[arijitkanrar]

Originally Posted by Sutripta

How are headwinds taken into account for limit of endurance flights?

Regards
Sutripta.

The pilots can request for a change of altitude or track to avoid headwinds.
If that cannot be done or they dont find a way to avoid headwinds, they usually have extra fuel for contingencies. This ensures that even with a little bit of headwind they still can reach their destination.
However if the headwinds are so strong that their range will be significantly reduced, then they can always divert to an alternate airport, land, refuel and take off again.

[Jeroen]

Originally Posted by Sutripta

How are headwinds taken into account for limit of endurance flights?

.

Every commercial jet deals with head and tailwinds and adjust its flight plan and fuel load accordingly. Part of the flight planning is to look at winds aloft and find the most optimum route and altitude. So the initial flight planning is done on whatever is known about the winds aloft.

The FMC, Flight Management Computer, will also handle expected winds aloft for various altitudes.

So the pilots have a continuously update from the FMC about ETA and fuel remaining at destination. The FMC takes into consideration the plane ascending to higher altitudes during the flight. Higher altitudes means better fuel efficiency. But can be offset by head wind. So it needs careful planning and monitoring during the flight.

I just flew back from Delhi to Amsterdam. When we took off the captain told us flight time would be 8 hours and two minutes. And we landed exactly 8 hours and two minutes later. That is quite accurate and not unusual at all!

So his flight plan had really good wind aloft forecast!

Part of the problem for this flight is likely that they might follow routes with very little information on winds aloft.

ETA and fuel remaining at destination relies heavily on the accuracy of the winds aloft.

It would be interesting to hear from some real dispatcher how they plan and account for tail and or head wind.

I used to factor in whatever wind was forecasted and just checked I still had appropriate alternatives. A headwind would always factored in completely, it can severely cut down on your range. So either you bring more fuel, or you might have to plan for an extra fuel stop.

During the flight you would continuously monitor your planned fuel versus actual fuel. You want to know if you fall behind the curve so to speak and you need to figure out when it gets to the situation where you need to divert from your original flight plan.

Jeroen

[Sutripta]

Originally Posted by Jeroen

It would be interesting to hear from some real dispatcher how they plan and account for tail and or head wind.

Indeed. Indigo messed up. DGCA had to step in.

Regards
Sutripta

[.sushilkumar]

Talking of head & tail winds, below came to my mind as how they can make help you break world record & ensure you reach early.

Boeing 787 flight reaches 801 mph as a furious jet stream packs record-breaking speeds

801 miles an hour. Beat that

[V.Narayan]

Qantas is known for doing its homework well and in this case they have taken the test run to not only gather incremental data but more importantly garner a whole lot of well orchestrated and happy publicity. All airlines that plan, what for that era is, a long flight first conduct two or more trial runs to check head winds and navigation along the route, measure crew fatigue and most importantly take a scientific measure of fuel consumption and reserves.

There are at least 7 or 8 regular scheduled flights in the 17-hour and above category and at least two in the 18-hour segment. 19-hours is demanding, and I am not taking anything away from the crew and the flight planners, but not earth shattering. But it would still have called for significant planning and careful management of fuel burn. Also across the wide expanse of the Pacific there are far fewer airports that can serve as an emergency back-up.

Measures on crew brain wave patterns & wakefulness limits will always help. We do not know enough about this yet. The real passenger runs will need a different aircraft.

To the questions on allowing for unexpected headwinds it is typical to allow for at least 5% extra of the worst case TRIP fuel consumption for unexpected headwinds or weather conditions or 20 minutes whichever is greater. This is over and above DIVERSION fuel for diversion to the nearest practical airstrip and CONTINGENCY fuel equal to at least 30 minutes of hovering at 1500 feet. Further the Captain will determine based on his experience how much additional fuel he needs to carry as a safety margin above all these. Plus there are laws and policies on the minimum that must be planned to be there in tanks on landing as a further safety buffer. The figures above are for long flights of a business jet that I am more familiar with. Airline figures could vary but it gives the reader a sense of the direction.

[HKap]

Originally Posted by Shreyans_Jain

Help me understand.

They are pushing the limits of endurance in terms of fuel and range, fair enough. But I don’t get the fuss being made about the performance and ‘condition’ of pilots and passengers over a 19 hour flight. I mean, there are plenty of long distancers here on this forum who drive 20+ hours continuously with no mul fuel and bio breaks, yours truly included. Personally speaking, I drive all by myself and the family also doesn’t complain after so many hours in the vehicle. So many train journeys are over 2 and 3 nights. So, what is the big deal about something similar happening in civil aviation despite having redundancies like multiple pilots and tools like autopilot?

Pilots always have to be in a condition with optimum awareness and fatigue whether mental or physical is a massive problem when it comes to dealing with emergencies. This is the exact reason why there are two sets of pilots on ultra long haul flights. Maybe they are planning to extend the flying hours for pilots through this research so they can have only 2 sets of pilots instead of 3 that may be required as per the current regulations..... My guess.

