Ask The Pilot

[docjames]

Aviation is all about options. We do everything possible to keep as many options open as possible. Fuel is the greatest giver of options, because it allows the luxury of time (or miles). Departures from LA to Melbourne do not have an alternate to destination as a matter of course. If the weather is good, that's a waste of about 10 tonnes of capacity, that is rarely needed. This only becomes relevant towards the end of the flight, as for the most part of the journey, you have the choice of many airports within (potentially) thousands of miles. In fact, for most of the journey, you'd be dumping many tonnes of fuel if you had to go anywhere else.

Departures from LA (to Melbourne) are almost always at maximum brakes release weight. The chances are that we simply cannot carry any holding or alternate requirements for Melbourne, without offloading a large number of passengers. And most likely we won't actually need the fuel at the end, as the prediction that we have to use is about 20 hours into the future..they get better as you get closer. So, in simple terms (shock, horror), we may depart LA without sufficient fuel for the mission.

But....

Along the way there are a number of primary alternates, with the last one being Sydney. As long as we keep our fuel reserves above the line for any point that we could use (at all times, with no gaps), we can continue. If you can keep it above the line to destination, then you get to go there..

Apologies if this seems a dumb question, but in such a (seemingly, everyday) scenario, if you are on approach to MEL and the aircraft ahead of you manages becomes disabled on the runway and subsequently impeding both runways (breaks down at intersection for example), do you carry sufficient fuel to return to SYD or ADL? Or would you be therefore forced to hold awaiting clearance, or to use AVV or any other alternative (is AVV A380 capable - understanding there's a difference between "preferred" and "in an emergency" use)?

 

[D747]

I have a question that relates to very large aircraft design. It seems that the relationship between the placement of the jet engines and the wings themselves is very interesting and complex. Wings are very low on the standard jet fuselage and then the engines are on pylons that push them forward of the wing. What is the reason for this design please? Could the wing be moved forward and then the engines be on pylons that are just straight below the wing for example? Also does the jet blast leave the engine without enlarging very much as it moves back across the underside of the wing? I ask this because it seems that when the flaps are extended fully it must be a close thing for the blast to miss the lowest part of the flap, even with the small gap provided in the flaps.

 

[jb747]

Apologies if this seems a dumb question, but in such a (seemingly, everyday) scenario, if you are on approach to MEL and the aircraft ahead of you manages becomes disabled on the runway and subsequently impeding both runways (breaks down at intersection for example), do you carry sufficient fuel to return to SYD or ADL? Or would you be therefore forced to hold awaiting clearance, or to use AVV or any other alternative (is AVV A380 capable - understanding there's a difference between "preferred" and "in an emergency" use)?

There are many ways to build up this sort of scenario. The simple answer is that no, you don't always have fuel to go somewhere else. Nor would you necessarily have fuel to hold for more than a few minutes. In the case of Melbourne, there would a charge, of many aircraft, to Avalon, though the smaller aircraft could probably use Essendon at a pinch.

But, you could be left with the option of landing on whatever part runway is clear, or of using the taxiway. I'm sure an internet search will find you examples of both.

 

[jb747]

I have a question that relates to very large aircraft design. It seems that the relationship between the placement of the jet engines and the wings themselves is very interesting and complex. Wings are very low on the standard jet fuselage and then the engines are on pylons that push them forward of the wing. What is the reason for this design please? Could the wing be moved forward and then the engines be on pylons that are just straight below the wing for example?

The wings are placed where they are so that the centre of lift is approximately at the same for and aft position as the centre of gravity. Balance for want of a better term.

The engines are not slung under the wings in an attempt to migrate the effects of unconfined failures, amongst, I'm sure, many other reasons. I can't see a positive to having them directly underneath.

Also does the jet blast leave the engine without enlarging very much as it moves back across the underside of the wing? I ask this because it seems that when the flaps are extended fully it must be a close thing for the blast to miss the lowest part of the flap, even with the small gap provided in the flaps.

