Let's face it, regional airlines don't have the best reputation right now and rightly so. However, much of that blame has to do with regional airline management running at the cheapest possible level and major airline management that insist on getting the cheapest possible feed at pretty much any cost.
Totally agree with you on that. Definitely the engine behind the whole downward cycle.
AD
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These views are my own and do not represent the views of United Airlines or the ALPA.
Different Flights/Same Aircraft Type/Different Cruising Speeds
On a recent flight from BOS to SFO, I heard an interesting issue arise regarding cruising speeds as I listened to channel 9. I was on UA 181 (a 757)and about an hour into the flight, UA 15 (also a 757) from JFK to SFO came on our frequency. UA 15 was a little behind us but was obviously cruising at a faster speed at the same altitude and catching up to us. The controller asked each aircraft its mach speed - UA 181 was .78 and UA 15 was .81. The controller asked each aircraft to fly at .79.
The pilot of UA 15 agreed but then asked for a different altitude in order to resume his previous speed and pass us. That was done and since we were both flying nearly the exact same route the rest of the way to SFO, we heard UA 15 get ahead of us and eventually land about 15 minutes before we did.
It seemed curious to me that two different flights both using the same equipment - 757 - for the same airline on the same route would cruise at different speeds. At first I thought that perhaps UA 15 was late and was trying to make up some time, but UA 15 was actually scheduled to arrive after UA 181. I would have thought that company policy regarding such issues as fuel consumption would have dictated the same speed for both aircraft.
About the only thing I could think of was that the passenger load on UA15 was less, since UA 181 was full and since the 757s on the JFK SFO route are configured differently, with F, C, and E+ and therefore carry fewer passengers, even with a full load. If UA 15 was lighter than UA 181, that may have dictated a faster cruising speed.
I'm wondering if anyone with more technical insight than I have would have some insight on this.
On a recent flight from BOS to SFO, I heard an interesting issue arise regarding cruising speeds as I listened to channel 9. I was on UA 181 (a 757)and about an hour into the flight, UA 15 (also a 757) from JFK to SFO came on our frequency. UA 15 was a little behind us but was obviously cruising at a faster speed at the same altitude and catching up to us. The controller asked each aircraft its mach speed - UA 181 was .78 and UA 15 was .81. The controller asked each aircraft to fly at .79.
The pilot of UA 15 agreed but then asked for a different altitude in order to resume his previous speed and pass us. That was done and since we were both flying nearly the exact same route the rest of the way to SFO, we heard UA 15 get ahead of us and eventually land about 15 minutes before we did.
It seemed curious to me that two different flights both using the same equipment - 757 - for the same airline on the same route would cruise at different speeds. At first I thought that perhaps UA 15 was late and was trying to make up some time, but UA 15 was actually scheduled to arrive after UA 181. I would have thought that company policy regarding such issues as fuel consumption would have dictated the same speed for both aircraft.
About the only thing I could think of was that the passenger load on UA15 was less, since UA 181 was full and since the 757s on the JFK SFO route are configured differently, with F, C, and E+ and therefore carry fewer passengers, even with a full load. If UA 15 was lighter than UA 181, that may have dictated a faster cruising speed.
I'm wondering if anyone with more technical insight than I have would have some insight on this.
There are several possibilities.
One is that the aircraft were flying the same Cost Index (CI -- an assumed ratio of time to fuel costs used by the FMC to control the aircraft speed), but at different weights (as you said) -- although for many common ranges of CI and weight, the speed actually decreases as weight decreases, the opposite of what you said.
One is that they were flying a different Cost Index because either their fuel costs were different (remember they had different departure airports) or their time costs were different (even though you found that meeting published schedule couldn't cause the discrepancy, there could be different time-based costs related to where the individual airframes/engines are in their maintenance cycles, where the crews are in their duty cycles, etc.). In fact, I'd guess that the PS flights have a different base cost of time just because they're a different configuration (or because the passengers are considered higher value).
One is that the slower aircraft was limited by a MEL or CDL item, although if he was willing to speed up to .79, that seems unlikely.
One is that UA aren't even flying CI at all, the crews or dispatchers are just picking a Mach number they want to fly out of thin air, and happened to pick very different numbers for those flights.