Also, driving a car and flying are not comparable and the alertness levels required for both are very different. A piece of unsolicited advice, please do not drive for over 12 hours in a single day. I am 100% sure that the human mind will not be as alert after 12 hours of continuous driving as it was in the first 7-8 hours. I've driven long distances myself and looking back, I think it was just pure adrenaline that got me through those drives. Was I maintaining a consistent level of mental alertness? No way. There were times where I almost dozed off at the wheel. All the passengers in the car were asleep. This was a 13 hours road trip 12-14 hours after flying from Mumbai to SFO.

[dragracer567]

Originally Posted by Stratos

Great feat by Qantas and the Dreamliner, however, I am not so sure about the research related to this flight.

19-20 hours is a long flight for the operating crew. However, unless Qantas plans to only have business class seats on this flight, the passenger research on this particular flight for me is not relevant.

If you really want to study effects of ultra-long haul flights on passengers, it has to be focused more on the ones sitting in economy class.

For me, flight SQ21/22 (Singapore Airlines), which already operates for more than 18 hours of flight duration (Singapore - Newark - Singapore) takes the cake. At least it is carrying almost 180 people and some cargo in Business and Premium Economy configuration.

I will wait and watch how Project Sunrise actually becomes a reality as from where I see it, the 787 Dreamliner lacks the range to do so with more than "handful" passengers and "some" cargo.

That's because the ultra-long haul flights (18 hours+) such as the Singapore-Newark-Singapore operated by Singapore Airlines and the Perth-London-Perth operated by Qantas only has business class and premium economy class. I'm assuming that the same will the case for the upcoming Sydney-JFK-Sydney flights.

Budget conscious travelers who will fly in economy probably won't mind a stopover - either as a transit or an airstop like the Sydney-JFK via Los Angeles flight.

[Jeroen]

Originally Posted by Shreyans_Jain

Help me understand.

They are pushing the limits of endurance in terms of fuel and range, fair enough. But I don’t get the fuss being made about the performance and ‘condition’ of pilots and passengers over a 19 hour flight. I mean, there are plenty of long distancers here on this forum who drive 20+ hours continuously with no mul fuel and bio breaks, yours truly included. Personally speaking, I drive all by myself and the family also doesn’t complain after so many hours in the vehicle. So many train journeys are over 2 and 3 nights. So, what is the big deal about something similar happening in civil aviation despite having redundancies like multiple pilots and tools like autopilot?

Well, to be brutally frank, driving 20+ hours continuously is simply irresponsible.
By and large in many western countries, the norm for driving is 2 hours drive, 15 minutes rest. Professional drivers (truck / busses) are limited to legal driving of no more than 8-10 hours a day, with 2 hours/15 minute stops. Many road fatalities across the world are due to driver fatigue.

Driver fatigue is tricky, it creeps up on you and you hardly notice it yourself. You will feel reasonable fine after those 20+ hours driving. But the truth is that within a few hours your alertness is dropping considerably and your responses are slowing down.

You only have to look for it on the Internet: Endless research showing what effects prolonged driving has on your level of alertness. That is the exact reason why in many countries driving times for people such as truck-, bus drivers and pilots is heavily regulated.


Please take care, if not for yourself, for your family. Yes, it is nice to get there quickly, but it is not worth an accident.

All the best.

Jeroen

[Sunil2307]

Have done a couple of New Delhi - New York direct flights, and was exhausted and restless at the end of those. I am sure the crankiness will increase on a 19-hour flight. At the end of the flight there will be a bunch of irate passengers and flight crew for sure.

[A350XWB]

Originally Posted by .sushilkumar

No Aeroplane in service currently have the range to do this on a one go & thats exactly the challenge qantas have thrown to Airbus & Boeing.

Technically, an Airbus A350XWB-900ULR can do this route. It has a design range of up to 9700nm, which is sufficient for this route, which has an 8646nm Great Circle distance. The distance traveled during the test flight was 8747nm, which gives it a reserve of ~1000nm, which is usually sufficient as contingency reserve. Technically, it can even do the proposed LHR-SYD, which is 9180nm.
But everything depends on the payload requirements from the carrier. Singapore airlines does the SIN-EWR-SIN route with 161 seats (67 Business and 94 Premium economy) and flies ~8640nm (~16000km). If the payload requirements are much higher for QANTAS, the A350XWB-900ULR cannot do this; else, it is very much possible.

[MMinor]

I dont think I will be in minority when I say this but I personally prefer a two ten hour flights split by a short lay over than a straight 20 hour flight. I travel to the US west coast at least once a year every year and my optimum route turned out to be the one via London. After trying out Emirates, Cathay Pacific among others I can confidently say its British Airways for me all the way. Top reason, because they use a really old model flight from Bangalore that has better width and pitch than the ones on other carriers . Second reason my destination is served, the second 10 hours, via an A380.

