. Does Operations pick the most optimum track for you based on known winds or can you change that depending on forecasts, etc?

The flight plan is run for just about all possible routes, using the forecast winds. They change from day to day, and around the middle of the flight, can be a thousand miles apart. On sectors across the Pacific, the planners can even change the route after departure.

- What sort of fuel holding do you have to take into Dubai (something around 60+mins based on last night) as well as fuel for an alternate as needed? How far off MTOW would you be leaving Sydney for Dubai in the winter months with the additional requirements for fuel?

Holding...and an alternate. I'd love that. You have a very optimistic view of just how much fuel aircraft arrive anywhere with. There are some decent alternates for Dubai (Muscat and Bahrain), and some less desirable. The decent ones require a lot of fuel, and would generally preclude holding at all. The others require less, but aren't places you necessarily want to go, or generally have exactly the same weather as Dubai. Once you start holding, you are pretty much committing to Dubai, or Dubai World. Many, if not all, departures from Sydney are are maximum weight. And that's before we start looking at adding fuel.

- Flying into Heathrow this morning at their peak (around 6:55am) seemed to be "normal" compared to Dubai which always seems to throw in at least 25-45 minutes of holding. I recognise they are completely different airports however are there any procedures that make Dubai more complex than Heathrow which would have a similar number of movements at its peak?

London has the best ATC in the world. Other places, less so. Dubai, seems to make things much worse than needed by descending aircraft earlier than we'd desire. If I have to hold, I'd rather be high, and I certainly don't want to be forced to descend a hundred or so miles early.

 

[flychrisfly]

If I have to hold, I'd rather be high, and I certainly don't want to be forced to descend a hundred or so miles early.

Why is that?

 

[AVC]

If not for inflation, what is the function of the bag?

Same theory as a resus bag set. You have a big rubbery bag that you squeeze, which works opposite to the lungs. You squeeze the bag, O2 goes in to the patient. Connected to this is a soft bag (reservoir bag)which is inflated by the flow from the O2 cylinder. The flow going into the reservoir bag is constant (we would normally use about 12-16 litres per minute), but the breathing (in this case assisted breathing) is cyclic.

In the aircraft, there is obviously no resus bag as the person is drawing in the O2 themselves (we hope). So the soft bag is just a reservoir. If the O2 flow was high enough to supply enough down the tube for the inspiration cycle, then it would be wasting O2 during exhalation.

Logically, the flow down the tube would be 50% of (average) inspiration rate. So about 8 litres per minute. Hyperventilators would just be getting more room air.

Even if the flow was only 4 LPM, times 300 PAX and that's a pretty reasonable amount of oxygen flow.

And while we are getting the ATP thread totally OT, a rebreather works opposite to the lungs. Exhale, lungs deflate, bag in the rebreather inflates. The exhaled air in a rebreather set has the CO2 scrubbed out, and adds O2 slowly, so you are reusing the same air (rebreathing it), as opposed to a SCUBA or CABA set that just has a big cylinder of compressed air that you breathe in, use a small amount of the O2 (about 20%of it), then dump the rest out into the environment, along with your exhaled CO2.

So you get about 30-60 mins on an average SCUBA set, but 4-6 hours on a rebreather. For a ton more money.

EDIT:

... to protect the system against excessive pressure building up which could cause the system to fail (eg via a burst pipe)

Or, as JB will attest to, a failed cylinder.

BTW, a tank is something you drive. A bottle is something you drink out of.And a cylinder is what is attached to the CABA . I still remember an instructor saying that one. So unquote.

As I recall the cylinders in (at least the 747 200s) are/were a steel cylinder wrapped with a kevlar composite, to withstand constant pressure changes. No oxygen generators (or O2 concentrators) on board. To generate enough O2 for 300 pax, they would be bigger that the air con packs.

Not sure how many cylinders are on board, but there must be many.

 

[por930]

Well, yes...the issue on the 30 was that because the bag did not inflate, some people thought they had no flow. But, given that the masks are open to the cabin anyway, and don't seal like the pilots' masks...then what is the exact purpose (of the bag). Or is there there one at all? Dunno.

As I recall JB, you were the captain of that flight QF30 where the failed cylinder caused some grief..... The full report makes good reading. http://www.atsb.gov.au/media/2409291/ao2008053.pdf

 

[jb747]

Why is that?

The fuel flow is higher at lower levels. The ideal height (if there is such a thing) for holding, is in the mid to high twenties. Additionally, if I do have to divert after holding for a while, if I'm already at altitude, I won't have to waste fuel climbing again.

 

[jb747]

As I recall the cylinders in (at least the 747 200s) are/were a steel cylinder wrapped with a kevlar composite, to withstand constant pressure changes. No oxygen generators (or O2 concentrators) on board. To generate enough O2 for 300 pax, they would be bigger that the air con packs.

Not sure how many cylinders are on board, but there must be many.

There were 17 on OJK. Two were dedicated to crew, and were are part of a separate system, and the remainder, in a couple of banks, provided passenger oxygen. They are just steel, no kevlar. They are about 800mm high, and about 200mm across...and hold the gas at 1800-2000 psi. The bottle failed (as best they can tell), just above the base. The only part that was found was the regulator, and that was because, in its journey, it hit the aircraft wall near door 2, and ripped the regulator off.

The failure mode of this particular bottle was against all expectations. The lead investigator was a metallurgist, and it was pretty obviously a metals issue, but with no part of the bottle from around the failure available, they were pretty much stymied.

I don't think anyone, especially the aircraft designers, had considered them to be dangerous when in situ.

