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speedracer1407
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ERJ: Burning Fuel On The Taxiway?

Mon Aug 23, 2010 5:21 am

Hi folks,

Sorry about the cryptic title. I couldn't think of a better one.

A couple weeks ago, I was on a United Express ERJ 145 departing from STL for ORD about 3 PM or so. We pushed back from the gate a bit early and taxied briskly to very near the runway, and stopped.

Then the engines spooled up a bit. It was a noticeable spool-up, and I'm certain it wasn't just the 2nd engine starting because I distinctly heard both engines start in sequence right after the pushback.

Shortly after I heard the engines spool, a pilot got on the PA to explain the situation, but the volume was too low to be audible. It was a short explanation anyway: something like "we'll be sitting here for a bit while we diagnose a situation." The engines remained sounded like well above idle for a good 15-20 minutes before finally returning to idle. About 5 minutes after the spool-down, we simply turned left onto the runway and took off.

Traffic at the airport was minimal. There were no other planes waiting to take off in front of us, and landing traffic on the runway we eventually took off from was sparse.

I'm curious why we sat on the taxiway for so long with the engines spooled up; I've never experienced that before. My first thought is that we departed the gate with too much fuel due to a miscalculation realized after pushback, exceeding either MTOW for the conditions (it was a VERY hot day in St. Louis), MLW in the short hop to ORD, or some other parameter I can't think of.

Problem is, after 6 years of geeking-out on this forum and others, I've never heard of deliberately burning fuel while stationary on the tarmac to meet takeoff performance requirements.

Anyone else who knows better than I have an idea what may have happened here?
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
 
jetmatt777
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RE: ERJ: Burning Fuel On The Taxiway?

Mon Aug 23, 2010 6:03 am

I've seen similar situations. One example was at OKC where a Pinnacle CRJ crew asked ATC if they could wait it out for 5-10 minutes to burn some fuel off before departing. It was likely miscalculated fuel. It's a shame with all of the cost control and bottom line issues, that this has to be done in some situations. But that is life.
 
Goldenshield
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RE: ERJ: Burning Fuel On The Taxiway?

Mon Aug 23, 2010 10:34 am

Quoting speedracer1407 (Thread starter):
I've never heard of deliberately burning fuel while stationary on the tarmac to meet takeoff performance requirements.

With smaller aircraft (and now higher passenger weights) come smaller windows of opportunity to allow for oddities in a load plan.

As a dispatcher, I set the minimum dispatch fuel for a flight using an estimated passenger weight burden (Pax + bags). The amount of bags passengers bring with them can vary wildly, though, and might put the plane over the original planned payload. With many weight critical aircraft though (such as the CRJ-200,) if you are over by a couple hundred pounds, and if the conditions allow for it, then to avoid a customer service problem, it's best to just eat those 200 lbs of fuel.

Overall, I wouldn't say that there was too much fuel on board.  
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
FlyASAGuy2005
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RE: ERJ: Burning Fuel On The Taxiway?

Mon Aug 23, 2010 2:41 pm

This actually happened a while back (couple years maybe?) out of LGA on a Delta 75 heading to Atlanta. We pulled out the gate and taxied down on bravo for 31 and we suddenly pulled off onto Alpha. We just kind of sat for a minute then te engines spooled up and held for about a minute then it went back down. Went back up for about a minute or two then went back down. We did this for about 5 minutes then we just pulled forward and took of like normal. Getting off the a/c in Atlanta I asked the pilots what was up in LGA and they said they were getting funky readings and they were doing engine run-ups to clear things up and everything turned out to be ok.
What gets measured gets done.
 
mrocktor
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RE: ERJ: Burning Fuel On The Taxiway?

Mon Aug 23, 2010 2:59 pm

As a broader answer, every plane has a Maximum Ramp Weight higher than the Maximum Takeoff Weight (this is so you can taxi and wait in congested airports and still take off at MTOW for a limit range trip). If you get overfilled and end up not having to wait as long as expected, this could happen.

Another possibility is that the plane simply was overfueled (human or system error). Burning off fuel is a lot simpler than defueling (which requires you to deboard the aircraft in many or most cases).
 
Lemmy
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RE: ERJ: Burning Fuel On The Taxiway?

Mon Aug 23, 2010 3:08 pm

Exact same thing happened to me on a very hot day flying an ERJ SGF-ORD. We sat for 5 or 10 minutes with the engines spooled up before takeoff. The pilot explained that we were a little heavy and needed to lighten the load.

