wilcharl
Posts: 1156
Joined: Sun Jun 25, 2000 11:19 am

Fuel Saving/Waisitng Procdedurs

Thu Dec 28, 2000 5:49 am

I have noticed recently alot of airlines have stoped running the apu on the ground. Does this equal a fuel savings? Ive noticed DL and FL both are doing this, I see it as a waste, an aircraft arrives in the gate, and the time it takes to get ground power connected an engine is left running, then it always seems as soon as the crew deplanes the next crew comes on and the 1st thing they do is light off the apu. Not to mention the safety hazard this causes with ground vehicles getting blown over by running engines. I really dont see the logic here... I know there is a certain amount of fuel burned during apu start, but it has to be started regardless. I also kind of see maybe logic in it reducing the time on the APU keeping them from wearing out faster but I still fail to see the logic. Also when do you normaly light the apu off? During decent once you hit the ground? I was on one aircraft that had the apu bell rinigng when they went to light it on approach. They pulled the fire handles and the alarm stoped. Apparently there was no fire though but we sure made it in fast and had a nice welcome from the ARFF guys welcome us. I think approach would be a bad place to light it becasue if something does go wrong you have enough stuff to deal with getting the aircraft on the ground not having to worry about punching out a fire. Also ive seen aircraft doing single engine taxis after powerback or only lighting one engine after pushback. I know this is a very common procedure but what are y'alls opinons of it... This makes me think of NW 255 where they pulled the aural warning system ciricuit breaker since they did single engine taxies so tehy wouldnt have to deal with being told the slats werent set when they pushed the throttle forward to taxi and ended up taking off without without the aircraft configured for departure. I also think there was a 727 that the center engine never got lit ... What do y'all think?
 
Greeneyes53787
Posts: 817
Joined: Tue Aug 08, 2000 10:34 am

RE: Fuel Saving/Waisitng Procdedurs

Thu Dec 28, 2000 7:13 am

Try some paragraph breaks. I get lost reading your post- and it sounds pretty good.

G
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: Fuel Saving/Waisitng Procdedurs

Thu Dec 28, 2000 8:44 am

> I see it as a waste, an aircraft arrives in the gate, and the time
>it takes to get ground power connected an engine is left running...

The only number I recall was "8 minutes" for B757. It was cheaper to keep one engine running for up to 8 minutes waiting for ground air/electric than to start APU and shutdown both engines during those 8 minutes. This economic model took into account the APU cycles and wear/tear on APU as well as fuel burn.

OTOH; once one has the MD90 up/running on internal power, there is no way I'm going to shift electrical power to any outside source... NO EXCEPTIONS! That means the APU (if it is working) is going to be on everytime the aircraft parks. One electrical "hic-up" and the plane could be down for 20-40 minutes trying to get everything working properly again (if not longer).

>then it always seems as soon as the crew deplanes the next crew
>comes on and the 1st thing they do is light off the apu.

Inbound crew is leaving and may not know when the plane is departing (or they may not care) so shutting down may be appropriate (checklist item?). Outbound crew will have two major concerns; a) reliable electrical power and air source for starting and, b) comfortable cabin air temperature.

>Also when do you normaly light the apu off?

The "ideal" situation is to have the APU up and running no more than 1 minute prior to parking at the gate. Reality means we usually start it immediately after clearing the runway (I prefer one-engine taxi).

>Also ive seen aircraft doing single engine taxis after powerback or only
>lighting one engine after pushback. I know this is a very common
>procedure but what are y'alls opinons of it...

Very common. No big deal.

>This makes me think of NW 255 where they pulled the aural warning
>system ciricuit breaker since they did single engine taxies so tehy
>wouldnt have to deal with being told the slats werent set when
>they pushed the throttle forward to taxi and ended up taking off
>without without the aircraft configured for departure.

Never pulled the C/B on the MD80 for single engine taxi. One just lives with the warning(s) since it is so rare anyway. OTOH, the MD80 trained folks driving the MD90 always use too much power... all the time!  

*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
NKP S2
Posts: 1665
Joined: Mon Dec 20, 1999 3:16 am

RE: Fuel Saving/Waisitng Procdedurs

Thu Dec 28, 2000 3:19 pm

Though bean counters may disagree, it seems like "false economy" to shut an APU down for 30 minutes just to save fuel. It sounds great short term but doesn't factor in long term APU maintainance/replacement costs. Saving 30-45 minutes of fuel consumption is not an acceptable tradeoff IMO due to the extra wear and tear that starts and shutdowns cause APU's...Thermal shock on the turbine wheel and aft bearings chief among them.
 
