Ask The Pilot

[Quickstatus]

You can get into all sorts of things when you start looking

I remember telling my Dad that the Wright Brothers did not have a cambered wing - just flat like my Kites. It was also too hard to build a Kite with a cambered surface. And when I got into model airplanes we had a flat wing which also flew...
We went down the rabbit hole of trying to discover why ( back in the days before internet). The local library was where i found the answer.

upwind offsets

Or just fly higher than the usual Big jet traffic in the area?. The smaller jets seem to have a higher ceiling?. Though i understand it may not be available.

 

[JohnM]

The rejected CX B777 takeoff and subsequent slide deployment covered by Juan Browne:

.

Pilots, any further comments as to why they may have kept moving back to the gate instead of stopping just off the runway?

 

[jb747]

Or just fly higher than the usual Big jet traffic in the area?. The smaller jets seem to have a higher ceiling?. Though i understand it may not be available.

They have weight/performance/ATC issues too. Higher may not be available, and if they do get it, they're blocking heavies that may want it. I don't know how ATC treat them in the airspace, but I'd be annoyed if some biz jet were holding the airline stream down. If anything, they can afford the fuel. In any event, an offset would almost always be available.

 

[Quickstatus]

offset would almost always be available

How many nm?

 

[jb747]

How many nm?

For wake? One would be enough, as long as it's upwind.

The rejected CX B777 takeoff and subsequent slide deployment covered by Juan Browne:

.

Pilots, any further comments as to why they may have kept moving back to the gate instead of stopping just off the runway?

To be 100% honest, I'm not all that taken with Juan's channel. Reading from AvHerald and the media isn't anywhere the level of research done by Mentour.

The questions I have are related to why they left the runway so quickly. They could have used more of it, and that would have meant a lot less heat. And then their taxi to the gate would have been a negligible distance, and would have been more acceptable. The brake temps would have lagged somewhat too, so the overtemp warning might not have come up immediately. He seemed to miss that the evacuation was apparently not ordered from the coughpit too (though that is to be confirmed). As best I can tell there has been no brake fire, just the fusible plugs going...so there was never any reason to evacuate anyway.

When Juan held up the ipad showing the brake temp display, he didn't explain what you were seeing. The 160 is the tyre pressure. The temps are a scale from 0 to 9. AB show the actual temperature.

I'm yet to hear why they aborted. Even if they weren't at V1, an abort above 100 knots is generally for something very serious, not just remembering that you forgot to pack your lunch.

 

[JohnM]

To be 100% honest, I'm not all that taken with Juan's channel. Reading from AvHerald and the media isn't anywhere the level of research done by Mentour.

I agree. However, the way I see it is that they run at different timing, levels and styles.

Juan comes in contemporaneously about an incident with some technical explanation that I, as an amateur, value at the time. But I recognise with that come assumptions that may not turn out to be correct, missing information or gratuitously judgmental comments.

Mentour's analyses are exceptional in my view, but they come after the final report which may be years later.

 

[xt_20]

Well, most of the flights you were looking at would have been domestic of some sort, and they generally don't need anywhere near as much runway as the longer/heavier flights. QF1 and QF11 both used either 34 or 16.

Thanks jb747. I thought I recall a CI A330 using 07/25 as well.

 

[jb747]

I'm yet to hear why they aborted. Even if they weren't at V1, an abort above 100 knots is generally for something very serious, not just remembering that you forgot to pack your lunch.

Prune seems to be of the opinion that they aborted due to invalid air data. To be confirmed. If that is the case though, they should never have reached anywhere near 150 knots of groundspeed. There's a check at (80 or) 100 knots, where basically the non flying pilot will call 100, and the flying pilot is supposed to x-check to his display. One scenario I can think of, is that the non flying pilot's IAS was very slow, or never, reached 100. But, whilst that might work if it was the FO's side, the Captain has two displays, of different data, more or less directly in his line of sight, and should be aware of any split between them, even before 100kts. And if they aren't split, then there's no reason to abort, even if the FO's side does not work at all.

There are 4 IAS sources. Three are via the air data computers, and one via the standby display. These are totally separate systems. The Captain will be selected to one source, and the FO another. The standby display only shows it's own source. Upon loss of one, the affected side will be selected to the unused source. It is possible to select both sides to the same source, but that throws up a warning. For what it's worth, QF30 ended up on single source. You need to be careful in that scenario, but you lose nothing.