Maybe there's something unique about ERJs, full passenger loads, and short flights?
I am a patient boy ...
 
FlyHossD
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RE: ERJ: Burning Fuel On The Taxiway?

Tue Aug 24, 2010 4:49 pm

Quoting Goldenshield (Reply 2):
As a dispatcher, I set the minimum dispatch fuel for a flight using an estimated passenger weight burden (Pax + bags). The amount of bags passengers bring with them can vary wildly, though, and might put the plane over the original planned payload. With many weight critical aircraft though (such as the CRJ-200,) if you are over by a couple hundred pounds, and if the conditions allow for it, then to avoid a customer service problem, it's best to just eat those 200 lbs of fuel.

Overall, I wouldn't say that there was too much fuel on board.

That's well stated, but I have had a situation where we've been over fueled. We requested defueling, but that would have taken too long as the gate was needed for another aircraft just minutes after our scheduled departure time.

So we had no choice but to burn the fuel on the taxi way. I don't recall the exact time, but it was about 25 minutes with both engines and the APU running.

On arrival, a company check airman (who had been riding as a passenger) started to lecture me about running the engines for an extended delay. I stopped his lecture and explained the "big picture." He seemed to be shocked that
Ops would chose to burn the fuel over finding another gate for the next aircraft.
My statements do not represent my former employer or my current employer and are my opinions only.
 
Goldenshield
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RE: ERJ: Burning Fuel On The Taxiway?

Tue Aug 24, 2010 5:29 pm

Quoting FlyHossD (Reply 6):
We requested defueling, but that would have taken too long as the gate was needed for another aircraft just minutes after our scheduled departure time.

You do bring up a valid point. Sometimes fuelers forget the number, or mis-calculate (if no reference is available,) or are new and don't know the the tricks to fuel the birds correctly (when fueling CRJs, the fuel tended to slosh in the tank until it settled, giving an innacurate---and deceivingly lower---reading.)
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
N243NW
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RE: ERJ: Burning Fuel On The Taxiway?

Tue Aug 24, 2010 6:03 pm

Back in 2005 we had a maintenance problem at about 6:45am in an ERJ from MKE-STL and had to wait about an hour until the mechanics arrived at work. During that time, the pilot said he was going to start #2 and let it run at the gate to burn off some extra fuel. We sat there for probably about 45 minutes with the engine idling until MX stepped onto the airplane, took a look at the pilot's windscreen and gave us the seal of approval to depart.

It seems strange that we weren't simply defueled even though we were at the gate and had plenty of time before departure. Is it an involved process?
B-52s don't take off. They scare the ground away.
 
musapapaya
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RE: ERJ: Burning Fuel On The Taxiway?

Tue Aug 24, 2010 6:57 pm

Back in 2004, I experienced the same thing. It was an AA 777 from LHR to JFK. We were sitting in LHR for some 30 minutes spooling up and burning fuel, thye Captain explained that they got too much fuel on etc....

I did not understand that for a big plane like a 777, will that bit of fuel matter much? At that time I dont know much about planes so did not ask the question.

regards
musapapaya
 
bohica
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RE: ERJ: Burning Fuel On The Taxiway?

Tue Aug 24, 2010 7:14 pm

Quoting FlyHossD (Reply 6):
That's well stated, but I have had a situation where we've been over fueled. We requested defueling, but that would have taken too long as the gate was needed for another aircraft just minutes after our scheduled departure time.

So we had no choice but to burn the fuel on the taxi way. I don't recall the exact time, but it was about 25 minutes with both engines and the APU running.

On arrival, a company check airman (who had been riding as a passenger) started to lecture me about running the engines for an extended delay. I stopped his lecture and explained the "big picture." He seemed to be shocked that
Ops would chose to burn the fuel over finding another gate for the next aircraft.

From an Ops point of view the arriving airplane would have been burning fuel while waiting for the plane at the gate to be defueled. It's a no-win situation. Push the plane. I would be more than happy to deal with the check airman.

Quoting mrocktor (Reply 4):
As a broader answer, every plane has a Maximum Ramp Weight higher than the Maximum Takeoff Weight (this is so you can taxi and wait in congested airports and still take off at MTOW for a limit range trip). If you get overfilled and end up not having to wait as long as expected, this could happen.

It may also have to do with the landing weight at the destination.
 
Alias1024
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RE: ERJ: Burning Fuel On The Taxiway?

