Ask The Pilot

[jb747]

A few questions if I may.
Why is it that, as soon as the descent starts, it gets bumpy? All of a sudden it is a nice smooth cruise, and then the bumps appear.

Boris has answered this...we had a good example going into London the other morning. We'd found lots of bumps over Europe, and climbed to get out of them. But, as we started descent we ran into a 50 knot wind shear, and it was quite rough for a minute or two. Sadly, you can't leave out the middle bit of a descent.

Also, I flew MEL-HOB this morning and I could feel and see the aircraft swaying side to side for a couple of minutes. It wasn't bad but felt like I was on a boat. Is that just the wind that the aircraft has to contend with?

Aircraft can react in different ways to various disturbances. Some aircraft will 'dutch roll', and that can be quite uncomfortable. https://en.wikipedia.org/wiki/Dutch_roll

One for JB- Would you happen to know your October roster yet? Oct 29 to LAX if your roster manager takes special requests.

The rosters aren't out yet, but I know what I'll be doing then. On leave again. It wasn't what I wanted, but I ended up with two leave slots relatively close together.

I've just been playing with my bids for the next roster period, and a combination of the leave (which the system cannot move), and the flight hours from trips I've already been allocated, has the effect of severely constraining the potential roster. Not all flights ex Melbourne are crewed by people based there, so that limits the choices. As best I can work out with my pencil and paper, I'll have to do the London trip that starts on 8/10, and could do either of the LAs that start 21, 22, 23/9. I can't see any other way for the roster to work, so I will be interesting to see if the computer system finds another solution.

 

[RooFlyer]

Prompted by some observations out on the SYD main NS runway from my hotel room this afternoon.

Say a small (10-20 seater) plane is on the runway, supposedly ready for its take-off roll and for whatever reason, it can't commence that roll - its just sitting there. Now say there are large jets in-bound, expecting their touchdown slots in a few minutes.

First, what are the 'rules' in Australia? Does the small aircraft pilot have the 'right' to go through his checklists and do immediate troubleshooting and occupy the runway for a few more minutes at least, causing the plane behind (and possibly a second) to go-around? Or, if the small plane (or a big one for that matter) can't depart within the time frame allocated, is the small plane obliged to vacate the runway immediately, if it can?

If ATC sees the small plane sitting there, not commencing an expected take-off roll and obviously obstructing the in-bound planes, would it initiate contact with it with a view to ordering or 'request' it to vacate the runway "NOW", if the plane can move but not take-off?

 

[andmiz]

First, what are the 'rules' in Australia? Does the small aircraft pilot have the 'right' to go through his checklists and do immediate troubleshooting and occupy the runway for a few more minutes at least, causing the plane behind (and possibly a second) to go-around? Or, if the small plane (or a big one for that matter) can't depart within the time frame allocated, is the small plane obliged to vacate the runway immediately, if it can?

If ATC sees the small plane sitting there, not commencing an expected take-off roll and obviously obstructing the in-bound planes, would it initiate contact with it with a view to ordering or 'request' it to vacate the runway "NOW", if the plane can move but not take-off?

There's no 'rules' as such, just the expectation of a little bit of professionalism. Runway occupancy times are closely monitored, with all sides of the industry doing what they can to minimise time spent on the runway, and highly likely they'd get a quick prompt from ATC to either depart or taxi off the runway and then continue troubleshooting....provided one of those options was safe in every means (and if they're safest by not moving, then so be it). An theoretical example in a theoretical small aircraft which I can think of, would be an indication that the park brake was still set....you can't takeoff with it, and don't want to taxi with it, because even if you thought the brake was in fact released, there is a risk of brake fire and FOD.

Occupying a runway for those few extra seconds can have huge consequences, with one or several arrivals having to be slotted back into the arrival flow, and the subsequent arrivals behind those delayed. It can easily cost the industry 30 minutes by occupying the runway for that one extra 1 minute, or how many hundreds of thousands of dollars that costs overall. That said, if they need that minute on the runway to ensure their safe operation, then its theirs to take.

Now...if you viewed some of this occurring from your hotel room, it could in fact be for wake turbulence separation (especially since it was a small aircraft at a large airport), rather than the aircraft waiting to run a checklist or sort out a technical fault.

