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A-320 Single Engine Taxi out Myth Busters

Old 08-02-2010, 06:38 PM
  #1  
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Default A-320 Single Engine Taxi out Myth Busters

MYTH BUSTERS-SINGLE ENGINE (SE) TAXI
This article may well have been titled; “Confessions of a start em both up captain”. I’ll be the first to admit that my use of SE taxi had been less than optimum in the past. A recent email from Captain Glen Fink stated that the A-320 fleet was performing less than 10% of SE taxi outs.
I decided to take a look at my own operation during the month of June, and see if it was possible to increase my use of SE taxi out. I was determined to increase my SE taxi out, though honestly, I didn’t think it was possible due to some well held beliefs, or myths. It seems that the A320 pilots hold a paradigm which does not embrace SE taxi. I set out to debunk the no SE taxi myths. Let’s take a look at some of those myths.

I DON’T WANT TO LOAD UP MY FIRST OFFICER WITH A SINGLE ENGINE TAXI; START EM BOTH UP! BUSTED In the past this may have been a reasonable CRM concern. Delta North aircraft would often receive their ‘numbers’ late in the taxi. However with the cutover to the Delta AWABS/WDR we now receive our numbers at the gate. As Captain, you will need to adjust the second engine start to your F/Os comfort level. As the F/O becomes more comfortable with the delayed engine start you can increase the amount of SE taxi time. Almost every F/O that flew with me during June was initially uncomfortable with the delayed engine start. Surprising? No. If only 10% of F/Os were getting landings I’d bet they’d be uncomfortable with landings too. By the end of the trip, SE flow was a standard routine.

IT’S THE FIRST FLIGHT OF THE DAY; START EM BOTH UP. BUSTED During June seven of my flights were first flights of the day (30%). Though the requirement to have 5 minutes of warm-up time limited the amount of SE taxi I was surprised at how many minutes of SE taxi I had actually performed. Even at SMF with a short taxi we recorded 4 minutes of SE taxi.
**Least SE taxi out time for first flights of the day; 3 min, Highest SE taxi out; 6 min, avg SE taxi out 4.6 min**

WE ARE TOO HEAVY FOR SINGLE ENGINE TAXI; START EM BOTH UP BUSTED My weights varied from 128.7 to 165.0 pounds. On all but one flight at max takeoff weight I was able to SE taxi. Some factors for considerations in a successful SE taxi out included concrete vs blacktop. Direction of turn on taxi out (right turns more reasonable N1s than left turns) For example, in the alley at LGA you may need to start both for the initial taxi, then shut one down following the required cool down. Heavy SE taxi requires planning. For example taxi to Rwy 4 at LGA not a problem…crossing Rwy 4 taxi to 13 at taxiway ‘F’ may require an early 2nd engine start.
**Lowest SE taxi out weight;128.7 lbs Highest SE taxi out weight;163.4 lbs. Average SE taxi out weight; 146.1 lbs**

ANY WEIGHTS GREATER THAN MAX LANDING WEIGHT WILL REQUIRE EXCESSIVE N1s; START EM BOTH UP. BUSTED This myth may have developed life during the FNWA Vol 1 days (along with max N1s) See the accompanying spread sheet. The average N1 for breakaway was 32.5%. Again planning ahead will mitigate the impact of breakaway thrust. Have the push crew turn your tail during the push back so that you don’t need to turn into engine 1. If unable to do that, ask for a deeper push than normal to allow forward taxi prior to turning. Carry the thrust into the turn etc. Know where your tail is pointing Is 45% N1 breakaway a big deal if your tail is clear of personnel and carts/equipment? Max N1 breakaway was experienced at LAX (161,300 lbs) at the top of the alley; 48%. Tail was clear of personnel with no objects behind the jet An interesting observation here is that we had a heavier taxi out weight of 163,400 in CVG with only a 37% N1 breakaway. The difference?; Concrete and slight downhill. Plenty of variables affect SE taxi at heavy weights. The key take away is, don’t summarily rule out SE taxi simply based on weight.
**Lowest breakaway 20% N1, highest breakaway 48% N1, Average breakaway 32.5% N1**

I’LL ONLY SAVE A FEW MINUTES, IT’S NOT WORTH THE HASSLE; START EM BOTH UP BUSTED Probably the biggest myth of all. It’s been said before, but it needs to be repeated; the cumulative savings of SE taxi adds up. With the number of flights we operate a day, you and I can make a significant impact in fuel cost savings. What savings did one Captain achieve in June?
**In 20 flights utilizing SE taxi, a total of 143 minutes of SE taxi was recorded.( average SE taxi out was 7.15 minutes!) **
**Total SE taxi fuel saved 2,280 lbs.**
**APU burn during SE taxi: 715 lbs (5 lbs/min)**
**Net SE taxi fuel saved: 1,565 lbs ( 226.8 gallons)**

If you’ve stayed with me so far, thanks. So what‘s the way ahead? First of all, let’s make SE taxi a conscious decision in your flight planning. No different than preflight/taxi/take off/climb out/ cruise/ descent/ approach / landing/ and taxi-in.

