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Question About Routing (air And Ground) SEA-DEN  
User currently offlinercair1 From United States of America, joined Oct 2009, 1308 posts, RR: 52
Posted (1 year 9 months 6 days 18 hours ago) and read 2906 times:
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Last night I flew (on) a UA 757 from SEA to DEN and 3 (4?) 'interesting' things happened. Hoping somebody may be able to shed some light. I considered asking the crew after landing - but we unloaded from L2 and going upstream to the cockpit would have been a challenge.

Boarding:
First - it started in SEA at the gate. Inbound (same aircraft DEN-SEA) was delayed slightly so we were scheduled out 15 late. At the gate the agent stated the inbound crew was hoping for a quick turn as they wanted to get back home too (Denver based) - so to expedite loading - they invited people with larger roll-a-boards to gate check. Particularly those in later boarding groups. This was before the a/c touched down I think - or soon after. The fight was not full by the way.
Loading was quick (late Fri evening - everybody wanted to go home).

Taxi/Takeoff:
Then on taxi out (N-gates to 16L) we honked right along - okay - trying to make up time.

At the end of 16L we waited for a moment and the PM said (Tower - United xxx is ready to go). They told us to hold for inbound traffic - okay. Just as the inbound when by - the engines spooled up a bit (on brakes) - so that as soon as were told "line up and wait" we jumped right to it.

Then - on the runway - we did what seems like a high performance takeoff. When we got clearance to takeoff - the engines spooled up - on brakes. When spooled up fully - brakes released and off to the races!

Great fun in a 757 - had a great takeoff and quick climb... However, it was 'wobbly - lots of small pitch changes - like hand flying, but not hand flying smoothly. (not bad - just not as smooth as you might think).

-----
Enroute:
About an hour in - center called and said - "Clear direct Rock Springs." We came back with "We'd like to stay on plan as filed." Center said - "Okay - as filed."

On approach to Denver - center called and gave us a clearance - I think it was TOMPSN 5, but maybe it was RAMMS 5, I can't remember. But again - we came back with "We'd like to stay on plan as filed." Denver said - "You can do that, I'll have to take you way out east." At that point - we said - okay - we'll take the .... and we took the route requested.

----
Denver landing/taxi (all aircraft, not just us)
Landing was "solid" but fine - but then we taxied in a very weird way -
We landed 16L - headed to gate B32 I think - gate was on south side of B just west of center.
The 'normal' Route from 16L to B32 would have been South on G(olf) or F(oxtrot) to B(ravo) S(ierra) to the gate.

Instead - we told us taxi Z(ulu) and when abeam the united hanger call. We did and then taxied south on L(ima) to B(ravo) S(ierra) to the gate.

As I was listening - I heard all aircraft being directed Zulu to Lima to the gate.

I was unable to see anything unusual on the west side of the airport - I was window seat on the right - so I had a good view.

BTW - we did land pretty much on time - so we made up nearly 25 minutes. We would have been early if we had not had to taxi around the dang airport in DEN.

----
So -
- Why were we so 'pushed' to get out quick - is there an end of the month "award" for on time?
- Why did we do the max perf takeoff (spool up on brakes - then release and go). We were not heavy - and 16L at SEA is LONG.
- Why the hand flying climb(?)
- Why the concern to stay on plan as filed.
- Why was Denver taxi routing so weird.

Was it possible there was an issue with either the Autopilot or FMC so changing routes were a pain? Maybe they had to hand fly.

I have no clue on the DEN taxi routing


rcair1
12 replies: All unread, jump to last
 
User currently offlineSKC From United States of America, joined Oct 2012, 93 posts, RR: 0
Reply 1, posted (1 year 9 months 6 days 14 hours ago) and read 2845 times:

- If you're running late inbound, why not rush to get out closer to on time. Performance stats count, so getting closer to on time on the arrival end could help stats.
- Maybe that is a procedure UA has that's done periodically.
- Maybe there were some winds that made it squirrelly, an autopilot wasn't working properly, or maybe he just wanted to hand fly it a bit.
- Route may have been a turbulence or mountain wave avoidance route or maybe they needed to stay on a non RNAV route due to deferred nav equipment.
- taxiways could have been NOTAM'd closed


User currently offlinercair1 From United States of America, joined Oct 2009, 1308 posts, RR: 52
Reply 2, posted (1 year 9 months 6 days 2 hours ago) and read 2755 times:
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Yes - unfortunately - you just restated my questions as hypotheses.