 

[williamsf1]

A question for Boris or any other operator of similar aircraft – this was a departure from FRA recently. What could have been the issue here? Incorrect weight settings or something else ?

I guess FRA is a longer runway so maybe more room for error ?

Terrifying moment passenger jet fails first take-off attempt at Frankfurt Airport | Daily Mail Online

 

[jb747]

A question for Boris or any other operator of similar aircraft – this was a departure from FRA recently. What could have been the issue here? Incorrect weight settings or something else ?

I guess FRA is a longer runway so maybe more room for error ?

Terrifying moment passenger jet fails first take-off attempt at Frankfurt Airport | Daily Mail Online

Interesting footage.

Even though the article claims it was calm, you can hear the wind on the soundtrack.

Possible reasons...
Incorrect flap setting
Early rotation
Wind gust either removing some of the headwind, or even worse, increasing tailwind component.

The comments are, as usual, largely gibberish. Aborting is not an option. I doubt that it's trim. That could give an early rotation, but you'd expect to see some nose down elevator in an attempt to stop it. He's actually done well not to have a tail strike. My feeling is that it's wind related.

 

[Captain Halliday]

What's the flaps setting for a 737 takeoff?

In that video the leading edge slats seem to be down. It's hard to tell how much flap is selected, but it doesn't appear much.

 

[jb747]

What's the flaps setting for a 737 takeoff?

In that video the leading edge slats seem to be down. It's hard to tell how much flap is selected, but it doesn't appear much.

There will be a number of flap settings that can be used. The early settings will give the slats and possibly an area increasing setting at the rear, without much/any rear droop. There is a takeoff configuration warning, and in some aircraft there is a comparison of the FMC flap setting and the actual setting. Frankfurt has pretty long runways, so the use of a setting with minimal rear droop is quite likely (it will use a higher Vr, but will give a better 'second segment', and less noise). Second segment is the initial part of the climb. aircraft performance - How are take-off segments defined? - Aviation Stack Exchange

I guess that it's possible that they have less flap than they'd done the calculations for, whilst still being a take off setting.

As the take off track passes under the approach path of the A330, I wonder if there could even be a wake issue.

 

[williamsf1]

As the take off track passes under the approach path of the A330, I wonder if there could even be a wake issue.

Appears you were spot on!

From AV herald

In response Royal Air Maroc tweeted a French statement in 5 parts translated by The Aviation Herald: "Following dissemination of false information about flight AT-811 of July 23rd, Frankfurt - Casablanca, we wish to clarify that Frankfurt tower advised the captain of our flight in question of possible wake turbulence as result of a simultaneous landing of an A330. As result the captain performed a maneouver to accelerate in order to achieve speeds which permitted safe takeoff."

 

[Captain Halliday]

Tonight's QF477 MEL-SYD departed 34R and made a couple of right turns. Just past Wollongong it reached FL250 and almost immediately descended to FL200 and not long after descended further to FL180.

https://flightaware.com/live/flight/QFA477

Flight aware says planned altitude was FL240, though I have no idea how reliable that is. FR24 showed the QF and VA aircraft ahead at FL400 and FL380 respectively. The JQ aircraft following was at FL360. A quick look at BoM shows no significant or widespread weather of note on that route. So my questions:

1. What might have been the reason(s) to select FL240. It would seem lower than usual, but is it that unusual?

2. What might have prompted the descent so early in the flight?

3. If weather is a possible cause, why select FL240 to begin with? If isolated weather, why descend rather than climb?

4. Are there any Mel items that would allow the flight to proceed, but with an altitude restriction?

 

[jb747]

1. What might have been the reason(s) to select FL240. It would seem lower than usual, but is it that unusual?

In itself, FL240 is not that unusual. Low, but not outlandish. It was an altitude I've often used on the way to Perth. I don't have access to the flight plan weathers, so I don't know if that provided a reason.

2. What might have prompted the descent so early in the flight?

No idea. It's an unusual profile.

3. If weather is a possible cause, why select FL240 to begin with? If isolated weather, why descend rather than climb?

Climbing over weather is rarely a good idea. We normally go around it. We used to go low on that route in the 767 if we were chasing groundspeed, and could afford the fuel burn.