UAL Bagsmasher
Posts: 1839
Joined: Wed Sep 08, 1999 12:52 pm

RE: Fuel Saving/Waisitng Procdedurs

Thu Dec 28, 2000 3:36 pm

We had this discussion at work a while ago. We were told it costs somewhere around $25.00/hour to run the APU on a 737. Normally when one of our aircraft arrives at the gate, it will sit with #1 engine running for up to 3 or 4 minutes until the ground power is hooked up. If it isn't hooked up by then, the crew will usually start the APU anyways. The point we were discussing was the amount of bags missing their connections because we cannot drive behind a running engine. Each bag that misses it's flight costs roughly $125 to deliver to the pax. More so for an INTL bag. I myself cannot count the number of times I have missed bags due to a running engine. So what's the lesser of two evils? Running an APU at $25.00 per hour, or missing 10 bags at a cost of $125 each?? You decide.
 
prebennorholm
Posts: 6430
Joined: Tue Mar 21, 2000 6:25 am

RE: UAL Bagsmasher

Fri Dec 29, 2000 2:24 am

UAL Bagsmasher wrote:
-------------------------------
.... Each bag that misses it's flight costs roughly $125 to deliver to the pax. More so for an INTL bag. I myself cannot count the number of times I have missed bags due to a running engine. So what's the lesser of two evils? Running an APU at $25.00 per hour, or missing 10 bags at a cost of $125 each?? You decide.
-------------------------------

No, UAL Bagsmasher, you are totally wrong with those figures.
I won't disagree with the $25/hr APU cost.
The same with the $125 missed bag DELIVERY cost.
But you are very wrong because you simply missed the by far higest cost for your company: Missed customer confidence.
Every time one single bag doesn't get on the same plane as it's owner, then the next day in avarage fifty potential customers will know exactly what happened and which airline company caused its passenger this ultimate discomfort and trouble.
You are talking about 2-digit and small 3-digit figures. But the real figures are high 4-digit figures for your company.
Believe me, I am right!!!
It is not a loss for the industry as a whole. People need to fly. Only very few has the option to take the car or train for the safety of their properties, working tools, business presentation materials etc. - what you call "bags". But they often have the option to fly a slightly different route in order to avoid one specific airline company.
You just make your competitors laugh all way to their bank every time a bag does not arrive on the belt as your customer expects.
Best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs
 
UAL Bagsmasher
Posts: 1839
Joined: Wed Sep 08, 1999 12:52 pm

RE: Prebennorholm

Fri Dec 29, 2000 2:53 am

Good point! Just all the more reason why crews should start the APU, provided it isn't INOP, before they reach the gate.
 
prebennorholm
Posts: 6430
Joined: Tue Mar 21, 2000 6:25 am

RE: UAL Bagsmasher

Fri Dec 29, 2000 3:27 am

Exactly, UAL Bagsmasher.
The airline industry is a pure service industry.
I have earned my butter for my bread during the last 30 years in another service industry. Our rules have always been:
1. Give the customer just a little more than he expects, and he will be happy. He may even tell his wife.
2. Give the customer exactly what he expects, and he won't notice you.
3. Give the customer just a little less than he expects, and he will be very disappointed, and he will use every opportunity to tell about his experiences. The story will snowball and Hans Christian Andersen said it best 150 years ago when he wrote his fairytale about the feather and the five chicken.
Best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs
 
me
Posts: 220
Joined: Sat Oct 21, 2000 4:57 am

RE: UAL Bagsmasher

Fri Dec 29, 2000 5:57 am

Joe L. doesn't want the APU turned on, so I don't turn it on.

Does it make sense? Probably not, maybe a little. Who knows??
 
prebennorholm
Posts: 6430
Joined: Tue Mar 21, 2000 6:25 am

RE: UAL Bagsmasher

Fri Dec 29, 2000 7:23 am

Me wrote:
-------------------------------
Joe L. doesn't want the APU turned on, so I don't turn it on.
Does it make sense? Probably not, maybe a little. Who knows??
-------------------------------

Who the h#¤* is Joe L.?
There may be many good reasons for not turning on the APU, but:
If Joe L. thinks that it is a good idea to save $25 and by doing so risk that my bag (which often contains the very reason for my trip) is sent on another plane into an unknown future, and then delivered by taxi to the place where I may happen to be at work - directed by me on my mobile phone in my left hand, while I am entertaining a bunch of my customers with the right hand... etc.
Then I know one thing about Joe L.:
I know that I don't like him.
Just in case Joe L. should also somehow be involved in the airline business, then I know one more thing about him: He is not a clever man. He should instead try to be a good friend of me, because it is people like me who pay his salary.
The whole reason for people working in the airline industry is often to earn a salary. That makes sense, for sure.
Best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs
 
wilcharl
Posts: 1156
Joined: Sun Jun 25, 2000 11:19 am

RE: Fuel Saving/Waisitng Procdedurs

Fri Dec 29, 2000 8:21 am

Joe L. would be the CEO of Airtran Airways. Im just waiting for someone or something to become FOD and see how much that cost an airline, since it appears to be widespread SOP in the industry now, im waiting for someone or something to suck into an enigne. Lets take a 737 @ UAL... I read somewhere the loss of a life is roughly 1,000,000 bucks, plus the cost of the engine, plus the cost of the aircraft being AOG for a long time while they wait on the engine swap plus the cost of reaccomidating the pax, plus the frightend pax that saw the ramp guy walk over to chock the mains while #1 was still runing and got sucked in etc etc etc...

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