Quoting SKC (Reply 1):
- If you're running late inbound, why not rush to get out closer to on time. Performance stats count, so getting closer to on time on the arrival end could help stats.
- Maybe that is a procedure UA has that's done periodically.

As a DEN based flyer - I fly/have flown UA a lot (used to be 1K up till 2 years ago). I've never seen them do this - not complaining, just a bit of a surprise. I thought 'on time' spec's were based on departure, not arrival. We departed 30min late, arrived on time.

It seemed like this crew/gate was pushing really hard - don't get me wrong - I really liked it - people responded and we got home earlier - all good - but it was unusual.

It was really refreshing to see a gate crew being proactive to make up time, I give them high complements (wish I had a name/employee numbers to submit awards). It was just unusual. If that is the 'new' united - then kudos!. Also - I don't think this was ex -CO crew. The gate and flight is one I've used many times on the DEN/SEA route and it was always UA (before the merger).

Quoting SKC (Reply 1):
- Maybe there were some winds that made it squirrelly, an autopilot wasn't working properly, or maybe he just wanted to hand fly it a bit.
- Route may have been a turbulence or mountain wave avoidance route or maybe they needed to stay on a non RNAV route due to deferred nav equipment.

Rides were pretty good at in all sectors/altitudes - listened to channel 9 the entire trip - very little hunting for rides. We did not change altitude once (35K) - and no need to. I remembers very few aircraft wanting to change. The ones I do recall seemed to be interested in routing, not ride (can we go to 45K and then direct xxxx?)

Indeed, it may be some equipment was deferred - I was just hoping to hear from somebody who could tell me what kind of equipment deferral would push you to not wanting to go off flightplan. Bad button on a keypad?

It may be that the flight plan was very direct and they wanted to stay on it to minimize the time. This was a DEN based crew and I suspect they had DEN/SEA/DEN down pat.

Quoting SKC (Reply 1):
- taxiways could have been NOTAM'd closed

I looked for NOTAM's once we landed - best I could on my smartphone. Could see nothing about DEN taxiways except a note or two on lights in one or two isolated places. Nothing about the entire west side of the airport being closed.



rcair1
User currently offlineYYZatcboy From Canada, joined Apr 2005, 1070 posts, RR: 0
Reply 3, posted (1 year 9 months 6 days ago) and read 2730 times:
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Well as to the optimum routing, If the flight plan was a Random Route and altitude profile, the dispatcher did a lot of work to plan the best route for winds. ATC does not know or care much about winds, so when they offer directs, it can put you smack bang into a headwind. For example sometimes from LAS-YYC my best routing is departing to the west out of LAS and going up over RNO before cutting up to YXC and into YYC. Normal route departs to the east and up over SLC. At night when Area 51 is not active, ATC often offers directs to YQL and that puts the planes right into a headwind. If the pilots don't ask the dispatcher to run them new numbers they won't know until they realize that they are over burning and over flight planned time. Usually by then it's too late to get them out of the wind. That's one reason why the crew might have wanted to stick to the planned routing.


DHC1/3/4 MD11/88 L1011 A319/20/21/30 B727 735/6/7/8/9 762/3 E175/90 CRJ/700/705 CC150. J/S DH8D 736/7/8
User currently offlineMSJYOP28Apilot From United States of America, joined Jul 2009, 219 posts, RR: 1
Reply 4, posted (1 year 9 months 5 days 17 hours ago) and read 2686 times:

There are many reasons for expedited boarding. There may have been some connecting passengers, the crew may have had some rest and duty time issues, and also the crew may have simply wanted to get home and not sit waiting around in SEA. Only way to know would be to ask the crew.

I would also be very careful making assumptions on whether the crew did full power takeoffs, or hand flew vs autopilot. There isnt that big of a difference between the autopilot and hand flown so I seriously doubt that hand flying caused the wobbly takeoff. Chances are greater that there was a crosswind that was pushing the aircraft away from the route headings and some crabbing was need to correct for the wind. Pitch changes indicate the crew trying to maintain or increase/decrease the airspeed or climb rate. On a SID or vectored departure, both are likely and can change with other traffic in the area.