4. Are there any Mel items that would allow the flight to proceed, but with an altitude restriction?

On the 737, I don't know. On the 767, there was an altitude limitation if a pack was MELed. FL280 if memory serves... I'd expect a similar restriction on any twin pack aircraft.

 

[Boris spatsky]

Yep, i would assume one pack out. No significant jet today to justify that level as far as i can tell.

 

[Captain Halliday]

On the 737, I don't know. On the 767, there was an altitude limitation if a pack was MELed. FL280 if memory serves... I'd expect a similar restriction on any twin pack aircraft.

Yep, i would assume one pack out. No significant jet today to justify that level as far as i can tell.

What is a pack?

 

[Boris spatsky]

What is a pack?

Air conditioning pack which in a twin engine aircraft provides about half of the air to the pressurisation system. One pack operation limits how high you can fly because the volume of air available to pressurise the cabin is less.

 

[mjt57]

Air conditioning pack which in a twin engine aircraft provides about half of the air to the pressurisation system. One pack operation limits how high you can fly because the volume of air available to pressurise the cabin is less.

Do you need both engines to provide adequate cabin pressure?

I'm guessing that a single engine op would limit the ceiling of a twin as well. Or can one engine feed two packs?

 

[Boris spatsky]

Do you need both engines to provide adequate cabin pressure?

I'm guessing that a single engine op would limit the ceiling of a twin as well. Or can one engine feed two packs?

Yes, both engine bleed air systems are required to keep the cabin below 10000 feet (which is the requirement for passengers and crew) when the aircraft is in the normal cruise levels above 30000 feet.

One bleed air system alone cannot keep the cabin low enough for the aircraft itself to stay that high on most twins. So you have to descend to a level where one bleed air system can cope and keep the cabin below 10000 feet - this is normally around 24-26000 feet aircraft altitude, aircraft type dependant.

Both engines can be working, but one bleed air system might be isolated due to a system fault. So the crew can dispatch in that case in accordance with the Minimum Equipment list, but the aircraft cannot climb above the 24-26000 feet altitude limit.

This is different to the cruise limit with one engine inoperative - twins will generally descend into the mid to low 20s with one engine out, which is an aerodynamic/thrust limit issue.

 

[jb747]

Despatch with a pack out is quite reasonable, especially on domestic operations. It can be limiting on long haul ops as the lower altitude will have too much effect on fuel burn. I'm told that in this case, it was too rough at FL240, hence the lower altitudes. Pity it was night time, as the view would have been much better than usual.

On the 767, either engine was capable of providing enough bleed air to run both packs, so that didn't provide an altitude limit. But, losing an engine means you can't get anywhere near as high anyway, so basically you run out of thrust before you run out of air. Having a bleed selected off (i.e. both engines, but only one providing air) may have had an altitude limit (I don't have a copy of the MEL), but looking at the checklist, there is no requirement to descend for loss of a pack or a bleed source.

 

[jb747]

I made a prediction a couple of weeks ago, about what my next roster would look like. As it turned out, the computer couldn't think of anything different, so I got it spot on.....

Anyway...

93 ex Melbourne 21/9
94 ex LA 23/9

9 ex Melbourne 8/10
1 ex Dubai, 11/10
10 ex London 13/10
10 ex Dubai 16/10

The rest of the roster is leave.

 

[CaviAck]

I made a prediction a couple of weeks ago, about what my next roster would look like. As it turned out, the computer couldn't think of anything different, so I got it spot on.....

Anyway...

93 ex Melbourne 21/9
94 ex LA 23/9

9 ex Melbourne 8/10
1 ex Dubai, 11/10
10 ex London 13/10
10 ex Dubai 16/10

The rest of the roster is leave.

How long does this roster run till?

 

[jb747]

How long does this roster run till?

Long haul rosters are 56 days. Starts on 19/9.

 

[Flying Fox]

Questions about refuelling -

1. Are aircraft always refuelled from one particular side?

2. Can refuelling be done on either side?

3. Can refuelling be done on both sides simultaneously and would it be any faster?

Thanks