I'm sure it expands, but the flap gap is only a relatively short distance behind, so I doubt that it's a big issue. Some blast does impinge on flaps. For example when reverse thrust is selected on the 747, it automatically retracts the inboard leading edge flaps.

 

[Franky]

JB - apologies for the delay in responding to the thread of 19JUL17, which contained the Wiki thread about the Skyhawk A4Gs you once flew. The article was a little disparaging about the capabilities of the RAN version compared to the A4F. Your thoughts? Along with a lot of info about the Skyhawks, the Wiki article also gave a précis of the life of the carrier that I found interesting. I served on the Big M in 1963 and 1981, as well as at Nowra in 1969 and 1975. The article also mentioned the number of losses of A4s over the years, but missed one in 1969 when the pilot landed during a sudden squall over the airfield. Unfortunately, he crashed off the end of the runway into trees and was left a paraplegic as a result. From memory, he was formerly an RCAF pilot whose name was Ian Goodfellow (or Goodenough).


The article also discussed the desire of the RAN to replace the carrier with the Invincible, along with a squadron of Harriers. Whilst I was serving on the staff of ANA Washington 1977-79, we had one of our A4 pilots posted for exchange service with the Marines in South Carolina to gain experience operating the Harriers, but can’t recall his name. We also had another A4 pilot, a young SBLT whose name was ‘Bruiser’ Baddams, who was posted to fly with the USN at Brownsville in Texas. He would occasionally programme a nav exercise from Brownsville to Andrews AFB and come and visit the Embassy. He would fly back with a carton of Aussie beer under his seat! There was also a LEUT whose name I can’t recall posted to Patuxtent River to undergo a Test Pilots course. Needless to say, his was the most expensive course we had to pay for amongst the many of our RAN personnel under training in the US in those days.



Forgotten names aside, did you ever cross paths with any of these fellow pilots during your time in the RAN?

 

[Quickstatus]

Would appreciate some insight into the reason for speed profile for today's QF7 SYD-SYD flaps issue. Did not proceed to DFW. Fuel dump occurred while circling - heading 90[SUP]0[/SUP] then 270[SUP]0[/SUP]

My guess is there is headwind on one direction causing G/S to be low then once the aircraft turns in the opposite direction the tailwind makes the G/S faster.

 

[Melburnian1]

When fuel is dumped from an A380 (today's QF7 return to SYD saw the aircraft typically at 8,150 ft - just under 2,500m - while this was occurring) how many kilograms of fuel per minute are typically disgorged?

 

[jb747]

JB - apologies for the delay in responding to the thread of 19JUL17, which contained the Wiki thread about the Skyhawk A4Gs you once flew. The article was a little disparaging about the capabilities of the RAN version compared to the A4F. Your thoughts? Along with a lot of info about the Skyhawks, the Wiki article also gave a précis of the life of the carrier that I found interesting. I served on the Big M in 1963 and 1981, as well as at Nowra in 1969 and 1975. The article also mentioned the number of losses of A4s over the years, but missed one in 1969 when the pilot landed during a sudden squall over the airfield. Unfortunately, he crashed off the end of the runway into trees and was left a paraplegic as a result. From memory, he was formerly an RCAF pilot whose name was Ian Goodfellow (or Goodenough).

No, they didn't miss one. The accident you refer to was a Sea Venom.

The A4 losses were:
A4G engine failure (Tony Derkinderen)
TA4G loss of control (fatal)
A4G soft catapult shot (Barry Evans)
A4G broken arrestor wire (Kevin Finan USN)
A4G mid air collision at the bombing range (fatal)
A4G engine failure during ACM near Bega (Colin Tomlinson)
TA4G engine failure in the circuit (Andy Sinclair)
A4G rolled over the side of the ship during an attempt to move it
A4G soft catapult shot (David Baddams - Bruiser's little brother)
A4G engine failure during the cat shot (Clive Blennerhasset)

Disparaging compared to the A4F...strange, given that they were modified A4Fs.