There are other possibilities, too, and maybe the mods will merge this into the "ask a UA pilot" thread for more visibility.
There is no UX forum; this is the correct place for a UX employee or FF to be, since UX is a sub-brand of UA. And hey, LarryJ is a pilot for some other airline entirely (neither UA nor UX), but he's still welcome. It's always good to have multiple perspectives...
That's fine. Just be aware that all airlines operate differently and an answer from a pilot at a different airline may not reflect UA procedures at all. UX has zero operational coordination with UA. Totally different operating procedures and completely different airlines. My assumption was that the 'pilots' answering questions on this thread are UA pilots..... Glad I know differently now!
In the interest of fair play, I'm a UA 767/757 F/O based in DCA. I have previously flown the 777 and 320 as a F/O and the 727 as a F/E.
On a recent flight from BOS to SFO, I heard an interesting issue arise regarding cruising speeds as I listened to channel 9. I was on UA 181 (a 757)and about an hour into the flight, UA 15 (also a 757) from JFK to SFO came on our frequency. UA 15 was a little behind us but was obviously cruising at a faster speed at the same altitude and catching up to us. The controller asked each aircraft its mach speed - UA 181 was .78 and UA 15 was .81. The controller asked each aircraft to fly at .79.
The pilot of UA 15 agreed but then asked for a different altitude in order to resume his previous speed and pass us. That was done and since we were both flying nearly the exact same route the rest of the way to SFO, we heard UA 15 get ahead of us and eventually land about 15 minutes before we did.
It seemed curious to me that two different flights both using the same equipment - 757 - for the same airline on the same route would cruise at different speeds. At first I thought that perhaps UA 15 was late and was trying to make up some time, but UA 15 was actually scheduled to arrive after UA 181. I would have thought that company policy regarding such issues as fuel consumption would have dictated the same speed for both aircraft.
About the only thing I could think of was that the passenger load on UA15 was less, since UA 181 was full and since the 757s on the JFK SFO route are configured differently, with F, C, and E+ and therefore carry fewer passengers, even with a full load. If UA 15 was lighter than UA 181, that may have dictated a faster cruising speed.
I'm wondering if anyone with more technical insight than I have would have some insight on this.
There are a multitude reasons that could happen. One reason that comes to mind is that the flight going faster might have had some connections that needed to get there as early as possible, for example some passengers that were supposed to be on an earlier flight but ended up on this one and were connecting out of SFO. The other flight could have had an ill passenger onboard, so they were speeding up to get to SFO. I mean, who knows, there are just too many variables to name, or really even worry about.
Speeds are not company directed. The flight crew has discretion on what speeds to fly. Rarely do I end up flying what I have planned unless it's a oceanic flight. ATC continuously changes our speeds in flight. A good example is flying into Chicago or DCA. I know how bad they can get with delays and slowing down enroute. So even though I may be filed at .75, I'll fly faster to Chicago in anticipation of being slowed down as I approach Chicago Center. Doing this helps me avoid a late delay, and hopefully get there a little early for the connections.
But as I said, it's not unsual for flights to be flying different speeds enroute to the same destination. Not unusual at all.
Cheers,
__________________
These views are my own and do not represent the views of United Airlines or the ALPA.
Do you remember whether your aircraft had winglets? The ps aircraft probably did. The winglets may dictate a different optimal cruise altitude/speed.
The winglets do change the Mach number for a specific CI, altitude, weight, and temperature, but the difference is pretty small -- definitely not .03.
(The OP (for this question) said the aircraft were at the same altitude.)
Quote:
Originally Posted by aluminumdriver
Speeds are not company directed. The flight crew has discretion on what speeds to fly. Rarely do I end up flying what I have planned unless it's a oceanic flight.
So now I have a question. Assuming you fly Airbus domestically, is what you have planned constant for all flights, but you vary it yourself (and per ATC), or does your planned speed vary also? Is your planned speed Cost Index, or is it constant Mach?
Last edited by iluv2fly; Jul 5, 09 at 2:45 am.