Enroute, there are plenty of reasons to stay as filed. SEA-DEN covers a lot of mountains. The regulations require that aircraft must clear the terrain by a comfortable margin if one engine were to fail. The max weight of the aircraft crossing these areas must be matched up to possible icing conditions. If icing is possible enroute, the dispatcher may have planned for driftdown clearance because terrain clearance method in icing conditions takes a severe weight hit. In the driftdown method the aircraft would go to pre-determined alternates that would safely allow the aircraft to clear the terrain. Either way, accepting a direct clearance over mountains means being certain that you have the numbers to go off the filed plan. The terrain clearance and driftdown numbers in the dispatch release/flight plan only cover the being filed. Crews have charts to look up if they decide to go off route.

Also, the crew could have input direct Rock Springs in the FMS and compared with staying on filed route and found the winds and enroute time more favorable to stay as filed.

If both of the FMS or GPS wasnt working, the crew could still accept direct Rock Springs if they had a way to maintain navigation through VORs.

On arrival, the only way to know why which route is being used is to talk to ground control and ramp control. There are a large number of variables that they consider.


User currently offlinercair1 From United States of America, joined Oct 2009, 1308 posts, RR: 52
Reply 5, posted (1 year 9 months 5 days 12 hours ago) and read 2653 times:
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Quoting MSJYOP28Apilot (Reply 4):
crew may have had some rest and duty time issues,

This seems like the most likely to me... but as you said - really would have had to ask and that was not practical (plus, if they really did just want to get home, last thing they needed was some passenger asking inane questions.

Quoting MSJYOP28Apilot (Reply 4):
I would also be very careful making assumptions on whether the crew did full power takeoffs, or hand flew vs autopilot. There isnt that big of a difference between the autopilot and hand flown so I seriously doubt that hand flying caused the wobbly takeoff.

It actually wasn't the takeoff - it was the second stage climb - 4K to 15K where I noticed it. It could have been weather I suppose - wind shifts as we climbed would have had the impact I felt.

I'm not sure it was max power - but it clearly was different in that we pulled onto the runway - came to full stop (line up and wait), the powered up to what appeared to be close to the take off power setting - on the brakes. Then released brakes when power was up. It was not a long roll - the aircraft did not feel heavy and 16L is quite long.

Quoting MSJYOP28Apilot (Reply 4):
Enroute, there are plenty of reasons to stay as filed. SEA-DEN covers a lot of mountains. The regulations require that aircraft must clear the terrain by a comfortable margin if one engine were to fail.

That makes some sense to this mt pilot. However, the weather was clear and clean- no icing predicted or likely. As I said I don't think we were heavy. The response about direct Rock Springs was 'instant' - so they did not have time to look anything up (unless they had already). Same with the arrival routing - the response was an "automatic" we'd like to stay on plan as filed. I think there was just some reason they did not want to have to dink with the FMC.

Clearly they could do it - they flew the requested approach without hesitation once it became clear the filed plan would result in a long swing east.

As for taxi in Denver - clearly there was something going on over in the west side. Even a/c that were on the s/w end of A had to taxi Zulu-Lima-Alpha-Sierra and all the way down the terminal. This was adding probably 10 minutes to nearly every taxi.

I'll chalk it up to a late Friday night party at the deicing pads.... Maybe 3 dog night was playing.... (wasn't quite cold enough to be a 3 dog night).

Thanks for your insights MSJ....



rcair1
User currently offlineRoseflyer From United States of America, joined Feb 2004, 9511 posts, RR: 52
Reply 6, posted (1 year 9 months 5 days 11 hours ago) and read 2639 times:

Quoting rcair1 (Reply 2):

As a DEN based flyer - I fly/have flown UA a lot (used to be 1K up till 2 years ago). I've never seen them do this - not complaining, just a bit of a surprise. I thought 'on time' spec's were based on departure, not arrival. We departed 30min late, arrived on time.

On time specs that are most commonly reported between airlines is Arrival within 14 minutes of scheduled arrival. The airline internally monitors delays at 0-15 minutes, 15-120 minutes, 120+ minutes, and cancellations for ways to keep the metrics up. However none of that gets tracked outside the airline.