I can already hear the howls…………They don’t have park crew waiting for us…They don’t have ext pwr waiting for us….They have us carry too much fuel….Yes, Yes and Yes. However, these are things you as a crew have little control over. Where you have a direct impact on fuel savings however is determining when you start the second engine!

My personal wish list? I’d like to see the cross bleed procedure revisited. Currently the A-320 requires the parking brake set for cross bleed start making that option impractical in most SE taxi scenarios. My data shows that if the APU could have been shut down, and cross bleed utilized for the second engine start an additional 715 pounds of fuel would have been saved.

If you’re still with me great…you may be asking; ‘OK, so what’s in it for me?’ Think job security.

Captains, your next upgrade may be impacted by higher operational costs, but your junior First Officers will be the first to be negatively impacted by higher operational costs. First Officers, become proactive in the single engine start discussion. Captains, I ask you to challenge yourself and increase your SE taxi time

We can do better, we must do better.
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Old 08-02-2010, 07:02 PM
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Only 10 reasons? If you just take off on the ramp, problem solved.
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Old 08-02-2010, 07:06 PM
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I'm not sure if this was just an issue at NW/Delta, but in my 3 yrs at jetblue, we (well the CA's) chose to taxi single engine about 95% of the time and I never heard anyone give any excuse's except having large hills to taxi up.
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Old 08-02-2010, 08:22 PM
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Great post, reddog. You should have this published online somewhere.
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Old 08-02-2010, 09:01 PM
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Doesn't single engine taxi on a A320/319 mean you'll have the hydraulic PTU doing its thing the whole time until the other engine is up?

Just saying, you'll have plenty of passengers thinking that a poor dog is yapping away or that something is broke on the plane. Might as well give a heads up
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Old 08-02-2010, 09:29 PM
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Originally Posted by tortue View Post
Doesn't single engine taxi on a A320/319 mean you'll have the hydraulic PTU doing its thing the whole time until the other engine is up?

Just saying, you'll have plenty of passengers thinking that a poor dog is yapping away or that something is broke on the plane. Might as well give a heads up
There is an electric pump for the yellow system....
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Old 08-02-2010, 09:52 PM
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Nice post reddog, and thanks for putting in the effort to track it. I agree, that the biggest myth is the one you exposed below. If we had 50 or 60 airplanes you might me able to say that it's not making much of a difference. But, if I'm not mistaken, we're hovering in the 850 range of aircraft (not counting the W.O. RJ's) And your numbers are based on the "small bus", one of our leaner burning aircraft. Extrapolate that to include the "big bus", 75/6, 777 and "whale"....that's some serious dollars.


Originally Posted by reddog25 View Post

I’LL ONLY SAVE A FEW MINUTES, IT’S NOT WORTH THE HASSLE; START EM BOTH UP BUSTED Probably the biggest myth of all. It’s been said before, but it needs to be repeated; the cumulative savings of SE taxi adds up. With the number of flights we operate a day, you and I can make a significant impact in fuel cost savings. What savings did one Captain achieve in June?
**In 20 flights utilizing SE taxi, a total of 143 minutes of SE taxi was recorded.( average SE taxi out was 7.15 minutes!) **
**Total SE taxi fuel saved 2,280 lbs.**
**APU burn during SE taxi: 715 lbs (5 lbs/min)**
**Net SE taxi fuel saved: 1,565 lbs ( 226.8 gallons)**
Please forward this to your fleet manager and S.D.
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Old 08-03-2010, 01:36 AM
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Originally Posted by tzskipper View Post
There is an electric pump for the yellow system....
I've found on some airplanes even with the electric pump on, the PTU is still on. Sometimes the electric pump does not put out enough pressure to keep the PTU from coming on. In theory, the PTU is not supposed to be on with the electric pump on, but it does not always work like that.
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Old 08-03-2010, 03:42 AM
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Originally Posted by hockeypilot44 View Post
I've found on some airplanes even with the electric pump on, the PTU is still on. Sometimes the electric pump does not put out enough pressure to keep the PTU from coming on. In theory, the PTU is not supposed to be on with the electric pump on, but it does not always work like that.
really? I have never seen that before...and if I did I would think the pump would need to be written up. Its supposed to put out 3000psi and if its not then its not working properly.
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Old 08-03-2010, 05:26 AM
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Originally Posted by reddog25 View Post
MYTH BUSTERS-SINGLE ENGINE (SE) TAXI
This article may well have been titled; “Confessions of a start em both up captain”. I’ll be the first to admit that my use of SE taxi had been less than optimum in the past. A recent email from Captain Glen Fink stated that the A-320 fleet was performing less than 10% of SE taxi outs.
I decided to take a look at my own operation during the month of June, and see if it was possible to increase my use of SE taxi out. I was determined to increase my SE taxi out, though honestly, I didn’t think it was possible due to some well held beliefs, or myths. It seems that the A320 pilots hold a paradigm which does not embrace SE taxi. I set out to debunk the no SE taxi myths. Let’s take a look at some of those myths.