Apart from the above reasons, I just couldn't stand to sit post 13 hours when I had to fly 16 hours on the second leg, can't imagine doing that for another 3 hours after the first 16 cooped up in a germ infested cauldron that the air inside the aircraft is.

[Stratos]

Originally Posted by dragracer567

That's because the ultra-long.......like the Sydney-JFK via Los Angeles flight.

Thus, I see no point in measuring mental impact of such a long flight on 35 passengers who were in "business class". If they had put some passengers in economy / premium economy, it would be a much stronger case of research.

[Malyaj]

Originally Posted by Shreyans_Jain

Help me understand.

They are pushing the limits of endurance in terms of fuel and range, fair enough. But I don’t get the fuss being made about the performance and ‘condition’ of pilots and passengers over a 19 hour flight. I mean, there are plenty of long distancers here on this forum who drive 20+ hours continuously with no mul fuel and bio breaks, yours truly included. Personally speaking, I drive all by myself and the family also doesn’t complain after so many hours in the vehicle. So many train journeys are over 2 and 3 nights. So, what is the big deal about something similar happening in civil aviation despite having redundancies like multiple pilots and tools like autopilot?

Even from passengers' point of view, it is not the same thing. On the highway, a passenger always has the option (whether he/she chooses to exercise it or not) to have the vehicle pulled over and take rest, use the restroom and generally stretch legs for as long as one wants.

The absence of this choice on a flight can have a psychological impact and add to discomfort. There is also the fact that one could be sitting next to strangers and may feel restricted in movement and privacy. Passengers who are extremely conscious about not disturbing others will visit the restroom less often and get up less often to stretch their legs. These are real scenarios and just not comparable to spending similar time on the road, especially in your private vehicle.

[Jeroen]

Originally Posted by A350XWB

Technically, an Airbus A350XWB-900ULR can do this route. It has a design range of up to 9700nm, which is sufficient for this route, which has an 8646nm Great Circle distance. The distance traveled during the test flight was 8747nm, which gives it a reserve of ~1000nm, which is usually sufficient as contingency reserve. Technically, it can even do the proposed LHR-SYD, which is 9180nm.
But everything depends on the payload requirements from the carrier. Singapore airlines does the SIN-EWR-SIN route with 161 seats (67 Business and 94 Premium economy) and flies ~8640nm (~16000km). If the payload requirements are much higher for QANTAS, the A350XWB-900ULR cannot do this; else, it is very much possible.

Planes rarely travel via Great Circles. Flight plans are at best an approximation. Flight plans are built up of multiple “straight” section, way point to way point, just sections of essentially rhumb lines. I do not think there are Flight Management System out there that can fly a great circle? Your typical flight plan consists of a set of so called Hi altitude routes, which are not great circles.

Whether it is a Hi or Lo altitude route, neither is a great circle. The various ocean tracking system do the same. Not a great circle either, again just sections of essentially rhumb lines.

Flight planning and thus range is not about geographical distance perse. Although the aircraft manufacturer like to mention the range, it is not a number that is used in real flight planning.

Flight planning is about fuel burn. How much fuel are you burning per hour and how much distance are you covering at that burn rate. Which depends on altitude, winds, actual weight (which comes down as you burn fuel) etc.

The rest is about the route and all sorts of restrictions and other consideration. It is always about having to take into account multiple variants that impact your route and your route time and thus fuel. 19 hours against an average 100 mph jet stream will get you a considerable shorter (geographical) distance than 19 hours with the same jetstream on your tail! Throw in ETOPS, suitable alternates and escape route over high mountainous terrains, restricted airspace (e.g.war zones, holds, minimum required fuel at destination airport, taxi time, expected taxi delays, expected weather at destination, legal and other (company specific) operational considerations etc etc.

That is all on top of payload requirement obviously.

Flight planning is about fuel burn. The correlation between fuel burn, weight, altitude are very specific and known for each plane/engine. So it is about how much fuel are you burning per hour and how much distance are you covering. Which depends on altitude, winds, actual weight (which comes down as you burn fuel). The rest is about the route and all sorts of restrictions see above. The geographical shortest route (great circle, rhumb line or other) might not necessarily be the shortest flight time either. Jet streams are pretty consistent in strength and duration for a short period and regional area. On long haul flights you rarely encounter the same jet stream strength/direction for the duration of the flight. So it might be advantageous to plan for what would be a longer (geoprahical) route to optimise for jet stream effects.

Jeroen

[swami69]

is a 3 hour difference between the current long hauls and this one making so much of news ? or is it that 3 hour really the breaking point ?

Because, as most of us know, there are several flights from Dubai/Emirates to the West Coast of the USA which is already 15.5 to 16 hours. I have myself flown in Economy Class and Business class to SFO, LAX and SEA from DXB few times.

Yes, the procedure of working on the Destination time zones are practiced already by many including me and i do not find that much of a problem while landing on both sides and get used very quickly. May be it is just me..

As said, may be those additional 3 hours is making Qantas doing all these studies and test flights - I respect that part of the Science.

Swami