Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie
The great big "ask an airline pilot" thread!
Options
Comments
-
Flying higher does use less fuel, but this only useful to a point, there is an altitude called OPTIMUM altitude, this is where you get the maximum "Nautical Air Miles" for a given amount of fuel. So in an old fashioned aircraft, one would basically aim for this altitude, as you get lighter this altitude gets higher, so you climb with it, it might also help to slow down, but if you slow down it will take longer to cover the distance, so you have to assess your total fuel to cover that distance at the slower speed.
To take this a step further you get whats called ECON cruise, this is based on a value called "Cost Index" that is entered in the FMS. Some airlines will have a specific CI value for each route, or they may assess the need for an on time arrival to be more important than fuel costs, this is due to missed connections etc.
With Cost Index you ignore the costs that are not controlled by the hour, like paying for the aircraft lease/loan, insurance, airline operations administration costs, these have to be paid at the end of the month regardless of how much you fly.
So you compare the hourly costs of the aircraft versus fuel, lets say its $100 = $100. But on a certain route fuel is expensive so it becomes $100 = $200, ouch i want to cut down that fuel cost so i fly slower, this will increase my hourly costs but reduce my fuel cost, so we end up with $140 = $150, in doing this we have saved $10 for that hour. It doesn't sound like a lot but our A320 fleet flies something like 10,000 hours a month, so over a year thats over $1,000,000 saving in fuel costs. Now considering that the costs involved are a lot higher than my little formula, you can see how these savings are worthwhile.
As for Garbage IN/OUT, well ECON has to use WINDS to make an accurate calculation of time, if you dont enter real winds for the whole route, its not going to make a total accurate calculation, OK it will reassess each time it gets a wind, but from your planning stage it was wrong.
Then the fixed costs, lets say an airline decides to include the cost of its operational staff in the formula, it would increase the fixed costs so it wouldn't push you to save as much fuel. This is why i find it funny when people ask on forums, "hey we are new to CI, what do you guys use"? It doesn't work that way, if one is unaware of how the formula works, then the easiest thing to do is ask Boeing/Airbus for a standard CI value that equates to your desired Cruise Speed, ie constant mach or LRC.
Most airlines have an operational engineering department, who would calculate these values and submit them to the flight planning system as well as giving them to the crew.
As to additional maintenance for flying high, we dont record the altitude that we fly at, so maintenance have no way of assessing if we flew high or low. Plus with the logic of the pressurisation system, the cabin is pressurised to a pressure regardless of the altitude, for example today we will fly at FL210 with the cabin altitude at Sea Level and the pressurisation setting will be at about 7.5, on the way back it will most likely remain at 7.5, but if we climb to FL320, the cabin altitude will increase to 3000 feet. Maybe some of the technicians on here might correct me on this, but AFAIK we dont have additional maintenance checks due to higher cruising levels.
And now i have to go do an annual line check
:(
smurfjed0 -
-
-
-
-
Advertisement
-
-
-
-
-
-
Advertisement
-
-
-
-
Are you really 16 years old? You ask some extremely interesting questions
I'm interested to know a little more about the flight planning systems. Is this just a standalone solution or is it integrated with the aircraft computer? And, is it just for planning? What I mean is, are any actual values recorded and compared against the plan (so we can see how wrong we got wind speed etc.)?
Finally, do all airlines use the same flight planning systems, or are there a number of providers?
I'm going to guess here that Lockheed (Aircraft manufacturer, builder of L1011 Tristar) were one of the first developers of a flight planning system, they later became Lockheed Memrykord and then Jeppesen, who are now one of the bigger providers of flight planning software. The older versions were standalone and were pretty hit and miss due to the lack of computing power and available data.
Now a lot of the systems are integrated, so the weight control adds the payload and exact fuel to the Computerised flight plan prior to the flight, this is combined with fuel costs for departure and destination and aircraft costs to provide a speed schedule based on cost efficiency. The captain and dispatcher agree on the flight fuel etc. Once onboard and everything loaded, a final flight plan is uploaded directly to the FMS. After the flight, the original fuel plan and the actual fuel plan are compared to assess the differences, this in turn can lead to fuel or drag biases getting added to that specific aircraft tail number as part of a larger performance monitoring program.
Some airlines have in-house flight planning systems, other providers are Lufthansa LIDO, Sabre with their crap system, Sabre with their recently purchased FWZ system and some company in Sweden who's name i can never remember.
smurfjed0 -
-
-
-
-
-
-
Advertisement
-
-
-
-
-
-
-
I hate jetlag..... 5am in the morning and I'm wide awake, pick up in 4 hours
I asked this question to a friend who flies the A320, we have over 40 of them, he replied that he didn't usually know which aircraft that he was on, and that the only difference for him was remembering that some had more fuel than others. But as they are all set up the same, and with an operating policy that just about has the autopilot on 99% of the time, he really doesn't see a difference between them.
As for me, i have 6 aircraft to choose from, and we hand fly a lot more, the joys of not having active flight dating monitoring systems. And yes we know which aircraft flies nicer, which one is slightly out of rigging, which one always a "X" fault on startup etc, and which one has the best interior for the route. For example, the aircraft coming up to the UK today has the largest number of seats, it has 2 long sofa's that have plenty of room underneath them for storing shopping, so in about 30 minutes I'm heading to Tesco to stock up. We have another that has a double bed in the aft cabin, just perfect for long deadhead flights, and another with a shower. So depending on where we are going, the selection of aircraft can make a nice difference to us.
smurfjed0 -
On the point of knowing what to expect from individual aircraft, a friend who used to be on the 146 knew exactly how much extra rudder trim they would need above and beyond what would be required anyway, once they saw the reg. Apparently some needed quite the extra touch
0 -
-
Advertisement
-
Are you really 16 years old? You ask some extremely interesting questions
Sadly not. You can pretty much double that
I'm just a bit of a nerd with an interest in numbers and aviation!
To continue the theme, how good would you say commercial airlines are at performance monitoring?
Is it something in your opinion saves airlines money or, in reality, do the practicalities of running a large (or any size) airline mean that for all the monitoring and planning in the world, unexpected stuff happens and tail numbers are swapped last minute making monitoring and planning of routes by tail number meaningless?
Also, are those grapes seedless?0
Advertisement