I DON’T WANT TO LOAD UP MY FIRST OFFICER WITH A SINGLE ENGINE TAXI; START EM BOTH UP! BUSTED In the past this may have been a reasonable CRM concern. Delta North aircraft would often receive their ‘numbers’ late in the taxi. However with the cutover to the Delta AWABS/WDR we now receive our numbers at the gate. As Captain, you will need to adjust the second engine start to your F/Os comfort level. As the F/O becomes more comfortable with the delayed engine start you can increase the amount of SE taxi time. Almost every F/O that flew with me during June was initially uncomfortable with the delayed engine start. Surprising? No. If only 10% of F/Os were getting landings I’d bet they’d be uncomfortable with landings too. By the end of the trip, SE flow was a standard routine.

IT’S THE FIRST FLIGHT OF THE DAY; START EM BOTH UP. BUSTED During June seven of my flights were first flights of the day (30%). Though the requirement to have 5 minutes of warm-up time limited the amount of SE taxi I was surprised at how many minutes of SE taxi I had actually performed. Even at SMF with a short taxi we recorded 4 minutes of SE taxi.
**Least SE taxi out time for first flights of the day; 3 min, Highest SE taxi out; 6 min, avg SE taxi out 4.6 min**

WE ARE TOO HEAVY FOR SINGLE ENGINE TAXI; START EM BOTH UP BUSTED My weights varied from 128.7 to 165.0 pounds. On all but one flight at max takeoff weight I was able to SE taxi. Some factors for considerations in a successful SE taxi out included concrete vs blacktop. Direction of turn on taxi out (right turns more reasonable N1s than left turns) For example, in the alley at LGA you may need to start both for the initial taxi, then shut one down following the required cool down. Heavy SE taxi requires planning. For example taxi to Rwy 4 at LGA not a problem…crossing Rwy 4 taxi to 13 at taxiway ‘F’ may require an early 2nd engine start.
**Lowest SE taxi out weight;128.7 lbs Highest SE taxi out weight;163.4 lbs. Average SE taxi out weight; 146.1 lbs**

ANY WEIGHTS GREATER THAN MAX LANDING WEIGHT WILL REQUIRE EXCESSIVE N1s; START EM BOTH UP. BUSTED This myth may have developed life during the FNWA Vol 1 days (along with max N1s) See the accompanying spread sheet. The average N1 for breakaway was 32.5%. Again planning ahead will mitigate the impact of breakaway thrust. Have the push crew turn your tail during the push back so that you don’t need to turn into engine 1. If unable to do that, ask for a deeper push than normal to allow forward taxi prior to turning. Carry the thrust into the turn etc. Know where your tail is pointing Is 45% N1 breakaway a big deal if your tail is clear of personnel and carts/equipment? Max N1 breakaway was experienced at LAX (161,300 lbs) at the top of the alley; 48%. Tail was clear of personnel with no objects behind the jet An interesting observation here is that we had a heavier taxi out weight of 163,400 in CVG with only a 37% N1 breakaway. The difference?; Concrete and slight downhill. Plenty of variables affect SE taxi at heavy weights. The key take away is, don’t summarily rule out SE taxi simply based on weight.
**Lowest breakaway 20% N1, highest breakaway 48% N1, Average breakaway 32.5% N1**

I’LL ONLY SAVE A FEW MINUTES, IT’S NOT WORTH THE HASSLE; START EM BOTH UP BUSTED Probably the biggest myth of all. It’s been said before, but it needs to be repeated; the cumulative savings of SE taxi adds up. With the number of flights we operate a day, you and I can make a significant impact in fuel cost savings. What savings did one Captain achieve in June?
**In 20 flights utilizing SE taxi, a total of 143 minutes of SE taxi was recorded.( average SE taxi out was 7.15 minutes!) **
**Total SE taxi fuel saved 2,280 lbs.**
**APU burn during SE taxi: 715 lbs (5 lbs/min)**
**Net SE taxi fuel saved: 1,565 lbs ( 226.8 gallons)**

If you’ve stayed with me so far, thanks. So what‘s the way ahead? First of all, let’s make SE taxi a conscious decision in your flight planning. No different than preflight/taxi/take off/climb out/ cruise/ descent/ approach / landing/ and taxi-in.

I can already hear the howls…………They don’t have park crew waiting for us…They don’t have ext pwr waiting for us….They have us carry too much fuel….Yes, Yes and Yes. However, these are things you as a crew have little control over. Where you have a direct impact on fuel savings however is determining when you start the second engine!

My personal wish list? I’d like to see the cross bleed procedure revisited. Currently the A-320 requires the parking brake set for cross bleed start making that option impractical in most SE taxi scenarios. My data shows that if the APU could have been shut down, and cross bleed utilized for the second engine start an additional 715 pounds of fuel would have been saved.

If you’re still with me great…you may be asking; ‘OK, so what’s in it for me?’ Think job security.

Captains, your next upgrade may be impacted by higher operational costs, but your junior First Officers will be the first to be negatively impacted by higher operational costs. First Officers, become proactive in the single engine start discussion. Captains, I ask you to challenge yourself and increase your SE taxi time

We can do better, we must do better.
You need to put this in the Trim Tab or other company circular. This is well done.
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