I was at Nowra in 75, but at the Seaking end of the base.

The article also discussed the desire of the RAN to replace the carrier with the Invincible, along with a squadron of Harriers. Whilst I was serving on the staff of ANA Washington 1977-79, we had one of our A4 pilots posted for exchange service with the Marines in South Carolina to gain experience operating the Harriers, but can’t recall his name.

In that time frame it would most likely have been John Siebert.

We also had another A4 pilot, a young SBLT whose name was ‘Bruiser’ Baddams, who was posted to fly with the USN at Brownsville in Texas. He would occasionally programme a nav exercise from Brownsville to Andrews AFB and come and visit the Embassy. He would fly back with a carton of Aussie beer under his seat!

I wasn't aware that Bruiser did an exchange. It would have been after I left to instruct with the RAAF.

There was also a LEUT whose name I can’t recall posted to Patuxtent River to undergo a Test Pilots course. Needless to say, his was the most expensive course we had to pay for amongst the many of our RAN personnel under training in the US in those days.

Pax River...not sure in that time frame, but I'd suggest it was most likely one of the Tracker guys.

Forgotten names aside, did you ever cross paths with any of these fellow pilots during your time in the RAN?

I knew them all, and still in touch with some.

 

[jb747]

Would appreciate some insight into the reason for speed profile for today's QF7 SYD-SYD flaps issue. Did not proceed to DFW. Fuel dump occurred while circling - heading 90[SUP]0[/SUP] then 270[SUP]0[/SUP]

My guess is there is headwind on one direction causing G/S to be low then once the aircraft turns in the opposite direction the tailwind makes the G/S faster.

That's exactly it. Have a look at the IAS. I expect that to have been pretty stable. The downward trend in the average speed is probably commensurate with the weight loss during the fuel dump.

 

[jb747]

When fuel is dumped from an A380 (today's QF7 return to SYD saw the aircraft typically at 8,150 ft - just under 2,500m - while this was occurring) how many kilograms of fuel per minute are typically disgorged?

About 2,500 kgs per minute.

 

[Boof1]

About 2,500 kgs per minute.

Hi JB,

Roughly how much fuel would you estimate QF7 to have dumped today? I was listening to them on the departures frequency and they said they needed 45 mins to dump fuel once started. That is 112 tonnes based on the rate you quote. Would that seem right to you?

Thanks
Boof

 

[nutwood]

About 2,500 kgs per minute.

At SG 0.8, that's more than 50 litres every second. Fastest way to lose money with your clothes on, or off?!

 

[jb747]

Roughly how much fuel would you estimate QF7 to have dumped today? I was listening to them on the departures frequency and they said they needed 45 mins to dump fuel once started. That is 112 tonnes based on the rate you quote. Would that seem right to you?

The number I quoted was for an A380. The jumbo rate is slower, and also varies with the number of pumps being used. Maximum rate looks to be about 2,100 kgs/min.

They would only have needed to dump/burn down to max landing weight (a different scenario to the A380). So, if they flew for about 4 hours, that would take care of about 40 tonnes. I don't know which aircraft it was (and so the take off and landing weights, which vary a bit), but I'd guess at about 50 tonnes.

 

[jb747]

Roster time again. The year flies when you take it in two month chunks.

Currently on a London trip, with one more to do from the current roster.

The new one adds a bunch more Londons.

4 Sept QF9 MEL-DXB
7 Sept QF1 DXB-LHR
9 Sept QF10 LHR-DXB
12 Sept QF10 DXB-MEL

18 Sept QF9 MEL-DXB
21 Sept QF1 DXB-LHR
23 Sept QF10 LHR-DXB
26 Sept QF10 DXB-MEL

8 Oct QF9 MEL-DXB
11 Oct QF1 DXB-LHR
13 Oct QF10 LHR-DXB
16 Oct QF10 DXB-MEL

 

[Cynicor]

I just realised that if you're in London, you might have flown my parents in F 2 days ago.
They were on QF 1 I believe.