Reason: merge
So now I have a question. Assuming you fly Airbus domestically, is what you have planned constant for all flights, but you vary it yourself (and per ATC), or does your planned speed vary also? Is your planned speed Cost Index, or is it constant Mach?
Well, both. Our flight plan will be done based on a planned mach number at a certain altitude, but it could change as we climb in altitude during the flight. The cost index will vary our speed as we fly along and get lighter, or climb and descend. ATC doesn't know our cost index, so if our actual speed is different than what we have filed, we let ATC know. Most of the time, we end up flying the speeds ATC would like us at, which is a fast speed. Someone cruising along at .74 mach for cost index is like a speed bump in the road for others flying along. So ATC might ask us to speed up, or take a vector or go to a different altitude. Either one of those affects our planned fuel burn. Not only that, but when flying a cost index, as you start your descent, the cost index can really get you. If I'm cruising along at a cost index giving me .77 mach, that same cost index on descent slows my jet down to .68 mach all of a sudden. If I don't notice, ATC comes on asking what's my speed since I'm backing everyone up. So I'll come out of cost index on descent and use manual speed settings.
It just depends on each flight really.
__________________
These views are my own and do not represent the views of United Airlines or the ALPA.
Well, both. Our flight plan will be done based on a planned mach number at a certain altitude, but it could change as we climb in altitude during the flight. The cost index will vary our speed as we fly along and get lighter, or climb and descend. ATC doesn't know our cost index, so if our actual speed is different than what we have filed, we let ATC know. Most of the time, we end up flying the speeds ATC would like us at, which is a fast speed. Someone cruising along at .74 mach for cost index is like a speed bump in the road for others flying along. So ATC might ask us to speed up, or take a vector or go to a different altitude. Either one of those affects our planned fuel burn. Not only that, but when flying a cost index, as you start your descent, the cost index can really get you. If I'm cruising along at a cost index giving me .77 mach, that same cost index on descent slows my jet down to .68 mach all of a sudden. If I don't notice, ATC comes on asking what's my speed since I'm backing everyone up. So I'll come out of cost index on descent and use manual speed settings.
It just depends on each flight really.
So it sounds like the flight plan comes to you in Mach numbers varying by segment, but you fly CI. Is the CI fixed across the fleet type, or is it also communicated to you on the flight plan, or do you have some other way of picking it?
So it sounds like the flight plan comes to you in Mach numbers varying by segment, but you fly CI. Is the CI fixed across the fleet type, or is it also communicated to you on the flight plan, or do you have some other way of picking it?
It is not fixed, nor is it the same across the fleets. It can vary by specific aircraft in the same fleet. Our flight plans will have listed the lower to higher CI ranges for us to look at.
__________________
These views are my own and do not represent the views of United Airlines or the ALPA.
Programs: My views are not those of United Airlines or UAL Corp
Posts: 60
Quote:
Originally Posted by JerryFF
On a recent flight from BOS to SFO, I heard an interesting issue arise regarding cruising speeds as I listened to channel 9. I was on UA 181 (a 757)and about an hour into the flight, UA 15 (also a 757) from JFK to SFO came on our frequency. UA 15 was a little behind us but was obviously cruising at a faster speed at the same altitude and catching up to us. The controller asked each aircraft its mach speed - UA 181 was .78 and UA 15 was .81. The controller asked each aircraft to fly at .79.
The pilot of UA 15 agreed but then asked for a different altitude in order to resume his previous speed and pass us. That was done and since we were both flying nearly the exact same route the rest of the way to SFO, we heard UA 15 get ahead of us and eventually land about 15 minutes before we did.
It seemed curious to me that two different flights both using the same equipment - 757 - for the same airline on the same route would cruise at different speeds. At first I thought that perhaps UA 15 was late and was trying to make up some time, but UA 15 was actually scheduled to arrive after UA 181. I would have thought that company policy regarding such issues as fuel consumption would have dictated the same speed for both aircraft.
About the only thing I could think of was that the passenger load on UA15 was less, since UA 181 was full and since the 757s on the JFK SFO route are configured differently, with F, C, and E+ and therefore carry fewer passengers, even with a full load. If UA 15 was lighter than UA 181, that may have dictated a faster cruising speed.