 

[Quickstatus]

Good question, to which I don't have a definite answer. The cabin crew will pinch the exit side of the bag to check for flow, and it may be that it's a simply way to provide that function.

It's actually quite simple. The peak flow of gas during inspiration is x but it's only x for a short period of the entire breathing cycle. You can design a system which delivers a flow rate of x all the time but will require a very large system and will waste a lot of oxygen. The bag serves as a reservoir. So that during inspiration the volume inspired comes from the oxygen tube plus oxygen in bag plus ambient air. The masks are not airtight for safety so excess pressure in mask will not burst the lungs - rather it will flow to the atmosphere.

So the reservoir bag serves to augment the oxygen concentration during inspiration while making the whole system efficient by minimising oxygen wastage.

the system is found in many oxygen masks in hospital and is used by the manual ventilation systems in ambulances and hospital emergency situations

the overall effect is that while the oxygen tube delivers 100% O2 (hospital). The net inspired concentration of oxygen is about 30-40%. The reservoir bag can increase this to maybe 50-60% depending of respiratory rate, volumes. So a big person will get a lower O2 inspired concentration using the same mask than a small person. That's the other reason for the reservoir bag - to cater for different inspired volumes

 

[QF WP]

An Airbus A330 was taxiing along the runway at Manchester Airport when its right engine suddenly developed a fault and exploded. (couldn't see a date)

https://au.news.yahoo.com/video/watch/17756762/passenger-jet-engine-explodes-before-take-off/#page1

Audio is supplied of ATC and the pilot in a brief conversation after the event. jb747, can you tell (or estimate where you think they were) on the take off roll (V1, rotate, or V2)?? What would have been the protocol for the flight crew in this event (explain what procedures they would have gone though in this incident).

 

[jb747]

An Airbus A330 was taxiing along the runway at Manchester Airport when its right engine suddenly developed a fault and exploded. (couldn't see a date)

He certainly isn't taxiing...it's the take off roll.

Audio is supplied of ATC and the pilot in a brief conversation after the event. jb747, can you tell (or estimate where you think they were) on the take off roll (V1, rotate, or V2)?? What would have been the protocol for the flight crew in this event (explain what procedures they would have gone though in this incident).

Firstly it's at a speed of less than V1. The option to abort basically expires at that speed. An abort from beyond V1 is, 99% of the time, a screw up, and likely to end badly.

The spotter who caught this was lucky to grab such a rare event. The engine fails, and as it does, the aircraft starts to yaw. It's barely moved, and you can see the rudder displaced against the turn (which is the pilot's reaction). He's caught it very quickly, and ultimately the aircraft hardly moves off the centreline. Both thrust levers would be slammed closed. The spoiler rise shows when the thrust levers are closed (as this action trips the spoilers in the abort case). Reverse is selected on both engines (and you can see the doors open), but obviously only one will give any thrust at all....the level is low enough that the asymmetry is barely noticeable. Automatic braking, right up to the anti skid, would have kicked in as soon as the thrust levers were closed. There is a speed for this, 72 knots in the 380, and I assume similar in the 330. Below that speed, the system won't activate in RTO mode.

Once they come to a stop, they would park the brakes, and have a look at whatever the the ECAM had to say. They'd action whatever was required at that point.

 

[whatmeworry]

Will I really blow up a plane by using a phone/mobile nearby a refuelling plane?

Mobile phones and petrol stations › Dr Karl's Great Moments In Science (ABC Science)

 

[jb747]

Will I really blow up a plane by using a phone/mobile nearby a refuelling plane?

Mobile phones and petrol stations › Dr Karl's Great Moments In Science (ABC Science)

You could probably stand in the middle of a puddle of AVTUR and throw a lit match into it, and not do anything. But, I don't see any particular reason to personally test it.

 

[raleyoz]

I think this can go in here?
Walking past my 2 A380's last night I noticed 3 dials/ indicators above the nose but under the coughpit Windows, they looked like analogue clocks , can I ask what do they do??

 

[jb747]

I think this can go in here?
Walking past my 2 A380's last night I noticed 3 dials/ indicators above the nose but under the coughpit Windows, they looked like analogue clocks , can I ask what do they do??

Side slip probes. Basically the same as an angle of attack probe, but measuring flow across the aircraft. One for each air data computer.

 

[benzoenator]

Hi JB. Not sure if you've been asked this question before (either in this thread or somewhere else online), but I've just stumbled across an article - presumably well published at the time - written by a pilot where he suggests a possible explanation of the disappearance of MH370 is that the pilots intercepted a passing 777 and flew in close proximity, as as to avoid radar detection, until it reached the Middle East. The article is at www.keithledgerwood.com/post/79838944823/did-malaysian-airlines-370-disappear-using

Do you have any thoughts on this theory? I assume it's fairly far-fetched given that it hasn't received any media attention since the disappearance, but seemed quite intriguing on a detailed read.

 

[jb747]

Hi JB. Not sure if you've been asked this question before (either in this thread or somewhere else online), but I've just stumbled across an article - presumably well published at the time - written by a pilot where he suggests a possible explanation of the disappearance of MH370 is that the pilots intercepted a passing 777 and flew in close proximity, as as to avoid radar detection, until it reached the Middle East. The article is at keithledgerwood. com/post/79838944823/did-malaysian-airlines-370-disappear-using

Do you have any thoughts on this theory? I assume it's fairly far-fetched given that it hasn't received any media attention since the disappearance, but seemed quite intriguing on a detailed read.

It got plenty of attention. Basically far more than it deserved.