(ignoring ATC, weather or due to inbound airplane) 0-15 minute delays are typically caused by airport operations, boarding, cabin cleaning, catering, ramp operations etc. 15-120 minute delays are usually maintenance related for minor problems. Interior problems, cargo problems, equipment that can be deferred, things that can be reset easily, tires, etc. Delays over 120 minutes are typically caused by systems components like flight controls, fuel, engines, etc.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineandyinpit From United States of America, joined Sep 2007, 320 posts, RR: 0
Reply 7, posted (1 year 9 months 5 days 5 hours ago) and read 2604 times:

The tower positions could have been combined to the East side, therefore all taxi would have to be done from that side. DEN tower is so big, you either have to work it split, or everything goes in and out of the combined side.

User currently offlineN353SK From United States of America, joined Jun 2006, 820 posts, RR: 0
Reply 8, posted (1 year 9 months 5 days 2 hours ago) and read 2589 times:

The most common reason to stay on your planned route is weight. If you're forecasting to be at or above you max landing weight at arrival, you're not going to take a shortcut and reduce your burn.

User currently offlineRoseflyer From United States of America, joined Feb 2004, 9511 posts, RR: 52
Reply 9, posted (1 year 9 months 4 days 23 hours ago) and read 2561 times:

Quoting N353SK (Reply 8):
The most common reason to stay on your planned route is weight. If you're forecasting to be at or above you max landing weight at arrival, you're not going to take a shortcut and reduce your burn.

I'd expect that on a regional jet, but is that common on a 757? I was under the impression that the 757 had such a wide payload curve that it doesn't run problems exceeding max landing weight. I'm curious.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineFabo From Slovakia, joined Aug 2005, 1219 posts, RR: 1
Reply 10, posted (1 year 9 months 4 days 19 hours ago) and read 2522 times:

Quoting Roseflyer (Reply 9):
I'd expect that on a regional jet, but is that common on a 757? I was under the impression that the 757 had such a wide payload curve that it doesn't run problems exceeding max landing weight. I'm curious.

Might have been tankering cheaper fuel from SEA...

As for high-power takeoff, I believe airplanes have to do full power takeoff every so often - maybe it was just time to do one, and crew added a bit of fun factor by standing on brakes - or looked for specific indications before releasing and concentrating on the roll itself.



The light at the end of tunnel turn out to be a lighted sing saying NO EXIT
User currently offlineSKC From United States of America, joined Oct 2012, 93 posts, RR: 0
Reply 11, posted (1 year 9 months 2 days 23 hours ago) and read 2386 times:

Quoting rcair1 (Reply 2):
Indeed, it may be some equipment was deferred - I was just hoping to hear from somebody who could tell me what kind of equipment deferral would push you to not wanting to go off flightplan. Bad button on a keypad?

I don't have a 757 MEL in front of me, but at least on a 737, you can defer your FMCS and that would prohibit you from operating along an RNAV route.

It's common around here for the dispatcher to see what ATC is giving other aircraft ahead and pass that info on so the pilots will know what to expect. So, it's very possible that the crew already was expecting ATC to offer DCT OCS, so it didn't take them any time to mull it over, they just knew they couldn't/wouldn't (for whatever reason).

I don't recall many place that the 757 has difficulty with driftdown, unless it was loaded with fuel and freight. But, without someone IN the cockpit, it's nearly impossible to know exactly what transpired or why.


User currently offlineMSJYOP28Apilot From United States of America, joined Jul 2009, 219 posts, RR: 1
Reply 12, posted (1 year 9 months 2 days 20 hours ago) and read 2365 times:

One thing to consider is because taxi times were long on the ground and the flight would have been early if it werent the taxi times is that airlines try very hard to not have planes leave and arrive early due to gate and ground congestion caused by early arrivals into hubs. If the crew accepted direct OCS, it likely could have cut the flight time down and caused it to arrive too soon. The dispatcher likely sent the crew an ACARS message as soon as it looked like the flight would arrive early and asked them to slow down. I checked flightaware for the day in question and couldnt find any B757 filed anything but /Q for SEA-DEN which indicates the aircraft likely, but not for certain, had RNAV.

I doubt tankering would cause such a max landing weight issue though with some incompetent dispatching by the dispatcher it is possible. One of the first rules of tankering is to not cause unnecessary weight issues.

After looking at the SEA SIDs, they show tree obstacles in the departure path off of 16L. I imagine that a more powerful takeoff was used to safely clear the obstacles in compliance with FAR obstacle clearance distances.


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