I'm wondering if anyone with more technical insight than I have would have some insight on this.
The pilots of UA15 were heading home and had to make their commuter flights!...LOL
Dont know if any of the pilots here can answer this one as they seem to be mostly domestic but I will try...
On a recent flight SFO-PVG, our flight path was pretty much a great circle up to the Aleutians and down over Siberia. We were on a dead reckoning path to Shanghai but I could see we were heading directly for North Korea. This was a few months ago but I remember that overflights had been banned by North Korea by then so I expected a jog in our flight path. As soon as we hit the China border with Russia we took a turn to the southwest on a vector to Beijing. We continued on that vector but when we were out of the way of North Korea I expected us to turn to the SSE towards Shanghai but never did. We kept going straight for Beijing and were now getting WAY out of the way. We had been making pretty good time but as we were getting close to Beijing I began to worry that we may be diverting!
Once we were almost to Beijing we then vectored south towards Nanjing and when we go to about Nanjing we FINALLY turned on a vector to Shanghai. This path I estimated added about an hour to our flight versus a direct route. The last time I flew to Shanghai we did not do this and kept on a beeline to Shanghai pretty much.
Anyone know what may have happened here? Is ATC in China really so limited in its flight paths? Did that occur because of the need to go around North Korean airspace? It seems that in other parts of the path, the changes in direction are only slight as each waypoint is hit. This seemed a bit extreme and I wondered if this was part of the filed flight plan and if we had fuel loaded to accommodate it.
Dont know if any of the pilots here can answer this one as they seem to be mostly domestic but I will try...
On a recent flight SFO-PVG, our flight path was pretty much a great circle up to the Aleutians and down over Siberia. We were on a dead reckoning path to Shanghai but I could see we were heading directly for North Korea. This was a few months ago but I remember that overflights had been banned by North Korea by then so I expected a jog in our flight path. As soon as we hit the China border with Russia we took a turn to the southwest on a vector to Beijing. We continued on that vector but when we were out of the way of North Korea I expected us to turn to the SSE towards Shanghai but never did. We kept going straight for Beijing and were now getting WAY out of the way. We had been making pretty good time but as we were getting close to Beijing I began to worry that we may be diverting!
Once we were almost to Beijing we then vectored south towards Nanjing and when we go to about Nanjing we FINALLY turned on a vector to Shanghai. This path I estimated added about an hour to our flight versus a direct route. The last time I flew to Shanghai we did not do this and kept on a beeline to Shanghai pretty much.
Anyone know what may have happened here? Is ATC in China really so limited in its flight paths? Did that occur because of the need to go around North Korean airspace? It seems that in other parts of the path, the changes in direction are only slight as each waypoint is hit. This seemed a bit extreme and I wondered if this was part of the filed flight plan and if we had fuel loaded to accommodate it.
There are two sets of routes in China. The more dense route structure, used for domestic flights, is controlled by the military, and non-Chinese nationals aren't supposed to know where all the airways and points are; naturally, foreign airlines on international flights cannot use this. There's another route structure, much more sparse, that's published to everyone and can be used by foreign airlines. That said, it's possible that only specific routes of those are allowed to be used by specific operators (or specific airports as origins or destinations).
Also the Russian routes there are pretty restrictive, there are only a few routes allowed for foreign aircraft, again by agreements with the carriers, leading to only certain points where you can cross into Chinese airspace.
Also keep in mind that the great circle is not in general the shortest air distance, once you take winds into account. If you look at flights between the west coast of the US and Europe on flightaware, most times of the year you'll see the eastbound and westbound are not symmetrical, and can be really far apart. Same thing for transcons, like SFO-BOS.
I've seen SFO-HKG to take a similar route to your flight, overflying Beijing after leaving Russian airspace and then heading SSE over China. I've also seen HKG-SFO fly pretty far east of Japan, over the water the whole way. The combination of winds and overflight clearances can take you pretty far from the great circle.
So... In my stalking of White Sox flights, I noticed they sometimes go to unusual airports which United does not offer service. So my question is, does the flight crew do anything special before landing at an airport they never have been to before? Or are these airports small enough that it doesn't matter?