Tue Aug 24, 2010 9:05 pm

Just one other thought besides the overweight scenario everyone has mentioned. Do you remember if the aircraft had to use an air cart to start the engines?

Another unlikely scenario is that the APU was inoperative and as the aircraft approached the runway they got a last minute flow time into ORD from air traffic control. They might have kept the engines above idle to provide more bleed air to the packs for air conditioning while they did their troubleshooting.
It is a mistake to think you can solve any major problems with just potatoes.
 
atct
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RE: ERJ: Burning Fuel On The Taxiway?

Tue Aug 24, 2010 9:35 pm

Quoting speedracer1407 (Thread starter):
Problem is, after 6 years of geeking-out on this forum and others, I've never heard of deliberately burning fuel while stationary on the tarmac to meet takeoff performance requirements.

Happens all the time when the possibility of weather adds extra fuel for CDR's and re-routes.

ATCT
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FlyHossD
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RE: ERJ: Burning Fuel On The Taxiway?

Tue Aug 24, 2010 10:27 pm

Quoting bohica (Reply 10):
From an Ops point of view the arriving airplane would have been burning fuel while waiting for the plane at the gate to be defueled. It's a no-win situation.


It's not that cut-and-dried. There would have been no need for the arriving aircraft to run both engines and also, the APU.

There may have been other gates available, too. IIRC, there were empty gates available on the other side of the concourse and I believe some of them could have accommodated the arriving aircraft.

By not delaying the arriving aircraft (and passengers), the delay was passed on to us and our passengers.

I have had situations where the airplane was over-fueled and the decision was made to "de-fuel" the airplane. In the most recent case, we waited for over 40 minutes for the de-fueling to be completed. It turned out that the first de-fueling truck was already full, so another had to be found.
My statements do not represent my former employer or my current employer and are my opinions only.
 
Mir
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RE: ERJ: Burning Fuel On The Taxiway?

Wed Aug 25, 2010 6:12 am

Quoting musapapaya (Reply 9):
I did not understand that for a big plane like a 777, will that bit of fuel matter much?

Limits are limits. Will a 777 fly any differently at MTOW+1000lbs as opposed to MTOW? Probably not, but you have to draw the line somewhere.

-Mir
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HAWK21M
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RE: ERJ: Burning Fuel On The Taxiway?

Wed Aug 25, 2010 2:42 pm

Looks like the crew found the Fuel to be a bit excess & needed to burn it.

Quoting N243NW (Reply 8):
It seems strange that we weren't simply defueled even though we were at the gate and had plenty of time before departure. Is it an involved process?

Defuelling would have been more economical here.
regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
Goldenshield
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RE: ERJ: Burning Fuel On The Taxiway?

Wed Aug 25, 2010 4:09 pm

Quoting HAWK21M (Reply 15):
Defuelling would have been more economical here

And take a delay just to off a couple hundred pounds of fuel? Hell no!
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
N243NW
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RE: ERJ: Burning Fuel On The Taxiway?

Wed Aug 25, 2010 5:24 pm

Quoting Goldenshield (Reply 16):
And take a delay just to off a couple hundred pounds of fuel? Hell no!

Not if the defueling could be completed while we were just sitting there anyway due to the mechanical issue I mentioned. We had the engine running for the better part of an hour.
B-52s don't take off. They scare the ground away.
 
Goldenshield
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RE: ERJ: Burning Fuel On The Taxiway?

Wed Aug 25, 2010 7:11 pm

Quoting N243NW (Reply 17):
Not if the defueling could be completed while we were just sitting there anyway due to the mechanical issue I mentioned. We had the engine running for the better part of an hour.

It still wouldn't have been that much fuel. 800 lbs at most. Run both engines, and rev them up to breakaway thrust, and you'd have that down in a few minutes.

Also, calling out the fuel truck costs money. It could've been (much) more cost efficient to burn what he had on board than to call out another truck.
Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
 
speedracer1407
Topic Author
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RE: ERJ: Burning Fuel On The Taxiway?

Thu Aug 26, 2010 2:43 am

Quoting Alias1024 (Reply 11):
Another unlikely scenario is that the APU was inoperative and as the aircraft approached the runway they got a last minute flow time into ORD from air traffic control. They might have kept the engines above idle to provide more bleed air to the packs for air conditioning while they did their troubleshooting.

Thanks for all your replies, it seems like it's not quite as surprising or unusual as I thought.

Alias: that's something I hadn't thought of at all. And it certainly was hot that day: something like 95+ with high humidity.