 

[Boof1]

The number I quoted was for an A380. The jumbo rate is slower, and also varies with the number of pumps being used. Maximum rate looks to be about 2,100 kgs/min.

They would only have needed to dump/burn down to max landing weight (a different scenario to the A380). So, if they flew for about 4 hours, that would take care of about 40 tonnes. I don't know which aircraft it was (and so the take off and landing weights, which vary a bit), but I'd guess at about 50 tonnes.

Thanks JB. You might have had a long day at the wheel, or maybe you read my mind as QF63's scenario with the 747 was going to be my next question. I was actually asking about the A380 fuel quantity dumped for QF7 if you could please possibly take a stab?

Also another thing that popped into my head if you don't mind answering (sorry if it's been asked before) , what are the requirements to dump fuel? As in minimum height to be at? over water only or can it be over land as well?

Thanks

 

[jb747]

I just realised that if you're in London, you might have flown my parents in F 2 days ago.
They were on QF 1 I believe.

I'm Melbourne based, so as a general rule the only sectors that I do on the Sydney flights (1&2) are between Dubai and London. That can change if there are any disruptions, but I haven't operated a scheduled flight out of Sydney since 2014.

Two days ago, I flew the 9 from Melbourne.

 

[jb747]

Thanks JB. You might have had a long day at the wheel, or maybe you read my mind as QF63's scenario with the 747 was going to be my next question. I was actually asking about the A380 fuel quantity dumped for QF7 if you could please possibly take a stab?

It's actually harder to say with the A380, because it's not as restrictive with regard to overweight landings. If you're happy to do the required inspection, and the conditions allow, there's no issue landing at close to max take off weight. Also unlike the 747, the loss of flaps or slats simply doesn't have as negative an effect on the approach speed...even without those aids, it's still an enormous wing.

If they took off at max brakes release weight, with about 220 tonnes of fuel, they'd have the ability to dump about 140 tonnes of that. I don't do the Dallas flight, so the weights are guesses, but probably not too far off. So, with 220 tonnes of fuel, and a 569 TOW, they'd have an operating weight of 349 tonnes. You can dump to around 80 tonnes remaining, which would mean a dump of about 140 tonnes. At 2.5 tonnes/min that's 56 minutes. That would get the weight to about 569-140=429 tonnes. But, we haven't accounted for any burn yet. They were airborne for about 2:40, so if we just call the burn about 13 tonnes hour, that would take care of about 35 tonnes. Add in about another 5 tonnes for the take off and initial climb and you end up at pretty well exactly the max landing weight (391 tonnes).

Overweight landings are recommended to be automatic landings. The loss of the trailing edge flaps means that the autopilot can't be used (for landing), so unless there's an overriding issue, in that case you'd take the time to get below MLW. The approach speed is about 35 knots faster than usual. It could be lower, but the geometry would put the tail too close to the ground. As you saw in the video, the aircraft stops without any issues.

Also another thing that popped into my head if you don't mind answering (sorry if it's been asked before) , what are the requirements to dump fuel? As in minimum height to be at? over water only or can it be over land as well?

In an emergency you can dump it wherever, and from whatever height, you like. Normally though, if dumped above 6000 feet, none will reach the ground.

 

[Strategic Aviation]

Normally though, if dumped above 6000 feet, none will reach the ground.

I'll always be amazed that over 100 tonnes of fuel can be dumped (above a certain altitude) and not a drop touches the ground.

Roughly how much would 140 tonnes of fuel cost the airline?

 

[jb747]

I'll always be amazed that over 100 tonnes of fuel can be dumped (above a certain altitude) and not a drop touches the ground.

You have to remember that it's being dumped into an airflow of somewhere around 500 to 700 kph. It's instantly an aerosol.

Roughly how much would 140 tonnes of fuel cost the airline?

That's the nice thing about being a pilot. I neither know nor care.