warreng24
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Issues With The CFM-56 On Inter-Island Flights?

Sat Sep 17, 2011 9:32 pm

So what exactly is the technical issue with the CFM-56 engine on Hawaiian Inter-Island flights?

AQ once tried 737-400's on Inter-Island flights and found that the maintenance issues with the CFM-56 were unacceptable.

From what I gather from reading old posts in the Civil Aviation forum the issue is NOT with the scheduled on-ground time. WN and other often do short 20 or 30 min turns with the CFM-56 as well (no issues have been reported or rumored on A.net regarding the WN quick turn time and the CFM-56). The CFM-56 issues with Inter-Island flights, seem to be with the very short in-air times. Does this sound accurate? Does anyone know the exact issue?
 
Poadrim
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RE: Issues With The CFM-56 On Inter-Island Flights?

Sun Sep 18, 2011 2:34 am

From what I understand is it not the flight time it self, but because of the salt from the water that is the issue?

//Poadrim
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BMI727
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RE: Issues With The CFM-56 On Inter-Island Flights?

Sun Sep 18, 2011 3:37 am

Quoting warreng24 (Thread starter):

I think it had to do with the engines not being able to ever fully warm up or cool down over the course of a day.

Quoting Poadrim (Reply 1):
From what I understand is it not the flight time it self, but because of the salt from the water that is the issue?

The sea air doesn't do the planes any favors, but I would tend to doubt this. For one thing, Air Mike and Air Pacific seem to have no issues arising from the salt.
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tdscanuck
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RE: Issues With The CFM-56 On Inter-Island Flights?

Sun Sep 18, 2011 4:32 am

Quoting warreng24 (Thread starter):

So what exactly is the technical issue with the CFM-56 engine on Hawaiian Inter-Island flights?

Not enough time to stabilize...the engine goes from takeoff to climb to descent, basically. It's thermally stressful on the engine.

Tom.
 
Sancho99504
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RE: Issues With The CFM-56 On Inter-Island Flights?

Sun Sep 18, 2011 10:11 pm

Quoting tdscanuck (Reply 3):

Tom, I value your info and respect what you have to say. My issue is this, how can the RR BR715 handle that kind of flying, as well as the pw on the classics, and the cfm not? Thanks in advance.
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tdscanuck
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RE: Issues With The CFM-56 On Inter-Island Flights?

Mon Sep 19, 2011 1:13 am

Quoting sancho99504 (Reply 4):
My issue is this, how can the RR BR715 handle that kind of flying, as well as the pw on the classics, and the cfm not?

Lightsaber is a lot more qualified to answer this than in detail, but engine thermal response (especially vis-a-vis wear) is very dependant on detailed engine architecture...how the cooling works and where it's routed, what the clearances are, what the temperature margin is on all the components, what thermal protection is being used on which part, etc., etc. Those thing can vary wildly from engine to engine.

Tom.
 
lhcvg
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RE: Issues With The CFM-56 On Inter-Island Flights?

Wed Sep 21, 2011 3:57 pm

Offhand, doesn't this make sense given the mission of the CFM56 - longer-range travel? I'm no engineer, but it seems logical that the CFM56 has more issues than the aforementioned BR715 given the differing missions of the planes (CFM56-powered 737s and 320s are designed to do longer routes if need be, whereas the 717 was designed for the 10-segment a day short hop market).
 
mrskyguy
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RE: Issues With The CFM-56 On Inter-Island Flights?

Sat Sep 24, 2011 6:22 pm

Quoting tdscanuck (Reply 3):
Not enough time to stabilize...the engine goes from takeoff to climb to descent, basically. It's thermally stressful on the engine.

Tom, good to see you! Hope all is well with you and yours.

Specific to this post, how does WN handle the same issues on the CMF56 flying the "Texas triangle" routes? My contacts at WN have shown me the same aircraft (especially the classics) turning in 30 min or less flying back and forth between Houston, Austin, Harlingen, etc. without ample engine "rest time" between hops.
"The strength of the turbulence is directly proportional to the temperature of your coffee." -- Gunter's 2nd Law of Air
 
tdscanuck
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RE: Issues With The CFM-56 On Inter-Island Flights?

Sat Sep 24, 2011 8:30 pm

Quoting mrskyguy (Reply 7):
My contacts at WN have shown me the same aircraft (especially the classics) turning in 30 min or less flying back and forth between Houston, Austin, Harlingen, etc. without ample engine "rest time" between hops.

As I understand it, it's not the ground turn that's the problem, it's the really short flight cycle. An island hop in the Hawaiian islands is ~100-150 miles. That only gets you about half way to San Antonio from Houston.

Tom.
 
ha763
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RE: Issues With The CFM-56 On Inter-Island Flights?

Sun Sep 25, 2011 3:17 am

To add to what Tom said, WN has the ability to send their aircraft on longer routes, even within Texas, which is not exactly possible with the Interisland market. Plus, the shortest WN intra-Texas route is HOU-AUS at 148 miles, which they only have 5 round trips.
 
BMI727
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RE: Issues With The CFM-56 On Inter-Island Flights?

Sun Sep 25, 2011 4:40 am

Quoting tdscanuck (Reply 8):
As I understand it, it's not the ground turn that's the problem, it's the really short flight cycle. An island hop in the Hawaiian islands is ~100-150 miles. That only gets you about half way to San Antonio from Houston.