However, we disembarked via air stairs onto the tarmac at ORD and the the APU was shrieking away while we waited for our bags. I guess the APU could have been cranky before the flight though.
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
 
mrocktor
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RE: ERJ: Burning Fuel On The Taxiway?

Thu Aug 26, 2010 7:08 pm

Quoting N243NW (Reply 17):
Not if the defueling could be completed while we were just sitting there anyway due to the mechanical issue I mentioned.

Not every plane can be defueled with pax on board.
 
maddogjt8d
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RE: ERJ: Burning Fuel On The Taxiway?

Thu Aug 26, 2010 7:31 pm

Last week I was on an MD-88 BNA-ATL and we had both engines running (actually started with an air-start cart at the gate), but as we were taxiing out we got an ATC slot time for takeoff. While we were sitting in the hot sun, in order to get the A/C working harder, the captain pushed the throttles up to almost break-away thrust and held them there for a good 10 minutes. The difference in temperature in the cabin was quite noticeable from the taxi-out at mostly idle thrust, which was significantly warmer.

A few years back, I heard on JFK ATC an American 757 which took extra fuel anticipating a delay for waiting in line and deicing (this was a day or two after a major snow storm). He got to the front of the line pretty quickly and said he would have to sit on a taxiway for upwards of an hour to burn off excess fuel in order to depart. At the time, I thought "what a waste", but I guess it makes more financial sense then de-boarding an aircraft, calling out a fuel truck and de-fueling, etc.
 
pilotpip
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RE: ERJ: Burning Fuel On The Taxiway?

Thu Aug 26, 2010 8:25 pm

Everybody saying "just defuel" doesn't realize that the fuel can only be put back onto that company's aircraft. If you don't have a dedicated defueling truck nearby that truck is now rendered useless until all the fuel can be placed into the same company's (in this case TSA) aircraft.

There could have been a number of reasons for this and it can happen regardless of size. A likely reason could also be dispatching the aircraft with an anticipation of a departure time later than they got. Departing as scheduled and not burning additional fuel on the taxi to the runway would have resulted in arriving at ORD above max landing weight. This is a common cause of weight restrictions in the 145, especially in TSA's (I used to fly for them) which do not have thrust reversers and as a result have a lower BOW.
DMI
 
N243NW
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RE: ERJ: Burning Fuel On The Taxiway?

Thu Aug 26, 2010 10:54 pm

Quoting Goldenshield (Reply 18):
It still wouldn't have been that much fuel. 800 lbs at most. Run both engines, and rev them up to breakaway thrust, and you'd have that down in a few minutes.

Also, calling out the fuel truck costs money. It could've been (much) more cost efficient to burn what he had on board than to call out another truck.
Quoting mrocktor (Reply 20):
Not every plane can be defueled with pax on board.
Quoting pilotpip (Reply 22):
Everybody saying "just defuel" doesn't realize that the fuel can only be put back onto that company's aircraft. If you don't have a dedicated defueling truck nearby that truck is now rendered useless until all the fuel can be placed into the same company's (in this case TSA) aircraft.

Thanks for clearing up the confusion. 
B-52s don't take off. They scare the ground away.
 
fly727
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RE: ERJ: Burning Fuel On The Taxiway?

Sat Aug 28, 2010 4:59 pm

As others mentioned, I would say it was a matter of weight. Oh God, old news are so exciting! But wait, you have probably not thought about this:

Most likely the aircraft was a couple hundred pounds over structural MTOW or the actual TOW for the given conditions at the airfield (length and obstacles), selected thrust rate, weight, temperature and flap setting.

Could have been an issue with Maximum Landing Weight as well, though less likely as the ERJ is very flexible on this matter (not saying that it commonly supports landing in excess of that limitation, which by the way it can but it shouldn't).

It could also be an issue with anti-ice tests in which a certain thrust is needed in order to perform it. It is a common practice when icing conditions are present or expected during the flight; however they surely do not last 15 minutes as in your flight, err... ground wait.

Rolls-Royce also states a minimum warm up time. 4 minutes warm-up after start on cold engines (more than 90 minutes in the ground) or 2 minutes on "hot" engines (less than 90 minutes resting) or simply whatever is needed to raise the temperature and oil pressure to within limits for take off thrust setting.

Anyway, if you are a member of airliners.net most likely you weren't really bothered to wait in the aircraft, were you? 

RM.
There are no stupid questions... just stupid people!

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