 

[Quickstatus]

150 knots of groundspeed

What's estimated V1 and V2

 

[jb747]

What's estimated V1 and V2

I can make a guess, but without access to the performance charts, for that specific runway, I can't give you a solid answer. At a guess though, I'd say about 160 and 185.

Remember that V1 is not the same as Vrefusal. In practice, it's treated as such, but the reality is that V1 is the slowest airspeed from which you can continue the take off, after loss of an engine, and cross the fence at a defined height (about 35'). On a very long runway, or at a light weight, you could, in theory stop the aircraft from a later stage, but history has shown that this is such a dangerous avenue, that V1 is always treated as if it's the last point from which you can stop.

 

[jb747]

How to give the passengers a good view.

 

[serfty]

How to give the passengers a good view.
...

When was that taken?

That airstrip has not been a shadow of what it was in its heyday for a long time.

 

[jb747]

When was that taken?

That airstrip has not been a shadow of what it was in its heyday for a long time.

1984 Southern Cross Air Race. The new runway was already in use.

 

[Saab34]

JB, did you have a buffer on your A380 flights if a cabin crew called in sick either at home base or abroad? Ie, if one called in, you could still legally operate?

 

[jb747]

JB, did you have a buffer on your A380 flights if a cabin crew called in sick either at home base or abroad? Ie, if one called in, you could still legally operate?

Cabin crew. Is that aft of the coughpit door?

You needed one qualified person per door during take off and landing, and one cabin crew member per 36 passengers is (I think) the CASA requirement. So, the limiting number would be 16 (one per door) which would give you a loading of 576 passengers, which is greater than we could possibly carry. I thought I had some old crew lists, but can't find them at the moment. The nominal cabin crew was 18-20, so there's a bit of margin for sickness.

You could, if needed, put an SO on a door for the landing, though I don't recall hearing of anyone actually doing so.

 

[flyingfan]

I saw an article about a Houston-Amsterdam flight being diverted to Chicago due to a pax disturbance. The flight had to circle near ORD for what was presumably a while to burn fuel.

Given there was no airworthiness issue and assuming no weather problems either, would it have made better sense to aim for say Maine, by which time more fuel would have been burnt, offload the pax there and continue? Rather than doing loops around ORD? Presumably they wanted to land ‘soonish’ to offload the pax but it seems they couldn’t land earlier while being overweight, so the time, fuel and distance seems to be wasted.

 

[Warragul]

Assuming the choice of airport was for the airline alone, I imagine operationally it would be easier to replace the crew if needed at ORD than somewhere like Maine.

 

[jb747]

I saw an article about a Houston-Amsterdam flight being diverted to Chicago due to a pax disturbance. The flight had to circle near ORD for what was presumably a while to burn fuel.

It was holding for just on 30 minutes. A 777 would burn about 4 tonnes in that time, so the burn down idea doesn't really work. But dumping fuel, would take about around that. So, assuming they're dumping, ATC do not want them drawing a line with fuel across the upper USA.

Given there was no airworthiness issue and assuming no weather problems either, would it have made better sense to aim for say Maine, by which time more fuel would have been burnt, offload the pax there and continue? Rather than doing loops around ORD? Presumably they wanted to land ‘soonish’ to offload the pax but it seems they couldn’t land earlier while being overweight, so the time, fuel and distance seems to be wasted.

You logic is sound, but as mentioned above, you generally can't just dump en-route. I'd expect they have better support in Chicago that at Bangor (?). Turnaround was pretty rapid.

Assuming the choice of airport was for the airline alone, I imagine operationally it would be easier to replace the crew if needed at ORD than somewhere like Maine.

The crew were not replaced. Look at the timings.

 

[Saab34]

Gents. Any idea what you think went wrong here? Didn’t seem to be in a hurry getting the nose back on the deck either.

 

[jb747]

Gents. Any idea what you think went wrong here? Didn’t seem to be in a hurry getting the nose back on the deck either.

Flare is too late. There is no attempt to correct the aircraft drift prior to touchdown. Pitch control is so rigid, that I wonder if they aren't hitting an FBW limit. If you aren't aligned with the runway, you don't really want to put the NG down, as then it will charge off towards wherever it's pointed.

In my experience with Airbus FBW, once you're below 100' then it's effectively direct law in pitch, with no limiting to stop you hitting the tail. I expect that the 350 FBW is somewhat more vocal about this.