  

Quoting ha763 (Reply 9):

To add to what Tom said, WN has the ability to send their aircraft on longer routes, even within Texas, which is not exactly possible with the Interisland market.

I would tend to agree. I always got the impression, that like a lot of issues regarding powerplants, it isn't a big deal on a limited basis but becomes an issue when you do it day in and day out.
Why do Aerospace Engineering students have to turn things in on time?
 
mrskyguy
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RE: Issues With The CFM-56 On Inter-Island Flights?

Mon Sep 26, 2011 12:11 am

Quoting tdscanuck (Reply 8):
As I understand it, it's not the ground turn that's the problem, it's the really short flight cycle. An island hop in the Hawaiian islands is ~100-150 miles. That only gets you about half way to San Antonio from Houston.

Sure, that makes sense.. but I'd argue that we're in the ballpark. The carrier with the closest operation to sample an inter-island route structure like AQ flew would be WN's Texas triangle routes. While they are ever-so-slightly longer, I would imagine that at least some similar issues would appear especially considering the longevity of those routes within the WN system utilizing CFM-56 power.

Thoughts?
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BMI727
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RE: Issues With The CFM-56 On Inter-Island Flights?

Mon Sep 26, 2011 1:38 am

Quoting mrskyguy (Reply 11):
I would imagine that at least some similar issues would appear especially considering the longevity of those routes within the WN system utilizing CFM-56 power.

By the time CFM powered 737s showed up Southwest had a lot of longer routes and planes rotated around more. During the time when they were flogging planes around Texas all they had were -200s.

Here is the WN route map from 1984 when the 737-300 first flew:
http://www.departedflights.com/WN010484.html
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ha763
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RE: Issues With The CFM-56 On Inter-Island Flights?

Mon Sep 26, 2011 3:38 am

Quoting mrskyguy (Reply 11):

It may seem similar, but it isn't. WN is not sending aircraft to fly ultra short flights 10-12 times a day. The shortest WN intra-Texas route is AUS-HOU at 148 miles and is only flown 5 daily round trips. The longest is HOU-ELP at 677 miles. The route with the most flights is DAL-HOU with 25 daily round trips. DAL-HOU is 239 miles.

The interisland routes with the most daily flights are HNL-OGG (20 daily round trips) and HNL-LIH (18 daily round trips). HNL-OGG is 101 miles and HNL-LIH is 102 miles. The interisland route most similar to AUS-HOU is HNL-KOA, which is 163 miles and has 16 daily round trips. The longest interisland route is is HNL-ITO at 216 miles with 14 daily round trips. This is HA's schedule and AQ was flying a similar schedule. The shortest interisland flight flown by AQ's 737s was ITO-KOA at 65 miles. HA used to fly MKK-LNY, which is 27 miles, with the DC-9s and 717s. HA also currently flies OGG-KOA, which is 84 miles.

Quoting BMI727 (Reply 10):
I would tend to agree. I always got the impression, that like a lot of issues regarding powerplants, it isn't a big deal on a limited basis but becomes an issue when you do it day in and day out.

There was a couple of times when AQ was short on -200s and had to use the -700 to cover for half the day before being sent on their mainland trip. After the 2nd or 3rd round trip, I've seen the mechanics get called out to the line for engine maintenance.
 
Charlienoble
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RE: Issues With The CFM-56 On Inter-Island Flights?

Mon Sep 26, 2011 10:52 am

Quoting ha763 (Reply 13):
After the 2nd or 3rd round trip, I've seen the mechanics get called out to the line for engine maintenance.

Does anybody know - what fails? What maintenance is required to get the CFM back in business?
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mrskyguy
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RE: Issues With The CFM-56 On Inter-Island Flights?

Mon Sep 26, 2011 7:22 pm

That's interesting. What could the mechanics offer in such circumstances if its a rest/cooling related issue?

What was it about the JT8Ds that made them so suitable for such cycle-intensive routes?
"The strength of the turbulence is directly proportional to the temperature of your coffee." -- Gunter's 2nd Law of Air
 
Okie
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RE: Issues With The CFM-56 On Inter-Island Flights?

Mon Sep 26, 2011 7:50 pm

Quoting mrskyguy (Reply 15):
What was it about the JT8Ds that made them so suitable for such cycle-intensive routes


I would go with less efficient meaning larger clearances and still be in spec.

Okie
 
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HAWK21M
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RE: Issues With The CFM-56 On Inter-Island Flights?

Wed Sep 28, 2011 8:57 am

Though not directly related....whats the normal oil consumption rate on a typical CFM56-7 series engine?.
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MarkC
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RE: Issues With The CFM-56 On Inter-Island Flights?

Wed Sep 28, 2011 11:18 pm

I've seen a CFM56-5B getting torn down from a Carribean operator, and, it was unbelievably corroded without a huge amount of cycles and time. Not sure if it was the environment, short trips, or maintenance practices. Sample size of one I know, but typically fleet engines are similar to each other.
 
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HAWK21M
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RE: Issues With The CFM-56 On Inter-Island Flights?

Tue Oct 04, 2011 9:05 am

Quoting MarkC (Reply 18):
maintenance practices

Very Important to the Airworthiness of an Aircraft.....Procedures are in place,but they need to be followed.
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